Influence of porosity on fatigue cumulative damage of sintered iron

Fatigue represents a common mechanical condition during service for materials used in structural components. This type of loading becomes particularly critical when alternating stress amplitude may be expected to vary, or change, in some way during the service life. Such variations and changes in load amplitude make the direct use of standard S-N curves inapplicable, because these curves are developed and presented for constant stress amplitude operation. In the present paper, results of cumulative damage under fatigue of porous materials are reported. The specimens used were produced by compacting and sintering iron powder. Their as-sintered porosity contents were P0 = 4.1 and 12.4 %. Uniaxial fatigue tests (tensile-compression) were carried out at room temperature on a hydraulic testing machine.