Strain is a physical quantity indicating the size of deformation, the accumulation process of plastic deformation and the development process of plastic deformation. Figures (a), (b), (c) and (d) show the distribution of equivalent effect variation of spiral bevel gear blank metal when simulating steps 40, 50, 60 and 73 respectively. In the initial stage of deformation, that is, when the punch tooth top just contacts the blank, the upper part of the spiral bevel gear blank is deformed into free upsetting deformation. The lower part of the blank of spiral bevel gear is restrained by the die and does not deform, as shown in figure (a).
As the upper die goes down, the height of the spiral bevel gear blank decreases, the diameter increases, and the metal continues to flow around. Due to the friction between the spiral bevel gear blank and the upper and lower dies, the spiral bevel gear blank will form a drum shape after upsetting, resulting in uneven distribution of internal deformation of the blank. It can be seen from the equal effect deformation distribution diagram of the spiral bevel gear blank by numerical simulation that the deformation area of the spiral bevel gear blank can be divided into two areas, large deformation area and small deformation area, as shown in figure (b). The contact part between the punch teeth and the blank of the spiral bevel gear is a stress concentration area in the deformation. The variation value of the equal effect here is larger than that elsewhere, and the punch has a greater effect on hindering the radial flow of the blank of the spiral bevel gear, belonging to the large deformation area. At the same time, because the size of the lower end of the spiral bevel gear blank is basically the same as that of the female die, there is basically no deformation at the lower end and middle of the spiral bevel gear blank. It can be seen from figures (a), (b), (c) and (d) that its equivalent effect variation is close to 0, belonging to the small deformation area. When metal is filled from the tooth root to the tooth cavity, it is mainly radial strain. At the same time, due to the existence of spiral angle of spiral bevel gear, there is also tangential strain.