The dependence of the Taylor-Quinney coefficient on the dynamic loading mode

The efficiency of the thermomechanical conversion, expressed as the Taylor-Quinney co-efficient (TQC) is seldom reported in the literature and generally assumed to be equal to 0.9. Moreover, an eventual dependence of this coefficient on the dynamic loading mode has not been investigated so far. This work presents a systematic characterization of the TQC for seven different metals and alloys loaded in dynamic tension, compression and dominant shear. The results show that the TQC varies greatly with the investigated material, instead of its assumed constant value of 0.9. Likewise, until final collapse of the specimen, the overall temperature rise remains quite modest. Moreover, we clearly observe that for commercially pure Titanium, which exhibits an asymmetric mechanical response in tension and compression, the measured TQC values are mode dependent too. Microstructural characterization reveals profuse twinning in compression and shear, as opposed to tension. Twinning is related to heat generation in accord with previous studies. In addition to reporting a wide database of TQC values, this study reveals a new correlation between the thermomechanical characteristics of a material and its deformation micromechanisms, that should find its way into constitutive models. (C) 2017 Elsevier Ltd. All rights reserved.