Residual stress measurement in engine block—an overview

Significant residual stresses are often generated during the manufacturing of cast Al-Si alloy engine blocks due to differential cooling rates, the mismatch in the thermo-physical properties of adjacent materials in direct contact and volumetric changes caused by solid-state phase transformations during cooling. These may be modified during heat treatment and operation. These residual stresses may lead to distortion (affecting performance and economy) or premature failure of the engine block. For this reason, it is of fundamental importance to have reliable numerical and experimental methods for characterizing the residual stresses in the engine blocks at several steps during the manufacturing process. Sectioning and neutron diffraction techniques have been widely used to determine the residual stresses in the engine blocks. Numerical techniques have been developed to predict these residual stress but require experimental validation. The authors reviewed several numerical and experimental studies of residual stress evolution in engine blocks and showed how the residual stresses, microstructures, and mechanical properties are correlated.