Laser-induced Surface Burn: A Feasible Approach for Controlled Production of Thermal Damage and its Monitoring Based on Acoustic Emission
Z-S. Yang, Y-F. Huang, M-Z. Wang, W. Yan, B-P. Gu and Z-H. Yu
Due to the fact that energy partition ratio in grinding is generally higher than other machining processes, surface burn is one of the most common defects in grinding and hard turning of steels. Unfortunately, as grinding is considered to be highly complex, non-stationary and dependent on a large number of input variables, the monitoring of surface burn in grinding process is thus necessary yet difficult. In this work a surface burn production method using high energy density pulsed laser was introduced. Controlled surface burn on various metals was obtained by adjusting laser pulse duration and pulse frequency. Acoustic emission was used for in-process surface burn monitoring. Factors such as laser pulse duration, pulse frequency and sensor mounting location which influence acoustic emission features were also studied. Frequency spectra with and without surface burn were compared. The differences were distinct. It was also found that root mean square (RMS) and mean energy of acoustic emission could successfully reflect the occurrence of surface burn. Findings in this work could provide knowledge for further surface burn monitoring in grinding.
Keywords: Nd:YAG laser, stainless steel, AISI 304, carbon steel, ASTM A36, AISI 1045, surface burn, thermal damage, acoustic emission, monitoring