Energy-saving sand core assembly quality detection method and system based on multi-sensor data

Abstract

The application discloses an energy-saving pump sand core assembly quality detection method and system based on multi-sensor data, and relates to the technical field of energy-saving pump manufacturing. The method comprises the following steps: obtaining a core head image of a to-be-detected sand core, determining a force application contact position and a stress concentration monitoring area; controlling a force application assembly to press the force application contact position at a first pressure value, collecting an initial micro-vibration sequence of the stress concentration monitoring area, and calculating a fluctuation energy value; calculating a fluctuation energy threshold value and an open crack sensitivity index; controlling the force application assembly to increase the loading force at a constant rate starting from the first pressure value, calculating the deformation recovery rate of the unloading hysteresis interval and the average change rate of the unloading hysteresis displacement; and when the deformation recovery rate is lower than a dynamic recovery rate threshold value or the average change rate of the unloading hysteresis displacement exceeds a dynamic change rate threshold value, it is determined that there is internal micro-crack propagation. The application realizes quantitative detection of the open crack on the surface of the sand core and the internal micro-crack propagation, and improves the accuracy and reliability of the assembly quality detection.

Description

Technical Field

[0001] This invention relates to the field of energy-saving pump manufacturing technology, and specifically to a method and system for detecting the assembly quality of energy-saving pump sand cores based on multi-sensor data. Background Technology

[0002] In the casting production of energy-saving pumps, sand cores are key components forming the complex internal cavity of the pump body, and their quality directly affects the casting yield. During the core assembly process, multiple sand cores are sequentially placed and work together. The core head of the lower sand core must withstand the weight of the upper sand core and the assembly impact force. If the sand core strength is insufficient, the core head is prone to breakage, leading to core scrap or batch casting defects. Therefore, effectively verifying the dynamic pressure-bearing capacity of the sand core during the core assembly process is a crucial step in ensuring casting quality.

[0003] In existing technologies, the inspection of sand core assembly quality mainly relies on manual experience. Operators typically apply an estimated force to the core tip by hand or using simple lever tools, subjectively sensing whether the sand core will break or whether there are hidden cracks. This existing inspection method has several shortcomings. First, the magnitude of the applied force lacks quantitative standards, leading to significant differences in force applied by different operators, resulting in inconsistent inspection results and making it difficult to establish a basis for quality judgment. Second, traditional methods can only detect macroscopic fractures of the sand core under static loads, failing to identify open cracks and the propagation of internal microcracks during sustained loading or dynamic loading. Hidden defects can easily induce sudden fractures during core assembly, causing quality accidents. Third, manual inspection lacks data recording and traceability capabilities, making it impossible to analyze and provide early warnings of fluctuations in sand core quality, hindering early detection and preventative control of quality problems. Summary of the Invention

[0004] This invention addresses the technical problems in existing technologies where sand core assembly quality inspection relies on subjective human experience, lacks quantitative standards, and cannot identify the propagation of hidden cracks and internal microcracks. It provides an energy-saving pump sand core assembly quality inspection method and system based on multi-sensor data.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: In a first aspect, the present invention provides a method for detecting the assembly quality of energy-saving pump sand cores based on multi-sensor data, including: The image acquisition component is used to acquire images of the core head of the sand core to be tested, and the force contact location and stress concentration monitoring area are determined. The force application component is controlled to press against the force application contact position with a first pressure value, and the initial micro-vibration sequence of the stress concentration monitoring area is collected by the displacement sensing component to calculate the wave energy value. Based on the contour curvature radius of the stress concentration monitoring area, the fluctuation energy threshold is calculated and the opening crack sensitivity index is obtained. The force application component is controlled to increase the loading force at a constant rate starting from the first pressure value, and the deformation displacement sequence at the force application contact position is collected. The deformation recovery rate and the average change rate of the unloading hysteresis interval in the deformation displacement sequence are calculated. When the deformation recovery rate is lower than the dynamic recovery rate threshold or the average change rate of the unloading hysteresis displacement exceeds the dynamic change rate threshold, it is determined that the sand core to be tested has internal microcrack propagation.

[0006] Secondly, the present invention provides an energy-saving pump sand core assembly quality inspection system based on multi-sensor data, comprising: The image acquisition module is used to acquire images of the core head of the sand core to be tested through the image acquisition component, and to determine the force contact position and stress concentration monitoring area; The preloading module is used to control the force application component to press against the force application contact position with a first pressure value, and to collect the initial micro-vibration sequence of the stress concentration monitoring area through the displacement sensing component and calculate the wave energy value. The sensitivity index acquisition module is used to calculate the fluctuation energy threshold and acquire the opening crack sensitivity index based on the contour curvature radius of the stress concentration monitoring area. The loading and deformation analysis module is used to control the force application component to increase the loading force at a constant rate starting from the first pressure value, and to collect the deformation displacement sequence at the force application contact position, and to calculate the deformation recovery rate and the average change rate of the unloading hysteresis interval in the deformation displacement sequence. The crack detection module is used to determine that there is internal microcrack propagation in the sand core to be tested when the deformation recovery rate is lower than the dynamic recovery rate threshold or the average change rate of the unloading hysteresis displacement exceeds the dynamic change rate threshold.

[0007] The beneficial effects of this invention are: Compared to existing technologies, this invention firstly achieves precise detection location by automatically calibrating the force application contact position and stress concentration monitoring area through an image acquisition component, overcoming the shortcomings of arbitrary positioning in manual operation. Secondly, by applying pressure with a first pressure value through the force application component, the initial micro-vibration sequence is collected to calculate the wave energy value. Combined with the contour curvature radius, the wave energy threshold is calculated, which can effectively identify open cracks and achieve early detection of microcracks. Thirdly, based on the open crack sensitivity index, the force application component is controlled to increase the loading force, and the deformation displacement sequence is collected to calculate the deformation recovery rate and the average change rate of displacement after unloading. The propagation of internal microcracks is determined by dynamic threshold comparison, achieving quantitative detection of latent defects. Finally, this invention constructs a complete detection chain from surface crack detection to internal microcrack propagation determination, providing a quantifiable and traceable intelligent detection solution for sand core assembly quality, reducing the risk of batch casting scrap due to latent defects in sand cores. Attached Figure Description

[0008] Figure 1 A flowchart illustrating the energy-saving pump sand core assembly quality inspection method based on multi-sensor data provided by the present invention; Figure 2 A schematic diagram of the structure of the energy-saving pump sand core assembly quality inspection system based on multi-sensor data provided by the present invention.

[0009] In the attached diagram, the components represented by each number are as follows: Image acquisition module 11, preloading module 12, sensitivity index acquisition module 13, loading and deformation analysis module 14, crack judgment module 15. Detailed Implementation

[0010] Example 1, as Figure 1 As shown, this embodiment of the invention provides a method for inspecting the assembly quality of energy-saving pump sand cores based on multi-sensor data, including: S10: Obtain the core head image of the sand core to be tested through the image acquisition component, and determine the force contact position and stress concentration monitoring area; First, an image of the core head of the sand core to be inspected is acquired using an image acquisition component. This component is a vision imaging unit consisting of an industrial camera, lens, and light source. It is used to acquire surface images of the core head area. For example, a 5-megapixel CMOS industrial camera paired with a ring LED light source can be used to ensure clear imaging of the core head contour and surface features. The core head image acquired by the image acquisition component is a two-dimensional grayscale image containing the geometric contour and surface texture of the core head area. This image is used to characterize the shape features, dimensional parameters, and contour variation patterns at the interface between the core head and the core body.

[0011] Furthermore, based on the contour feature points marked in the core head image, the force application contact location and stress concentration monitoring area are determined. Contour feature points refer to key pixels extracted from the core head image that reflect the core's geometry, including abrupt changes in grayscale gradient at the core head and core body interface, and points of contour curvature change. The force application contact location refers to the point where the force-applying component directly contacts the core during subsequent loading. This location must avoid weak areas of the core head to ensure effective transmission of the loading force to the core structure. The stress concentration monitoring area refers to the part of the core most prone to stress concentration during loading, typically located in the transition area at the core head and core body interface. Geometric abrupt changes in this area lead to uneven stress distribution, making it a high-risk location for crack initiation and propagation.

[0012] Specifically, due to the complex structure of the core head area, and the differences in core head shape, size, and transition area between different cores, improper selection of the force application location may lead to test results that fail to accurately reflect the actual pressure-bearing capacity of the core, or even misjudgment due to the force application location deviating from the stress concentration area. This step, through image acquisition and contour feature point calibration, can automatically identify the unique geometric features of each core to be tested, accurately locate the force application contact point and stress concentration monitoring area, and provide standardized application points and monitoring points for subsequent loading tests, thereby ensuring the consistency and reliability of the test results.

[0013] Specifically, the image acquisition component acquires images of the core head of the sand core to be tested, and determines the force contact location and stress concentration monitoring area, including: The image of the core head of the sand core to be tested is acquired using an image acquisition component; Extract the gray-level gradient abrupt change points at the junction of the core head and core body in the core head image, and mark the continuous area where the gray-level gradient abrupt change points are located as the stress concentration monitoring area; Identify the location with the minimum radius of curvature in the stress concentration monitoring area, and expand outward from the location with the minimum radius of curvature to form a circular area with a preset radius. Mark the circular area as the micro-vibration acquisition area. Using the stress concentration monitoring area as a reference, the core is moved a specified offset distance towards the end along the core extension direction of the core image, and the area covered after the movement is marked as the force contact position.

[0014] First, the image of the core head of the sand core to be inspected is acquired using an image acquisition component. The industrial camera and light source are then activated to acquire surface images of the core head area under standardized lighting conditions, ensuring clear imaging of the core head outline, core body boundary line, and surface texture, providing fundamental data for subsequent image processing.

[0015] Secondly, abrupt changes in grayscale gradients at the junction of the core head and core body are extracted from the core head image. The continuous regions containing these abrupt changes are designated as stress concentration monitoring areas. The junction of the core head and core body is a transitional region where the geometry of the sand core undergoes abrupt changes, making this area prone to stress concentration under stress. Abrupt changes in grayscale gradients refer to locations in the image where the grayscale values ​​of adjacent pixels change drastically, reflecting the contour edge of the junction between the core head and core body. By extracting all abrupt changes in grayscale gradients and clustering spatially adjacent abrupt changes into continuous regions, these continuous regions become stress concentration monitoring areas, representing the most vulnerable locations in the sand core during stress.

[0016] Specifically, the gray-level gradient abrupt change points at the junction of the core head and core body in the core head image are extracted, and the continuous region where the gray-level gradient abrupt change points are located is marked as the stress concentration monitoring region, including: The chip head image is converted to grayscale to obtain a grayscale image; Traverse the grayscale difference between each pixel and its neighboring pixels in the grayscale image, and mark the pixels whose grayscale difference exceeds the grayscale change threshold as the grayscale gradient abrupt change points. Among the gray-level gradient abrupt change points, spatially adjacent abrupt change points are clustered into a continuous abrupt change point set. During clustering, eight-neighbor adjacency is used as the criterion, and all interconnected abrupt change points are grouped into the same continuous abrupt change point set. Extract the abrupt change points in the continuous abrupt change point set whose radius of curvature is less than the radius of curvature threshold as stress concentration feature points, wherein the radius of curvature threshold is determined based on the average and standard deviation of the radius of curvature of all abrupt change points in the continuous abrupt change point set; Centered on the stress concentration feature point, search forward and backward along the extension direction of the continuous set of abrupt change points, and mark the continuous area covered by all abrupt change points within the search range as the stress concentration monitoring area.

[0017] First, the chip image is converted to grayscale to obtain a grayscale image. Grayscale conversion is the process of converting the red, green, and blue color components of each pixel in the original color image into a single brightness value using a weighted average formula. A commonly used conversion formula is: grayscale value = 0.299 multiplied by the red component + 0.587 multiplied by the green component + 0.114 multiplied by the blue component. The original chip image is a color image; grayscale conversion converts it into a single-channel grayscale image, simplifying the computational complexity of subsequent image processing while preserving the brightness information reflecting contour changes in the image.

[0018] Secondly, the grayscale difference between each pixel and its neighboring pixels in the grayscale image is traversed, and pixels whose grayscale difference exceeds the grayscale change threshold are marked as grayscale gradient abrupt change points. The grayscale difference reflects the degree of brightness change between adjacent pixels. At the junction of the core head and the core body, due to the abrupt change in geometric structure, the grayscale value will change drastically.

[0019] The grayscale change threshold represents the critical value for distinguishing grayscale differences between edge pixels and background pixels. This threshold is preset based on the overall contrast and noise level of the image. Specifically, it is determined as follows: Based on historical core images of multiple calibrated stress concentration monitoring areas, the grayscale difference between the pixel at the junction of the core head and core body and the adjacent background pixel in each historical image is calculated. All grayscale differences are sorted from smallest to largest to form a grayscale difference distribution. The grayscale difference value corresponding to the 95th percentile of the grayscale difference distribution is determined as the grayscale change threshold, which can be set to, for example, 30 to 50. Pixels with grayscale differences exceeding this threshold are marked as grayscale gradient abrupt change points. These grayscale gradient abrupt change points represent candidate pixels for the contour edge at the junction of the core head and core body. All grayscale gradient abrupt change points initially constitute the edge point set at the junction of the core head and core body.

[0020] Furthermore, spatially adjacent abrupt change points in the gray-level gradient abrupt change are clustered into a continuous abrupt change point set. Clustering is based on eight-neighbor adjacency, grouping all interconnected abrupt change points into the same continuous abrupt change point set. Eight-neighbor adjacency means that, with the current pixel as the center, adjacent pixels in the eight directions (up, down, left, right, upper left, upper right, lower left, and lower right) are considered adjacent points. Specifically, for any marked gray-level gradient abrupt change point, its adjacent pixels in the eight directions are checked. If adjacent pixels are also marked as abrupt change points, they are considered spatially connected. All gray-level gradient abrupt change points are iterated through, grouping interconnected gray-level gradient abrupt change points into the same set, until all gray-level gradient abrupt change points are assigned to their corresponding continuous abrupt change point sets.

[0021] Specifically, the reason for choosing eight neighboring regions is that the stress concentration area at the junction of the core head and core body usually presents as a continuous curve or arc, and the distribution of gray-level abrupt change points in this area may also have connectivity in the diagonal direction. The adjacency of eight neighboring regions can more completely capture the continuous contour at the junction, avoiding the same stress concentration area being incorrectly segmented into multiple fragmented regions due to the lack of connectivity in the diagonal direction, thus ensuring that the subsequent extraction of stress concentration feature points is based on the complete geometric shape.

[0022] Through the above clustering operation, each set of continuous mutation points corresponds to a continuous edge at the junction of the core head and the core body. At the same time, isolated noise points can be eliminated, and edge segments with continuous geometric meaning can be retained.

[0023] Furthermore, abrupt changes with radii of curvature smaller than a threshold value are extracted from the set of continuous abrupt change points as stress concentration feature points. The radius of curvature threshold is determined based on the average and standard deviation of the radii of curvature of all abrupt change points in the set. The radius of curvature reflects the curvature of the edge curve; a smaller radius of curvature indicates a more severe geometric abrupt change and a higher degree of stress concentration. Specifically, the radius of curvature of all abrupt change points in the set is first calculated, and then the average and standard deviation of the radii of curvature are calculated. The radius of curvature threshold is set to the average value minus one standard deviation, thus selecting points with radii of curvature significantly smaller than the average level as stress concentration feature points. This method automatically identifies the most severe localized stress concentration areas at the interface, ensuring that detection focuses on high-risk areas for crack initiation.

[0024] Secondly, using the identified stress concentration feature point as the center, a search is performed forward and backward along the extension direction of the continuous set of abrupt change points. The continuous area covered by all abrupt change points within the search range is designated as the stress concentration monitoring area. Specifically, the extension direction of the continuous set of abrupt change points refers to the tangent direction of the edge at the junction of the core head and core body, which can be determined based on the direction of the line connecting adjacent abrupt change points at the stress concentration feature point. Using each stress concentration feature point as the center, a search is performed forward and backward along the edge extension direction. The endpoint of the search range is determined by the natural boundary of the continuous set of abrupt change points; that is, when there are no other abrupt change points within the eight-neighborhood of a certain abrupt change point, that abrupt change point is the endpoint of the continuous set of abrupt change points, and the search terminates there. For example, the search stops when the search step size reaches a preset upper limit or when an endpoint is encountered. The preset step size can be set to 5 to 10 pixels. The continuous area covered by all abrupt change points within the search range is designated as the stress concentration monitoring area. This stress concentration monitoring area encompasses the stress concentration feature point and its surrounding complete edge abrupt change area, comprehensively reflecting the geometric abrupt change characteristics at the junction, and providing accurate monitoring locations for subsequent micro-vibration acquisition and deformation analysis.

[0025] Furthermore, using the location of the stress concentration feature point as the center of the micro-vibration acquisition area, a circular area with a preset radius is formed and marked as the micro-vibration acquisition area. Specifically, the stress concentration feature point is the location with the smallest radius of curvature determined after screening by the radius of curvature threshold. It represents the sensitive point with the most severe geometric change and the highest degree of stress concentration within the stress concentration monitoring area, and is the key location where microcracks first initiate. The preset radius can be set according to the sand core size and detection accuracy requirements, for example, it can be set to 2 mm to 5 mm. The micro-vibration acquisition area is used as the probe alignment position for the displacement sensing component when acquiring the initial micro-vibration sequence in the subsequent pre-loading stage. This area is located at the most sensitive part of stress concentration and can capture the abnormal vibration response caused by the presence of microcracks to the greatest extent.

[0026] Finally, using the stress concentration monitoring area as a reference, the core is moved a specified offset distance towards the end along the core extension direction of the core image, and the area covered after the movement is marked as the force contact position. Here, the core extension direction refers to the axial direction from the core-body junction to the end of the core.

[0027] The force application contact point refers to the area where the force application component directly contacts the sand core during loading. It must avoid stress concentration monitoring areas to prevent the force application point from directly acting on crack-sensitive areas, thus avoiding human-caused damage during the testing process. Simultaneously, it must ensure that the force application point is located in the load-bearing area of ​​the core head structure, allowing the loaded force to be effectively transferred to the core body. Using the stress concentration monitoring area as a reference, the force application point is moved a specified offset distance along the core head extension direction of the core head image, and the area covered after the movement is marked as the force application contact point. This ensures that the force application point avoids the most sensitive crack initiation areas due to stress concentration, applying the loaded force to the load-bearing parts of the core head structure. This ensures that, while guaranteeing testing safety, the loaded force can be effectively transferred along the core head axis to the core body junction, accurately reflecting the stress state of the sand core during assembly.

[0028] The calculation steps for the specified offset distance include: Obtain the extension length and root width of the core tip in the core tip image; Images of the core heads of multiple historical sand core samples were collected, and the corresponding stress concentration monitoring area and force contact position were marked for each historical sand core sample. Record the extension length, core root width, and actual offset distance from the stress concentration monitoring area to the force contact point for each historical sand core sample; Using the extension length and core root width of the multiple historical sand core samples as input features, and the corresponding actual offset distance as the supervision signal, the first coefficient and the second coefficient are obtained by multiple linear regression fitting. The specified offset distance is obtained by adding the product of the extension length of the sand core to be tested and the first coefficient, and the product of the root width of the sand core to be tested and the second coefficient.

[0029] First, obtain the extension length and root width of the core head from the core head image. The extension length refers to the distance along the core head axis from the junction of the core head and the core body to the end of the core head, reflecting the overall length of the core head; the root width refers to the lateral dimension of the core head at the junction of the core head and the core body, reflecting the thickness of the core head root. The extension length and root width together determine the structural characteristics of the sand core head and are important factors affecting the selection of the force contact position.

[0030] Secondly, images of the core heads of multiple historical sand core samples were acquired, and the corresponding stress concentration monitoring area and force contact position were marked for each historical sand core sample. Historical sand core samples refer to sand cores whose force contact positions have been confirmed to be reasonable through manual or other means. Their stress concentration monitoring areas were automatically marked using the aforementioned image processing method, while the force contact positions were marked by experienced operators based on actual testing experience, serving as the benchmark data for subsequent fitting.

[0031] Record the extension length, core root width, and actual offset distance from the stress concentration monitoring area to the force application contact position for each historical sand core sample. For each historical sand core sample, use its extension length and core root width as input features, and the straight-line distance between the manually calibrated force application contact position and the automatically calibrated stress concentration monitoring area as the actual offset distance to form a set of training samples.

[0032] Furthermore, using the extension length and core root width of multiple historical sand core samples as input features, and the corresponding actual offset distance as the supervision signal, the first and second coefficients are obtained through multiple linear regression fitting. The form of the multiple linear regression model is: the actual offset distance equals the first coefficient multiplied by the extension length, plus the second coefficient multiplied by the core root width, plus the bias term. By minimizing the fitting error, the optimal values ​​of the first and second coefficients are obtained, enabling the model to predict a reasonable offset distance based on the geometric parameters of the core.

[0033] Specifically, the product of the extension length of the sand core to be tested and a first coefficient, and the product of the root width of the sand core to be tested and a second coefficient, are added to obtain the specified offset distance. This offset distance is used in subsequent steps to move the core head towards the end along the extension direction in a distance based on the stress concentration monitoring area, and the area covered after the movement is marked as the force application contact position. Through the above-mentioned offset distance calculation method based on historical sample fitting, the determination of the force application contact position can fully take into account the differences in geometric characteristics of different sand cores, and achieve adaptive positioning of the force application position.

[0034] In summary, the above steps have enabled precise positioning of the force contact location and stress concentration monitoring area, providing standardized application points and monitoring points for subsequent loading tests.

[0035] S20: Control the force application component to press against the force application contact position with a first pressure value, and collect the initial micro-vibration sequence of the stress concentration monitoring area through the displacement sensing component to calculate the wave energy value; Secondly, the force-applying component is controlled to apply a first pressure value to the force-applying contact position. The force-applying component is a precision loading unit consisting of a servo motor, a force sensor, and a pressure head, used to apply precise and controllable static or dynamic loads to the sand core under control commands. The first pressure value is a preset pressure value in the pre-loading stage, representing the initial load used to detect whether there are open cracks on the surface of the sand core before formal loading. This pressure value needs to be large enough to excite a vibration response at the micro-cracks, but not too large to avoid damaging the crack-free sand core.

[0036] The steps for determining the first pressure value include: Multiple standard sand core samples of the same type as the sand core to be tested and confirmed to be free of cracks were obtained. The stress concentration monitoring area and the force contact position were marked for each standard sand core sample. The force application component is controlled to increase the loading force at a constant rate. During the loading process, the micro-vibration sequence of the stress concentration monitoring area is synchronously collected by the displacement sensing component. The constant rate is determined based on the extension length of the sand core to be tested. The loading force value at which the displacement amplitude first exceeds the amplitude threshold in the micro-vibration sequence corresponding to each loading force value is recorded as the critical pressure value; The arithmetic mean of the critical pressure values ​​of each standard sand core sample is taken, and the product of the arithmetic mean and the safety factor is taken as the first pressure value. The safety factor is determined based on the fluctuation range of the critical pressure values ​​of the standard sand core samples and is a positive real number less than 1.

[0037] First, multiple standard sand core samples of the same type as the sand core to be tested, confirmed to be crack-free, are obtained. The corresponding stress concentration monitoring area and force contact position are then calibrated for each standard sand core sample. Specifically, the standard sand core sample refers to a qualified sand core confirmed to be free of any cracks through non-destructive testing or destructive testing, serving as the reference object for calibrating the first pressure value. For each standard sand core sample, its stress concentration monitoring area and force contact position are calibrated according to the aforementioned image processing method to ensure the accuracy of the loading and monitoring positions.

[0038] Secondly, the force application component is controlled to increase the loading force at a constant rate, and during the loading process, the micro-vibration sequence of the stress concentration monitoring area is synchronously acquired through the displacement sensing component. The displacement sensing component is a measurement unit composed of a high-precision laser displacement sensor or eddy current displacement sensor and its signal conditioning circuit, used to acquire micron-level displacement changes at specific locations on the sand core surface in real time. For example, a laser displacement sensor with a range of ±1 mm and a resolution of 0.1 μm can be selected. The micro-vibration sequence of the stress concentration monitoring area is acquired, which reflects the dynamic response of the sand core due to changes in its microstructure during loading. By analyzing the variation law of displacement amplitude, the critical state of microcrack initiation can be identified.

[0039] The constant rate is determined based on the elongation length of the sand core under test. The specific calculation formula is: constant rate equals elongation length divided by the rate coefficient. The rate coefficient is obtained by averaging the optimal loading rates of multiple historical sand core samples under crack-free conditions. The optimal loading rate is the maximum loading rate at which each historical sand core sample does not induce additional vibration noise during loading. For example, when the elongation length is 100 mm and the rate coefficient is 200, the constant rate can be set to 0.5 kN / s.

[0040] Specifically, the critical pressure value is recorded as the first time the displacement amplitude in the micro-vibration sequence corresponding to each loading force value exceeds the amplitude threshold. During the loading process, when the loading force is small, the sand core is in the elastic deformation stage, and the displacement amplitude is stable and small; when the loading force increases to a certain extent, if there are defects inside the sand core or microcracks begin to form in the stress concentration area, the displacement amplitude will change abruptly.

[0041] The amplitude threshold is determined based on the maximum displacement amplitude of multiple standard sand core samples of the same type as the sand core to be tested and confirmed to be crack-free under various loading force values. Specifically, for each loading force value, the displacement amplitude of each standard sand core sample under that loading force value is statistically analyzed, and the maximum value is taken as the amplitude threshold corresponding to that loading force value, forming a one-to-one correspondence between the amplitude threshold and the loading force value. The moment when the displacement amplitude first exceeds the amplitude threshold under the corresponding loading force value, the loading force value is the critical pressure value, representing the critical load at which the sand core begins to generate microcracks or significant nonlinear responses during the loading process.

[0042] Furthermore, the arithmetic mean of the critical pressure values ​​of each standard sand core sample is taken. The ratio of the maximum to the minimum critical pressure value of each standard sand core sample is calculated as the fluctuation coefficient. The reciprocal of the fluctuation coefficient is used as the safety factor. The product of the arithmetic mean and the safety factor is used as the first pressure value. Since the standard sand core samples are confirmed to be crack-free, their critical pressure values ​​reflect the maximum safe load that the sand core can withstand in a crack-free state. Taking the arithmetic mean of multiple samples can eliminate individual differences. The safety factor is determined based on the fluctuation range of the critical pressure value. The larger the fluctuation coefficient, the greater the difference between samples, and the smaller the safety factor, thus ensuring that the first pressure value is lower than the critical pressure value of all standard sand core samples. For example, when the ratio of the maximum to the minimum value is 1.2, the fluctuation coefficient is 1.2, and the safety factor is approximately 0.83; when the ratio is 1.5, the safety factor is approximately 0.67.

[0043] The above calibration method ensures that the first pressure value can effectively stimulate the vibration response at the microcracks without damaging the crack-free sand core.

[0044] Simultaneously, during the maintenance of the first pressure value, the initial micro-vibration sequence of the stress concentration monitoring area is acquired through the displacement sensing component, and the fluctuation energy value is calculated. The displacement sensing component is a measurement unit composed of a high-precision displacement sensor and its signal conditioning circuit, used to acquire micron-level displacement changes at specific locations on the sand core surface in real time. The initial micro-vibration sequence refers to the discrete sampling point sequence of the minute vibration displacements generated in the stress concentration monitoring area due to the presence of microcracks over time after the force-applying component presses against the contact position with the first pressure value. If there is an open crack on the sand core surface, under constant pressure, the microstructures on both sides of the crack will undergo relative slippage or vibration, generating vibration signals with specific frequencies and amplitudes; if there is no crack, the vibration signal amplitude is smaller and relatively stable.

[0045] The wave energy value is a quantitative index obtained by normalizing the sum of the squares of the amplitudes of each displacement sampling point in the initial micro-vibration sequence. It is used to characterize the overall intensity of the vibration signal. The larger the wave energy value, the higher the probability that the sand core has an open crack. Through micro-vibration detection in this pre-loading stage, sand cores with surface open cracks can be identified before formal loading, avoiding core breakage due to crack propagation during subsequent loading, and providing a basis for decision-making in subsequent detection processes.

[0046] Specifically, the force-applying component is controlled to press against the force-applying contact position with a first pressure value, and the initial micro-vibration sequence of the stress concentration monitoring area is collected by the displacement sensing component to calculate the wave energy value, including: Control the force-applying component to move unloaded to directly above the force-applying contact position, and control the force-applying component to move downward until it contacts the force-applying contact position; The force sensor feedback value is read at the moment of contact. When the force sensor feedback value reaches the first pressure value, the downward movement stops. The moment of contact is determined by the instantaneous state of the force sensor feedback value changing from zero to non-zero. The moment when the force sensor feedback value first exceeds zero is taken as the moment of contact. The force application component is maintained at the first pressure value state. The probe of the displacement sensing component is aligned with the micro-vibration acquisition area. During the maintenance period, the displacement change of the micro-vibration acquisition area is continuously acquired at a fixed sampling frequency to obtain an initial micro-vibration sequence composed of multiple displacement sampling points. By iterating through each displacement sampling point in the initial micro-vibration sequence, the square value of the displacement amplitude at each displacement sampling point is calculated. The sum of all the square values ​​is then divided by the total number of displacement sampling points to obtain the wave energy value.

[0047] First, the force-applying component is moved unloaded to directly above the force-applying contact position. Then, it is moved downwards until it contacts the contact position. Unloaded movement refers to the force-applying component being driven by a servo motor to move the pressure head to the preset position directly above the contact position without any applied load. Subsequently, the pressure head is slowly moved downwards, gradually approaching and contacting the sand core surface. During this process, a force sensor continuously monitors changes in the contact force.

[0048] The force sensor feedback value is read at the moment of contact. The downward movement stops when the force sensor feedback value reaches the first pressure value. The moment of contact is determined by the instantaneous change in the force sensor feedback value from zero to non-zero; the moment the force sensor feedback value first exceeds zero is taken as the contact moment. When the pressure head just contacts the sand core surface, the force sensor feedback value undergoes a slight change from zero; this moment is the contact moment. From the contact moment, the pressure head continues to move downward a short distance, gradually increasing the applied pressure until the force sensor feedback value reaches the preset first pressure value, at which point the downward movement stops and this pressure value is maintained.

[0049] Specifically, the force application component is maintained at the first pressure value state, and the probe of the displacement sensing component is aligned with the micro-vibration acquisition area. During the maintenance period, the displacement change of the micro-vibration acquisition area is continuously acquired at a fixed sampling frequency to obtain an initial micro-vibration sequence composed of multiple displacement sampling points.

[0050] The displacement sensing component can employ a magnetic displacement sensor, which detects minute distance changes between the probe and the sand core surface through electromagnetic induction. It features non-contact operation and high sensitivity, making it suitable for precise measurements of micron-level vibrations. The duration of the measurement can be set according to the stability requirements of the vibration signal, for example, from 2 to 5 seconds, ensuring that a sufficient number of vibration cycles are collected to reflect the micro-vibration characteristics.

[0051] The method for determining the fixed sampling frequency is as follows: Multiple standard sand core samples of the same type as the sand core to be tested, confirmed to be crack-free, are collected. During the microcrack initiation process, micro-vibration sequences are acquired using a displacement sensing component. Spectral analysis is performed on the micro-vibration sequences to extract the main frequency components of the micro-vibration signal. The highest frequency of these main components is then set as the fixed sampling frequency. According to the Nyquist sampling theorem, the sampling frequency must be at least twice the highest frequency of the signal to avoid spectral aliasing and fully preserve the waveform characteristics of the micro-vibration signal. For example, if spectral analysis shows that the highest main frequency component of the micro-vibration signal is 500 Hz, then the fixed sampling frequency is set to 1000 Hz.

[0052] Specifically, the probe of the displacement sensing component remains aligned with the micro-vibration acquisition area during the maintenance period, continuously recording the minute displacement fluctuations in that area under constant pressure, forming an initial micro-vibration sequence composed of multiple displacement sampling points. This initial micro-vibration sequence contains vibration response information generated by the presence of the open crack, providing basic data for subsequent calculation of the fluctuation energy value.

[0053] Finally, by iterating through all displacement sampling points in the initial micro-vibration sequence, the square of the displacement amplitude at each sampling point is calculated. The sum of all squared values ​​is then divided by the total number of sampling points to obtain the wave energy value. The wave energy value is calculated as follows: the wave energy value equals the sum of the squares of the displacement amplitudes at each sampling point divided by the total number of sampling points. This wave energy value reflects the overall energy level of the initial micro-vibration sequence. A higher wave energy value indicates more intense micro-vibration and a higher probability of open-end cracks in the sand core. This quantitative index transforms minute vibrations, which are difficult to judge subjectively, into comparable numerical values, providing an objective basis for subsequent crack determination.

[0054] S30: Based on the contour curvature radius of the stress concentration monitoring area, calculate the fluctuation energy threshold and obtain the opening crack sensitivity index; Furthermore, based on the radius of curvature of the stress concentration monitoring area, a fluctuation energy threshold is calculated and compared with the fluctuation energy value obtained from the previous calculation to obtain the open crack sensitivity index. Specifically, the radius of curvature reflects the severity of geometric abrupt changes in the stress concentration monitoring area. The smaller the radius of curvature, the sharper the geometric structure of the area, the higher the stress concentration, and the easier it is to generate microcracks under the same load conditions, thus resulting in higher sensitivity to micro-vibration response. The fluctuation energy threshold is a critical value dynamically calculated based on the geometric characteristics of the stress concentration monitoring area, used to determine whether the currently acquired fluctuation energy value reaches the criteria for an open crack.

[0055] The open crack sensitivity index is the ratio of the fluctuation energy value to the fluctuation energy threshold. When the index is greater than 1, it indicates that the fluctuation energy value exceeds the threshold and the sand core is likely to have an open crack. When the index is less than or equal to 1, it indicates that the fluctuation energy value is within the normal range and there is no obvious open crack on the surface of the sand core.

[0056] Specifically, this step stems from the fact that the geometric characteristics of stress concentration monitoring areas differ among different sand cores. Using a uniform fluctuation energy threshold for crack detection could lead to misjudgments of sand cores with smaller radii of curvature due to higher stress concentration and greater sensitivity to vibration, or missed detections of sand cores with larger radii of curvature due to less sensitivity to vibration. By dynamically calculating the fluctuation energy threshold based on the contour curvature radius, the threshold can adapt to the geometric characteristics of the sand core, achieving accurate detection of open-crack patterns. The aim is to screen out sand cores with open-crack patterns before formal loading, preventing core fragmentation due to crack propagation during subsequent loading, and providing a basis for decision-making regarding subsequent internal microcrack propagation detection.

[0057] Specifically, based on the radius of curvature of the contour of the stress concentration monitoring region, the fluctuation energy threshold is calculated and the open crack sensitivity index is obtained, including: Extract the minimum contour radius of curvature from the stress concentration monitoring area; Obtain the reference fluctuation energy coefficient of a standard sand core sample of the same type as the sand core to be tested in a crack-free state. The reference fluctuation energy coefficient is obtained by averaging the product of the fluctuation energy values ​​of multiple standard sand core samples in a crack-free state and the corresponding minimum contour curvature radius. The ratio of the reference fluctuation energy coefficient to the minimum profile curvature radius is used as the fluctuation energy threshold. The ratio of the fluctuation energy value to the fluctuation energy threshold is used as the open crack sensitivity index.

[0058] First, the minimum profile radius of curvature is extracted from the stress concentration monitoring region. The stress concentration monitoring region contains multiple profile points, each corresponding to a radius of curvature. The location with the smallest radius of curvature exhibits the most dramatic geometric abrupt change and the highest degree of stress concentration, making it a sensitive site for the earliest initiation of microcracks. Therefore, the minimum profile radius of curvature is used as the geometric characteristic parameter for calculating the wave energy threshold.

[0059] Secondly, the baseline fluctuation energy coefficient of a standard sand core sample of the same type as the sand core to be tested is obtained under a crack-free state. The baseline fluctuation energy coefficient is a constant obtained by averaging the products of the fluctuation energy values ​​of multiple standard sand core samples under a crack-free state and their corresponding minimum profile curvature radii. Specifically, for each standard sand core sample, its stress concentration monitoring area is first calibrated and its minimum profile curvature radius is extracted according to the aforementioned method. Then, its fluctuation energy value under a crack-free state is collected according to the aforementioned method, and the product of the two is calculated. The arithmetic mean of the products of all standard sand core samples is taken to obtain the baseline fluctuation energy coefficient. This baseline fluctuation energy coefficient is used to reflect the inherent level of the fluctuation energy value of the crack-free sand core under specific geometric characteristics.

[0060] Furthermore, the ratio of the reference fluctuation energy coefficient to the minimum profile radius of curvature is used as the fluctuation energy threshold. Since the product of the fluctuation energy value and the minimum profile radius of curvature remains essentially constant in the crack-free state, the fluctuation energy threshold for the sand core under test is equal to the reference fluctuation energy coefficient divided by its own minimum profile radius of curvature. This fluctuation energy threshold increases as the minimum profile radius of curvature decreases; that is, the more drastic the geometric change in a region, the higher the permissible fluctuation energy threshold, thus avoiding the misinterpretation of normal vibrations caused by stress concentration as crack signals.

[0061] Finally, the ratio of the fluctuation energy value to the fluctuation energy threshold is used as the open crack sensitivity index. When the open crack sensitivity index is greater than 1, it indicates that the fluctuation energy value of the sand core under test exceeds the threshold calculated based on its geometric characteristics, and the sand core is highly likely to have an open crack; when the open crack sensitivity index is less than or equal to 1, it indicates that the fluctuation energy value is within the normal range and there is no obvious open crack on the surface of the sand core.

[0062] In summary, by using the above-mentioned method for calculating the dynamic fluctuation energy threshold, the determination of open cracks can be adaptively adjusted to the geometric characteristics of the sand core, thereby improving the accuracy and reliability of the determination.

[0063] S40: Control the force application component to increase the loading force at a constant rate starting from the first pressure value, and collect the deformation displacement sequence at the force application contact position, and calculate the deformation recovery rate and the average change rate of the unloading hysteresis interval in the deformation displacement sequence. Furthermore, based on the aforementioned open-crack sensitivity index, the force application component is controlled to increase the loading force at a constant rate starting from the first pressure value. A deformation displacement sequence at the force application contact point is collected using a displacement sensing component. The deformation recovery rate and the average change rate of the unloading hysteresis interval in the deformation displacement sequence are calculated. The open-crack sensitivity index is used to determine whether to enter the loading stage: if the sensitivity index is greater than 1, it indicates that an open crack already exists in the sand core, and continued loading may cause the sand core to break; therefore, the detection is terminated and the core is deemed unqualified. If the sensitivity index is less than or equal to 1, it indicates that there are no obvious open cracks on the surface of the sand core, and the loading stage can be entered for internal micro-crack propagation detection.

[0064] Increasing the loading force at a constant rate means that the force-applying component linearly increases the pressure applied to the force-applying contact point at a set rate, ensuring a smooth loading process and fully stimulating the response of internal microcracks. This constant rate is determined based on the extension length of the sand core under test. During loading, the displacement sensing component continuously collects the deformation displacement at the force-applying contact point, recording the displacement values ​​corresponding to different loading force values ​​to form a loading deformation displacement sequence. When the loading force increases to a preset second pressure value, loading stops, and then the force-applying component is controlled to decrease the loading force at the same constant rate. During unloading, the deformation displacement at the force-applying contact point is collected to form an unloading deformation displacement sequence.

[0065] The unloading hysteresis interval refers to the range where the loaded deformation displacement differs from the unloading deformation displacement during the entire process of the loading force increasing from the first pressure value to the second pressure value and then unloading back to the first pressure value. The deformation recovery rate reflects the sand core's ability to recover deformation after unloading. It is calculated by the ratio of the endpoint displacement when the loading force is the first pressure value in the unloading deformation displacement sequence to the loading displacement corresponding to the same loading force value in the loading deformation displacement sequence. A higher deformation recovery rate indicates a stronger elastic recovery ability of the sand core and a lower degree of internal microcrack propagation. The average rate of change of unloading hysteresis displacement reflects the average slope of the hysteresis displacement as the loading force changes during unloading. A larger value indicates a more significant unloading hysteresis phenomenon and a more severe internal microcrack propagation.

[0066] Specifically, this step is based on the premise that the presence of microcracks inside the sand core alters its mechanical behavior, manifesting as deformation hysteresis during the loading-unloading process. By collecting a complete loading-unloading deformation displacement sequence and calculating the deformation recovery rate and the average change rate of the unloading hysteresis displacement, the extent of microcrack propagation inside the sand core can be quantitatively assessed, providing a quantitative basis for subsequent crack determination.

[0067] Specifically, the force-applying component is controlled to increase the loading force at a constant rate starting from the first pressure value, and the deformation displacement sequence at the force-applying contact position is collected. The deformation recovery rate and the average change rate of the unloading hysteresis interval in the deformation displacement sequence are calculated, including: If the sensitivity index for open cracks is greater than 1, the detection is terminated and it is determined that the sand core to be tested has open cracks. If the open crack sensitivity index is less than or equal to 1, then the force application component is controlled to increase the loading force at a constant rate starting from the first pressure value; During the loading process, the displacement sensing component continuously collects the loading deformation displacement at the force contact position to obtain a loading deformation displacement sequence corresponding to the loading force value. When the loading force value is increased to the second pressure value, the loading force is stopped. The second pressure value is the loading force value at which the displacement increment of adjacent sampling points in the loading deformation displacement sequence first falls below the linear reference displacement increment during the loading process. The linear reference displacement increment is obtained by multiplying the linear regression slope of the displacement increment and the loading force increment in the elastic deformation stage of the loading deformation displacement sequence by the current loading force increment. The elastic deformation stage is the range in which the loading force rises from the first pressure value to the critical pressure value. The ratio of the displacement increment to the loading force increment in the loading deformation displacement sequence fluctuates within a preset deviation range during the continuous loading interval. The force application component is controlled to reduce the loading force at the same constant rate. During the unloading process, the displacement sensing component continuously collects the unloading deformation displacement at the force application contact position to obtain the unloading deformation displacement sequence corresponding to the loading force value, until the loading force value is restored to the first pressure value. The difference between the loading deformation displacement and the unloading deformation displacement under the same loading force value is taken as the unloading hysteresis displacement. The unloading hysteresis displacements corresponding to each loading force value during the process of increasing the loading force value from the first pressure value to the second pressure value constitute the unloading hysteresis interval. The ratio of the endpoint displacement when the loading force value in the unloading deformation displacement sequence is the first pressure value to the loading displacement corresponding to the same loading force value in the loading deformation displacement sequence is taken as the deformation recovery rate. Calculate the average slope of the unloading hysteresis displacement as a function of the loading force within the unloading hysteresis interval, and use the average slope as the average rate of change of the unloading hysteresis displacement.

[0068] First, if the sensitivity index for open-cracks is greater than 1, the testing is terminated and the sand core under test is determined to have open-cracks. An open-crack sensitivity index greater than 1 indicates that the fluctuation energy value collected during the pre-loading stage has exceeded the threshold calculated based on geometric features, and an open-crack has already appeared on the surface of the sand core. Continued loading may lead to crack propagation or even sand core fragmentation. Therefore, the subsequent testing process is terminated, and the core is directly judged as unqualified.

[0069] Furthermore, if the sensitivity index for open-crack formation is less than or equal to 1, the force application component is controlled to increase the loading force at a constant rate starting from the first pressure value. Under this condition, no obvious open-crack formation is observed on the sand core surface, allowing the loading stage to proceed with the detection of internal microcrack propagation. The constant rate can be preset according to the sand core size to ensure a smooth loading process.

[0070] Specifically, during the loading process, the displacement sensing component continuously collects the loading deformation displacement at the force application contact position, obtaining a loading deformation displacement sequence corresponding to the loading force value. The probe of the displacement sensing component is aligned with the force application contact position to record the deformation displacement change as the loading force increases, forming a sequence of data in which the loading force value and the displacement value correspond one-to-one, which is the loading deformation displacement sequence.

[0071] The loading force is increased to a second pressure value, at which point the increase in loading force stops. The second pressure value is the loading force at which the displacement increment of adjacent sampling points in the loading deformation displacement sequence first falls below the linear reference displacement increment. The linear reference displacement increment is obtained by multiplying the slope of the linear regression between the displacement increment and the loading force increment in the elastic deformation stage of the loading deformation displacement sequence by the current loading force increment.

[0072] Specifically, the elastic deformation stage refers to the continuous loading interval where the ratio of the displacement increment to the loading force increment in the loading deformation displacement sequence remains stable within a preset deviation range, from the initial pressure value to the critical pressure value. This preset deviation range is determined by performing loading tests on multiple standard sand cores of the same type as the sand core to be tested and confirmed to be defect-free. The ratio of the displacement increment to the loading force increment in the elastic deformation stage is extracted, and the average value and standard deviation of this ratio sequence are calculated. The preset deviation range is then calculated by adding or subtracting 1.5 to 3 times the standard deviation from the average value. During the elastic deformation stage, the sand core is in a linear elastic deformation state, with a linear relationship between displacement and force, and the ratio of the displacement increment to the loading force increment remains stable.

[0073] When the applied force exceeds the elastic deformation stage, if internal microcracks exist in the sand core, the propagation of these microcracks will absorb some energy, leading to a decrease in the displacement increment. This causes the ratio of the displacement increment to the applied force increment to deviate from the preset deviation range. When the displacement increment first falls below the linear reference displacement increment calculated from the linear regression slope of the elastic deformation stage, it indicates that the sand core has begun to undergo nonlinear deformation. The corresponding applied force value is the second pressure value. This second pressure value marks the critical point where the sand core transitions from elastic deformation to elastoplastic deformation and serves as an important reference benchmark for subsequent unloading hysteresis analysis.

[0074] Furthermore, the force-applying components are controlled to reduce the loading force at the same constant rate. During the unloading process, the displacement sensing components continuously collect the unloading deformation displacement at the force-applying contact position to obtain the unloading deformation displacement sequence corresponding to the loading force value, until the loading force value recovers to the first pressure value. During the unloading process, due to the presence of internal microcracks, the deformation recovery of the sand core exhibits a lag, and the unloading deformation displacement sequence does not coincide with the loading deformation displacement sequence.

[0075] Furthermore, the difference between the loaded deformation displacement and the unloaded deformation displacement under the same loading force value is taken as the unloading hysteresis displacement. The unloading hysteresis displacements corresponding to each loading force value during the process of increasing the loading force value from the first pressure value to the second pressure value constitute the unloading hysteresis interval. This unloading hysteresis interval reflects the irreversible deformation of the sand core caused by the propagation of internal microcracks during the loading-unloading cycle.

[0076] The ratio of the endpoint displacement when the loading force value is the first pressure value in the unloading deformation displacement sequence to the loading displacement corresponding to the same loading force value in the loading deformation displacement sequence is used as the deformation recovery rate. This deformation recovery rate is used to reflect the ability of the sand core to recover deformation after unloading. The closer the ratio is to 1, the stronger the recovery ability and the lower the degree of internal microcrack propagation; the smaller the ratio, the larger the residual deformation and the more severe the internal microcrack propagation.

[0077] Finally, the average slope of the unloading hysteresis displacement as a function of the loading force is calculated within the unloading hysteresis interval, and this average slope is taken as the average rate of change of the unloading hysteresis displacement. Specifically, the unloading hysteresis displacement is equal to the difference between the loading deformation displacement and the unloading deformation displacement under the same loading force value, reflecting the irreversible deformation of the sand core caused by the propagation of internal microcracks during the loading-unloading cycle. The unloading hysteresis displacements corresponding to each loading force value within the unloading hysteresis interval constitute a set of data points. The average slope of this interval is calculated using the formula: the average slope equals the difference between the final hysteresis displacement and the initial hysteresis displacement, divided by the difference between the final loading force value and the initial loading force value. This average slope reflects the rate at which the unloading hysteresis displacement increases with the increase of the loading force; a larger average slope indicates a more significant unloading hysteresis phenomenon and a more severe propagation of internal microcracks.

[0078] Based on the above calculations, the deformation recovery rate and the average change rate of unloading hysteresis displacement together constitute the core indicators for quantitatively evaluating the degree of microcrack propagation inside the sand core.

[0079] S50: When the deformation recovery rate is lower than the dynamic recovery rate threshold or the average change rate of the unloading hysteresis displacement exceeds the dynamic change rate threshold, it is determined that the sand core to be tested has internal microcrack propagation.

[0080] Finally, when the calculated deformation recovery rate is lower than the dynamic recovery rate threshold, or the calculated average rate of change of unloading hysteresis displacement exceeds the dynamic rate of change threshold, it is determined that the sand core under test has internal microcrack propagation. The deformation recovery rate reflects the sand core's ability to recover deformation after unloading. The closer the value is to 1, the stronger the elastic recovery ability of the sand core and the lower the degree of internal microcrack propagation; the lower the value, the greater the residual deformation and the more severe the internal microcrack propagation. The average rate of change of unloading hysteresis displacement reflects the rate at which the unloading hysteresis displacement increases with increasing loading force. The larger the value, the more significant the unloading hysteresis phenomenon and the more severe the internal microcrack propagation.

[0081] The dynamic recovery rate threshold and dynamic change rate threshold are dynamically determined critical values ​​based on test data from reference sand core samples of the same type and confirmed to be crack-free as the sand core to be tested. Since different batches and types of sand cores differ in material properties and geometric structures, using fixed static thresholds can lead to misjudgments or missed judgments. The dynamic threshold is obtained by collecting the deformation recovery rate and average change rate of unloading hysteresis displacement from multiple reference sand core samples, and then correcting for these differences by combining them with the geometric characteristics and mechanical properties of the sand core to be tested. This allows it to adaptively reflect the reference performance levels of different sand cores.

[0082] Specifically, when the deformation recovery rate is lower than the dynamic recovery rate threshold, it indicates that the residual deformation of the sand core after unloading exceeds the normal range, and the propagation of internal microcracks leads to a decrease in the material's elastic recovery ability. When the average change rate of the unloading hysteresis displacement exceeds the dynamic change rate threshold, it indicates that the unloading hysteresis phenomenon is significantly enhanced, and the internal microcracks continue to propagate during loading. Meeting either condition determines that the sand core has internal microcrack propagation. This determination result serves as the final output of the sand core assembly quality inspection, guiding quality sorting and process adjustments during production.

[0083] Specifically, when the deformation recovery rate is lower than the dynamic recovery rate threshold or the average change rate of the unloading hysteresis displacement exceeds the dynamic change rate threshold, it is determined that the sand core under test has internal microcrack propagation, including: Multiple reference sand core samples of the same type as the sand core to be tested and confirmed to be free of cracks were obtained, and the reference deformation recovery rate and the average change rate of the reference unloading hysteresis displacement of each reference sand core sample were obtained. Calculate the arithmetic mean of the baseline deformation recovery rate of each reference sand core sample, and use the product of the arithmetic mean and the first correction coefficient calculated based on the minimum profile curvature radius of the sand core to be tested as the dynamic recovery rate threshold. The first correction coefficient is determined by the ratio of the minimum profile radius of curvature to the reference radius of curvature, wherein the reference radius of curvature is the arithmetic mean of the minimum profile radii of curvature of multiple reference sand core samples; Calculate the arithmetic mean of the average change rate of the baseline unloading hysteresis displacement of each reference sand core sample, and use the product of the arithmetic mean and the second correction coefficient calculated based on the critical pressure value of the sand core to be tested as the dynamic change rate threshold. The second correction factor is determined by the ratio of the critical pressure value to the reference pressure value, wherein the reference pressure value is the arithmetic mean of the critical pressure values ​​of multiple reference sand core samples; The deformation recovery rate of the sand core to be tested is compared with the dynamic recovery rate threshold. If the deformation recovery rate is lower than the dynamic recovery rate threshold, it is determined that the sand core to be tested has internal microcrack propagation. The average rate of change of the unloading hysteresis displacement of the sand core to be tested is compared with the dynamic rate of change threshold. If the average rate of change of the unloading hysteresis displacement exceeds the dynamic rate of change threshold, it is determined that the sand core to be tested has internal microcrack propagation.

[0084] First, multiple reference sand core samples of the same type as the sand core to be tested and confirmed to be crack-free were obtained, and the reference deformation recovery rate and the reference average change rate of unloading hysteresis displacement were obtained for each reference sand core sample. The reference sand core samples are qualified sand cores confirmed to be free of any internal microcracks through non-destructive testing or destructive testing, and are used as the reference objects for dynamic threshold calibration. For each reference sand core sample, its deformation recovery rate and the average change rate of unloading hysteresis displacement in the crack-free state were calculated according to the aforementioned method and used as the reference values.

[0085] Furthermore, the arithmetic mean of the deformation recovery rates of each reference sand core sample is calculated. The product of this arithmetic mean and a first correction coefficient calculated based on the minimum profile radius of curvature of the sand core to be tested is used as the dynamic recovery rate threshold. The first correction coefficient is determined by the ratio of the minimum profile radius of curvature of the sand core to be tested to the reference radius of curvature. Specifically, the first correction coefficient equals the minimum profile radius of curvature of the sand core to be tested divided by the reference radius of curvature, where the reference radius of curvature is the arithmetic mean of the minimum profile radii of curvature of multiple reference sand core samples. The smaller the radius of curvature, the more severe the geometric change, the higher the stress concentration, and the easier it is for microcracks to propagate under the same load. Therefore, the dynamic recovery rate threshold should be lowered accordingly. When the first correction coefficient is less than 1, it indicates that the geometric change of the sand core to be tested is more severe than that of the reference sand core, and the dynamic recovery rate threshold is lowered; when the first correction coefficient is greater than 1, the threshold is raised.

[0086] Simultaneously, the arithmetic mean of the average change rate of the hysteresis displacement after unloading of each reference sand core sample is calculated. The product of this arithmetic mean and a second correction coefficient calculated based on the critical pressure value of the sand core to be tested is used as the dynamic change rate threshold. The second correction coefficient is determined by the ratio of the critical pressure value of the sand core to be tested to the reference pressure value. Specifically, the second correction coefficient equals the critical pressure value of the sand core to be tested divided by the reference pressure value, where the reference pressure value is the arithmetic mean of the critical pressure values ​​of multiple reference sand core samples. The critical pressure value reflects the load level at which the sand core transitions from elastic deformation to elastoplastic deformation. The smaller the critical pressure value, the lower the load-bearing capacity of the sand core, and the easier it is for microcracks to propagate under the same load. Therefore, the dynamic change rate threshold should be reduced accordingly. When the second correction coefficient is less than 1, the dynamic change rate threshold is lowered; when the second correction coefficient is greater than 1, the threshold is raised.

[0087] Furthermore, the deformation recovery rate of the sand core under test is compared with the dynamic recovery rate threshold. If the deformation recovery rate is lower than the dynamic recovery rate threshold, it is determined that the sand core under test has internal microcrack propagation. A deformation recovery rate lower than the dynamic threshold indicates that the residual deformation of the sand core after unloading exceeds the normal range, and the propagation of internal microcracks leads to a decrease in the material's elastic recovery ability.

[0088] Simultaneously, the average rate of change of unloading hysteresis displacement of the sand core under test is compared with the dynamic rate of change threshold. If the average rate of change of unloading hysteresis displacement exceeds the dynamic rate of change threshold, it is determined that the sand core under test has internal microcrack propagation. An average rate of change of unloading hysteresis displacement exceeding the dynamic threshold indicates that the unloading hysteresis phenomenon is significantly enhanced, and the internal microcracks continue to propagate during loading.

[0089] In summary, by using the above-mentioned dynamic threshold calculation method, the judgment threshold is correlated with the geometric features and mechanical properties of the sand core to be tested, thereby achieving adaptive adjustment of crack judgment and improving the accuracy and reliability of the test results.

[0090] In summary, the embodiments of this application have at least the following technical effects: This invention first acquires an image of the sand core head using an image acquisition component. Based on contour feature points, it automatically calibrates the force application contact position and stress concentration monitoring area, achieving precise positioning and standardization of the detection location and overcoming detection deviations caused by the arbitrariness of manual operation. Secondly, by applying a first pressure value to the force application contact position using a force application component, and collecting the initial micro-vibration sequence of the stress concentration monitoring area to calculate the wave energy value, and combining this with the contour curvature radius to calculate the wave energy threshold, it can effectively identify whether there are open-end cracks on the sand core surface, achieving early detection of micro-cracks. Thirdly, based on the open-end crack sensitivity index, the force application component is controlled to increase the loading force at a constant rate, collecting the deformation displacement sequence and calculating the deformation recovery rate and the average change rate of displacement after unloading. By comparing dynamic thresholds, it determines the propagation of internal micro-cracks, achieving quantitative detection of latent defects in the sand core under continuous load.

[0091] Finally, by fusing multi-sensor data and dynamically analyzing the multi-stage loading-unloading process, this invention constructs a complete detection chain from surface crack detection to internal micro-crack propagation determination, providing a quantifiable, traceable, and early warning intelligent detection solution for sand core assembly quality, and reducing the risk of batch casting scrap caused by latent defects in sand cores.

[0092] Example 2, as Figure 2 As shown, based on the same inventive concept as the energy-saving pump sand core assembly quality inspection method based on multi-sensor data provided in Embodiment 1, this embodiment of the invention also provides an energy-saving pump sand core assembly quality inspection system based on multi-sensor data, including: Image acquisition module 11 is used to acquire the core head image of the sand core to be tested through the image acquisition component, and to determine the force contact position and stress concentration monitoring area; The preloading module 12 is used to control the force application component to press against the force application contact position with a first pressure value, and to collect the initial micro-vibration sequence of the stress concentration monitoring area through the displacement sensing component and calculate the wave energy value. Sensitivity index acquisition module 13 is used to calculate the fluctuation energy threshold and acquire the opening crack sensitivity index based on the contour curvature radius of the stress concentration monitoring area. The loading and deformation analysis module 14 is used to control the force application component to increase the loading force at a constant rate starting from the first pressure value, and to collect the deformation displacement sequence at the force application contact position, and to calculate the deformation recovery rate and the average change rate of the unloading hysteresis interval in the deformation displacement sequence. The crack detection module 15 is used to determine that there is internal microcrack propagation in the sand core to be tested when the deformation recovery rate is lower than the dynamic recovery rate threshold or the average change rate of the unloading hysteresis displacement exceeds the dynamic change rate threshold.

[0093] The image acquisition module 11 is specifically used for: Specifically, the image acquisition component acquires images of the core head of the sand core to be tested, and determines the force contact location and stress concentration monitoring area, including: The image of the core head of the sand core to be tested is acquired using an image acquisition component; Extract the gray-level gradient abrupt change points at the junction of the core head and core body in the core head image, and mark the continuous area where the gray-level gradient abrupt change points are located as the stress concentration monitoring area; Identify the location with the minimum radius of curvature in the stress concentration monitoring area, and expand outward from the location with the minimum radius of curvature to form a circular area with a preset radius. Mark the circular area as the micro-vibration acquisition area. Using the stress concentration monitoring area as a reference, the core is moved a specified offset distance towards the end along the core extension direction of the core image, and the area covered after the movement is marked as the force contact position.

[0094] Specifically, the gray-level gradient abrupt change points at the junction of the core head and core body in the core head image are extracted, and the continuous region where the gray-level gradient abrupt change points are located is marked as the stress concentration monitoring region, including: The chip head image is converted to grayscale to obtain a grayscale image; Traverse the grayscale difference between each pixel and its neighboring pixels in the grayscale image, and mark the pixels whose grayscale difference exceeds the grayscale change threshold as the grayscale gradient abrupt change points. Among the gray-level gradient abrupt change points, spatially adjacent abrupt change points are clustered into a continuous abrupt change point set. During clustering, eight-neighbor adjacency is used as the criterion, and all interconnected abrupt change points are grouped into the same continuous abrupt change point set. Extract the abrupt change points in the continuous abrupt change point set whose radius of curvature is less than the radius of curvature threshold as stress concentration feature points, wherein the radius of curvature threshold is determined based on the average and standard deviation of the radius of curvature of all abrupt change points in the continuous abrupt change point set; Centered on the stress concentration feature point, search forward and backward along the extension direction of the continuous set of abrupt change points, and mark the continuous area covered by all abrupt change points within the search range as the stress concentration monitoring area.

[0095] The calculation steps for the specified offset distance include: Obtain the extension length and root width of the core tip in the core tip image; Images of the core heads of multiple historical sand core samples were collected, and the corresponding stress concentration monitoring area and force contact position were marked for each historical sand core sample. Record the extension length, core root width, and actual offset distance from the stress concentration monitoring area to the force contact point for each historical sand core sample; Using the extension length and core root width of the multiple historical sand core samples as input features, and the corresponding actual offset distance as the supervision signal, the first coefficient and the second coefficient are obtained by multiple linear regression fitting. The specified offset distance is obtained by adding the product of the extension length of the sand core to be tested and the first coefficient, and the product of the root width of the sand core to be tested and the second coefficient.

[0096] The preloading module 12 is specifically used for: Specifically, the force-applying component is controlled to press against the force-applying contact position with a first pressure value, and the initial micro-vibration sequence of the stress concentration monitoring area is collected by the displacement sensing component to calculate the wave energy value, including: Control the force-applying component to move unloaded to directly above the force-applying contact position, and control the force-applying component to move downward until it contacts the force-applying contact position; The force sensor feedback value is read at the moment of contact. When the force sensor feedback value reaches the first pressure value, the downward movement stops. The moment of contact is determined by the instantaneous state of the force sensor feedback value changing from zero to non-zero. The moment when the force sensor feedback value first exceeds zero is taken as the moment of contact. The force application component is maintained at the first pressure value state. The probe of the displacement sensing component is aligned with the micro-vibration acquisition area. During the maintenance period, the displacement change of the micro-vibration acquisition area is continuously acquired at a fixed sampling frequency to obtain an initial micro-vibration sequence composed of multiple displacement sampling points. By iterating through each displacement sampling point in the initial micro-vibration sequence, the square value of the displacement amplitude at each displacement sampling point is calculated. The sum of all the square values ​​is then divided by the total number of displacement sampling points to obtain the wave energy value.

[0097] The steps for determining the first pressure value include: Multiple standard sand core samples of the same type as the sand core to be tested and confirmed to be free of cracks were obtained. The stress concentration monitoring area and the force contact position were marked for each standard sand core sample. The force application component is controlled to increase the loading force at a constant rate. During the loading process, the micro-vibration sequence of the stress concentration monitoring area is synchronously collected by the displacement sensing component. The constant rate is determined based on the extension length of the sand core to be tested. The loading force value at which the displacement amplitude first exceeds the amplitude threshold in the micro-vibration sequence corresponding to each loading force value is recorded as the critical pressure value; The arithmetic mean of the critical pressure values ​​of each standard sand core sample is taken, and the product of the arithmetic mean and the safety factor is taken as the first pressure value. The safety factor is determined based on the fluctuation range of the critical pressure values ​​of the standard sand core samples and is a positive real number less than 1.

[0098] Specifically, the sensitivity index acquisition module 13 is used for: Specifically, based on the radius of curvature of the contour of the stress concentration monitoring region, the fluctuation energy threshold is calculated and the open crack sensitivity index is obtained, including: Extract the minimum contour radius of curvature from the stress concentration monitoring area; Obtain the reference fluctuation energy coefficient of a standard sand core sample of the same type as the sand core to be tested in a crack-free state. The reference fluctuation energy coefficient is obtained by averaging the product of the fluctuation energy values ​​of multiple standard sand core samples in a crack-free state and the corresponding minimum contour curvature radius. The ratio of the reference fluctuation energy coefficient to the minimum profile curvature radius is used as the fluctuation energy threshold. The ratio of the fluctuation energy value to the fluctuation energy threshold is used as the open crack sensitivity index.

[0099] The loading and deformation analysis module 14 is specifically used for: Specifically, the force-applying component is controlled to increase the loading force at a constant rate starting from the first pressure value, and the deformation displacement sequence at the force-applying contact position is collected. The deformation recovery rate and the average change rate of the unloading hysteresis interval in the deformation displacement sequence are calculated, including: If the sensitivity index for open cracks is greater than 1, the detection is terminated and it is determined that the sand core to be tested has open cracks. If the open crack sensitivity index is less than or equal to 1, then the force application component is controlled to increase the loading force at a constant rate starting from the first pressure value; During the loading process, the displacement sensing component continuously collects the loading deformation displacement at the force contact position to obtain a loading deformation displacement sequence corresponding to the loading force value. When the loading force value is increased to the second pressure value, the loading force is stopped. The second pressure value is the loading force value at which the displacement increment of adjacent sampling points in the loading deformation displacement sequence first falls below the linear reference displacement increment during the loading process. The linear reference displacement increment is obtained by multiplying the linear regression slope of the displacement increment and the loading force increment in the elastic deformation stage of the loading deformation displacement sequence by the current loading force increment. The elastic deformation stage is the range in which the loading force rises from the first pressure value to the critical pressure value. The ratio of the displacement increment to the loading force increment in the loading deformation displacement sequence fluctuates within a preset deviation range during the continuous loading interval. The force application component is controlled to reduce the loading force at the same constant rate. During the unloading process, the displacement sensing component continuously collects the unloading deformation displacement at the force application contact position to obtain the unloading deformation displacement sequence corresponding to the loading force value, until the loading force value is restored to the first pressure value. The difference between the loading deformation displacement and the unloading deformation displacement under the same loading force value is taken as the unloading hysteresis displacement. The unloading hysteresis displacements corresponding to each loading force value during the process of increasing the loading force value from the first pressure value to the second pressure value constitute the unloading hysteresis interval. The ratio of the endpoint displacement when the loading force value in the unloading deformation displacement sequence is the first pressure value to the loading displacement corresponding to the same loading force value in the loading deformation displacement sequence is taken as the deformation recovery rate. Calculate the average slope of the unloading hysteresis displacement as a function of the loading force within the unloading hysteresis interval, and use the average slope as the average rate of change of the unloading hysteresis displacement.

[0100] The crack detection module 15 is specifically used for: Specifically, when the deformation recovery rate is lower than the dynamic recovery rate threshold or the average change rate of the unloading hysteresis displacement exceeds the dynamic change rate threshold, it is determined that the sand core under test has internal microcrack propagation, including: Multiple reference sand core samples of the same type as the sand core to be tested and confirmed to be free of cracks were obtained, and the reference deformation recovery rate and the average change rate of the reference unloading hysteresis displacement of each reference sand core sample were obtained. Calculate the arithmetic mean of the baseline deformation recovery rate of each reference sand core sample, and use the product of the arithmetic mean and the first correction coefficient calculated based on the minimum profile curvature radius of the sand core to be tested as the dynamic recovery rate threshold. The first correction coefficient is determined by the ratio of the minimum profile radius of curvature to the reference radius of curvature, wherein the reference radius of curvature is the arithmetic mean of the minimum profile radii of curvature of multiple reference sand core samples; Calculate the arithmetic mean of the average change rate of the baseline unloading hysteresis displacement of each reference sand core sample, and use the product of the arithmetic mean and the second correction coefficient calculated based on the critical pressure value of the sand core to be tested as the dynamic change rate threshold. The second correction factor is determined by the ratio of the critical pressure value to the reference pressure value, wherein the reference pressure value is the arithmetic mean of the critical pressure values ​​of multiple reference sand core samples; The deformation recovery rate of the sand core to be tested is compared with the dynamic recovery rate threshold. If the deformation recovery rate is lower than the dynamic recovery rate threshold, it is determined that the sand core to be tested has internal microcrack propagation. The average rate of change of the unloading hysteresis displacement of the sand core to be tested is compared with the dynamic rate of change threshold. If the average rate of change of the unloading hysteresis displacement exceeds the dynamic rate of change threshold, it is determined that the sand core to be tested has internal microcrack propagation.

Claims

1. A method for inspecting the assembly quality of energy-saving pump sand cores based on multi-sensor data, characterized in that, The method includes: The image acquisition component is used to acquire images of the core head of the sand core to be tested, and the force contact location and stress concentration monitoring area are determined. The force-applying component is controlled to press against the force-applying contact position with a first pressure value, and the initial micro-vibration sequence of the stress concentration monitoring area is collected by the displacement sensing component to calculate the wave energy value, including: Control the force-applying component to move unloaded to directly above the force-applying contact position, and control the force-applying component to move downward until it contacts the force-applying contact position; The force sensor feedback value is read at the moment of contact. When the force sensor feedback value reaches the first pressure value, the downward movement stops. The moment of contact is determined by the instantaneous state of the force sensor feedback value changing from zero to non-zero. The moment when the force sensor feedback value first exceeds zero is taken as the moment of contact. The steps for determining the first pressure value include: Multiple standard sand core samples of the same type as the sand core to be tested and confirmed to be free of cracks were obtained. The stress concentration monitoring area and the force contact position were marked for each standard sand core sample. The force application component is controlled to increase the loading force at a constant rate. During the loading process, the micro-vibration sequence of the stress concentration monitoring area is synchronously collected by the displacement sensing component. The constant rate is determined based on the extension length of the sand core to be tested. The loading force value at which the displacement amplitude first exceeds the amplitude threshold in the micro-vibration sequence corresponding to each loading force value is recorded as the critical pressure value; The arithmetic mean of the critical pressure values ​​of each standard sand core sample is taken, and the product of the arithmetic mean and the safety factor is taken as the first pressure value. The safety factor is determined based on the fluctuation range of the critical pressure values ​​of the standard sand core sample and is a positive real number less than 1. The force application component is maintained at the first pressure value state. The probe of the displacement sensing component is aligned with the micro-vibration acquisition area. During the maintenance period, the displacement change of the micro-vibration acquisition area is continuously acquired at a fixed sampling frequency to obtain an initial micro-vibration sequence composed of multiple displacement sampling points. By iterating through each displacement sampling point in the initial micro-vibration sequence, the square value of the displacement amplitude of each displacement sampling point is calculated. The sum of all the square values ​​is then divided by the total number of displacement sampling points to obtain the wave energy value. Based on the contour curvature radius of the stress concentration monitoring area, the fluctuation energy threshold is calculated and the opening crack sensitivity index is obtained. The force application component is controlled to increase the loading force at a constant rate starting from the first pressure value, and the deformation displacement sequence at the force application contact position is collected. The deformation recovery rate and the average change rate of the unloading hysteresis interval in the deformation displacement sequence are calculated. When the deformation recovery rate is lower than the dynamic recovery rate threshold or the average change rate of the unloading hysteresis displacement exceeds the dynamic change rate threshold, it is determined that the sand core to be tested has internal microcrack propagation.

2. The energy-saving pump sand core assembly quality inspection method based on multi-sensor data according to claim 1, characterized in that, The image acquisition component acquires images of the core head of the sand core to be tested, and determines the force contact location and stress concentration monitoring area, including: The image of the core head of the sand core to be tested is acquired using an image acquisition component; Extract the gray-level gradient abrupt change points at the junction of the core head and the core body in the core head image, and mark the continuous area where the gray-level gradient abrupt change points are located as the stress concentration monitoring area; Identify the location with the minimum radius of curvature in the stress concentration monitoring area, and expand outward from the location with the minimum radius of curvature to form a circular area with a preset radius. Mark the circular area as the micro-vibration acquisition area. Using the stress concentration monitoring area as a reference, the core is moved a specified offset distance towards the end along the core extension direction of the core image, and the area covered after the movement is marked as the force contact position.

3. The energy-saving pump sand core assembly quality inspection method based on multi-sensor data according to claim 2, characterized in that, Extracting abrupt changes in grayscale gradient at the junction of the core head and core body in the core head image, and defining the continuous region containing these abrupt changes as the stress concentration monitoring region, including: The chip head image is converted to grayscale to obtain a grayscale image; Traverse the grayscale difference between each pixel and its neighboring pixels in the grayscale image, and mark the pixels whose grayscale difference exceeds the grayscale change threshold as the grayscale gradient abrupt change points. Among the gray-level gradient abrupt change points, spatially adjacent abrupt change points are clustered into a continuous abrupt change point set. During clustering, eight-neighbor adjacency is used as the criterion, and all interconnected abrupt change points are grouped into the same continuous abrupt change point set. Extract the abrupt change points in the continuous abrupt change point set whose radius of curvature is less than the radius of curvature threshold as stress concentration feature points, wherein the radius of curvature threshold is determined based on the average and standard deviation of the radius of curvature of all abrupt change points in the continuous abrupt change point set; Centered on the stress concentration feature point, search forward and backward along the extension direction of the continuous set of abrupt change points, and mark the continuous area covered by all abrupt change points within the search range as the stress concentration monitoring area.

4. The energy-saving pump sand core assembly quality inspection method based on multi-sensor data according to claim 2, characterized in that, The calculation steps for the specified offset distance include: Obtain the extension length and root width of the core tip in the core tip image; Images of the core heads of multiple historical sand core samples were collected, and the corresponding stress concentration monitoring area and force contact position were marked for each historical sand core sample. Record the extension length, core root width, and actual offset distance from the stress concentration monitoring area to the force contact point for each historical sand core sample; Using the extension length and core root width of the multiple historical sand core samples as input features, and the corresponding actual offset distance as the supervision signal, the first coefficient and the second coefficient are obtained by multiple linear regression fitting. The specified offset distance is obtained by adding the product of the extension length of the sand core to be tested and the first coefficient, and the product of the root width of the sand core to be tested and the second coefficient.

5. The energy-saving pump sand core assembly quality inspection method based on multi-sensor data according to claim 1, characterized in that, Based on the radius of curvature of the stress concentration monitoring region, the fluctuation energy threshold is calculated and the open crack sensitivity index is obtained, including: Extract the minimum contour radius of curvature from the stress concentration monitoring area; Obtain the reference fluctuation energy coefficient of a standard sand core sample of the same type as the sand core to be tested in a crack-free state. The reference fluctuation energy coefficient is obtained by averaging the product of the fluctuation energy values ​​of multiple standard sand core samples in a crack-free state and the corresponding minimum contour curvature radius. The ratio of the reference fluctuation energy coefficient to the minimum profile curvature radius is used as the fluctuation energy threshold. The ratio of the fluctuation energy value to the fluctuation energy threshold is used as the open crack sensitivity index.

6. The energy-saving pump sand core assembly quality inspection method based on multi-sensor data according to claim 1, characterized in that, The force-applying component is controlled to increase the loading force at a constant rate starting from the first pressure value, and the deformation displacement sequence at the force-applying contact position is collected. The deformation recovery rate and the average change rate of the unloading hysteresis interval in the deformation displacement sequence are calculated, including: If the sensitivity index for open cracks is greater than 1, the detection is terminated and the sand core to be tested is determined to have open cracks. If the open crack sensitivity index is less than or equal to 1, then the force application component is controlled to increase the loading force at a constant rate starting from the first pressure value; During the loading process, the displacement sensing component continuously collects the loading deformation displacement at the force contact position to obtain a loading deformation displacement sequence corresponding to the loading force value. When the loading force value is increased to the second pressure value, the loading force is stopped. The second pressure value is the loading force value at which the displacement increment of adjacent sampling points in the loading deformation displacement sequence first falls below the linear reference displacement increment during the loading process. The linear reference displacement increment is obtained by multiplying the linear regression slope of the displacement increment and the loading force increment in the elastic deformation stage of the loading deformation displacement sequence by the current loading force increment. The elastic deformation stage is the range in which the loading force rises from the first pressure value to the critical pressure value. The ratio of the displacement increment to the loading force increment in the loading deformation displacement sequence fluctuates within a preset deviation range during the continuous loading interval. The force application component is controlled to reduce the loading force at the same constant rate. During the unloading process, the displacement sensing component continuously collects the unloading deformation displacement at the force application contact position to obtain the unloading deformation displacement sequence corresponding to the loading force value, until the loading force value is restored to the first pressure value. The difference between the loading deformation displacement and the unloading deformation displacement under the same loading force value is taken as the unloading hysteresis displacement. The unloading hysteresis displacements corresponding to each loading force value during the process of increasing the loading force value from the first pressure value to the second pressure value constitute the unloading hysteresis interval. The ratio of the endpoint displacement when the loading force value in the unloading deformation displacement sequence is the first pressure value to the loading displacement corresponding to the same loading force value in the loading deformation displacement sequence is taken as the deformation recovery rate. Calculate the average slope of the unloading hysteresis displacement as a function of the loading force within the unloading hysteresis interval, and use the average slope as the average rate of change of the unloading hysteresis displacement.

7. The energy-saving pump sand core assembly quality inspection method based on multi-sensor data according to claim 1, characterized in that, When the deformation recovery rate is lower than the dynamic recovery rate threshold or the average change rate of the unloading hysteresis displacement exceeds the dynamic change rate threshold, it is determined that the sand core under test has internal microcrack propagation, including: Multiple reference sand core samples of the same type as the sand core to be tested and confirmed to be free of cracks were obtained, and the reference deformation recovery rate and the average change rate of the reference unloading hysteresis displacement of each reference sand core sample were obtained. Calculate the arithmetic mean of the baseline deformation recovery rate of each reference sand core sample, and use the product of the arithmetic mean and the first correction coefficient calculated based on the minimum profile curvature radius of the sand core to be tested as the dynamic recovery rate threshold. The first correction coefficient is determined by the ratio of the minimum profile radius of curvature to the reference radius of curvature, wherein the reference radius of curvature is the arithmetic mean of the minimum profile radii of curvature of multiple reference sand core samples; Calculate the arithmetic mean of the average change rate of the baseline unloading hysteresis displacement of each reference sand core sample, and use the product of the arithmetic mean and the second correction coefficient calculated based on the critical pressure value of the sand core to be tested as the dynamic change rate threshold. The second correction factor is determined by the ratio of the critical pressure value to the reference pressure value, wherein the reference pressure value is the arithmetic mean of the critical pressure values ​​of multiple reference sand core samples; The deformation recovery rate of the sand core to be tested is compared with the dynamic recovery rate threshold. If the deformation recovery rate is lower than the dynamic recovery rate threshold, it is determined that the sand core to be tested has internal microcrack propagation. The average rate of change of the unloading hysteresis displacement of the sand core to be tested is compared with the dynamic rate of change threshold. If the average rate of change of the unloading hysteresis displacement exceeds the dynamic rate of change threshold, it is determined that the sand core to be tested has internal microcrack propagation.

8. An energy-saving pump sand core assembly quality inspection system based on multi-sensor data, characterized in that, The method for inspecting the quality of energy-saving pump sand core assembly based on multi-sensor data as described in any one of claims 1-7 includes: The image acquisition module is used to acquire images of the core head of the sand core to be tested through the image acquisition component, and to determine the force contact position and stress concentration monitoring area; The preloading module is used to control the force-applying component to press against the force-applying contact position with a first pressure value, and to collect the initial micro-vibration sequence of the stress concentration monitoring area through the displacement sensing component, and calculate the wave energy value, including: Control the force-applying component to move unloaded to directly above the force-applying contact position, and control the force-applying component to move downward until it contacts the force-applying contact position; The force sensor feedback value is read at the moment of contact. When the force sensor feedback value reaches the first pressure value, the downward movement stops. The moment of contact is determined by the instantaneous state of the force sensor feedback value changing from zero to non-zero. The moment when the force sensor feedback value first exceeds zero is taken as the moment of contact. The steps for determining the first pressure value include: Multiple standard sand core samples of the same type as the sand core to be tested and confirmed to be free of cracks were obtained. The stress concentration monitoring area and the force contact position were marked for each standard sand core sample. The force application component is controlled to increase the loading force at a constant rate. During the loading process, the micro-vibration sequence of the stress concentration monitoring area is synchronously collected by the displacement sensing component. The constant rate is determined based on the extension length of the sand core to be tested. The loading force value at which the displacement amplitude first exceeds the amplitude threshold in the micro-vibration sequence corresponding to each loading force value is recorded as the critical pressure value; The arithmetic mean of the critical pressure values ​​of each standard sand core sample is taken, and the product of the arithmetic mean and the safety factor is taken as the first pressure value. The safety factor is determined based on the fluctuation range of the critical pressure values ​​of the standard sand core sample and is a positive real number less than 1. The force application component is maintained at the first pressure value state. The probe of the displacement sensing component is aligned with the micro-vibration acquisition area. During the maintenance period, the displacement change of the micro-vibration acquisition area is continuously acquired at a fixed sampling frequency to obtain an initial micro-vibration sequence composed of multiple displacement sampling points. By iterating through each displacement sampling point in the initial micro-vibration sequence, the square value of the displacement amplitude of each displacement sampling point is calculated. The sum of all the square values ​​is then divided by the total number of displacement sampling points to obtain the wave energy value. The sensitivity index acquisition module is used to calculate the fluctuation energy threshold and acquire the opening crack sensitivity index based on the contour curvature radius of the stress concentration monitoring area. The loading and deformation analysis module is used to control the force application component to increase the loading force at a constant rate starting from the first pressure value, and to collect the deformation displacement sequence at the force application contact position, and to calculate the deformation recovery rate and the average change rate of the unloading hysteresis interval in the deformation displacement sequence. The crack detection module is used to determine that there is internal microcrack propagation in the sand core to be tested when the deformation recovery rate is lower than the dynamic recovery rate threshold or the average change rate of the unloading hysteresis displacement exceeds the dynamic change rate threshold.

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