航空框类零件加工动态夹紧力确定有限元分析

Finite element analysis for the verification of the dynamic clamping force during machining of the aero frame shape workpiece

针对目前航空框类零件加工中夹紧力的确定主要凭经验,加工变形难以控制的难题,采用有限元数值计算方法,通过相应模型的建立和求解,揭示摩擦力及切屑去除对夹紧力确定的影响,以降低夹紧力对工件加工变形的影响.在有限元模型中利用生死单元技术模拟切屑去除;用弹簧和阻尼单元表示工件与夹具的接触,确定工件在动态载荷作用下的夹紧力.研究结果表明,随着刀具位置不同,夹具与工件接触处反力也随之发生变化,为保证工件的定位基准及减小工件的变形应根据刀具位置的不同及工件刚度的变化不断调整夹紧力.

At present the verification of clamping force is mainly based on experience during machining the aero frame shape workpiece, which often results in distortion of the workpiece. An FEA （Finite Element Analysis） model is developed to reflect the influence of friction and chip removal on the clamping force verification. The chip removal effect is simulated using an element death technique based material removal approach in the FEA model. Spring and damper elements are used to represent every point, where the fixtures contact with the work piece. The clamping force of the work-piece is determined under the effects of dynamic loading. Simulation results show that the nonnal force on the contact area changes with the cutter＇s movement. The clamping force must be adjusted during machining, in order to reduce the workpiece distortion and to ensure the accurate work piece location.