Evaluation of distortion of castings

Displacement results are usually used as the criterion for distortion of castings during casting and heat treatment processes. However, the displacement results consist of both contraction and distortion. Contraction is a kind of uniform volume change, which can be solved by enlarging the castings by a contraction coefficient. However, the actual distortion has to be deleted by giving inverse distortion or by mechanical correction method. In this paper, algorithms are presented to evaluate the distortion of castings. One method is to subtract the uniform contraction from the displacement results. The other is to calculate the deflection angle between the normal direction of the discretised surface triangle of the original casting shape in stereolithography format and that of the simulated casting shape. The third one is the application of actual machining allowance in the evaluation of distortion. These methods are validated by three case studies, including a heavy hydroturbine blade casting.