三、封头拉伸的压边条件封头的拉伸分为带有压边圈的和不用压边圈的两种形式。在什么条件下需要压边,又在什么条件下不需要压边,这要从封头冲压时的应力和应变情况来分析。 (一)封头拉伸时的应力及应交封头毛坯拉伸时,凸缘部分的环状毛坯受到径向的拉应力及切向的压应力,如图12所 Third, the first stretch of the blank holder conditions Head tension is divided into blank holder with and without blank holder two forms. Under what conditions need to press the edge, under what conditions do not need to press the edge, which should be from the head stamping stress and strain analysis. (A) the stress when the head is stretched and should be submitted to head blank stretch, the flange portion of the ring blank by the radial tensile stress and tangential compressive stress, as shown in Figure 12