由弯曲应力引起的疲劳破坏在反挤凸模上经常发生。本文分析了弯曲应力与疲劳寿命的关系,井根据凸模弯曲应力与挤压件壁厚差成正比的试验结果,得出挤压件壁厚差与凸模疲劳寿命的定性关系,指出减小壁厚差不仅可以提高挤压仟的形位精度,而且可以提高凸模的使用寿命。文中还叙述了为减小壁厚差在模具方面应该采取的措施。 Fatigue failure caused by bending stress often occurs on anti-extrusion dies. In this paper, the relationship between bending stress and fatigue life is analyzed. According to the test results that the bending stress of punch is proportional to the difference of wall thickness of extrusion, the qualitative relationship between wall thickness difference and fatigue life of punch is obtained, The difference in wall thickness not only improves the form accuracy of the extrusion but also improves the service life of the punch. The article also describes the measures to be taken to reduce the mold thickness in poor wall thickness.