Limitations of Constitutive Relations for TiNi Shape Memory Alloys

Phase transformation tensor Q in the constitutive equation pmposed by Tanaka has been evaluated by employing experimental data of TiNi alloys in a constrained recovery process. It demonstrates that the absolute value of Q for the consmined recovery process is typically about 0.6 0.7 x103 MPa, which is much smaller than that for the stress induced martensitic transformation (typically 2.5 3.5 x103). Based on the evaluated results for Q. predicted recovery stress temperature relations by the constitutive equation are compared with the experimental data for TiNi rods under different strains. Big discrepancy exists for large strain conditions. Several transformation kinetic expressions are examined for the constitutive relation of the constrained recovery process.