THERMO-MECHANICAL ANALYSIS OF A COMPLEX GRAY IRON CASTING

摘要

Cracking due to excessive thermal stresses/strains can be a severe problem for complex iron casting parts such as engine cylinder heads. The root causes of this problem are not intuitively revealed because of the complexity of the geometry of the parts and the casting processes. Performing thermo-mechanical analysis of an iron casting over the entire casting process including mold filling, in mold solidification and cooling, shake out and subsequent air cooling, removal of the gating system and risers and stress relief/heat treatment can provide complete residual stress and deformation history in the casting. This information is valuable for pinning down the root causes of cracking and provides redesign directions to both foundry tooling engineers and product design engineers. An elastic-plastic thermo-mechanical model implemented using commercial FEA packages is presented. Uni-axial tensile tests from room temperature to 1100℃ of gray iron samples are conducted to provide material behavior and fracture criterion. An application of the model is then presented.