DETERMINATION OF JOHNSON-COOK MATERIAL MODEL CONSTANTS FOR AISI 4340 HR BY METAL CUTTING

摘要

A novel experimental capability to measure the strain rate distribution is used to characterize the material behavior within the Primary Shear Zone (PSZ). A new method has been developed to compensate for the indentation component in machining to better estimate the flow stress along the PSZ. An evaluation of the Johnson-Cook material model constants available for hot rolled AISI 4340 has been carried out by comparing the outputs of finite element analysis (FEA) with outputs of cutting experiments. FEA with constants provided by Johnson and Cook [1983] for AISI 4340 at 30HRc overestimates the forces and the flow stress. A set of JC model constants obtained by fitting the model to flow stress data from cutting experiments indicates negligible work hardening. This model results in good prediction of shear angle and forces, but poor prediction of the strain rate in the PSZ implying the need for further improvement.