서강대학교

초록/요약

The work tools in hot forging processes are subjected to the cyclic thermo-mechanical stresses due to repetitive contact with the workpiece and the lubricant. To evaluate the thermo-mechanical stress fields quickly and precisely, an FE model is proposed to solve the repetitive heat transfer problem quickly. The proposed FE model only solves heat transfer problems while skipping the deformation analysis and increases the time increment to save the computation time. A simple upsetting process is analysed to validate the FE model proposed. The developed FE model is also verified by comparing the temperature of the specific spot of the hot forging die from the experiment and the computation. The computation time to evaluate the temperature fields during the forging process is reduced by 13.8 times when the proposed FE model is utilised. The Lemaitre damage model is modified and utilised to predict the lifetime of the work tool using the thermo-mechanical stress fields. The model constants of the modified Lemaitre damage model are determined using tensile test results in different temperatures. The distribution and evolution of the damage in the work tool is analysed and the lifetime of the work tool is predicted.