Strain measurements using high energy white X-rays at SPring-8

Shobu, Takahisa  ; Kaneko, Hiroshi; Mizuki, Junichiro; Konishi, Hiroyuki; Shibano, Junichi*; Hirata, Tomoyuki*; Suzuki, Kenji*

The third generation synchrotron X-ray source such as SPring-8 provides us intense beams of high energy X-rays. The techniques of non-destructive internal residual stress measurement for industrial applications are well established by angle dispersive diffractometry with high energy synchrotron radiation and provide valuable information. The energy dispersive diffraction techniques using white radiation is the advantage of a stress measurement compared with the angular dispersive one. For example, the multitudes of reflections recorded in one spectrum offers additional information that can be used for stress gradient evaluation. The purpose of present study is to apply high energy white X-rays to the measurement of the residual strain in the bulk specimen. The experiment was carried out on the beamline BL14B1 at SPring-8. A diffraction pattern was collected by a Ge Solid State Detector (SSD) mounted on the arm of a 2-axes diffractometer behind two sets of secondary collimating slits. The beam size of white X-rays was 0.05 0.3 mm. The specimens were JIS-S45C carbon steel and JIS-SUS304 austenitic stainless steel with a thickness of 5mm. The bending stress was applied with the four-point bending and the strain at the surface of the specimen was measured by a strain gauge as shown in the figure. X-rays diffraction measurement was carried out simultaneously. The figure shows each diffraction profile of SUS304 taken with white X-rays. The strain was calculated by the ratio of the energy shift to the peak energy. Though many peaks appeared in every measured positions Y, each diffraction pattern depended on the number and the orientation of crystal grains in irradiated volume by X-rays. The calculated strain by using a single peak is depending on peak quality. The accurate internal stress can be obtained with white X-rays by selecting the peak at high energy, high peak counts and close to Gaussian peak profile.