High-precision nondestructive testing method for welding seams of metal terminal blocks

Abstract

The present invention relates to the technical field of metal terminal weld detection, and specifically to a high-precision nondestructive detection method for metal terminal welding welds, including: performing fluorescent penetration detection on the copper-aluminum connection terminal and obtaining the outer surface image of the copper-aluminum connection terminal; obtaining the internal fluorescent current data of the copper-aluminum connection terminal; obtaining several weak fluorescent effect areas in the outer surface image of the copper-aluminum connection terminal; obtaining the fluorescent boundary conspicuity of the weak fluorescent effect area; obtaining the hollowness of the hole in the weak fluorescent effect area; screening several suspected welding hollow areas according to the size of the hollowness of the hole; obtaining the irregularity of the suspected welding hollow area; according to the internal fluorescent current data and irregularity of the copper-aluminum connection terminal, obtaining several hole defect areas inside the copper-aluminum connection terminal. The present invention can perform high-precision nondestructive detection on fine holes generated in the copper-aluminum connection terminal welding weld that are connected to the internal space.

Description

Technical Field

[0001] The invention relates to the technical field of metal terminal weld detection, and in particular to a high-precision nondestructive detection method for metal terminal welds. Background Art

[0002] At present, with the promotion of the application of aluminum wires in automotive wiring harnesses, the application of aluminum wires to replace traditional copper wires is gradually increasing. However, in the application process of aluminum wires replacing copper wires, electrochemical corrosion, high-temperature creep, and conductor oxidation are problems that must be faced and solved in the application process. At the same time, the application of aluminum wires replacing copper wires must meet the electrical and mechanical properties of the original copper wires to avoid performance degradation. In order to solve the problems of electrochemical corrosion, high-temperature creep, and conductor oxidation in the application of aluminum wires, friction welding technology is mainly used to manufacture copper-aluminum connection terminals to solve the problem. Therefore, non-destructive testing of copper-aluminum connection terminals is required.

[0003] The existing technology usually uses a fluorescent penetrant detection method to detect welding welds. First, a penetrant is applied to the welding area of ​​the copper-aluminum connection terminal. After it penetrates for a period of time, the penetrant on the surface of the copper-aluminum connection terminal is cleaned, and a developer is applied to adsorb the penetrant remaining in the gap space. The penetrant is then irradiated with an ultraviolet lamp to cause the adsorbed penetrant to reflect fluorescence. The fluorescent area is identified by taking an image with the equipment to complete the non-destructive detection of the welding weld area of ​​the copper-aluminum connection terminal.

[0004] In the process of manufacturing copper-aluminum connection terminals by friction welding, the copper terminals and aluminum terminals generate high temperature by rotating and rubbing against each other at their contact points, thereby completing the welding connection. However, during the rotational friction process, some inclusions in the materials of the copper terminals and aluminum terminals themselves may interfere with the strength of the rotational friction, resulting in insufficient heat generated by friction, and the material fails to reach a sufficient plasticized state, resulting in insufficient material flow, thereby generating tiny holes connected to the internal space in the corresponding copper-aluminum connection terminal welding weld; when performing fluorescent penetration testing on copper-aluminum connection terminals with such tiny holes, the tiny holes cannot retain the penetrant, causing the penetrant to penetrate into the internal tube wall of the copper-aluminum connection terminal, and effective fluorescent development cannot be performed, resulting in this part of the area being mistaken for a normal welding area without fluorescent development. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a high-precision nondestructive testing method for welding seams of metal terminal blocks.

[0006] The high-precision nondestructive testing method for the welding seam of metal terminal blocks of the present invention adopts the following technical solutions:

[0007] An embodiment of the present invention provides a high-precision nondestructive testing method for a weld of a metal terminal, the method comprising the following steps:

[0008] Perform fluorescent penetrant testing on the copper-aluminum connection terminal and obtain the outer surface image of the copper-aluminum connection terminal; obtain the internal fluorescent current data of the copper-aluminum connection terminal;

[0009] Acquire several weak fluorescence effect areas in the outer surface image of the copper-aluminum connection terminal;

[0010] According to the gray value of the pixels around the weak fluorescence effect area, the fluorescence boundary conspicuity of each weak fluorescence effect area is obtained; the connected domain detection is performed on the weak fluorescence effect area to obtain a number of connected domains in each weak fluorescence effect area; according to the fluorescence boundary conspicuity and the distribution of the connected domains in the weak fluorescence effect area, the hollowness of the holes in each weak fluorescence effect area is obtained; according to the size of the hollowness of the holes, a number of suspected welding hollow areas are screened;

[0011] According to the minimum circumscribed rectangle of the suspected welding hollow area, the irregularity of each suspected welding hollow area is obtained; according to the internal fluorescent current data and irregularity of the copper-aluminum connecting terminal, the degree of penetration connectivity of each suspected welding hollow area is obtained; according to the size of the penetration connectivity degree, several hole defect areas inside the copper-aluminum connecting terminal are screened and obtained.

[0012] Furthermore, the specific method of obtaining several weak fluorescence effect areas in the outer surface image of the copper-aluminum connection terminal is as follows:

[0013] Perform Canny edge detection on the outer surface image of the copper-aluminum connection terminal to obtain a number of edge pixels in the outer surface image of the copper-aluminum connection terminal;

[0014] Polygon fitting is performed on all edge pixels in the outer surface image of the copper-aluminum connection terminal to obtain several fitted polygonal regions in the outer surface image of the copper-aluminum connection terminal; and several weak fluorescence effect regions in the outer surface image of the copper-aluminum connection terminal are obtained according to the grayscale values ​​of the fitted polygonal regions.

[0015] Furthermore, the step of obtaining a plurality of weak fluorescence effect regions in the outer surface image of the copper-aluminum connection terminal according to the gray value of the fitted polygonal region includes the following specific steps:

[0016] Get the mean gray value of each fitted polygon area, and set the mean gray value in The fitted polygonal area between is taken as the weak fluorescence effect area. are respectively a preset first value and a preset second value.

[0017] Furthermore, the step of obtaining the fluorescence boundary conspicuity of each weak fluorescence effect area according to the grayscale values ​​of the pixels around the weak fluorescence effect area includes the following specific steps:

[0018] Get the first The average gray value of the two layers of pixels inside and outside the weak fluorescence effect area, The specific inner pixels of the weak fluorescence effect area are: The edge of the weak fluorescence effect area The edge pixels of the adjacent layer within the edge of the weak fluorescence effect area are used as the first The inner pixels of the weak fluorescence effect area; The outer pixels of the weak fluorescence effect area are specifically: The edge pixels of the adjacent layer outside the edge of the weak fluorescence effect area are used as the first The outer pixels of the weak fluorescence effect area are taken as the inverse proportional value of the absolute difference between the gray value mean of the inner pixels and the gray value mean of the outer pixels. The fluorescence boundary visibility of the weak fluorescence effect area.

[0019] Furthermore, the hollowness of the holes in each weak fluorescence effect area is obtained according to the fluorescence boundary visibility and the distribution of the connected domains in the weak fluorescence effect area, and the specific steps include the following:

[0020]

[0021] In the formula, For the The centroid of all connected domains in the weak fluorescence effect area to the The mean distance between the centroids of the weak fluorescence effect areas; For the The fluorescence boundary visibility of the weak fluorescence effect area; is an exponential function with a natural constant as base; For the The hollowness of the holes in the weak fluorescence effect area.

[0022] Furthermore, the method of screening a number of suspected welding hollow areas according to the size of the hollowness of the holes includes the following specific steps:

[0023] A first threshold is preset, and a weak fluorescence effect area with a hole hollowness greater than the first threshold is regarded as a suspected welding hollow area, otherwise, it is not regarded as a suspected welding hollow area. The first threshold is 0.7.

[0024] Furthermore, the irregularity of each suspected weld hollow area is obtained according to the minimum circumscribed rectangle of the suspected weld hollow area, and the specific steps include the following:

[0025]

[0026] In the formula, The specific method of obtaining is as follows: The minimum bounding rectangle of the suspected welding hollow area is recorded as the first minimum bounding rectangle, and the The shortest distance between each pixel on the edge of the suspected welding hollow area and the first minimum circumscribed rectangle side is The standard deviation of the shortest distance between all pixels on the edge of the suspected welding hollow area and the first minimum circumscribed rectangle is recorded as ; For the The minimum angle between the long side of the smallest circumscribed rectangle of a suspected weld hollow area and the horizontal line; For the Irregularities in suspected weld hollow areas.

[0027] Furthermore, the method of obtaining the penetration connectivity of each suspected welding hollow area according to the internal fluorescent current data and irregularity of the copper-aluminum connection terminal includes the following specific steps:

[0028]

[0029] In the formula, For the Irregularities in suspected weld hollow areas; is the mean value of all current values ​​in the internal fluorescence current data of the copper-aluminum connection terminal; is the sigmoid function; For the The degree of penetration connectivity of a suspected weld hollow area.

[0030] Furthermore, the method of screening and obtaining a plurality of hole defect areas inside the copper-aluminum connection terminal according to the degree of penetration connectivity includes the following specific steps:

[0031] A second threshold is preset, and the suspected welding hollow area with a penetration connectivity greater than the second threshold is regarded as a hole defect area inside the copper-aluminum connecting terminal. Otherwise, it is not regarded as a hole defect area inside the copper-aluminum connecting terminal. The second threshold is 0.65.

[0032] Furthermore, the first value and the second value are 120 and 150 respectively.

[0033] The beneficial effect of the technical solution of the present invention is that according to the present invention, high-precision non-destructive detection can be performed on the tiny holes connected to the internal space in the welding seam of the copper-aluminum connection terminal. When determining several weak fluorescence effect areas in the outer surface image of the copper-aluminum connection terminal, by performing edge detection on the outer surface image of the copper-aluminum connection terminal and polygon fitting on the edge pixels, and determining several weak fluorescence effect areas in the outer surface image of the copper-aluminum connection terminal according to the grayscale value of the fitted polygonal area, the subtle performance of the tiny holes connected to the internal space in the welding seam of the copper-aluminum connection terminal is accurately analyzed, and the scientificity, accuracy and objectivity of the weak fluorescence effect area are improved. When determining the suspected welding hollow area, the suspected welding hollow area is determined by analyzing the fluorescence boundary conspicuity, fluorescence boundary conspicuity and the distribution of the connected domains in the weak fluorescence effect area, and the scientificity, accuracy and objectivity of the suspected welding hollow area are improved. When determining several hole defect areas inside the copper-aluminum connecting terminal, the irregularity of the suspected welding hollow area and the change in the fluorescent current data inside the copper-aluminum connecting terminal were deeply analyzed, and the tiny holes generated in the welding seam of the copper-aluminum connecting terminal and connected to the internal space were obtained, which improved the accuracy of the tiny holes generated in the welding seam of the copper-aluminum connecting terminal and connected to the internal space. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be 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.

[0035] Figure 1 A flowchart of the steps of a high-precision nondestructive testing method for a welding seam of a metal terminal provided by an embodiment of the present invention;

[0036] Figure 2 A schematic diagram of the outer surface image of a copper-aluminum connecting terminal provided by an embodiment of the present invention;

[0037] Figure 3 A schematic diagram of the spatial relationship between the internal hollowing and hole gaps of an aluminum material provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation method, structure, features and effects of the high-precision non-destructive testing method for the welding seam of the metal terminal proposed by the present invention are described in detail below in combination 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.

[0039] 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.

[0040] The specific scheme of the high-precision nondestructive testing method for the welding seam of the metal terminal provided by the present invention is described in detail below with reference to the accompanying drawings.

[0041] See also Figure 1 , which shows a flowchart of the steps of a high-precision nondestructive testing method for a metal terminal welding weld provided by an embodiment of the present invention, the method comprising the following steps:

[0042] Step S001, performing fluorescent penetrant testing on the copper-aluminum connection terminal and obtaining an outer surface image of the copper-aluminum connection terminal; obtaining internal fluorescent current data of the copper-aluminum connection terminal.

[0043] It should be noted that the main purpose of this embodiment is to perform high-precision non-destructive testing on tiny holes generated in the weld of the copper-aluminum connection terminal and connected to the internal space. Before starting the analysis, relevant data is first collected.

[0044] Specifically, the copper-aluminum connection terminal is processed by the fluorescent penetration detection method and the outer surface image of the copper-aluminum connection terminal is obtained, as follows:

[0045] The process of obtaining the outer surface image of the copper-aluminum connection terminal based on the fluorescent penetrant detection method is as follows:

[0046] 1) Apply the penetrant to the surface of the copper-aluminum connection terminal and let it stand for 10 minutes.

[0047] 2) Clean the penetrant on the surface of the copper and aluminum connection terminals.

[0048] 3) Dry the surface of the copper-aluminum connection terminals.

[0049] 4) Apply the developer to the copper-aluminum connection terminals.

[0050] 5) Using an ultraviolet lamp to irradiate the copper-aluminum connecting terminal, and using an industrial camera to capture an image, the acquired image is gray-scaled to obtain an outer surface image of the copper-aluminum connecting terminal.

[0051] It should be noted that the fluorescent penetrant testing method mainly includes: applying penetrant to the surface of the copper-aluminum connection terminal, cleaning the penetrant on the surface of the copper-aluminum connection terminal, drying the surface of the copper-aluminum connection terminal, applying developer to the copper-aluminum connection terminal and using ultraviolet light to irradiate the copper-aluminum connection terminal for light inspection. Figure 2 , Figure 2 Schematic diagram of the outer surface image of the copper-aluminum connecting terminal of this embodiment.

[0052] Furthermore, the internal fluorescence current data of the copper-aluminum connection terminal is obtained, as follows:

[0053] The photosensor is placed inside the copper-aluminum connecting terminal. There is a hollow area in the aluminum terminal of the copper-aluminum connecting terminal. The probe of the photosensor is placed in the hollow area of ​​the aluminum terminal to detect the fluorescence signal, output the electrical signal to the system platform, and record the fluorescence current data inside the copper-aluminum connecting terminal for 5 minutes.

[0054] It should be noted that the present embodiment records the internal fluorescent current data of the copper-aluminum connection terminal for 5 minutes, which can be adjusted according to the actual situation.

[0055] At this point, the outer surface image of the copper-aluminum connecting terminal is obtained, and the internal fluorescent current data of the copper-aluminum connecting terminal is obtained.

[0056] Step S002: perform edge detection on the outer surface image of the copper-aluminum connection terminal to obtain a number of edge pixels in the outer surface image of the copper-aluminum connection terminal; perform polygon fitting on all edge pixels in the outer surface image of the copper-aluminum connection terminal to obtain a number of fitted polygonal regions in the outer surface image of the copper-aluminum connection terminal; and obtain a number of weak fluorescence effect regions in the outer surface image of the copper-aluminum connection terminal according to the grayscale value of the fitted polygonal region.

[0057] It should be noted that when the copper-aluminum connecting terminals are friction welded, there are usually a certain amount of impurities in the materials of the copper terminals and the aluminum terminals respectively. These impurities may be gradually concentrated on the welding seam of the two metals to form inclusions during the process of plasticization between the copper and aluminum. This interferes with the strength of the rotational friction, resulting in insufficient heat generated by friction, and causing certain holes and gaps in the welding seam area. These holes and gaps cannot retain the penetrant; however, the penetrant will remain in the tube wall area, thereby absorbing the developer, which will produce a fluorescent effect under ultraviolet irradiation, forming a fluorescent phenomenon in a certain closed area.

[0058] Specifically, edge detection is performed on the outer surface image of the copper-aluminum connection terminal to obtain a number of edge pixels in the outer surface image of the copper-aluminum connection terminal, as follows:

[0059] Canny edge detection is performed on the outer surface image of the copper-aluminum connecting terminal to obtain several edge pixels in the outer surface image of the copper-aluminum connecting terminal.

[0060] Furthermore, polygon fitting is performed on all edge pixels in the outer surface image of the copper-aluminum connection terminal to obtain a plurality of fitted polygonal regions in the outer surface image of the copper-aluminum connection terminal.

[0061] It should be noted that the existing method of performing polygon fitting on all edge pixels in the outer surface image of the copper-aluminum connection terminal to obtain several fitted polygonal regions in the outer surface image of the copper-aluminum connection terminal is a polygon fitting method, which will not be repeated in this embodiment.

[0062] It should be noted that the ultraviolet light irradiated on the gaps of the holes will be diffusely reflected inside the tube walls because the tube walls inside the holes are not smooth. In addition, the developer adsorbed inside the tube walls is unevenly distributed and has a small amount of residual penetrant, resulting in a relatively weak fluorescent reaction in the holes.

[0063] Specifically, according to the gray value of the fitted polygonal area, several weak fluorescence effect areas in the outer surface image of the copper-aluminum connection terminal are obtained, as follows:

[0064] Get the mean gray value of each fitted polygon area, and set the mean gray value in The fitted polygonal area between is taken as the weak fluorescence effect area. They are respectively a preset first value and a preset second value. In this embodiment, the first value is 120 and the second value is 150.

[0065] It should be noted that the grayscale range is selected because a single grayscale threshold will include a large number of other normal welding areas, which greatly increases the recognition time. Considering the actual situation, a grayscale range consisting of two grayscale thresholds is selected.

[0066] At this point, several weak fluorescence effect areas in the outer surface image of the copper-aluminum connecting terminal are obtained.

[0067] Step S003, according to the gray value of the pixels around the weak fluorescence effect area, obtain the fluorescence boundary conspicuity of each weak fluorescence effect area; perform connected domain detection on the weak fluorescence effect area to obtain a number of connected domains in each weak fluorescence effect area; according to the fluorescence boundary conspicuity and the distribution of the connected domains in the weak fluorescence effect area, obtain the hollowness of the holes in each weak fluorescence effect area; according to the size of the hollowness of the holes, screen a number of suspected welding hollow areas.

[0068] It should be noted that in the actual process of fluorescent penetrant testing, for smaller and shallower gaps on the surface that are not connected to the internal space of the copper-aluminum connection terminal, the developer on the surface of this part of the gap will adsorb relatively less penetrant, showing a weaker fluorescent reaction, so this part of the gap area will cause interference; at the same time, because the inner layer structure of this part of the gap area is different from that of the hole gap, this part of the gap area can retain the penetrant, so the boundary division of the fluorescence on the surface notch will have more penetrant to support the brightness, and the resulting fluorescent edge feeling will be more obvious.

[0069] Specifically, the fluorescence boundary conspicuity of each weak fluorescence effect area is obtained according to the grayscale values ​​of the pixels around the weak fluorescence effect area, as follows:

[0070] Get the first The average gray value of the two layers of pixels inside and outside the weak fluorescence effect area, The specific inner pixels of the weak fluorescence effect area are: The edge of the weak fluorescence effect area The edge pixels of the adjacent layer within the edge of the weak fluorescence effect area are used as the first The inner pixels of the weak fluorescence effect area; The outer pixels of the weak fluorescence effect area are specifically: The edge pixels of the adjacent layer outside the edge of the weak fluorescence effect area are used as the first The outer pixels of the weak fluorescence effect area are taken as the inverse proportional value of the absolute difference between the gray value mean of the inner pixels and the gray value mean of the outer pixels. The fluorescence boundary visibility of the weak fluorescence effect area.

[0071] It should be noted that this embodiment adopts The model is used to perform inverse proportional processing on the absolute difference between the mean grayscale value of the inner layer pixels and the mean grayscale value of the outer layer pixels. The input of the model is the absolute difference between the mean grayscale value of the inner layer pixels and the mean grayscale value of the outer layer pixels. When the mean grayscale value difference of the pixels around the weak fluorescence effect area is smaller, it means that the boundary division of the fluorescence on the surface gap has more penetrants for brightness support, the fluorescence edge will be more obvious, and the fluorescence boundary will be more obvious.

[0072] It should be noted that for holes and gaps, the fluorescence phenomenon in the holes and gaps is mainly displayed by the reflection of the developer adsorbed by the penetrant remaining on the tube wall. There is no penetrant to support the fluorescence phenomenon in the middle of the area. Therefore, under the premise that the regional fluorescence reflection phenomenon is weak, there will usually be relatively dark voids in the area.

[0073] Specifically, the connected domain detection is performed on the weak fluorescence effect area to obtain a number of connected domains in each weak fluorescence effect area. It should be noted that the connected domain detection is performed on each weak fluorescence effect area to obtain a number of connected domains in the corresponding weak fluorescence effect area as an existing method for connected domain detection, which will not be described in detail in this embodiment.

[0074] Specifically, according to the fluorescence boundary visibility and the distribution of connected domains in the weak fluorescence effect area, the hollowness of each weak fluorescence effect area is obtained, as follows:

[0075]

[0076] In the formula, For the The centroid of all connected domains in the weak fluorescence effect area to the The mean distance between the centroids of the weak fluorescence effect areas; For the The fluorescence boundary visibility of the weak fluorescence effect area; is an exponential function with a natural constant as the base. The model is used to present the inverse proportional relationship and normalization processing. is the input of the model; For the The hollowness of the holes in the weak fluorescence effect area.

[0077] It should be noted that when The centroid of all connected domains in the weak fluorescence effect area to the The smaller the mean value of the centroid distance of the weak fluorescence effect area is, the more concentrated the multiple relatively dark hole areas are in the weak fluorescence effect area, the more obvious the hollowness of the holes is, and the greater the hollowness of the holes is; at the same time, if the fluorescence boundary of the weak fluorescence effect area is also less obvious, it means that the brightness of the relatively dark hole part is poorer and the hollowness of the holes is greater.

[0078] Furthermore, according to the size of the hollowness of the holes, several suspected welding hollow areas are screened, as follows:

[0079] A first threshold is preset, and a weak fluorescence effect area with a hole hollowness greater than the first threshold is regarded as a suspected welding hollow area, otherwise, it is not regarded as a suspected welding hollow area. This embodiment is described with the first threshold being 0.7.

[0080] At this point, several suspected weld hollow areas have been screened.

[0081] Step S004, according to the minimum circumscribed rectangle of the suspected welding hollow area, obtain the irregularity of each suspected welding hollow area; according to the internal fluorescent current data and irregularity of the copper-aluminum connection terminal, obtain the penetration connectivity degree of each suspected welding hollow area; according to the size of the penetration connectivity degree, screen and obtain several hole defect areas inside the copper-aluminum connection terminal.

[0082] It should be noted that in the process of manufacturing copper-aluminum connection terminals by friction welding, a copper rod and an aluminum rod will be selected for rotational friction. After the two metals are plastically deformed, they will be further trimmed to form the required shape of the copper-aluminum connection terminal. In the processed copper-aluminum connection terminal, the device corresponding to the aluminum material is hollowed out. If there are inclusions in the copper-aluminum welding seam area, resulting in uneven copper-aluminum contact surfaces, the heat generated by friction welding will also produce different heat dispersions due to the flatness of the contact surface, resulting in higher heat diffusion in local areas of the aluminum material, and the physical structure is more easily damaged. In addition, the force applied to the aluminum material during friction welding may cause cracks in the aluminum material, connecting the hollow space inside the aluminum material with the hollow holes and gaps in the copper-aluminum welding area, so that the penetrant applied to the welding seam area will also penetrate into the hollow space inside the aluminum material, and also produce a fluorescent reaction. Please refer to Figure 3 , Figure 3 Schematic diagram of the spatial relationship between the hollowing out and the hole gaps inside the aluminum material of this embodiment.

[0083] It should be noted that, under normal circumstances, the copper-aluminum connecting part on the copper-aluminum connecting terminal is distributed vertically in the longitudinal direction; if the copper-aluminum welding weld area is more inclined and the edge is more uneven, it means that the copper-aluminum welding weld area is formed by friction welding. The greater the influence of inclusions on the composition of the welding area, the more uneven the heat generated by friction welding is dispersed, and the more likely it is that cracks will occur inside the aluminum material.

[0084] Specifically, according to the minimum circumscribed rectangle of the suspected welding hollow area, the irregularity of each suspected welding hollow area is obtained, as follows:

[0085]

[0086] In the formula, The specific method of obtaining is as follows: The minimum bounding rectangle of the suspected welding hollow area is recorded as the first minimum bounding rectangle, and the The shortest distance between each pixel on the edge of the suspected welding hollow area and the first minimum circumscribed rectangle side is The standard deviation of the shortest distance between all pixels on the edge of the suspected welding hollow area and the first minimum circumscribed rectangle is recorded as ; For the The minimum angle between the long side of the smallest circumscribed rectangle of a suspected weld hollow area and the horizontal line; For the Irregularities in suspected weld hollow areas.

[0087] It should be noted that The larger the standard deviation of the shortest distance between all pixels on the edge of the suspected welding hollow area and the first minimum circumscribed rectangle side, the more irregular the edge of the suspected welding hollow area is and the greater the irregularity is. The larger the minimum angle between the long side of the minimum circumscribed rectangle of a suspected welding hollow area and the horizontal line, the more irregular it is. This is because under normal circumstances, the copper-aluminum connecting part of the copper-aluminum connecting terminal is distributed vertically in the longitudinal direction. The larger the angle, the less vertical it is and the greater the irregularity.

[0088] It should be noted that although a fluorescent reaction will occur in the hollow space inside the aluminum material, the fluorescence brightness will not be very large due to the influence of the tiny space connecting the hollow space inside the aluminum material and the hollow holes and gaps on the copper-aluminum welding area.

[0089] Specifically, based on the internal fluorescent current data and irregularity of the copper-aluminum connection terminal, the penetration connectivity of each suspected welding hollow area is obtained, as follows:

[0090]

[0091] In the formula, For the Irregularities in suspected weld hollow areas; is the mean value of all current values ​​in the fluorescence current data inside the copper-aluminum connection terminal; is the sigmoid function, used for normalization; For the The degree of penetration connectivity of a suspected weld hollow area.

[0092] It should be noted that the greater the irregularity of the suspected welding hollow area, the more likely the suspected welding hollow area is to be infiltrated and connected, and the greater the degree of infiltration and connectivity; at the same time, if the mean of all current values ​​in the fluorescent current data inside the copper-aluminum connecting terminal is larger, it means that the degree of infiltration and connectivity is greater due to the influence of the tiny space connected by the hollow space inside the aluminum material and the hollow holes and gaps in the copper-aluminum welding area.

[0093] Furthermore, according to the degree of penetration connectivity, several hole defect areas inside the copper-aluminum connection terminal are screened and obtained, as follows:

[0094] A second threshold is preset, and a suspected welding hollow area with a penetration connectivity greater than the second threshold is regarded as a hole defect area inside the copper-aluminum connection terminal. Otherwise, it is not regarded as a hole defect area inside the copper-aluminum connection terminal. This embodiment is described with the second threshold being 0.65.

[0095] It should be noted that when the screening shows that there are hole defect areas inside the copper-aluminum connecting terminal, it means that the produced copper-aluminum connecting terminal is unqualified and needs to be returned to the factory for repair. The details will not be repeated here.

[0096] Through the above steps, a high-precision nondestructive testing method for welding seams of metal terminal blocks is completed.

[0097] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-precision nondestructive testing method for welding seams of metal terminal blocks, characterized in that: The method comprises the following steps: Perform fluorescent penetrant testing on the copper-aluminum connection terminal and obtain the outer surface image of the copper-aluminum connection terminal; obtain the internal fluorescent current data of the copper-aluminum connection terminal; Acquire several weak fluorescence effect areas in the outer surface image of the copper-aluminum connection terminal; wherein the method for acquiring the weak fluorescence effect areas is: perform Canny edge detection on the outer surface image of the copper-aluminum connection terminal to obtain several edge pixels in the outer surface image of the copper-aluminum connection terminal; perform polygon fitting on all edge pixels in the outer surface image of the copper-aluminum connection terminal to obtain several fitted polygonal areas in the outer surface image of the copper-aluminum connection terminal; obtain several weak fluorescence effect areas in the outer surface image of the copper-aluminum connection terminal according to the gray value of the fitted polygonal area; According to the grayscale values ​​of the pixels around the weak fluorescence effect area, the fluorescence boundary conspicuity of each weak fluorescence effect area is obtained; the connected domain detection is performed on the weak fluorescence effect area to obtain a number of connected domains in each weak fluorescence effect area; according to the fluorescence boundary conspicuity and the distribution of the connected domains in the weak fluorescence effect area, the hollowness of the holes in each weak fluorescence effect area is obtained; according to the size of the hollowness of the holes, a number of suspected welding hollow areas are screened; According to the minimum circumscribed rectangle of the suspected welding hollow area, the irregularity of each suspected welding hollow area is obtained; according to the internal fluorescent current data and irregularity of the copper-aluminum connecting terminal, the degree of penetration connectivity of each suspected welding hollow area is obtained; according to the size of the penetration connectivity degree, several hole defect areas inside the copper-aluminum connecting terminal are screened and obtained.

2. The high-precision nondestructive testing method for welding seams of metal terminal blocks according to claim 1, characterized in that: The specific steps of obtaining a plurality of weak fluorescence effect regions in the outer surface image of the copper-aluminum connection terminal according to the gray value size of the fitted polygonal region are as follows: Get the mean gray value of each fitted polygon area, and set the mean gray value in The fitted polygonal area between is taken as the weak fluorescence effect area. are respectively a preset first value and a preset second value.

3. The high-precision nondestructive testing method for welding seams of metal terminal blocks according to claim 1, characterized in that: The specific steps of obtaining the fluorescence boundary conspicuity of each weak fluorescence effect area according to the grayscale values ​​of the pixels around the weak fluorescence effect area are as follows: Get the first The average gray value of the two layers of pixels inside and outside the weak fluorescence effect area, The specific inner pixels of the weak fluorescence effect area are: The edge of the weak fluorescence effect area The edge pixels of the adjacent layer within the edge of the weak fluorescence effect area are used as the first The inner pixels of the weak fluorescence effect area; The outer pixels of the weak fluorescence effect area are specifically: The edge pixels of the adjacent layer outside the edge of the weak fluorescence effect area are used as the first The outer pixels of the weak fluorescence effect area are taken as the inverse proportional value of the absolute difference between the gray value mean of the inner pixels and the gray value mean of the outer pixels. The fluorescence boundary visibility of the weak fluorescence effect area.

4. The high-precision nondestructive testing method for welding seams of metal terminal blocks according to claim 1, characterized in that: The method of obtaining the hollowness of each weak fluorescence effect area according to the fluorescence boundary visibility and the distribution of the connected domains in the weak fluorescence effect area includes the following specific steps: In the formula, For the The centroid of all connected domains in the weak fluorescence effect area to the The mean distance between the centroids of the weak fluorescence effect areas; For the The fluorescence boundary visibility of the weak fluorescence effect area; is an exponential function with a natural constant as base; For the The hollowness of the holes in the weak fluorescence effect area.

5. The high-precision nondestructive testing method for welding seams of metal terminal blocks according to claim 1, characterized in that: The specific steps of screening a number of suspected welding hollow areas according to the size of the hollowness of the holes are as follows: A first threshold is preset, and a weak fluorescence effect area with a hole hollowness greater than the first threshold is regarded as a suspected welding hollow area, otherwise, it is not regarded as a suspected welding hollow area.

6. The high-precision nondestructive testing method for welding seams of metal terminal blocks according to claim 1, characterized in that: The method of obtaining the irregularity of each suspected welding hollow area according to the minimum circumscribed rectangle of the suspected welding hollow area includes the following specific steps: In the formula, The specific method of obtaining is as follows: The minimum bounding rectangle of the suspected welding hollow area is recorded as the first minimum bounding rectangle, and the The shortest distance between each pixel on the edge of the suspected welding hollow area and the first minimum circumscribed rectangle side is The standard deviation of the shortest distance between all pixels on the edge of the suspected welding hollow area and the first minimum circumscribed rectangle is recorded as ; For the The minimum angle between the long side of the smallest circumscribed rectangle of a suspected weld hollow area and the horizontal line; For the Irregularities in suspected weld hollow areas.

7. The high-precision nondestructive testing method for welding seams of metal terminal blocks according to claim 1, characterized in that: The method of obtaining the penetration connectivity of each suspected welding hollow area according to the internal fluorescent current data and irregularity of the copper-aluminum connection terminal includes the following specific steps: In the formula, For the Irregularities in suspected weld hollow areas; is the mean value of all current values ​​in the fluorescence current data inside the copper-aluminum connection terminal; is the sigmoid function; For the The degree of penetration connectivity of a suspected weld hollow area.

8. The high-precision nondestructive testing method for welding seams of metal terminal blocks according to claim 1, characterized in that: The method of screening and obtaining a plurality of hole defect areas inside the copper-aluminum connection terminal according to the degree of penetration connectivity includes the following specific steps: A second threshold is preset, and a suspected welding hollow area with a penetration connectivity greater than the second threshold is regarded as a hole defect area inside the copper-aluminum connecting terminal. Otherwise, it is not regarded as a hole defect area inside the copper-aluminum connecting terminal.

9. The high-precision nondestructive testing method for welding seams of metal terminal blocks according to claim 2, characterized in that: The first value and the second value are 120 and 150 respectively.

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