CN-121980789-A - Quantitative evaluation and global parameter optimization method for quality of aluminum and steel resistance spot welding spots

Abstract

The invention discloses a method for quantitatively evaluating quality of welding spots of aluminum and steel resistance spot welding and optimizing global parameters, which comprises the following steps of S1 experimental design, S2) orthogonal experimental design, S2 data acquisition, S3 welding spot quality quantitative evaluation calculation, 1) data normalization, 2) gray correlation coefficient calculation on normalized data, 3) calculation on a gray correlation coefficient matrix to obtain a correlation coefficient matrix, 4) calculation of characteristic values and characteristic vectors of the correlation coefficient matrix, 5) selection of one or more main components with characteristic values larger than 1 according to Kaiser rule, calculation of weight coefficients of the characteristic vectors corresponding to the main components, 6) calculation of comprehensive quantitative quality indexes by combining the weight coefficients of key indexes of each welding spot and the gray correlation coefficients corresponding to the key indexes, S4 prediction of optimal welding parameter combination, and S5 parameter optimization. The invention realizes the accurate quantification of the quality of the aluminum and steel resistance spot welding spot and the scientific global optimization of the technological parameters.

Inventors

• ZHOU KANG
• CHEN JINMENG
• YU WENXIAO

Assignees

• 北京理工大学

Dates

Publication Date

20260505

Application Date

20260122

Claims (9)

1. 1. The quantitative evaluation and global parameter optimization method for the quality of the aluminum and steel resistance spot welding spots is characterized by comprising the following steps of: s1, experimental design: 1) Setting welding parameters, wherein the welding parameters comprise welding current, welding time and electrode pressure; 2) The orthogonal test design is that an orthogonal test method is adopted to study the influence of different welding parameter combinations on the quality of welding spots; S2, data acquisition: Selecting 8 key indexes of aluminum nugget diameter, steel nugget diameter, aluminum surface indentation, steel side elevation height, peak shearing force, failure energy and welding energy as key indexes for calculating comprehensive quantitative quality indexes of welding spots; s3, quantitatively evaluating and calculating the quality of welding spots: 1) Normalizing the data; 2) Carrying out gray correlation coefficient calculation on the normalized data; 3) Calculating a gray correlation coefficient matrix to obtain a correlation coefficient matrix; 4) Calculating the eigenvalue and eigenvector of the correlation coefficient matrix; 5) According to Kaiser rule, selecting a feature value larger than 1 as a main component, and calculating weight coefficients of the feature vectors corresponding to 1 or more main components; 6) Multiplying the weight coefficient of each welding spot key index by the corresponding gray correlation coefficient, and then adding the products to finally obtain a comprehensive quantization quality index to finish the comprehensive quantization evaluation of the welding spots; s4, predicting an optimal welding parameter combination: Calculating the average value of the comprehensive quantitative quality indexes of each factor of welding time, welding current and electrode pressure and the corresponding range thereof by using a range analysis method so as to determine the primary and secondary sequences of the influence of each factor on the welding quality and determine the optimal parameter combination; s5, optimizing parameters: firstly, a relation model between welding parameters and welding spot comprehensive quantization quality indexes is constructed by adopting a natural neighborhood interpolation method, and then parameter optimization is carried out on the target model through a genetic algorithm.
2. 2. The method for quantitatively evaluating quality of aluminum and steel resistance spot welds and optimizing global parameters according to claim 1, wherein in step S1, the orthogonal test method is specifically based on L 16 (4 3 ) orthogonal table for performing 16 groups of experiments with 3 factors and 4 levels.
3. 3. The quantitative evaluation and global parameter optimization method for the quality of the aluminum and steel resistance spot welding spots according to claim 1 is characterized in that in the step S2, aluminum nugget diameter, steel nugget diameter, aluminum surface indentation, steel surface indentation and steel side elevation height indexes are obtained through metallographic experiments, peak shearing force of the welding spots is obtained according to a shearing force-displacement curve, failure energy of the welding spots is calculated by an area surrounded by the shearing force-displacement curve and an x-axis, welding energy is calculated by measuring electrode voltage and welding current in a welding process on line, a welding power curve is obtained, and the welding power curve is calculated by the area surrounded by the x-axis.
4. 4. The method for quantitatively evaluating quality of aluminum and steel resistance spot welding spots and optimizing global parameters according to claim 1, wherein in step S3, the data normalization is specifically calculated by using the following two formulas according to the characteristics of index data: Wherein x i (k) is data to be normalized, y i (k) is a normalized value of x i (k), max x (k) and min x (k) are a maximum value and a minimum value of x i (k) respectively, i is an orthogonal test number, and k is 8 key indexes.
5. 5. The method for quantitative evaluation and global parameter optimization of aluminum and steel resistance spot welding quality according to claim 4, wherein in step S3, the gray correlation coefficient calculation formula is as follows: Wherein, delta i (k) is a deviation sequence, X i (k) is a comparison sequence, X 0 (k) is a reference sequence, ζ i (k) is a gray correlation coefficient, delta min and delta max are respectively the minimum value and the maximum value of delta i (k), the value range is 0-1, rho is a resolution coefficient, and is set to 0.5, and after all the zeta values are calculated, a gray correlation coefficient matrix of 16×8 is formed.
6. 6. The method for quantitatively evaluating quality and optimizing global parameters of aluminum and steel resistance spot welds according to claim 5, wherein in step S3, for the selected 8 key indexes, the correlation coefficients are calculated according to the following calculation formula: Wherein Cov (X, Y) is the covariance of any two selected key indexes, X, Y is any two columns of a gray correlation coefficient matrix, X i 、y i respectively represents the ith value in the X column and the ith value in the Y column, n is the experiment number, As the mean value of the variable X, For the average value of the variable Y, sigma x is the standard deviation of the variable X, sigma y is the standard deviation of the variable Y, corr (X, Y) is the correlation coefficient of any two selected key indexes, and after the correlation coefficient of any two key indexes is obtained, an 8X 8 correlation coefficient matrix is constructed.
7. 7. The method for quantitatively evaluating quality of aluminum and steel resistance spot welds and optimizing global parameters according to claim 6, wherein in step S3, the calculation formula of eigenvalues and eigenvectors of the correlation coefficient matrix is as follows: Where a is the correlation coefficient matrix in the previous step, λ is the set of eigenvalues, I is the identity matrix, v k is the eigenvector corresponding to the eigenvalue λ k .
8. 8. The method for quantitatively evaluating quality of aluminum and steel resistance spot welds and optimizing global parameters according to claim 2, wherein in step S3, the weight coefficient calculation formula of the feature vector corresponding to the main component is as follows: Wherein W is a weight coefficient vector of 8 key indexes, C k is a decision coefficient, C k =λ k /n, and t is the number of principal components selected for evaluating the weight coefficient.
9. 9. The method for quantitatively evaluating quality of aluminum and steel resistance spot welds and optimizing global parameters according to claim 8, wherein in step S3, the comprehensive quality index calculation formula is as follows: wherein, beta (i) is the comprehensive quality index corresponding to the ith group of experiments, m is the number of key indexes, and the value of the key indexes is equal to 8.

Description

Quantitative evaluation and global parameter optimization method for quality of aluminum and steel resistance spot welding spots Technical Field The invention relates to the technical field of welding, in particular to a method for quantitatively evaluating quality of a resistance spot welding spot of aluminum and steel and optimizing global parameters. Background Currently, the automobile industry is accelerating to develop in the directions of energy conservation, emission reduction and comprehensive performance improvement, and the lightweight manufacturing of automobiles is one of the core technical paths for achieving the aim. In an automobile lightweight material system, aluminum alloy relies on the characteristics of low density and high specific strength, and high-strength steel depends on excellent impact resistance, so that the composite structure formed by the aluminum alloy and the high-strength steel can greatly reduce the weight of the whole automobile on the premise of ensuring the safety performance of the automobile body, and is widely applied to the manufacture of the automobile body. In the automobile body production process, the resistance spot welding process has the outstanding advantages of high production efficiency, simple operation flow, easy adaptation with an automatic production line and the like, and has long been the mainstream technical means for connecting automobile body metal components. When the process is adopted to connect the aluminum alloy and the high-strength steel, the process can be directly compatible with equipment and flow of the existing automobile production line, the large-scale production line transformation is not needed, and the industrialized application cost of dissimilar metal connection is obviously reduced, so that the research and optimization of the aluminum and steel resistance spot welding technology has important engineering value for promoting the automobile to be light and land. But the physical and chemical properties of the aluminum alloy and the high-strength steel have obvious differences that the heat conductivity coefficient of the aluminum alloy is about five times that of the steel, the melting temperature is less than half that of the steel, and the thermal expansion coefficient is about twice that of the steel, so that the aluminum and the steel have uneven temperature distribution and complex metal melting behavior in the resistance spot welding process, and finally the formed welding spot has special morphological characteristics of a double-nugget structure, asymmetric surface indentation, steel side bulge and the like. Under the influence of the influence, the traditional welding quality evaluation depends on a single physical quantity (such as nugget diameter), cannot fully cover the nugget size, mechanical property (peak shearing force), geometric morphology (indentation depth, steel side bump height) and other multidimensional indexes, so that the quality of an aluminum welding spot and a steel welding spot is difficult to realize accurate quantification, the comprehensive performance of the welding spot cannot be systematically evaluated, and quantitative association of technological parameters and quality is difficult to establish, thereby restricting the reliable application of the aluminum and steel resistance spot welding technology in the lightweight manufacturing of automobiles. For example, in the prior art, application number 202310698037.5 discloses a method and a system for evaluating the quality of resistance spot welding of an automobile body part, and dynamic resistance data is obtained by analyzing voltage and current data corresponding to different welding spots, wherein a light-weight one-dimensional convolutional neural network model is built as a spot welding quality evaluation model, and data to be tested is input into the spot welding quality evaluation model after training and optimization to obtain a corresponding spot welding quality evaluation result. But has problems in that 1) model training is performed only by single dynamic resistance data, other welding data are not considered, 2) quantitative evaluation of welding quality is not performed, and 3) optimization of welding parameters is not performed. Therefore, providing a comprehensive and accurate quantitative evaluation and global parameter optimization method for quality of aluminum and steel resistance spot welds is a problem that needs to be solved by those skilled in the art. Disclosure of Invention In view of the above, the invention provides a quantitative evaluation and global parameter optimization method for quality of aluminum and steel resistance spot welding spots, which can integrate multidimensional indexes, effectively process complex correlations among multidimensional quality indexes caused by obvious differences of physical and chemical properties of aluminum and steel materials, objectively determine influence weights of all