FATIGUE BEHAVIOR OF A SINTERED HIGH-STRENGTH STEEL

Stress-controlled fatigue tests were performed on a common high-strength powder metallurgy (PM) alloy steel (Fe-4 w/o Ni-1.5 w/o Cu-0.5 w/o Mo-0.6 w/o C) to provide fatigue strength data at 10(7) cycles. Concurrently, finite element calculations on the stress concentration factor Kt and the volume V-90 exposed to stresses >= 90% of the maximum principal stress were performed. Eight different types of specimens were tested under axial, bending, and torsional loading. From the nominal fatigue strength at 50% failure probability (sigma(A)) and the stress concentration factor (K-t), the local fatigue strength (K-t sigma(A)) was determined and plotted as a function of V-90 in double logarithmic coordinates. A density-modified three-parameter Weibull distribution describes the results at an equal stress ratio (R), irrespective of the loading mode, specimen size, or shape and sintered density, over more than five orders of magnitude in V-90. These findings suggest a new interpretation of the results from notched specimens and permit a universally applicable calculation of component-fatigue performance.