The effects of stacking fault energy and hardness on the shear process during low-speed orthogonal metal cutting were examined in a designed experiment of 1680 tests in Copper Zinc (CU-ZN) alloys. Existing shear zone models were compared to the experimental results generated by a Videographic Quick Stop method.
Analysis of the data indicates that the onset of shear plane is more properly viewed as the activation of glide plane. This in turn is a result of the available slip planes, which are a function of the materials crystalline structure, the stacking fault energy and the dislocation density (i.e., the amount of work-hardening), as constrained by the tool’s rake face angle. Merchant’s Force Diagram is revised using an extension of the existing diagram to incorporate the material’s crystalline structure, incorporating well established dislocation theory.