The effecT of mechanIcal InTeracTIons beTween The casTIng and The mold on The condITIons of heaT dIssIpaTIon: a numerIcal model WpłyW oddziałyWań mechanicznych między odleWem a formą odleWniczą na Warunki oddaWania ciepła: model numeryczny

During the solidification, and then cooling, generally a shrinkage gap or mechanical interaction (grip or slip) can occur between the casting and the mold. The character of interaction is decided by the shape of casting. Both these phenomena occur in most real castings. Shrinkage gap, and specifically its width, determines the heat flow between cast and mold, while the mechanical interactions lead to increased stress in the solidified layer [11]. If these stresses exceed the limit value, they can damage the solidified layer and, consequently, cause the emergence of casting defects. In most numerical simulations the mechanical interactions are not considered. In the case of shaped casting solidification modeling, only factors affecting the thermal conductivity of the shrinkage gap are taken into account in the heat calculation [2, 12, 13, 14]. The casting structure properties are determined by the push of solute from the growing solid phase, together with the thermal processes and the liquid phase movement. The increasing solid phase forms a skeleton that has the ability to transfer the mechanical loads. Depending on the type of structure, the ability to transfer mechanical loads emerges for different values of the local solid phase fraction. Diverse temperature gradients together with the resistance put up by the mold are the cause of stress in the solidifying castings, mechanical interaction and shrinkage gap occurrence [1, 4]. The cooling casting shrinkage is the sum of shrinkage caused by temperature and phase change. The stresses are transferred by the solid phase – in the casting domains completely solidified or by the inter-granular layers in the not fully solidified casting domains. The deformations caused by the mechanical reactions of solidifying casting and mold are small and therefore the friction forces can be neglected in mathematical description of the problem. The shrinkage gap has the greatest impact on the heat exchange between the casting and the mold. Its inclusion in the numerical model of solidification, however, requires carrying out simulations including both the solidification and the stresses formation [8]. Thermo-mechanics of solidification is a very complex field, which consists a lot of phenomena, usually coupled [7]. A R C H I V E S O F M E T A L L U R G Y A N D M A T E R I A L S