Finite Element Analysis and Life Estimation of a Permanent Cylindrical Mold with ANSYS and Coffin-Manson Approach

Abstract

Thermal fatigue is the most severe problem encountered by a permanent mold, leading to heat checking and cracking which affects the dimensional stability of the mold. Developing a methodology to determine the optimal diameter to thickness ratio to ensure the dimensional stability of a permanent cylindrical mold exposed to cyclic thermal loading is the focus of this work. In this research, thermal stress analysis was performed for multilayered cylindrical molds made up of 2 ¼ % Cr 1% Mo steel and 99% pure copper and cylindrical molds made up of 2 ¼ % Cr 1% Mo steel. Heating and cooling cycles of 10 and 25 seconds were applied to the inside surface, while the outside surface was water cooled. A 2-D (Plane strain) coupled-field analysis was performed using a thermal-elastic-plastic model accounting for the elastic, as wel-l as, the plastic deformation with ANSYS. The Coffin-Manson equation was then used to calculate fatigue life utilizing the strain amplitude was obtained from the finite element analysis. The results of the finite element analysis and the calculated fatigue life were validated against a widely accepted mathematical model’s result and empirical industrial data. The method estimated the actual fatigue life observed in industry conservatively (within 5%).