Experiment and finite element simulation on thermo-mechanically coupled deformation behavior of shape memory polyurethane

Abstract

Monotonic tensile tests of shape memory polyurethane (SMPU) at different strain rates were carried out at room temperature, and the surface temperature of samples was monitored synchronously with the infrared thermometer to investigate the thermo-mechanical coupling effect during stretching. The results show that the post-yield softening is observed due to the disentanglement of molecular chains, after the stress approaches the yield peak, and a localized temperature rise is induced by the friction between molecular chains; with the progressive increasing of load, the strain hardening occurs due to the preferred orientation of molecular chains in the direction of stretching, which induces the stress and temperature rise increase. In the meantime, it is found that both the yield peak and localized temperature rise are increased significantly with the increase of strain rates; however, the competition exists between the strain softening induced by the dissipation heat generation and the strain hardening, making the sensitivity of localized plastic flow on the strain rate decreased. Based on the finite element software ABAQUS, the finite element model of a plate specimen was established to study the thermo-mechanically coupled behavior on the tensile deformation of SMPU. By comparing the contours of plastic strain field with that of temperature field at different moments, it is found that the forming of the localized plastic flow and temperature rise start from the initial defect and gradually move towards the middle and the expand to the entire sample, simultaneously. Furthermore, the simulated average temperature rise curves at different loading rates are in good agreement with the experimental ones.

Keywords

• shape memory polyurethane
• thermo-mechanical coupling
• plastic flow localization
• temperature rise
• rate dependence