Method and apparatus for detecting bond strength of mortar

Abstract

The present application relates to the technical field of intelligent sensing system, in particular to a mortar bonding strength detection method and device. The present application firstly carries out multi-dimensional synchronous sampling on displacement, pulling force and pulling force growth rate in the pulling process, eliminates the misjudgment risk of single threshold being easily disturbed, and provides reliable data basis for subsequent analysis; secondly, through analyzing the cooperative fluctuation characteristics of displacement and pulling force, a nonlinear discrete index is determined to accurately distinguish the gap free state and the effective loading state, and the sensing accuracy under complex working conditions is significantly improved; then, the pulling force growth rate and the nonlinear discrete index are fused to quantize the impact risk caused by the coupling of high speed and free in real time, and the active accumulation and sensitive control of the risk are realized; finally, according to different pulling contact stages, the control strategy is adaptively switched, the overshoot risk is eliminated from the physical root, the detection process is stable and reliable, the accuracy of mortar bonding strength detection is effectively improved, and the possibility of low strength detection is reduced.

Description

Technical Field

[0001] This invention relates to the field of intelligent sensing system technology, specifically to a method and equipment for testing the bonding strength of mortar. Background Technology

[0002] In construction engineering, the pull-out strength of facing bricks or adhesive mortar is a key indicator for evaluating construction quality. According to industry standards (such as JGJ110 "Standard for Testing the Bond Strength of Facing Bricks in Building Engineering"), the testing process usually requires applying a vertical and uniform tensile force to the specimen and strictly controlling the loading rate to obtain accurate strength data.

[0003] In actual field testing, a common engineering phenomenon is called stiffness abrupt change. Specifically, at the initial stage of the test, the pull-out apparatus needs to eliminate the base mounting gap, thread fit gap, and the free stroke of the adjusting screw. During this gap elimination phase, the system is in a free state with minimal resistance, causing the servo motor to easily accelerate under force feedback closed-loop control to catch up with the target pulling force. When the gap is completely eliminated and the pull rod and specimen instantly enter a tight contact state (i.e., the moment of stiffness abrupt change), the system stiffness suddenly increases from almost zero to a maximum value. At this moment, if the motor maintains a high feed speed, the accumulated kinetic energy cannot be dissipated instantly, resulting in a large overshoot load at the moment of contact.

[0004] Currently, most conventional control methods rely on a single force threshold to determine the contact state. However, when unexpected contact is detected, overload has often already occurred, directly causing microscopic pre-damage to the brittle mortar interface. This results in a lower measured bond strength value, severely affecting the accuracy of the test results. Existing technologies can only determine whether overload has occurred through a single mechanical threshold, but cannot proactively eliminate the risk of accumulated kinetic energy before contact occurs, leading to a lower measured bond strength. Summary of the Invention

[0005] To address the problem that existing technologies rely solely on a single mechanical threshold to determine whether an overload has occurred, failing to proactively eliminate the risk of accumulated kinetic energy before contact occurs, thus leading to lower measured bond strength, the present invention aims to provide a method and equipment for testing mortar bond strength. The specific technical solution adopted is as follows: The displacement, tensile force, and tensile force growth rate at each sampling moment were obtained during the pull-out test of mortar bond strength. Based on the coordinated changes between displacement and tension at each sampling time, the corresponding nonlinear discrete index is determined; based on the tension growth rate and nonlinear discrete index at each sampling time, the corresponding overshoot risk index is analyzed; the overshoot risk index at each sampling time is superimposed and analyzed to determine the corresponding cumulative risk index. Based on the magnitude of the cumulative danger index at each sampling time, the corresponding rate limit ratio is determined; based on the tensile force and the nonlinear discrete index at each sampling time, the corresponding pull-out contact stage is determined; and based on the pull-out contact stage and the rate limit ratio, the mortar bond strength pull-out test is performed.

[0006] Furthermore, the method for obtaining the nonlinear discrete exponent includes: Based on the numerical fluctuations of displacement and tension at each sampling time and a preset number of previous sampling times, a mechanical feature matrix is ​​constructed; the mechanical feature matrix is ​​solved to determine the main trend feature value and the non-correlated feature value; the main trend feature value is used as the denominator and the non-correlated feature value is used as the numerator, and the nonlinear discrete index at each sampling time is determined by ratio calculation.

[0007] Furthermore, the method for constructing the mechanical feature matrix includes: The covariance matrix between displacement and tension at each sampling time and a preset number of previous sampling times is used as the mechanical characteristic matrix.

[0008] Furthermore, the method for obtaining the overshoot risk index includes: The overshoot risk index at each sampling time is determined by multiplying the square of the pull force growth rate at each sampling time with the nonlinear discrete index.

[0009] Furthermore, the method for obtaining the cumulative risk index includes: The time interval between two adjacent sampling times is taken as the sampling period; the product of the overshoot risk index and the sampling period is taken as the periodic risk index at each sampling time. The cumulative risk index for each sampling moment is determined by summing the periodic risk indices of each sampling moment and all previous sampling moments.

[0010] Furthermore, the method for obtaining the rate limiting ratio includes: By negatively mapping the cumulative risk index at each sampling time, the corresponding risk limit ratio is determined. If the risk limit ratio is greater than or equal to the preset minimum ratio threshold, then the risk limit ratio will be used as the rate limit ratio. If the risk limit ratio is less than the preset minimum ratio threshold, then the preset minimum ratio threshold will be used as the rate limit ratio.

[0011] Furthermore, the method for obtaining the risk limit ratio includes: A risk comparison value is determined based on the ratio between the cumulative risk index at each sampling time and the preset maximum risk threshold; the difference between the positive integer 1 and the risk comparison value is used as the risk limit ratio.

[0012] Furthermore, the method for determining the pull-out contact stage includes: The sampling time when the corresponding tensile force is greater than the preset tensile force threshold and the corresponding nonlinear discrete exponent is less than the preset discrete threshold is taken as the instantaneous stable time; in terms of time sequence, the number of consecutive instantaneous stable times before each instantaneous stable time is taken as the judgment number; the instantaneous stable time when the corresponding judgment number is greater than the preset judgment number threshold is taken as the temporal stable time. The pull-out contact phase at each time series stable moment is defined as a stable pull-out contact phase; the pull-out contact phase at all other sampling moments outside of the time series stable moments is defined as a dangerous pull-out contact phase.

[0013] Furthermore, the method for conducting pull-out tests on mortar bond strength includes: If the mortar bond strength pull-out test is conducted at the standard pull-out rate, the mortar bond strength will be tested. If the mortar is in a dangerous pull-out contact stage, the product of the standard pull-out rate and the rate limit ratio shall be used as the actual pull-out rate, and the mortar bond strength pull-out test shall be conducted using the actual pull-out rate.

[0014] The present invention also proposes a mortar bonding strength testing device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements any of the steps of the mortar bonding strength testing method described above.

[0015] The present invention has the following beneficial effects: This invention first samples data from multiple dimensions during the mortar strength testing process, effectively reducing potential misjudgments caused by a single threshold and providing a reliable data foundation for subsequent state identification and analysis. Second, by analyzing the coordinated fluctuations of displacement and tensile force, it accurately distinguishes between the gap-free state and the effective loading state, significantly improving the perception accuracy under complex conditions such as rough walls and thread corrosion. Third, by integrating and analyzing the tensile force growth rate and nonlinear discrete index during the strength testing process, it obtains the danger index at each moment, enabling proactive quantification of impact risk. This allows for real-time calculation of the pull-out risk generated by high-speed and free coupling during the gap-existing stage, effectively improving control sensitivity. Finally, by performing different strength pull-out testing processes based on different pull-out contact stages, it helps eliminate overshoot risks from a physical perspective, ensuring stability during the strength testing process and significantly improving the accuracy and reliability of mortar bond strength testing. Attached Figure Description

[0016] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of a mortar bonding strength testing method provided in one embodiment of the present invention. Detailed Implementation

[0018] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a mortar bonding strength testing method and device proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0020] The specific scheme of the mortar bonding strength testing method and equipment provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0021] Please see Figure 1 The diagram illustrates a flowchart of a mortar bonding strength testing method according to an embodiment of the present invention, the method comprising: Step S101: Obtain the displacement, tension, and tension growth rate of the pull-out instrument at each sampling moment during the strength pull-out test.

[0022] Since the tensile strength test involves continuously increasing the tensile force until the mortar between the specimens breaks, it measures the bond strength of the mortar. During this process, the analytical data at each moment is dynamically changing. Therefore, to ensure the accuracy of the analysis, it is necessary to acquire the analytical data (i.e., displacement, tensile force, and tensile force growth rate) at each sampling moment, so that subsequent data analysis and calculations are based on a complete data foundation.

[0023] This invention takes into account that a single tensile force can only determine whether gap elimination has ended, but cannot quantify the changing trend during the gap elimination process (when the gap still exists and is being eliminated). Meanwhile, the displacement continuously increases during the gap elimination process and decreases instantaneously after the gap disappears. The rate of increase of tensile force directly reflects the kinetic energy risk (destructive energy) generated during the gap elimination process. Therefore, in order to achieve real-time quantification of the changes during the gap elimination process, it is necessary to obtain sampling data in three dimensions: displacement, tensile force, and tensile force growth rate, to ensure the accuracy of subsequent data analysis and feature calculation.

[0024] As an example, in a specific implementation of this invention, the method for obtaining the displacement, tension, and tension growth rate at each sampling moment during the strength pull-out test is as follows: First, the global sampling frequency is set to 1000 Hz (i.e., the sampling time interval is 1 millisecond); second, the system reads the pulse count value of the servo motor encoder of the pull-out instrument, converts it into the feed position of the motor output shaft at the current sampling moment through the mechanical transmission ratio, and records it as displacement (unit: millimeters); then, the system triggers the analog-to-digital converter (ADC) to read the real-time tension at the current sampling moment from the tension sensor, and records it as tension (unit: kilonewtons, kN), wherein the tension sensor can be set at the connection between the traction rope and the specimen. At the connection point, the tensile force on the test piece is detected in real time. Then, the system differentiates the tensile force at each moment (e.g., divides the tensile force at each moment by the sampling time interval) to obtain the tensile force growth rate (unit: kilonewtons per second) at each sampling moment. Finally, to facilitate data storage and subsequent data analysis and calculation, the displacement, tensile force, and tensile force growth rate at each sampling moment are constructed into a data source matrix. Specifically, the data source matrix has three rows (e.g., the first row represents displacement, the second row represents tensile force, and the third row represents tensile force growth rate), and the number of columns is the same as the number of sampling moments in the strength detection process. The sampling data in each row is stored in chronological order from left to right.

[0025] Step S102: Determine the corresponding nonlinear discrete index based on the coordinated change between displacement and tension at each sampling time; analyze the corresponding overshoot risk index based on the tension growth rate and nonlinear discrete index at each sampling time; perform superposition analysis on the overshoot risk index at each sampling time to determine the corresponding cumulative risk index.

[0026] During the gap elimination stage, the connection between the traction rope and the specimen is in a normal, close fit. Due to the gap, the traction rope will sway, resulting in displacements of varying magnitudes. Furthermore, the traction force is not fully applied to the specimen at this stage, leading to a relatively small and randomly fluctuating actual tensile force on the specimen. After the gap is eliminated, the connection between the traction rope and the specimen is in tight contact, with no unnecessary movement. At this point, the displacement of the traction rope increases systematically over time, and the tight contact allows the traction force to be fully applied to the specimen. Similarly, the tensile force increases systematically over time. Therefore, combining the temporal and coordinated changes in displacement and tensile force allows for accurate quantification of the characteristics of the gap elimination stage, providing a reliable basis for subsequent identification of the pull-out contact stage.

[0027] The physical reason why the presence of gaps leads to a decrease in strength testing is that the traction device accumulates excessive kinetic energy during the gap's existence. When the traction rope, carrying significant kinetic energy, contacts the specimen, it damages the mortar's microstructure, resulting in a decrease in strength. Therefore, it is necessary to quantify this destructive kinetic energy during the gap's existence, i.e., introduce the tensile force growth rate, as the magnitude of the tensile force growth rate is positively correlated with the kinetic energy. Furthermore, based on the above analysis, it is known that the nonlinear discrete index can characterize the gap elimination stage. Therefore, this embodiment of the invention uses the tensile force growth rate and the nonlinear discrete index for data analysis, which can represent the impact risk during the gap elimination process and avoid misjudging the normal pull-out process.

[0028] It should be noted that since the risk accumulates continuously over time, superimposing the risk at each sampling moment can accurately represent the cumulative risk (cumulative risk index) at each moment during the mortar bond strength test. This is beneficial for the subsequent dynamic suppression and control of the motor drive speed, thereby avoiding pre-damage to the brittle mortar interface from a physical source.

[0029] Step S103: Determine the corresponding rate limit ratio based on the value of the cumulative danger index at each sampling time; determine the corresponding pull-out contact stage based on the tensile force and the nonlinear discrete index at each sampling time; and perform mortar bond strength pull-out test according to the pull-out contact stage and the rate limit ratio.

[0030] Since a higher cumulative hazard index indicates more destructive kinetic energy accumulated during the gap elimination stage, it is more necessary to limit the pull-out speed (i.e., the rate of increase of the tensile force applied to the specimen by the pull-out instrument, the increase of tensile force per unit time). In other words, the magnitude of the cumulative hazard index is positively correlated with the rate limit ratio. By limiting the pull-out speed during gap elimination, pre-damage to mortar bond strength testing can be reduced.

[0031] During the gap elimination phase (when the gap still exists), the traction rope is not in close contact with the specimen, and the tension is relatively small. After the gap is eliminated, the traction rope and the specimen begin to make close contact, and the tension measured at this point is the larger tension during normal pull-out. Therefore, the tension can be used to preliminarily determine the pull-out contact stage at each sampling moment. Furthermore, the nonlinear dispersion index calculated above can further characterize the data features of the gap elimination phase. Thus, the pull-out contact stage at each sampling moment can be determined jointly by the tension and the nonlinear dispersion index, significantly improving the accuracy of the determination.

[0032] Since effective pull-out strength testing does not involve gaps, but gaps exist in the initial stage of testing, using the same control strategy can lead to reduced testing efficiency or even reduced testing strength. Therefore, adaptive mortar bond strength pull-out testing is required based on different pull-out contact stages. This ensures both safety before testing (with gaps) and accuracy during testing (without gaps), significantly improving the accuracy of mortar bond strength testing and effectively preventing the final measured mortar bond strength from being too low.

[0033] In summary: First, this invention samples data from multiple dimensions during the strength testing process, effectively reducing potential misjudgments caused by a single threshold and providing a reliable data foundation for subsequent state identification and analysis. Second, by analyzing the coordinated fluctuations of displacement and tension, it accurately distinguishes between the gap free state and the effective loading state, significantly improving the perception accuracy under complex conditions such as rough walls and thread corrosion. Third, by fusing and analyzing the tension growth rate and nonlinear discrete index during the strength testing process, it obtains the danger index at each moment in the strength testing process, achieving proactive quantification of impact risk. It can calculate the pull-out risk caused by high-speed and free coupling in real time during the gap stage, effectively improving the sensitivity of control. Finally, by conducting different strength pull-out testing processes based on different pull-out contact stages, it helps to eliminate overshoot risks from a physical source, ensuring the stability of the strength testing process and significantly improving the accuracy and reliability of mortar bonding strength testing.

[0034] Preferably, in some possible implementations of the embodiments of the present invention, the method for obtaining the nonlinear discrete index includes: Based on the numerical fluctuations of displacement and tension at each sampling time and a preset number of previous sampling times, a mechanical feature matrix is ​​constructed; the mechanical feature matrix is ​​solved to determine the main trend feature value and the non-correlated feature value; the main trend feature value is used as the denominator and the non-correlated feature value is used as the numerator, and the nonlinear discrete index at each sampling time is determined by ratio calculation.

[0035] Since the state data at a single sampling moment cannot reflect the overall movement trend, continuous observation in the time dimension is required. Considering that the state data at each sampling moment is closely related to the state at previous sampling moments, this embodiment of the invention uses data from each sampling moment and a preset number of previous sampling moments for analysis, which can improve the reliability and stability of the calculation results at each sampling moment. It should be noted that the reason for not using data from each sampling moment and all previous sampling moments for analysis is that using global historical data would introduce the gap influence that may exist in the initial stage of intensity detection in each subsequent sampling moment, resulting in large errors in all subsequent analysis and calculation results. Furthermore, if the number of sampling moments before each sampling moment is insufficient (less than the preset number), the average value of the data from all previous sampling moments is used to make up the difference, avoiding the calculation crash that may be caused by insufficient data.

[0036] In one specific implementation of this invention, the preset quantity is set to 9. The implementer may also set other preset quantities according to the specific implementation scenario, which will not be elaborated or limited here.

[0037] Step S102 explains that during the gap elimination stage, displacements of varying magnitudes occur, and tension fluctuates randomly; after gap elimination, both displacement and tension increase in an orderly manner. That is, the fluctuations in displacement and tension are similar before and after gap elimination: random before gap elimination and orderly after. Therefore, the presence or absence of a gap can be accurately characterized based on the coordinated fluctuations of displacement and tension values. The construction of the mechanical characteristic matrix aims to unify the comparison of data in both displacement and tension dimensions, thereby improving the stability of subsequent calculations.

[0038] On the one hand, before constructing the mechanical feature matrix, since displacement and tension have different dimensions and large differences in numerical magnitude, directly using the original data for calculation will cause the features of large data to mask the features of small data, reducing the reliability of the results. Therefore, before constructing the mechanical feature matrix, it is necessary to standardize the displacement and tension. Specifically, all displacements (or tensions) at each sampling time and at the previous preset number (9) sampling times (a total of 10) are used as input, and the Z-score standardization algorithm is used to output the standardized displacements (or tensions). If all displacements (or tensions) at each sampling time and at the previous preset number (9) sampling times (a total of 10) are the same, then all standardized displacements (or tensions) are directly set to 0, in order to prevent division by zero errors that occur when the data are completely equal. In other specific implementations of this invention, other standardization algorithms such as maximum-minimum value normalization and maximum value normalization can also be used. Implementers can set them according to the specific implementation scenario, which will not be elaborated or limited here. Among them, the Z-score normalization algorithm, maximum and minimum value normalization and maximum value normalization are all well-known techniques and need not be elaborated here.

[0039] The maximum and minimum values ​​used in the maximum-minimum normalization can be obtained according to the actual situation. For example, when multiple values ​​can be obtained during the implementation process and it is necessary to compare the size relationship between different values, multiple values ​​can be counted to obtain the maximum and minimum values. However, when only a single value can be obtained during the implementation process or it is not necessary to compare the size relationship between different values, the maximum and minimum values ​​can be obtained by counting based on a large amount of historical experimental data or prior data obtained earlier. Unless otherwise specified, the method for obtaining the maximum and minimum values ​​used in the maximum-minimum normalization in all embodiments of the present invention is the same as the method for obtaining the maximum and minimum values, and will not be described in detail one by one.

[0040] On the other hand, before constructing the mechanical feature matrix, since the actual motor is stationary or at low speed, the sensor signal may only include weak background noise. Data analysis in this case would lead to unstable calculations due to the small values. Therefore, to ensure the stability of the calculation results, background energy detection is required after the above standardization process. Specifically, the sum of all standardized displacements and standardized tensions (20 in total) is recorded as the total fluctuation energy. If the total fluctuation energy is less than a preset noise floor threshold, it indicates that the current signal of the system is submerged in noise, and this is invalid data; the nonlinear dispersion index is directly set to 0. If the total fluctuation energy is greater than or equal to the preset noise floor threshold, it indicates the presence of significant motion signals. In this case, the mechanical feature matrix can be constructed, and the feature solution can be performed normally. In a specific implementation of this invention, the preset noise floor threshold is determined based on the static noise level of the sensor, for example, a value of 0.01.

[0041] By solving the mechanical characteristic matrix, the original displacement-tension data can be mapped to the principal component direction, thereby separating the main trend (main trend eigenvalue, representing the main extension direction of the data) and uncorrelated fluctuations (uncorrelated eigenvalue, representing the degree of dispersion of the data perpendicular to the main extension direction). Based on the above analysis, it is known that during the gap phase, the fluctuations in displacement and tension are random, meaning that the main trend eigenvalue is small (because the data is not along the main extension direction), and the uncorrelated eigenvalue is large (because the data is randomly discrete). During the gap phase, the fluctuations in displacement and tension are ordered, meaning that the main trend eigenvalue is large (because the data is ordered), and the uncorrelated eigenvalue is small (because the data is not discrete). The main trend eigenvalue is greater than the uncorrelated eigenvalue. Therefore, in a specific implementation of this invention, the nonlinear dispersion index can be calculated using the following formula: in, Represents the nonlinear discrete exponent at the k-th sampling time; This represents the non-associated feature value at the k-th sampling time. Let represent the main trend feature value at the k-th sampling time, where the main trend feature value is greater than the non-correlated feature value; It represents a very small positive number, intended to prevent the denominator from being zero; The square root function is used to convert the variance dimension represented by the eigenvalues ​​of the covariance matrix into the standard deviation dimension, thus more intuitively reflecting the proportion of linear dispersion of data in the main trend and non-correlated directions. When the non-linear dispersion exponent is close to 0, it indicates that the non-correlated eigenvalues ​​are much smaller than the main trend eigenvalues, the data distribution is extremely flat, and the displacement and tension show a linear distribution. This corresponds to the system being in a stable contact state (without gaps), where displacement and force are strictly linearly correlated. The larger the non-linear dispersion exponent, the higher the proportion of non-correlated eigenvalues ​​in the total fluctuation, and the wider the data distribution. This corresponds to the system being in a gap-free state (with gaps), where displacement changes but tension fluctuates disorderly. In other words, the larger the non-linear dispersion exponent, the looser and more disordered the system is, and the higher the potential risk of overshoot.

[0042] In one specific implementation of this invention, the method for determining the main trend eigenvalue and the non-correlated eigenvalue is as follows: the mechanical feature matrix is ​​decomposed into eigenvalues ​​to calculate two eigenvalues. The larger eigenvalue is taken as the main trend eigenvalue, and the smaller eigenvalue is taken as the non-correlated eigenvalue. It should be noted that the calculation process of eigenvalue decomposition is a well-known technique and will not be described in detail here.

[0043] Preferably, in some possible implementations of the embodiments of the present invention, the method for constructing the mechanical feature matrix includes: The covariance matrix between displacement and tension at each sampling time and a preset number of previous sampling times is used as the mechanical characteristic matrix.

[0044] The covariance matrix can reflect the correlation between two dimensional variables (displacement and tension). In other specific implementations of this invention, correlation coefficient matrix and mutual information matrix can also be used. These are well-known technologies, and implementers can set them according to specific implementation scenarios. No limitation is made here.

[0045] Preferably, in some possible implementations of the embodiments of the present invention, the method for obtaining the overshoot risk index includes: The overshoot risk index at each sampling time is determined by multiplying the square of the pull force growth rate at each sampling time with the nonlinear discrete index.

[0046] Since the maximum tensile force growth rate that different drawing instruments can apply varies greatly in reality, using the actual tensile force growth rate for calculation would reduce the universality of the calculation results. Therefore, before calculating the overshoot risk index, it is necessary to standardize the tensile force growth rate at each sampling moment. Specifically, the system reads the drawing speed range of the drawing instrument (i.e., including the maximum and minimum tensile force growth rates during the drawing process), takes the tensile force growth rate at each sampling moment as well as the maximum and minimum tensile force growth rates as input, and outputs the standardized tensile force growth rate using the maximum-minimum value standardization algorithm.

[0047] In other specific implementations of the embodiments of the present invention, other standardization processing algorithms such as maximum value normalization may also be used. Implementers may set them according to the specific implementation scenario, which will not be elaborated or limited here.

[0048] Since a higher tensile force growth rate results in greater kinetic energy and a greater risk of impact, and a larger nonlinear dispersion index indicates a more loosely structured and disordered system, the potential for overshoot is higher. Therefore, this embodiment of the invention uses the product of the square of the tensile force growth rate and the nonlinear dispersion index to represent the overshoot risk index at each sampling time. The reason for using the square of the tensile force growth rate is that kinetic energy is positively correlated with the square of the tensile force growth rate; the larger the square of the tensile force growth rate, the greater the potential destructive energy. Therefore, the overshoot risk index can be expressed by the following formula: in, This represents the overshoot risk index at the k-th sampling time. This represents the square of the standardized rate of increase of the tension at the k-th sampling time, i.e., the kinetic energy term; The nonlinear discrete index represents the nonlinear discrete index at the k-th sampling time. Its function is to convert the kinetic energy term into impact risk. When there is no gap, the nonlinear discrete index is very small (close to 0). At this time, even if the tension growth rate is very high, the calculated overshoot risk index is close to 0. When there is a gap, the nonlinear discrete index is larger, and the overshoot risk index will increase sharply with the increase of the tension growth rate. The risk gain coefficient is used to adjust the model's sensitivity to risk. In this embodiment, the range is set between [0.5, 5], with a preferred value of a positive integer of 1 to maintain the original physical magnitude. It can be adjusted according to the specific implementation scenario. Within this range, the larger the risk gain coefficient (e.g., 4), the more sensitive the system is to kinetic energy risk. The calculated overshoot risk index is proportionally amplified, and the system will trigger forced deceleration earlier, with the control response becoming more conservative. Conversely, the smaller the risk gain coefficient (e.g., 0.5), the higher the system's tolerance to kinetic energy risk. The overshoot risk index increases more slowly, and the system is allowed to maintain high-speed operation for a longer period during the gap elimination phase, with the control response becoming more aggressive. The overshoot risk index accurately quantifies the physical fact that the faster the system runs in the gap, the greater the collision risk. It only outputs a high value when the system is in a state that is both fast and chaotic, thereby avoiding misjudgment of the normal stretching process.

[0049] Preferably, in some possible implementations of the embodiments of the present invention, the method for obtaining the cumulative risk index includes: The time interval between two adjacent sampling times is taken as the sampling period; the product of the overshoot risk index and the sampling period is taken as the periodic risk index at each sampling time. The cumulative risk index for each sampling moment is determined by summing the periodic risk indices of each sampling moment and all previous sampling moments.

[0050] The pulling process is a continuous process, and the data at each sampling moment can only represent the pulling state at a single moment. In order to conform to the laws of reality, this embodiment of the invention obtains the time interval between two adjacent sampling moments (the current sampling moment and the moment after the current sampling moment). By multiplying it with the overshoot risk index at the current sampling moment, the discrete overshoot risk index can be transformed into a periodic risk index that can represent the continuous reality. The reason for multiplying the overshoot risk index at the current sampling moment with the periodic risk index is that the overshoot risk index at the current sampling moment is determined by the state at the current sampling moment, and this state will continue for the entire time period between the current sampling moment and the next sampling moment.

[0051] Since the actual cumulative risk at each sampling moment during the pulling process does not disappear instantaneously, but is a process that accumulates over time; at the same time, kinetic energy will also dissipate naturally over time (such as friction loss); therefore, the embodiments of the present invention accumulate the periodic risk index of each sampling moment and all previous sampling moments, which can represent the actual risk magnitude at each sampling moment, and is beneficial to improving the accuracy of subsequent analysis processes.

[0052] In one specific implementation of this invention, the cumulative risk index can be expressed using the following summation formula: in, This represents the cumulative risk index at the (k+1)th sampling time. This represents the cumulative risk index at the k-th sampling time. This represents the cumulative risk index at the beginning of the entire pull-out strength test, since data from the previous moment is unavailable. This indicates the overshoot risk index at the start of the entire pull-out strength test; This represents the overshoot risk index at the (k+1)th sampling time. Indicates the sampling period; The forgetting factor (with a value range of (0,1), preferably 0.98) serves to ensure that the historical cumulative risk index increases proportionally in each sampling period. The cumulative hazard index decays exponentially over time until it approaches zero if the motor stops moving. This simulates the gradual dissipation of kinetic energy after the system stops, preventing the influence of the system's long-standing motion history. Finally, it should be noted that the cumulative hazard index, as a continuously changing value, can intuitively tell the controller how much dangerous energy the system has accumulated that must be released or limited.

[0053] Preferably, in some possible implementations of the embodiments of the present invention, the method for obtaining the rate limiting ratio includes: By negatively mapping the cumulative risk index at each sampling time, the corresponding risk limit ratio is determined. If the risk limit ratio is greater than or equal to the preset minimum ratio threshold, then the risk limit ratio will be used as the rate limit ratio. If the risk limit ratio is less than the preset minimum ratio threshold, then the preset minimum ratio threshold will be used as the rate limit ratio.

[0054] A higher cumulative hazard index indicates that the current system has accumulated more dangerous energy that must be released or restricted, requiring a reduction in the pulling speed to release this energy. Therefore, a negative correlation mapping of the cumulative hazard index is needed to determine a risk limit ratio for subsequent adjustment of the pulling speed. It should be noted that the core physical reason for using a negative correlation mapping is that a higher cumulative hazard index indicates that the system is closer to the overshoot critical point, at which point a smaller risk limit ratio must be generated. Subsequently, this smaller risk limit ratio is used to modulate the pulling speed command of the pulling device through multiplication operations, thus forcibly reducing the target pulling speed output to the motor. This effectively releases the dangerous energy accumulated during the gap elimination stage, which is beneficial to improving the accuracy of subsequent mortar bond strength testing.

[0055] Under extremely high risk conditions, an excessively high cumulative risk index can cause the pull-out speed of the pull-out device to drop to zero, halting the strength testing process and preventing effective contact. Therefore, a minimum proportional threshold needs to be set to ensure that even under high risk conditions, the motor will not completely stop, but the system can still push the pull rod at a tiny creeping speed to eliminate the last bit of gap.

[0056] In one specific implementation of this invention, the preset minimum ratio threshold is set to 0.05, indicating that the minimum drawing speed is constrained to more than five percent of the standard drawing speed. The implementer may set other minimum ratio thresholds according to the specific implementation scenario, which will not be elaborated or limited here.

[0057] Preferably, in some possible implementations of the embodiments of the present invention, the method for obtaining the risk limit ratio includes: A risk comparison value is determined based on the ratio between the cumulative risk index at each sampling time and the preset maximum risk threshold; the difference between the positive integer 1 and the risk comparison value is used as the risk limit ratio.

[0058] Since a single cumulative hazard index can only reflect the magnitude of the hazard but cannot indicate the specific extent of the hazard, in order to accurately quantify the hazard progress at each sampling moment, this embodiment of the invention divides the cumulative hazard index by a preset maximum risk threshold to obtain a risk comparison value, which can map the abstract cumulative risk value into an intuitive hazard progress, providing a normalized decision-making benchmark for subsequent dynamic speed limits.

[0059] As explained above, the higher the cumulative risk index, the lower the pulling speed should be. Therefore, in order to obtain a risk limit ratio that can positively adjust the pulling speed, the positive integer 1 is subtracted from the risk comparison value to ensure that the subsequent limit on the pulling speed can conform to the laws of physics, that is, the greater the risk, the lower the speed. In one specific implementation of this invention, the preset maximum risk threshold can be obtained through experimental calibration. Specifically, before formally conducting mortar strength pull-out monitoring, the pull-out instrument is controlled to run continuously at its maximum instrument pull-out speed under no-load conditions. During this process, the cumulative risk index at each moment is calculated in real time according to the aforementioned cumulative risk index calculation method and recorded as the no-load risk index. When the no-load risk index reaches stability (for example, the rate of change of the no-load risk index at the first five consecutive sampling moments is less than 1%, and the first sampling moment within the five consecutive sampling moments is taken as the moment when the no-load risk index reaches stability), the no-load risk index at the time of stability is taken as the preset maximum risk threshold. It should be noted that the preset maximum risk threshold represents the physical limit of the pull-out equipment itself, ensuring that no matter how it is adjusted subsequently, it will not exceed the maximum instrument pull-out speed limit of the pull-out equipment itself. In this embodiment, the preset maximum risk threshold can be in the range of [3, 8], preferably set to 5, and can be set according to the specific implementation scenario. The larger the preset maximum risk threshold, the higher the physical limit of the pull-out equipment itself, and vice versa.

[0060] Preferably, in some possible implementations of the embodiments of the present invention, the method for determining the pull-out contact stage includes: The sampling moments when the corresponding tension is greater than the preset tension threshold (indicating that the rod has been stressed and initial contact has been established) and the corresponding nonlinear discrete index is less than the preset discrete threshold (indicating that the distribution of displacement and tension data has changed from clustered to ordered linear, the mechanical gap has been completely eliminated, and the system has entered a stable elastic deformation stage that conforms to Hooke's Law) are taken as instantaneous stable moments. In terms of time sequence, the number of consecutive instantaneous stable moments preceding each instantaneous stable moment is taken as the judgment number. Instantaneous stable moments with a corresponding judgment number greater than the preset judgment number threshold are taken as temporally stable moments. It should be noted that the judgment conditions for instantaneous stable moments are: the corresponding tension is less than the preset tension threshold (indicating that the rod or traction rope has not yet been fully stressed) or the corresponding nonlinear discrete index is greater than the preset discrete threshold (indicating that the distribution of displacement and tension data is in a clustered distribution, i.e., random, and the mechanical gap still exists). The pull-out contact phase at each time series stable moment is defined as a stable pull-out contact phase; the pull-out contact phase at all other sampling moments outside of the time series stable moments is defined as a dangerous pull-out contact phase.

[0061] Since the gap will not exist indefinitely, the formal strength testing stage begins once the gap is completely eliminated. Therefore, in order to remove all restrictions during the formal strength testing stage and complete the subsequent pull-out strength test normally, it is necessary to first determine which pull-out contact stage is currently in (the stable pull-out contact stage without gap and the dangerous pull-out contact stage with gap). This allows for adaptive switching of the control strategy between stages, which helps improve the accuracy of mortar bond strength testing.

[0062] During the gap period, the traction rope is not in complete contact with the specimen, resulting in a smaller tension and a larger nonlinear dispersion index. During the gapless period, the traction rope is in close contact with the specimen, resulting in a larger tension and a smaller nonlinear dispersion index. Therefore, this embodiment of the invention, by setting a preset tension threshold and a preset dispersion threshold, can accurately identify the instantaneous pull-out contact stage (i.e., whether it is an instantaneously stable moment) at each sampling time through threshold comparison. In a specific implementation of this embodiment, the preset tension threshold is set to 0.1 kN, and the preset dispersion threshold is set to 0.1. Implementers can set other threshold values ​​according to specific implementation scenarios, which are not limited here.

[0063] Since instantaneous data cannot accurately characterize the contact phase in the continuous tensile strength test, to ensure the accuracy of the results, the current instantaneous stable moment is only considered a stable tensile contact phase if all consecutive preset judgment threshold sampling moments before the current instantaneous stable moment are instantaneous stable moments; otherwise, the current sampling moment is considered to be in a dangerous tensile contact phase. The preset judgment number can be set to 50, and implementers can set other values ​​according to specific implementation scenarios, which are not limited here. It should be noted that if there are fewer than 50 historical sampling moments before the current sampling moment, the average of the tensile force and nonlinear dispersion index of all historical sampling moments is used to make up the difference.

[0064] In other specific implementations of this invention, to ensure the accuracy of the judgment results, each sampling moment is judged as a stable pull-out contact stage only if all tensile forces and nonlinear discrete indices at each sampling moment and the preset number of sampling moments prior to that moment meet the judgment conditions; otherwise, it is judged as being in a dangerous pull-out contact stage. The preset number of judgments can be set to 50, but implementers can set other values ​​according to specific implementation scenarios, which are not limited here.

[0065] Preferably, in some possible implementations of the embodiments of the present invention, the method for performing pull-out testing of mortar bond strength includes: If the mortar bond strength pull-out test is conducted at the standard pull-out rate, the mortar bond strength will be tested. If the mortar is in a dangerous pull-out contact stage, the product of the standard pull-out rate and the rate limit ratio shall be used as the actual pull-out rate, and the mortar bond strength pull-out test shall be conducted using the actual pull-out rate.

[0066] During the stable pull-out contact stage, only normal mortar bond strength testing is required, without limiting the pull-out speed. However, during the dangerous pull-out contact stage, the pull-out speed needs to be limited to prevent excessive overload at the moment of contact, which could lead to microscopic pre-damage at the brittle mortar interface and consequently, a lower measured bond strength value. By limiting the pull-out speed, the risk of accumulated kinetic energy can be proactively eliminated before contact occurs, significantly improving the accuracy and reliability of mortar bond strength testing and effectively avoiding the problem of a lower measured bond strength.

[0067] In one specific implementation of this invention, the standard drawing rate is the theoretical command speed calculated using a conventional PID force control algorithm (PID control algorithm), for example, 0.05 kN / s; wherein, the PID control algorithm is a technical means well known to those skilled in the art, and need not be described in detail here.

[0068] Based on the same inventive concept, the present invention also proposes a mortar bonding strength testing device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements any of the steps of the mortar bonding strength testing method described above.

[0069] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0070] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for testing the bonding strength of mortar, characterized in that, The method includes: The displacement, tensile force, and tensile force growth rate at each sampling moment were obtained during the pull-out test of mortar bond strength. Based on the coordinated changes between displacement and tension at each sampling time, the corresponding nonlinear discrete index is determined; based on the tension growth rate and nonlinear discrete index at each sampling time, the corresponding overshoot risk index is analyzed; the overshoot risk index at each sampling time is superimposed and analyzed to determine the corresponding cumulative risk index. Based on the magnitude of the cumulative danger index at each sampling time, the corresponding rate limit ratio is determined; based on the tensile force and the nonlinear discrete index at each sampling time, the corresponding pull-out contact stage is determined; and based on the pull-out contact stage and the rate limit ratio, the mortar bond strength pull-out test is performed.

2. The method for testing the bonding strength of mortar according to claim 1, characterized in that, The method for obtaining the nonlinear discrete index includes: Based on the numerical fluctuations of displacement and tension at each sampling time and a preset number of previous sampling times, a mechanical feature matrix is ​​constructed; the mechanical feature matrix is ​​solved to determine the main trend feature value and the non-correlated feature value; the main trend feature value is used as the denominator and the non-correlated feature value is used as the numerator, and the nonlinear discrete index at each sampling time is determined by ratio calculation.

3. The method for testing the bonding strength of mortar according to claim 2, characterized in that, The method for constructing the mechanical feature matrix includes: The covariance matrix between displacement and tension at each sampling time and a preset number of previous sampling times is used as the mechanical characteristic matrix.

4. The method for testing the bonding strength of mortar according to claim 1, characterized in that, The method for obtaining the overshoot risk index includes: The overshoot risk index at each sampling time is determined by multiplying the square of the pull force growth rate at each sampling time with the nonlinear discrete index.

5. The method for testing the bonding strength of mortar according to claim 1, characterized in that, The methods for obtaining the cumulative risk index include: The time interval between two adjacent sampling times is taken as the sampling period; the product of the overshoot risk index and the sampling period is taken as the periodic risk index at each sampling time. The cumulative risk index for each sampling moment is determined by summing the periodic risk indices of each sampling moment and all previous sampling moments.

6. The method for testing the bonding strength of mortar according to claim 1, characterized in that, The method for obtaining the rate limit ratio includes: By negatively mapping the cumulative risk index at each sampling time, the corresponding risk limit ratio is determined. If the risk limit ratio is greater than or equal to the preset minimum ratio threshold, then the risk limit ratio will be used as the rate limit ratio. If the risk limit ratio is less than the preset minimum ratio threshold, then the preset minimum ratio threshold will be used as the rate limit ratio.

7. The method for testing the bonding strength of mortar according to claim 6, characterized in that, The methods for obtaining the risk limit ratio include: A risk comparison value is determined based on the ratio between the cumulative risk index at each sampling time and the preset maximum risk threshold; the difference between the positive integer 1 and the risk comparison value is used as the risk limit ratio.

8. The method for testing the bonding strength of mortar according to claim 1, characterized in that, The method for determining the pull-out contact stage includes: The sampling time when the corresponding tensile force is greater than the preset tensile force threshold and the corresponding nonlinear discrete exponent is less than the preset discrete threshold is taken as the instantaneous stable time; in terms of time sequence, the number of consecutive instantaneous stable times before each instantaneous stable time is taken as the judgment number; the instantaneous stable time when the corresponding judgment number is greater than the preset judgment number threshold is taken as the temporal stable time. The pull-out contact phase at each time series stable moment is defined as a stable pull-out contact phase; the pull-out contact phase at all other sampling moments outside of the time series stable moments is defined as a dangerous pull-out contact phase.

9. The method for testing the bonding strength of mortar according to claim 8, characterized in that, The method for conducting pull-out tests on mortar bond strength includes: If the mortar bond strength pull-out test is conducted at the standard pull-out rate, the mortar bond strength will be tested. If the mortar is in a dangerous pull-out contact stage, the product of the standard pull-out rate and the rate limit ratio shall be used as the actual pull-out rate, and the mortar bond strength pull-out test shall be conducted using the actual pull-out rate.

10. A mortar bonding strength testing device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the mortar bonding strength testing method as described in any one of claims 1 to 9.

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