Numerical Analysis of Thermal Growth of Cast Aluminum Engine Components

As-cast or as-solution treated cast aluminum A319 has copper solutions within its aluminum dendrite. These copper solutions precipitate out to form Al₂Cu through a sequence of phase changes and bring with them volume changes at elevated temperatures. These volume changes, referred to as thermal growth are irreversible. The magnitude of thermal growth at a material point is decided by the temperature history of the material point. When an under aged or non heat treated cast aluminum is exposed to non-uniform temperature such as that during engine operation, thermal growth leads to non-uniform volume change and thus additional self balanced stresses. These stresses remain inside material as residual stresses even when the temperature of the material is uniform again.

In the present paper, numerical analysis method for thermal growth is developed and integrated into engine operation analysis. A user subroutine is written to interface thermal growth theory with commercial finite element code ABAQUS. The impact of thermal growth on durability of an engine cylinder head is illustrated by a real case study.