Analytical analysis of the mechanism of effects of machining parameter and tool parameter on residual stress based on multivariable decoupling method

Abstract

Generation of machining residual stress is affected by various variables, such as workpiece material, machining parameter and tool parameter. In this paper, these variables are decoupled into fundamental variables, including thermal conductivity, cutting force, friction coefficient on tool flank, shear angle, width of cut, length of tool flank wear, uncut chip thickness, rake angle and cutting speed. In order to reveal the mechanism of effects of machining parameter and tool parameter on residual stress, firstly, analytical model of residual stress was used to investigate independent effect of each fundamental variable on residual stress, to obtain the tendency of residual stress variation along with each fundamental variable; secondly, tendencies of residual stress variation along with different fundamental variables were compared, in order to reveal dominant physical approach of fundamental variables to affect residual stress; finally, physical mechanism of fundamental variables on residual stress were used to explain those of machining parameter and tool parameter on residual stress. The analysis results show that: (1) depth of highest compressive residual stress increases with the increase of feed rate, and decreases with the increase of cutting speed, this is because heating time increases with the increase of feed rate, and decreases with the increase of cutting speed; (2) more tensile residual stresses in machined surface layer generates along with the increase of tool flank wear, this is caused by the increase of length of tool flank wear and friction coefficient on tool flank; (3) residual stress amplitude increases with the increase of rake angle, this is because cutting force increase with the decrease of rake angle; also, depth of highest compressive residual stress increase with the decrease of rake angle, this is because shear angle decrease with the decrease of rake angle which further cause the increase of heating time.