Residual Stress Measurement in Aluminum Engine Block

Residual stress distribution at the cylinder block wall in 1500cc class aluminum engine was measured using RESA in JRR-3 of JAEA. In order to increase neutron flux at the gauge volume measured, newly developed vertically focused collimator was employed. Since the grain size in cast aluminum engine block was large, the oscillation method was applied. The residual stresses near the surface layers of cylinder block wall were compressive all in the tangential, the thickness and the cylinder axial directions, but tensile in the middle part of cylinder block wall. This means the residual stress distributions are likely to be hydrostatic. The residual stresses in the tangential direction were not balanced in the cylinder block wall. If the residual stress distribution in the hoop direction is approximated by 2 dimensional power equation, the residual stresses on the cylinder wall surface is estimated as about -140MPa and the mean residual stress in the cylinder wall is 15MPa.