螺纹短收尾表面折叠形成机理及滚压工艺参数仿真

The bolts with short end thread are widely used in the aerospace industry due to their advantages of compact structure,light weight,and reliable connection. However,during the processing of bolt,the end area is prone to producing folding defect,which seriously affects the fatigue life of the bolt. Therefore,it is necessary to conduct research on the mechanism of surface folding formation and the influence of process parameters on the short end of threads. Firstly,a numerical simulation model with finite element was established on the thread and its end rolling process,and the forming process of short end folding defects was analyzed. Correspondingly,the folding formation mechanism was revealed. Afterwards,the influence of the effect of the end rolling process on the folding size was explored,and a mathematical regression model was constructed between rolling process parameter and folding size. The rolling process parameters were also optimized. The research results indicate that the surface folding of short end threads mainly occurs in the later stage of bolt processing,which is caused by the extrusion effect of the end rolling wheel on the transition area of the thread end-arc region in bolt. As the processing progresses,the thickness of the transition area becomes smaller and the material undergoes severe deformation,which can further lead to the aggravation of folding defects. Based on the mathematical model between rolling process parameter and folding size,it is indicated that the feed rate impacts most significantly the folding size. And as the folding size increases,the final folding shows a variation tendency of first decreasing and then increasing.