The Estimation of Taylor-Quinney Coefficients Using Small Ring Specimens

Abstract

BackgroundThe use of the Taylor-Quinney coefficient for introducing a thermal dissipation term into material models relies on understanding its dependencies. These are usually determined through extensive experimentation, wherein temperature variations are monitored in a test piece during mechanical loading.ObjectiveThis study aims to reduce the cost and time necessary to determining the dependencies of the Taylor-Quinney coefficient by proposing a novel small specimen inverse testing method and demonstrating its use on aluminium alloy 7175.MethodsThe method proposed is based on mechanical testing of a novel small ring specimen in parallel with FEA simulations. In the experiments, small rings of 7175-T7351 aluminium alloy, 20 mm in outer diameter, were loaded between two pins for different pin displacement rates (namely 1, 1.5 and 2 mm/s) at room temperature and the local specimen temperature field was monitored using an infra-red thermal camera. Fully coupled thermal-mechanical simulations of the tests were performed using a range of Taylor-Quinney coefficients, and the resulting temperature evolutions compared to the experimental results in order to determine appropriate coefficient values for the material.ResultsThe method presented shows good repeatability and allows for clear observation of thermal dissipation. Taylor-Quinney values ranging 0.51-0.59 are reported for the 7175 alloy, in line with values reported in the literature for similar alloys. Density, specific heat capacity and thermal conductivity, fundamental thermal material properties necessary for the simulations, are also reported for the alloy.ConclusionsThe method detailed shows promise for determining Taylor-Quinney coefficients in a wide range of experimental conditions and is proposed as a cheap and fast alternative to full-scale specimen testing of Taylor-Quinney coefficients. Taylor-Quinney values obtained for 7175 aluminium are shown to be much lower than the value of 0.9 often proposed for materials.