Influence of plastic predeformation on the fatigue strength of compressor blades with defects

We study the influence of plastic predeformation by bending to create deep residual compressive stresses on the fatigue strength of 13Kh11N2V2MF steel specimens and compressor blades with cut and stamped V-shaped and semicircular defects, and also the use of design-based redistribution of the stresses in the blade (offsetting toward the edges) for the retardation of cracks in the stress concentrators. It is found that plastic predeformation increases the fatigue strength by about 20%, while offsetting with the creation of a compressive mean stress _m = –300 MPa in the defect region increases the fatigue strength by 2–2.5 times. We examine schemes for calculating the fatigue strength with account for the residual and mean stresses, and also examine the defect creation technique. Recommendations are made for increasing the strength of compressor blades with defects.Translated from Problemy Prochnosti, No. 10, pp. 76–88, October, 1994.