Fatigue Crack Initiation from Microstructurally Small Vickers Indentations

Abstract

The resistivity of a coarse grain steel against fatigue crack initiation in presence of micro-defects is discussed. Samples of material with martensitic microstructure were prepared by adequate thermal treatment. Microstructurally small Vickers indentations were used as artificial micro-defect. The compressive residual stresses are due to the irreversibility of plastic deformation. The moment of indenting enables to prepare samples with and without effects of residual stresses. The stress level for crack initiation depends on the actual indentation size. The location of initiated cracks is affected by the presence and character of residual stresses.

Keywords

• micro-defect
• coarse-grain heat-affected zone
• crack initiation and growth
• stress-concentration
• fatigue limit