An error when the stress is measured from average diameters of a debye ring in X-ray stress measurement

The local surface residual stress values of the ceramics near the Si3N4/SUS304 brazing joint interface have been measured by a X-ray film method. The diffraction pattern become spotty due to the use of an X-ray beam as thin as 100 μ in diameter (full width at half maximum). Such at diffraction ring was not able to be measured by a comparator. Therefore authors measured stresses by measuring average diameters of a Debye ring of high diffraction angle and applying Sin2ψ method. For these reasons, an image processor was used to measure a diffraction ring diameter. The characteristic X-rays of Vanadium-Kα and the lattice plane (212) of Si3N4 were selected to obtain a high diffraction angle. The resultant diffraction angle was 170.83deg (2θ0) under unloading condition. This paper discribes a numerical evaluation about an error when the stress is calculated from average diameters of a diffraction ring. The stress is given by a relationship between strain (εφψ, ε-barη) and Sin2ψ. Authors evaluate about εφψ and ε-barη. As a result, an error of measured stress is less than ±7 Mpa in case of a residual stress is |500| Mpa. (author)