Topic
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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TL;DR: In this article, a model for predicting the life of composite structures under constant amplitude and two-stress level fatigue loadings is extended and applied to structures subjected to randomly-ordered loading spectra.
Abstract: A previously developed model for predicting the life of composite structures under constant amplitude and two-stress level fatigue loadings is extended and applied to structures subjected to randomly-ordered loading spectra. The model is phenomenological and a limited amount of experimental data is required for its characterization. For uniaxially loaded laminates, this consists of static tension and compression strength distributions, S-N curves based on constant amplitude fatigue life distributions for two-to-three stress ratios, and a limited amount of two-stress level fatigue test results. The model is verified by comparing predicted fatigue life distributions to experimentally observed fatigue life data for a variety of laminates and load spectrums. Good correlation between theory and experiment is obtained for all loadings and laminates studied.
130 citations
TL;DR: In this article, the authors show that the addition of small volume fractions of multi-walled carbon nanotubes (CNTs) in the matrix results in a significant increase in the high-cycle fatigue life.
Abstract: Glass fiber polymer composites have high strength, low cost, but suffer from poor performance in fatigue. Mechanisms for high-cycle (>104 cycles) fatigue failure in glass fiber composites consist primarily of matrix-dominated damage accumulation and growth that coalesce and propagate into the fibers resulting in ultimate fatigue failure. This investigation shows that the addition of small volume fractions of multi-walled carbon nanotubes (CNTs) in the matrix results in a significant increase in the high-cycle fatigue life. Cyclic hysteresis measured over each cycle in real time during testing is used as a sensitive indicator of fatigue damage. We show that hysteresis growth with cycling is suppressed when CNTs are present with resulting longer cyclic life. Incorporating CNTs into the matrix tends to inhibit the formation of large cracks since a large density of nucleation sites are provided by the CNTs. In addition, the increase in energy absorption from the fracture of nanotubes bridging across nanoscale cracks and nanotube pull-out from the matrix is thought to contribute to the higher fatigue life of glass composites containing CNTs. High-resolution scanning electron microscopy suggests possible mechanisms for energy absorption including nanotube pull-out and fracture. The distributed nanotubes in the matrix appear to inhibit damage propagation resulting in overall improved fatigue strength and durability.
129 citations
TL;DR: In this article, the ion-nitriding properties of quenched and tempered AISI 4340 low alloy steel were investigated under different process parameters including time and temperature.
129 citations
TL;DR: In this paper, a topological design procedure, incorporating a finite element model, was proposed to produce the shape of the sample necessary to achieve the required stress state/pattern, and a forced vibration-based fatigue procedure for conducting the high cycle fatigue experiments with variable-amplitude loading.
129 citations
TL;DR: The development of spray atomization and collection processes was motivated by the severe problems of oxide contamination associated with quenched reactive metal powders as well as by the need to minimize the overall number of processing steps from the liquid metal to fully dense product, perhaps in the near-net shape state.
129 citations