Movement patterns of ellipsoidal particle in abrasive flow machining

Abrasive particle movement pattern is an important factor in estimating the wear rate of materials, especially, as it is closely related to the burring, buffing and polishing efficiency of the abrasive flow machining (AFM) process. There are generally two kinds of particle movement patterns in the AFM process, i.e. sliding–rubbing and rolling. In mechanism, AFM particle–workpiece interaction is taking place in any one or a combination of the possible modes: elastic/plastic deformation by grooving particle movement; elastic/plastic deformation by rolling particle movement; chip formation (micro-cutting) by grooving particle movement, ridge formation by grooving and rolling particle movement, and low-cycle fatigue wear. Grooving particle movement pattern has a greater contribution to wear mass loss of workpiece than rolling mode. Considering the machining efficiency of a machine part is predominantly dependent upon its wear mass loss speed, it can be concluded that particle movement patterns are key parameters to machining efficiency in AFM. In this paper, ellipsoidal particles are investigated to understand particle movement patterns. An analytical model of ellipsoidal geometry to determine particle movement patterns in AFM is proposed with given particle ellipticity, normal load, particle size and material hardness. From the analytical model and particle movement pattern criterion proposed by the present authors, a statistic prediction of particle movement patterns is completed by computer programmed by C++ language. It is found that a seat position of ellipsoid is an easy grooving position for a particle and a large ellipticity value predominantly increases grooving particle numbers. Smaller workpiece hardness, larger particle radius and higher normal load promote grooving of the particles. Sharper particles are much more easy to groove; moreover, grooving pattern will be predominant if particle ellipticity is below 0.8. Increasing workpiece hardness tends to decrease grooving regime while other parameters are fixed in AFM process. In three-body abrasion, hard material paired with soft material will result in more rolling particles. Abrasive contour and material hardness in many variables are two predominant parameters to give distinct influence on particle movement pattern.