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Construction and Materials Defect
Published in Mavis Sika Okyere, Mitigation of Gas Pipeline Integrity Problems, 2020
The significance of the fatigue limit is that if the material is loaded below this stress, then it will not fail, regardless of the number of times it is loaded. In accordance with IGE TD/1, 15,000 cycles at 125 N/mm2 have been set as the maximum permissible fatigue life.
Creep and Fatigue Behavior of Materials
Published in Snehanshu Pal, Bankim Chandra Ray, Molecular Dynamics Simulation of Nanostructured Materials, 2020
Snehanshu Pal, Bankim Chandra Ray
The parameters of Basquin equation are as follows: σa is stress amplitude, Δεe/2 is elastic strain amplitude, E is the modulus of elasticity, σ′f is fatigue strength coefficient, b is fatigue strength exponent, N is the number of cycle to failure, and p and c are empirical constants. The ability of materials to withstand high stresses without breaking for infinite number of cycles is known as fatigue limit/endurance limit/fatigue strength. In addition, the corresponding number of cycles is known as fatigue life (i.e., number of cycles handled by material before failure). Endurance ratio is obtained by dividing the fatigue stress of a material by its tensile stress.
Stress Method
Published in Eliahu Zahavi, Vladimir Torbilo, Fatigue Design, 2019
Eliahu Zahavi, Vladimir Torbilo
The fatigue limit (also called endurance limit) is defined as the maximum value of stress amplitude at zero mean stress which can be repeated an infinite number of times on a test specimen without causing a failure. This value forms a mechanical property specific for each material. The fatigue limit depends on the loading mode (the result is different for specimens subjected to rotating bending, axial loading, or torsion) and it is influenced by the size and surface condition of the specimen. The test results used in design of machine parts combine these effects.
Effect of CFRP strengthening systems on the fatigue limit of reinforced concrete beams
Published in Structure and Infrastructure Engineering, 2021
Tamer Eljufout, Houssam Toutanji, Mohammad Al-Qaralleh
Fatigue limit is a strength property that represents the maximum possible applied cyclic stress range without causing fatigue failure of a material (Dowling, 2007). The Up-and-Down method, also known as the staircase method, is one of the widely used conventional methods for determining the fatigue limit (Lipski, 2014). In this method, the specimen is tested under constant cyclic stress range slightly higher than the estimated fatigue limit. If the specimen does not fail before the designed number of cycles of the fatigue limit, another specimen is tested at a higher stress range. However, if the specimen fails before the completion of the designed number of cycles, then the next specimen is tested at a lower stress range. This method is costly and time-consuming since several fatigue tests are needed to be performed. Hence, different accelerated fatigue methods were developed for reducing the number of specimens and shortening the testing duration (Nicholas, 2006; Zhang, Poirier, & Barr, 2003).
Review on effect of Ti-alloy processing techniques on surface-integrity for biomedical application
Published in Materials and Manufacturing Processes, 2020
Dental implants experience periodic load due to chewing; this results in microstructural non-homogeneities. The identification of fatigue resistance of a material is a complex task due to its dependency on various factors. Fatigue properties of the material are mainly based on alloying elements and manufacturing methods. Fatigue strength is a primary factor that affects life of implants. Gepreel et al.[73] explained that testing of an implant under loading conditions and simulated implantation is a complicated and expensive process. No standard is available to evaluate the fatigue resistance of a material. Experimental results showed that the shot peening process improved fatigue limit and also provided a proper balance for residual surface stresses. (Ayllon et al.[48]) investigated fatigue characteristics of dental implants made by pure Ti. The effect of stress concentration on surface treatment and the external thread was analyzed. Figure 6 shows fatigue test results for experimentally obtained fatigue curves of Ti without and with surface treatment. Figure 7 shows the method by which the load was applied. Experimental results proved that surface treatment reduces the fatigue strength of samples.
The effect of saline environment on the fatigue behaviour of HVOF-sprayed WC–CrC–Ni coatings
Published in Surface Engineering, 2018
Alin Constantin Murariu, Anghel Vasile Cernescu, Ion-Aurel Perianu
Fatigue strength is a key mechanical property to be considered if components were subjected to cyclic loading. The fatigue strength of coatings can be influenced by the mechanical loading, material metallurgical structure and by the internal residual stress. The environmental operating conditions and defects play a significant role in fatigue limit reduction. Thus, besides corrosion and erosion, material fatigue is the main degradation mechanism that could lead to early failure of components. Studies on wear and corrosion resistance, the correlation between structural and mechanical characteristics of coatings [21–26] and also on fatigue strength of cold-sprayed metals and alloys, and HVOF thermally sprayed WC compounds are of highly practical interest [27–30]. However, the experimental research could be ampler due to the complexity of the process parameters [31], the large range of particle size and distribution [32], different chemical composition and production method of the sprayed powder, various mechanical properties of the substrate or post-treatment used [33,34] and other such factors. This paper presents the effect of saline environment on the fatigue behaviour of WC–CrC–Ni coatings obtained by the HVOF thermal spraying process.