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Topic: Creep (deformation)

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In the News (Sat 21 Oct 17)

  Creep (deformation) - Wikipedia, the free encyclopedia
Creep is the term given to the material deformation that occurs as a result of long term exposure to levels of stress that are below the yield or ultimate strength, often in combination with temperatures near its melting point.
Creep is usually a concern to engineers and metallurgists when evaluating components that operate under high stresses and/or temperatures.
Creep deformation can be obtained in reasonable time frames under very high temperatures i.e., temperatures around half of the absolute melting temperature.
en.wikipedia.org /wiki/Creep_(failure_mode)   (973 words)

 Smart Manual on the Design and Testing of Bonded and Bolted Joints
Creep deformation usually occurs over a period of time when a material (or structure) is subjected to constant load (or stress) (i.e.
As creep is defined as time-dependent deformation of a material (or structure) under a constant load, the design process should involve substituting creep modulus for stiffness (or Young's modulus).
The creep index n is a measure of viscoelastic behaviour and is dependent on the resin type and degree of cure, interfacial bonding, fibre format, orientation of the fibres with respect to the applied load, fibre volume content, loading regime and environmental effects (i.e.
www.npl.co.uk /materials/programmes/mms11/design/bondfatigue4.html   (395 words)

 Tinius/Technical Support   (Site not responding. Last check: 2007-10-29)
Creep at room temperature is more common in plastic materials and is called cold flow or deformation under load.
Minimum creep rate is the slope of the portion of the creep vs time diagram corresponding to secondary creep.
Deformation is recorded at specified time intervals and a creep vs time diagram is plotted.
www.tiniusolsen.com /tmech2.html   (2116 words)

 Design for High-Temperature Applications: Part One   (Site not responding. Last check: 2007-10-29)
The issues of interest from a design basis are the nature of primary creep, the validity of the concept of viscous steady-state creep, and the dependence of deformation on both temperature and stress.
Creep of metals is primarily a result of the motion of dislocations, but is distinct from time-independent behavior in that flow continues as obstacles, which may be dislocation tangles or precipitate particles, are progressively overcome.
These various processes of creep (dislocation controlled as well as diffusion controlled) may be represented on a deformation mechanism map to highlight regimes of stress and temperature where each mechanism, based on current theories, may be operating.
www.key-to-steel.com /de/ViewArticle.asp?ID=133   (1377 words)

 The Numerical Analysis of Creep Deformation and Cavitation in TiAl Intermetallic Alloys
Creep deformation and cavitation damage in these microstructures were simulated and analyzed here using finite-element techniques.
It is evident from the present FE analyses that grain-boundary sliding significantly affects the course of creep deformation and cavitation damage in microstructures.
The effect of lamellae orientation on creep cavitation damage in the fully lamellar microstructures is found to be insignificant in the presence of grain-boundary sliding.
www.tms.org /pubs/journals/JOM/9808/Chakraborty/Chakraborty-9808.html   (2338 words)

 Creep - Wikipedia, the free encyclopedia
Creep (deformation), a materials deformation process that can lead to mechanical failure
Downhill creep, the slow progression of rock and other debris down a low grade slope
Creep (computer gaming), a neutral but hostile computer controlled unit in Warcraft III
en.wikipedia.org /wiki/Creep   (121 words)

 Tinius/TechnicalSupport   (Site not responding. Last check: 2007-10-29)
It is the stress at the point of tangency between the stress-strain curve and a line having a slope with respect to the stress axis 50% greater than the slope of the curve at the origin.
In the deformation under load test it indicates the extent to which a nonrigid plastic recovers from prolonged compressive deformation at elevated temperature.
It is equal to torsional deformation multiplied by the radius of the specimen.
www.tiniusolsen.com /tmech.html   (9481 words)

 The National Board of Boiler and Pressure Vessel Inspectors-Classic Series-Creep and Creep Failures
Creep may be defined as a time-dependent deformation at elevated temperature and constant stress.
This is followed by a region in which the elongation or deformation rate decreases with time, the so-called transient or primary creep, from region "A" to "B" of Figure 1.
Creep deformation and creep strength are a grain-size sensitive property.
www.nationalboard.org /NationalBoard/Articles/Classics/classic7.aspx   (1408 words)

 Journal of Electronic Materials: Creep Deformation of Sn-3.5Ag-xCu and Sn-3.5Ag-xBi Solder Joints
Creep properties of lead-free Sn-3.5Ag-based alloys with varying amounts of Cu or Bi were studied by single lap-shear test.
Creep results of lead-free solders have been reported, but the microstructure of bulk specimens differs from that of a solder joint.
Unlike the rupture appearance of the bulk specimen by necking,13 an abrupt tertiary creep region was found in the creep curve.
www.findarticles.com /p/articles/mi_qa3776/is_200502/ai_n11826106   (1318 words)

 Thursday Morning Sessions
During high temperature creep deformation, lattice dislocations interact with grain boundaries creating extrinsic grain boundary dislocations (EGBDs) which may then be dissociated, absorbed or trapped in the boundaries depending on the type and structure of the grain boundaries.
Thus the rate of formation and absorption of EGBDs during creep deformation is of practical importance since it may be related to the rate at which back-stresses on following dislocations are relaxed and this relaxation may control the rate of deformation.
The magnitude of primary creep scales with the interparticle spacing and it appears to be linked with the steady state creep mechanism.
www.tms.org /Meetings/Annual-96/ThursAM8.html   (1589 words)

 Numerical Model of Primary Creep Deformation in a Novel Double Shear Specimen
Three-dimensional finite element calculations were performed for primary creep deformation in a novel double shear specimen.
Two characteristic creep behaviors were considered: one in which the stress exponent, n, is equal to 3 and another in which n is equal to 5.
The uniformity of this quasi-stationary stress state throughout the gage section indicates that it may be used to characterize the overall stresses driving creep deformation and damage.
www.astm.org /JOURNALS/TESTEVAL/PAGES/17.htm   (183 words)

 [No title]   (Site not responding. Last check: 2007-10-29)
In this report, the creep deformation of Polycarbonate (PC) and Glass fiber reinforced polycarbonate (GFRPC) was researched to estimate the creep deformation on the molded materials.
The creep deformation on the phased stresses was calculated with superposition of the result of estimation on each stresses.
Therefore, the results of estimation of creep deformation were very fit to the experimental creep deformation.
www.sem.org /APP-CONF-AC-List2-Abstract.asp?PaperNo=142   (205 words)

 Luke Hsiung Bio   (Site not responding. Last check: 2007-10-29)
High-temperature deformation and creep, cyclic deformation and fatigue, high-temperature alloys and intermetallics, metal-matrix composites, thin-film and multilayered materials, high strain-rate deformation, phase transformations, dislocation dynamics, physical metallurgy of uranium alloys, electron microscopy and microanalysis.
L.M. Hsiung and T.G. Nieh, "The Evolution of Deformation Substructure in a Creep Deformed Fully-Lamellar TiAl Alloy,”; Mater.
L.M. Hsiung and T.G. Nieh, “Substructure in a Creep Deformed Lamellar TiAl Alloy,”; Scripta Mater., 36 (1997), 323.
www-cms.llnl.gov /bios/hsiung_lbio.html   (432 words)

 Geol 456/656 - Lithospheric Deformation   (Site not responding. Last check: 2007-10-29)
Strains are unitless and for rocks often expressed in terms of microstrain, which is a deformation of 0.000001 proportionately, or 0.0001%.
Internal gliding dislocation, as with plastic flow, is the main mechanism of deformation for power-law creep.
The load deforms the elastic lithosphere at strains much less than 1%, according to a fourth-order differential equation for plate flexing that surrounds the load with a moat and peripheral uplift.
www.seismo.unr.edu /ftp/pub/louie/class/plate/deformation.html   (1286 words)

 InSAR Analysis of Creep on the Hayward Fault   (Site not responding. Last check: 2007-10-29)
To date, methods of observing and measuring deformation on faults such as the Hayward Fault have relied on the use of cultural landmarks, trenches, official benchmarks, GPS measurements, bore hole and tilt meters, and creep meters.
InSAR observation of effects from creep across the Hayward Fault may eliminate errors inherent in interpolation of GPS data, thus creating better estimates of potential for seismic slip, which is useful for damage and hazard projection.
Creep is aseismic fault slip, that can either be steady or episodic, lasting minutes to days between co-seismic events.
www-mcnair.berkeley.edu /2000journal/Baroody/Baroody.html   (3928 words)

19.3: if the power-law creep equation used to construct this map is extrapolated to predict the behaviour of the pipes, it gives the strain-rates slower by a factor of 103 than those observed.
Deformation is dominated by elasticity and diffusional flow.
Reducing the stress by a factor of two would not remedy this.  An acceptable creep rate in the skirt could be obtained by selecting a steel with the same composition but a larger grain size: an increase to 200 µm, for instance, lowers the creep strain by a factor of 8.
engineering.dartmouth.edu /~defmech/Chapter_19.htm   (3624 words)

 Creep, deformation and moisture redistribution during air convective wood drying and conditioning
Creep, deformation and moisture redistribution during air convective wood drying and conditioning
This thesis contains an analysis of creep and deformation during wood drying related to stress development and susceptibility of checking.
The tension stress at the beginning of the drying period develops rapidly causing a creep response of the surface.
epubl.luth.se /avslutade/0348-8373/116   (455 words)

 mr51a in fm02
We conclude that the lack of LPO observed in the finest-grained regions of the mylonite indicates a transition from dislocation-accommodated grain boundary sliding to diffusion creep.
The deformation conditions determined from these analyses indicate that the rheology of gabbroic rocks is well bracketed by experimental flow laws for gabbroic rocks and suggest that there is not a large difference in the viscosity of lower oceanic crust and mantle.
Geologic observations of migmatite terrains suggest that deformation of orogenic crust is controlled by both horizontal flow, leading to layered migmatite, and vertical flow, reflecting the emplacement of gneiss domes cored by migmatite.
www.agu.org /cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm02&database=/data/epubs/wais/indexes/fm02/fm02&maxhits=200&="MR51A"   (4623 words)

For such designs at elevated temperatures the creep of engineering materials is the limiting factor with respect to the operating temperature.
Let us consider a creep experiment in which a specimen is subject to a constant stress of sufficient magnitude and a high enough temperature to cause creep deformation.
After primary creep a second stage occurs in which the creep rate is essentially constant and is therefore referred to as steady state creep.
www.eng.wayne.edu /MSE130/CREEP.html   (1248 words)

 [No title]   (Site not responding. Last check: 2007-10-29)
We have performed an experimental study to quantify the high-temperature creep behavior of natural diabase rocks under dry deformation conditions.
Samples of both Maryland diabase and Columbia diabase were investigated to measure the effects of temperature, oxygen fugacity, and plagioclase-to-pyroxene ratio on creep strength.
The dry creep strengths of both rocks are significantly greater than values previously measured on diabase under "as-received" or wet conditions [Shelton and Tullis, 1981; Caristan, 1982].
www.agu.org /pubs/abs/jb/97JB02671/tmp.html   (242 words)

 1.15.6 -integral evaluation
Because of the time-dependent effects of creep deformation, there is no one parameter that characterizes the stress state around the crack tip for all circumstances.
The appropriate parameter to use depends on the details of the constitutive law (whether the law describes primary, secondary, or tertiary creep) and on the stage of deformation of the material around the crack tip.
The creep response is then developed in a second step, using the *VISCO procedure.
www.rpi.edu /AFS/home/85/millem/public_html/v6.4/books/bmk/ch01s15ach110.html   (1435 words)

 Creep deformation
A major cause for concern is often time dependent deformation and failure (creep and creep rupture).
The state-of-the-art, high precision, constant stress creep laboratories are capable of testing materials in uniaxial tension from -60 to 1600°C both in air and vacuum.
Silicon carbide fibres in an alumina matrix after creep fracture at 1600°C in tension.
irc.swan.ac.uk /CreepDeformation.htm   (162 words)

 AAOS On-Line Service - 2005 Annual Meeting Poster Presentations Micromotion and Creep Deformation Assessment of Modular ...   (Site not responding. Last check: 2007-10-29)
The aim of this study was to investigate the extent of micromotion between the metal tibial baseplate and the UHMWPE insert of the Medial Rotation Knee system, and to measure creep deformation of the inferior surface of the insert.
Creep of the disassembled and competitive system retrieved components was measured after testing using a dial gauge.
No creep deformation was measured in the Medial Rotation Knee inserts, as opposed to values of 0.5 and 1.25mm for the competitor system inserts.
www.aaos.org /wordhtml/anmt2005/poster/p103.htm   (378 words)

 Creep Modeling in Excavation Analysis of a High Rock Slope   (Site not responding. Last check: 2007-10-29)
Based on the distinct element method, a numerical procedure is presented for simulation of creep behavior of jointed rock slopes due to excavation unloading.
As an application of the model, residual deformations of the high rock slopes of the Three Gorges shiplock due to excavation unloading and creep behavior are investigated.
It demonstrates the effectiveness of the presented model in analysis of the creep deformation due to excavation unloading of high rock slopes.
www.pubs.asce.org /WWWdisplay.cgi?0304044   (236 words)

 Jahrbuch-CD der MPG 2003 - Diffusional creep: Stresses and
In this article, we discuss creep deformation as it relates to thin films and multilayer foils.
We begin by reviewing experimental techniques for studying creep deformation In thin- film geometries, listing the pros and cons of each; then we discuss the use of deformation-mechanism maps for recording and understanding observed creep behavior.
We include a number of cautionary remarks regarding the impact of microstructural stability, zero-creep stresses, and transient-creep strains on stress-strain rate relationships, and we finish by reviewing the current state of knowledge for creep deformation in thin films.
www.mpg.de /forschungsergebnisse/wissVeroeffentlichungen/archivListenJahrbuch/2002/31/publZIM223.html   (139 words)

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