In-situ Evaluation of Surface Integrity Modifications by means of Barkhausen Noise Measurement

Abstract

The quality and functionality of machined parts depend on their dimensional tolerance as well as on the mechanical properties of the workpiece rim zone, which are summarized as surface integrity. Thermo-mechanical loads induced by the cutting process into the rim zone often lead to an undesirable workpiece material modification. Over the last decades, many researches focused on the process monitoring of properties of the rim zone, such as the grain size or the residual stress profile. In order to prevent damage to the workpiece material, non-destructive and magnetic measurement methods are to be favored when machining ferromagnetic workpiece materials. Due to its sensitivity to the microstructural properties of ferromagnetic materials, Barkhausen Noise (BHN) measurement offers the potential for in process monitoring. In particular, BHN shows a strong correlation with the residual stress state of the workpiece material and thus the direct obtainment of BHN signals in the cutting process enables the in-situ modelling of residual stress changes in the rim zone.In this paper, two BHN measurement test benches were developed in order to investigate a first correlation between process parameters, measuring conditions and resulting BHN signals when machining quenched and tempered AISI 4140 steel. Furthermore, a first correlation between residual stress states and BHN signals obtained in the orthogonal cutting process is presented.