Topic
Paris' law
About: Paris' law is a research topic. Over the lifetime, 13815 publications have been published within this topic receiving 224818 citations. The topic is also known as: Paris-Erdogan law.
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TL;DR: In this paper, the cyclic σ-e curves of annealed and aged maraging steels were determined using incremental step testing and stable hysteresis loop tip measurements.
Abstract: The cyclic stress-strain curves, the low cycle and high cycle fatigue lives and the fatigue crack growth rates of annealed (1 h 820°C) and aged (3 h 480°C) maraging steel 300 were determined. Incremental step testing and stable hysteresis loop tip measurements were used to determine the cyclic σ-e curves. Both annealed and aged maraging steels were found to cyclically soften at room temperature over a plastic strain range from 0.1 to 20 pct. The S-N curves were determined from 10 to 107 cycles to failure by plastic strain controlled low cycle fatigue tests performed in air and load controlled high cycle fatigue tests performed in dry argon. The test results compared very well with the theoretical lifetime predictions derived from Tomkins’ theory. Fatigue crack growth rates were measured in air and dry argon for the annealed and aged alloys. Crack growth rates of annealed maraging steel were found to be equal to those of aged maraging steel at rates between 10-7 and 10-5 in./cycle. A significant difference in crack growth rates in the two environments was found at low stress intensity factor ranges, indicating a high susceptibility to corrosion fatigue in the presence of water vapor. The mechanisms of cyclic softening in the two alloys are discussed in terms of dislocations rearrangement in the annealed alloy and dislocation-precipitate interactions in the aged alloy.
55 citations
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TL;DR: In this article, variable-amplitude (VA) load spectra were used with periodic overload (OL) cycles added to constant amplitude (CA) cycles to obtain more detailed information on crack growth contributions of different load cycles.
Abstract: Fatigue crack growth tests were carried out on 2024-T3 and 7075-T6 centrally cracked specimens. Variable-amplitude (VA) load spectra were used with periodic overload (OL) cycles added to constant-amplitude (CA) cycles. The fatigue fracture surfaces were examined in the SEM to obtain more detailed information on crack growth contributions of different load cycles. The striation patterns could be related to the load histories. SEM observations were related with (i) delayed retardation, (ii) the effect of 10 or a single OL on retardation, (iii) crack growth during the ()L cycles, and (iv) crack growth arrest after a high peak load. Fractographs exhibited local scatter of crack growth rates and sometimes a rather tortuous 3D geometry of the crack front. Indications of structurally sensitive crack growth under VA loading were obtained. Fractography appears to be indispensable for the evaluation of fatigue crack growth prediction models in view of similarities and dissimilarities between crack growth under VA and CA loading.
55 citations
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TL;DR: In this article, an architectural approach for toughening discontinuously reinforced aluminum (DRA) alloys is described based upon exploiting the higher apparent toughness of thin DRA lamina to obtain a laminate of higher thickness and toughness.
55 citations
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TL;DR: In this paper, the authors used microscopic Digital Image Correlation (DIC) to examine the mechanisms of crack growth resistance and near-tip displacement distribution for cracks in human dentin that are subjected to opening mode loads.
Abstract: An understanding of the fatigue and fracture behavior of hard tissues (e.g., bone and tissues of the human tooth) is critical to the maintenance of physical and oral health. Recent studies suggest that there are a number of mechanisms contributing to crack extension and crack arrest in these materials, and that they appear to be a function of moisture and age of the tissue. An understanding of these processes can provide new ideas that are relevant to the design of multi-functional engineering materials. As a result, we have adopted the use of microscopic Digital Image Correlation (DIC) to examine the mechanisms of crack growth resistance and near-tip displacement distribution for cracks in human dentin that are subjected to opening mode loads. We have also developed a special compact tension (CT) specimen that permits evaluation of crack extension within small portions of tissue under both quasi-static and fatigue loads. The specimen embodies a selected portion of hard tissue within a resin composite restorative and enables an examination of diseased tissue, or portion with specific physiology, that would otherwise be impossible to evaluate. In this paper we describe application of these experimental methods and present some recent results concerning fatigue crack growth and stable crack extension in dentin and across the dentin-enamel-junction (DEJ) of human teeth.
55 citations
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TL;DR: In this paper, the influence of variable amplitude loading on fatigue crack growth has been reviewed, in particular the importance of residual stresses, fatigue crack closure, microstruture, geometry and environment on the growth of long, through-thickness cracks following overloads, underloads and overload-underload combinations in Mode 1 opening.
55 citations