Johnson-Cook Damage Model Research Articles

A FEM study on mechanisms of discontinuous chip formation in hard machining

Chip types in machining are determined by the combined effects of workpiece material properties, cutting speed, and tool geometry. The understanding of chip formation plays an important role in machining process optimization and surface integrity. Discontinuous chips, one of the major chip types, are usually formed in hard machining at high speeds. In this study, a new method has been presented to simulate discontinuous chips in high-speed machining AISI 4340 (32 HRc). The workpiece material properties have been modeled using the Johnson–Cook (JC) plasticity model, and material crack formation and propagation simulated using the Johnson–Cook damage model. It has been shown that discontinuous chip is due to the internal crack initiation and propagation in front of the tool and above the cutting edge, rather than from the free surface. The simulated chip morphology correlated well with the experimental results.

Anisotropy-corrected MTS constitutive strength modeling in HY-100 steel

In this work, a microstructural-related model was developed to simulate micromachining of FCC polycrystalline copper. Indeed, a crystal plasticity framework was adopted to describe the anisotropy of the mechanical behavior. Some material microstructure characteristics (such as grain size, grain misorientation and crystallographic orientation) are explicitly considered through the constitutive model. For describing the material removal during chip formation, a modified thermodynamically consistent formulation of the Johnson-Cook damage model was used. The model was implemented in the ABAQUS/Explicit finite element solver with a user-defined subroutine, and the experimental validation was performed using data on the cutting forces available in the literature. Finally, the model was used to investigate the effect of the microstructure on the micro-machining cutting forces and chip formation process. According to the results, the proposed model allows capturing the cutting forces trends due to the crystallographic anisotropy.