集合組織を有する鋼の残留応力測定

抄録

Non-linear sin²ψ relations are sometimes observed when the X-ray stress analysis was performed on the materials having preferred orientations. Therefore, the stress determination by the Sin²ψ method is impossible for such case. There are three main factors influencing the oscillation of lattice strain with Sin²ψ as follows: 1) Elastic anisotropy, 2) Plastic anisotropy and 3) Instrumental effect caused by the X-ray optics.
This paper deals with the possibility of residual stress measurement for cold-rolled steels having a typical preferred orientation.
The results obtained are summarized as follows:
1) The distribution of X-ray elastic constants with respect to Sin²ψ for the (211) diffraction was precisely calculated based on the modified Dölle model and it agreed with the experimental result.
2) The experimental values of X-ray elastic constants also agreed with the analytical values for the isotropic steel by the Reuss model at Sin²ψ=0 and 0.75. Since the X-ray elastic strains at such positions are linear with Sin²ψ, we can determine the elastic stresses in textured steels by using the isotropic X-ray elastic constant by the Reuss model.
3) A remarkable oscillation in the Sin²ψ diagram was observed by the fixed ψ₀ method. This oscillation originated from the X-ray optics was analyzed by the numerical simulation. The result indicates that both the X-ray strains at Sin²ψ=0 and 0.75 on the (211) diffraction agree with those by the fixed ψ method. Thus, we proved that the residual stresses in textured steels can be measured by using both X-ray strains at such values of Sin²ψ.