抄録
In this study, we used neutron diffraction to analyze in a non-destructive method the distribution of internal residual stress in a free-cutting steel bar processed by cold drawing and straightening. Since a change in lattice-plane spacing occurs in a strain-free standard sample used as a reference due to the cold-drawing and straightening processes, it was necessary for the sake of improving measurement accuracy to prepare strain-free standard samples for each individual process. As a result, the residual stresses were successfully measured with excellent stress balance. The residual stresses generated by the cold-drawing process were reduced by subsequent straightening, and the distribution of residual stresses by finite element method (FEM) simulation was consistent with the measured values by neutron diffraction. As a result of the FEM analysis, it is assumed that the rod was subjected to strong tensile strains in the axial direction during the drawing process, and the residual stresses were generated when the rod was unloaded. Those residual stresses were presumably reduced by the redistribution of residual stresses in the subsequent straightening process.
Fig. 12 Distribution of residual stresses after drawing by neutron diffraction (all peaks) and by FEM.
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