Investigation of Prestress Hard Turning of 40Cr Steel

Abstract

Hard turning is a method for precision part production of hardened materials used instead of grinding. Some reports show the prestress machining can improve the residual stress state of machined surface and fatigue life of mechanical part. The purpose of this article is to obtain a comprehensive understanding about the influence of prestress hard turning of hardened alloy 40Cr on stress state and topography of machined surface. The measured data of cutting force show prestress would affect feed force but not on cutting and thrust forces. The chip morphology appears saw-tooth formation by applying different prestress. When prestress load increases, residual compressive stress on machined surface will increase in the feed direction and decrease a little in the cutting direction. Experimental results show that the machined workpiece gains a good surface finish and the value of surface finish will worsen by applying prestress, but will have no change when prestress load changes. On the other hand, it is possible to increase residual compressive stress levels by prestress hard turning.

Keywords:

• Chip morphology
• Cutting force
• Prestress hard cutting
• Residual stress
• Surface topography