软性磨粒流加工方法及近壁区域特性

Softness abrasive flow machining and characteristics of near wall area

为了解决模具细微结构化表面难以光整加工的问题,提出固-液两相软性磨粒流(SAF)无工具精密加工方法.通过为结构化表面配以约束模块,以构建磨粒流湍流流道,利用软性磨粒流与被加工表面的"无缝"接触特性及壁面效应,实现模具表面的无工具无死角光整加工.以Nikuradse实验方法为理论依据,分析软性磨粒流中固体相在近壁区的运动学和力学特性,得到适用于软性磨粒流加工的摩擦系数公式.采用标准k-ε模型和欧拉多相流模型对软性磨粒流进行数学描述;利用压力耦合方程的半隐相容(SIMPLEC)算法,对不同入口速度时流道内的固体相压力分布进行数值分析研究.数值模拟结果表明,软性磨粒流固体相的压力衰减程度与入口速度成反比,并且固体相在流道内的运动轨迹呈无序状态.利用动态分析三维显示系统对流道内的颗粒运动轨迹进行实验研究.结果显示,固体颗粒运动轨迹呈无序漩涡状,符合湍流形态的运动规律.搭建软性磨粒流加工平台并进行加工实验.实验结果表明,采用软性磨粒流的加工方法能够使工件表面粗糙度达到61.8nm.

A new no-tools precision finishing method based on solid-liquid two phase softness abrasive flow （SAF） was proposed in order to solve the problem of tiny scale structural surface finishing in mould manufacturing course. Restrained flow passage was constructed by setting restrained component for the machined surface. Because the turbulent effect of SAF can seamlessly contact machining surface, no-tools precision machining for tiny scale structural surface can be realized. Motion regulars of SAF were analyzed according to the Nikuradse experimental method, and friction coefficient formulas which were suited for SAF machining were obtained. Standard κ-ε model and Euler multiple-phase model were used to make mathematical description of SAF, and flow passage pressure distribution with different inlet velocities was obtained by semi-implicit method for pressure linked equations consistent （SIMPLEC） algorithm. Numerical simulation results showed that the pressure attenuation of slid phase in flow passage was inversely proportional to inlet velocity, and motion trails of solid phase were disorderly and unsystematic. Particle motion trails were observed by dynamic analysis three-dimensional display system. Results of observation show that motion trails of solid phase are disorder vortexes, according with turbulent motion regularity. SAF experimental platform was constructed. Experimental results show that machined roughness of mould structural surface can be reduced to 61.8 nm.