Determination of the heat transfer coefficient at the workpiece—die interface for the forging process

Abstract

This paper describes an investigation of the determination of the heat transfer coe cient at the workpiece±die interface for the forging process. A surface thermocouple has been constructed to measure the temperature at the die surface, where a high pressure occurs, for the simple upsetting forging process. The process was also simulated by a commercial ®nite element package. The measured and predicted temperatures were then used in an inverse algorithm with an iterative approach to determine the interface heat transfer coe cient (IHTC). The results show that the predicted temperatures modelled by a constant IHTC at the rest-on-die stage were in good agreement with the experimental measurement. However, for the forging stage, the IHTC values vary signi®cantly during the process. This has important consequences in the implementation of simulation software.

Influence of the inaccuracy of thermal contact conductance coefficient on the weighted-mean temperature calculated for a forged blank

“…A close look at the references (Kopp and Phillip, 1992;Rosochowska et al, 2004;Nshama et al, 1994;Chang and Bramley, 2002;Burte et al, 1990;Jain, 1990;Semiatin et al, 1987;Rosochowska et al, 2003;Goizet et al, 1998;Caliskanoglu et al, 2002) shows that most values of the coefficient˛were determined for low and moderate temperatures. The error in determining of this coefficient is not given in most of scientific papers.…”

“…The determination of the˛coefficient by mixed methods (Kopp and Phillip, 1992;Chang and Bramley, 2002;Caliskanoglu et al, 2002) introduces the inaccuracy in the simulation program output. The error of the simulation cannot be evaluated in this case, as available simulation programs require the input of many other parameters whose accurate values are also unknown.…”

Exact and approximate methods for determining the thermal parameters of the forging process

“…The rough value of the convection heat transfer coefficient h was calculated by the empirical formula described in the literature [1]:…”

“…According to British [1], German [2] and other researchers, experimental data of test piece cooling are obtained and put into a black-box type "industrial package" with programs using the finite elements method for calculation purposes. Results of this calculation are satisfactory, but these studies cannot be used as a standard to determine thermal parameters since the information presented in the articles is incomplete.…”

The Influence of the Model Selected Parameter Measurement Error on the Accuracy of Heat Transfer Coefficient Determination Method for Contact between Rolls and the Cast Strand

“…Heat transfer occurs by radiation within a very thin gap, and by conduction between two surfaces that are in contact. The modelling of the temperature field, heat flux or heat transfer coefficient and other phenomena as regards the process of heat transfer between two solid surfaces has been analysed by several authors, using both commercial software and original formulations [4][5][6][7][8][9]. The boundary conditions of heat transfer need to be determined in order to obtain the solution to the heat conduction equation needed to obtain the temperature field.…”