For many years, Martinlamitz has successfully used MAGMASOFT® for designing and optimizing their casting designs. With the introduction of Autonomous Engineering, Martinlamitz uses these new capabilities wherever possible. Therefore, the previously calculated mold filling, solidification and cooling to shake-out of the casting were used to identify and investigate the residual stresses and the distortion of the casting based on the corresponding temperature fields.
For the calculation of stresses and distortion of the housing, in addition to the casting and the rigging, the influence of the constrained casting shrinkage caused by the internal core was also considered. In this context, the contact forces and the wall friction between the sand core and the casting were also determined. To describe the thermomechanical material behavior of GJS 500 ductile iron, the material data available in MAGMASOFT® and the strain rate-dependent creep model were used.
Already the first simulation revealed that the residual stresses arising during cooling in the mold are primarily formed due to the casting shrinking onto the sand core. After shake-out, a part of the residual stresses persists which lead to a deformation of the casting. Cutting off the braces results in the release of more residual stresses, thus leading to even more deformation in the casting. As a result, the two “ear” areas keep moving towards each other, leading to a significantly distorted casting. As a consequence, the required dimensional tolerance between both “ears” cannot be kept (Figure 4/ bottom image).