Fluid Structure Interaction (FSI) and Thermal Stress Evolution (TSE)
A Coupled Finite-Element/Finite-Difference Model
The thermal stress evolution model in FLOW-3D v10 extends the range of casting processes that can be modeled. The FSI/TSE model describes fully-coupled interactions between fluid and solid using a finite element approach to model stresses and deformations in solid and solidified components in response to pressure forces from the surrounding fluid, thermal gradients, and specified constraints.
Thermal stresses develop during the solidification process which are caused by non-uniform cooling. These stresses are influenced by shrinkage at mold walls and irregularities in the casting's shape.
This is a V6 engine block composed of Aluminum A380 alloy that was cast within a steel die. The pour temperature of the aluminum was 527°C and the initial die temperature was 125°C. The part was cooled within the die for 60s, after which the die was opened and the part continued to cool for 9 minutes in ambient conditions (125°C), totaling 10 minutes of simulation time. The von Mises stress shown here is a measure of the magnitude of shear stresses within the part, thus showing regions where tearing is most like to occur.
Stresses can be simultaneously computed in the mold and in the solidifying metal. Meshing is done automatically by choosing to generate a mesh of the fluid region or the solid domain depending on the analysis desired. Within a few seconds the user has a finite element mesh.
Simulating Thermal Stress
This is an aluminum cover, also composed of Aluminum A380 alloy cast within a steel die. The pour temperature was 654°C and the initial die temperature was 240°C. The part was cooled within the die for 6s at which point the part was completely solidified (except for the runner system). The die was then opened and the part was allowed to cool a further 10s in ambient conditions (25°C). The runner system was then removed, after which a further 10s of cooling in ambient conditions occurred. The normal displacement shown here indicates the motion of the surface of the part, magnified 30 times to highlight the greatest regions of deformation.