| With the improvement of modern living standards,the scale of cities is also expanding,and rail transit has become an important means of transportation to solve urban traffic problems.Therefore,in recent years,rail transit in my country has been showing a trend of rapid growth.Stainless steel rail passenger car has become one of the key urban rail vehicles for its high safety,full life cycle,low cost and light weight.The thin-plate assembly welding structure is the main component of the stainless steel body,and the resistance spot welding process in welding has the advantages of simple operation,easy automation,and high productivity,and is widely used in the field of rail passenger car manufacturing.Stainless steel car bodies often used by people usually have tens of thousands of spot welding spots,so resistance spot welding plays an extremely important role in the welding and manufacturing of stainless steel car bodies,and the quality of welding will also affect the manufacturing quality and the quality of welding can also affect the build quality and safety of the body.Therefore,it is very critical to effectively detect and evaluate the quality of spot welding.Since the welding spot of resistance spot welding exists inside the lapped sheet,it is difficult to quickly and accurately judge the welding quality by the appearance state.At present,the quality assessment of resistance spot welding mainly includes real-time monitoring of welding parameters and non-destructive testing and destructive testing after welding.Among them,the real-time monitoring of welding parameters is widely used in production sites due to its real-time and non-destructive characteristics.Monitoring parameters commonly used for quality assessment generally include direct welding parameters such as current,voltage,and interpolar pressure,and indirect welding parameters such as dynamic resistance.Commonly used post-weld non-destructive testing methods mainly include radiographic testing,laser displacement ranging,ultrasonic testing,etc.However,due to the limitations of testing methods or testing conditions,these testing methods are difficult to evaluate the quality of spot welded joints with high efficiency and high proportion.ground detection.Therefore,finding an automatic and high-efficiency method for spot welding quality assessment is of great significance for the realization of comprehensive automatic detection and online quality assessment of spot welding.In this paper,a certain number of dynamic resistance curves of spot welding joints are extracted to form a dynamic resistance curve group,and an online evaluation model of spot welding quality that can be automatically updated is established according to the dynamic resistance curve group and the dynamic time bending algorithm.The model can automatically judge whether the dynamic resistance curve of the spot welded joint to be tested is within the threshold range of the established model,so as to complete the evaluation of the quality of the spot welded joint.In this paper,the size of the nugget of spot welding is measured by ultrasonic,and the size of the pit is measured by the laser displacement sensor,so as to verify the established model.The results of these two tests show that the evaluation model of spot welding quality established in this paper is more accurate for evaluating the quality of spot welding joints. |
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