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Fatigue limit

About: Fatigue limit is a research topic. Over the lifetime, 20489 publications have been published within this topic receiving 305744 citations. The topic is also known as: endurance limit & fatigue strength.


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Journal ArticleDOI
TL;DR: In this paper, an explanation for non propagating fatigue cracks is presented based on the criterion that once the value of a particular strain intensity factor reduces to the threshold value for the material the crack should stop.

865 citations

Journal ArticleDOI
TL;DR: In this article, the effects of defects, inclusions and inhomogeneities on the fatigue strength of metals are reviewed, from the Isibasi model and the Frost model to recent models based on fracture mechanics.

789 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of fabrication orientation, surface polishing, and hot isostatic pressing upon mechanical behavior of four metallic alloys fabricated with layered, laser-heated methods of additive manufacturing (AM) was compared to that of similar alloys produced with conventional methods (wrought and machined).
Abstract: Mechanical behavior of four metallic alloys fabricated with layered, laser-heated methods of additive manufacturing (AM) was compared to that of similar alloys produced with conventional methods (wrought and machined). AM materials were produced by a leading commercial service provider, as opposed to incorporating material specimens produced by unique or specially-adapted equipment. The elastic moduli were measured in flexure, stress–strain characteristics were measured in tensile deformation, and fatigue strengths were measured in fully reversed bending. The effects of fabrication orientation, surface polishing, and hot isostatic pressing upon mechanical behavior were studied. The fatigue strengths exhibited by SLM AlSi10Mg and DMLS Ti6Al4V in the as-fabricated condition proved to be significantly inferior to that of conventional material. These lower fatigue strengths are a consequence of multiple fatigue cracks initiating at surface defects, internal voids and microcracks, and growing simultaneously during cyclic loading. Measured fatigue strengths of DMLS 316L and 17-4PH approached those of corresponding wrought materials when subjected to principal stresses aligned with the build planes. When cyclic stresses were applied across the build planes of the DMLS stainless steels, fatigue fractures often developed prematurely by separation of material. Post-processing the DMLS Ti6Al4V and SS316L with hot isostatic pressure elevated the fatigue strength significantly. Measurements of surface roughness with an optical profilometer, examinations of the material microstructures, and fractography contribute to an understanding of the mechanical behavior of the additive materials.

720 citations

Journal ArticleDOI
Abstract: Under repeated stressing, cracks in a specimen of vulcanized rubber may propagate and lead to failure. It has been found, however, that below a critical severity of strain no propagation occurs in the absence of chemical corrosion. This severity defines a fatigue limit for repeated stressing below which the life can be virtually indefinite. It can be expressed as the energy per unit area required to produce new surface ( T 0 ), and is about 5 x 10 4 erg/cm 2 . In contrast with gross strength properties such as tear and tensile strength, T 0 does not correlate with the viscoelastic behaviour of the material and varies only relatively slightly with chemical structure. It is shown that T 0 can be calculated approximately by considering the energy required to rupture the polymer chains lying across the path of the crack. This energy is calculated from the strengths of the chemical bonds, secondary forces being ignored. Theory and experiment agree within a factor of 2. Reasons why T 0 and the gross strength properties are influenced by different aspects of the structure of the material are discussed.

691 citations

Journal ArticleDOI
TL;DR: In this paper, structural and functional fatigue of NiTi shape memory alloys is investigated and four cases of fatigue are discussed: (1) the evolution of the stress-strain hysteresis in low cycle pull-pull fatigue of pseudo-elastic NiTi wires.
Abstract: Cyclic loading is one of the generic characteristic features of many of the present and potential future applications of NiTi shape memory alloys, no matter whether they exploit mechanical (pseudo-elasticity) or thermal shape memory (one and two way effect). Cyclic loading may well be associated with structural and functional fatigue, which both limit the service life of shape memory components. By “structural fatigue” we mean the microstructural damage that accumulates during cyclic loading and eventually leads to fatigue failure. There is a need to understand how microstructures can be optimized to provide good fatigue resistance. The term “functional fatigue” indicates that shape memory effects like the working displacement in a one way effect (1WE) actuator or the dissipated energy in a loading–unloading cycle of a pseudo-elastic (PE) damping application decrease with increasing cycle numbers. This is also due to a gradual change in microstructure. In both cases it is important to know how fatigue cycling affects shape memory properties. The present paper considers structural and functional fatigue of NiTi shape memory alloys. It discusses four cases of fatigue in NiTi shape memory alloys: (1) The evolution of the stress–strain hysteresis in low cycle pull–pull fatigue of pseudo-elastic NiTi wires. (2) Bending–rotation fatigue rupture of pseudo-elastic NiTi wires. (3) Strain localization during the stress induced formation of martensite. (4) Generic features of functional fatigue in NiTi shape memory actuator springs. The paper shows that fatigue of shape memory alloys is a fascinating research field and highlights the need for further work in this area.

661 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023248
2022586
2021616
2020684
2019749
2018712