Abstract
Within this study, a new method for the determination of the Taylor-Quinney coefficient is presented. The coefficient was identified by measuring the force-displacement-behavior as well as the temperature change resulting from an adiabatic compression test. In order to deduce the global temperature increasing of the specimen from the local measured temperature a suitable specimen geometry was designed with the use of numerical simulation. The resulting specimen allows a friction-free compression and therefore precludes a temperature increase through friction. Finally, the Taylor-Quinney coefficient of C35 steel (1.0501) was experimentally determined in the initial state as well as after a heat treatment.
Highlights
During forming processes, a large amount of the performed plastic work Wplast is converted directly into thermal energy Q, due to material dependent internal friction [1]
In order to describe the material behavior within the numerical simulation, the yield curves of C35 were determined using the conventional compression test
The numerical simulation of the upsetting process shows that the deviation between calculated and predefined Taylor-Quinney coefficient can be influenced by adapting the specimen geometry
Summary
During forming processes, a large amount of the performed plastic work Wplast is converted directly into thermal energy Q, due to material dependent internal friction [1]. This leads to inaccuracies during the determination of the Taylor-Quinney coefficient β due to the simplified assumptions. The determination of the Taylor-Quinney coefficient β with the use of compression tests is falsified because friction occurs between the front side of the specimen and the tools. − simple and solid experimental setup − realization of high plastic strain − achieving high strain rates in order to guarantee adiabatic conditions − almost frictionless deformation in order to neglect heating through friction at front side − simple temperature detection with the help of thermocouples. This optimizing step is necessary due to the formation of a temperature field caused by inhomogeneous distribution of forming degree during upsetting. The grain size increases from 25 μm at the initial state to 75 μm due to the heat treatment
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