A corrugated cardboard strength detection method and system

Abstract

The present invention relates to the field of corrugated paper strength detection, and specifically to a corrugated paper strength detection method and system. The method first obtains stress data of the corrugated paper at each moment under different pressurization speed tests and a grayscale image of the corrugated side, analyzes the deformation of each corrugation in the grayscale image at each moment during each pressurization speed test, obtains the structural damage degree of the corrugated paper in each pressurization speed test, and extracts the stress peak value of the corrugated paper in each pressurization speed test, and then linearly fits the structural damage degree and stress peak value of each pressurization speed test to obtain the true flat compression strength of the corrugated paper. The present invention reduces the interference of the pressurization speed of the detection equipment on the flat compression strength test of the corrugated paper, and improves the accuracy of the flat compression strength test results of the corrugated paper.

Description

Technical Field

[0001] The invention relates to the field of corrugated paper strength detection, and in particular to a corrugated paperboard strength detection method and system. Background Art

[0002] Corrugated cardboard is a composite material consisting of a wavy paper core and a flat surface paper. It is widely used in the packaging industry due to its good mechanical properties and biodegradable and renewable environmentally friendly characteristics. The flat compression strength test is used to determine the compressive strength of corrugated cardboard when it is subjected to horizontal pressure during stacking and transportation. It is one of the key test contents for evaluating the production quality of corrugated cardboard.

[0003] In the related art, a compression tester and other equipment are usually used to perform a flat compression test on the corrugated cardboard. The deformation process of the corrugated cardboard under the action of external force is analyzed based on the stress and strain data in the test, and the maximum stress value before the corrugated cardboard is completely destroyed, that is, the stress peak value in the quasi-elastic stage, is used as the flat compression strength of the corrugated cardboard, thereby achieving the flat compression strength of the corrugated cardboard. However, during the flat compression test, the speed of the pressurization of the upper pressing plate of the compression equipment such as the compression tester will affect the mechanical behavior of the corrugated cardboard and the stability of the test. The faster the pressurization speed, the more rapid the strain response of the corrugated cardboard will be, which is more likely to cause local damage or premature fracture of the corrugated cardboard. At this time, directly using the stress peak as the flat compression strength may cause the stress peak to be low due to local deformation. At this time, it is not that there is a problem with the strength quality of the cardboard itself, but that the cardboard is destroyed due to the fast pressurization speed, so that the test results cannot accurately reflect the flat compression strength of the corrugated cardboard. As a result, when the existing method performs a flat compression strength test on the corrugated cardboard without considering the pressurization speed, the accuracy of the flat compression strength test result of the corrugated cardboard will be reduced. Summary of the invention

[0004] In order to solve the technical problem that the accuracy of the flat compression strength test results of corrugated cardboard is reduced when the existing method performs flat compression strength test on the corrugated cardboard without considering the pressure speed, the purpose of the present invention is to provide a corrugated cardboard strength test method and system, and the technical scheme adopted is as follows:

[0005] The present invention provides a method for detecting the strength of corrugated paperboard, the method comprising:

[0006] Obtain stress data of the corrugated paperboard at each moment under different pressurization speed tests and grayscale images of the corrugated side of the corrugated paperboard at each moment;

[0007] Taking any one of the pressurization speed tests as the target pressurization speed test, taking any time under the target pressurization speed test as the target time, obtaining the deformation coefficient of each corrugation in the grayscale image at the target time according to the morphological change of the same corrugation in the grayscale image between the target time and the initial time; clustering all the corrugations in the grayscale image at the target time according to the difference of the deformation coefficients of any two corrugations in the grayscale image at the target time, and obtaining the degree of outlier of each corrugation in the grayscale image at the target time;

[0008] According to the difference in the degree of outliers of each corrugation in the grayscale image between the target moment and the previous adjacent moment, the deviation gain coefficient of the corrugated board at the target moment is obtained; according to the deviation gain coefficient of the corrugated board at each moment and the degree of outliers of each corrugation in the grayscale image at each moment, the degree of structural damage of the target pressurization speed test is obtained;

[0009] The stress peak value of each pressurizing speed test is extracted from the stress data at all times under each pressurizing speed test; the structural damage degree and the stress peak value of each pressurizing speed test are linearly fitted to obtain the true flat compression strength of the corrugated board.

[0010] Furthermore, the deformation coefficient of each corrugation in the grayscale image obtained at the target time includes:

[0011] Perform edge detection on the grayscale image at each moment to obtain a wavy edge line in the grayscale image at each moment, and detect peak points and valley points from the wavy edge line, wherein each corrugation includes one peak point and two valley points;

[0012] On the wavy edge line in the grayscale image at each moment, the line between the peak point of each corrugation and the valley point on the right side of each corrugation is used as the deflection line segment of each corrugation, and the angle between the deflection line segment of each corrugation and the horizontal line is used as the deflection angle of each corrugation. The value range of the deflection angle is ;

[0013] According to the difference in length of the deflection line segment and the difference in the deflection angle of the same corrugation in the grayscale image between the target moment and the initial moment, the deformation coefficient of each corrugation in the grayscale image at the target moment is obtained.

[0014] Further, the deformation coefficient of each corrugation in the grayscale image at the target moment is obtained according to the difference in length of the deflection line segment and the difference in the deflection angle of the same corrugation in the grayscale image between the target moment and the initial moment, including:

[0015] Based on the calculation formula of the deformation coefficient, the deformation coefficient of each corrugation in the grayscale image at the target time is obtained. The calculation formula of the deformation coefficient is:

[0016] ;

[0017] in, The grayscale image at the target moment The deformation coefficient of each corrugation; The grayscale image at the target moment The length of the deflection line segment of each corrugation; Represents the grayscale image at the initial moment The length of the deflection line segment of each corrugation; The grayscale image at the target moment The deflection angle of each corrugation; Represents the grayscale image at the initial moment The deflection angle of each corrugation; Represents the normalization function.

[0018] Furthermore, the outlier degree of each corrugation in the grayscale image at the target moment is obtained, including:

[0019] Based on the calculation formula of the distance metric, the distance metric between any two corrugations in the grayscale image at the target moment is obtained. The calculation formula of the distance metric is:

[0020] ;

[0021] in, Represents the distance measure between any two corrugations in the grayscale image at the target moment; and The deflection angle of any two corrugations in the grayscale image representing the target time; and The deformation coefficients of any two corrugations in the grayscale image representing the target time;

[0022] Based on the distance metric between any two corrugations, clustering all the corrugations in the grayscale image at the target moment to obtain a plurality of clusters;

[0023] The cluster with the largest number of corrugations is used as a reference cluster, and the average value of the deflection angles of all the corrugations in the reference cluster is used as a reference deflection angle of the reference cluster; the average value of the deformation coefficients of all the corrugations in the reference cluster is used as a reference deformation coefficient of the reference cluster;

[0024] According to the difference between the deflection angle of each corrugation in the grayscale image at the target moment and the reference deflection angle, the difference between the deformation coefficient of each corrugation and the reference deformation coefficient, and the number of corrugations in the cluster where each corrugation is located, the outlier degree of each corrugation in the grayscale image at the target moment is obtained.

[0025] Furthermore, the outlier degree of each corrugation in the grayscale image at the target moment is obtained, including:

[0026] Based on the calculation formula of the outlier distance, the outlier distance of each corrugation in the grayscale image at the target time is obtained. The calculation formula of the outlier distance is:

[0027] ;

[0028] in, The grayscale image at the target moment The distance of the corrugation from the group; The grayscale image at the target moment The deflection angle of each corrugation; Represents the reference deviation angle of the reference cluster; The grayscale image at the target moment The deformation coefficient of each corrugation; represents the reference deformation coefficient of the reference cluster;

[0029] Taking the average of the outlier distances of all the corrugations in the grayscale image at the target moment as the overall outlier distance of the grayscale image at the target moment;

[0030] The outlier distance of each corrugation in the grayscale image at the target moment is taken as the numerator, the sum of the number of corrugations in the cluster where each corrugation in the grayscale image at the target moment is located and the overall outlier distance is taken as the denominator, and the comparison value is normalized to obtain the outlier degree of each corrugation in the grayscale image at the target moment.

[0031] Furthermore, the step of obtaining the deviation gain coefficient of the corrugated board at the target time includes:

[0032] Taking the average of the outlier degrees of all the corrugations in the grayscale image at each moment as the overall outlier degree of the grayscale image at each moment;

[0033] If the target time is the initial time, the deviation gain coefficient of the corrugated board at the target time is set to a value of 0;

[0034] If the target time is not the initial time, the deviation gain coefficient of the corrugated board at the target time is obtained based on the calculation formula of the deviation gain coefficient, and the calculation formula of the deviation gain coefficient is:

[0035] ;

[0036] in, represents the deviation gain coefficient of the corrugated board at the target time; Indicates the overall outlier degree of the grayscale image at the target moment; Indicates the overall outlier degree of the grayscale image at the previous moment adjacent to the target moment; Represents the maximum value function.

[0037] Further, obtaining the structural damage degree of the target pressurization speed test includes:

[0038] Based on the calculation formula of the structural damage degree, the structural damage degree of the target pressurization speed test is obtained, and the calculation formula of the structural damage degree is:

[0039] ;

[0040] in, Indicates the degree of structural damage for the target pressurization speed test; Indicates that corrugated cardboard is Deviation gain coefficient at each moment; Indicates The maximum value of the outlier degree of all the corrugations in the grayscale image at a moment; Indicates the number of all moments under the target pressurization speed test; Represents the normalization function.

[0041] Further, extracting the stress peak value of each pressurization speed test includes:

[0042] The maximum value of the stress data at all times under each pressurization speed test is taken as the stress peak value of each pressurization speed test.

[0043] Furthermore, obtaining the true flat compression strength of the corrugated paperboard includes:

[0044] The two-dimensional data points consisting of the structural damage degree and the stress peak value of each pressurization speed test are mapped into a coordinate system, wherein the horizontal axis of the coordinate system represents the structural damage degree and the vertical axis represents the stress peak value, and a linear function is constructed. ,in, Indicates The peak stress of the pressure velocity test, Indicates The degree of structural damage of the pressure velocity test, represents the first unknown parameter, represents the second unknown parameter;

[0045] The least square method is used in combination with the linear function to perform linear fitting on all two-dimensional data points in the coordinate system, and the value of the first unknown parameter in the linear function is calculated. The value of the first unknown parameter is used as the true flat compression strength of the corrugated board.

[0046] The present invention also proposes a corrugated cardboard strength detection system, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements any one of the steps of a corrugated cardboard strength detection method.

[0047] The present invention has the following beneficial effects:

[0048] The present invention takes into account that the accuracy of the flat compression strength test results of the corrugated cardboard will be reduced when the existing method performs a flat compression strength test on the corrugated cardboard without considering the pressure speed. First, the stress data of the corrugated cardboard at each moment under different pressure speed tests and the grayscale image of the corrugated side of the corrugated cardboard at each moment are obtained. Since the deformation of the corrugated cardboard is different under different pressure speed tests, at the same time, during the flat compression strength test, the various corrugated parts of the wavy paper core of the corrugated cardboard will undergo different morphological changes, and as the test proceeds, the morphological changes of the same corrugation at different moments are also different. Therefore, the deformation coefficient obtained can be used to reflect the degree of deformation of each corrugation of the corrugated cardboard at different moments. Considering that if local corrugations are destroyed prematurely during the flat compression test, the morphological difference between the destroyed corrugations and normal corrugations is large, all the corrugated cards in the grayscale image at the target moment are measured. The corrugations are clustered, and the degree of outlier is used to reflect the deformation difference between each corrugation and the normal corrugation at the target moment. Considering that if the corrugated board has local structural damage at a certain moment, the local damage position will cause the stress performance of the corrugated board to deteriorate, resulting in the deformation speed of each corrugation of the corrugated board being faster than that of the normal corrugated board, which in turn causes the degree of outlier of each corrugation of the corrugated board to increase with time. Therefore, the possibility of local structural damage of the corrugated board at the target moment can be reflected by the deviation gain coefficient, and the degree of structural damage can be used to reflect the degree of local structural damage of the corrugated board during the entire target pressurization speed test. Then, the structural damage degree and stress peak value of various pressurization speed tests are linearly fitted to obtain the true flat compression strength, thereby reducing the interference of the pressurization speed on the flat compression strength detection of the corrugated board and improving the accuracy of the flat compression strength detection results of the corrugated board. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0050] Figure 1 A flow chart of a corrugated paperboard strength detection method provided by one embodiment of the present invention;

[0051] Figure 2 A schematic diagram of a wavy edge line in a grayscale image of a corrugated cardboard provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0052] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of a corrugated cardboard strength detection method and system proposed by the present invention, its specific implementation, structure, features and effects, in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0053] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0054] The following is a detailed description of a corrugated board strength detection method and system provided by the present invention in conjunction with the accompanying drawings.

[0055] See also Figure 1 , which shows a flow chart of a corrugated paperboard strength detection method provided by an embodiment of the present invention, the method comprising:

[0056] Step S1: Obtain stress data of the corrugated paperboard at each moment under different pressurization speed tests and a grayscale image of the corrugated side of the corrugated paperboard at each moment.

[0057] The embodiment of the present invention takes a five-layer corrugated cardboard as an example. The five-layer corrugated cardboard consists of three layers of flat paper core and two layers of wavy paper core. Several corrugated cardboards are selected from all products in the same production batch as samples, and the sizes of the corrugated cardboards are ensured to be the same for subsequent tests at different pressurization speeds. An embodiment of the present invention uses a rectangular corrugated cardboard with a size of 100 mm × 25 mm for testing. The specific size of the corrugated cardboard can also be set by the implementer according to the specific real-time scenario, which is not limited here.

[0058] Then, different pressurization speeds are set for fixed platen compression testing equipment such as INSTRON universal material testing machine. In one embodiment of the present invention, the pressurization speed setting method is as follows: ,in, Indicates The corresponding pressurization speed of the fixed platen compression tester in the pressurization speed test, Indicates the preset standard pressurization speed, the value is set to 12.5mm / min, Indicates The preset adjustment multiples of the pressure speed test are as follows: , It represents the preset adjustment step, and its value is set to 1, wherein the specific values ​​of the preset standard pressurization speed, the preset adjustment multiple and the preset adjustment step can also be set by the implementer according to the specific implementation scenario, which is not limited here. In one embodiment of the present invention, a total of ten groups of tests are set, and the pressurization speeds of different tests are different. The number of test groups can be set by the implementer according to the specific implementation scenario, which is not limited here.

[0059] In each pressurization speed test process, firstly, a corrugated cardboard is placed in the central position of the lower press plate of the fixed press plate compression tester, and then the upper press plate of the compression tester is controlled to uniformly pressurize the corrugated cardboard until the corrugated cardboard is completely crushed, and then the stress data of the corrugated cardboard at each moment is collected in real time by the sensor on the fixed press plate compression tester, and the grayscale image of the corrugated side of the corrugated cardboard at each moment is collected in real time by a camera, wherein the time interval for collecting stress data and image data is the same, which is set to 0.1 second. The time interval for data collection can also be set by the implementer according to the specific implementation scenario, which is not limited here. At the same time, in each pressurization speed test process, the moment when the corrugated cardboard begins to contact the upper press plate and is subjected to stress is taken as the initial moment of each pressurization speed test.

[0060] It should be noted that, since the structure of the corrugated cardboard has been destroyed after each pressurization speed test, it is necessary to update the corrugated cardboard for testing when conducting the next pressurization speed test to ensure the accuracy of data collection.

[0061] Step S2: Take any one of the pressurization speed tests as the target pressurization speed test, and take any moment under the target pressurization speed test as the target moment. According to the morphological change of the same corrugation in the grayscale image between the target moment and the initial moment, obtain the deformation coefficient of each corrugation in the grayscale image at the target moment; according to the difference in the deformation coefficients of any two corrugations in the grayscale image at the target moment, cluster all the corrugations in the grayscale image at the target moment to obtain the outlier degree of each corrugation in the grayscale image at the target moment.

[0062] When the corrugated cardboard is subjected to uniform and small pressure, the deformation of the corrugated cardboard is elastic deformation. If the applied pressure is removed in the elastic deformation state, the cardboard will return to its original shape. However, if the pressure is large or the local structure of the cardboard is damaged prematurely due to the rapid pressure application speed, such as the bonding state of the corrugated bottom is damaged, then the corrugated cardboard will be quickly crushed, resulting in a low flat compression strength in the test result.

[0063] Since the deformation of the corrugated cardboard is different under different pressure speed tests, and at the same time, during the flat compression strength test of a certain specific pressure speed, the various corrugated parts of the wavy paper core of the corrugated cardboard will undergo different morphological changes, and as the test proceeds, the morphological changes of the same corrugation at different times are also different. Therefore, the embodiment of the present invention first analyzes any pressure speed test, takes any pressure speed test as the target pressure speed test, and then takes any moment under the target pressure speed test as the target moment. Since the initial moment is the moment when the corrugated cardboard and the upper pressing plate just start to contact, the corrugated cardboard at the initial moment has not undergone morphological changes. Therefore, the morphological changes of the same corrugation in the grayscale image between the target moment and the initial moment can be analyzed, and the deformation coefficient obtained reflects the degree of deformation of each corrugation of the corrugated cardboard at different times. Subsequently, based on the deformation coefficient, the possibility of local damage to the corrugated cardboard under the target pressure speed test can be analyzed, thereby reducing the interference of the pressure speed on the flat compression strength test of the corrugated cardboard.

[0064] Preferably, in one embodiment of the present invention, the method for obtaining the deformation coefficient of each corrugation in the grayscale image at the target time specifically includes:

[0065] First, edge detection is performed on the grayscale image at each moment to obtain the wavy edge line in the grayscale image at each moment. The existing Canny edge detection algorithm can be used to implement edge detection, which is not limited here. Then, the peak points and valley points are detected from the wavy edge line by manual labeling methods or by using related image processing tools such as Photoshop or ImageJ, where each corrugation contains a peak point and two valley points.

[0066] Then, on the wavy edge line in the grayscale image at each moment, the line between the peak point of each corrugation and the valley point on the right side of each corrugation is used as the deflection line segment of each corrugation, and the angle between the deflection line segment of each corrugation and the horizontal line is used as the deflection angle of each corrugation, where the value range of the deflection angle is , see Figure 2, which shows a schematic diagram of a wavy edge line in a grayscale image of a corrugated cardboard provided by an embodiment of the present invention, wherein E represents a corrugation on the wavy edge line, point X represents the peak point of the corrugation E, point Y represents the valley point on the right side of the corrugation E, the line segment between point X and point Y represents the deflection line segment of the corrugation E, and θ represents the deflection angle of the corrugation E.

[0067] The greater the difference in the length of the deflection line segment of the same corrugation in the grayscale image between the target moment and the initial moment, and the greater the difference in the deflection angle of the same corrugation, the greater the degree of deformation of the corrugation at the target moment. Therefore, the deformation coefficient of each corrugation in the grayscale image at the target moment can be obtained based on the difference in the length of the deflection line segment of the same corrugation in the grayscale image between the target moment and the initial moment and the difference in the deflection angle.

[0068] Preferably, in one embodiment of the present invention, the method for obtaining the deformation coefficient of each corrugation in the grayscale image at the target time further comprises:

[0069] Based on the calculation formula of the deformation coefficient, the deformation coefficient of each corrugation in the grayscale image at the target time is obtained. The calculation formula of the deformation coefficient is:

[0070] ;

[0071] in, The grayscale image at the target moment The deformation coefficient of each corrugation; The grayscale image at the target moment The length of the deflection line segment of each corrugation; Represents the grayscale image at the initial moment The length of the deflection line segment of each corrugation; The grayscale image at the target moment The deflection angle of each corrugation; Represents the grayscale image at the initial moment The deflection angle of each corrugation; Represents a normalization function. In one embodiment of the present invention, the normalization process may be specifically, for example, a maximum and minimum value normalization process, and the normalization in subsequent steps may adopt the maximum and minimum value normalization process. In other embodiments of the present invention, other normalization methods may be selected according to a specific range of numerical values, which will not be described in detail.

[0072] It should be noted that, at the initial moment, since the corrugated paperboard has not been deformed by pressure at the initial moment, the deformation coefficient of each corrugation in the grayscale image at the initial moment can be set to a value of 0.

[0073] During the target pressurizing speed test, under the ideal condition that the local structure of the corrugated cardboard is not damaged prematurely, as the test progresses until the corrugated cardboard is crushed, at a certain moment, the deformation of each corrugation of the corrugated cardboard is relatively similar, that is, the deformation coefficients of each corrugation are relatively similar, and due to the factor of pressurizing speed, the corrugated cardboard suffers premature local corrugated structure damage. At this moment, there is a difference in the deformation between the corrugated cardboard with local damage and the normal corrugation without damage, that is, the difference in the deformation coefficients of each corrugation is relatively large. Therefore, according to the difference in the deformation coefficients of any two corrugations in the grayscale image at the target moment, all the corrugations in the grayscale image at the target moment can be clustered to obtain the outlier degree of each corrugation in the grayscale image at the target moment. The outlier degree reflects the deformation difference between each corrugation of the corrugated cardboard and the normal corrugation at the target moment. Subsequently, the degree of local structural damage of the corrugated cardboard under the target pressurizing speed test can be accurately analyzed based on the outlier degree.

[0074] Preferably, in one embodiment of the present invention, the method for obtaining the outlier degree of each corrugation in the grayscale image at the target moment specifically includes:

[0075] In the subsequent clustering process, the deformation difference between the corrugations can be measured based on the difference in deformation coefficients between the corrugations and the difference in deflection angles. Therefore, the distance measurement between any two corrugations in the grayscale image at the target moment can be obtained based on the calculation formula of the distance measurement. The calculation formula of the distance measurement is:

[0076] ;

[0077] in, Represents the distance measure between any two corrugations in the grayscale image at the target moment; and Represents the deflection angle of any two corrugations in the grayscale image at the target moment; and Represents the deformation coefficient of any two corrugations in the grayscale image at the target time.

[0078] Based on the distance measurement between any two corrugations, all the corrugations in the grayscale image at the target moment are clustered to obtain multiple clusters, wherein the existing K-means clustering algorithm can be used to implement the clustering operation, and the number of clusters can be determined by the existing elbow method, which is not limited or elaborated here.

[0079] When the corrugated structure of the corrugated cardboard is partially damaged at the target time, the locally damaged corrugations only account for a minority, while the normal corrugations that are not damaged account for the majority. Therefore, for clusters with more corrugations, the corrugations contained therein are more likely to be normal and undamaged corrugations. Therefore, the cluster with the largest number of corrugations can be used as the reference cluster, and the average value of the deflection angles of all the corrugations in the reference cluster is used as the reference deflection angle of the reference cluster; the average value of the deformation coefficients of all the corrugations in the reference cluster is used as the reference deformation coefficient of the reference cluster, wherein the reference deflection angle and the reference deformation coefficient can be considered as the overall deflection angle and deformation coefficient of each undamaged corrugation. Subsequently, the deflection angle of each corrugation can be compared with the reference deflection angle, and the deformation coefficient of each corrugation can be compared with the reference deformation coefficient, and the degree of outlier of each corrugation in the grayscale image at the target time can be calculated and analyzed.

[0080] In the grayscale image at the target moment, the greater the difference between the deflection angle of a certain corrugation and the reference deflection angle, the greater the difference between the deformation coefficient of a certain corrugation and the reference deformation coefficient, and the fewer the number of corrugations in the cluster where a certain corrugation is located, the greater the deformation difference of the corrugation relative to the normal corrugation, and then the more likely the corrugation is to be damaged. Therefore, the outlier degree of each corrugation in the grayscale image at the target moment can be obtained based on the difference between the deflection angle of each corrugation in the grayscale image at the target moment and the reference deflection angle, the difference between the deformation coefficient of each corrugation and the reference deformation coefficient, and the number of corrugations in the cluster where each corrugation is located.

[0081] Preferably, in one embodiment of the present invention, the method for obtaining the outlier degree of each corrugation in the grayscale image at the target moment further comprises:

[0082] First, based on the calculation formula of the outlier distance, the outlier distance of each corrugation in the grayscale image at the target moment is obtained. The calculation formula of the outlier distance is:

[0083] ;

[0084] in, The grayscale image at the target moment The distance of the corrugation from the group; The grayscale image at the target moment The deflection angle of each corrugation; Represents the reference deviation angle of the reference cluster; The grayscale image at the target moment The deformation coefficient of each corrugation; represents the reference deformation coefficient of the reference cluster;

[0085] The average value of the outlier distances of all the corrugations in the grayscale image at the target moment is taken as the overall outlier distance of the grayscale image at the target moment, and the overall outlier distance reflects the overall level of the outlier distances of all the corrugations in the grayscale image at the target moment.

[0086] The larger the outlier distance of a corrugation in the grayscale image at the target time is relative to the overall outlier distance, and the fewer the number of corrugations in the cluster where the corrugation is located, the more likely the deformation of the corrugation is abnormal, and the more likely the corrugation is to be a locally damaged corrugation. Therefore, the outlier distance of each corrugation in the grayscale image at the target time can be used as the numerator, and the sum of the number of corrugations in the cluster where each corrugation in the grayscale image at the target time and the overall outlier distance can be used as the denominator, and the comparison value can be normalized, and the calculation result can be limited to range, thereby obtaining the outlier degree of each corrugation in the grayscale image at the target moment.

[0087] As an example, in one embodiment of the present invention, the expression of the outlier degree of each corrugation in the grayscale image at the target time can be specifically, for example, as follows:

[0088] ;

[0089] in, The grayscale image at the target moment The degree of outliers of each corrugation; The grayscale image at the target moment The distance of the corrugation from the group; The grayscale image at the target moment The number of corrugations in the cluster where the corrugation belongs; represents the overall outlier distance of the grayscale image at the target moment; Represents the normalization function.

[0090] The outlier degree of each corrugation in the grayscale image at each moment can be obtained by the same method as above.

[0091] Step S3: According to the difference in the degree of outliers of each corrugation in the grayscale image between the target moment and the previous adjacent moment, the deviation gain coefficient of the corrugated board at the target moment is obtained; according to the deviation gain coefficient of the corrugated board at each moment and the degree of outliers of each corrugation in the grayscale image at each moment, the degree of structural damage of the target pressurization speed test is obtained.

[0092] If local corrugated structure damage occurs to the corrugated cardboard at a certain moment during the target pressurization speed test, the local damage position will cause the stress-bearing performance of the corrugated cardboard to deteriorate, resulting in the deformation speed of each corrugation of the corrugated cardboard being faster than that of the normal corrugated cardboard, which in turn causes the degree of outliers of each corrugation of the corrugated cardboard to increase with time. Therefore, the difference in the degree of outliers of each corrugation in the grayscale image between the target moment and the adjacent previous moment can be analyzed, and the possibility of local structural damage to the corrugated cardboard at the target moment can be reflected by the obtained deviation gain coefficient. Subsequently, based on the deviation gain coefficient, the degree of premature local corrugated structure damage of the corrugated cardboard during the target pressurization speed test can be calculated and analyzed.

[0093] Preferably, in one embodiment of the present invention, the method for obtaining the deviation gain coefficient of the corrugated board at the target time specifically includes:

[0094] First, the average value of the outlier degree of all the corrugations in the grayscale image at each moment is taken as the overall outlier degree of the grayscale image at each moment, and the overall outlier degree reflects the overall level of the outlier degree of all the corrugations in the grayscale image at each moment.

[0095] If the target time is the initial time, there is no adjacent previous time at the target time. Since the corrugated cardboard has not been subjected to flat pressure at the initial time, the corrugated cardboard has not been partially damaged at the initial time. Therefore, the deviation gain coefficient of the corrugated cardboard at the target time can be directly set to a value of 0.

[0096] If the target time is not the initial time, the deviation gain coefficient of the corrugated cardboard at the target time is obtained based on the calculation formula of the deviation gain coefficient. The calculation formula of the deviation gain coefficient is:

[0097] ;

[0098] in, represents the deviation gain coefficient of the corrugated board at the target time; Indicates the overall outlier degree of the grayscale image at the target moment; Indicates the overall outlier degree of the grayscale image at the previous moment adjacent to the target moment; Represents the maximum value function.

[0099] Among them, when , indicating that the overall outlier degree at the target moment is increasing relative to the previous moment, which further indicates that the corrugated cardboard is more likely to have local structural damage at the target moment, and The larger the value, the greater the possibility of local structural damage. When , it means that the overall outlier degree at the target time is stable or even decreasing relative to the previous time, indicating that the corrugated cardboard has no local structural damage at the target time, so it can be directly Assign the value 0.

[0100] The deviation gain coefficient of the corrugated cardboard at each moment can be obtained by the same method as mentioned above. The larger the deviation gain coefficient of the corrugated cardboard at each moment, and the greater the degree of outlier of each corrugation in the grayscale image at each moment, the more likely the corrugated cardboard is to have local structural damage at each moment and the more obvious the damaged structure is. Therefore, the degree of structural damage in the target pressurization speed test can be obtained based on the deviation gain coefficient of the corrugated cardboard at each moment and the degree of outlier of each corrugation in the grayscale image at each moment. The degree of structural damage can be used to reflect the degree of local structural damage of the corrugated cardboard during the entire target pressurization speed test. Subsequently, the structural damage degree and stress data under each pressurization speed test can be combined to reduce the interference of the pressurization speed on the flat compression strength detection of the corrugated cardboard.

[0101] Preferably, in one embodiment of the present invention, the method for obtaining the degree of structural damage in the target pressurization speed test specifically includes:

[0102] Based on the calculation formula of the structural damage degree, the structural damage degree of the target pressurization speed test is obtained. The calculation formula of the structural damage degree is:

[0103] ;

[0104] in, Indicates the degree of structural damage for the target pressurization speed test; Indicates that corrugated cardboard is Deviation gain coefficient at each moment; Indicates The maximum value of the outlier degree of all the corrugations in the grayscale image at a moment; Represents the number of all moments under the target pressurization speed test.

[0105] Among them, the deviation gain coefficient at a certain moment The greater the degree of outlier of the corrugated board, the more abnormal the corrugated board is at that moment. Since local damage will gradually affect the originally intact corrugated boards, the earlier the deviation occurs, the greater the impact on the result. The degree of structural damage in the target pressure speed test is The bigger it is.

[0106] The structural damage degree of each pressurization speed test can be obtained by the same method as above.

[0107] Step S4: extracting the stress peak value of each pressurizing speed test from the stress data at all times under each pressurizing speed test; performing linear fitting on the structural damage degree and stress peak value of each pressurizing speed test to obtain the true flat compressive strength of the corrugated board.

[0108] After the corrugated cardboard is subjected to a flat compression test, the existing method usually takes the maximum stress value before the corrugated cardboard is completely destroyed, that is, the stress peak value in the quasi-elastic stage, as the flat compression strength of the corrugated cardboard. Therefore, the embodiment of the present invention needs to extract the stress peak value of each pressurization speed test from the stress data at all times under each pressurization speed test. Subsequently, based on the structural damage degree and stress peak value of various pressurization speed tests, the real flat compression strength of the corrugated cardboard after eliminating the interference factor of the pressurization speed can be calculated and analyzed, thereby improving the accuracy of the flat compression strength detection of the corrugated cardboard.

[0109] Preferably, in one embodiment of the present invention, the maximum value of stress data at all times under each pressurization speed test is taken as the stress peak value of each pressurization speed test.

[0110] When the compression strength test is performed in the embodiment of the present invention, the selected corrugated cardboards are from the same production batch. Therefore, in theory, the compression strengths of the corrugated cardboards used in the test are the same. However, in actual tests, the pressure speed of the equipment used in the test may cause premature local structural damage to the corrugated cardboard, resulting in a smaller stress peak value of the corrugated cardboard obtained in the actual test, that is, a smaller compression strength. In addition, the degree of structural damage and the peak stress value of each pressure speed test present a linear relationship. Therefore, the embodiment of the present invention obtains the true compression strength of the corrugated cardboard by linearly fitting the degree of structural damage and the peak stress value of each pressure speed test, thereby improving the accuracy of the compression strength detection of the corrugated cardboard.

[0111] Preferably, in one embodiment of the present invention, the method for obtaining the true flat compressive strength of the corrugated paperboard specifically includes:

[0112] First, the two-dimensional data points consisting of the degree of structural damage and the stress peak value of each pressurization speed test are mapped to the coordinate system, where the horizontal axis of the coordinate system represents the degree of structural damage and the vertical axis represents the stress peak value. Since the actual detected stress peak value is smaller than the stress peak value of the corrugated cardboard itself, and the greater the degree of structural damage of each pressurization speed test, the greater the degree of smaller the actual tested stress peak value, so a linear function can be constructed. ,in, Indicates The peak stress of the pressure velocity test, Indicates The degree of structural damage of the pressure velocity test, represents the first unknown parameter, represents the second unknown parameter, where It can also be considered as the true flat compressive strength of the corrugated board itself, and its value can be determined in the subsequent fitting process.

[0113] Then, the least squares method is used in combination with the linear function to perform linear fitting on all two-dimensional data points in the coordinate system, and the value of the first unknown parameter in the linear function is calculated, and the value of the first unknown parameter is used as the true flat compression strength of the corrugated board.

[0114] Through the above process, a flat compression strength that is closer to the corrugated cardboard itself is obtained, and the obtained actual flat compression strength can be used to evaluate the quality of the corrugated cardboard in the production batch. For example, the actual flat compression strength can be compared with the qualified flat compression strength range required by production. If the actual flat compression strength is within the qualified flat compression strength range, the quality is considered to be qualified, otherwise the quality is considered to be unqualified.

[0115] An embodiment of the present invention provides a corrugated cardboard strength detection system, which includes a memory, a processor and a computer program, wherein the memory is used to store the corresponding computer program, and the processor is used to run the corresponding computer program. When the computer program runs in the processor, the method described in steps S1 to S4 can be implemented.

[0116] It should be noted that the sequence of the above embodiments of the present invention is only for description and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0117] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

Claims

1. A corrugated cardboard strength testing method, characterized in that: The method comprises: Obtain stress data of the corrugated paperboard at each moment under different pressurization speed tests and grayscale images of the corrugated side of the corrugated paperboard at each moment; Taking any one of the pressurization speed tests as the target pressurization speed test, taking any time under the target pressurization speed test as the target time, obtaining the deformation coefficient of each corrugation in the grayscale image at the target time according to the morphological change of the same corrugation in the grayscale image between the target time and the initial time; clustering all the corrugations in the grayscale image at the target time according to the difference of the deformation coefficients of any two corrugations in the grayscale image at the target time, and obtaining the degree of outlier of each corrugation in the grayscale image at the target time; According to the difference in the degree of outliers of each corrugation in the grayscale image between the target moment and the previous adjacent moment, the deviation gain coefficient of the corrugated board at the target moment is obtained; according to the deviation gain coefficient of the corrugated board at each moment and the degree of outliers of each corrugation in the grayscale image at each moment, the degree of structural damage of the target pressurization speed test is obtained; Extracting the stress peak value of each pressurizing speed test from the stress data at all times under each pressurizing speed test; performing linear fitting on the structural damage degree and the stress peak value of each pressurizing speed test to obtain the true flat compressive strength of the corrugated paperboard; The method of obtaining the deviation gain coefficient of the corrugated board at the target time includes: Taking the average of the outlier degrees of all the corrugations in the grayscale image at each moment as the overall outlier degree of the grayscale image at each moment; If the target time is the initial time, the deviation gain coefficient of the corrugated board at the target time is set to a value of 0; If the target time is not the initial time, the deviation gain coefficient of the corrugated board at the target time is obtained based on the calculation formula of the deviation gain coefficient, and the calculation formula of the deviation gain coefficient is: ； in, represents the deviation gain coefficient of the corrugated board at the target time; Indicates the overall outlier degree of the grayscale image at the target moment; Indicates the overall outlier degree of the grayscale image at the previous moment adjacent to the target moment; It represents the maximum value function; The structural damage degree of the target pressurization speed test includes: Based on the calculation formula of the structural damage degree, the structural damage degree of the target pressurization speed test is obtained, and the calculation formula of the structural damage degree is: ； in, Indicates the degree of structural damage for the target pressurization speed test; Indicates that corrugated cardboard is Deviation gain coefficient at each moment; Indicates The maximum value of the outlier degree of all the corrugations in the grayscale image at a moment; Indicates the number of all moments under the target pressurization speed test; Represents the normalization function.

2. A corrugated board strength testing method according to claim 1, characterized in that: The deformation coefficient of each corrugation in the grayscale image obtained at the target time includes: Perform edge detection on the grayscale image at each moment to obtain a wavy edge line in the grayscale image at each moment, and detect peak points and valley points from the wavy edge line, wherein each corrugation includes one peak point and two valley points; On the wavy edge line in the grayscale image at each moment, the line between the peak point of each corrugation and the valley point on the right side of each corrugation is used as the deflection line segment of each corrugation, and the angle between the deflection line segment of each corrugation and the horizontal line is used as the deflection angle of each corrugation. The value range of the deflection angle is ; According to the difference in length of the deflection line segment and the difference in the deflection angle of the same corrugation in the grayscale image between the target moment and the initial moment, the deformation coefficient of each corrugation in the grayscale image at the target moment is obtained.

3. A corrugated board strength testing method according to claim 2, characterized in that: The step of obtaining the deformation coefficient of each corrugation in the grayscale image at the target moment according to the difference in length of the deflection line segment and the difference in the deflection angle of the same corrugation in the grayscale image between the target moment and the initial moment comprises: Based on the calculation formula of the deformation coefficient, the deformation coefficient of each corrugation in the grayscale image at the target time is obtained. The calculation formula of the deformation coefficient is: ； in, The grayscale image at the target moment The deformation coefficient of each corrugation; The grayscale image at the target moment The length of the deflection line segment of each corrugation; Represents the grayscale image at the initial moment The length of the deflection line segment of each corrugation; The grayscale image at the target moment The deflection angle of each corrugation; Represents the grayscale image at the initial moment The deflection angle of each corrugation; Represents the normalization function.

4. A corrugated board strength testing method according to claim 2, characterized in that: The outlier degree of each corrugation in the grayscale image at the target moment is obtained as follows: Based on the calculation formula of the distance metric, the distance metric between any two corrugations in the grayscale image at the target moment is obtained. The calculation formula of the distance metric is: ； in, Represents the distance measure between any two corrugations in the grayscale image at the target moment; and The deflection angle of any two corrugations in the grayscale image representing the target time; and The deformation coefficients of any two corrugations in the grayscale image representing the target time; Based on the distance metric between any two corrugations, clustering all the corrugations in the grayscale image at the target time to obtain a plurality of clusters; The cluster with the largest number of corrugations is used as a reference cluster, and the average value of the deflection angles of all the corrugations in the reference cluster is used as a reference deflection angle of the reference cluster; the average value of the deformation coefficients of all the corrugations in the reference cluster is used as a reference deformation coefficient of the reference cluster; According to the difference between the deflection angle of each corrugation in the grayscale image at the target moment and the reference deflection angle, the difference between the deformation coefficient of each corrugation and the reference deformation coefficient, and the number of corrugations in the cluster where each corrugation is located, the outlier degree of each corrugation in the grayscale image at the target moment is obtained.

5. A corrugated board strength testing method according to claim 4, characterized in that: The outlier degree of each corrugation in the grayscale image at the target moment is obtained as follows: Based on the calculation formula of the outlier distance, the outlier distance of each corrugation in the grayscale image at the target time is obtained. The calculation formula of the outlier distance is: ； in, The grayscale image at the target moment The distance of the corrugation from the group; The grayscale image at the target moment The deflection angle of each corrugation; Represents the reference deviation angle of the reference cluster; The grayscale image at the target moment The deformation coefficient of each corrugation; represents the reference deformation coefficient of the reference cluster; Taking the average of the outlier distances of all the corrugations in the grayscale image at the target moment as the overall outlier distance of the grayscale image at the target moment; The outlier distance of each corrugation in the grayscale image at the target moment is taken as the numerator, the sum of the number of corrugations in the cluster where each corrugation in the grayscale image at the target moment is located and the overall outlier distance is taken as the denominator, and the comparison value is normalized to obtain the outlier degree of each corrugation in the grayscale image at the target moment.

6. A corrugated board strength testing method according to claim 1, characterized in that: The stress peak value of each pressurization speed test is extracted as follows: The maximum value of the stress data at all times under each pressurization speed test is taken as the stress peak value of each pressurization speed test.

7. A corrugated board strength testing method according to claim 1, characterized in that: The method of obtaining the true flat compression strength of the corrugated board comprises: The two-dimensional data points consisting of the structural damage degree and the stress peak value of each pressurization speed test are mapped into a coordinate system, wherein the horizontal axis of the coordinate system represents the structural damage degree and the vertical axis represents the stress peak value, and a linear function is constructed. ,in, Indicates The peak stress of the pressure velocity test, Indicates The degree of structural damage of the pressure velocity test, represents the first unknown parameter, represents the second unknown parameter; The least square method is used in combination with the linear function to perform linear fitting on all two-dimensional data points in the coordinate system, and the value of the first unknown parameter in the linear function is calculated. The value of the first unknown parameter is used as the true flat compression strength of the corrugated board.

8. A corrugated board strength detection system, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

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