Weak Pinning and Unpinning of Dislocations Observed from Residual Elongation in Compression Steel Springs

Abstract

To study anelastic effect in steel, we observed residual elongation of a compression steel coil spring after unloading compression force, which was previously applied to the specimen for various periods. Total residual elongation and saturation time are increased with the compression period. Since pure share stress is applied to the spring wire during compression, major share elastic strain is explained from bow-like expansion of dislocations between strong pinning points. The above phenomena indicate small partial expanded dislocations are weakly pinned at certain sites such as magnetic domain walls and the pinning cites are increased with the compression time.