Original Paper(Vol.61 No.7 pp.612-619)

Consideration of Microstructure Evolution and Residual Stress Measurement near Severe Worked Surface Using High Energy X-Ray

Tadafumi HASHIMOTO, Takahisa SHOBU and Masahito MOCHIZUKI

Abstract:It is necessary to establish a measurement method that can evaluate accurate stress on the surface. However, the microstructure evolution takes place near the surface due to severe plastic deformation, since structural members have been superpositioned a lot of working processes to complete. As well known, a plane stress canft be assumed on the severe worked surface. Therefore we have been proposed the measurement method that can be measured the in-depth distribution of residual stress components by using high energy X-ray from a synchrotron radiation source. the constant penetration depth method and tri-axial stress analysis. Measurements were performed by diffraction planes for the orientation parameter =0.25 of which elastic constants are nearly equal to the mechanical one. The stress components obtained must be converted to the stress components in real space by using optimization technique, since it corresponds to the weighted average stress components associated with the attenuation of X-ray in materials. The predicted stress components distribution agrees very well with the corrected one which was measured by the conventional removal method. To verify the availability of the proposed method, thermal aging variation of residual stress components on the severe worked surface under elevated temperature was investigated using specimen superpositioned working processes (i.e., welding, machining, peening). It is clarified that the residual stress components increase with thermal aging, using the diffraction planes in hard elastic constants to the bulk. This result suggests that the thermal stability of residual stress has the dependence of the diffraction plane.

Key Words:Ni based alloy, Severe worked surface, High energy X-ray, Tri-axial stress analysis, Working process, Microstructure evolution