Thermal Fatigue Analysis of Hot Forging Closed Dies

Abstract The aim of this work is to develop a numerical subroutine for the commercial finite element method software QFORM VX 8.1.4 capable of predicting, simultaneously, regions of closed dies which are prone to thermal fatigue as well as the number of cycles required for thermal fatigue cracking. The numerical subroutine was based on Manson (thermal fatigue) and Coffin-Manson (number of cycles) equations. Hot forging of AISI 1045 grinding balls using AISI H13 closed dies was performed and the numerical and experimental results were compared. The findings indicated that after forging 66 grinding balls, the numerical model achieved steady state for the temperature inside the die. After forging 600 grinding balls, both the experimental and numerical results showed that the regions of the dies subjected to the highest thermal gradient were prone to thermal fatigue. In addition to that, the numerically predicted values for the onset of thermal cracking were consistent with the experimental results: 517 and 600 cycles, respectively.摘要 本研究旨在为商用有限元法软件QFORM VX 8.1.4开发一款数值子程序，该子程序可同时预测闭式模具易发生热疲劳的区域，以及热疲劳裂纹萌生所需的循环次数。该数值子程序基于Manson（热疲劳）方程与Coffin-Manson（循环次数）方程构建。采用AISI H13闭式模具开展AISI 1045钢磨球热锻造实验，并对比了数值模拟与实验结果。研究结果表明，锻造66个磨球后，模具内部温度场达到稳态。锻造600个磨球后，实验与数值模拟结果均显示，承受最高热梯度的模具区域易发生热疲劳。此外，数值模拟预测的热裂纹萌生循环次数与实验结果吻合良好，分别为517次与600次。