Introducing the ECNI-II

Author:  Shuji Hayashida / Yuji Kobayashi | SINTOKOGIO, LTD Japan
Source:  The Shot Peener magazine, Vol 35, Issue 4, Fall 2021
Doc ID:  2021034
Year of Publication:  2021
Abstract:  
1. INTRODUCTION Special processes such as heat treatment, painting, and welding are difficult to visually inspect. Shot peening (SP) is one of these special processes. SP is a dry method of surface modification. SP improves the fatigue strength by inducing compressive residual stress on the surface of the metal to be processed. Therefore, it is important to measure the compressive residual stress. Until now, the quality control of the products in the SP processing line has not been performed, but only the process control of the processing machine has been performed. On the other hand, residual stress measurement after the process has been done off-line, if necessary. Generally, the X-ray diffraction method is used for stress measurement of metallic materials; the penetration depth of X-rays is a few micrometers from the top surface. If the stress in the depth direction is needed, it is necessary to measure it step by step by electropolishing. This results in the destruction of the product. Thus, it is a spot check. Therefore, there is a need for a non-destructive method to inspect the compressive residual stress in the depth direction applied by SP.