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Mechanism of Corrosion
Published in Harry J. Meigh, Cast and Wrought Aluminium Bronzes, 2018
Metals can fail by fatigue as a result of the repeated imposition of cyclic stresses well below those that would cause failure under constant load. In many corrosive environments the cyclic stress level to produce failure is further reduced, the failure mechanism then being termed corrosion fatigue. The relative contributions to the failure made by the corrosion factor and the fatigue factor depend upon the level of the cyclic stress and upon its frequency, as well as upon the nature of the corrosive environment. Under high frequency loading conditions such as may arise from vibration or rapid pressure pulsing due to the operation of pumps, etc., the corrosion resistance of the alloy is of less importance than its mechanical strength but under slow cycle high strain conditions both these properties become important.
Fracture, fatigue, and creep of metals
Published in Gregory N. Haidemenopoulos, Physical Metallurgy, 2018
Several types of fatigue are encountered in engineering. Mechanical fatigue is associated with a material subjected to a cyclic stress or strain. When at the same time the material is exposed at high temperatures, then the behavior is characterized as creep-fatigue. When the material is subjected, concurrently, to both cyclic loading and cyclic heating or cooling, the behavior is characterized as thermo-mechanical fatigue. When cyclic loading takes place in a corrosive environment, then it is characterized as corrosion fatigue. Cyclic loading with simultaneous sliding or rolling between two metallic surfaces results in sliding contact fatigue or rolling contact fatigue respectively. Finally cyclic loading with simultaneous relative oscillatory sliding friction between two metallic surfaces causes fretting fatigue. The present chapter deals primarily with mechanical fatigue. For the other types of fatigue the interested reader is advised to consult the suggested reading list at the end of this chapter.
Stress–strain–strength of soil
Published in Hsai-Yang Fang, John L. Daniels, Introductory Geotechnical Engineering, 2017
Hsai-Yang Fang, John L. Daniels
Fatigue behavior: Fatigue properties deal with the behavior of materials when subjected to repeated loads. The cyclic stressing of materials usually leads to a brittle type fracture (Ch. 8) if the magnitude of cyclic stress is sufficient. (a) The fatigue strength of a material is the maximum alternating value of stress that a material can withstand for a specific number of cycles without failure. Fatigue strength will usually be applied to materials that do not exhibit an endurance limit; (b) The fatigue limit, sometime referred to as endurance limit, of a material is the maximum value of alternating stress that a material can withstand an infinite number of times without failure, and (c) Fatigue life is the number of cycles of alternating stress of a specified magnitude that are required to fracture a material.
Effect of Expanded Graphite on the Tribological Behavior of Tin–Bronze Fiber Brushes Sliding against Brass
Published in Tribology Transactions, 2020
Bo Luo, Chengshan Liu, Xinli Liu, Lei Zhang
The most common types of wear between metal are adhesion, fatigue, abrasion, and corrosion (Braunovic, et al. (19)). Adhesive wear results from shear of the friction junctions that often involve higher friction force and material loss. A remarkable feature of adhesive wear is that materials transfer from one surface to another due to regional bonding between the contact surfaces (Kestursatya, et al. (23)). Strong adhesion occurs easily at the interface of two materials with similar composition and hardness. Hence, the tin–bronze fiber brush without EG sliding against a brass disc presents an extremely high friction coefficient and wear rate (1.02 and 1.6 × 10−5 mm3/Nm), and material transfer and fish-scale-like structures were observed on the worn surface. Fatigue is the result of a change in the material state due to cyclic stress, which leads to progressive fracture (Moshkovich, et al. (24); Seo, et al. (25)). During periodic sliding, the adhesive shearing force is so strong that fatigue cracks are initiated easily at the severe adhesion region where the maximum tangential stress or tensile strain takes place, as displayed in Figs. 9b and 9d. The origination and propagation of fatigue cracks led to delamination of the large flaky debris shown in Figs. 11b and 11d. Theoretical and experimental studies show that the point of maximal shear strength emerges to the surface when the friction coefficient is greater than 0.3 (Braunovic, et al. (19)).
Effect of organic content and frequency on degradation and pore pressure in marine organic soils
Published in Marine Georesources & Geotechnology, 2018
Wei Xiao, Yue Gui, Gui-Zhong Xu
Considerable investigations have been made in understanding the fundamental aspects of the cyclic degradation and the pore water pressure change in soils in relation to the design of foundations for offshore structures subjected to cyclic ocean wave loadings or earthquake loadings. Mortezaie and Vucetic (2013) proposed that the cyclic degradation and the cyclic pore pressure could be generally evaluated on the basis of results from either the strain-controlled or the stress-controlled cyclic laboratory tests. In the procedure based on stress-controlled cyclic test, the cyclic stress amplitude is maintained constant, while in the method based on the strain-controlled cyclic test, the cyclic strain amplitude is kept constant.
Fatigue failure simulation of a double-lap composites-metal bolted joint structure
Published in Mechanics of Advanced Materials and Structures, 2021
Chi Hou, Jing Qiao, Wenzhi Wang, Chao Zhang
The method of fitting the parameters in the modified fatigue damage model is very similar to that of the original Lemaitre damage model, which is clearly discussed in [15]. The static or plastic parameters such as yield stress or Young’s modulus could be obtained by tension stress–strain curves. The low cycle fatigue parameters could be obtained from cyclic stress-strain curves and strain-life data. The high cycle fatigue parameters could be obtained from S-N curves.