Hybrid method for determining the fraction of plastic work converted to heat

Abstract

The fraction of plastic work converted to heat is typically measured either by nearly isothermal experiments, in which the thermal energy is measured during a deformation experiment with a calorimeter, or by adiabatic experiments, in which the thermal energy is determined from the temperature rise, measured either during the test or immediately after the test by dropping the sample into a calorimeter. In the present work, the temperature is measured with a single fine-wire thermocouple. The restriction to adiabatic loadings is relaxed by using a hybrid method that combines the measurements with finite difference simulations to calculate the heat losses that occur during the test. These heat losses are then accounted for in the final energy balance to determine the fraction of plastic work converted to heat. The method is applied to annealed 302 stainless steel. The results show that the fraction of plastic work converted to heat is a decreasing function ranging from 0.7 to 0.4 over a tensile strain range of 0 to 0.15. An analysis of the restrictions to this method and of the potential errors is given.