Paper bag paper strength detection method and system

Abstract

The invention discloses a paper bag paper strength detection method and system, and relates to the technical field of paper bag paper strength detection. The method comprises the following steps: after the paper bag paper is clamped stably, stretching the paper bag paper at a set standard stretching speed, collecting a force value borne by the paper bag paper in the stretching process and a corresponding displacement value, and generating a force-displacement curve of the paper bag paper; microcosmic fracture events of the paper bag paper are identified from the force-displacement curve, and a first displacement value and local dissipated energy of each microcosmic fracture event are calculated; and determining the strength value of the paper bag paper according to the first displacement value and the local dissipated energy. According to the paper bag paper strength detection method and system provided by the invention, the microscopic fracture behavior of the paper bag paper in the stretching process can be effectively identified, the strength value is determined based on the displacement and energy information of the microscopic fracture event, the problem that the detection result is inaccurate and unstable due to the fact that the fracture point is difficult to accurately judge in a traditional method is solved, and the detection accuracy is improved. And the reliability and the accuracy of paper strength detection of the paper bag are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of paper bag paper strength detection, in particular to a paper bag paper strength detection method and system. BACKGROUND

[0002] In modern industrial production, paper bag paper as an important packaging material, its strength performance is a key indicator to measure product quality. In order to ensure that the paper bag paper can withstand the expected load, its tensile strength, tear resistance and other mechanical properties must be strictly detected. Usually such detection will adopt standardized test method, through specific equipment to apply tensile force to paper bag paper sample until the sample breaks, and record the force-displacement curve, so as to calculate the corresponding strength value. However, with the enhancement of environmental awareness and the demand for cost control, papermaking enterprises begin to add a higher proportion of recycled pulp in paper bag paper raw materials, which brings new challenges to traditional strength detection.

[0003] For example, in some industrial production scenarios, in response to increasingly stringent environmental regulations and to reduce production costs, papermaking enterprises may gradually increase the proportion of recycled pulp in paper bag paper raw materials. Such adjustment is not a simple replacement of raw materials, which fundamentally changes the microstructure of paper. For example, the fibers in recycled pulp are usually shorter and more uneven than virgin wood pulp fibers, and may contain more impurities. The shortening and uneven distribution of fiber length make the finally produced paper bag paper have more micro-defects and weak areas in the internal structure, and its overall uniformity and consistency decrease.

[0004] When such paper bag paper sample containing a high proportion of recycled fibers is sent to the quality control laboratory for tensile strength test, its mechanical behavior will show significantly different characteristics from traditional paper. In the process of applying tensile force, the force-displacement curve no longer presents a clear, smooth single peak, but may appear multiple small, irregular fluctuation peaks, forming a "sawtooth" curve shape. The physical mechanism of this phenomenon is that due to the inhomogeneity of the internal structure of the paper, not all fiber bundles or regions reach their ultimate strength at the same time during the force process, but the weak fiber bundles or micro-defect regions inside will first undergo small-scale, gradual fracture or slip, and then the load is redistributed to other regions until a larger part of the structure fails. This progressive failure mode directly impacts the preset "fracture point judgment logic" in existing strength detection software. The traditional judgment logic usually determines the fracture point based on finding the maximum peak or a certain drop point on the force-displacement curve, and in the face of such "sawtooth" curve, the system may frequently misjudge a certain intermediate small fluctuation as the final fracture point, resulting in a large and irregular downward deviation and fluctuation of the detection result, making it difficult for quality control personnel to obtain stable and reliable strength data.

[0005] In view of the above problems, the prior art needs to be improved. SUMMARY

[0006] The paper bag paper strength detection method and system are disclosed to solve the technical problem that the existing paper bag paper strength detection method is unstable and unreliable when facing paper bags containing a high proportion of recycled fibers due to the "sawtooth" force-displacement curve.

[0007] The technical solution of the present application is as follows:

[0008] In the first aspect, the present application discloses a paper bag paper strength detection method, comprising the following steps:

[0009] After the paper bag paper is clamped firmly, the paper bag paper is stretched at a set standard stretching speed, the force value borne by the paper bag paper during stretching is collected, as well as the corresponding displacement value, and a force-displacement curve of the paper bag paper is generated;

[0010] The micro-fracture events of the paper bag paper are identified from the force-displacement curve, and the first displacement value and the local dissipated energy of each micro-fracture event are calculated;

[0011] According to the first displacement value and the local dissipated energy, the strength value of the paper bag paper is determined.

[0012] Through the technical solution, the present application can effectively identify the micro-fracture behavior of the paper bag paper during stretching, and determine the strength value based on the displacement and energy information of the micro-fracture events, thereby overcoming the problem that the traditional method is inaccurate and unstable when dealing with "sawtooth" force-displacement curve due to the difficulty in accurately determining the fracture point, and improving the reliability and accuracy of paper bag paper strength detection.

[0013] Further, according to the paper bag paper strength detection method, the step of determining the paper bag paper strength value according to the first displacement value and the local dissipated energy specifically comprises:

[0014] The local dissipated energy of all micro-fracture events is accumulated to generate a cumulative dissipated energy-displacement curve;

[0015] The slope change of the cumulative dissipated energy-displacement curve is monitored, and when the slope of one point on the cumulative dissipated energy-displacement curve exceeds a preset slope threshold, it is determined that the one point is a structural failure critical point of the paper bag paper;

[0016] The strength value of the paper bag paper is determined according to the force-displacement curve and the structural failure critical point;

[0017] According to the first displacement value corresponding to the one point and the force value decreasing trend after the one point on the force-displacement curve, it is determined whether the strength value of the paper bag paper is valid.

[0018] Through the technical scheme, the application identifies the structural failure critical point by introducing the cumulative dissipated energy-displacement curve and the slope change thereof, and further judges the effectiveness of the strength value, so that the overall structural failure moment of the paper bag paper can be more accurately captured, and misjudgment caused by the randomness of local microscopic fracture events is avoided, and the accuracy and reliability of the strength value determination are improved.

[0019] On the basis of the above, the application further proposes that after the paper bag paper is clamped and stabilized, the paper bag paper is stretched at a set standard stretching speed, the force value borne by the paper bag paper and the corresponding displacement value in the stretching process are collected, and the force-displacement curve of the paper bag paper is generated. The step after the step further comprises:

[0020] The force value sequence in the force-displacement curve is decomposed into multiple layers, and each layer includes a group of detail coefficients;

[0021] According to a preset rule, the detail coefficients in one layer are selected for reconstruction to obtain a reconstructed force value sequence; and the force-displacement curve is updated according to the reconstructed force value sequence to form a first force-displacement curve.

[0022] Through the technical scheme, the application can effectively filter out noise and irregular fluctuations in the curve by decomposing and reconstructing the force-displacement curve, so that the identification of microscopic fracture events is more clear and accurate, thereby providing a more reliable data basis for subsequent strength calculation, and further improving the anti-interference ability and precision of the detection method.

[0023] Further, the force-displacement curve involved in the steps of identifying the microscopic fracture events of the paper bag paper, calculating the first displacement value and the local dissipated energy of each microscopic fracture event, and the subsequent steps is: the first force-displacement curve updated according to the reconstructed force value sequence.

[0024] Through the technical scheme, the application clearly uses the first force-displacement curve that is reconstructed and updated in the subsequent steps, ensuring the data consistency and accuracy of the entire detection process, avoiding errors that may be introduced due to inconsistent data sources, and further improving the reliability of the detection result.

[0025] In some preferred embodiments, the step of identifying the microscopic fracture events of the paper bag paper from the force-displacement curve and calculating the local dissipated energy of each microscopic fracture event specifically comprises:

[0026] Calculating the first derivative of the force-displacement curve;

[0027] Identifying the critical point when the first derivative changes from positive to negative as the local peak value of the force-displacement curve, and identifying the critical point when the first derivative changes from negative to positive as the local valley value of the force-displacement curve.

[0028] identify a local peak on the force-displacement curve and a next adjacent local valley as a micro-cracking event of the paper bag paper;

[0029] According to the local peak and the local valley corresponding to each micro-cracking event, the local dissipated energy of each micro-cracking event is calculated by using the trapezoidal integration method.

[0030] Through the technical scheme, the application provides a specific and effective method to identify micro-cracking events and calculate the local dissipated energy thereof, the local peak and the valley of the force-displacement curve are accurately captured through the change of the first derivative, so as to accurately define the range of each micro-cracking event, and the trapezoidal integration method is used for energy calculation, thereby ensuring the accuracy and operability of micro-cracking event identification and energy calculation.

[0031] As an optional solution, the step of determining the strength value of the paper bag paper according to the force-displacement curve and the structural failure critical point specifically comprises:

[0032] finding a displacement point corresponding to the structural failure critical point on the force-displacement curve;

[0033] finding a first force value corresponding to the displacement point on the force-displacement curve;

[0034] determining the first force value as the strength value of the paper bag paper.

[0035] Through the technical scheme, the application provides a direct and clear strength value determination method, that is, the strength of the paper bag paper is directly determined through the corresponding force value of the structural failure critical point on the force-displacement curve, thereby simplifying the acquisition process of the strength value and improving the operation efficiency.

[0036] On the basis of the above, the application further provides that the step of determining whether the strength value of the paper bag paper is valid according to the first displacement value corresponding to the point and the force value decreasing trend after the point on the force-displacement curve specifically comprises:

[0037] obtaining the first displacement value corresponding to the point, and determining whether the first displacement value is within a preset displacement threshold;

[0038] obtaining the force value corresponding to the point and after the point on the force-displacement curve; determining whether the difference between the force value corresponding to the point and the minimum force value corresponding to a set displacement after the point reaches or exceeds a preset force threshold;

[0039] When the first displacement value is within the displacement threshold and the difference reaches or exceeds the preset force threshold, the strength value is determined as an invalid strength value.

[0040] By the technical scheme, the application introduces a double judgment mechanism for the effectiveness of the strength value, that is, the reliability of the strength value is evaluated in combination with the displacement threshold value and the force value descending trend, invalid strength values caused by local abnormal fluctuations or test errors can be effectively identified and excluded, and the accuracy and practicality of the detection result are further improved.

[0041] In an implementation manner, the step of determining the strength value of the paper bag paper according to the first displacement value and the local dissipated energy specifically comprises:

[0042] According to the first displacement value, an event displacement interval value of each micro fracture event relative to a previous micro fracture event is calculated;

[0043] According to the event displacement interval value and the local dissipated energy, an event displacement interval moving average value and an event energy moving average value in the force-displacement curve are calculated in real time;

[0044] When the event displacement interval moving average value in the force-displacement curve is lower than a preset event density threshold value for the first time, and the event energy moving average value is higher than a preset energy significance threshold value, it is determined that a displacement point corresponding to the current micro fracture event is a candidate failure critical point;

[0045] The force value corresponding to the candidate failure critical point and a subsequent first set displacement thereof on the force-displacement curve is searched;

[0046] According to the force value change trend corresponding to the candidate failure critical point and the subsequent first set displacement thereof, whether the candidate failure critical point is a first structure failure critical point is confirmed;

[0047] When the candidate failure critical point is the structure failure critical point, the strength value of the paper bag paper is determined according to the force-displacement curve and the first structure failure critical point.

[0048] The event displacement interval moving average value is an average value between the event displacement interval value of the current micro fracture event and the event displacement interval values of a set number of previous micro fracture events;

[0049] The event energy moving average value is an average value between the first local dissipated energy of the current micro fracture event and the first local dissipated energies of a set number of previous micro fracture events.

[0050] By the technical scheme, the application provides a strength determination method based on dynamic monitoring of micro fracture event density and energy change through moving average values, which can more sensitively capture the transition process of the internal structure of the paper bag paper from stability to failure, improves the accuracy and real-time performance of the identification of the structure failure critical point through the combination judgment of the event displacement interval moving average value and the event energy moving average value, and is especially suitable for identifying the gradual failure mode of complex materials.

[0051] Further, the step of determining whether the candidate failure critical point is the first structure failure critical point according to the force value change trend corresponding to the candidate failure critical point and the first set displacement after the candidate failure critical point specifically comprises:

[0052] determining whether a first difference between the force value corresponding to the candidate failure critical point and the minimum force value within the first set displacement after the candidate failure critical point on the force-displacement curve reaches or exceeds a preset first force threshold value;

[0053] When the first difference reaches or exceeds the preset first force threshold value, the candidate critical point is determined as the first structure failure critical point.

[0054] Through the technical solution, the application provides a clear judgment standard to determine whether the candidate failure critical point is a real structure failure critical point, and the threshold value of the force value drop amplitude is used for judgment, which effectively avoids misjudging local small fluctuations as structure failure, and further improves the accuracy and reliability of the failure critical point determination.

[0055] In a second aspect, the application also discloses a paper bag paper strength detection system, which comprises:

[0056] a generation module configured to generate a force-displacement curve of the paper bag paper by stretching the paper bag paper at a set standard stretching speed after the paper bag paper is clamped and stabilized, collecting force values and corresponding displacement values borne by the paper bag paper during the stretching process;

[0057] a calculation module configured to identify micro fracture events of the paper bag paper from the force-displacement curve, and calculate a first displacement value and a local dissipated energy of each micro fracture event;

[0058] a determination module configured to determine a strength value of the paper bag paper according to the first displacement value and the local dissipated energy.

[0059] Through the technical solution, the application provides a system for implementing the paper bag paper strength detection method, and the modular design can efficiently complete the generation of the force-displacement curve, the identification and energy calculation of the micro fracture events, and the determination of the final strength value, thereby providing hardware and software support for the quality control of the paper bag paper and realizing the automatic and standardized strength detection process.

[0060] Advantages

[0061] The paper bag strength testing method disclosed in this application involves clamping the paper bag securely and then stretching it at a set standard stretching speed. The method collects the force and corresponding displacement values ​​experienced by the paper bag during the stretching process, generating a force-displacement curve. Microscopic fracture events are identified from this curve, and the first displacement value and local dissipated energy for each fracture event are calculated. The strength value of the paper bag is determined based on these first displacement values ​​and local dissipated energy. This method effectively solves the problem in existing technologies where, when the paper bag raw material contains a high proportion of recycled pulp, the force-displacement curve exhibits a "sawtooth" shape, making it difficult for traditional strength testing methods to accurately determine the fracture point, resulting in unstable and unreliable test results. This application, by identifying microscopic fracture events in paper bags and calculating their local dissipated energy, can more precisely capture the progressive failure mode of paper bags during the stress process, avoiding misjudging local fluctuations as the final fracture point, thereby improving the accuracy and reliability of strength testing. It is especially suitable for strength assessment of paper bags containing complex microstructures, providing more stable and reliable technical support for quality control in the papermaking industry. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of a paper bag strength testing method provided in this application.

[0063] Figure 2 This is a schematic diagram of a paper bag strength testing system provided in this application.

[0064] Figure 2 In the diagram: 1 is the generation module; 2 is the calculation module; 3 is the determination module. Detailed Implementation

[0065] The technical solutions in this application will now be clearly and completely described in conjunction with the accompanying drawings.

[0066] See Figure 1 This application proposes a method for testing the strength of paper bags, comprising the following steps:

[0067] S10. After the paper bag is securely clamped, stretch the paper bag at the set standard stretching speed, collect the force value and the corresponding displacement value of the paper bag during the stretching process, and generate the force-displacement curve of the paper bag.

[0068] S20. Identify the micro-fracture events of the paper bag from the force-displacement curve, and calculate the first displacement value and local dissipation energy for each micro-fracture event.

[0069] S30. Determine the strength value of the paper bag based on the first displacement value and the local dissipated energy.

[0070] The paper bag paper strength detection method of the present application can more accurately capture the structural failure process of the paper bag paper by identifying the micro fracture events during the stretching process of the paper bag paper and combining the displacement and energy information of each event, thereby overcoming the limitations of traditional methods in dealing with complex force-displacement curves and providing stable and reliable strength detection results.

[0071] In order to better understand the paper bag paper strength detection method proposed in the present application, some key terms involved therein are first explained.

[0072] "Paper bag paper" refers to paper used to make paper bags, and its strength performance is a key indicator of product quality.

[0073] "Force-displacement curve" refers to the relationship curve between the force value and the corresponding displacement value of the paper bag paper recorded during the stretching test of the paper bag paper. This curve reflects the deformation and failure behavior of the paper bag paper under stress.

[0074] "Micro fracture event" refers to a small fluctuation in force or displacement value caused by local failure of internal fibers or structural units of the paper bag paper during the stretching process. These fluctuations are the cumulative performance before the macro fracture of the paper bag paper.

[0075] "First displacement value" refers to the displacement value associated with each micro fracture event, usually referring to the displacement at the time of the event.

[0076] "Local dissipated energy" refers to the energy absorbed and dissipated by the internal structure of the paper bag paper in each micro fracture event, which reflects the energy loss degree of the micro fracture event.

[0077] The paper bag paper strength detection method of the present application is based on the fine analysis of the force-displacement curve generated during the stretching process of the paper bag paper, the identification of micro fracture events, and the determination of the strength value of the paper bag paper by combining the displacement and energy information thereof.

[0078] Specifically, after the paper bag paper is clamped firmly, it needs to be stretched at a set standard stretching speed. For example, a universal material testing machine can be used to perform a stretching test on the paper bag paper sample. During the test, the force sensor and displacement sensor on the testing machine will collect the force value and corresponding displacement value of the paper bag paper in real time. These collected data points are then used to generate the force-displacement curve of the paper bag paper. As a preferred embodiment, the stretching speed can be set to 20 mm / min, and the recording is continued until the paper bag paper is completely broken.

[0079] Identifying the micro-rupture events of the paper sack paper from the force-displacement curve is one of the key steps of the present application. For example, the micro-rupture events can be identified by observing the local fluctuations on the force-displacement curve. When the force value shows a trend of first rising and then falling, it can be considered that a micro-rupture event has occurred. In order to quantify these events, it is necessary to calculate the first displacement value and the local dissipated energy of each micro-rupture event. The first displacement value can be the displacement corresponding to the occurrence of the micro-rupture event. The local dissipated energy can be calculated by integrating the force-displacement curve segment corresponding to the micro-rupture event, for example, using the trapezoidal integration method to calculate the area enclosed by the curve segment and the displacement axis.

[0080] The paper sack paper strength detection method of the present application stretches the paper sack paper at a set standard stretching speed after the paper sack paper is clamped firmly, and collects the force value and the corresponding displacement value borne by the paper sack paper during the stretching process, thereby generating a force-displacement curve of the paper sack paper. Subsequently, the micro-rupture events of the paper sack paper are identified from the force-displacement curve, and the first displacement value and the local dissipated energy of each micro-rupture event are calculated. Finally, the strength value of the paper sack paper is determined according to the first displacement value and the local dissipated energy.

[0081] The overall technical solution of the present application can effectively solve the problem of the traditional method in processing the "sawtooth" force-displacement curve by introducing the identification of micro-rupture events and the calculation of energy dissipation. By analyzing the displacement and energy information of each micro-rupture event, the present application can more accurately capture the real process of the progressive destruction of the internal structure of the paper sack paper. For example, when a weak fiber bundle or a micro-defect region inside the paper sack paper occurs small-scale rupture, a micro-rupture event will occur, accompanied by a certain energy dissipation. By accumulating the energy dissipation of these micro-rupture events, the overall structural integrity and carrying capacity of the paper sack paper can be more comprehensively evaluated. When the cumulative dissipated energy or its change trend reaches a certain critical point, it indicates that the macro-structure of the paper sack paper is about to fail, and the corresponding force value can more accurately reflect the real strength of the paper sack paper. This method avoids the dependence on a single peak value, thereby improving the stability and reliability of the strength detection result, and providing a more accurate quality control means for paper sack paper containing a high proportion of recycled fibers.

[0082] Compared with the prior art, the core innovation of the present application is that instead of only focusing on macroscopic breaking points, it goes deep into the microscopic level to identify every microscopic breaking event occurring in the paper bag paper during the stretching process. By calculating the first displacement value and the local dissipated energy of each microscopic breaking event, the present application can more finely capture the dynamic process of the progressive destruction of the internal structure of the paper bag paper. This method based on microscopic event analysis can effectively avoid misjudgment caused by curve fluctuations in traditional methods, thereby providing more stable and accurate strength detection results. For example, even if the force-displacement curve presents multiple small fluctuations, the present application can accurately identify the structural failure critical point of the paper bag paper by comprehensively analyzing the displacement and energy characteristics of these microscopic events, and then determine its true strength. Therefore, the present application significantly improves the accuracy and reliability of paper bag paper strength detection, and is especially suitable for quality assessment of paper bag paper containing complex microscopic structures.

[0083] The present application further proposes that the step of determining the paper bag paper strength value according to the first displacement value and the local dissipated energy specifically comprises:

[0084] accumulating the local dissipated energy of all microscopic breaking events to generate a cumulative dissipated energy-displacement curve;

[0085] monitoring the slope change of the cumulative dissipated energy-displacement curve, and when the slope of one point on the cumulative dissipated energy-displacement curve exceeds a preset slope threshold, determining that the one point is the structural failure critical point of the paper bag paper;

[0086] determining the strength value of the paper bag paper according to the force-displacement curve and the structural failure critical point;

[0087] determining whether the strength value of the paper bag paper is valid according to the first displacement value corresponding to the one point and the force value decreasing trend after the one point on the force-displacement curve.

[0088] Specifically, accumulating the local dissipated energy of all microscopic breaking events means sequentially accumulating the local dissipated energy calculated from each microscopic breaking event identified from the force-displacement curve. For example, starting from the first microscopic breaking event, its local dissipated energy can be taken as the initial cumulative value, and then the local dissipated energy of the subsequent microscopic breaking events can be sequentially added to the previous cumulative value, thereby forming a cumulative dissipated energy sequence varying with displacement during the entire stretching process. In this way, a cumulative dissipated energy-displacement curve reflecting the total energy dissipation of the paper bag paper during the stretching process can be generated. The purpose is to more comprehensively reflect the cumulative effect of internal damage of the material by accumulating energy, rather than only focusing on a single breaking event.

[0089] The slope of the cumulative dissipated energy-displacement curve is monitored, specifically, the slope of the generated cumulative dissipated energy-displacement curve is calculated in real time or in segments. When the slope of a certain point on the curve suddenly increases significantly and exceeds a preset slope threshold, it usually indicates that the damage accumulation rate inside the paper bag paper has accelerated sharply, indicating that the macrostructure of the material is about to or has already failed significantly. Therefore, the certain point is determined as the structural failure critical point of the paper bag paper. The slope threshold can be set according to the material properties, thickness and actual application requirements of different paper bag papers through experimental data or experience. The purpose is to provide an objective and quantitative standard to identify the key turning point from damage accumulation to structural failure of the paper bag paper.

[0090] In practical applications, the strength value of the paper bag paper is determined according to the force-displacement curve and the structural failure critical point, which means that after the structural failure critical point is identified, the force value corresponding to the critical point is found in combination with the original force-displacement curve, and the force value is taken as the strength value of the paper bag paper. This usually means that the force value represents the maximum bearing capacity of the paper bag paper before the macrostructure fails.

[0091] Further, according to the first displacement value corresponding to the certain point and the force value decrease trend after the certain point on the force-displacement curve, it is determined whether the strength value of the paper bag paper is valid, which aims to verify the determined strength value again to exclude false judgments caused by measurement errors, material defects or other abnormal situations. For example, if the displacement value corresponding to the structural failure critical point is too small or too large, or the force value does not show the expected significant decrease after the critical point, it may indicate that the strength value is not the true failure strength, and needs to be invalidated.

[0092] The scheme of the present application can comprehensively reflect the internal damage accumulation process of the paper bag paper during the stretching process by accumulating the local dissipated energy of all micro fracture events. By generating the cumulative dissipated energy-displacement curve, the energy evolution process of the material from elastic deformation to plastic deformation to final failure can be clearly observed. When the slope of the curve exceeds the preset threshold, it indicates that the dissipated energy per unit displacement increases sharply, which directly corresponds to the critical state of large-scale destruction or macro crack propagation of the internal structure of the paper bag paper, thereby the structural failure critical point of the paper bag paper can be more accurately identified. In addition, by judging the validity of the determined strength value, in combination with the displacement value corresponding to the structural failure critical point and the force value decrease trend after the critical point, false judgments caused by local defects, measurement noise or other atypical failure modes can be effectively excluded, and the determined strength value can truly and reliably reflect the overall strength performance of the paper bag paper.

[0093] By the technical solution, the paper bag paper strength detection method is more accurate and reliable. By introducing the cumulative dissipated energy-displacement curve and its slope monitoring, the limitations of the traditional method of relying only on the maximum force value or a single fracture event judgment can be overcome, the key turning point of the paper bag paper from damage accumulation to macroscopic structure failure can be more accurately captured, and the objectivity and accuracy of the structure failure critical point identification are improved. In addition, the mechanism for judging the effectiveness of the strength value further enhances the reliability of the detection result, avoids misjudgment caused by abnormal data or atypical failure mode, and makes the determined paper bag paper strength value more truly and comprehensively reflect the actual performance of the material, thereby providing a more solid data basis for paper bag paper quality control and performance evaluation.

[0094] The step of stretching the paper bag paper at a set standard stretching speed after the paper bag paper is clamped stably, collecting the force value borne by the paper bag paper and the corresponding displacement value in the stretching process, and generating the force-displacement curve of the paper bag paper further includes:

[0095] The force value sequence in the force-displacement curve is decomposed into multiple layers, and each layer includes a group of detail coefficients;

[0096] According to a preset rule, the detail coefficients in one layer are selected for reconstruction to obtain a reconstructed force value sequence; and the force-displacement curve is updated according to the reconstructed force value sequence to form a first force-displacement curve.

[0097] Specifically, the force value sequence refers to a set of force value data points extracted from the original force-displacement curve and arranged in time or displacement order. The multi-layer decomposition can be understood as a signal processing technology, which aims to decompose the original force value sequence into components of different frequencies or scales, such as through wavelet transform, empirical mode decomposition (EMD) or variational mode decomposition (VMD) method. Each layer of decomposition usually corresponds to the characteristics of the signal in a certain frequency range, and the detail coefficients represent the high-frequency or low-frequency information of the signal at different scales.

[0098] The preset rule is used to guide how to select from the decomposed multiple layers of detail coefficients. For example, the rule can be set according to the energy, variance, correlation or contribution degree of a certain frequency range of the detail coefficients. The purpose is to filter out the noise components in the original signal while retaining the effective information related to the microscopic fracture events of the paper bag paper. By selecting the detail coefficients in one or more layers for reconstruction, a denoised or smoothed reconstructed force value sequence can be obtained.

[0099] In practical applications, the reconstructed force value sequence is the processed, smoother and more accurate force value data, which can better reflect the real mechanical response of the sack paper during the stretching process. Updating the force-displacement curve according to the reconstructed force value sequence means replacing the original force value with the reconstructed force value, thereby forming a new and optimized first force-displacement curve. This first force-displacement curve will serve as the basis for subsequent identification of microscopic fracture events and calculation of related parameters.

[0100] The scheme of the present application effectively solves the noise problem existing in the original force-displacement curve by introducing the multi-layer decomposition and reconstruction steps of the force value sequence. Specifically, the multi-layer decomposition technology can separate the noise components (usually represented as high-frequency or specific scale details) in the original force value sequence from the mechanical response of the sack paper material itself (usually represented as low-frequency or different scale trends and events). By reconstructing according to the pre-set rules to select appropriate detail coefficients, noise can be filtered out while retaining or enhancing the effective signal characteristics related to microscopic fracture events. It is precisely due to this fine processing of the force value sequence that the subsequent identification of microscopic fracture events of the sack paper from the first force-displacement curve becomes more accurate and reliable, thereby providing a high-quality data basis for subsequent calculation of local dissipated energy, cumulative dissipated energy and determination of structural failure critical point.

[0101] Through the above technical scheme, the pre-processing of the original force-displacement curve can significantly improve the signal-to-noise ratio of the force-displacement curve, making the microscopic fracture characteristics in the curve more clear. This not only helps to more accurately identify the microscopic fracture events of the sack paper, reducing false positives or false negatives, but also improves the calculation accuracy of the first displacement value and local dissipated energy of each microscopic fracture event. Ultimately, this optimization can ensure that the determined strength value of the sack paper is more accurate and reliable, thereby improving the robustness and practicality of the entire strength detection method, especially when facing complex or noisy test environments.

[0102] In some preferred embodiments, the multi-layer decomposition can be implemented using wavelet decomposition techniques. Specifically, the collected force value sequence is input into a wavelet decomposition algorithm, and by selecting a suitable wavelet basis function (e.g. Daubechies wavelet, Symlets wavelet, etc.) and the number of decomposition layers, the original force value sequence is decomposed into a series of approximation coefficients and detail coefficients. Among them, the approximation coefficients represent the low-frequency components of the signal, while the detail coefficients represent the high-frequency components of the signal at different scales. In order to remove noise, according to a pre-set rule, for example, selecting a certain level of detail coefficients for threshold processing or directly discarding the detail coefficients of high-frequency noise levels, and then performing wavelet reconstruction on the remaining approximation coefficients and processed detail coefficients, thereby obtaining a smooth and denoised reconstructed force value sequence. For example, low-frequency approximation coefficients and part of the low-mid frequency detail coefficients can be retained, while high-frequency detail coefficients are filtered out, because high-frequency details are usually related to noise. In this way, the random fluctuations and burrs in the original force-displacement curve are effectively suppressed, and the true response of the internal structure changes of the paper bag paper is highlighted, thereby forming a clearer and more accurate first force-displacement curve, providing more reliable data input for subsequent analysis.

[0103] In some embodiments of the present application described above, by stretching the paper bag paper, the force value and the corresponding displacement value borne by the paper bag paper during the stretching process are collected, thereby generating a force-displacement curve of the paper bag paper. On this basis, it is necessary to identify the microscopic fracture events of the paper bag paper from the force-displacement curve, and calculate the first displacement value and the local dissipated energy of each microscopic fracture event. However, the originally collected force-displacement curve may contain a certain degree of noise or irregular fluctuations, which may lead to inaccurate identification of microscopic fracture events, and thus affect the accuracy of the subsequent calculation of the first displacement value and the local dissipated energy. If the above problem is not solved, it may reduce the reliability of the paper bag paper strength detection result.

[0104] In view of this, the present application further proposes that in the steps of identifying the microscopic fracture events of the paper bag paper from the force-displacement curve, calculating the first displacement value and the local dissipated energy of each microscopic fracture event, and all subsequent analysis steps involving the force-displacement curve, the force-displacement curve used should be the first force-displacement curve updated according to the reconstructed force value sequence, to ensure the accuracy and reliability of the analysis.

[0105] The force-displacement curve used in the steps of identifying the microscopic fracture events of the paper bag paper from the force-displacement curve, calculating the first displacement value and the local dissipated energy of each microscopic fracture event, and all subsequent steps is: the first force-displacement curve updated according to the reconstructed force value sequence.

[0106] Specifically, the above-mentioned step of identifying the micro-rupture events of the paper bag paper from the force-displacement curve, calculating the first displacement value and the local dissipated energy of each micro-rupture event, and all subsequent steps relying on the analysis of the force-displacement curve, all use the pre-processed and optimized first force-displacement curve. Among them, the first force-displacement curve is formed by decomposing the force value sequence in the originally collected force-displacement curve in multiple layers, reconstructing the detail coefficients in one layer according to the pre-set rules, obtaining the reconstructed force value sequence, and finally updating the original force-displacement curve. The purpose is to remove the noise and irregular fluctuations in the original data, making the curve smoother and more truly reflecting the mechanical response of the paper bag paper.

[0107] The scheme of the present application effectively avoids the interference of noise and random fluctuations in the original force-displacement curve on the analysis results by applying the first force-displacement curve updated by the reconstructed force value sequence to the identification of micro-rupture events and energy calculation. It is precisely because the quality of the force-displacement curve has been significantly improved that the local peak and valley of the micro-rupture event can be more accurately identified, thereby ensuring the calculation accuracy of the first displacement value and the local dissipated energy of each micro-rupture event. This processing method lays a solid data foundation for subsequent determination of the strength value of the paper bag paper.

[0108] In some preferred embodiments, it is assumed that during the stretching of the paper bag paper, due to the interference of the sensor or environmental factors, the originally collected force-displacement curve presents obvious burrs or high-frequency noise. If this original curve is directly used to identify micro-rupture events, these noises may be misidentified as micro-rupture events, or the characteristic points (such as local peaks and valleys) of the true micro-rupture events may be covered by noise, resulting in incorrect first displacement values and local dissipated energies. Through the scheme of the present application, the original force-displacement curve is first decomposed and reconstructed in multiple layers to generate a smooth and denoised first force-displacement curve. For example, wavelet decomposition and other methods can be used to remove or attenuate the detail coefficients corresponding to high-frequency noise, and then reconstruction is performed. Subsequently, when identifying micro-rupture events, the analysis is based on this optimized first force-displacement curve, at this time, the characteristic points of the micro-rupture events will be clearer, and the identification result will be more accurate. For example, a local peak that is originally blurred by noise will become sharp and easy to identify on the first force-displacement curve, thereby ensuring the accuracy of the subsequent strength value calculation.

[0109] In some embodiments of the present application described above, identifying the micro-rupture events of the paper bag paper from the force-displacement curve and calculating the local dissipated energy thereof is a key step in determining the strength value of the paper bag paper. Specifically, this identification and calculation process can be carried out in the following manner.

[0110] The step of identifying the micro-fracture events of the paper bag paper from the force-displacement curve and calculating the local dissipated energy of each micro-fracture event specifically comprises:

[0111] calculating the first derivative of the force-displacement curve;

[0112] identifying the critical point when the first derivative changes from positive to negative as the local peak value of the force-displacement curve,

[0113] identifying the critical point when the first derivative changes from negative to positive as the local valley value of the force-displacement curve;

[0114] identifying one local peak value and the next adjacent local valley value on the force-displacement curve as one micro-fracture event of the paper bag paper;

[0115] calculating the local dissipated energy of each micro-fracture event by using the trapezoidal integration method according to the local peak value and the local valley value corresponding to each micro-fracture event.

[0116] Specifically, during the stretching process of the paper bag paper, a series of micro-damages will occur in its internal structure, which are manifested as small fluctuations on the force-displacement curve in macroscopic view. In order to accurately capture these micro-fracture events, it is necessary to first perform mathematical processing on the collected force-displacement curve. Calculating the first derivative of the force-displacement curve can effectively reflect the rate of change of the force value with displacement. When the first derivative changes from positive to negative, it indicates that the force value reaches a local maximum, i.e., a local peak value is formed; conversely, when the first derivative changes from negative to positive, it indicates that the force value reaches a local minimum, i.e., a local valley value is formed. These local peak values and local valley values are characteristic points of micro-fracture events.

[0117] A micro-fracture event can be understood as an interval starting from a local peak value on the force-displacement curve and ending at the next adjacent local valley value. This interval represents the process of internal structural damage and energy release of the paper bag paper when it is subjected to load. The local dissipated energy refers to the energy dissipated by the internal structure of the paper bag paper due to damage in each micro-fracture event. In practical applications, this local dissipated energy can be calculated by integrating the force-displacement curve between the local peak value and the local valley value corresponding to each micro-fracture event. For example, the trapezoidal integration method can be used to approximate the curve in this interval as a series of trapezoids, and then the areas of these trapezoids are summed up to obtain the local dissipated energy of the micro-fracture event. The trapezoidal integration method is a commonly used numerical integration method, which is simple to calculate and has high precision, and is suitable for processing curves composed of discrete data points.

[0118] The scheme of the present application can accurately identify local peaks and local valleys in the force-displacement curve through first derivative analysis. These local peaks and local valleys are a direct manifestation of micro fracture events occurring during the stretching process of the paper bag paper. By defining a local peak and the next adjacent local valley as a micro fracture event, the starting and ending points of each micro damage can be clearly defined. Further, the local dissipated energy of each micro fracture event is calculated using the trapezoidal integration method, which can quantify the energy consumed by each micro damage. This method can divide the continuous stretching process into a series of discrete micro fracture events and perform energy analysis on each event, thereby providing refined data support for subsequent strength evaluation.

[0119] Through the above technical scheme, accurate identification and quantification of micro fracture events of paper bag paper can be achieved. Compared with only observing macroscopic fracture, the present scheme can capture the subtle damage of the internal structure of the paper bag paper during the stress process, thereby more comprehensively and accurately reflecting the toughness and damage accumulation process of the paper bag paper. By calculating the local dissipated energy of each micro fracture event, a more physically meaningful parameter can be provided for the strength evaluation of the paper bag paper, which helps to deeply understand the failure mechanism of the paper bag paper and improve the reliability and accuracy of the strength detection.

[0120] Further, the step of determining the strength value of the paper bag paper according to the force-displacement curve and the structural failure critical point specifically comprises:

[0121] finding a displacement point corresponding to the structural failure critical point on the force-displacement curve;

[0122] finding a first force value corresponding to the displacement point on the force-displacement curve;

[0123] determining the first force value as the strength value of the paper bag paper.

[0124] Specifically, finding a displacement point corresponding to the structural failure critical point on the force-displacement curve means locating the structural failure critical point determined by monitoring the slope change of the cumulative dissipated energy-displacement curve on the generated force-displacement curve. The structural failure critical point corresponds to a specific displacement value on the force-displacement curve, which is the displacement point. Finding a first force value corresponding to the displacement point on the force-displacement curve can be understood as once the displacement point corresponding to the structural failure critical point is determined, the force value exactly corresponding to the displacement point on the force-displacement curve is found. This force value is the maximum or critical load borne by the paper bag paper when reaching the structural failure critical point, which is defined as the first force value. Therefore, determining the first force value as the strength value of the paper bag paper aims to directly extract the force value of the paper bag paper at the structural failure critical point as its strength value, thereby providing a clear and objective strength evaluation standard.

[0125] The technical scheme of the present application realizes the accurate quantification of the paper bag paper strength value by associating the structural failure critical point with a specific force value on the force-displacement curve. The structural failure critical point is a sign that the internal structure of the paper bag paper begins to irreversibly and significantly damage or destabilize, while the force-displacement curve directly reflects the relationship between the force and deformation of the paper bag paper during the stretching process. Therefore, finding the displacement point corresponding to the structural failure critical point on the force-displacement curve can accurately lock the deformation state at which the paper bag paper begins to macroscopically fail. Subsequently, by finding the first force value corresponding to this displacement point, the maximum carrying capacity of the paper bag paper at the moment of failure can be directly obtained. Finally, determining this first force value as the strength value of the paper bag paper is based on the principle of material mechanics, i.e., the strength of a material is usually defined as the maximum stress or force it can withstand before failure.

[0126] Through the above technical scheme, the present application provides a clear and operable method for determining the strength value of paper bag paper. This method avoids the ambiguity or subjective judgment that may exist in traditional methods, and directly associates the structural failure critical point with a specific force value on the force-displacement curve, so that the strength value of the paper bag paper can be objectively and accurately extracted. Thus, the reliability and consistency of the strength detection results are ensured, providing a solid data foundation for the quality control and performance evaluation of paper bag paper.

[0127] The present application further provides a specific method for determining whether the strength value of the paper bag paper is valid according to the first displacement value corresponding to the above-mentioned one point and the force value decline trend after the above-mentioned one point on the force-displacement curve, in order to improve the accuracy and reliability of the strength value determination.

[0128] According to the above-mentioned paper bag paper strength detection method, the step of determining whether the strength value of the paper bag paper is valid according to the first displacement value corresponding to the above-mentioned one point and the force value decline trend after the above-mentioned one point on the force-displacement curve specifically includes:

[0129] Obtaining the first displacement value corresponding to the above-mentioned one point, and determining whether the first displacement value is within a preset displacement threshold;

[0130] Obtaining the force value corresponding to the above-mentioned one point and after it on the force-displacement curve; determining whether the difference between the force value corresponding to the above-mentioned one point and the minimum force value corresponding to a set displacement after the above-mentioned one point reaches or exceeds a preset force threshold;

[0131] When the first displacement value is within the displacement threshold and the difference reaches or exceeds the preset force threshold, the strength value is determined as an invalid strength value.

[0132] Specifically, the "one point" refers to a point on the cumulative dissipated energy-displacement curve where the slope exceeds a pre-set slope threshold value, and the "first displacement value" refers to the displacement value corresponding to the structural failure critical point. The "pre-set displacement threshold value" is a displacement range set according to the material properties of the paper bag paper and testing experience, used to determine whether the structural failure critical point occurs within a reasonable deformation range. If the displacement value corresponding to the structural failure critical point is too small or too large, it may indicate that the test process is abnormal or that the failure point is not representative.

[0133] The "one point and the force values corresponding thereto on the force-displacement curve" refer to a series of force value data continuously collected on the force-displacement curve starting from the structural failure critical point. The "set displacement" refers to a pre-set displacement interval extending backward from the displacement corresponding to the structural failure critical point. The "minimum force value" refers to the lowest force value recorded on the force-displacement curve within the set displacement interval. The "difference value" refers to the absolute difference between the force value corresponding to the structural failure critical point and the minimum force value within the set displacement, which reflects the magnitude of the force value drop after structural failure. The "pre-set force threshold value" is a critical value used to determine whether the force value drop is significant enough to confirm whether a true, macroscopic structural failure has occurred. When the "strength value" is determined to be "invalid strength value", it means that although a strength value has been calculated, it is considered unreliable or not representative because it does not meet the displacement and force value drop conditions, and should not be used as the final strength evaluation result of the paper bag paper.

[0134] The scheme of the present application verifies the effectiveness of the determined strength value by introducing a double judgment of the displacement value corresponding to the structural failure critical point and the descending trend of the force value after failure. Specifically, the first displacement value corresponding to one of the above points is obtained, and it is judged whether it is within the preset displacement threshold, aiming to ensure that the identified structural failure critical point occurs within the normal tensile failure interval of the paper bag paper. If the displacement value is too small, it may mean premature local failure or noise interference; if it is too large, it may indicate that the material has been deformed too much, and the "failure" at this time may not be representative. At the same time, by obtaining the force value corresponding to one of the above points and after it on the force-displacement curve, and judging whether the difference between the force value corresponding to one of the above points and the minimum force value corresponding to a set displacement after one of the above points reaches or exceeds the preset force threshold, aiming to evaluate the significance of structural failure. An effective structural failure is usually accompanied by a significant drop in force value. If the force value does not decrease significantly, i.e. the difference does not reach the preset force threshold, it may mean that a real macro-structural failure has not occurred, or the failure process is too gentle, and the determined strength value may not be representative. Through the joint judgment of the above two conditions, the reliability of the determined strength value can be more comprehensively and accurately evaluated.

[0135] Through the above technical scheme, the present application can effectively identify invalid strength values caused by test abnormalities, material properties or data noise, etc. By reasonably judging the displacement corresponding to the structural failure critical point and combining the significance evaluation of the force value drop after failure, the data points without representative are avoided to be misjudged as effective strength values. Thus, the accuracy and reliability of the paper bag paper strength detection result are significantly improved, providing a more solid data foundation for the quality control and performance evaluation of paper bag paper, thereby reducing the potential risks caused by misjudgment.

[0136] In some preferred embodiments, the following is illustrated by a specific example. Assume that in the detection of the tensile strength of a batch of paper bags, the cumulative dissipated energy-displacement curve is generated by accumulating the local dissipated energy of all micro-fracture events. The slope of the curve is monitored, and when the slope first exceeds the preset slope threshold at a displacement of 10 mm, the point is determined as the structural failure critical point of the paper bag. At this time, the first displacement value corresponding to the critical point is 10 mm. In order to verify the validity of the strength value, first, the first displacement value 10 mm is obtained, and it is determined whether it is within the preset displacement threshold (for example, 5 mm to 15 mm). Assuming that 10 mm is within the threshold, the first condition is met. Then, the force value within the set displacement (for example, from 10 mm to 12 mm) after the displacement of 10 mm on the force-displacement curve is obtained. Assuming that the force value corresponding to the displacement of 10 mm is 100 N, and the minimum force value within the interval from 10 mm to 12 mm is 80 N. At this time, the difference between the two is 20 N. The preset force threshold is set to 50 N. Since 20 N does not reach the preset force threshold of 50 N, it indicates that the force value does not decrease significantly enough. According to the above judgment, although the first displacement value is within the preset displacement threshold, the difference in the force value does not reach the preset force threshold, so the strength value obtained by this detection is determined as an invalid strength value. In this way, it can be avoided to misjudge this insignificant failure point as a valid strength value, thereby improving the reliability of the detection result.

[0137] The application further proposes that the step of determining the strength value of the paper bag according to the first displacement value and the local dissipated energy specifically comprises:

[0138] According to the first displacement value, the event displacement interval value of each micro-fracture event relative to the previous micro-fracture event is calculated;

[0139] According to the event displacement interval value and the local dissipated energy, the event displacement interval moving average value and the event energy moving average value in the force-displacement curve are calculated in real time;

[0140] When the event displacement interval moving average value in the force-displacement curve first falls below the preset event density threshold, and the event energy moving average value is higher than the preset energy significance threshold, the displacement point corresponding to the current micro-fracture event is determined as the candidate failure critical point;

[0141] The force value corresponding to the candidate failure critical point and the subsequent first set displacement is searched on the force-displacement curve;

[0142] According to the force value change trend corresponding to the candidate failure critical point and the subsequent first set displacement, it is confirmed whether the candidate failure critical point is the first structural failure critical point;

[0143] When the candidate failure threshold is the structural failure threshold, the strength value of the paper bag paper is determined according to the force-displacement curve and the first structural failure threshold.

[0144] The event displacement interval moving average value is an average value between the event displacement interval value of the current micro-cracking event and a set number of micro-cracking events before the current micro-cracking event.

[0145] The event energy moving average value is an average value between the first local dissipated energy of the current micro-cracking event and a set number of micro-cracking events before the current micro-cracking event.

[0146] Specifically, after the paper bag paper is stretched to generate a force-displacement curve, and micro-cracking events and corresponding first displacement values and local dissipated energies are identified, first, for each micro-cracking event, the event displacement interval value relative to the previous micro-cracking event is calculated. The event displacement interval value reflects the distance between adjacent micro-cracking events on the displacement axis, and can represent the frequency or density of micro-damage occurrence.

[0147] Further, based on the event displacement interval values and the local dissipated energies of each micro-cracking event, the system will calculate and monitor the event displacement interval moving average value and the event energy moving average value in the force-displacement curve in real time. The event displacement interval moving average value is an average value between the event displacement interval value of the current micro-cracking event and a set number of micro-cracking events before the current micro-cracking event, which provides a smooth index reflecting the recent micro-cracking event density. The event energy moving average value is an average value between the first local dissipated energy of the current micro-cracking event and a set number of micro-cracking events before the current micro-cracking event, which reflects the average level of dissipated energy of recent micro-cracking events. By using the moving average value, random fluctuations of individual events can be effectively filtered out, and the overall trend of paper bag paper damage accumulation can be more accurately captured.

[0148] When the event displacement interval moving average value in the force-displacement curve is first monitored to be lower than the preset event density threshold, it indicates that the occurrence of micro-cracking events becomes more frequent and dense, indicating the acceleration of internal damage of the material. At the same time, if the event energy moving average value is higher than the preset energy significant threshold, it indicates that these densely occurring micro-cracking events are accompanied by significant energy dissipation, further confirming that the material is experiencing severe structural damage. When the two conditions are met at the same time, the displacement point corresponding to the current micro-cracking event is preliminarily determined as the candidate failure threshold.

[0149] Subsequently, to further confirm the effectiveness of the candidate failure critical point, the system will search for the force values corresponding to the candidate failure critical point and the first set displacement after it on the force-displacement curve. By analyzing the trend of force values in this range, such as determining whether the force value has a significant drop, it can be confirmed whether the candidate failure critical point is the true first structural failure critical point. When it is confirmed that the candidate failure critical point is the structural failure critical point, the strength value of the paper bag paper is determined according to the force-displacement curve and the force value corresponding to the first structural failure critical point. For example, the force value corresponding to the first structural failure critical point can be taken as the strength value of the paper bag paper.

[0150] The scheme of the present application can dynamically and continuously evaluate the cumulative state of micro-damage of the paper bag paper during the stretching process by introducing event displacement interval moving average and event energy moving average. The traditional method may only focus on the peak value of force or the energy of a certain fixed point, while the present scheme comprehensively analyzes a series of micro-fracture events through moving average, thereby more comprehensively reflecting the damage evolution process of the material. When the event displacement interval moving average decreases, it indicates that micro-fracture events occur more and more densely, indicating that the internal structure of the material is accelerating to be destroyed; and the event energy moving average increases, which indicates that the energy dissipated by each micro-fracture event is larger, reflecting the severity of the damage. The combination of the two indicators makes the system more sensitive and accurate in capturing the critical transition point from elastic deformation to plastic deformation of the paper bag paper to the final structural failure. Through subsequent confirmation of the downward trend of the force value, the possibility of misjudgment is further ruled out, ensuring that the identified structural failure critical point is real and reliable, thereby improving the accuracy of the strength detection.

[0151] Through the above technical scheme, the present application can overcome the limitations of the traditional strength detection method in identifying the complex failure mechanism of the paper bag paper. The scheme can more accurately identify the structural failure critical point of the paper bag paper through dynamic monitoring and moving average analysis of micro-fracture events, avoiding misjudgment or omission caused by single threshold judgment. Therefore, the determined strength value of the paper bag paper has higher reliability and representativeness, and can more truly reflect the actual bearing capacity and damage resistance of the paper bag paper, providing a more scientific and effective method for quality control and performance evaluation of the paper bag paper.

[0152] In some preferred embodiments, the following is described by a specific example. It is assumed that a paper bag paper is subjected to a stretching test, and a force-displacement curve thereof is generated. During the stretching process, the system identifies a series of micro-fracture events and calculates the first displacement value and the local dissipated energy of each event.

[0153] For example, when the stretching proceeds to a certain stage, the system starts to calculate the event displacement interval moving average and the event energy moving average. Assume that the set number is 5 micro-fracture events. When the Nth micro-fracture event occurs, the system calculates the average of the event displacement interval values of the current event and the previous 4 events, and the average of the local dissipated energy of the current event and the previous 4 events.

[0154] With the continuation of the stretching, the internal damage of the paper sack paper intensifies, and the micro-fracture events become more and more intensive, resulting in a gradual decrease in the event displacement interval moving average. At the same time, as the severity of the damage increases, the energy dissipated by each micro-fracture event can also increase, causing the event energy moving average to gradually rise.

[0155] Assume that the event displacement interval moving average first falls below the preset event intensity threshold, and the event energy moving average simultaneously rises above the preset energy significance threshold, at a displacement of X millimeters. At this time, the system determines the point corresponding to the displacement X millimeters as a candidate failure critical point.

[0156] To confirm this point, the system further checks the force value trend within the first set displacement after the displacement X millimeters. If a significant drop in the force value in this range is found, the point corresponding to the displacement X millimeters is confirmed as the first structural failure critical point. Finally, the force value on the force-displacement curve corresponding to the first structural failure critical point is determined as the strength value of the paper sack paper. Through this dynamic monitoring and multi-index comprehensive judgment method, the real failure point of the paper sack paper can be more accurately captured.

[0157] The application further proposes that the step of confirming whether the candidate failure critical point is the first structural failure critical point according to the force value trend corresponding to the candidate failure critical point and the first set displacement after the candidate failure critical point specifically comprises:

[0158] determining whether a first difference between the force value corresponding to the candidate failure critical point and the minimum force value corresponding to the first set displacement after the candidate failure critical point on the force-displacement curve reaches or exceeds a preset first force threshold;

[0159] When the first difference reaches or exceeds the preset first force threshold, the candidate critical point is determined as the first structural failure critical point.

[0160] Specifically, the first set displacement refers to a preset displacement interval after the candidate failure critical point for observing the force value decline trend. The displacement interval can be set according to factors such as the material properties, thickness, and expected breaking behavior of the paper bag paper. The first difference refers to the difference between the force value corresponding to the candidate failure critical point and the minimum force value occurring within the first set displacement interval after the candidate failure critical point on the force-displacement curve. The difference reflects the magnitude of the decline in the carrying capacity of the paper bag paper after the candidate failure critical point occurs. The preset first force threshold is a preset force value used as a basis for judging whether the paper bag paper has undergone significant structural failure. The threshold can be determined according to experimental data, empirical values, or industry standards, and its purpose is to distinguish between minor force value fluctuations and actual structural damage.

[0161] The scheme of the present application provides a quantitative and objective judgment standard for confirming whether the candidate failure critical point is the first structural failure critical point by introducing the comparison between the first difference and the preset first force threshold. When the paper bag paper actually fails structurally, its carrying capacity will significantly decrease, which is manifested as a sharp decline in force value on the force-displacement curve. By calculating the first difference between the force value at the candidate failure critical point and the minimum force value within the subsequent first set displacement, and comparing it with the preset first force threshold, the significant force value decline can be effectively captured. If the first difference reaches or exceeds the preset first force threshold, it indicates that the internal structure of the paper bag paper has been irreversibly damaged, i.e., the first structural failure critical point has been reached. This judgment method based on quantitative indicators avoids the drawbacks of subjective judgment of force value trends, thereby improving the accuracy of failure critical point identification.

[0162] Through the above technical scheme, the present application can provide a more accurate and objective method to confirm the first structural failure critical point of the paper bag paper. By introducing the first difference and the preset first force threshold, the normal force value fluctuations and actual structural damage that occur during the stretching of the paper bag paper can be effectively distinguished, thereby avoiding misjudgment due to subjective judgment of force value trends. This enables the strength value of the paper bag paper to be more accurately determined, improving the reliability and consistency of the strength detection results, and having important practical significance for the quality control and performance evaluation of the paper bag paper.

[0163] In some preferred embodiments, the following is illustrated by a specific example. Assume that during the stretching of paper sack paper, a candidate failure critical point is identified at a displacement of XI by monitoring the event displacement interval moving average and the event energy moving average. At this time, the force value corresponding to the candidate failure critical point is F1. In order to confirm whether the candidate failure critical point is the first structural failure critical point, the system will continue to collect data and find the minimum force value Fmin on the force-displacement curve within the first set displacement (for example, 0.2 mm) after the candidate failure critical point. Then, the first difference value AF = F1-Fmin is calculated. If the preset first force threshold is set as AF_threshold, when the calculated AF reaches or exceeds AF_threshold, the system determines that the candidate failure critical point at the displacement XI is the first structural failure critical point of the paper sack paper. Conversely, if AF is less than AF_threshold, the candidate failure critical point may only be a local minor damage and is not confirmed as the first structural failure critical point, and the system will continue to monitor.

[0164] Referring to Figure 2 The specific embodiments of the present application also disclose a paper sack paper strength detection system, which comprises a generation module 1, a calculation module 2 and a determination module 3. The generation module 1 is used for stretching paper sack paper at a set standard stretching speed after the paper sack paper is clamped stably, collecting force values borne by the paper sack paper and corresponding displacement values in the stretching process, and generating a force-displacement curve of the paper sack paper. The calculation module 2 is used for identifying micro fracture events of the paper sack paper from the force-displacement curve and calculating first displacement values and local dissipated energies of each micro fracture event. The determination module 3 is used for determining a strength value of the paper sack paper according to the first displacement values and the local dissipated energies.

[0165] The system realizes accurate identification of micro fracture events and quantitative analysis of energy dissipation in the stretching process of paper sack paper in a modular manner, so as to overcome the limitations of traditional methods in processing complex force-displacement curves and provide stable and reliable strength detection results. Specifically, the generation module 1 is responsible for data collection and curve construction, the calculation module 2 deeply analyzes the curve to identify micro events and quantify the characteristics, and finally the determination module 3 comprehensively considers these information to obtain the strength value of the paper sack paper. This cooperative working mechanism ensures the comprehensiveness of the detection process and the accuracy of the results.

[0166] The specific steps and principles of the paper sack paper strength detection method have been described in the above embodiments and will not be repeated here. It is emphasized that the paper sack paper strength detection system proposed in the present application realizes the functions of these detection steps in a modular manner by means of hardware or software combination.

[0167] Specifically, the generating module 1 can be understood as a data acquisition and processing unit, which is responsible for receiving raw force and displacement data from the tensile testing equipment and integrating them into a force-displacement curve. For example, the generating module 1 can be an embedded controller connected to the force sensor and displacement sensor through an analog-to-digital converter (ADC) interface, reading data in real time and storing them in memory, and then connecting discrete data points into a curve through a software algorithm. As another implementation, the generating module 1 can also be a standalone computer program that interacts with the tensile testing machine through a standard communication interface (such as USB, Ethernet) to receive data and draw a force-displacement curve on a graphical user interface.

[0168] The computing module 2 is responsible for in-depth analysis of the force-displacement curve output by the generating module. Its purpose is to identify micro-fracture events in the curve and calculate the first displacement value and local dissipated energy of each event. For example, the computing module 2 can be a high-performance processor running a specific signal processing algorithm, such as a derivative-based analysis or wavelet transform algorithm, to identify local peaks and local valleys in the curve and thus define micro-fracture events. Subsequently, the module can perform numerical integration operations (such as the trapezoidal integration method) to calculate the local dissipated energy. In some embodiments, the computing module 2 can be a programmable logic controller (PLC) that performs real-time analysis and calculation of force-displacement data through a pre-set logic program.

[0169] The function of the determining module 3 is to determine the strength value of the paper bag paper according to the first displacement value and local dissipated energy output by the computing module. For example, the determining module 3 can be a decision support system with multiple strength determination models pre-set inside. The module receives analysis results from the computing module and outputs the final paper bag paper strength value according to these results combined with pre-set determination rules (such as cumulative energy threshold method, structure failure critical point identification method, etc.). As a preferred implementation, the determining module 3 can be an analysis unit based on machine learning algorithms, which learns the complex relationship between micro-fracture event characteristics and macro-strength by training on a large amount of historical data, thus more intelligently determining the strength value.

[0170] Compared with the prior art, the paper bag paper strength detection system of the present application has significant progress. The traditional strength detection method often relies on manual interpretation or simple peak identification algorithm to determine the breaking point, which is prone to misjudgment and instability of the results when facing the "sawtooth" force-displacement curve generated by the paper bag paper containing a high proportion of recycled fibers. The present application introduces a modular system design to decouple the complex processes of data generation, microscopic event calculation and strength determination, making each link more focused and efficient. For example, the generation module can ensure accurate collection of raw data and reliable construction of curves; the calculation module can finely identify and quantify microscopic breaking events, avoiding excessive dependence on a single macroscopic peak; the determination module can integrate multi-dimensional information to determine the true strength of the paper bag paper in a more scientific way. This systematic solution not only improves the degree of automation and efficiency of the detection process, but more importantly, it can effectively deal with the mechanical behavior of complex materials, providing stable, accurate and reliable strength detection results, thereby significantly improving the quality control level of paper bag paper.

[0171] The above only describes the embodiments of the present application and is not used to limit the protection scope of the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method of detecting the strength of paper for paper bags, characterized by, The method comprises the following steps: After the paper bag paper is clamped and stabilized, the paper bag paper is stretched at a set standard stretching speed, force values borne by the paper bag paper during the stretching process and corresponding displacement values are collected, and a force-displacement curve of the paper bag paper is generated; Microscopic fracture events of the paper bag paper are identified from the force-displacement curve, and a first displacement value and a local dissipated energy of each microscopic fracture event are calculated; The strength value of the paper bag paper is determined according to the first displacement value and the local dissipated energy.

2. The paper bag paper strength detection method according to claim 1, characterized by, The step of determining the strength value of the paper bag paper according to the first displacement value and the local dissipated energy specifically comprises: The local dissipated energies of all the microscopic fracture events are accumulated to generate a cumulative dissipated energy-displacement curve; The slope change of the cumulative dissipated energy-displacement curve is monitored, and when the slope of a point on the cumulative dissipated energy-displacement curve exceeds a preset slope threshold, the point is determined as a structural failure critical point of the paper bag paper; The strength value of the paper bag paper is determined according to the force-displacement curve and the structural failure critical point; Whether the strength value of the paper bag paper is valid is determined according to the first displacement value corresponding to the point and a force value descending trend after the point on the force-displacement curve.

3. The paper bag paper strength detection method according to claim 2, characterized by, The step of stretching the paper bag paper at a set standard stretching speed after the paper bag paper is clamped and stabilized, collecting force values borne by the paper bag paper during the stretching process and corresponding displacement values, and generating a force-displacement curve of the paper bag paper further comprises: The force value sequence in the force-displacement curve is decomposed into multiple layers, and each layer includes a group of detail coefficients; According to a preset rule, a detail coefficient in one of the layers is selected for reconstruction to obtain a reconstructed force value sequence; and the force-displacement curve is updated according to the reconstructed force value sequence to form a first force-displacement curve.

4. The paper bag paper strength detection method according to claim 3, characterized by, The force-displacement curve involved in the steps of identifying the microscopic fracture events of the paper bag paper from the force-displacement curve and calculating the first displacement value and the local dissipated energy of each microscopic fracture event, and subsequent steps is the first force-displacement curve updated according to the reconstructed force value sequence.

5. The paper sack paper strength detection method according to any one of claims 1 to 4, characterized by, The step of identifying the microscopic fracture events of the paper bag paper from the force-displacement curve and calculating the local dissipated energy of each microscopic fracture event specifically comprises: calculating the first derivative of the force-displacement curve; identifying a critical point at which the first derivative changes from positive to negative as a local peak value of the force-displacement curve, and identifying a critical point at which the first derivative changes from negative to positive as a local valley value of the force-displacement curve; identifying a local peak value and a next adjacent local valley value on the force-displacement curve as a microscopic fracture event of the paper bag paper; 6. The paper sack paper strength detection method according to any one of claims 2 to 4, characterized by, calculating the local dissipated energy of each microscopic fracture event by using the trapezoidal integration method according to the local peak value and the local valley value corresponding to each microscopic fracture event. The step of determining the strength value of the paper bag paper according to the force-displacement curve and the structural failure critical point specifically comprises: finding a displacement point corresponding to the structural failure critical point on the force-displacement curve; finding a first force value corresponding to the displacement point on the force-displacement curve; determining the first force value as the strength value of the paper bag paper.

7. The paper sack paper strength detection method according to any one of claims 2 to 4, characterized by, According to the first displacement value corresponding to the point and the force value drop trend after the point on the force-displacement curve, the step of determining whether the strength value of the paper bag paper is valid specifically comprises: Obtaining the first displacement value corresponding to the point, and judging whether the first displacement value is within a preset displacement threshold; Obtaining the force values corresponding to the point and the subsequent points on the force-displacement curve; judging whether the difference between the force value corresponding to the point and the minimum force value corresponding to the subsequent points within a set displacement is up to or exceeds a preset force threshold; When the first displacement value is within the displacement threshold, and the difference is up to or exceeds the preset force threshold, it is determined that the strength value is an invalid strength value.

8. The paper sack paper strength detection method according to claim 1, characterized by, According to the first displacement value and the local dissipated energy, the step of determining the strength value of the paper bag paper specifically comprises: According to the first displacement value, the event displacement interval value of each micro fracture event relative to the previous micro fracture event is calculated; and according to the event displacement interval value and the local dissipated energy, the event displacement interval sliding average value and the event energy sliding average value in the monitoring of the force-displacement curve are calculated in real time; When the event displacement interval sliding average value in the force-displacement curve is first lower than a preset event density threshold, and the event energy sliding average value is higher than a preset energy significant threshold, it is determined that the displacement point corresponding to the current micro fracture event is a candidate failure critical point; Looking up the force values corresponding to the candidate failure critical point and the subsequent first set displacement on the force-displacement curve; According to the force value change trend corresponding to the candidate failure critical point and the subsequent first set displacement, it is confirmed whether the candidate failure critical point is a first structure failure critical point; When the candidate failure critical point is a structure failure critical point, the strength value of the paper bag paper is determined according to the force-displacement curve and the first structure failure critical point.

9. The paper sack paper strength detection method according to claim 8, characterized by, According to the force value change trend corresponding to the candidate failure critical point and the subsequent first set displacement, it is confirmed whether the candidate failure critical point is a first structure failure critical point, and the step specifically comprises: Judging whether a first difference between the force value corresponding to the candidate failure critical point and the minimum force value corresponding to the first set displacement after the candidate failure critical point on the force-displacement curve is up to or exceeds a preset first force threshold; When the first difference is up to or exceeds the preset first force threshold, it is determined that the candidate critical point is a first structure failure critical point.

10. A paper sack paper strength detection system characterized by, The method comprises: A generating module is configured to generate a force-displacement curve of the paper bag paper after the paper bag paper is clamped and stabilized, by stretching the paper bag paper at a set standard stretching speed, collecting the force value borne by the paper bag paper and the corresponding displacement value during the stretching, and generating the force-displacement curve of the paper bag paper; A calculating module is configured to identify micro fracture events of the paper bag paper from the force-displacement curve, and calculate a first displacement value and a local dissipated energy of each micro fracture event; A determining module is configured to determine a strength value of the paper bag paper according to the first displacement value and the local dissipated energy.

Images