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Stress relaxation

About: Stress relaxation is a research topic. Over the lifetime, 12959 publications have been published within this topic receiving 270815 citations.


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Journal ArticleDOI
TL;DR: In this article, the authors evaluated the creep behavior and the microstructural evolution of 9Cr-Mo-Nb-V (T91) steel by means of short term constant load creep tests and TEM analysis.
Abstract: The creep behaviour and the microstructural evolution of a 9Cr–Mo–Nb–V (T91) steel were extensively evaluated by means of short term constant load creep tests and TEM analysis. Statistical analysis of the microstructural data revealed that the precipitated phases M23 C6 (where M is a metal, mainly Cr or Fe) and MX (where M is Nb or V, and X is C and/or N) were subject to coarsening during creep exposure. The coarsening law and its dependence on applied stress were identified, and the model was used to predict the magnitude of the Orowan stress at the time corresponding to the minimum creep rate. The minimum creep rate dependence on applied stress at 873 K was described by incorporating the threshold stress concept in a power law with stress exponent n = 5. In the resulting phenomenological model, the strengthening effect of the dispersed phases was thus expressed by a threshold stress proportional to the Orowan stress.

92 citations

Journal ArticleDOI
TL;DR: In this paper, a laser reflection technique is used to investigate the relaxation of SiO2 film stress which occurs during the dry thermal oxidation of Si between 700 and 1000 °C.
Abstract: A laser reflection technique is used to investigate the relaxation of SiO2 film stress which occurs during the dry thermal oxidation of Si between 700 and 1000 °C. Included is a determination of the stress distribution in the oxide by two independent methods: (1) measurement on oxides of various thicknesses from 100 to 800 A, and (2) repeated stress measurements on chemically thinned SiO2 films, viz. etch‐back analysis toward the interface. Agreement is found between these experiments. These thin film stress measurements are achieved by the use of ultrathin Si substrates (75 μm). Essentially, an increase in film stress with decreasing film thickness is observed. Rapid stress relaxation is observed for all temperatures studied and is attributed to a time‐dependent oxide viscosity. The influence of these measured properties on the kinetics of Si oxidation is discussed.

92 citations

Journal ArticleDOI
TL;DR: In this paper, the authors carried out controlled-stress experiments in addition to the conventional controlled-rate measurements to probe the nature of nonlinear flow behavior of entangled 1,4-polybutadiene solutions.
Abstract: We have carried out controlled-stress experiments in addition to the conventional controlled-rate measurements to probe the nature of nonlinear flow behavior of entangled 1,4-polybutadiene solutions. The flow responses are found to be drastically different depending on whether the shear flow is imposed by applying a constant torque or a constant velocity on one of the two surfaces in a cone−plate flow cell. When the applied shear stress is of a comparable magnitude to the elastic plateau modulus of the entangled solutions, a sharp yieldlike constitutive transition is observed, revealing a discontinuous relationship between the shear rate and the shear stress. Following such an entanglement−disentanglement transition (EDT), the chain orientation appears to further increase as a function of time as evidenced by the rising normal stress N1, reflecting a plausible coil−uncoil transition (C−UCT). The relaxation of N1 consists of an initial rapid decay, likely due to chain recoil from the C−UCT and a subsequent...

92 citations

Journal ArticleDOI
TL;DR: In this paper, a single shear band in a Zr-based metallic glass was studied and the authors found that cavities are a signature of a shear-band-to-crack transition, which is supported by stress fields known to develop ahead of mixed mode I and II crack tips.

92 citations

Journal ArticleDOI
TL;DR: In this paper, the grain-boundary sliding during superplastic flow of the Pb-Sn eutectic was observed and a threshold stress of 1.3×106N m−2 was observed for the onset of super-plastic deformation.
Abstract: Dynamic observations of grain-boundary sliding during superplastic flow of the Pb-Sn eutectic are reported. These observations confirm the postulate that the dominant deformation mode during superplastic flow is grain-boundary sliding with localized deformation necessary to maintain grain coherency. Extensive grain-boundary sliding is also observed when the strain-rate and/or grain size is outside the superplastic flow regime. Stress relaxation tests were also carried out on the Pb-Sn eutectic. These tests provide data on the activation energy (45±5 kJ mol−1), grain-size dependence (d−3), and stress dependence of superplastic flow in this alloy. A threshold stress of 1.3×106N m−2 for the onset of superplastic deformation is also observed.

92 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023145
2022390
2021266
2020276
2019270
2018281