The Bending Behavior of NiTi

The bending behavior of superelastic and shape memory Nitinol wire with circular and rectangular cross sections was studied in three-point, four-point and pure bending. Four-point and pure bending results are in good agreement with each other, whereas those from three-point bending show marked differences. The stress-strain curves of the four-point and pure bending were also compared with uniaxial tensile results. As expected, the plateau stresses in bending were consistently higher than those in tension. The tensile data were then analyzed with the modified plasticity theory for pseudoelastic beams and further compared with the bending results. It was found that the linear elastic range and upper plateau stresses are in close agreement with the bending data. Differences were found, however, for the lower plateau and the springback strain, which may result from the different modes of deformation.