OPTIMIZATION OF HYDRAULIC CYLINDER HOUSING

This paper concerns the optimization of the fatigue-critical part of a hydraulic cylinder. The investigation includes optimization, fatigue testing, residual stress measurements, life predictions and, finally, reliability computations. The optimization reduced the critical parameter, the stress intensity factor in the end weld root, by 40%. The fatigue tests verified this reduction. Life predictions based on available da/dN data, combined with computed and tabulated stress intensity factor solutions, were in good agreement with the fatigue test data. Fractography of the fatigue sites revealed the existence of initial cracks of size 0.02 to 0.06 mm in all the welded joints examined. Reliability computations based on the test results and long-term load data demonstrate the type of results that are of major interest for designers.