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摘要
This work describes the creation of an experimentally validated abrasive-grain cutting model using a hybrid Euler-Lagrange finite element formulation. This model was developed to better understand the micro-mechanical cutting that occurs during the grinding manufacturing operation. The model was developed in stages using the commercially available package LS-DYNA (R) with each stage undergoing experimental validation. Two cutting tool geometries were utilized to represent idealized abrasive grains that form a grinding wheel. A round-nosed tool was used to approximate the general size of abrasive grains and a flat-nosed tool was used to approximate the size and active cutting edge shape of abrasive grains. The development began with a simple spherical indentation model to test the feasibility of the numerical formulation, to determine essential contact parameters, and to verify an elastoplastic material model. The indentation model was then expanded to include relative motion between a round-nosed cutting tool and the workpiece using the same parameters that were identified with the indentation model. The round-nosed cutting model was used to determine the coefficient of friction between the tool and the workpiece. Analysis of the results from the round-nosed cutting model revealed that a plowed lip of plastically deformed material forms in front of the tool while a ridge of material forms on the sides of the residual groove as a result of flow around the tool. Subsurface stresses were shown to be more affected by depth of cut as compared to cutting speed. A case study showed that smaller abrasive grains produced lower overall forces and reduced the size of the subsurface stress fields; however, peak stresses were shown to increase slightly with decreasing grain size. Finally, a flat-nosed cutting tool was introduced in-place of the round-nosed tool to create a three-dimensional model of abrasive-grain cutting with chip formation. This finalized model incorporated all of the identified numerical parameters from the previous two development stages. The results revealed markedly different deformation and subsurface stresses. The workpiece material was shown to flow up the sides and around the cutting tool producing a continuous chip. Material thinning of the chip as it flowed around the tool demonstrated likely areas of crack formation, which may lead to discontinuous chip formation. The subsurface stresses were shown to be concentrated along a thin shear band at the root of the chip in accordance with metal cutting theory. Stresses below the flat-nosed cutting tool were shown to be below the yield stress of the workpiece material.
- 出版日期2012-6
