Patent ID: 7003074

Claim:
A stress measurement method using X-ray diffraction, said method comprising: (a) preparing a c-axis-oriented specimen of a tetragonal polycrystal as a specimen to be measured; (b) defining, as a specimen coordinate system, a coordinate axis P 3 perpendicular to a surface of the specimen and two coordinate axes P 1 and P 2 orthogonal to each other within the specimen surface, and arranging an X-ray optical system including an X-ray source and an X-ray detector such that a coordinate axis L 3 of a laboratory coordinate system based on the X-ray optical system is within a plane including the coordinate axes P 1 and P 3 ; (c) selecting one set of Miller indices (hkl) of the specimen, and arranging the X-ray source and the X-ray detector to be symmetrical about a normal to a crystal plane with said one set of Miller indices (hkl), the normal to the crystal plane being inclined from a normal to the specimen surface at an angle of ψ, so that a diffracted X-ray from the crystal plane with said one set of Miller indices (hkl) is detectable with a diffraction angle θ 0 (diffraction angle in a non-strain state); (d) irradiating the specimen with an X-ray, detecting a diffracted X-ray therefrom with the X-ray detector, adjusting the X-ray optical system to determine a diffraction angle θ at which the diffracted X-ray exhibits a maximum intensity, and determining the diffraction angle θ as a measurement value; (e) determining a strain based on the diffraction angle θ 0 in the non-strain state and the measured diffraction angle θ; (f) repeating steps (c) to (e) in which another set of Miller indices (hkl) is selected in step (c), and determining a strain with respect to said another set of Miller indices (hkl); (g) arranging said coordinate axis L 3 of the laboratory coordinate system within a plane which is derived by rotating the plane including the coordinate axes P 1 and P 3 around the coordinate axis P 3 through an angle of φ=45′; (h) repeating steps (c) to (f); (i) arranging said coordinate axis L 3 of the laboratory coordinate system within a plane which is derived by rotating the plane including the coordinate axes P 1 and P 3 around the coordinate axis P 3 through an angle of φ=90°; (j) repeating steps (c) to (f); and (k) determining a stress σ 11 in a direction of the coordinate axis P 1 , a stress σ 22 in a direction of the coordinate axis P 2 and a shearing stress σ 12 between the coordinate axes P 1 and P 2 based on a strain ε(φ=0°) determined in step (f), a strain ε(φ=45°) determined in step (h), a strain ε(φ=90°) determined in step (j) and sin 2 ψ based on stress calculation formulae determined under conditions of a plane stress state and a symmetry 4/mmm.