软性磨粒流磨粒入射壁面过程及其加工特性研究

针对利用两相流模型无法计算高浓度固—液两相流固相颗粒撞击壁面时颗粒速度的问题,提出一种边界层内颗粒运动轨迹计算模型,基于Mixture两相流模型和Realizable k-ε湍流模型仿真计算结果,通过分析提取颗粒入射前速度、计算边界层厚度、建立边界层内速度场和颗粒运动分析可以得到颗粒撞击壁面时的速度和入射角度。分析加工表面动压力分布和磨粒体积分数分布,结合两种结构约束流道验证仿真结果与加工效果的对应关系。通过对试验结果的分析,为约束模块的设计提供依据。研究结果表明:磨粒入射速度、磨粒体积分数和加工表面所受动压力大小直接影响工件加工效果,并与材料去除量成正相关关系;在本次试验中选择的工艺参数导致加工材料去除量小,适合初始粗糙度低的工件表面加工,对于此次试验的初始粗糙度应在0.2μm以下;约束模块的设计除了要考虑磨粒流流场特性之外,还要对加工表面的原始加工痕迹作详细了解,为约束模块的设计及加工工艺参数提供参考。

Research of Abrasive Injection Process to the Wall and Machining Characteristic of Soft Abrasive Flow Machining

To solve the problem of unable to calculate particle velocity of high concentrate solid-liquid two-phase flow when impacting wall,a model which simulates particle movement locus in boundary layer is proposed.Based on results simulated by mixture model and realizable k-ε model,velocity and angle of incidence can be calculated through analyzing particle velocity before incidence,calculating boundary layer thickness,establishing velocity field in boundary layer and solving particle motion function.Distribution of dynamic pressure and volume fraction of abrasive on the workpiece’s surface is analyzed associated with two kinds of flow passage with different restrained components.Experimental results are analyzed to get design law for restrained component.Research results indicate that machining is directly affected by incidence velocity of abrasive,volume fraction of abrasive and dynamic pressure on surface of workpiece,which are positive correlation with material removal rate.Initial degree of roughness should be below 0.2 μm employing machining parameters.Initial machining track should be checked before design restrained component beside consider characteristic of flow field.