Numerical-experimental study on the mechanisms of material removal during magnetic abrasive finishing of brittle materials using extended finite element method

摘要

Magnetic abrasive finishing (MAF) is an advanced machining process efficiently used for finishing of hard-to-machine materials. In this method, material removal takes place through nano-/microindentations in the presence of a controllable magnetic field generated via a permanent or an electronic magnet. Understanding the material removal mechanisms of the process is of particular importance for achievement of a high-quality surface with minimum surface defects. Therefore, in this work a numerical-experimental study was performed toward this issue using the extended finite element method (X-FEM). In this regard, the MAF operation was simulated as an indentation and sliding process of a sharp abrasive and the prevailing material removal mechanisms were obtained during MAF of BK7 optical glass. The constitutive material model for the specimen was defined according to the elastic-plastic-cracking model, which takes into account the tensile cracking and compressive yielding behavior of brittle materials. The X-FEM analysis revealed that both microcutting and microfracture mechanisms exist during MAF process of brittle materials depending on the process parameters. Among various parameters, magnetic particles size and abrasives size were the most influential factors affecting the dominant mechanism of material removal. The obtained numerical results were then validated experimentally by using scanning electron microscopy (SEM). The SEM observations revealed good performance of X-FEM analysis in prediction of material removal mechanisms during MAF of brittle materials.