纵扭超声铣削残余应力三维有限元仿真与试验

3D Finite Element Simulation and Experimentation of Residual Stress in Longitudinal Torsional Ultrasonic Assisted Milling

针对钛合金等航空难加工材料,提出采用纵扭复合超声振动辅助铣削的加工方法以实现压应力抗疲劳制造。根据侧铣-顺铣加工特性,基于热力耦合作用建立了钛合金铣削等效三维有限元仿真模型,有效提高了计算效率,实现了刀具作为载体的纵扭超声振动仿真。根据铣削残余应力的形成机理,通过机械应力和热应力的加载-释放,完成了加工残余应力的仿真。利用所建立的有限元模型,从切削力、切削温度以及加工残余应力角度出发,对比分析了传统铣削和纵扭超声铣削的差异性,得出纵扭超声振动能够有效降低切削力和切削温度,增大表面压应力值和压应力层深度。通过试验对纵扭超声铣削等效模型进行了验证,结果表明所建立的三维有限元模型能够以较高的精度对切削力、切削温度和加工残余应力进行预测;进一步通过数值模拟研究了刀具几何参数以及超声表征参数对加工残余应力的影响规律,为实现钛合金的压应力制造奠定了基础。

In view of the difficult-to-cut materials such as titanium alloy, the machining method of longitudinal torsion ultrasonic vibration assisted milling (L-TUM) is put forward to realize the anti-fatigue manufacturing. Firstly, the milling process is converted to the oblique cutting model, and a 3D FEM equivalent model of L-TUM is established, it effectively improved the computation efficiency and realized longitudinal torsional ultrasonic vibration and cutting process compound. According to the formation mechanism of the machining induced residual stress (RS), through mechanical and thermal stress loaded and released, the simulation of RS is realized. Then, the difference between the traditional milling and L-TUM is compared from the cutting force, the cutting temperature and the machining induced residual stress, it is concluded that cutting force and temperature are reduced, surface compressive stress and compressive stress layer depth are increased in L-TUM. The experiments are carried out to verify the equivalent model of L-TUM, the results show that the 3D model predicts cutting force, cutting temperature and residual stress with high precision. The influence of tool geometry parameters and ultrasonic characterization parameters on machining residual stress is studied by FEM, It lays a foundation for the compressive stress manufacture of titanium alloy's.