The back stress concept in power law creep of metals: A review

Čadek, J.

doi:10.1016/0025-5416(87)90324-7

Cited by 57 publications

(44 citation statements)

References 38 publications

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“…However, since the apparent activation energy for the creep or rupture of heat-resistant steels for practical use is considerably large, the relation = does not hold. For this relation to hold even for practical heat-resistant steels, the concept of internal stress was introduced (Williams & Wilshire, 1973;Cadek, 1987), but this introduced new problems in that complicated work was necessary to measure the internal stresses and that the physical meanings of both the internal stress and stress exponent were not necessarily clear (Yoshinaga,1977).…”

Section: Introductionmentioning

confidence: 99%

Verification of Equation for Evaluating Dislocation Density during Steady-state Creep of Metals

Tamura¹

2017

JMSR

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Ninety-two sets of observed dislocation densities for crept specimens of 21 types of ferritic/martensitic and austenitic steels, Al, W, Mo, and Mg alloys, Cu, and Ti including germanium single crystals were collected to verify an equation for evaluating the dislocation density during steady-state creep proposed by Tamura and Abe (2015). The activation energy, , activation volume, , and Larson-Miller constant, , were calculated from the creep data. Using these parameter constants, the strain rate, and the temperature dependence of the shear modulus, a correction term, , was back-calculated from the observed dislocation density for each material. is defined in the present paper as a function of the temperature dependences of both the shear modulus and pre-exponential factor of the strain rate. The values of range from −394 to 233 kJmol and average 2.1 kJmol , which is a value considerably lower than the average value of (410.4 kJmol ), and values of are mainly within the range from 0 to 50 kJmol . The change in Gibbs free energy, ∆ , for creep deformation is obtained using the calculated value of , and the empirical relation ∆ ≅ ∆ is found, where ∆ is the change in Gibbs free energy for self-diffusion of the main componential element of each material. Experimental data confirm the validity of the evaluation equation for the dislocation density.

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Section: Introductionmentioning

confidence: 99%

Verification of Equation for Evaluating Dislocation Density during Steady-state Creep of Metals

Tamura¹

2017

JMSR

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“…In fact, Bhargava et al 95 observed that the presence of M 23 C 6 precipitates in a Type 304 stainless steel inhibited the formation of sub-grain dislocation structures. A value of n=5.6 is found based on the creep data of Fe-21Cr-37Ni stainless steel 30 , Figure 2 ( Creep in pure metals reveals that the presence of a dislocation sub-structure normally gives a creep stress exponent of n=5, whereas the presence of a three dimensional dislocation network in solid solution alloys gives a creep stress exponent of n=3.…”

Section: Creep Of a Complex Engineering Alloymentioning

confidence: 99%

“…The dislocation structure was characterised as a three dimensional dislocation network for all tests. The high values of creep stress exponents (n>5) seem to indicate a change in the mechanism for dislocation creep deformation, since the theoretical predictions of the creep stress exponent based on dislocation mechanisms are always less than five 18,30,65,66 . Creep data at temperatures from 625°C to 900°C are shown in Figure 2 , subgrain dislocation structures were obtained for stainless steels.…”

Section: Creep Of a Complex Engineering Alloymentioning

confidence: 99%

“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 There has been a widespread acceptance of the idea that creep deformation is not driven by the applied stress but rather by an operative stress. Sometimes this operative stress is seen as the difference between the applied stress and the so-called "internal stress", often considered to be representative of the material internal state 29,30 . Many different terms have been used to describe this internal stress concept, such as back stress 29 , friction stress 31,32 , threshold stress 33 and residual stress 34 .…”

Section: General Introductionmentioning

confidence: 99%

“…Many different terms have been used to describe this internal stress concept, such as back stress 29 , friction stress 31,32 , threshold stress 33 and residual stress 34 . By incorporating a certain value of "internal stress", attempts to reconcile differences between the theoretically derived creep stress exponents of the steady state creep rate and the experimental observations have been considered 30 .…”

Section: General Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A review of the changes of internal state related to high temperature creep of polycrystalline metals and alloys

Chen

Flewitt

Cocks

et al. 2014

International Materials Reviews

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When polycrystalline metals and their alloys are used at high temperature, creep deformation leads to changes in their internal state. The change in internal state manifests itself in many ways, but the two ways that concern us in this review are (i) the creation of internal stress arising from the strain incompatibility between grains and/or the formation of cell/sub-grain structures and (ii) a change in the material resistance. This review aims to provide a clear separation of these two concepts by exploring the origin of each term and how it is associated with the creep deformation mechanism. Experimental techniques used to measure the internal stress and internal resistance over different length-scales are critically reviewed. It is demonstrated that the interpretation of the measured values requires knowledge of the dominant creep deformation mechanism. Finally, the concluding comments provide a summary of the key messages delivered in this review and highlight the challenges that remain to be addressed.

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Dislocation creep of olivine: Backstress evolution controls transient creep at high temperatures

Hansen

Wallis

Breithaupt

et al. 2021

Preprint

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Transient creep occurs during geodynamic processes that impose stress changes on rocks at high temperatures. The transient is manifested as evolution in the viscosity of the rocks until steady-state flow is achieved. Although several phenomenological models of transient creep in rocks have been proposed, the dominant microphysical processes that control such behavior remain poorly constrained. To identify the intragranular processes that contribute to transient creep of olivine, we performed stress-reduction Preprint submitted to ESSOAr and Journal of Geophysical Research -Solid Earth 2 tests on single crystals of olivine at temperatures of 1250-1300°C. In these experiments, samples undergo time-dependent reverse strain after the stress reduction. The magnitude of reverse strain is ~10 -3 and increases with increasing magnitude of the stress reduction. High-angular resolution electron backscatter diffraction analyses of deformed material reveal lattice curvature and heterogeneous stresses associated with the dominant slip system. The mechanical and microstructural data are consistent with transient creep of the single crystals arising from accumulation and release of backstresses among dislocations. These results allow the dislocation-glide component of creep at high temperatures to be isolated, and we use these data to calibrate a flow law for olivine to describe the glide component of creep over a wide temperature range. We argue that this flow law can be used to estimate both transient creep and steadystate viscosities of olivine, with the transient evolution controlled by the evolution of the backstress. This model is able to predict variability in the style of transient (normal versus inverse) and the load-relaxation response observed in previous work.c Cooper et al. Hanson and Spetzler This study Normal Inverse

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The back stress concept in power law creep of metals: A review

Cited by 57 publications

References 38 publications

Verification of Equation for Evaluating Dislocation Density during Steady-state Creep of Metals

Verification of Equation for Evaluating Dislocation Density during Steady-state Creep of Metals

A review of the changes of internal state related to high temperature creep of polycrystalline metals and alloys

Dislocation creep of olivine: Backstress evolution controls transient creep at high temperatures

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