Effect of Magnetic Stirring to Anelasticity of Steel Compression Coil Spring (Role of magnetic domain walls for weakly pinning dislocations)

Abstract

Anelasticity is an important phenomenon for spring technology, since it affects the size and restoring force of a spring during its operation. Although this property has been known more than a half-century ago, its mechanism has not been clarified yet. In this study we have evaluated the effects of magnetic treatments to the anelasticity of steel compression coil springs during elastic deformation in experiments. We measured the temporal change of recovery lengths of the specimens after unloading with or without magnetic stirring under 180mT, since free length change of the coil spring is the summation of the faint twist modification in the steel wire. Each spring of 20mm long showed about 20μm length of recovery in 2 hours from the point of 90 second after the unloading. It indicates some bowing-out dislocations during the compression were interrupted with certain disturbances. The length of recovery was increased in 10％ for the magnetic stirring specimens. Since alternatively changed external magnetic field expands the length of magnetic domain walls in steel, it suggests the walls might play the role of obstacles, such as weak pinning sites, against the recovery movement of the dislocations in anelasticity.