Application of Hall effect for assessing grinding thermal damage

The limitations of the usual techniques applied for gear grinding burn detection are extended by the increasing demands on quality control within industrial feasibility. Although widely used, nital etching technique has a subjective character. Alternative techniques such as magnetic Barkhausen noise and X-ray diffractometry also present drawbacks such as variability of output based on external energy input that depends on parameter settings, high cost and destruction of tests parts. Due to this technical gap, an alternative method is suggested, where the remanent induction of a workpiece is measured by means of a Hall probe. The objective of this concept is to reduce external inputs on the workpiece, measuring its natural signal and correlating it to the material property induced by the damage. In this study, three different degrees of damage were investigated with the Hall method, covering damages with phase transformation as well as with modifications on the residual stress state. According to the results obtained, an alteration in the remanent induction which is directly correlated to the burn degree, was detected. The micro-magnetic theory establishes a correlation between the remanent magnetic induction and material hardness as well as residual stress state. The signal alteration detected by the Hall method is in accordance with the micro-magnetic theory for all three degrees of burn analyzed.