Understanding creep—a review

Blum, W.; Eisenlohr, Philip; Breutinger, F.

doi:10.1007/s11661-002-0090-9

Cited by 145 publications

(67 citation statements)

References 34 publications

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“…The static load might induce some creep in the metal, but this phenomenon is well known and its magnitude reduces over time. 8 Thus, we consider a cantilever subject to a time dependent force F(t), with a characteristic frequency below the macroscopical resonance of the cantilever. In this case, the local microscopic stress varies over time following the external drive.…”

Section: B Up-conversion Noise Modelmentioning

confidence: 99%

“…8 Although the underlying micro-mechanics of mechanical up-conversion and creep may be related, creep has a event rate that decreases quickly after the initial stress, and experimental investigations have shown that the creep can be reduced with the use of maraging steel. 1,2,6,11 Our experiment however focuses on mechanical events that are continuously triggered by a time varying external perturbation, such as the Advanced LIGO suspension cantilevers which are subjected to by the local micro-seismic activity of the ground.…”

Section: Introductionmentioning

confidence: 99%

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An instrument to measure mechanical up-conversion phenomena in metals in the elastic regime

Vajente

Quintero

et al. 2016

Review of Scientific Instruments

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Physical aging of plastoferrites under tensile stress and its effect on microwave properties J. Appl. Phys. 104, 064108 (2008) Crystalline materials, such as metals, are known to exhibit deviation from a simple linear relation between strain and stress when the latter exceeds the yield stress. In addition, it has been shown that metals respond to varying external stress in a discontinuous way in this regime, exhibiting discrete releases of energy. This crackling noise has been extensively studied both experimentally and theoretically when the metals are operating in the plastic regime. In our study, we focus on the behavior of metals in the elastic regime, where the stresses are well below the yield stress. We describe an instrument that aims to characterize non-linear mechanical noise in metals when stressed in the elastic regime. In macroscopic systems, this phenomenon is expected to manifest as a non-stationary noise modulated by external disturbances applied to the material, a form of mechanical up-conversion of noise. The main motivation for this work is for the case of maraging steel components (cantilevers and wires) in the suspension systems of terrestrial gravitational wave detectors. Such instruments are planned to reach very ambitious displacement sensitivities, and therefore mechanical noise in the cantilevers could prove to be a limiting factor for the detectors' final sensitivities, mainly due to non-linear up-conversion of low frequency residual seismic motion to the frequencies of interest for the gravitational wave observations. We describe here the experimental setup, with a target sensitivity of 10 −15 m/ √Hz in the frequency range of 10-1000 Hz, a simple phenomenological model of the non-linear mechanical noise, and the analysis method that is inspired by this model. Published by AIP Publishing. [http://dx

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Section: B Up-conversion Noise Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An instrument to measure mechanical up-conversion phenomena in metals in the elastic regime

Vajente

Quintero

et al. 2016

Review of Scientific Instruments

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“…Treating recovery of dipoles under the assumption of spatially homogeneous glide on the active slip systems [4,13,14] leads to a rate ε & s of steady-state deformation as function of stress σ and temperature T which reproduces some of the experimentally observed features. This is…”

Section: Low-angle Boundariesmentioning

confidence: 52%

“…Therefore the density ρ dip of dislocation dipoles, i.e. the length of dislocations which is stored in dipolar configuration, needs to be considered as a structure parameter entering the expression for dislocation recovery by annihilation: [4,13].…”

Section: Low-angle Boundariesmentioning

confidence: 99%

Role of Boundaries in Control of Deformation Rate and Strength of Crystalline Materials

Blum

2008

MSF

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Abstract. Plastic deformation of crystalline materials is not controlled by interaction among free dislocations only, but the interaction of free dislocations with internal boundaries. i) Low-angle boundaries: Modeling of deformation of pure materials with conventional grain size on the basis of structure evolution indicates that low-angle boundaries act as obstacles of free dislocations. The migration of the low-angle boundaries constitutes an essential recovery process determining the deformation resistance in the steady state. ii) High-angle boundaries: Severe plastic deformation transforms low-angle boundaries into high-angle ones. They differ in obstacle and recovery characteristics from low-angle boundaries, which explains the special properties of ultrafine-grained and nanocrystalline materials with regard to strength, strain rate sensitivity and ductility. iii) Phase boundaries in Ni-base superalloys enhance the strengthening by hard phases with strengthening by dense dislocation networks serving to reduce coherency stresses. It is concluded that internal boundaries play a crucial role in controlling the evolution of structure and strength in crystalline materials.

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“…Studies of the effect of strain rate transients on the plastic behaviour of superplastic metals are scarce in the literature, 30,31) although the cases of hot working [32][33][34][35] and creep [36][37][38][39] conditions have been investigated more extensively. One common observation in the hot-working or creep studies is that conventional materials react to strain rate transients according to two typified behaviours: either ''pure metal'' or ''alloy'' type.…”

Section: Transient Strain Rate Effectsmentioning

confidence: 99%

Strain Rate Sensitivity of Superplastic Inconel 718

2005

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The strain rate sensitivity, m, of a superplastic-quality (SPF) INCONEL 718 alloy has been measured in the temperature and strain rate ranges of 925-1000 C and 10 À4 -10 À2 s À1 using both the classical method of instantaneous strain rate changes and a new method based on the continuous response to a sinusoidal strain rate input. The novel method furnishes continuous information from the whole stress-strain curve on the dependence of m on strain rate transients.In agreement with other recent studies, our results show that the maximum m values of the 718 alloy, although interesting enough for industrial superplastic forming, are lower than those shown by other superplastic materials for typical aeronautical application. A texture analysis indicates that crystallographic slip does not merely act here as an accommodation mechanism for grain boundary sliding. It significantly contributes to the total plastic strain, being thus responsible for the relatively low values observed for the strain rate sensitivity m.

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Understanding creep—a review

Cited by 145 publications

References 34 publications

An instrument to measure mechanical up-conversion phenomena in metals in the elastic regime

An instrument to measure mechanical up-conversion phenomena in metals in the elastic regime

Role of Boundaries in Control of Deformation Rate and Strength of Crystalline Materials

Strain Rate Sensitivity of Superplastic Inconel 718

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