by University of Aston in Birmingham. Department of Metallurgy in Birmingham .
Written in English
|Series||Ph. D thesis|
The metallurgical variables having the most pronounced effects on the fatigue behavior of carbon and low-alloy steels are strength, ductility, cleanliness, residual stresses, surface conditions, and aggressive environments. The article discusses the stress-based and strain-based approach to fatigue. Book: Fatigue handbook: Offshore steel structures. Fatigue handbook: Offshore steel structures. Evaluation of stress concentrations in simple and complex Sharp, J V. A literature review of fatigue crack growth rates (FCGR) has been performed for steels in air and seawater environments, either free corroding or with applied. The initiation of fatigue cracks is an event whose very definition is strongly linked to the size scale of observation. For example, materials scientists are likely to consider the nucleation of flaws along persistent slip bands as the initiation stage of fatigue failure, whilst a mechanical engineer may associate the resolution of crack detection with the threshold for crack by: 6. Fatigue crack initiation at a PSB. FCP 12 Effects of strength and ductility 1 steels all have about the same crack growth rates Behavior of Structural Materials. stress concept; consequently, fatigue usually begins at stress concentrators which are most frequently at the surface of a component.!
Lower compressive residual stresses near the surface result in easier crack initiation and faster fatigue crack growth. Hence, further study is necessary to distinguish the effects of these two phenomena and consider them simultaneously to have a better understanding of the fatigue crack initiation and propagation in SLM steels. The simplest way to account for stress concentration would be to use a modifying factor that this the inverse of the theoretical stress concentration factor: n ASM International , where S is the adjusted fatigue strength at the given number of cycles, S n ' is the calculated fatigue strength without stress concentration, and K t is the. For a totally brittle material in which the elastic stress concentration factor K t might be assumed to have its full effect, e.g. K t = 2, the fatigue life or notched endurance limit would be reduced accordingly. For materials with varying plastic flow capabilities, the effect of stress-raisers produces notched endurance limits somewhere between the un-notched value and that of the. Fatigue failure of Babbitt metal is similar to any other metal fatigue. The crack initiation point can be stress concentration caused by an embedded particle, a high-stress region due to shaft misalignment, high temperature, and so forth. The fatigue crack may seem to open in the direction of rotation.
The fatigue limit for crack initiation, σw1, is lower than that for fracture, σw2. At stress amplitudes between σw1 and σw2, a nonpropagating fatigue crack is formed at the notch root. Tanaka and Akiniwa () proposed the R -curve method to estimate the fatigue strength reduction . This report provides an overview of fatigue crack initiation in austenitic stainless steels (SSs) in LWR coolant environments. The existing fatigue e–N data are analyzed to define key material, loading, and environmental parameters that influence the fatigue lives of these steels. Schematic example of mechanisms leading to a fatigue crack initiation (a) extrusion and intrusion in slip region due to cyclic stress (b) slip band intrusions and extrusions prior to crack initiation (Note the stress concentration is formed on the surface in this process). . This study investigated the fretting wear and fatigue of full-scale railway axles. Fatigue tests were conducted on full-scale railway axles, and the fretting wear and fretting fatigue in the fretted zone of the railway axles were analysed. Three-dimensional finite element models were established based on the experimental results. Then, multi-axial fatigue parameters and a linear elastic.