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1.
Pitting formation due to surface and subsurface initiated fatigue crack growth in contacting mechanical elements
Gorazd Fajdiga, Srečko Glodež, Janez Kramar, 2007, original scientific article

Abstract: A computational model for simulation of surface and subsurface initiated fatigue crack growth due to contact loading is presented. The model is based on fracture mechanics theory where the required materials properties are obtained from common fatigue tests. For computational simulations an equivalent model of two contacting cylinders is used instead of simulating theactual contact of mechanical elements. The discretised model with the initial crack on or under the surface is then subjected to normal contact pressure, which takes into account the EHD-lubrication conditions, and tangential loading due to friction between contacting surfaces. The model considers also the moving contact of mechanical elements and for the surface initiated crack also the fluid trapped in the crack. The virtual crack extension method, implemented in the finite element method is then used for simulating the fatigue crack growth from the initial crack up to the formationof the surface pit. The numerical results correspond well with available experimental data. The described model can be used for simulation ofpitting phenomenon of contacting mechanical elements like gears, bearings, wheels, etc.
Keywords: fracture mechnaics, machine elements, gears, contact fatigue, pitting, subsurface crack initiation, computational analysis
Published: 31.05.2012; Views: 1294; Downloads: 71
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2.
Effect of residual stresses on the fatigue crack propagation in welded joints
Nenad Gubeljak, Jožef Predan, Reinhard Pippan, Maks Oblak, 2005, original scientific article

Abstract: The effect of residual stress on the fatigue crack growth was investigated forcyclic tension. Three-point bend specimens were used with through thicknessnotches at the center line of the welded joint. The experiments were performed for different load amplitudes and load ratios under conditions of small-scale yielding. The influence of the residual stresses on fatigue crack growth was estimated by experimentally observed fatigue crack growth rate and measurement of residual stresses at the surface of specimen. This paper describes an approach taken in two models to estimate the residual stress effect on fatigue crack propagation and to predict remaining service life of awelded structure.
Keywords: fracture mechnaics, fatigue crack, crack growth, residual stresses, fatigue crack growh rate, X-ray
Published: 01.06.2012; Views: 1180; Downloads: 57
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