Strain measurement under loading in laser weld on austenitic stainless steel using high-energy synchrotron radiation

The railway carbody structure for commuter and suburban services in Japan is often made of austenitic stainless steel, which is used in the form of the thin metal sheets by cold rolling. It is difficult to observe the strain distribution around the weld zone, which is the critical area of the body structure strength. The objective of this study is to get the strain distribution in stainless steel around the weld zone. To observe the distribution, the strain scanning method by using high-energy synchrotron radiation was applied to the strain measurement of austenitic stainless steel. The transmission method was applied in order to observe internal weld zone. Using this method, we could measure the distribution from surface to inside of the weld zone. The specimen of lapped joint prepared by welding 2mm thick plates by laser weld method was used for measurement. This measurement provides the strain distribution of both residual strain and strain under loading. The result by this measurement shows strain distribution in the weld zone successfully. In addition, the different tendency between the distribution of residual strain and that of strain under loading made be clear. The full width of half maximums, FWHM, of measurement shows a difference between the tendency of measured value of weld zone and that of base material. (author)