The stress distribution of the necking part in the tensile specimen of ductile material is very important for understanding the essence of fracture,but there is still not a well-accepted theory that could interpret the reason for the occurrence of necking and the solution of stress field in the necking part currently,which brings the inconvenience to practical application.In this article,the uniaxial tension tests of three common metal materials including Q235 steel,14CrNiMoV alloy steel,and LY12 aluminium ...