14th International Conference on Shot Peening

Application of on-sight positron annihilation lifetime spectroscopy system as non-destructively shot peening evaluation technique

N. Uesugi, M. Yamawaki, K. Hattori and Y. Watanabe

Toyo Seiko Co., Ltd., Japan

National Institute of Advanced Industrial Science and Technology, Japan

Corresponding Author: y_watanabe@toyoseiko.co.jp

Abstract

An evaluation of shot peening is usually evaluated by X-ray diffraction, but sometime polishing or cutting a sample should be required to measure deep region from surface. In order to increase the reliability of the treatment, a completely non-destructive method is strongly required. Positron annihilation lifetime spectroscopy (PALS) is a non-destructively technique to study open-volume lattice defects such as vacancies or dislocations. Shot peening induce plastic deformation in a surface, so some lattice defects are introduced in that region. A positron emitted from 22Na source, which is generally used for PALS, penetrate up to about 100 m in steels, so it is possible to evaluate deeper region non-destructively compared with X-ray diffraction method. We have demonstrated that PALS is effective as shot peening evaluation technique in some works.

Incidentally, it is necessary to put parts into a dark box for non-destructively PALS measurement. So an apparatus size must be bigger as target parts is bigger. Recently we developed a new apparatus capable of on-site PALS measurement. The apparatus have “dark-box-less” structure, so no matter how target parts is bigger, the apparatus size and weight can be small. In this study, we validated that the new apparatus have the same potential for shot peening evaluation as the conventional system (with dark box system). Moreover, to improve the usefulness of PALS we attempted to reduce a measurement time using new analysis method.

It is confirmed almost same value are obtained using the new system as well the conventional system by adjusting fitting parameters. And it is suggested the new analysis method have a potential to greatly reduce measurement time for shot peening