Abstract:

Megacasting during rapid filling and cooling processes inevitably generates defects， which significantly impact the mechanical properties of castings. However， it is difficult for existing mechanical analysis models to accurately predict the properties in defective castings， posing substantial challenges to the design of structurally safe castings. To solve the problem， a constitutive model and a fracture criterion of cast aluminum considering defects are proposed in this paper. Five different shapes of samples are cut from different locations of the megacasting floor， and experimental tests are carried out. The defect information on the fracture sections is statistically analyzed using scanning electron microscopy. Based on the stress-strain curves of the standard tensile samples， a constitutive model considering defects and saturating stresses is proposed to accurately characterize the strain-hardening properties. Based on the existing Modified Mohr-Coulomb （MMC） fracture criterion， an improved MMC model considering defects and stress states is proposed， and the parameters are calibrated by four different shaped samples. To validate the effectiveness of the proposed model， a comparative analysis between experimentation and simulation is conducted. The results show that the proposed constitutive model has a high fitting accuracy compared with the traditional hardening model. The load-displacement curves of the tests and simulation of different samples are in good agreement， which verifies the validity of the proposed fracture model. This study provides a novel approach to accurately predicting the mechanical properties of megacasting aluminum alloys.

Key words: megacasting, non-heat-treated alloy, constitutive model, fracture criterion