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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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TL;DR: In this article, the mean density of mobile dislocations in a crystalline solid increases linearly with plastic strain for small strains and decays exponentially for large strains, all at constant stress and low temperatures.
Abstract: Arguments are presented which conclude that the mean density of mobile dislocations in a crystalline solid increases linearly with plastic strain for small strains and decays exponentially for large strains, all at constant stress and low temperatures. The resulting analytic expression combined with the strain‐rate equation can be integrated explicitly in terms of tabulated exponential integral functions. This creep equation has a general form that is consistent with many experiments and detailed comparison with a particularly well‐documented experimental curve yields quantitative agreement. The large strain limit of the proposed creep equation is the familiar logarithmic creep law. A simple transformation of the creep equation yields the shape of a slowly propagating plastic front, and it is shown that the predicted shape corresponds to experimental observations for mild steel. The lengths of the incubation periods that precede fast flow, as predicted by the equation, have a stress dependence that agrees...

80 citations

Book
01 Oct 1982
TL;DR: A review of the state-of-the-art results can be found in this article, where the authors discuss the nature of residual stress and its measurement, as well as the effect of temperature on stress relaxation.
Abstract: Session I.- The Nature of Residual Stress and Its Measurement.- Session II.- Thermal and Transformation Stresses.- Load Induced Residual Stress Changes in Carburized Steel Computations and Experiments.- Residual Stresses and Distortion in Weldments-A Review of the Present State-of-the-Art-.- Thermal Modifications of Welding Residual Stresses.- Shot Peening and Residual Stresses.- Session III.- Measurement of Throughwall Residual Stresses in Large-Diameter Piping Butt Weldments Using Strain-Gauge Techniques.- X-Ray Methods for Measuring Residual Stress.- Measurements of Stress in the Interior of Solids with Neutrons.- Session IV.- Mechanical Relaxation Response of 21/4 Cr-1 Mo Steel.- Effect of Temperature on Stress Relaxation of Several Metallic Materials.- Thermal Relaxation in Autofrettaged Cylinders.- Session V.- The Numerical Simulation of Crack Growth in Weld-Induced Residual Stress Fields.- Linear Elastic Fracture Mechanics and Fatigue Crack Growth-Residual Stress Effects.- Stress Corrosion Crack Growth in the Presence of Residual Stresses.- The Relaxation of Residual Stresses During Fatigue.- Session VI.- The Generation of Residual Stresses in Metal-Forming Processes.- Stress Relaxation in Spring Materials.- Problems with Residual Stress in the Railroad Industry.- Measurement of Residual Stresses in Ammunition.- Session VII.- X-Ray Residual Stress Measurement Systems for Army Material Problems.- Residual Stresses and Stress Relieving in Uranium Alloys.- Residual Stresses in Resin Matrix Composites.- Residual Stress Measurement in Metal Matrix Composites.- Residual Stress Development in Ceramics.- Session VIII.- Determination of Residual Stress Distributions in the Interior of Technical Parts by Means of Neutron Diffraction.- Calculation of Quenching Stresses with and Without Transformation Effects.- X-Ray Measurements of Long-Range Strains: A Bridge Between Micromechanics and Macromechanics.- Stress Relaxation Characteristics and Data Utilization.

80 citations

Journal ArticleDOI
TL;DR: In this paper, the Boltzmann superposition principle was used to establish the transient creep and recovery behavior in compression of two lithium zinc silicate glassceramics over the temperature range 590 to 750° C at stresses up to 91.4 MN m−2.
Abstract: The creep and recovery behaviour in compression of two lithium zinc silicate glassceramics is established over the temperature range 590 to 750° C at stresses up to 91.4 MN m−2. It is shown that the transient creep obtained is linearly viscoelastic and obeys the Boltzmann superposition principle. The activation energy of the rate-controlling process is the same as that found for secondary creep and is due to viscous flow of the residual glass phase. A simple method of analysis of the strain-time curves is presented, which can be modified to apply to stress relaxation tests.

80 citations

Journal ArticleDOI
TL;DR: In this paper, a constitutive modelling deduced from a model proposed by Bouaziz and Guelton integrates this typical organisation of microtwins is integrated, and twinning is quantified by the partial volume fraction of twins in each system.
Abstract: The TEM study of our steel with a high manganese content reveals that mechanical twining (TWIP effect) occurs during the deformation at room temperature. Microtwins are organised into parallel stacks and two systems are sequentially activated in each grain. They participate to the deformation and they are strong obstacles for the dislocations and for other twins, leading to the decrease of the effective grain size. Thus, TWIP provides our alloy a very good ductility and a high hardening rate. Our constitutive modelling deduced from a model proposed by Bouaziz and Guelton [4] integrates this typical organisation of microtwins. Twinning is quantified in each grain by the partial volume fraction of twins in each system. A nucleation law for the microtwins is introduced which depends on the local stress and the stress relaxation due to pre-existing twins. The flow stress is deduced from the dislocation density, which evolves with the dynamical recovery and the decrease of the mean free path (MFP). The MFP takes into account the grain and twin boundaries and the forest dislocations. The strain is calculated by adding the contributions of dislocation glide and twinning accounting the orientation of the grain. To treat the polycristal, the behaviours of different grain orientations are mixed by assuming at each strain step that the increment of elastic energy stored is the same in each grain. The model was successfully applied to describe the mechanical properties of our alloy, for two different grain sizes. Some microstructural parameters are yet fitted. This leads to an insufficient prediction of the evolution of the microstructure. In further developments, we expect to introduce numerical simulation results on local characteristics of microtwins (thickness, critical resolved shear stress for twinning) and experimental results on the rate of twin nucleation.

80 citations

Journal ArticleDOI
TL;DR: In this paper, the integral-type creep law is converted to a rate-type form with internal variables, which account for the previous history and make it possible to take into account the evolution of various inelastic and nonlinear phenomena such as tensile cracking, cyclic creep and stress relaxation in prestressing tendons at variable strain.
Abstract: Recent compilation of data on numerous large-span prestressed segmentally erected box girder bridges revealed gross underestimation of their multi-decade deflections. The main cause has been identified as incorrect and obsolete creep prediction models in various existing standard recommendations and is being addressed in a separate study. However, previous analyses of the excessive deflections of the Koror-Babeldaob (KB) Bridge in Palau and of four Japanese bridges have shown that a more accurate method of multi-decade creep analysis is required. The objective of this paper is to provide a systematic and comprehensive presentation, appropriate not only for bridges but also for any large creep-sensitive structure. For each time step, the solution is reduced to an elastic structural analysis with generally orthotropic elastic moduli and eigenstrains. This analysis should normally be three-dimensional (3-D). It can be accomplished with a commercial finite element code such as ABAQUS. Based on the Kelvin chain model, the integral-type creep law is converted to a rate-type form with internal variables, which account for the previous history. For time steps short enough to render aging during each step to be negligible, a unique continuous retardation spectrum for each step is obtained by Laplace transform inversion using simple Widder's formula. Discretization of the spectrum then yields the current Kelvin chain moduli. The rate-type creep analysis is computationally more efficient than the classical integral-type analysis. More importantly, though, it makes it possible to take into account the evolution of various inelastic and nonlinear phenomena such as tensile cracking, cyclic creep, and stress relaxation in prestressing tendons at variable strain, as well as the effects of humidity and temperature variations, and the effect of wall thickness variation on drying creep and shrinkage. Finally, the advantages compared to the existing commercial programs, based on step-by-step integration of memory integrals, are pointed out and illustrated by a simple example.

80 citations


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