光弾塑性法による混合U-V切欠きをもつ平板の応力解析

抄録

In this paper, an experimental stress analysis is reported on flat plates with mixed U-V notches by the photoelasto-plastic method. The model material used is nitro-cellulose. As the preliminary experiment the yield condition of the material and its mechanical and optical properties in the plastic as well as in the elastic region were investigated. From the experimental result of the tension-torsion test using thin-walled pipes cut from the same material, it was found that the yield condition agreed with the Mises' criterion. And the bi-axial tension-tension and tension-compression tests revealed the fact that the stress sensitivity in the plastic region was governed by the equivalent stress.
The tensile loads were applied to the specimens with mixed U-V notches in six steps. The first step was the load which produced a primary yielding at the notch root, and the last step the load causing the penetration of plastic regions through the minimum cross section. For the stress analysis in the plastic range, the Mises' yield criterion and the Prandtl-Reuß incremental strain law were adopted. The fringe order increments dN obtained photoelasto-plastically and the principal strain increments dε₃ determined from the electrical analogy method allow the separation of principal stress increments (dσ₁ and dσ₂). From these values the principal strain increments dε₁ and dε₂ may be calculated. The principal stress σ₂ and the principal strain ε₂ in the minimum cross section were much smaller than the other values σ₁ and ε₁. It has been found as the result of this experiment that the plastic regions generated on both sides of the notches are united to a fairly large extent, including several maximum fringe order points on the longitudinal central axis.