MODELING OF THERMAL-STRESSES AND THERMAL-CRACKING DURING HEATING OF LARGE INGOTS

The development of temperature gradients and thermal stresses during t he heating of large ingots has been investigated with special referenc e to the selection of heating schedules for brittle intermetallic mate rials such as titanium aluminides. A 1-D analytical (series) solution for radial temperature transients was used in conjunction with an elas ticity analysis to determine the maximum thermal stresses that would b e generated during ingot heating. The temperature gradients and stress es were seen to be strongly dependent on Fourier and Biot Numbers. In addition, finite element method simulations incorporating end effects and variations of thermal and elastic properties with temperature were performed and compared to the analytical results. Comparison of the p redicted thermal stresses and actual ingot heating observations sugges t that cracking is controlled by a maximum normal stress criterion.