基于数值模拟的局部变过盈量组合凹模研究

Research on combined die with local changeable interference based on numerical simulation

借助有限元软件分析了预紧力状态下,采用均匀变过盈量设计的组合凹模能有效减小消气带区齿根的切向压应力,以避免线切割时模具的破损,但模芯成形区齿根的切向压应力也相应减小,无法完全抵消挤压时在成形区产生的拉应力,从而影响了模具的使用寿命。为解决这一问题,提出局部变过盈量组合凹模的设计方法,即在模芯上部采用均匀过盈量,下部采用变过盈量的设计,以保证预紧状态下模芯成形区齿根切向压应力不被减小,而只减小消气带齿根的切向压应力,有效提高了模具寿命。以模数m=4的某齿轮为研究对象,通过数值模拟,确定了锥角γ″=1°,γ'''=1.2°,均匀过盈量区高度h=21 mm等参数进行实际生产,与均匀变过盈量模具寿命相比,提高了35%左右。

The combined die with uniform changeable interference under the preload condition was designed by the finite element software. This combined die could effectively reduce tangential compressive stress of gear root in the getter zone to avoid the die damage with wire cutting. But the tangential compressive stress of gear root in forming zone of die core reduced accordingly,which could not fully offset the tensile stress during extrusion forming,and the die life was affected. In order to solve this problem,the design method of local changeable interference on combination die was put forward,namely,uniform interference was applied on the upper part of die core,while changeable interference was used on the lower part of die core. Therefore,the tangential compressive stress of gear root in forming zone of die core under the preload condition was not reduced,and the tangential compressive stress of gear root in the getter zone was only decreased to improve the die life. Furthermore,for the gear with modulus of 4,the cone angle γ″ = 1° and γ＇″ = 1. 2° as well as the height21 mm of uniform interference zone were determined respectively by numerical analysis,and the actual production was carried out. Thus,for the combined die with uniform changeable interference,the die life was prolonged by obout 35%.