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Cyclic Loading Conditions (cyclic + loading_condition)
Selected AbstractsEffect of Atmospheric Humidity on the Fatigue Crack Propagation Behavior of Short Cracks in Silicon NitrideJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2000Sotomi Ishihara The effect of the environment on crack-growth processes in silicon nitride was studied by investigating the static and fatigue crack-growth behavior of small surface cracks, as influenced by testing (i) in the ambient environment, (ii) in distilled water, (iii) under vacuum, and (iv) in toluene. A principal finding was that testing under cyclic conditions led to crack-growth rates that were much higher in air than in toluene, whereas testing under static conditions in air or toluene led to minor differences in the rate of static fatigue crack growth. This difference in sensitivity to the environment under static and cyclic loading conditions was attributed, in part, to a much-greater extent of microcracking at the surface ahead of the main crack in air under cyclic conditions, in comparison to that in other environments. This propensity for microcracking at the surface in air under cyclic conditions also was reflected in the aspect ratios of the crack shapes that developed. [source] Dynamic fatigue studies of ZnO nanowires by in-situ transmission electron microscopyPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7-8 2009Zhiyuan Gao Abstract The fatigue behavior of ceramic ZnO nanowires (NWs) has been investigated under resonance cyclic loading conditions using in-situ transmission electron microscopy (TEM). After mechanical deformation at the resonance frequency at a vibration angle of 5.2° for 35 billion cycles, no failure or any defect generations have been found. We believe that the dislocation-free nature of NWs and the large surface-to-volume ratio contribute to the NWs' ability to undergo deformation without fatigue or fracture, proving their durability and toughness for nanogenerators and nanopiezotronics. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fatigue behavior of filament-wound glass fiber reinforced epoxy composite tubes under tension/torsion biaxial loadingPOLYMER COMPOSITES, Issue 1 2007Dongtao Qi A study of filament-wound glass fiber/epoxy composite tubes under biaxial fatigue loading is presented. The focus is placed on fatigue lives of tubular specimens under tension/torsion biaxial loading at low cycle up to 100,000 cycles. Filament-wound glass-fiber/epoxy tubular specimens with three different lay-up configurations, namely [±35°]n, [±55°]n, and [±70°]n lay-ups, are subjected to in-phase proportional biaxial cyclic loading conditions. The effects of winding angle and biaxiality ratio on the multiaxial fatigue performance of composites are discussed. Specimens are also tested under two cyclic stress ratio: R = 0 and R = ,1. The experimental results reveal that both tensile and compressive loading have an influence on the multiaxial fatigue strength, especially for [±35°]n specimens. A damage model proposed in the literature is applied to predict multiaxial fatigue life of filament-wound composites and the predictions are compared with the experimental results. It is shown that the model is unsuitable for describing the multiaxial fatigue life under different cyclic stress ratios. POLYM. COMPOS. 28:116,123, 2007. © 2007 Society of Plastics Engineers [source] Accelerated fatigue properties of unidirectional carbon/epoxy composite materialsPOLYMER COMPOSITES, Issue 2 2006Hsing-Sung Chen It has been confirmed that polymer matrix composites possess viscoelastic behavior. This means that one could accelerate the fatigue testing by changing the stress amplitude, frequency, or temperature. This study is to investigate the accelerated fatigue properties, which are resulted from the viscoelastic behavior, of carbon/epoxy composites and to predict their fatigue life. For this purpose, a series of fatigue tests of unidirectional specimens are conducted at room temperature under different stress ratios and stress frequencies. A group of sigmoid S-N curves, which are suitable for the whole fatigue life, and the corresponding parameters are developed for different cyclic loading conditions. A transformation method, which can transform a reference S-N curve to the corresponding S-N curve of the assigned fatigue conditions, is established by the parameters. And this S-N curve can be utilized to predict the fatigue life of the composite at the assigned stress ratio or stress frequency. The comparison between the linear and sigmoid S-N curves is also carried out to show the advantages of the latter model in the whole fatigue life. POLYM. COMPOS., 27:138,146, 2006. © 2006 Society of Plastics Engineers [source] | ||||||||||