The use of powder metallurgy (P/M) materials and processes provides several advantages over the use of wrought materials and conventional manufacturing processes for producing cost effective, high volume, high strength automotive components. Most structural parts, however, will experience some kind of periodic loads during their life cycle that exceed normal service loads. These overloads have been shown by researchers to significantly affect fatigue life. In the present study a fatigue evaluation was conducted on laboratory specimens of powder metallurgy steel with a density of 7.2 g/cm3 to determine the effect of periodic compressive overloads on fatigue life. The base material used for the pressed and sintered samples was Distaloy HP-1 powder with a composition of 0.7 Cu-4.0 Ni-1.4 Mo-2.0 Cu %wt. Monotonic tensile values and microstructure of the test samples are characterized. Strain based constant amplitude, R = -1 , fatigue tests were used to obtain baseline strain-life properties and determine the cyclic stress-strain behavior of the material. A series of periodic compressive overload tests were compared to the baseline R = -1 strain-life curve. In addition, test results are compared to powder-forged 2% Cu steel. Results showed that a variable amplitude fatigue test history, consisting of a cmpressive overload cycle followed by smaller cycles, caused a fatigue strength reduction of 55% at 1.0x106 cycles when compared to the constant amplitude fatigue results.
The effect of periodic overloads on the fatigue behavior of powder metallurgy steel
2003
9 Seiten, 8 Bilder, 2 Tabellen, 13 Quellen
Conference paper
English
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