Nondestructive Characterization of Residual Stresses on Cylinder Liners and Blocks via X-ray Diffraction Techniques

It is well known that machining operations produce surface conditions that can either enhance or debit the fatigue life of production components. Furthermore it has been well established that the thermal gradients produced during the solidification process of a casting operation can also generate detrimental residual stress loads. Cast cylinder blocks can sustain life limiting stress gradients from these processes. Due to their complex geometry it has historically been very difficult if not impossible to fully characterize the residual stresses present at critical locations in cylinder blocks. Recent advances in x-ray diffraction (XRD) have reduced the minimum clearance required for an accurate measurement from 200mm to 70mm. This now allows XRD to be used as a non destructive test (NDT) on features such as cylinder liners and bores, bulk heads and assembled journals. These advancements will allow OEM's and their suppliers to improve fatigue life and product quality by characterizing and managing the residual stresses present at various stages of production. Beyond production this technology will allow OEM's to measure residual stresses at different stages of a blocks operational life. Such information can be used to help design engine blocks with superior performance and life expectancy.