Volume 28, Issue 3 (May 2000)
Evaluation of the Autofrettage Effect on Fatigue Lives of Steel Blocks with Crossbores Using a Statistical and a Strain-Based Method
A problem of fundamental and industrial interest is the effect of autofrettage on fatigue lives and the structural integrity of engineering components. The component considered is a steel block containing crossbores, a situation found in many industrial applications such as the fluid ends of positive displacement pumps. Twenty-one steel blocks containing intersecting perpendicular crossbores were autofrettaged with pressures ranging from 79 to 172 MPa. The specimens were subsequently fatigue tested on a specially designed test facility under 53 and 69-MPa pressures. Statistical procedures based on analysis of variance were used to analyze the effect of the different autofrettage pressure levels on fatigue lives of specimens. The reverse plasticity criterion was also used to investigate the fatigue enhancement limit of the autofrettage process. Results of the statistical methodology correlated with results of the reverse plasticity criterion showed the existence of an “optimal” autofrettage pressure.