The present paper addresses the computer modelling of pipe formation in castings. As a preliminary, a brief review of the current state-of-the-art in pipe shrinkage computation is presented: most of existing methods are based on thermal considerations only. In the current paper, it is demonstrated that this typical evolution of the free surface, originated by shrinkage at solidification front and compensating feeding liquid flow, can be effectively approached by a thermomechanical analysis in the frame of the finite element method (FEM) and the arbitrary Lagrangian-Eulerian (ALE) formulation. In a first part, the constitutive equations that have to be considered in thermomechanical computations are presented. This point is central because the cast alloy is simultaneously present in liquid, mushy and solid state. Then the main lines of the mechanical finite element resolution are given, insisting on the fact that it permits the concurrent computation of stresses and strains in solidified areas and of liquid flow in still liquid or mushy zones. A detailed presentation of the Eulerian-Lagrangian formulation follows, explaining the connection between the Lagrangian and the quasi Eulerian zones, and the treatment of free surfaces. Finally, an example of application to an industrial casting is given.

In this paper, simulation of the casting and heat treatment processes of front spindle of a rigid dump truck are presented. The objectives are to present how the different operations can be simulated in order to predict the local phases in the different areas of the part. To reach these objectives, two software packages are used in sequenced. The first one, Thercast, is used to simulate the casting operation. The second one, Forge, is applied to the water-quenching simulation. The general formulations used are shortly presented in this paper. The aim of casting simulation is to compute the metal behavior from the liquid state at the pouring stage to the solid state during cooling into the mold. Filling and cooling phases simulations, taking into account the air gap, ensure that no internal defects like shrinkage, porosity, micro porosity or hot tearing are taking place into the part. Forge software allows the water quenching stage simulation. A model is used to deduct the IT diagram (Isothermal Transformation diagram) from the material composition. The initial grain size influences the transformation kinetics. Another main phenomenon is the efficiency of the cooling bath. The results of the simulation (phase distribution, distortion, residual stresses) strongly depend on these input conditions. Thus, the effect of input data variations on final results must be studied. The modeling approach is validated by comparisons with micrographic observations. Another solution to determine the reliability of the models is to observe the local properties in the quenched part. The prediction of the local micro hardness can be used to evaluate the accuracy of the quenching models.

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