Deformation energy of NiTi shape memory wires

作者：Akhlaghi M; Mahmudi R^*; Nili Ahmadabadi M

来源：Materials & Design, 2011, 32(4): 1923-1930.

DOI：10.1016/j.matdes.2010.12.006

• Wrought
• Mechanical
• Plastic behaviour

Deformation energy of NiTi wires with B2 and R phases was studied by the multiple tensile testing (MIT) method. In traditional materials, the total energy required to tear specimens is assumed to be the sum of elastic, uniform plastic, and post-uniform or tearing energy components. For the shape memory alloys, however, this classification is not valid due to their unusual superelastic/shape memory characteristics. Using a modified MU method, different energy components were calculated by plotting different combination of deformation energies divided by the specimen cross-sectional area against the gage length of the specimens. The slope of the obtained straight line demonstrates the summation of the elastic, superelastic/shape memory, second elastic, and plastic energy per unit volume and its intercept gives the value of tearing energy. It was found that the uniform plastic energy per unit volume for the R-phase wires was considerably higher than that for the 82-phase wires. This caused a marked enhancement in the total deformation energy of the R-phase wire, as compared to the B2-phase wire. The effect of strain rate on the tensile behaviour and deformation energies of these materials was also investigated. Except the plateau stress of the tensile curve which was raised for both wires, the B2-phase wires were almost strain-rate-independent, whereas the R-phase wires were significantly influenced by the variation in strain rate.

• 出版日期2011-4