Aluminum alloy spot welding quality detection method

Abstract

The invention discloses an aluminum alloy spot welding quality detection method. The method comprises the following steps that S1, magnetic field signals generated in the aluminum alloy spot welding process are collected through a magnetic induction sensor array; s2, performing amplification processing on the magnetic field signal through a signal amplification circuit to obtain a magnetic field amplification signal; s3, carrying out feature signal extraction on the magnetic field amplification signal through a principal component analysis method; and S4, the spot welding quality result of the aluminum alloy is obtained according to the characteristic signals. The method is used for solving the technical problems that a spot welding quality detection method in the prior art has high requirements on a detection surface and is not suitable for aluminum alloy resistance spot welding quality detection.

Description

Technical Field

[0001] The present application relates to the technical field of spot welding quality detection, and in particular to a method for detecting the quality of aluminum alloy spot welding. Background Art

[0002] The quality inspection of spot welding joints is more troublesome, and usually only destructive tests can be used to detect problems. The welding quality depends on the detection method. The lap joint of spot welding not only increases the weight of the structure, but also forms a certain angle at the welding nugget attachment of the workpiece, which will cause the fatigue performance and tensile resistance of the joint to decrease. In the actual processing and manufacturing process, the electrode tip will deform and wear, the surface state of the workpiece will change, the electrode pressure will change, and the current density will change. Even if the processing and production are carried out according to the same welding process, many production problems will still occur. If there are problems in the welding process, it is usually necessary to add a lot of welds or dissect them to make the welding quality meet the standards, which will greatly increase the processing cost. Regarding the manufacturing of aerospace devices, many important components cannot be completely dissected, so it is still necessary to rely on manual inspection of welding quality, and even so it is difficult to distinguish between false welds.

[0003] Spot welding, as an important welding method, has been widely used. The quality of welding affects the service life and performance of the entire welded structure. Controlling welding quality has become one of the research topics of welders. To control welding quality, it is necessary to detect the welding current, so the current sensor has become an indispensable part. With the current sensor, the control system can compare the sampled signal with the standard signal, and then control the problem of welding quality degradation caused by the drop in electrode pressure and other factors during welding, so as to ensure the welding quality.

[0004] There are many methods for spot welding quality inspection in the prior art, such as ultrasonic inspection and X-ray inspection. Among various non-destructive inspection methods, ultrasonic inspection has low cost, high efficiency and is relatively easy to operate. However, ultrasonic inspection has high requirements on the surface to be inspected, so ultrasonic inspection is not suitable for the inspection of aluminum alloy resistance spot welding quality.

[0005] Therefore, in view of the problems existing in the above-mentioned prior art, a method for detecting the quality of aluminum alloy spot welding is proposed to solve them. Summary of the invention

[0006] The embodiment of the present application provides a method for detecting the quality of aluminum alloy spot welding, which is used to solve the technical problem that the spot welding quality detection method in the prior art has high requirements on the detection surface and is not suitable for aluminum alloy resistance spot welding quality detection.

[0007] In view of this, the present application provides a method for detecting the quality of aluminum alloy spot welding, comprising the following steps:

[0008] S1, collecting magnetic field signals generated during the aluminum alloy spot welding process through a magnetic sensor array;

[0009] S2, amplifying the magnetic field signal through a signal amplification circuit to obtain a magnetic field amplification signal;

[0010] S3, extracting characteristic signals from the magnetic field amplification signal by principal component analysis;

[0011] S4. Obtaining the aluminum alloy spot welding quality result according to the characteristic signal.

[0012] Optionally, the specific method steps for collecting the magnetic field signal generated during the aluminum alloy spot welding process by the magnetic induction sensor array in step S1 are:

[0013] S11, select 4 magnetic sensors;

[0014] S12, distributing the four magnetic sensors in a circular shape around the aluminum alloy spot welding area to collect magnetic field signals.

[0015] Optionally, the specific method steps for extracting characteristic signals from the magnetic field amplified signal by principal component analysis in step S3 are:

[0016] S31, performing standardization processing on the magnetic field amplification signal data to obtain a magnetic signal data matrix, and the magnetic signal data matrix is ​​still recorded as x;

[0017] S32, calculating the covariance matrix R of the magnetic signal data matrix x XX ;

[0018] S33, calculating the covariance matrix R XX The first n eigenvalues ​​of n , and its corresponding eigenvectors v1, v2, …, v n , where n is the number of principal components selected;

[0019] S34, calculate the i-th principal component, and its calculation formula is: i =v i T x, i = 1, 2, ..., n, define the i-th principal component y i The variance contribution of is: The first n principal components y1, y2, ..., y n The cumulative variance contribution rate is According to the cumulative variance contribution rate, the characteristic signal is obtained.

[0020] Optionally, in step S34, the specific method steps for obtaining the characteristic signal according to the cumulative variance contribution rate are:

[0021] S341, determining the eigenvalue of the number sample covariance of the principal component according to the cumulative contribution rate;

[0022] S342, arranging the eigenvalues ​​from large to small, and extracting the principal components of the eigenvalues ​​that satisfy a threshold value greater than a preset threshold value to obtain a characteristic signal.

[0023] Optionally, the magnetic sensors are arranged around the aluminum alloy spot welding points, and the distance between each magnetic sensor and the aluminum alloy spot welding point is 30-90 mm.

[0024] Optionally, the magnetic sensor uses an indium antimonide magnetoresistor as a sensor probe.

[0025] Optionally, the specific method steps for obtaining the aluminum alloy spot welding quality result according to the characteristic signal in step S4 are:

[0026] S41, acquiring the characteristic signal;

[0027] S42, extracting the nugget area information in the characteristic signal;

[0028] S43, comparing the extracted nugget area information with the standard nugget area to obtain the aluminum alloy spot welding quality result.

[0029] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0030] The present application provides a method for detecting the quality of aluminum alloy spot welding, which collects magnetic field signals generated during the aluminum alloy spot welding process through a magnetic sensor array; amplifies the magnetic field signals through a signal amplification circuit to obtain a magnetic field amplification signal; extracts characteristic signals from the magnetic field amplification signal through a principal component analysis method; obtains the aluminum alloy spot welding quality result based on the characteristic signal; realizes accurate and reliable data collection, and obtains spatial information that cannot be interpreted by a single sensor, provides the maximum amount of information for accurately judging the quality of the weld, and realizes information redundancy, information complementarity, and information real-timeness; it is worth mentioning that the principal component analysis algorithm is proposed in this article as the main method for extracting characteristic values ​​of magnetic field signals collected in array detection of weld quality, which improves the extraction efficiency and accuracy of magnetic field signal characteristic values; the magnetic sensor array quality detection method processes the magnetic field signal during the aluminum alloy spot welding process by studying the characteristic quantity extraction algorithm, and finally obtains the relationship between the characteristic signal of the welding magnetic signal array and the weld quality, which provides an effective judgment method for further judging the weld quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly express the technical solutions of the embodiments of the present application, the drawings required for describing the embodiments 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 creative work.

[0032] Figure 1 This is a step diagram of a method for detecting quality of aluminum alloy spot welding provided in an embodiment of the present application. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0034] For easier understanding, see Figure 1 The present invention provides a method for detecting the quality of aluminum alloy spot welding, comprising the following steps:

[0035] S1, collecting magnetic field signals generated during the aluminum alloy spot welding process through a magnetic sensor array;

[0036] Specifically, four magnetic sensors are selected, and the four magnetic sensors all use indium antimonide (InSb) magnetoresistor as the sensor probe; then the four magnetic sensors are distributed in a circular shape around the aluminum alloy spot welding to collect magnetic field signals. Optionally, when the four magnetic sensors are arranged around the aluminum alloy spot welding point, the distance between each magnetic sensor and the aluminum alloy spot welding point is 30-90mm.

[0037] Specifically, the main component of the magnetic sensor is indium antimonide (InSb), which is prepared by vacuum coating technology, has a surface area of ​​0.4×0.3mm, and is made using vacuum compression film technology. The temperature coefficient is -1.6~-2.0% / ℃, the nominal resistance is 150~300□, the linearity is about 1.5%, and the resolution is >0.01mT, so that the sensitivity and linearity of the magnetic resistor can reach a very good level, which is a good choice for welding signal detection.

[0038] S2. Amplify the magnetic field signal through a signal amplification circuit to obtain a magnetic field amplification signal; specifically, the collected magnetic field signal is amplified by an AD620 instrument amplifier. The AD620 instrument amplifier can ensure the performance indicators such as low offset voltage, low offset voltage drift and low noise required for high-gain precision amplification; and has the advantages of high common-mode rejection ratio, high input impedance, low power consumption, etc., and the amplification factor value can be set by adjusting a resistor.

[0039] S3, extracting characteristic signals from the magnetic field amplification signal by principal component analysis;

[0040] S4. Deriving the aluminum alloy spot welding quality result according to the characteristic signal to detect the aluminum alloy spot welding quality.

[0041] Furthermore, in step S3, the specific method steps for extracting characteristic signals from the magnetic field amplification signal by principal component analysis are as follows:

[0042] S31, performing standardization processing on the magnetic field amplification signal data to obtain a magnetic signal data matrix, and the magnetic signal data matrix is ​​still recorded as x;

[0043] S32, calculate the covariance matrix R of the magnetic signal data matrix x XX ;

[0044] S33. Calculate the covariance matrix R XX The first n eigenvalues ​​of n , and its corresponding eigenvectors v1, v2, …, v n , where n is the number of principal components selected;

[0045] S34, calculate the i-th principal component, and its calculation formula is:i =v i T x, i = 1, 2, ..., n, the variance contribution rate of the i-th principal component yi is defined as: The first n principal components y1, y2, ..., y n The cumulative variance contribution rate is According to the cumulative variance contribution rate, the characteristic signal is obtained;

[0046] Specifically, if the cumulative variance contribution rate of the first n principal components is large enough, it can be known that the first n principal components can be taken as feature signals, and the remaining (mn) signals (m is the number of sampling groups) can be discarded, thereby reducing the number of feature signals, that is, compressing the dimension of the feature space, thereby improving the extraction efficiency and accuracy of feature signal information.

[0047] Furthermore, in step S34, the specific method steps for obtaining the characteristic signal according to the cumulative variance contribution rate are as follows:

[0048] S341, determining the eigenvalue of the number sample covariance of the principal components according to the cumulative contribution rate;

[0049] S342, arranging the eigenvalues ​​from large to small, and extracting the principal components of the eigenvalues ​​that satisfy a threshold value that is greater than a preset threshold, to obtain a characteristic signal.

[0050] Furthermore, the specific method steps for obtaining the aluminum alloy spot welding quality result according to the characteristic signal in step S4 are as follows:

[0051] S41, acquiring characteristic signals;

[0052] S42, extracting the nugget area information in the characteristic signal;

[0053] S43, then compare the extracted nugget area information with the standard nugget area to obtain the aluminum alloy spot welding quality result.

[0054] Specifically, a circular magnetic sensor array detection experiment was constructed. The experimental device was: an inverter DC DN-80 fixed spot welding machine (control box: M IYACH II S-444B); a circular magnetic sensor array; an industrial computer and a PC I-4472 dynamic signal data acquisition card;

[0055] The experimental steps include:

[0056] Step 1: Arrange a circular magnetic sensor array around the welding point, with the distance between each magnetic sensor unit and the welding point being 60 mm, and each sensor unit being arranged in a ring;

[0057] Step 2: Set the welding time to 30ms, change the number of acquisition channels to 0-5, set the welding current to 10kA, 14kA, and 18kA, and collect data and waveforms of the magnetic field information. Perform five spot weldings and collect five signals under each current parameter, and save the data to the disk;

[0058] Step three, change the distance between the welding spot and the center of the array to 60mm, keep the welding time unchanged, set the welding current to 10kA, 14kA, and 18kA respectively, and perform five spot weldings under each current parameter. Then collect data and waveform of the magnetic field information and save the data on the disk.

[0059] Step 4: Change the distance between the solder joint and the center of the array to 90 mm and perform the experiment according to step 3.

[0060] The experimental results are:

[0061] (1) The waveform of each magnetic sensor in the circular magnetic sensor array has a similar change trend, that is, it suddenly increases first and then fluctuates irregularly, and finally the magnetic field disappears, the change decreases, and finally tends to be smooth and stable.

[0062] (2) The diversity of waveforms reflects the redundancy and complementarity of the information of the circular magnetic sensor array, and the real-time nature of the detection is reflected in the experiment.

[0063] (3) For the circular magnetic sensor array, when the welding point distance is 30mm, the characteristic value is 0.0903-0.2812; when the welding point distance is 60mm, the characteristic value is 0.0079-0.1316; when the welding point distance is 90mm, the characteristic value is 0.0923-0.0766. For a fixed center distance between the array and the welding point, the greater the welding current, the greater the characteristic value of the collected magnetic signal; for the same welding current, as the center distance increases, the characteristic value of the magnetic signal decreases.

[0064] The array works best when the standard distance is 60mm. For the annular magnetic sensor array, when the welding point distance is 60mm and the characteristic value is between 0.0829 and 0.1316, the molten core area is greater than 60%, so the weld quality is qualified.

[0065] The terms "first", "second", "third", "fourth", etc. (if any) in the specification of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0066] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for detecting the quality of aluminum alloy spot welding, characterized in that: The following steps are involved: S1, collecting magnetic field signals generated during the aluminum alloy spot welding process through a magnetic sensor array; S2, amplifying the magnetic field signal through a signal amplification circuit to obtain a magnetic field amplification signal; S3, extracting characteristic signals from the magnetic field amplification signal by principal component analysis; S4. Obtaining the aluminum alloy spot welding quality result according to the characteristic signal.

2. A method for detecting the quality of aluminum alloy spot welding according to claim 1, characterized in that: The specific method steps of collecting the magnetic field signal generated during the aluminum alloy spot welding process by the magnetic induction sensor array in step S1 are as follows: S11, select 4 magnetic sensors; S12, distributing the four magnetic sensors in a circular shape around the aluminum alloy spot welding area to collect magnetic field signals.

3. A method for detecting quality of aluminum alloy spot welding according to claim 1, characterized in that: The specific method steps for extracting characteristic signals from the magnetic field amplification signal by principal component analysis in step S3 are as follows: S31, performing standardization processing on the magnetic field amplification signal data to obtain a magnetic signal data matrix, and the magnetic signal data matrix is ​​still recorded as x; S32, calculating the covariance matrix R of the magnetic signal data matrix x XX ; S33, calculating the covariance matrix R XX The first n eigenvalues ​​of n , and its corresponding eigenvectors v1, v2, …, v n , where n is the number of principal components selected; S34, calculate the i-th principal component, and its calculation formula is: i =v i T x, i = 1, 2, ..., n, define the i-th principal component y i The variance contribution of is: The first n principal components y1, y2, ..., y n The cumulative variance contribution rate is According to the cumulative variance contribution rate, the characteristic signal is obtained.

4. A method for detecting the quality of aluminum alloy spot welding according to claim 3, characterized in that: In step S34, the specific method steps for obtaining the characteristic signal according to the cumulative variance contribution rate are as follows: S341, determining the eigenvalue of the number sample covariance of the principal component according to the cumulative contribution rate; S342, arranging the eigenvalues ​​from large to small, and extracting the principal components of the eigenvalues ​​that satisfy a threshold value greater than a preset threshold value to obtain a characteristic signal.

5. A method for detecting quality of aluminum alloy spot welding according to claim 2, characterized in that: The magnetic sensors are arranged around the aluminum alloy spot welding points, and the distance between each magnetic sensor and the aluminum alloy spot welding point is 30-90 mm.

6. A method for detecting quality of aluminum alloy spot welding according to claim 1, characterized in that: The magnetic sensor uses an indium antimonide magnetoresistor as a sensor probe.

7. The aluminum alloy spot welding quality inspection method according to claim 1, characterized in that: The specific method steps for obtaining the aluminum alloy spot welding quality result according to the characteristic signal in step S4 are: S41, acquiring the characteristic signal; S42, extracting the nugget area information in the characteristic signal; S43, comparing the extracted nugget area information with the standard nugget area to obtain the aluminum alloy spot welding quality result.

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