Stress and strain states in a pseudoelastic wire subjected to bending rotation

Bending rotation is a load case where an originally straight wire is bent into a curved shape and subsequently forced to rotate around its longitudinal axis. Continuous bending rotation results in tension–compression cycles and is used to assess the fatigue resistance of pseudoelastic shape memory wires for medical applications. It is important to discuss fatigue on the basis of the underlying cyclic stress and strain states. To our knowledge, all previous studies on pseudoelastic bending rotation estimated the strain amplitudes by a simplified mechanical model (i.e. pure bending). In this study, a bilinear material model for pseudoelasticity is used to analytically derive a more accurate mechanical description of the stress and strain distributions during pseudoelastic bending rotation. We use numerical calculations to show that the stress and strain states, and other characteristic parameters, differ significantly between pure bending and bending rotation of pseudoelastic wires.