Response Surface Optimization Research Of Ultrasonic Array Detection Process For Weld Defects Of Aluminum Alloy Structure

Due to the influence of welding structure,welding process and external load,there will inevitably be quality defects in welds,which will lead to potential safety hazards.Ultrasonic phased array inspection technology is widely used in the quality inspection of weld structure because of its advantages of dynamic focusing of sound beam,wide inspection range and intuitive display of defects.However,because ultrasonic phased array inspection parameters involve many and there may be interactions among them,the rationality of parameter setting is very important for the quality of defect inspection.Screening testing parameters that have significant influence on defect testing results,optimizing testing process settings and improving defect imaging quality have become academic research hotspots.In this thesis,aiming at this goal,the optimization of ultrasonic phased array detection process parameters for defects in aluminum alloy weld area is studied.The specific research contents are as follows:(1)In order to explore the sound field distribution and response ability to defect detection when the detection parameters of ultrasonic phased array in aluminum alloy materials are changed,the sound field model of one-dimensional linear array probe is established with the help of the simulation software CIVA.On this basis,the sound field simulation of ultrasonic phased array probe frequency,array element number,array element excitation position,focusing depth and probe geometry parameters is carried out with the focus width,focal length and focus energy amplitude as evaluation indexes.The characteristics of sound field distribution under different parameter settings are analyzed.Secondly,the response analysis of round hole defects in aluminum alloy materials is carried out,which provides a theoretical basis for the subsequent optimization of phased array detection process parameters.(2)On the basis of understanding the working principle of ultrasonic phased array detection technology,the optimization objectives and experimental variables of ultrasonic phased array detection are determined.According to the horizontal range of each experimental variable,the experimental design is carried out by Box-Behnken experimental design method,and three-dimensional modeling of components and welds is carried out with the help of CIVA simulation software,and the peak-valley decibel difference and quantitative size data of defects under different parameter combinations are obtained,thus providing basic optimization data for the establishment of optimization model.(3)The least square method is used to fit the experimental data of decibel difference between peak and valley and quantitative size error of defects respectively,and the highorder optimization function model of them is established,and the significance test and variance analysis are carried out to further verify the reliability of the model.On this basis,three-dimensional response surface maps and two-dimensional contour maps of different process parameters are drawn respectively,and the influence of interaction on response variables under different process parameter combinations is further analyzed,and the optimal interval of each process parameter is also analyzed.(4)The design-Expert software is used to solve the joint solution of the resolution model and the defect sizing model,and the optimal combination of parameters to meet the requirements of both is: the probe center frequency is 14.75 MHz,the number of arrays is51.673,and the focus depth is 39.627 mm.The distance between the probe and the weld front is 5.112 mm,the predicted value of the amplitude difference between the crests and troughs under this parameter combination is 14.175 d B,and the prediction value of the defect size measurement error is 0.01 mm,and the model prediction results and simulation results are compared under the optimal parameter combination,so as to verify the correctness of the model.(5)The optimized results of ultrasonic phased array detection process parameters are verified by experiments.According to the results of response surface analysis and the operable conditions in the laboratory,under the condition that the central frequency of the probe is fixed,the process parameter combination of the best interval is selected to detect the weld defects,and then the accuracy of the predicted results of the model is verified.