In situ damage monitoring during surface treatment of materials

Abstract

Acoustic emission (AE) is a powerful tool to monitor the damage and impact in materials and structures. Process control is also one of the applications of AE measurement. However, it was very difficult to detect and analyze AE signals during material processing because of severe environment. Recently new technique to record AE signals such as laser AE and continuous waveform recording have been developed to apply to material processing. Ceramic thermal barrier coatings (TBCs) by atmospheric plasma spraying (APS) process have been widely used to add good heat resistance to metal base materials. Shot peening is also one of the surface treatment methods to improve the materials properties such as fatigue strength by shooting of balls on the surface of products in order to generate a compressive stress. However, there are a few researches on quantitative evaluation between shot conditions and mechanical properties of products, and the optimal process conditions are determined through a try and error process. AE signals were successfully detected and analyzed in surface treatment such atmospheric plasma spraying, high velocity oxy-fuel coating process and shot peening. Condition monitoring of material processing using AE will be promising to improve the reliability of materials and structures.