Residual stresses in milled titanium parts

Abstract

Residual stresses can cause part distortion especially in the case of large components such as structural parts in aerospace industry. Therefore, this paper investigates the machining induced residual stresses for milling of a workpiece material with increasing usage in industry, titanium. For stress determination a practical modification of an indirect measuring method, the layer removal method, is applied, as it can offer advantages compared to X-ray-measurements. It is robust against material properties such as grain size or texture which can complicate the X-ray-method. Afterwards two typical machining processes, face milling and peripheral milling are investigated regarding residual stress. A correlation between process forces and value and depth of the induced stresses is identified by a variation of feed per tooth and the tool geometry by means of usage of a worn tool. Increasing cutting speed leads to increased penetration depth in case of face milling and did not exhibit strong influence on the end milled subsurface.