In-process grinding burn detection by use of different Barkhausen noise measurement techniques

Magnetic Barkhausen noise (BN) measurement is a non-destructive method for the fast and data-based inspection of machined surfaces regarding grinding burn. While post-process Barkhausen noise inspection is already used in industry, the application directly during machining is a current research field. In perspective, these in-process measurements provide the prerequisites for a future process control. Besides the general usability of BN for damage detection during grinding, existing studies show a superposition of magnetic BN and mechanical effects generated during grinding what requires further investigations. Furthermore, existing studies use measurement devices from different manufacturers but up to now no direct comparison during identical processes was performed. The present work compares the measurement signals of Rollscan and 3MA-II device during grinding of two different workpieces: a cylindrical workpiece with dw=67.7 mm from AISI 4820 (DIN 18CrNiMo7-6) and a smaller workpiece with lower mass from AISI 52100 (DIN 100Cr6). Besides similarities and the general suitability for the detection of thermo-mechanical surface damages, both measurement techniques exhibit differences in the sensitivity to mechanical induced BN effects. The mechanical induced BN was investigated by different trials on a workpiece with thermo-mechanical damage over half of the circumference. In general, the BN excitated by grinding wheel contact correlates with surface state and excitation strength in the same way as magnetic BN. Even if the Rollscan technology seems to be more sensitive to mechanical excitation, both measurement technologies allow a distinction of damaged and undamaged surface states even without additional magnetization by an external field.