Thermal Stress Analysis of Residual Stress in a Cylindrical Aluminum Casting with Cast-in GCI Liner, Taking Recovery Behavior Effect into Account

摘要

Most aluminum cylinder blocks produced using high-pressure or low-pressure die-casting processes require gray cast iron liners (GCI liners) to compensate for their insufficient wear resistance and heat resistance of the Al-Si-Cu alloys. However, the cast-in liners cause excessive residual stress at the cylinder bore region. The resultant residual stress induces distortion of the cylinder liner. These inconveniences hinder development of more efficient engines. Therefore, an accurate thermal stress analysis technique has been sought to predict the residual stress and distortion of the cylinder liner. For accurate thermal stress analysis, we have already developed an elastoplastic-creep constitutive equation for which the inelastic strain developed at high temperatures does not contribute to strain hardening that occurs at low temperatures by duplicating the recovery behavior. Our earlier investigation using this equation has already revealed that incorporation of the recovery in the alloy constitutive equation is effective for improving the prediction accuracy of the thermal stress developed during casting. However, this conclusion was obtained only for a simple shape casting with a uniaxial thermal stress state. Effects of the developed constitutive equation have not been discussed for a casting closer to an actual cylinder block. For this study, a cylindrical aluminum casting with GCI (ISO 300) insert was produced. Then, the circumferential strain of the GCI liner was measured in-situ during casting. Measurements were taken of the residual stresses of the cylindrical aluminum casting and GCI liner, and of the liner deformation at a room temperature. The experimentally obtained results supported a discussion of the predictive accuracies of the elastoplastic-creep constitutive equation and the classical elastoplastic constitutive equation. A comparison revealed that the elastoplastic-creep constitutive equation for the aluminum casting has better predictive accuracy than the classical elastoplastic equation for residual stress, liner deformation, and the circumferential strain of a GCI liner during casting. Investigation of the simulated strain components of the cylindrical aluminum casting during casting indicated incorporation of the recovery in the alloy constitutive equation as a main factor improving the predictive accuracy. (C) The Minerals, Metals & Materials Society and ASM International 2018.