DETERMINATION OF THE DIE PROFILE FOR THE INVESTMENT-CASTING OF AEROFOIL-SHAPED TURBINE-BLADES USING THE FINITE-ELEMENT METHOD

Turbine blades and vanes used in aircraft engines are expected to conf orm to close dimensional tolerances, but super-alloy blade material ca nnot be machined easily. Although investment casting is an ideal route for producing such net-shape components, it calls for an accurate det ermination of the casting-die profile. This investigation outlines a s imple finite-element methodology (FEM) for obtaining the die profile, which takes into account the various shrinkages involved in the castin g process. The shrinkages are lumped into a single stress-free strain tensor and the FEM-based numerical computation is performed, treating the shrinkage strain as an initial strain. A fictitious sponge-like la yer of elements is incorporated at the boundary of the aerofoil cross- section in order to impose the necessary kinematic constraints to rest rain rigid-body modes. The applicability of this method is validated u sing experimental data.