Showing papers on "Creep published in 1983"
TL;DR: The mechanical properties (elastic, plastic, creep, and fracture) of cellular solids or foams are related to the properties of the cell wall material and to the cell geometry.
Abstract: The mechanical properties (elastic, plastic, creep, and fracture) of cellular solids or foams are related to the properties of the cell wall material and to the cell geometry The properties are well described by simple formulae Such materials occur widely in nature and have many potential engineering applications
909 citations
TL;DR: In this paper, a comparison of alternative Creep Force Models for rail vehicle dynamic analysis is presented, and the results show that the alternative models are less accurate than the original models in terms of acceleration and acceleration.
Abstract: (1983). A Comparison of Alternative Creep Force Models for Rail Vehicle Dynamic Analysis. Vehicle System Dynamics: Vol. 12, No. 1-3, pp. 79-83.
459 citations
455 citations
442 citations
Book•
01 Jan 1983
TL;DR: The creep of plain and structural concrete as mentioned in this paper, a.k.a., the "deformation of concrete", is a metaphor for the "creep of plain concrete" and "decrease of structural concrete".
Abstract: Creep of plain and structural concrete , Creep of plain and structural concrete , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
418 citations
TL;DR: In this paper, the effect of two heat treatments on the creep behavior of CMSX-2, a recently developed nickel-base single-crystal turbine blade alloy, was investigated in the temperature range 760-1050 °C.
350 citations
263 citations
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TL;DR: A review of the fundamental flow properties and processes in experimentally deformed natural and synthetic halite single crystals and polycrystalline aggregates is presented in this article, where a representative steady-state flow law determined for natural aggregates and maximum natural deviatoric stresses deduced from subgrain sizes are applied briefly to considerations of creep in waste repositories and of salt dome dynamics.
250 citations
TL;DR: In this paper, the creep of porous KCl and of porous sucrose has been measured in the dry state, and saturated with aqueous solutions and with organic liquids, in a way which varies linearly with stress, and exponentially with temperature.
250 citations
TL;DR: In this article, the authors use a simple rheological model to investigate the behavior of the lithosphere undergoing extension, which is consistent with experimental data on rock creep and with the nature of the brittle/ductile transition.
Abstract: To investigate the behavior of the lithosphere undergoing extension, we use a simple rheological model broadly consistent with experimental data on rock creep and with the nature of the brittle/ductile transition. A plastic surface layer overlies a substrate that deforms by power law creep with a stress exponent n = 3 and an effective viscosity that decreases with depth. In extension this model shows a strong necking instability, provided that the thermal gradient is sufficiently large; otherwise, stable uniform extension is indicated. The predicted structures display uniformly spaced necks or regions of enhanced extension (basins) alternating with regions of reduced extension (ranges). If the depth to the brittle/ductile transition is roughly 10 km, as suggested by the maximum depth of seismic faulting, the model yields spacings for the incipient Basin and Range structures of about 25–60 km, in excellent agreement with observation.
210 citations
Book•
01 Jan 1983
TL;DR: In this paper, the effects of fire, ablation, heat flow in porous rock, thermal stress and dissolving coal are discussed, and alternative energy sources such as geothermal reservoirs and solar radiation are also discussed.
Abstract: Topics discussed in this book include modelling the effects of fire, ablation, heat flow in porous rock, thermal stress and dissolving coal. Alternative energy sources such as geothermal reservoirs and solar radiation are also discussed. Includes bibliographies at the end of the papers, a cited author index, and a subject index. Contents, abridged: Exact finite element solutions for linear steady state thermal problems. Steep gradient modelling in diffusion problems. Numerical solution of coupled conduction-convection problems using lumped-parameter methods. The prediction of turbulent heat transfer by the finite element methods. The influence of creep and transformation plasticity in the analysis of stresses due to heat treatment. Heat and moisture movement in wood composite materials during the pressing operation-a simplified model. Index.
TL;DR: In this paper, a model of cavity nucleation based on the stochastic nature of transgranular creep deformation is presented, and a quantitative assessment of the likely errors of measurement is presented.
TL;DR: In this paper, the effect of grain boundary structure on creep intergranular fracture on metal bicrystals and polycrystals is discussed on the basis of the effect on sliding, the contribution of sliding to the overall creep deformation and a sliding-fracture diagram.
Abstract: Importance of grain boundary sliding to creep intergranular fracture is focussed. Previous metallographic and fractographic studies of creep intergranular fracture on metal bicrystals and polycrystals are briefly reviewed in order to show the close relationship between grain boundary sliding and fracture. Deformation ledge and migration irregularity are shown to be potential sites of stress concentration and crack nucleation on sliding grain boundaries without particles. The effect of grain boundary structure on creep intergranular fracture is discussed on the basis of the effect of grain boundary structure on sliding, the contribution of sliding to the overall creep deformation, and a sliding-fracture diagram. Recent observations of the effect of grain boundary structure on creep intergranular fracture on alpha iron-tin alloy polycrystals are shown.
TL;DR: Using a time-dependent failure model, the creep-fracture data was found to be consistent with previous studies of the influence of strain rate on the monotonic tensile strength of bone, suggesting that creep damage plays an important role in O-T fatigue specimens.
Abstract: Fatigue tests of human cortical bone (up to 1.74 X 10(6) cycles) were conducted under tension-compression (T-C) and zero-tension (O-T) modes with a 2Hz, stress controlled, sinusoidal loading history. Tensile creep-fracture tests at constant stress levels were also performed. The relationship between the initial cyclic strain range and cycles to failure with the T-C specimens were consistent with that derived previously in low-cycle fatigue under strain control. Using a time-dependent failure model, the creep-fracture data was found to be consistent with previous studies of the influence of strain rate on the monotonic tensile strength of bone. The model also predicted quite well the time to failure for the O-T fatigue specimens, suggesting that creep damage plays an important role in O-T fatigue specimens.
TL;DR: In this article, a phenomenological constitutive law for the steady creep of polycrystalline materials undergoing creep-constrained grain boundary cavitation is proposed based on micro-mechanical considerations.
TL;DR: In this paper, it is shown that inelastic strain is a far more important parameter than time in determining the extent of acceleration of strain rate and that tertiary creep is produced by at least two competing strain-softening damage micromechanisms.
TL;DR: In this paper, the authors investigated the high-temperature rheological and electrical behavior of single-crystal KZnF 3 fluoperovskite, an analogue of the MgSiO 3 perovskites in the lower mantle.
TL;DR: A variety of microhardness, bulge, shear punch, indentation creep and load relaxation tests for obtaining strength, ductility, time-dependent flow, and fracture behavior information on specimens as small as TEM discs are under development at the University of California, Santa Barbara as discussed by the authors.
TL;DR: In this article, a model for premature intergranular fracture of metals in creep tests during He injection and after room temperature He implantation is critically assessed, and the differences in the stress and temperature dependences of the lifetimes observed in the two cases are attributed to differences in bubble nucleation and growth kinetics.
TL;DR: Athermal nucleation of microcracks and thermal nucleation during creep deformation are reviewed with an emphasis on effects of solute segregation to grain boundaries and cavity surfaces.
Abstract: Athermal nucleation of microcracks and thermal nucleation of cavities during creep deformation are reviewed with an emphasis on effects of solute segregation to grain boundaries and cavity surfaces. The magnitude and the duration of stress concentration at a triple grain junction or at a grain boundary inclusion are estimated for transient Coble creep and steady state power-law creep conditions. Stable configurations of wedge-type microcracks are predicted by a Griffith-like crack model. The rate for thermal nucleation of cavities is obtained by the Fokker-Planck equation for vacancy clusters. Cracks and cavities are interdependent, and cavity nucleation occurs continuously throughout the three creep stages. The local stress concentration enhances microcrack and cavity nucleation. The cavity nucleation rate is generally increased as a result of solute segregation to the surfaces and interfaces and/or gas precipitation into cavity volume. This enhanced nucleation is more effective in a system with mobile solutes than with immobile solutes. Immobile solute or trace elements may affect the nucleation rate also by changing the grain boundary diffusivity. Experimental techniques for quantitative analyses of cavity nucleation processes are discussed.
TL;DR: In this article, the influence of triaxial stressing on the growth of cavities on grain boundaries by the combined processes of plastic creep flow and grain boundary diffusion was investigated and a simple formula for the volumetric growth rate of the cavity was suggested and it was found to give a good approximation to the numerically computed results.
Journal Article•
TL;DR: In this article, a constitutive law for a bituminous mixture subjected to repeated loading is presented, where elastic, plastic, viscoelastic, and viscoplastic strain components are incorporated into the model as they are simultaneously present in the loading process.
Abstract: A constitutive law for a bituminous mixture subjected to repeated loading is presented. The elastic, plastic, viscoelastic, and viscoplastic strain components are incorporated into the model as they are simultaneously present in the loading process. The model parameters are extracted from a series of repeated uniaxial creep and creep recovery experiments conducted under constant compression stress. The experiments were performed at constant temperature for various stress levels, time periods, and numbers of cycles. The elastic strain is found to depend solely and linearly on the stress. The plastic strain is linearly proportional to stress and exhibits a power-law dependence on the number of loading cycles. The viscoelastic strain is nonlinear with respect to stress and is governed by a power law of time. The viscoplastic strain component is nonlinear with respect to stress and thus can be represented by the product of a second-order polynomial of stress and two power laws of time and number of cycles, respectively. The reliability of this constitutive equation was evaluated by means of two verification tests. Good agreement was found between the predicted and measured strains. (Author)
TL;DR: In this article, the recovery kinetics and friction stress associated with high temperature creep of the directionally solidified nickel-based superalloy IN738LC have been determined by using a numerical method of analysis to extrapolate data from stress drop experiments.
TL;DR: In this article, the authors provide an overview of the mechanisms of deformation and fracture in a number of alternative micromechanisms: deformation, fracture, and fracture.
Abstract: Publisher Summary This chapter provides an overview of mechanisms of deformation and fracture. Crystalline solids deform plastically by a number of alternative (and often competing) mechanisms: Low-temperature plasticity, twinning, power-law creep, diffusional flow, and so forth. Each has certain characteristics: A rate that depends strongly on temperature, for instance, or on grain size, or which is influenced by a dispersion of a second phase. These characteristics are summarized by the constitutive law for that mechanism and each has a characteristic regime of dominance, that is, a range of stresses, temperatures, and strain rates over which it is the primary mechanism. Fracture, too, can occur by any one of a number of alternative micromechanisms: Cleavage, ductile fracture, rupture intergranular creep fracture, and so forth. Each has certain characteristics: Negligible ductility, for instance, or a ductility that depends on inclusion density or grain size; and, for given stress states-simple tension, for example—each has a characteristic regime of dominance, that is, a range of stresses and temperatures over which it is the primary mechanism. This chapter describes the mechanisms of plasticity and fracture and develops ways of displaying their ranges of dominance and certain of their characteristics.
TL;DR: In this paper, the authors proposed the cyclic J-integral as a criterion for fatigue crack growth, which is evaluated as a generalized force on dislocations to be moved or the energy flow rate to be dissipated to heat by the dislocation movements in an element just attached to the fatigued crack tip during one cycle of loading.
Abstract: The definition of the cyclic J-integral is offered and its physical significance for fatigue crack growth is discussed using the Dugdale model on the assumption that the crack closure, cycle dependent creep deformation, and crack extension under cycling can be neglected. It is shown that the cyclic J-integral for small scale yielding is equivalent to theJ-integral for linear elastic crack independent of loading processes, while the value for large scale yielding varies with the loading processes. However, in both cases, the cyclicJ-integral remains constant during the reversal of loading under a constant stress range, if the first monotonic loading stage is excluded. In this situation, the cyclicJ-integral can be applied as a criterion for fatigue crack growth, since it is evaluated as a generalized force on dislocations to be moved or the energy flow rate to be dissipated to heat by the dislocation movements in an element just attached to the fatigued crack tip during one cycle of loading. It is suggested that the available experimental data of different materials for fatigue crack growth can be generalized to a unified formulation on the basis of the energy criterion. It is also deduced that the threshold ΔJ corresponding to ΔKth should be larger than 4γ where γ is the surface energy of the material. Finally the operational definition of the cyclicJ-integral on single loadversus displacement curves is given for center cracked plate with wide uncracked ligaments in tension.
TL;DR: In this article, a method of combining long term creep data with relatively short term mechanical behaviour to provide an estimate of creep-fatigue endurance is presented, based on a difference in strain rate around the cycle and the associated variation in ductility with strain rate.
Abstract: — A method of combining long term creep data with relatively short term mechanical behaviour to provide an estimate of creep-fatigue endurance is presented. It is proposed that the creep-fatigue effect in high temperature cyclic deformation is governed by a difference in strain rate around the cycle and the associated variation in ductility with strain rate.
TL;DR: The mechanisms for initiation of high temperature failure in liquid-phase sintered (L.P.S.) ceramics are investigated in this paper, where physical expressions are derived for the growth and coalescence times for oblate holes in thin-glass films along two-grain interfaces.
TL;DR: A brief review of the physical processes involved in creep cavitation can be found in this article, where the authors report on progress in this field and to stimulate further thought and research on these topics.
TL;DR: In this paper, a model of a Ni-Al-Mo-Ta superalloy with negative misfit dislocations is presented, and the length of the γ′ rafts increases linearly up to a maximum, which is reached well after the transition into second-stage creep.