Stress Mapping of the Journal Region of Cast Aluminum Engine Blocks User Project with Ohio State University, J. Williams, R. DeNeff of Honda , and D. Wiesner,  T. Ely, and T. R.Watkins
	A researcher from the Ohio State University visted the Residual Stress User Center to characterize the residual stresses in as-cast and annealed aluminum engine blocks from Honda-Anna, OH.  Residual stresses in cast aluminum engine blocks were mapped using x-ray diffraction with the large sample stress analyzer – gantry system.  Residual stresses were identified to be the result of differential cooling during processing which distort critical features during machining.  This makes maintaining dimensional tolerances (i.e. bearing journals; Fig 5.8) difficult.  The current solution is to subject the engine blocks to a T5 stress relief treatment prior to machining.  While this provides residual stress reduction, it adds complexity to the process (major production volume limiting step).  Alternate stress relief cycles (with greater throughput) are desired. Automated coordinate-mapping of the radial and hoop stresses was performed.  Data analysis was performed on the aluminum (311) reflection using new LabVIEW software, developed for improved efficiency and quality of data analysis.  Analysis of the hoop stress results (Fig 5.9) showed an overall reduction in compressive stresses and increased uniformity in the stress levels over the mapped surface with increase heat-treatment.  The radial stress results, however, shifted from compressive to tensile with no change in uniformity with increasing heat treatment.  This shift may be  attributed to the complex geometry of the engine block resulting in the radial direction being constrained.   Figure 5.8 - Left: An engine block mounted on XYφ specimen translation stage with the stress analyzer position above. Right: The main bearing saddle area was the area of interest for stress mapping. Figure 5.9 – Contour maps of residual stress magnitude and sign in the journal region of the cast aluminum engine blocks as a function of heat treatment temperature.
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