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Sample records for creep deformation characteristics

  1. Creep deformation characteristics of ductile discontinuous fiber reinforced composites

    SciTech Connect

    Biner, S.B.

    1993-10-01

    Role of material parameters and geometric parameters of ductile reinforcing phase on the creep deformation behavior of 20% discontinuously reinforced composite was numerically investigated including debonding and pull-out mechanisms. Results indicate that for rigidly bonded interfaces, the creep rate of the composite is not significantly influenced by the material properties and geometric parameters of the ductile reinforcing phase due to development of large hydrostatic stress and constrained deformation in the reinforcement. For debonding interfaces, the geometric parameters of the reinforcing phase are important; however, event with very weak interfacial behavior low composite creep rates can be achieved by suitable selection of the geometric parameters of the ductile reinforcing phase.

  2. Creep Deformation of Allvac 718Plus

    NASA Astrophysics Data System (ADS)

    Hayes, Robert W.; Unocic, Raymond R.; Nasrollahzadeh, Maryam

    2015-01-01

    The creep deformation behavior of Allvac 718Plus was studied over the temperature range of 923 K to 1005 K (650 °C to 732 °C) at initial applied stress levels ranging from 517 to 655 MPa. Over the entire experimental temperature-stress regime this alloy exhibits Class M-type creep behavior with all creep curves exhibiting a decelerating strain rate with strain or time throughout primary creep. However, unlike pure metals or simple solid solution alloys, this gamma prime strengthened superalloy does not exhibit steady-state creep. Rather, primary creep is instantly followed by a long duration of accelerating strain rate with strain or time. These creep characteristics are common among the gamma prime strengthened superalloys. Allvac 718Plus also exhibits a very high temperature dependence of creep rate. Detailed TEM examination of the deformation structures of selected creep samples reveals dislocation mechanisms similar to those found in high volume fraction gamma prime strengthened superalloys. Strong evidence of microtwinning is found in several of the deformation structures. The presence of microtwinning may account for the strong temperature dependence of creep rate observed in this alloy. In addition, due to the presence of Nb and thus, grain boundary delta phase, matrix dislocation activity which is not present in non-Nb-bearing superalloys occurs in this alloy. The creep characteristics and dislocation mechanisms are presented and discussed in detail.

  3. Creep Deformation of Allvac 718Plus

    DOE PAGESBeta

    Hayes, Robert W.; Unocic, Raymond R.; Nasrollahzadeh, Maryam

    2014-11-11

    The creep deformation behavior of Allvac 718Plus was studied over the temperature range 650° to 732°C at initial applied stress levels ranging from 517 to 655 MPa. Over the entire experimental temperature stress regime this alloy exhibits Class M type creep behavior with all creep curves exhibiting a decelerating strain rate with strain or time throughout primary creep. However, unlike pure metals or simple solid solution alloys this gamma prime strengthened superalloy does not exhibit steady state creep. Rather, primary creep is instantly followed by a long duration of accelerating strain rate with strain or time. These creep characteristics aremore » common amongst the gamma prime strengthened superalloys. Allvac 718Plus also exhibits a very high temperature dependence of creep rate. Detailed TEM examination of the deformation structures of selected creep samples reveals dislocation mechanisms similar to those found in high volume fraction gamma prime strengthened superalloys. Strong evidence of microtwinning is found in several of the deformation structures. The presence of microtwinning may account for the strong temperature dependence of creep rate observed in this alloy. In addition, due to the presence of Nb and thus, grain boundary delta phase, matrix dislocation activity which is not present in non Nb bearing superalloys occurs in this alloy. The creep characteristics and dislocation mechanisms are presented and discussed in detail.« less

  4. Creep Deformation of Allvac 718Plus

    SciTech Connect

    Hayes, Robert W.; Unocic, Raymond R.; Nasrollahzadeh, Maryam

    2014-11-11

    The creep deformation behavior of Allvac 718Plus was studied over the temperature range 650° to 732°C at initial applied stress levels ranging from 517 to 655 MPa. Over the entire experimental temperature stress regime this alloy exhibits Class M type creep behavior with all creep curves exhibiting a decelerating strain rate with strain or time throughout primary creep. However, unlike pure metals or simple solid solution alloys this gamma prime strengthened superalloy does not exhibit steady state creep. Rather, primary creep is instantly followed by a long duration of accelerating strain rate with strain or time. These creep characteristics are common amongst the gamma prime strengthened superalloys. Allvac 718Plus also exhibits a very high temperature dependence of creep rate. Detailed TEM examination of the deformation structures of selected creep samples reveals dislocation mechanisms similar to those found in high volume fraction gamma prime strengthened superalloys. Strong evidence of microtwinning is found in several of the deformation structures. The presence of microtwinning may account for the strong temperature dependence of creep rate observed in this alloy. In addition, due to the presence of Nb and thus, grain boundary delta phase, matrix dislocation activity which is not present in non Nb bearing superalloys occurs in this alloy. The creep characteristics and dislocation mechanisms are presented and discussed in detail.

  5. Creep Deformation of B2 Alumindes

    NASA Technical Reports Server (NTRS)

    Nathal, M. V.

    1991-01-01

    The creep resistance and elevated temperature deformation mechanisms in CoAl, FeAl, and NiAl are reviewed. The stress and temperature dependencies of the steady state creep rate, the primary creep behavior, the dislocation substructure, and the response during transient tests are used as the main indicators of the deformation processes. In single phase intermetallics, the influence of grain size, stoichiometry, and solid solution hardening have been examined. In addition, the effect of adding dispersoids, precipitates, and other types of reinforcements to improve creep strength are compared.

  6. Spatial fluctuations in transient creep deformation

    NASA Astrophysics Data System (ADS)

    Laurson, Lasse; Rosti, Jari; Koivisto, Juha; Miksic, Amandine; Alava, Mikko J.

    2011-07-01

    We study the spatial fluctuations of transient creep deformation of materials as a function of time, both by digital image correlation (DIC) measurements of paper samples and by numerical simulations of a crystal plasticity or discrete dislocation dynamics model. This model has a jamming or yielding phase transition, around which power law or Andrade creep is found. During primary creep, the relative strength of the strain rate fluctuations increases with time in both cases—the spatially averaged creep rate obeys the Andrade law epsilont ~ t - 0.7, while the time dependence of the spatial fluctuations of the local creep rates is given by Δepsilont ~ t - 0.5. A similar scaling for the fluctuations is found in the logarithmic creep regime that is typically observed for lower applied stresses. We review briefly some classical theories of Andrade creep from the point of view of such spatial fluctuations. We consider these phenomenological, time-dependent creep laws in terms of a description based on a non-equilibrium phase transition separating evolving and frozen states of the system when the externally applied load is varied. Such an interpretation is discussed further by the data collapse of the local deformations in the spirit of absorbing state/depinning phase transitions, as well as deformation-deformation correlations and the width of the cumulative strain distributions. The results are also compared with the order parameter fluctuations observed close to the depinning transition of the 2d linear interface model or the quenched Edwards-Wilkinson equation.

  7. Fluctuations and Scaling in Creep Deformation

    NASA Astrophysics Data System (ADS)

    Rosti, Jari; Koivisto, Juha; Laurson, Lasse; Alava, Mikko J.

    2010-09-01

    The spatial fluctuations of deformation are studied in the creep in Andrade’s power law and the logarithmic phases, using paper samples. Measurements by the digital image correlation technique show that the relative strength of the strain rate fluctuations increases with time, in both creep regimes. In the Andrade creep phase characterized by a power-law decay of the strain rate γt˜t-θ, with θ≈0.7, the fluctuations obey Δγt˜t-γ, with γ≈0.5. The local deformation follows a data collapse appropriate for a phase transition. Similar behavior is found in a crystal plasticity model, with a jamming or yielding transition.

  8. Finite Element Analysis of Plastic Deformation During Impression Creep

    NASA Astrophysics Data System (ADS)

    Naveena; Ganesh Kumar, J.; Mathew, M. D.

    2015-04-01

    Finite element (FE) analysis of plastic deformation associated with impression creep deformation of 316LN stainless steel was carried out. An axisymmetric FE model of 10 × 10 × 10 mm specimen with 1-mm-diameter rigid cylindrical flat punch was developed. FE simulation of impression creep deformation was performed by assuming elastic-plastic-power-law creep deformation behavior. Evolution of the stress with time under the punch during elastic, plastic, and creep processes was analyzed. The onset of plastic deformation was found to occur at a nominal stress about 1.12 times the yield stress of the material. The size of the developed plastic zone was predicted to be about three times the radius of the punch. The material flow behavior and the pile-up on specimen surface have been modeled.

  9. Creep deformation of a soft magnetic iron-cobalt alloy

    NASA Astrophysics Data System (ADS)

    Fingers, R. T.; Coate, J. E.; Dowling, N. E.

    1999-04-01

    The U.S. Air Force is in the process of developing magnetic bearings, as well as an aircraft integrated power unit and an internal starter/generator for main propulsion engines. These developments are the driving force for the new emphasis on the development of high saturation, low loss magnets capable of maintaining structural integrity in high stress and high temperature environments. It is this combination of desired material characteristics that is the motivation of this effort to measure, model, and predict the creep behavior of such advanced magnetic materials. Hiperco® Alloy 50HS, manufactured by Carpenter Technology Corporation, is one of the leading candidates for these applications. Material specimens were subjected to a battery of mechanical tests in order to study and characterize their behaviors. Tensile tests provided stress versus strain behaviors that clearly indicated: a yield point, a heterogeneous deformation described as Lüders elongation, the Portevin-LeChatelier effect at elevated temperatures, and most often a section of homogeneous deformation that concluded with necking and fracture. Creep testing indicated three distinct types of behavior. Two types resembled a traditional response with primary, secondary, and tertiary stages; while the third type can be characterized by an abrupt increase in strain rate that acts as a transition from one steady-state behavior to another. The relationships between the tensile and creep responses are discussed. Analyses of the mechanical behavior include double linear regression of empirically modeled data, and constant strain rate testing to bridge the tensile and creep test parameters.

  10. Tantalum alloys resist creep deformation at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Buckman, R. W., Jr.

    1966-01-01

    Dispersion-strengthened tantalum-base alloys possess high strength and good resistance to creep deformation at elevated temperatures in high vacuum environments. They also have ease of fabrication, good weldability, and corrosion resistance to molten alkali metals.

  11. Mapping microscale strain heterogeneity during creep deformation

    NASA Astrophysics Data System (ADS)

    Quintanilla Terminel, A.; Evans, J.

    2013-12-01

    We use a new technique combining microfabrication technology and compression tests to map the strain field at a micrometric scale in polycrystalline materials. This technique allows us to map local strain while measuring macroscopic strain and rheological properties, and provides insight into the relative contribution of various plasticity mechanisms under varying creep conditions. The micro-strain mapping technique was applied to Carrara Marble under different deformation regimes, at 300 MPa and temperatures ranging from 200 to 700 °C. At 600 °C, strain of 10%, and strain rate of 3e-5s-1, the local strain at twin and grain boundaries is up to 5 times greater than the average sample strain. At these conditions, strains averaged across a particular grain may vary by as much as 100%, but the strain field becomes more homogeneous with increasing strain. For example, for the analyzed experiments, the average wavelength of the strain heterogeneity is 70 micrometers at 10% strain, but increases to 110 micrometers at 20%. For a strain of 10%, heterogeneity is increased at slower strain rate (at 1e-5s-1). This increase seems to be associated with a more important role of twin boundary and grain boundary migration. As expected, twin densities are markedly greater at the lower temperature, though it is still unclear whether the relative twin volume is greater. However, twin strains are still important at 600 °C and accommodate an average of 14 % of the total strain at 10% deformation and a strain rate of 3e-5s-1.

  12. Effect of Tungsten on Primary Creep Deformation and Minimum Creep Rate of Reduced Activation Ferritic-Martensitic Steel

    NASA Astrophysics Data System (ADS)

    Vanaja, J.; Laha, Kinkar; Mathew, M. D.

    2014-10-01

    Effect of tungsten on transient creep deformation and minimum creep rate of reduced activation ferritic-martensitic (RAFM) steel has been assessed. Tungsten content in the 9Cr-RAFM steel has been varied between 1 and 2 wt pct, and creep tests were carried out over the stress range of 180 and 260 MPa at 823 K (550 °C). The tempered martensitic steel exhibited primary creep followed by tertiary stage of creep deformation with a minimum in creep deformation rate. The primary creep behavior has been assessed based on the Garofalo relationship, , considering minimum creep rate instead of steady-state creep rate . The relationships between (i) rate of exhaustion of transient creep r' with minimum creep rate, (ii) rate of exhaustion of transient creep r' with time to reach minimum creep rate, and (iii) initial creep rate with minimum creep rate revealed that the first-order reaction-rate theory has prevailed throughout the transient region of the RAFM steel having different tungsten contents. The rate of exhaustion of transient creep r' and minimum creep rate decreased, whereas the transient strain ɛ T increased with increase in tungsten content. A master transient creep curve of the steels has been developed considering the variation of with . The effect of tungsten on the variation of minimum creep rate with applied stress has been rationalized by invoking the back-stress concept.

  13. Creep deformation mechanisms in modified 9Cr-1Mo steel

    NASA Astrophysics Data System (ADS)

    Shrestha, Triratna; Basirat, Mehdi; Charit, Indrajit; Potirniche, Gabriel P.; Rink, Karl K.; Sahaym, Uttara

    2012-04-01

    Modified 9Cr-1Mo (Grade 91) steel is currently considered as a candidate material for reactor pressure vessels (RPVs) and reactor internals for the Very High Temperature Reactor (VHTR). The tensile creep behavior of modified 9Cr-1Mo steel (Grade 91) was studied in the temperature range of 873-1023 K and stresses between 35 MPa and 350 MPa. Analysis of creep results yielded stress exponents of ∼9-11 in the higher stress regime and ∼1 in the lower stress regime. The high stress exponent in the power-law creep regime was rationalized by invoking the concept of threshold stress, which represents the lattice diffusion controlled dislocation climb process. Without threshold stress compensation, the activation energy was 510 ± 51 kJ/mol, while after correcting for the threshold stress, the activation energy decreased to 225 ± 24 kJ/mol. This value is close to the activation energy for lattice self-diffusion in α-Fe. Threshold stress calculations were performed for the high stress regime at all test temperatures. The calculated threshold stress showed a strong dependence on temperature. The creep behavior of Grade 91 steel was described by the modified Bird-Mukherjee-Dorn relation. The rate controlling creep deformation mechanism in the high stress regime was identified as the edge dislocation climb with a stress exponent of n = 5. On the other hand, the deformation mechanism in the Newtonian viscous creep regime (n = 1) was identified as the Nabarro-Herring creep.

  14. Creep Behavior, Deformation Mechanisms, and Creep Life of Mod.9Cr-1Mo Steel

    NASA Astrophysics Data System (ADS)

    ABE, Fujio

    2015-12-01

    The creep behavior, deformation mechanisms, and the correlation between creep deformation parameters and creep life have been investigated for Mod.9Cr-1Mo steel (Gr.91, 9Cr-1Mo-VNb) by analyzing creep strain data at 723 K to 998 K (450 °C to 725 °C), 40 to 450 MPa, and t r = 11.4 to 68,755 hours in NIMS Creep Data Sheet. The time to rupture t r is reasonably correlated with the minimum creep rate {dot{\\varepsilon }}_{ min } and the acceleration of creep rate by strain in the acceleration region dln {dot{\\varepsilon }} /d ɛ, as t r = 1.5/[ {dot{\\varepsilon }}_{ min } ( dln {dot{\\varepsilon }} /d ɛ)], where {dot{\\varepsilon }}_{ min } and dln {dot{\\varepsilon }} /d ɛ reflect the creep behavior in the transient and acceleration regions, respectively. The {dot{\\varepsilon }}_{ min } is inversely proportional to the time to minimum creep rate t m, while it is proportional to the strain to minimum creep rate ɛ m, as {dot{\\varepsilon }}_{ min } = 0.54 ( ɛ m/ t m). The ɛ m decreases with decreasing stress, suggesting that the creep deformation in the transient region becomes localized in the vicinity of prior austenite grain boundaries with decreasing stress. The duration of acceleration region is proportional to the duration of transient region, while the dln {dot{\\varepsilon }} /d ɛ is inversely proportional to the ɛ m. The t r is also correlated with the t m, as t r = g t m, where g is a constant. The present creep life equations reasonably predict the degradation in creep rupture strength at long times. The downward deviation takes place in the t r vs {dot{\\varepsilon }}_{ min } curves (Monkman-Grant plot). At the same {dot{\\varepsilon }}_{ min } , both the ɛ m and t m change upon the condition of t m ∝ ɛ m. The decrease in ɛ m with decreasing stress, corresponding to decreasing {dot{\\varepsilon }}_{ min } , causes a decrease in t m, indicating the downward deviation of the t r vs {dot{\\varepsilon }}_{ min } curves.

  15. Vertebroplasty reduces progressive ׳creep' deformity of fractured vertebrae.

    PubMed

    Luo, J; Pollintine, P; Annesley-Williams, D J; Dolan, P; Adams, M A

    2016-04-11

    Elderly vertebrae frequently develop an "anterior wedge" deformity as a result of fracture and creep mechanisms. Injecting cement into a damaged vertebral body (vertebroplasty) is known to help restore its shape and stiffness. We now hypothesise that vertebroplasty is also effective in reducing subsequent creep deformations. Twenty-eight spine specimens, comprising three complete vertebrae and the intervening discs, were obtained from cadavers aged 67-92 years. Each specimen was subjected to increasingly-severe compressive loading until one of its vertebrae was fractured, and the damaged vertebral body was then treated by vertebroplasty. Before and after fracture, and again after vertebroplasty, each specimen was subjected to a static compressive force of 1kN for 1h while elastic and creep deformations were measured in the anterior, middle and posterior regions of each adjacent vertebral body cortex, using a 2D MacReflex optical tracking system. After fracture, creep in the anterior and central regions of the vertebral body cortex increased from an average 4513 and 885 microstrains, respectively, to 54,107 and 34,378 microstrains (both increases: P<0.001). Elastic strains increased by a comparable amount. Vertebroplasty reduced creep in the anterior and central cortex by 61% (P=0.006) and 66% (P=0.017) respectively. Elastic strains were reduced by less than half this amount. Results suggest that the beneficial effects of vertebroplasty on the vertebral body continue long after the post-operative radiographs. Injected cement not only helps to restore vertebral shape and elastic properties, but also reduces subsequent creep deformation of the damaged vertebra. PMID:26459490

  16. Fatigue and creep-fatigue deformation of several nickel-base superalloys at 650 C

    NASA Technical Reports Server (NTRS)

    Miner, R. V.; Gayda, J.; Maier, R. D.

    1982-01-01

    Transmission electron microscopy has been used to study the bulk deformation characteristics of seven nickel-base superalloys tested in fatigue and creep-fatigue at 650 C. The alloys were Waspalloy, HIP Astroloy, H plus F Astroloy, H plus F Rene 95, IN 100, MERL 76, and NASA IIB-7. The amount of bulk deformation observed in all the alloys was low. In tests with inelastic strain amplitudes less than about 0.003, only some grains exhibited yielding and the majority of those had the 110 line near the tensile axis. Deformation occurred on octahedral systems for all of the alloys except MERL 76 which also showed abundant primary cube slip. Creep-fatigue cycling occasionally produced extended faults between partial dislocations, but otherwise deformation was much the same as for fatigue cycling.

  17. A True-Stress Creep Model Based on Deformation Mechanisms for Polycrystalline Materials

    NASA Astrophysics Data System (ADS)

    Wu, Xijia; Williams, Steve; Gong, Diguang

    2012-11-01

    A true-stress creep model has been developed based on well-recognized deformation mechanisms, i.e., dislocation glide, dislocation climb, and grain boundary sliding. The model provides a physics-based description of the entire creep deformation process with regards to the strain-time history (primary, secondary, and tertiary creep), rupture strain and lifetime, which finds good agreement with experimental observations for Waspaloy. A deformation-mechanism map is constructed for Waspaloy, and a creep failure criterion is defined by the dominant deformation mechanisms leading to intergranular/transgranular fracture. Thus, the model is a self-consistent tool for creep life prediction.

  18. Assessment of Tungsten Content on Tertiary Creep Deformation Behavior of Reduced Activation Ferritic-Martensitic Steel

    NASA Astrophysics Data System (ADS)

    Vanaja, J.; Laha, Kinkar

    2015-10-01

    Tertiary creep deformation behavior of reduced activation ferritic-martensitic (RAFM) steels having different tungsten contents has been assessed. Creep tests were carried out at 823 K (550 °C) over a stress range of 180 to 260 MPa on three heats of the RAFM steel (9Cr-W-0.06Ta-0.22V) with tungsten content of 1, 1.4, and 2.0 wt pct. With creep exposure, the steels exhibited minimum in creep rate followed by progressive increase in creep rate until fracture. The minimum creep rate decreased, rupture life increased, and the onset of tertiary stage of creep deformation delayed with the increase in tungsten content. The tertiary creep behavior has been assessed based on the relationship, , considering minimum creep rate () instead of steady-state creep rate. The increase in tungsten content was found to decrease the rate of acceleration of tertiary parameter ` p.' The relationships between (1) tertiary parameter `p' with minimum creep rate and time spent in tertiary creep deformation and (2) the final creep rate with minimum creep rate revealed that the same first-order reaction rate theory prevailed in the minimum creep rate as well as throughout the tertiary creep deformation behavior of the steel. A master tertiary creep curve of the steels has been developed. Scanning electron microscopic investigation revealed enhanced coarsening resistance of carbides in the steel on creep exposure with increase in tungsten content. The decrease in tertiary parameter ` p' with tungsten content with the consequent decrease in minimum creep rate and increase in rupture life has been attributed to the enhanced microstructural stability of the steel.

  19. Motion of a Deformed Sphere with Slip in Creeping Flows

    NASA Astrophysics Data System (ADS)

    Benard, Andre; Jia, Liping; Petty, Charles

    2004-11-01

    An analytical solution for the motion of a slightly deformed sphere in creeping flows with the assumption of slip on the particle surface is presented. Explicit expressions are obtained for the hydrodynamic force and torque exerted by the fluid on the deformed sphere. A perturbation method, based on previous work done by Brenner [1964] and Lamb[1945], is used to solve for the motion of a fluid influenced by the presence of a deformed sphere. Slip is assumed at the surface of the particle. Hydrodynamic force and torque exerted by the fluid on the deformed sphere are expressed explicitly for a translational and rotational deformed sphere. The equation governing the motion and orientation of a spheroid induced by homogenous flows is also presented. This evolution equation for the orientation of the spheroid is similar to the equation derived by Jeffery [1922]. Solutions of this equation show that the period of rotation of the particle with slip is longer than for the same particle without slip. Furthermore, when the slip coefficient is sufficiently low, the particle rotates to a fixed angle that corresponds to a quasi-steady state in the flow. REFERENCES Brenner, H. 1964 The Stokes resistance of a slightly deformed sphere. Chemical Engineering Science 19, 519-539 Jeffery, G.B.1922 The motion of ellipsoidal particles immersed in a viscous fluid. Proc. Soc. Lond. Math., 102, 161-179 Lamb, H. 1945 Hydrodynamics, sixth version, Dover, New York, U.S.A

  20. Microstructural behavior of 8Cr-ODS martensitic steels during creep deformation

    NASA Astrophysics Data System (ADS)

    Shinozuka, K.; Esaka, H.; Tamura, M.; Tanigawa, H.

    2011-10-01

    Oxide dispersion strengthened (ODS) steels show a high anisotropy in their creep behavior because of the δ-ferrite grain elongated in the hot-rolled direction and the characteristic formation of creep cavities. In this work, the relationship between the δ-ferrite grain and the growth of creep cavities in 8Cr-ODS steels was investigated. The samples of two ODS steels with different δ-ferrite volume fractions were machined parallel and perpendicular to the hot-rolled direction. Creep rupture tests and interrupted tests were performed at 700 °C and about 197 MPa. Cavities formed in the martensite along δ-ferrite grains during creep deformation. The area fraction of the cavities of all specimens increased in proportion to the cube root of test time. When the volume fraction of δ-ferrite was high and δ-ferrite grains elongated parallel to the load direction, δ-ferrite then obstructed the propagation of cracks. However, when the volume fraction of δ-ferrite was low and δ-ferrite grains elongated perpendicular to the load direction, δ-ferrite grains had little effect on crack propagation.

  1. Deformation Microstructures and Creep Mechanisms in Advanced ZR-Based Cladding Under Biazal Loading

    SciTech Connect

    K. Linga Murty

    2008-08-11

    Investigate creep behavior of Zr-based cladding tubes with attention to basic creep mechanisms and transitions in them at low stresses and/or temperatures and study the dislocation microstructures of deformed samples for correlation with the underlying micromechanism of creep

  2. Creep deformation of an unirradiated zircaloy nuclear fuel cladding tube under dry storage conditions

    NASA Astrophysics Data System (ADS)

    Mayuzumi, Masami; Onchi, Takeo

    1990-05-01

    Measurements of creep deformation were made on an internally gas pressurized tubular Zircaloy-4 specimen with plugs welded to its ends. Creep tests were conducted at temperatures between 577 and 693 K for holding times of up to 26640 ks, to formulate the creep equation needed for predicting creep strain during dry storage of spent fuel. Discussion was also given to the difference of creep behaviour between irradiated and unirradiated fuel cladding, indicating that the equation derived is applicable for predicting creep strain of spent fuel cladding during dry storage.

  3. Analyses of Transient and Tertiary Small Punch Creep Deformation of 316LN Stainless Steel

    NASA Astrophysics Data System (ADS)

    Ganesh Kumar, J.; Ganesan, V.; Laha, K.

    2016-09-01

    Creep deformation behavior of 316LN stainless steel (SS) under small punch creep (SPC) and uniaxial creep test has been assessed and compared at 923 K (650 °C). The transient and tertiary creep deformation behaviors have been analyzed according to the equation proposed for SPC deflection, δ = δ0 + δ_{{T}} \\cdot (1 - {{e}}^{ - κ \\cdot t} ) + dot{δ }_{{s}} t + δ3 {{e}}^{{[ {φ ( {t - t_{{r}} } )} ]}} on the basis of Dobes and Cadek equation for uniaxial creep strain. Trends in the variations of (i) rate of exhaustion of transient creep ( κ) with steady-state deflection rate ( dot{δ }_{{s}} ) (ii) ` κ' with time to attain steady-state deflection rate, and (iii) initial creep deflection rate with steady-state deflection rate implied that transient SPC deformation obeyed first-order reaction rate theory. The rate of exhaustion of transient creep ( r') values that were determined from uniaxial creep tests were correlated with those obtained from SPC tests. Master curves representing transient creep deformation in both SPC and uniaxial creep tests have been derived and their near coincidence brings unique equivalence between both the test techniques. The relationships between (i) rate of acceleration of tertiary creep ( φ) and steady-state deflection rate, (ii) ` φ' and time spent in tertiary stage, and (iii) final creep deflection rate and steady-state deflection rate revealed that first-order reaction rate theory governed SPC deformation throughout the tertiary region also. Interrelationship between the transient, secondary, and tertiary creep parameters indicated that the same mechanism prevailed throughout the SPC deformation.

  4. Analyses of Transient and Tertiary Small Punch Creep Deformation of 316LN Stainless Steel

    NASA Astrophysics Data System (ADS)

    Ganesh Kumar, J.; Ganesan, V.; Laha, K.

    2016-07-01

    Creep deformation behavior of 316LN stainless steel (SS) under small punch creep (SPC) and uniaxial creep test has been assessed and compared at 923 K (650 °C). The transient and tertiary creep deformation behaviors have been analyzed according to the equation proposed for SPC deflection, δ = δ0 + δ_{T} \\cdot (1 - {e}^{ - κ \\cdot t} ) + dot{δ }_{s} t + δ3 {e}^{{[ {φ ( {t - t_{r} } )} ]}} on the basis of Dobes and Cadek equation for uniaxial creep strain. Trends in the variations of (i) rate of exhaustion of transient creep (κ) with steady-state deflection rate ( dot{δ }_{s} ) (ii) `κ' with time to attain steady-state deflection rate, and (iii) initial creep deflection rate with steady-state deflection rate implied that transient SPC deformation obeyed first-order reaction rate theory. The rate of exhaustion of transient creep (r') values that were determined from uniaxial creep tests were correlated with those obtained from SPC tests. Master curves representing transient creep deformation in both SPC and uniaxial creep tests have been derived and their near coincidence brings unique equivalence between both the test techniques. The relationships between (i) rate of acceleration of tertiary creep (φ) and steady-state deflection rate, (ii) `φ' and time spent in tertiary stage, and (iii) final creep deflection rate and steady-state deflection rate revealed that first-order reaction rate theory governed SPC deformation throughout the tertiary region also. Interrelationship between the transient, secondary, and tertiary creep parameters indicated that the same mechanism prevailed throughout the SPC deformation.

  5. Multimechanism-Deformation Parameters of Domal Salts Using Transient Creep Analysis

    SciTech Connect

    MUNSON, DARRELL E

    1999-09-01

    Use of Gulf Coast salt domes for construction of very large storage caverns by solution mining has grown significantly in the last several decades. In fact, among the largest developers of storage caverns along the Gulf Coast is the Strategic Petroleum Reserve (SPR) which has purchased or constructed 62 crude oil storage caverns in four storage sites (domes). Although SPR and commercial caverns have been operated economically for many years, the caverns still exhibit some relatively poorly understood behaviors, especially involving creep closure volume loss and hanging string damage from salt falls. Since it is possible to postulate that some of these behaviors stem from geomechanical or reformational aspects of the salt, a method of correlating the cavern response to mechanical creep behavior as determined in the laboratory could be of considerable value. Recently, detailed study of the creep response of domal salts has cast some insight into the influence of different salt origins on cavern behavior. The study used a simple graphical analysis of limited non-steady state data to establish an approach or bound to steady state, as an estimate of the steady state behavior of a given salt. This permitted analysis of sparse creep databases for domal salts. It appears that a shortcoming of this steady state analysis method is that it obscures some critical differences of the salt material behavior. In an attempt to overcome the steady state analysis shortcomings, a method was developed based on integration of the Multimechanism-Deformation (M-D) creep constitutive model to obtain fits to the transient response. This integration process permits definition of all the material sensitive parameters of the model, while those parameters that are constants or material insensitive parameters are fixed independently. The transient analysis method has proven more sensitive to differences in the creep characteristics and has provided a way of defining different behaviors within a

  6. Creep deformation behavior in eutectic Sn-Ag solder joints using a novel mapping technique

    SciTech Connect

    Lucas, J.P.; Guo, F.; McDougall, J.; Bieler, T.R.; Subramanian, K.N.; Park, J.K.

    1999-11-01

    Creep deformation behavior was measured for 60--100 {micro}m thick solder joints. The solder joints investigated consisted of: (1) non-composite solder joints made with eutectic Sn-Ag solder, and (2) composite solder joints with eutectic Sn-Ag solder containing 20 vol.%, 5 {micro}m diameter in-situ Cu{sub 6}Sn{sub 5} intermetallic reinforcements. All creep testing in this study was carried out at room temperature. Qualitative and quantitative assessment of creep deformation was characterized on the solder joints. Creep deformation was analyzed using a novel mapping technique where a geometrical-regular line pattern was etched over the entire solder joint using excimer laser ablation. During creep, the laser-ablation (LA) pattern becomes distorted due to deformation in the solder joint. By imaging the distortion of laser-ablation patterns using the SEM, actual deformation mapping for the entire solder joint is revealed. The technique involves sequential optical/digital imaging of the deformation versus time history during creep. By tracing and recording the deformation of the LA patterns on the solder over intervals of time, local creep data are obtained in many locations in the joint. This analysis enables global and localized creep shear strains and strain rate to be determined.

  7. Experimental investigation of creep crack tip deformation using moire interferometry

    NASA Astrophysics Data System (ADS)

    Kang, B. S.-J.; Zhuang, Y.-N.

    High temperature moire interferometry was applied to obtain full-field creep crack tip displacements of a three-point bend Al 2024-T4 specimen under constant temperature of 200 C up to 720 hr. C* was evaluated by the moire data obtained at discrete time intervals. Test results indicated that under steady-state creep condition, the creep crack tip v-displacement rate agreed with the asymptotic solution based on C*-integral, however, no creeping behavior was observed for the crack tip u-displacement field after t = 276 hr. This discrepancy may be due to the initial large creep crack tip blunting and cavitation damage which alter the creep crack tip singular field such that the C*-integral is no longer applicable to characterize steady-state creep crack tip field. It is suggested that the size and shape of material grain boundaries may play an important role on the creeping behavior of the material.

  8. Features controlling the early stages of creep deformation of Waspaloy

    NASA Technical Reports Server (NTRS)

    Ferrari, A.; Wilson, D. J.

    1974-01-01

    A model has been presented for describing primary and second stage creep. General equations were derived for the amount and time of primary creep. It was shown how the model can be used to extrapolate creep data. Applicability of the model was demonstrated for Waspaloy with gamma prime particle sizes from 75 - 1000 A creep tested in the temperature range 1000 - 1400 F (538 - 760 C). Equations were developed showing the dependence of creep parameters on dislocation mechanism, gamma prime volume fraction and size.

  9. A TEM Study of Creep Deformation Mechanisms in Allvac 718Plus

    SciTech Connect

    Unocic, Raymond R; Unocic, Kinga A; Hayes, Robert; Daehn, Glenn; Mills, Michael J.

    2010-01-01

    A preliminary study on the evolution of creep deformation substructure in Ni-base superalloy Allvac 718Plus has been performed. Specimens crept at 620 MPa and at temperatures ranging from 690-732 C were examined utilizing diffraction contrast TEM characterization techniques. Creep was interrupted at 1-2.5% strain in order to study the deformation substructure following a limited amount of deformation. The dominant deformation modes at each of the test temperatures were highly planar in nature and involved shearing of the matrix and precipitates on {111} glide planes. In addition, paired a/2<110> dislocations were evident which suggest an antiphase boundary shearing mechanism. Creep induced microtwinning was also observed at the highest creep temperature which was created by identical a/6<112> Shockley partial dislocations that shear the matrix and precipitates on consecutive close packed {111} glide planes.

  10. Experimental Research on Creep Characteristics of Nansha Soft Soil

    PubMed Central

    Luo, Qingzi; Chen, Xiaoping

    2014-01-01

    A series of tests were performed to investigate the creep characteristics of soil in interactive marine and terrestrial deposit of Pearl River Delta. The secondary consolidation test results show that the influence of consolidation pressure on coefficient of secondary consolidation is conditional, which is decided by the consolidation state. The ratio of coefficient of secondary consolidation and coefficient of compressibility Ca/Cc is almost a constant, and the value is 0.03. In the shear-box test, the direct sheer creep failure of soil is mainly controlled by shear stress rather than the accumulation of shear strain. The triaxial creep features are closely associated with the drainage conditions, and consolidation can weaken the effect of creep. When the soft soil has triaxial creep damage, the strain rate will increase sharply. PMID:24526925

  11. On the creep deformation mechanisms of an advanced disk nickel-base superalloy

    NASA Astrophysics Data System (ADS)

    Unocic, Raymond R.

    The main objective of this research was aimed at investigating the fundamental relationship between microstructure and creep deformation mechanisms using a variety of electron microscopy characterization techniques. The alloy used in this research, Rene 104, is a newer generation powder metallurgy Ni-base superalloy that was developed specifically for aircraft gas turbine disk applications with extended service durability at temperatures exceeding 650°C. The influence of stress and temperature was studied first and it was found that during creep deformation at temperatures between 677--815°C and stresses between 345--724MPa a variety of distinctly different creep deformation mechanisms were operative. In addition to identifying the creep deformation mechanisms an attempt was made to determine the creep rate limiting process so that an improved understanding of the fundamental processes that control deformation can be better understood. Microtwinning was found to the dominant deformation mechanism following creep at 677°C/690MPa and 704°C/724MPa. Microtwins form by the motion of paired a/6<112> Shockley partial dislocations that shear both the gamma matrix and gamma' precipitates. The rate limiting process in this mechanism is diffusion mediated atomic reordering that occurs in the wake of the shearing, twinning partial dislocations in order to maintain the ordered L12 structure of the gamma' precipitates. This reordering process helps to fundamentally explain the temperature and rate dependence of microtwinning under creep conditions within this temperature and stress regime. At a slightly higher temperature but lower stress (760°C and 345MPa), a stacking fault related shearing mechanism, which typically spanned only a few micrometers in length, was the principle deformation mode. The faults left behind in the gamma' precipitates determined to be extrinsic in nature. During creep at the highest temperature and lowest stress (815°C and 345MPa) a thermally

  12. Fatigue and creep-fatigue deformation of several nickel-base superalloys at 650 °c

    NASA Astrophysics Data System (ADS)

    Miner, R. V.; Gayda, J.; Maier, R. D.

    1982-10-01

    Specimens of seven nickel-base superalloys for gas turbine disk application that had been failed in fatigue and creep-fatigue at 650 °C were examined by transmission electron microscopy to observe the effects of composition and microstructure on the deformation characteristics of the alloys. The alloys were Waspaloy, HIP Astroloy, H+F Astroloy, H+F René 95, IN 100, MERL 76, and NASA IIB-7. The amount of bulk deformation observed in all the alloys was low. At inelastic strain amplitudes less than about 10-3 only favorably oriented grains exhibited yielding, and the majority of those had <110> near the tensile axis. Deformation occurred on octahedral systems for all the alloys except MERL 76, which also exhibited primary cube slip. The difference in slip behavior between MERL 76 and its parent composition, IN 100, was attributed to the addition of Nb. Deformation occurred in well-defined slip bands in the alloys that contained only fine aging γ', 0.01 to 0.06 μm in size. Alloys which also contained a population of larger aging γ' particles, 0.1 to 0.3 μm, exhibited more homogeneous deformation. Deformation in the creep-fatigue cycle, which employed a 15 minute dwell at the maximum tensile strain of the cycle, was not greatly different from fatigue deformation except that a few extended faults were formed.

  13. Features of the low-temperature creep of a Nb-Ti alloy after large plastic deformations at 77 K

    NASA Astrophysics Data System (ADS)

    Aksenov, V. K.; Volchok, O. I.; Karaseva, E. V.; Starodubov, Ya. D.

    2004-04-01

    The low-temperature (77 K) creep and the corresponding changes in the resistivity of a niobium-titanium alloy subjected to plastic deformation by drawing at 77 K are investigated. It is shown that after large plastic deformations (ɛ>99%) one observes anomalies of the low-temperature creep which do not appear in tests of samples subjected to low and medium deformations. The creep rate in the transient stage is significantly higher than would follow from the classical ideas about the mechanisms of low-temperature creep (logarithmic law), and the time dependence of the creep deformations is described by a power law, which corresponds to recovery creep. In the creep process oscillations appear on the resistivity curves; these are especially pronounced after drawing in liquid nitrogen. Possible causes of the observed effects are discussed.

  14. Circular Functions Based Comprehensive Analysis of Plastic Creep Deformations in the Fiber Reinforced Composites

    NASA Astrophysics Data System (ADS)

    Monfared, Vahid

    2016-06-01

    Analytically based model is presented for behavioral analysis of the plastic deformations in the reinforced materials using the circular (trigonometric) functions. The analytical method is proposed to predict creep behavior of the fibrous composites based on basic and constitutive equations under a tensile axial stress. New insight of the work is to predict some important behaviors of the creeping matrix. In the present model, the prediction of the behaviors is simpler than the available methods. Principal creep strain rate behaviors are very noteworthy for designing the fibrous composites in the creeping composites. Analysis of the mentioned parameter behavior in the reinforced materials is necessary to analyze failure, fracture, and fatigue studies in the creep of the short fiber composites. Shuttles, spaceships, turbine blades and discs, and nozzle guide vanes are commonly subjected to the creep effects. Also, predicting the creep behavior is significant to design the optoelectronic and photonic advanced composites with optical fibers. As a result, the uniform behavior with constant gradient is seen in the principal creep strain rate behavior, and also creep rupture may happen at the fiber end. Finally, good agreements are found through comparing the obtained analytical and FEM results.

  15. Brittle, creep and melt damage mechanics of the lithosphere: is slow creep deformation a key to intraplate volcanic provinces?

    NASA Astrophysics Data System (ADS)

    Liu, J.; Regenauer-Lieb, K.; Karrech, A.; Rosenbaum, G.; Lyakhovsky, V.

    2014-12-01

    We investigate the problem of intraplate melt generation with the aim of understanding spatial and temporal relationships between magmatism and extremely slow intraplate deformation. We present numerical models that consider feedback between melt generation and lithospheric deformation and incorporate three different damage mechanisms: brittle damage, creep damage, and melt damage. Melt conditions are calculated with a Gibbs energy minimization method, and the energy equation solved self-consistently for latent heat and shear heating effects. We use an extremely slowly lithosphere extension model (1-1.5 mm/y) to investigate the mechanics leading to intraplate volcanism in a cold lithosphere (~50mW/m2) such as the Harrat Ash-Shaam volcanic field in NW Arabia. We find that the extremely slow extension is a key to a very potent melt transfer mechanism through the lithosphere. The mechanism relies on multiple feedback mechanisms active in the accommodation of strain in the presence of fluids. These are capable of generating melts in the lithosphere/asthenosphere even in regions of relatively low heat flux. Once low degrees of partial melts are generated, the triple feedback between brittle-creep and melt damage leads to high porosity lithospheric-scale shear zones capable of transferring melts and fluids to the surface. Efficient localization in the weaker ductile domains implies that the final pattern of strain distribution is controlled by slow creep from below rather than by brittle deformation from above. Our model provides an explanation for intraplate volcanic provinces, which appear to rely on slowly deforming lithospheres. A significant finding is that slow extension, rather than fast extension, can localize melt damage more effectively in the deeper creeping section of the lithosphere. This finding may have profound implications to the fundamental dynamic control on intraplate volcanism.

  16. Deformational characteristics of thermoplastic elastomers

    NASA Astrophysics Data System (ADS)

    Indukuri, Kishore K.

    This thesis focuses primarily on the structure-property relationships of poly (styrene-ethylene-butylene-styrene) triblock copolymer TPEs. First evidence for strain-induced crystallization occurring in certain SEBS block copolymers has been established using unique techniques like deformation calorimetry, combined in-situ small angle X-ray and wide angle X-ray diffraction (SAXD/WAXD). Also the ramifications of such strain-induced crystallization on the mechanical properties like cyclic hysteresis, stress relaxation/creep retention of these SEBS systems have been studied. In addition, the structural changes in the morphology of these systems on deformation have been investigated using combined SAXD/WAXD setup. Small angle X-ray diffraction probed the changes at the nano-scale of polystyrene (PS) cylinders, while wide angle X-ray diffraction probed the changes at molecular length scales of the amorphous/crystalline domains of the elastomeric mid-block in these systems. New structural features at both these length scales have been observed and incorporated into the overall deformation mechanisms of the material. Continuous processing techniques like extrusion have been used to obtain ultra long-range order and orientation in these SEBS systems. Thus well ordered crystal like hexagonal packing of cylinders, where in each element in this hexagonal lattice can be individually addressed without any grain boundaries can be realized using these robust techniques. The effect of long-range order/orientation on the mechanical properties has been studied. In addition, these well ordered systems serve as model systems for evaluating deformation mechanisms of these SEBS systems, where the relative contributions of each of the phases can be estimated. EPDM/i-PP thermoplastic vulcanizates (TPVs) have micron size scale phase separated morphologies of EPDM rubber dispersed in a semicrystalline i-PP matrix as a result of the dynamic vulcanization process. Confocal microscopy studies

  17. Nonlinear deformation and localized failure of bacterial streamers in creeping flows

    PubMed Central

    Biswas, Ishita; Ghosh, Ranajay; Sadrzadeh, Mohtada; Kumar, Aloke

    2016-01-01

    We investigate the failure of bacterial floc mediated streamers in a microfluidic device in a creeping flow regime using both experimental observations and analytical modeling. The quantification of streamer deformation and failure behavior is possible due to the use of 200 nm fluorescent polystyrene beads which firmly embed in the extracellular polymeric substance (EPS) and act as tracers. The streamers, which form soon after the commencement of flow begin to deviate from an apparently quiescent fully formed state in spite of steady background flow and limited mass accretion indicating significant mechanical nonlinearity. This nonlinear behavior shows distinct phases of deformation with mutually different characteristic times and comes to an end with a distinct localized failure of the streamer far from the walls. We investigate this deformation and failure behavior for two separate bacterial strains and develop a simplified but nonlinear analytical model describing the experimentally observed instability phenomena assuming a necking route to instability. Our model leads to a power law relation between the critical strain at failure and the fluid velocity scale exhibiting excellent qualitative and quantitative agreeing with the experimental rupture behavior. PMID:27558511

  18. Nonlinear deformation and localized failure of bacterial streamers in creeping flows.

    PubMed

    Biswas, Ishita; Ghosh, Ranajay; Sadrzadeh, Mohtada; Kumar, Aloke

    2016-01-01

    We investigate the failure of bacterial floc mediated streamers in a microfluidic device in a creeping flow regime using both experimental observations and analytical modeling. The quantification of streamer deformation and failure behavior is possible due to the use of 200 nm fluorescent polystyrene beads which firmly embed in the extracellular polymeric substance (EPS) and act as tracers. The streamers, which form soon after the commencement of flow begin to deviate from an apparently quiescent fully formed state in spite of steady background flow and limited mass accretion indicating significant mechanical nonlinearity. This nonlinear behavior shows distinct phases of deformation with mutually different characteristic times and comes to an end with a distinct localized failure of the streamer far from the walls. We investigate this deformation and failure behavior for two separate bacterial strains and develop a simplified but nonlinear analytical model describing the experimentally observed instability phenomena assuming a necking route to instability. Our model leads to a power law relation between the critical strain at failure and the fluid velocity scale exhibiting excellent qualitative and quantitative agreeing with the experimental rupture behavior. PMID:27558511

  19. Deformation and crack growth response under cyclic creep conditions

    SciTech Connect

    Brust, F.W. Jr.

    1995-12-31

    To increase energy efficiency, new plants must operate at higher and higher temperatures. Moreover, power generation equipment continues to age and is being used far beyond its intended original design life. Some recent failures which unfortunately occurred with serious consequences have clearly illustrated that current methods for insuring safety and reliability of high temperature equipment is inadequate. Because of these concerns, an understanding of the high-temperature crack growth process is very important and has led to the following studies of the high temperature failure process. This effort summarizes the results of some recent studies which investigate the phenomenon of high temperature creep fatigue crack growth. Experimental results which detail the process of creep fatigue, analytical studies which investigate why current methods are ineffective, and finally, a new approach which is based on the T{sup *}-integral and its ability to characterize the creep-fatigue crack growth process are discussed. The potential validity of this new predictive methodology is illustrated.

  20. Deformation mechanisms responsible for the creep resistance of Ti-Al alloys

    SciTech Connect

    Morris, M.A.; Lipe, T.

    1997-12-31

    Two {gamma}-based Ti-Al alloys with similar grain sizes and, respectively, lamellar and duplex microstructures have been creep tested at 700 C and constant stresses ranging between 280 and 430 MPa. TEM observations have confirmed that the duplex alloy deforms by extensive mechanical twinning whose density increases with applied stress and increasing strain. The new twin interfaces subdivide the {gamma} grains throughout the primary stage of creep. At the onset of the minimum creep rate, the twin interfaces in the duplex alloy behave in the same way as the {gamma}/{gamma} or the {alpha}{sub 2}/{gamma} interfaces in the lamellar alloy. However, single dislocations were also present and it appears that in both alloys the deformation process is controlled by the accumulation and emission of dislocations from the different interfaces.

  1. Phase boundary mobility in naturally deformed, high-grade quartzofeldspathic rocks: evidence for diffusional creep

    NASA Astrophysics Data System (ADS)

    Gower, Robert J. W.; Simpson, Carol

    1992-03-01

    Grain shape fabrics and optical microstructures of some quartzofeldspathic rocks deformed under upper amphibolite facies conditions in the southwestern Grenville Province, Ontario, Canada, suggest that quartz and feldspar have accommodated intracrystalline plastic strains by both diffusional and dislocation creep. In these rocks, quartz and feldspar form polycrystalline domains separated by gently curved and locally cuspate phase boundaries whose morphology is similar in certain respects to the phase boundary morphology of rocks annealed experimentally under hydrostatic stress conditions. In the naturally deformed rocks, however, phase boundary cusps consistently point along the foliation and parallel to the mineral fibre lineation (i.e. in directions of inferred finite extension) which implies that phase boundary motion and cusp formation occurred during deformation. Optical microstructures in feldspar and crystallographic preferred orientations in quartz are consistent with the accommodation of some intracrystalline plastic strains by dislocation creep. However, the morphology of quartz-feldspar phase boundaries cannot be explained by either dislocation creep or static annealing alone. We propose that phase boundary motion resulted from a diffusion-assisted process involving dissolution at foliation-parallel quartz-feldspar phase boundaries, mass transfer over length scales of the order of feldspar domain size (≈200 μm or greater) and precipitation at quartz-feldspar phase boundary cusps. This study extends the range of natural deformation conditions under which diffusional creep has been identified in quartzofeldspathic rocks. It also has important implications for the natural rheological behavior of the mid- and lower-continental crust.

  2. Time-, stress-, and temperature-dependent deformation in nanostructured copper: Creep tests and simulations

    NASA Astrophysics Data System (ADS)

    Yang, Xu-Sheng; Wang, Yun-Jiang; Zhai, Hui-Ru; Wang, Guo-Yong; Su, Yan-Jing; Dai, L. H.; Ogata, Shigenobu; Zhang, Tong-Yi

    2016-09-01

    In the present work, we performed experiments, atomistic simulations, and high-resolution electron microscopy (HREM) to study the creep behaviors of the nanotwinned (nt) and nanograined (ng) copper at temperatures of 22 °C (RT), 40 °C, 50 °C, 60 °C, and 70 °C. The experimental data at various temperatures and different sustained stress levels provide sufficient information, which allows one to extract the deformation parameters reliably. The determined activation parameters and microscopic observations indicate transition of creep mechanisms with variation in stress level in the nt-Cu, i.e., from the Coble creep to the twin boundary (TB) migration and eventually to the perfect dislocation nucleation and activities. The experimental and simulation results imply that nanotwinning could be an effective approach to enhance the creep resistance of twin-free ng-Cu. The experimental creep results further verify the newly developed formula (Yang et al., 2016) that describes the time-, stress-, and temperature-dependent plastic deformation in polycrystalline copper.

  3. Creep Properties and Deformation Mechanisms of a FGH95 Ni-based Superalloy

    NASA Astrophysics Data System (ADS)

    Xie, Jun; Tian, Su-gui; Zhou, Xiao-ming

    2013-07-01

    By means of full heat treatment, microstructure observation, lattice parameters determination, and the measurement of creep curves, an investigation has been conducted into the microstructure and creep mechanisms of FGH95 Ni-based superalloy. Results show that after the alloy is hot isostatically pressed, coarse γ' phase discontinuously distributes along the previous particle boundaries. After solution treatment at high temperature and aging, the grain size has no obvious change, and the amount of coarse γ' phase decreases, and a high volume fraction of fine γ' phase dispersedly precipitates in the γ matrix. Moreover, the granular carbides are found to be precipitated along grain boundaries, which can hinder the grain boundaries' sliding and enhance the creep resistance of the alloy. By x-ray diffraction analysis, it is indicated that the lattice misfit between the γ and γ' phases decreases in the alloy after full heat treatment. In the ranges of experimental temperatures and applied stresses, the creep activation energy of the alloy is measured to be 630.4 kJ/mol. During creep, the deformation mechanisms of the alloy are that dislocations slip in the γ matrix or shear into the γ' phase. Thereinto, the creep dislocations move over the γ' phase by the Orowan mechanism, and the < { 1 10 } rangle super-dislocation shearing into the γ' phase can be decomposed to form the configuration of (1/3) < { 1 12 } rangle super-Shockleys' partials and the stacking fault.

  4. Characterization of micro-scale creep deformation of an electro-active paper actuator

    NASA Astrophysics Data System (ADS)

    Lee, Sangwoo; Kim, Joo-Hyung; Kang, Kwangseon; Kim, Jaehwan; Kim, Heung Soo; Yang, Chulho

    2009-09-01

    The creep deformation process of an electro-active paper (EAPap) actuator was investigated by adapting stepwise dead-weight loading. To understand the deformation mechanism of the EAPap film, including morphological and structural changes, various loading conditions below yield strength were applied to cellophane EAPap. From the structural observation, micro-dimples and micro-cracks were detected at applied load lower than 10% of yield strength, while they were not found in higher load conditions. It is hypothesized that only short and random fibers in the amorphous region may respond to the applied stress at the low loading condition, not the fibers in the crystalline area. As a result, deformation energy at the localized spot accumulated and created micro-defects at the surface. Meanwhile, fibers in the crystalline region may sustain most of the loads as creep load increases to a high level. Molecular chains in the fiber may rotate and elongate with high load. Elongated fibers were observed only at a high level of load. From the structural change as a function of applied load, a peak shift of crystal orientation was observed only in high load conditions by wide angle x-ray measurement. This may confirm that creep deformation could give rise to structure changes in EAPap.

  5. A microstructural study of creep and thermal fatigue deformation in 60Sn-40Pb solder joints

    SciTech Connect

    Tribula, D.

    1990-06-02

    Thermal fatigue failures of solder joints in electronic devices often arise from cyclic shear strains imposed by the mismatched thermal expansion coefficients of the materials that bind the joint as temperature changes are encountered. Increased solder joint reliability demands a fundamental understanding of the metallurigical mechanisms that control the fatigue to design accurate accelerated probative tests and new, more fatigue resistant solder alloys. The high temperatures and slow strain rates that pertain to thermal fatigue imply that creep is an important deformation mode in the thermal fatigue cycle. In this work, the creep behaviour of a solder joint is studied to determine the solder's microstructural response to this type of deformation and to relate this to the more complex problem of thermal fatigue. It is shown that creep failures arise from the inherent inhomogeneity and instability of the solder microstructure and suggest that small compositional changes of the binary near-eutectic Pn-Sn alloy may defeat the observed failure mechanisms. This work presents creep and thermal fatigue data for several near-eutectic Pb-Sn solder compositions and concludes that a 58Sn-40Pb-2In and a 58Sn-40Pb-2Cd alloy show significantly enhanced fatigue resistance over that of the simple binary material. 80 refs., 33 figs., 1 tab.

  6. Microstructures of beta silicon carbide after irradiation creep deformation at elevated temperatures

    SciTech Connect

    Katoh, Yutai; Kondo, Sosuke; Snead, Lance Lewis

    2008-01-01

    Microstructures of silicon carbide were examined by transmission electron microscopy (TEM) after creep deformation under neutron irradiation. Thin strip specimens of polycrystalline and monocrystalline, chemically vapor-deposited, beta-phase silicon carbide were irradiated in the high flux isotope reactor to 0.7-4.2 dpa at nominal temperatures of 640-1080 C in an elastically pre-strained bend stress relaxation configuration with the initial stress of {approx}100 MPa. Irradiation creep caused permanent strains of 0.6 to 2.3 x 10{sup -4}. Tensile-loaded near-surface portions of the crept specimens were examined by TEM. The main microstructural features observed were dislocation loops in all samples, and appeared similar to those observed in samples irradiated in non-stressed conditions. Slight but statistically significant anisotropy in dislocation loop microstructure was observed in one irradiation condition, and accounted for at least a fraction of the creep strain derived from the stress relaxation. The estimated total volume of loops accounted for 10-45% of the estimated total swelling. The results imply that the early irradiation creep deformation of SiC observed in this work was driven by anisotropic evolutions of extrinsic dislocation loops and matrix defects with undetectable sizes.

  7. Creep Deformation and Rupture Behavior of Single- and Dual-Pass 316LN Stainless-Steel-Activated TIG Weld Joints

    NASA Astrophysics Data System (ADS)

    Vijayanand, V. D.; Vasudevan, M.; Ganesan, V.; Parameswaran, P.; Laha, K.; Bhaduri, A. K.

    2016-03-01

    Creep deformation and rupture behavior of single-pass and dual-pass 316LN stainless steel (SS) weld joints fabricated by an autogenous activated tungsten inert gas welding process have been assessed by performing metallography, hardness, and conventional and impression creep tests. The fusion zone of the single-pass joint consisted of columnar zones adjacent to base metals with a central equiaxed zone, which have been modified extensively by the thermal cycle of the second pass in the dual-pass joint. The equiaxed zone in the single-pass joint, as well as in the second pass of the dual-pass joint, displayed the lowest hardness in the joints. In the dual-pass joint, the equiaxed zone of the first pass had hardness comparable to the columnar zone. The hardness variations in the joints influenced the creep deformation. The equiaxed and columnar zone in the first pass of the dual-pass joint was more creep resistant than that of the second pass. Both joints possessed lower creep rupture life than the base metal. However, the creep rupture life of the dual-pass joint was about twofolds more than that of the single-pass joint. Creep failure in the single-pass joint occurred in the central equiaxed fusion zone, whereas creep cavitation that originated in the second pass was blocked at the weld pass interface. The additional interface and strength variation between two passes in the dual-pass joint provides more restraint to creep deformation and crack propagation in the fusion zone, resulting in an increase in the creep rupture life of the dual-pass joint over the single-pass joint. Furthermore, the differences in content, morphology, and distribution of delta ferrite in the fusion zone of the joints favors more creep cavitation resistance in the dual-pass joint over the single-pass joint with the enhancement of creep rupture life.

  8. Creep Deformation and Rupture Behavior of Single- and Dual-Pass 316LN Stainless-Steel-Activated TIG Weld Joints

    NASA Astrophysics Data System (ADS)

    Vijayanand, V. D.; Vasudevan, M.; Ganesan, V.; Parameswaran, P.; Laha, K.; Bhaduri, A. K.

    2016-06-01

    Creep deformation and rupture behavior of single-pass and dual-pass 316LN stainless steel (SS) weld joints fabricated by an autogenous activated tungsten inert gas welding process have been assessed by performing metallography, hardness, and conventional and impression creep tests. The fusion zone of the single-pass joint consisted of columnar zones adjacent to base metals with a central equiaxed zone, which have been modified extensively by the thermal cycle of the second pass in the dual-pass joint. The equiaxed zone in the single-pass joint, as well as in the second pass of the dual-pass joint, displayed the lowest hardness in the joints. In the dual-pass joint, the equiaxed zone of the first pass had hardness comparable to the columnar zone. The hardness variations in the joints influenced the creep deformation. The equiaxed and columnar zone in the first pass of the dual-pass joint was more creep resistant than that of the second pass. Both joints possessed lower creep rupture life than the base metal. However, the creep rupture life of the dual-pass joint was about twofolds more than that of the single-pass joint. Creep failure in the single-pass joint occurred in the central equiaxed fusion zone, whereas creep cavitation that originated in the second pass was blocked at the weld pass interface. The additional interface and strength variation between two passes in the dual-pass joint provides more restraint to creep deformation and crack propagation in the fusion zone, resulting in an increase in the creep rupture life of the dual-pass joint over the single-pass joint. Furthermore, the differences in content, morphology, and distribution of delta ferrite in the fusion zone of the joints favors more creep cavitation resistance in the dual-pass joint over the single-pass joint with the enhancement of creep rupture life.

  9. Influence of flowing sodium on creep deformation and rupture behaviour of 316L(N) austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Ravi, S.; Laha, K.; Mathew, M. D.; Vijayaraghavan, S.; Shanmugavel, M.; Rajan, K. K.; Jayakumar, T.

    2012-08-01

    The influence of flowing sodium on creep deformation and rupture behaviour of AISI 316L(N) austenitic stainless steel has been investigated at 873 K over a stress range of 235-305 MPa. The results were compared with those obtained from testing in air environment. The steady state creep rates of the material were not influenced appreciably by the testing environments. The time to onset of tertiary stage of creep deformation was delayed in sodium environment. The creep-rupture lives of the material increased in sodium environment, which became more pronounced at lower applied stresses. The increase in rupture life of the material in flowing sodium was accompanied by an increase in rupture ductility. The creep damage on specimen surface as well as inside the specimen was less in specimen tested in sodium. SEM fractographic investigation revealed predominantly transgranular dimple failure for the specimen tested in sodium, whereas predominantly intergranular creep failure was observed in the air tested specimens. Almost no oxidation was observed in the specimens creep tested in the sodium environment. Absence of oxidation and less creep damage cavitation extended the secondary state in liquid sodium tests and lead to increase in creep rupture life and ductility of the material as compared to in air.

  10. Fatigue and Creep-Fatigue Deformation of an Ultra-Fine Precipitate Strengthened Advanced Austenitic Alloy

    SciTech Connect

    M.C. Carroll; L.J. Carroll

    2012-10-01

    An advanced austenitic alloy, HT-UPS (high-temperature ultrafine-precipitation-strengthened), has been identified as an ideal candidate material for the structural components of fast reactors and energy-conversion systems. HT-UPS alloys demonstrate improved creep resistance relative to 316 stainless steel (SS) through additions of Ti and Nb, which precipitate to form a widespread dispersion of stable nanoscale metallic carbide (MC) particles in the austenitic matrix. The low-cycle fatigue and creep-fatigue behavior of an HT-UPS alloy have been investigated at 650 °C and a 1.0% total strain, with an R-ratio of -1 and hold times at peak tensile strain as long as 150 min. The cyclic deformation response of HT-UPS is directly compared to that of standard 316 SS. The measured values for total cycles to failure are similar, despite differences in peak stress profiles and in qualitative observations of the deformed microstructures. Crack propagation is primarily transgranular in fatigue and creep-fatigue of both alloys at the investigated conditions. Internal grain boundary damage in the form of fine cracks resulting from the tensile hold is present for hold times of 60 min and longer, and substantially more internal cracks are quantifiable in 316 SS than in HT-UPS. The dislocation substructures observed in the deformed material differ significantly; an equiaxed cellular structure is observed in 316 SS, whereas in HT-UPS the microstructure takes the form of widespread and relatively homogenous tangles of dislocations pinned by the nanoscale MC precipitates. The significant effect of the fine distribution of precipitates on observed fatigue and creep-fatigue response is described in three distinct behavioral regions as it evolves with continued cycling.

  11. Creep deformation modeling of a tool steel with a tempered martensitic structure used for extrusion dies

    NASA Astrophysics Data System (ADS)

    Reggiani, Barbara; Donati, Lorenzo; Tomesani, Luca

    2011-05-01

    Aim of an extrusion die is to allow the production of the profile with the required dimension tolerances and quality level. One of the main impediment to achieve this aim could be an excessive die deformation due to the high cyclic loads and temperatures acting on the die during the extrusion process. In order to investigate the mechanisms that influence the die deformation, a physical experiment reproducing the thermo-mechanical conditions of a die was performed on a martensitic tool steel used for extrusion tools (AISI H11). The design of experiment consisted of 4 levels of temperature, 3 levels of stress and 3 types of load, i.e. pure creep, pure fatigue and creep-fatigue. In all cases, the same pattern of the mandrel displacement-time curve was found consisting of 3 stages as those typical of the strain evolution in a standard creep test with a marked primary phase. Thus, with the aim to define an easy-applicable equation to estimate the die deformation, the time hardening creep law was chosen. In order to obtain the temperature gradient within the specimen coupled thermo-electric simulations were previously performed. The nodal temperature have been then imported within the structural model and the mechanical properties assigned to the each element as a function of these values. Coefficients of the time-hardening law were optimized, for each testing condition, on the basis of experimental data starting from values for similar alloys found in literature. The values found were validated against additional experimental data performed with different specimen geometries. A good average agreement was found between experimental and numerical results.

  12. Elevated temperature flow strength, creep resistance and diffusion welding characteristics of Ti-6Al-2Nb-1Ta-0.8Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.; Moore, T. J.

    1979-01-01

    A study of the flow strength, creep resistance and diffusion welding characteristics of the titanium alloy Ti-6Al-2Nb-1Ta-0.8Mo has been conducted. Two mill-processed forms of this alloy were examined. The forged material had been processed above the beta transus (approximately 1275 K) while the rolled form had been subjected to work below the beta transus. Between 1150 and 1250 K, the forged material was stronger and more creep resistant than the rolled alloy. Both forms exhibit superplastic characteristics in this temperature range. Strain measurements during diffusion welding experiments at 1200 K reveal that weld interfaces have no measurable effect on the overall creep deformation. Significant deformation appears to be necessary to produce a quality diffusion weld between superplastic materials. A 'soft' interlayer inserted between faying surfaces would seemingly allow manufacture of quality diffusion welds with little overall deformation.

  13. Elevated-temperature flow strength, creep resistance and diffusion welding characteristics of Ti-gAl-2Nb-1Ta-0.8Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.; Moore, T. J.

    1977-01-01

    A study of the flow strength, creep resistance and diffusion welding characteristics of the titanium alloy Ti-6Al-2Nb-1Ta-0.8Mo was conducted. Two mill-processed forms of this alloy were examined. The forged material was essentially processed above the beta transus while the rolled form was subjected to considerable work below the beta transus. Between 1150 and 1250 K, the forged material was stronger and more creep resistant than the rolled alloy. Both forms exhibit superplastic characteristics in this temperature range. Strain measurements during diffusion welding experiments at 1200 K reveal that weld interfaces have no measurable effect on the overall creep deformation. Significant deformation appears to be necessary to produce a quality diffusion weld between superplastic materials. A 'soft' interlayer inserted between faying surfaces would seemingly allow manufacture of quality diffusion welds with little overall deformation.

  14. Understanding creep in sandstone reservoirs - theoretical deformation mechanism maps for pressure solution in granular materials

    NASA Astrophysics Data System (ADS)

    Hangx, Suzanne; Spiers, Christopher

    2014-05-01

    Subsurface exploitation of the Earth's natural resources removes the natural system from its chemical and physical equilibrium. As such, groundwater extraction and hydrocarbon production from subsurface reservoirs frequently causes surface subsidence and induces (micro)seismicity. These effects are not only a problem in onshore (e.g. Groningen, the Netherlands) and offshore hydrocarbon fields (e.g. Ekofisk, Norway), but also in urban areas with extensive groundwater pumping (e.g. Venice, Italy). It is known that fluid extraction inevitably leads to (poro)elastic compaction of reservoirs, hence subsidence and occasional fault reactivation, and causes significant technical, economic and ecological impact. However, such effects often exceed what is expected from purely elastic reservoir behaviour and may continue long after exploitation has ceased. This is most likely due to time-dependent compaction, or 'creep deformation', of such reservoirs, driven by the reduction in pore fluid pressure compared with the rock overburden. Given the societal and ecological impact of surface subsidence, as well as the current interest in developing geothermal energy and unconventional gas resources in densely populated areas, there is much need for obtaining better quantitative understanding of creep in sediments to improve the predictability of the impact of geo-energy and groundwater production. The key problem in developing a reliable, quantitative description of the creep behaviour of sediments, such as sands and sandstones, is that the operative deformation mechanisms are poorly known and poorly quantified. While grain-scale brittle fracturing plus intergranular sliding play an important role in the early stages of compaction, these time-independent, brittle-frictional processes give way to compaction creep on longer time-scales. Thermally-activated mass transfer processes, like pressure solution, can cause creep via dissolution of material at stressed grain contacts, grain

  15. Micro-scale strain mapping technique: a tool to quantify strain partitioning during creep deformation

    NASA Astrophysics Data System (ADS)

    Quintanilla-Terminel, Alejandra; Zimmerman, Mark; Evans, Brian; Kohlstedt, David

    2016-04-01

    Several deformation mechanisms interact to accommodate plastic deformation. Quantifying the contribution of each to the total strain is necessary for establishing a better link between observed microstructures and mechanical data, as well as to allow more confident extrapolation from laboratory to natural conditions. In this contribution, we present the experimental and computational technique involved in micro-scale strain mapping (MSSM). The MSSM technique relies on analyzing the relative displacement of initially regularly spaced markers after deformation. We present several microfabrication techniques that permit us to pattern various rocks with micrometric and nanometric metal markers, as well as the challenges faced in working at high temperatures and pressures. A Hough transform algorithm was used to detect the markers and automate as much as possible the strain analysis. The von Mises strain is calculated for a set of n-points and their relative displacements, which allow us to map the strain at different length scales. We applied the MSSM technique to study strain partitioning during deformation creep of Carrara marble and San Carlos olivine at a confining pressure, Pc, of 300 MPa and homologous temperatures of 0.3 to 0.6. We measured the local strain and strain heterogeneity produced during creep deformation of split cylinders of Carrara marble under conventional triaxial loading to inelastic strains of 11 to 36% at a strain rate of 3x10‑5s‑1, Pc = 300 MPa and 400o < T <700oC. We conclude that the evolution of deformation structures in marble takes place over a substantial interval in strain and that the duration of this interval depends on strain rate, temperature, and pressure. Our first results on strain mapping of olivine deformed at T = 1150oC and Pc = 300 MPa demonstrate promise for characterizing intragranular strain and better defining the contribution of grain boundary sliding to the total strain.

  16. Intragranular deformation heterogeneities during the creep of ice polycrystals: experimental measurements vs. modeling

    NASA Astrophysics Data System (ADS)

    Grennerat, F.; Montagnat, M.; Castelnau, O.; Vacher, P.; Suquet, P.; Moulinec, H.; Duval, P.

    2011-12-01

    Similarly as minerals from the Earth mantle, ice exhibits a strongly anisotropic rheology resulting from the small number of independent slip systems for dislocations. Therefore, a significant heterogeneity of stress and strain distributions is expected at the inter- and intra-granular scale during polycrystal deformation, owing to the mechanical interaction between adjacent grains. A Digital Image Correlation (DIC) technique has been adapted to polycrystalline ice specimens in order to characterize the development of strain heterogeneities at an intragranular scale during transient creep deformation. Specimens exhibit a columnar microstructure so that plastic deformation is essentially 2-D with no in-depth gradients, and therefore surface DIC analyses are representative for the whole specimen volume. Local misorientations at the intragranular scale were also extracted from microstructure analyses carried out with an automatic texture analyzer before and after deformation. Highly localized strain patterns are evidenced by the DIC technique. Local equivalent strain can reach values as high as one order of magnitude larger than the macroscopic average. The structure of the strain pattern does not evolve with strain in the transient creep regime. Almost no correlation between the measured local strain and the Schmid factor of the slip plane of the underlying grain is observed, highlighting the importance of the mechanical interactions between neighboring grains resulting from the very large viscoplastic anisotropy of ice crystals. Finally, the experimental microstructure was introduced in a full-field FFT polycrystal model; simulated strain fields are in good match with experimental ones.

  17. Cell structure in cold worked and creep deformed phosphorus alloyed copper

    SciTech Connect

    Wu, Rui; Pettersson, Niklas; Martinsson, Åsa; Sandström, Rolf

    2014-04-01

    Transmission electron microscopy (TEM) examinations on as-received, cold worked, as well as cold worked and creep tested phosphorus-alloyed oxygen-free copper (Cu-OFP) have been carried out to study the role of the cell structure. The cell size decreased linearly with increasing plastic deformation in tension. The flow stress in the tests could also be correlated to the cell size. The observed relation between the flow stress and the cell size was in excellent agreement with previously published results. The dense dislocation walls that appeared after cold work in tension is likely to be the main reason for the dramatic increase in creep strength. The dense dislocation walls act as barriers against dislocation motion and their presence also reduces the recovery rate due to an unbalanced dislocation content.

  18. Dissolution and Replacement Creep:A Significant Deformation Mechanism in Mid-crustal Rocks

    NASA Astrophysics Data System (ADS)

    Wintsch, R. P.

    2001-12-01

    Zoning patterns and zoning truncations in metamorphic minerals in a granodioritic orthogneiss from the Bronson Hill terrane, New England indicate that strain and S-C fabrics in these rocks were produced by dissolution, precipitation, and replacement processes, even at epidote-amphibolite facies metamorphic conditions. The metamorphic fabric is defined by alternating layers and folia dominated by quartz, feldspars, and biotite + epidote. Zoning patterns in most metamorphic plagioclase, orthoclase, epidote, and sphene are truncated at boundaries normal to the shortening direction, suggesting dissolution. Interfaces of relict igneous orthoclase phenocrysts that face the shortening direction are embayed and replaced by biotite, epidote and myrmekitic intergrowths of plagioclase and quartz. Metamorphic plagioclase grains are also replaced by epidote. We interpret these microstructures to reflect strain-enhanced dissolution. The cores of many grains show asymmetric overgrowths with at least two generations of beards, all oriented on the ends of grains that face the extension direction. We interpret these textures to reflect precipitation of components dissolved by deformation enhanced dissolution. While biotite and quartz probably deformed by dislocation creep, the overall deformation was accommodated by dissolution perpendicular to the shortening direction, and precipitation parallel to it. These chemical processes must have been activated at lower stresses than the dislocation creep predicted from extrapolations of data from experiments in dry rocks. Thus wet crust is likely to be weaker than calculated from these experimental studies. Where such processes dominate, stress may not be high enough to reach brittle failure.

  19. Dissolution and replacement creep: a significant deformation mechanism in mid-crustal rocks

    NASA Astrophysics Data System (ADS)

    Wintsch, R. P.; Yi, Keewook

    2002-07-01

    Zoning patterns and zoning truncations in metamorphic minerals in a granodioritic orthogneiss indicate that strain and S- C fabrics in these rocks were produced by dissolution, precipitation, and replacement processes, even at epidote-amphibolite facies metamorphic conditions. The metamorphic fabric is defined by alternating layers and folia dominated by quartz, feldspars, and biotite+epidote. Zoning patterns in most metamorphic plagioclase, orthoclase, epidote, and sphene are truncated at boundaries normal to the shortening direction, suggesting dissolution. Interfaces of relict igneous orthoclase phenocrysts that face the shortening direction are embayed and replaced by biotite, epidote, and myrmekitic intergrowths of plagioclase and quartz. Metamorphic plagioclase grains are also replaced by epidote. We interpret these microstructures to reflect strain-enhanced dissolution. The cores of many grains show asymmetric overgrowths with at least two generations of beards, all oriented on the ends of grains that face the extension direction. We interpret these textures to reflect precipitation of components dissolved by deformation-enhanced dissolution. While biotite and quartz probably deformed by dislocation creep, the overall deformation was accommodated by dissolution perpendicular to the shortening direction, and precipitation parallel to it. These chemical processes must have been activated at lower stresses than the dislocation creep predicted from extrapolations of data from experiments in dry rocks. Thus wet crust is likely to be weaker than calculated from these experimental studies.

  20. Analysis of Mining Terrain Deformation Characteristics with Deformation Information System

    NASA Astrophysics Data System (ADS)

    Blachowski, Jan; Milczarek, Wojciech; Grzempowski, Piotr

    2014-05-01

    Mapping and prediction of mining related deformations of the earth surface is an important measure for minimising threat to surface infrastructure, human population, the environment and safety of the mining operation itself arising from underground extraction of useful minerals. The number of methods and techniques used for monitoring and analysis of mining terrain deformations is wide and increasing with the development of geographical information technologies. These include for example: terrestrial geodetic measurements, global positioning systems, remote sensing, spatial interpolation, finite element method modelling, GIS based modelling, geological modelling, empirical modelling using the Knothe theory, artificial neural networks, fuzzy logic calculations and other. The aim of this paper is to introduce the concept of an integrated Deformation Information System (DIS) developed in geographic information systems environment for analysis and modelling of various spatial data related to mining activity and demonstrate its applications for mapping and visualising, as well as identifying possible mining terrain deformation areas with various spatial modelling methods. The DIS concept is based on connected modules that include: the spatial database - the core of the system, the spatial data collection module formed by: terrestrial, satellite and remote sensing measurements of the ground changes, the spatial data mining module for data discovery and extraction, the geological modelling module, the spatial data modeling module with data processing algorithms for spatio-temporal analysis and mapping of mining deformations and their characteristics (e.g. deformation parameters: tilt, curvature and horizontal strain), the multivariate spatial data classification module and the visualization module allowing two-dimensional interactive and static mapping and three-dimensional visualizations of mining ground characteristics. The Systems's functionality has been presented on

  1. CREEP-2: Long-term time-dependent rock deformation in a deep-sea observatory.

    NASA Astrophysics Data System (ADS)

    Boon, Steve; Meredith, Philip; Heap, Michael; Berenzoli, Laura; Favali, Paolo

    2010-05-01

    Earthquake rupture and volcanic eruptions are the most spectacular manifestations of dynamic failure of a critically stressed crust. But these are actually rather rare events, and most of the crust spends most of its time in a highly-stressed but sub-critical state. Below a few hundred metres, the crust is saturated, and water-rock chemical reactions lead to time-dependent deformation that allows rocks to fail over extended periods of time at stresses far below their short-term strength by the mechanism of stress corrosion crack growth. This process is highly non-linear and a change in applied stress of around 5% can lead to a change in the time-to-failure of more than an order of magnitude. Theoretical calculations based on reaction rate theory suggest that such cracking may occur down to stresses as low as 20% of the rock strength, implying that time-dependent cracking will be an important deformation mechanism over geological time and at typical tectonic strain rates. A number of theoretical models have been proposed to explain this behaviour. However, it is currently not possible to discriminate between these competing models due to the relatively narrow bandwidth of strain rates that are practicably achievable in conventional laboratory experiments. Ultra-long-term experiments at very low strain rates are clearly essential to address this problem. We have therefore used the stability of the deep-sea environment to conduct ultra-long-term experiments. At depth, the temperature remains constant throughout the year and water pressure also remains essentially constant, especially in the Ionian Sea where the tidal range is minimal. We have successfully conducted a pilot experiment (CREEP-1) in which we used the constant sea-water pressure at depth to provide both a constant confining pressure and a constant deforming stress for our rock samples. Building on that success, we are now building a multi-sample deformation observatory (CREEP-2) to be deployed at

  2. Transient creep, aseismic damage and slow failure in Carrara marble deformed across the brittle-ductile transition

    NASA Astrophysics Data System (ADS)

    Schubnel, A.; Walker, E.; Thompson, B. D.; Fortin, J.; Guéguen, Y.; Young, R. P.

    2006-09-01

    Two triaxial compression experiments were performed on Carrara marble at high confining pressure, in creep conditions across the brittle-ductile transition. During cataclastic deformation, elastic wave velocity decrease demonstrated damage accumulation (microcracks). Keeping differential stress constant and reducing normal stress induced transient creep events (i.e., fast accelerations in strain) due to the sudden increase of microcrack growth. Tertiary creep and brittle failure followed as damage came close to criticality. Coalescence and rupture propagation were slow (60-200 seconds with ~150 MPa stress drops and millimetric slips) and radiated little energy in the experimental frequency range (0.1-1 MHz). Microstructural analysis pointed out strong interactions between intra-crystalline plastic deformation (twinning and dislocation glide) and brittle deformation (microcracking) at the macroscopic level. Our observations highlight the dependence of acoustic efficiency on the material's rheology, at least in the ultrasonic frequency range, and the role played by pore fluid diffusion as an incubation process for delayed failure triggering.

  3. Poroelastic response of articular cartilage by nanoindentation creep tests at different characteristic lengths.

    PubMed

    Taffetani, M; Gottardi, R; Gastaldi, D; Raiteri, R; Vena, P

    2014-07-01

    Nanoindentation is an experimental technique which is attracting increasing interests for the mechanical characterization of articular cartilage. In particular, time dependent mechanical responses due to fluid flow through the porous matrix can be quantitatively investigated by nanoindentation experiments at different penetration depths and/or by using different probe sizes. The aim of this paper is to provide a framework for the quantitative interpretation of the poroelastic response of articular cartilage subjected to creep nanoindentation tests. To this purpose, multiload creep tests using spherical indenters have been carried out on saturated samples of mature bovine articular cartilage achieving two main quantitative results. First, the dependence of indentation modulus in the drained state (at equilibrium) on the tip radius: a value of 500 kPa has been found using the large tip (400 μm radius) and of 1.7 MPa using the smaller one (25 μm). Secon, the permeability at microscopic scale was estimated at values ranging from 4.5×10(-16) m(4)/N s to 0.1×10(-16) m(4)/N s, from low to high equivalent deformation. Consistently with a poroelastic behavior, the size-dependent response of the indenter displacement disappears when characteristic size and permeability are accounted for. For comparison purposes, the same protocol was applied to intrinsically viscoelastic homogeneous samples of polydimethylsiloxane (PDMS): both indentation modulus and time response have been found size-independent. PMID:24814573

  4. Creep deformation and rupture behavior of CLAM steel at 823 K and 873 K

    NASA Astrophysics Data System (ADS)

    Zhong, Boyu; Huang, Bo; Li, Chunjing; Liu, Shaojun; Xu, Gang; Zhao, Yanyun; Huang, Qunying

    2014-12-01

    China Low Activation Martensitic (CLAM) steel is selected as the candidate structural material in Fusion Design Study (FDS) series fusion reactor conceptual designs. The creep property of CLAM steel has been studied in this paper. Creep tests have been carried out at 823 K and 873 K over a stress range of 150-230 MPa. The creep curves showed three creep regimes, primary creep, steady-state creep and tertiary creep. The relationship between minimum creep rate (ε˙min) and the applied stress (σ) could be described by Norton power law, and the stress exponent n was decreased with the increase of the creep temperature. The creep mechanism was analyzed with the fractographes of the rupture specimens which were examined by scanning electron microscopy (SEM). The coarsening of precipitates observed with transmission electron microscope (TEM) indicated the microstructural degradation after creep test.

  5. Experimental and computational simulation studies on creep deformation mechanisms of a novel nanostructured Cu and Cu-10%Sn Alloy

    NASA Astrophysics Data System (ADS)

    Abo-Elsoud, Mohamed A.

    2015-04-01

    This work presents experimental and computational simulation studies on creep deformation mechanisms of a novel nanostructured Cu and Cu-10%Sn alloy that prepared by mechanical alloying (MA) copper with elemental Tin. Mechanical Newtonian creep model is employed for computational simulation of creep deformation mechanism under low stress-high temperature and to justify the experimental findings. The observed behaviors are discussed and compared with the predications of the Nabarro-Herring (N-H) theory of directional diffusion. A simple theory based on the climb controlled generation of dislocations from a fixed density of sources is developed to explain the observed behavior. TEM and SEM investigations are convenient and powerful techniques for characterization of phases and a novel nano-grain structured of the resulting materials. The reduction of grain size to the nanometer scale improves their mechanical properties.

  6. Dislocation decorrelation and relationship to deformation microtwins during creep of a y' precipitate strengthened Ni-based superalloy

    SciTech Connect

    Unocic, R. R.; Zhou, N.; Kovarik, Libor; Shen, C.; Wang, Y.; Mills, M. J.

    2011-11-01

    The evolution of microtwins during high temperature creep deformation in a strengthened Ni-base superalloy has been investigated through a combination of creep testing, TEM characterization, theoretical modeling and computer simulation. Experimentally, microtwin nucleation sources were identified and their evolution was tracked by characterizing the deformation substructure at different stages of the creep deformation. Initially, deformation is highly localized around stress concentrators such as carbides, borides and serrated grain boundaries, which act as sources of a/2<110> matrix type dislocations. Due to microstructural effects such as fine channels between particles and low matrix stacking fault energies, the a/2<110> matrix dislocations dissociate into a/6<112> Shockley partials, which were commonly observed to be decorrelated from one another, creating extended intrinsic stacking faults in the matrix. As deformation progress further, microtwins form via partial dislocations cooperatively shearing both and phases on adjacent {111} glide planes. The TEM observations lead directly to an analysis of dislocation-precipitate interactions. Through phase field simulations and theoretical analysis based on Orowan looping, the important processes of dislocation dissociation and decorrelation are modeled in detail, providing comprehensive insight into the microstructural features and applied stress conditions that favor the microtwinning deformation mode in strengthened Ni-based superalloys.

  7. 3D microstructural and microchemical characteristics of SAFOD fault gouge: implications for understanding fault creep

    NASA Astrophysics Data System (ADS)

    Warr, Laurence; Wojatschke, Jasmaria; Carpenter, Brett; Marone, Chris; Schleicher, Anja; van der Pluijm, Ben

    2013-04-01

    Fault creep on the SAFOD section of the San Andreas Fault occurs along mechanically weak fault gouge characterized by high proportions of hydrous clay minerals, namely smectite, illite-smectite and chlorite-smectite phases. These minerals are concentrated along closely spaced, interconnected polished slip surfaces that give the gouge its characteristic scaly fabric. Although it is generally accepted that the creep behavior of the gouge relates to the concentration of these minerals, the precise mechanisms by which clay minerals weaken rock is currently a topic of debate. In this contribution we present the first results from a "slice-and-view" study of SAFOD gouge material by focused ion beam - scanning electron microscopy (Zeiss Auriga FIB/SEM), which allows the reconstruction of the microstructure and microchemistry of mineralized slip surfaces in 3D. The core and cuttings samples studied were selected from ca. 3297 m measured depth and represent some of the weakest materials yet recovered from the borehole, with a frictional coefficient of ca. 0.10 and a healing rate close to zero. This gouge contains abundant serpentine and smectite minerals, the latter of which was identified by X-ray diffraction to be saponite, after Mg- and glycol intercalation. Imaging and chemical analyses reveal nanometer scale thin alteration seams of saponite clay distributed throughout the ca. 50 micron thick sheared serpentinite layer that coats the slip surfaces. The base of this layer is defined by cataclastically deformed iron oxide minerals. The 3D fabric implies the orientation of the hydrated smectite minerals, which are interconnected and lie commonly sub parallel to the slip surface, are responsible for the gouge creep behavior in the laboratory. These minerals, and related interlayered varieties, are particularly weak due to their thin particle size and large quantities of adsorbed water, properties that are expected to persist down to mid-crustal depth (ca. 10 km). Creep of

  8. Characteristics of irradiation creep in the first wall of a fusion reactor

    SciTech Connect

    Coghlan, W.A.; Mansur, L.K.

    1981-01-01

    A number of significant differences in the irradiation environment of a fusion reactor are expected with respect to the fission reactor irradiation environment. These differences are expected to affect the characteristics of irradiation creep in the fusion reactor. Special conditions of importance are identified as the (1) large number of defects produced per pka, (2) high helium production rate, (3) cyclic operation, (4) unique stress histories, and (5) low temperature operations. Existing experimental data from the fission reactor environment is analyzed to shed light on irradiation creep under fusion conditions. Theoretical considerations are used to deduce additional characteristics of irradiation creep in the fusion reactor environment for which no experimental data are available.

  9. Dislocation creep accommodated Grain Boundary Sliding: A high strain rate/low temperature deformation mechanism in calcite ultramylonites

    NASA Astrophysics Data System (ADS)

    Rogowitz, Anna; Grasemann, Bernhard

    2014-05-01

    Grain boundary sliding (GBS) is an important grain size sensitive deformation mechanism that is often associated with extreme strain localization and superplasticity. Another mechanism has to operate simultaneously to GBS in order to prevent overlaps and voids between sliding grains. One of the most common accommodating mechanisms is diffusional creep but, recently, dislocation creep has been reported to operate simultaneous to GBS. Due to the formation of a flanking structure in nearly pure calcite marble on Syros (Cyclades, Greece) at lower greenschist facies conditions, an extremely fine grained ultramylonite developed. The microstructure of the layer is characterized by (1) calcite grains with an average grain size of 3.6 µm (developed by low temperature/high strain rate grain boundary migration recrystallization, BLG), (2) grain boundary triple junctions with nearly 120° angles and (3) small cavities preferentially located at triple junctions and at grain boundaries in extension. These features suggest that the dominant deformation mechanism was GBS. In order to get more information on the accommodation mechanism detailed microstructural and textural analyses have been performed on a FEI Quanta 3D FEG instrument equipped with an EDAX Digiview IV EBSD camera. The misorientation distribution curves for correlated and uncorrelated grains follow almost perfect the calculated theoretical curve for a random distribution, which is typical for polycrystalline material deformed by GBS. However, the crystallographic preferred orientation indicates that dislocation creep might have operated simultaneously. We also report Zener-Stroh cracks resulting from dislocation pile up, indicating that dislocation movement was active. We, therefore, conclude that the dominant deformation mechanism was dislocation creep accommodated grain boundary sliding. This is consistent with the observed grain size range that plots at the field boundary between grain size insensitive and grain

  10. Dislocation decorrelation and relationship to deformation microtwins during creep of a precipitate strengthened Ni-based superalloy

    SciTech Connect

    Unocic, Raymond R; Zhou, Ning; Kovarik, Libor; Shen, Chen; Wang, Yunzhi; Mills, Michael J.

    2011-01-01

    The evolution of microtwins during high temperature creep deformation in a strengthened Ni-base superalloy has been investigated through a combination of creep testing, transmission electron microscopy (TEM), theoretical modeling, and computer simulation. Experimentally, microtwin nucleation sources were identified and their evolution was tracked by characterizing the deformation substructure at different stages of creep deformation. Deformation is highly localized around stress concentrators such as carbides, borides and serrated grain boundaries, which act as sources of a/2<110> matrix-type dislocations. Due to fine channels between particles, coupled with the low matrix stacking fault energy, the a/2<110> matrix dislocations dissociate into a/6<112> Shockley partials, which were commonly observed to be decorrelated from one another, creating extended intrinsic stacking faults in the matrix. Microtwins are common and form via Shockley partial dislocations cooperatively shearing both and phases on adjacent {111} glide planes. The TEM observations lead directly to an analysis of dislocation-precipitate interactions. Through phase field simulations and theoretical analyses based on Orowan looping, the important processes of dislocation dissociation and decorrelation are modeled in detail, providing comprehensive insight into the microstructural features and applied stress conditions that favor the microtwinning deformation mode in strengthened Ni-based superalloys.

  11. Quantitative analysis of microstructure deformation in creep fenomena of ferritic SA-213 T22 and austenitic SA-213 TP304H material

    NASA Astrophysics Data System (ADS)

    Mulyana, Cukup; Taufik, Ahmad; Gunawan, Agus Yodi; Siregar, Rustam Efendi

    2013-09-01

    The failure of critical component of fossil fired power plant that operated in creep range (high stress, high temperature and in the long term) depends on its microstructure characteristics. Ferritic low carbon steel (2.25Cr-1Mo) and Austenitic stainless alloy (18Cr-8Ni) are used as a boiler tube in the secondary superheater outlet header to deliver steam before entering the turbin. The tube failure is occurred in a form of rupture, resulting trip that disrupts the continuity of the electrical generation. The research in quantification of the microstructure deformation has been done in predicting the remaining life of the tube through interrupted accelerated creep test. For Austenitic Stainless Alloy (18Cr-8Ni), creep test was done in 550°C with the stress 424.5 MPa and for Ferritic Low Carbon Steel (2.25Cr-1Mo) in 570°C with the stress 189 MPa. The interrupted accelerated creep test was done by stopping the observation in condition 60%, 70%, 80% and 90% of remaining life, the creep test fracture was done before. Then the micro hardness test, photo micro, SEM and EDS were obtained from those samples. Refer to ASTM E122, microstructure parameters were calculated. The results indicated that there are a consistency of decreasing their grain diameters, increasing their grain size numbers, micro hardness, and the length of crack or void number per unit area with the decreasing of remaining life. While morphology of grain (stated in parameter α=LV/LH) relatively constant for austenitic. However, for ferritic the change of morphology revealed significantly. Fracture mode propagation of ferritic material is growth with voids transgranular and intergranular crack, and for austenitic material the fracture growth with intergranular creep fracture void and wedge crack. In this research, it was proposed a formulation of mathematical model for creep behavior corresponding their curve fitting resulted for the primary, secondary and tertiary in accelerated creep test. In

  12. Core Characteristics Deterioration due to Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Kaido, Chikara; Arai, Satoshi

    This paper discusses the effect of plastic deformation at core manufacturing on the characteristics of cores where non-oriented electrical steel sheets are used as core material. Exciting field and iron loss increase proportionally to plastic deformation in the case of rP<10, where rP is a ratio of plastic deformation to that at yield point. In this region, anomalous eddy currents increase because plastic deformations of crystalline grains are distributed and then the flux distribution is induced. In the case of rP>20, the deterioration tend to saturate, and the increases in magnetic field and iron loss are 1000 to 1500A/m and 2 to 4W/kg. They are related to grain size, and high grade with larger grain may have lager field increase and smaller iron loss increase. Anomalous eddy current losses scarcely increase in this region. In actual motors, the plastic deformation affects iron loss increase although exciting current increases a little.

  13. Creep deformation and fracture behavior of types 316 and 316L(N) stainless steels and their weld metals

    SciTech Connect

    Sasikala, G.; Mathew, M.D.; Bhanu Sankara Rao, K.; Mannan, S.L.

    2000-04-01

    The creep properties of a nuclear-grade type 316(L) stainless steel (SS) alloyed with nitrogen (316L(N)SS) and its weld metal were studied at 873 and 923 K in the range of applied stresses from 100 to 335 MPa. The results were compared with those obtained on a nuclear-grade type 316 SS, which is lean in nitrogen. The creep rupture lives of the weld metals were found to be lower than those of the respective base metals by a factor of 5 to 10. Both the base and weld metals of 314L(N)SS exhibited better resistance to creep deformation compared to their 316SS counterparts at identical test conditions. A power-law relationship between the minimum creep rate and applied stress was found to be obeyed for both the base and weld metals. Both the weld metals generally exhibited lower rupture elongation than the respective base metals; however, at 873 K, the 316 SS base and weld metals had similar rupture elongation at identical applied stresses. Comparison of the rupture lives of the two steels to the ASME curves for the expected minimum stress to rupture for 316 Ss base and weld metals showed that, for 316L(N) SS, the specifications for maximum allowable stresses based on data for 316 SS could prove overconservative. The influence of nitrogen on the creep deformation and fracture behavior, especially in terms of its modifying the precipitation kinetics, is discussed in light of the microstructural observations. In welds containing {delta} ferrite, the kinetics of its transformation and the nature of the transformation products control the deformation and fracture behavior. The influence of nitrogen on the {delta} ferrite transformation behavior and coarsening kinetics is also discussed, on the basis of extensive characterization by metallographic techniques.

  14. Creep deformation and fracture behavior of types 316 and 316L(N) stainless steels and their weld metals

    NASA Astrophysics Data System (ADS)

    Sasikala, G.; Mannan, S. L.; Mathew, M. D.; Rao, K. Bhanu

    2000-04-01

    The creep properties of a nuclear-grade type 316(L) stainless steel (SS) alloyed with nitrogen (316L(N) SS) and its weld metal were studied at 873 and 923 K in the range of applied stresses from 100 to 335 MPa. The results were compared with those obtained on a nuclear-grade type 316 SS, which is lean in nitrogen. The creep rupture lives of the weld metals were found to be lower than those of the respective base metals by a factor of 5 to 10. Both the base and weld metals of 316L(N) SS exhibited better resistance to creep deformation compared to their 316 SS counterparts at identical test conditions. A power-law relationship between the minimum creep rate and applied stress was found to be obeyed for both the base and weld metals. Both the weld metals generally exhibited lower rupture elongation than the respective base metals; however, at 873 K, the 316 SS base and weld metals had similar rupture elongation at identical applied stresses. Comparison of the rupture lives of the two steels to the ASME curves for the expected minimum stress to rupture for 316 SS base and weld metals showed that, for 316L(N) SS, the specifications for maximum allowable stresses based on data for 316 SS could prove overconservative. The influence of nitrogen on the creep deformation and fracture behavior, especially in terms of its modifying the precipitation kinetics, is discussed in light of the microstructural observations. In welds containing δ ferrite, the kinetics of its transformation and the nature of the transformation products control the deformation and fracture behavior. The influence of nitrogen on the δ ferrite transformation behavior and coarsening kinetics is also discussed, on the basis of extensive characterization by metallographic techniques.

  15. An investigation of the deformation mechanism in grain size-sensitive Newtonian creep

    SciTech Connect

    Wang, J.N.

    2000-04-19

    Creep of polycrystalline materials at low stresses often shows a linear relationship between strain rate and stress, and an inverse dependence on grain size squared or cubed. Attribution of this behavior to diffusional creep or grain boundary sliding (GBS) has evoked much confusion and controversy in the literature. A model is proposed to unify these two creep mechanisms. The model predicts a change in dominant mechanism from diffusional creep to GBS accommodated mainly by diffusion or by GBS itself as the amount of matter moved by diffusion decreases. Corresponding to this change, the model also predicts a spectrum of creep rate with the absolute value being dependent upon the extent of diffusion accommodation. Although experimental data exhibit scattering, most of them are in very good agreement with the prediction of the GBS model. Therefore, it is suggested that the Newtonian creep behavior with grain size dependence be induced by GBS rather than by conventional diffusion creep as believed before.

  16. Assessment of the deformation of the Bateman bipolar hip prosthesis inner bearing due to moisture absorption and creep.

    PubMed

    Lockie, K; Binns, M; Fisher, J; Jobbins, B

    1992-01-01

    The mechanism of inner bearing stiffness of bipolar hip prostheses has been investigated. The Ultra-high Molecular Weight Polyethylene (UHMWPE) component of the Bateman bipolar hip prosthesis has been subjected to a series of static and dynamic tests to assess water absorption and creep. Although deformation of the UHMWPE occurred, this did not produce an increased resistance to movement in the inner bearing. PMID:1572706

  17. Creeping Deformation by the Precise Leveling Survey at the central part of the Longitudinal valley fault, Southeast Taiwan

    NASA Astrophysics Data System (ADS)

    Matta, N.; Murase, M.; Ishiguro, S.; Ozawa, K.; Lin, J.; Chen, W.; Lin, C.

    2011-12-01

    We would like to know the distributed asperity for seismic hazard and forecast. It is closely related to slip distribution on the fault in interseismic. We focused on the accumulating process of the stress at the boundary between the creeping and the locking zone, to clear the behavior on the fault. The Longitudinal Valley Fault (LVF), 150 km long and NNE-SSW striking, passes through the eastern Taiwan, and represents the obvious surface expression of the collision boundary between the Philippine Sea plate and the Eurasian continental plate. Owing to such a high deformation rate, many earthquakes have occurred along the LVF. The 1951 earthquake sequence represents a good example. The southern of LVF segment is observed to be high speed creeping based on the creep meter and leveling survey etc. The northern of LVF segment is not observed to be creeping and are found huge earthquakes evidence by paleo-seismology study in the trench. Yuili fault is one of the active segments of the longitudinal valley faults, is located around the boundary between creeping and locking area. It is reverse fault with east dip. We established about 30km leveling route from Yuli to Changbin to detect the vertical deformation in detail. Murase et al. (2009, 2010, and 2011) established about 30 km densely leveling route from Yuli to Changbin to detect the vertical deformation across the LVF for two years. As a result, the vertical displacement is 1.7 cm in 200 m across the LVF and 2.7 cm in 1000 m, referred to the west end of our route. In addition, a synclinal deformation is detected on the hanging wall side of the fault. This result is caused by the geometry of and the slipping distribution on the fault. The deformation detected in the period from 2009 to 2010 denotes the same tendency and rate of that from 2008 to 2009. We compared to the airphotographs which are taken by Taiwanese government at different age (1978 and 2007). If the creeping on the fault has continued for 30 years, the

  18. The sliding mode control for different shapes and dimensions of IPMC on resisting its creep characteristics

    NASA Astrophysics Data System (ADS)

    Hao, Lina; Chen, Yang; Sun, Zhiyong

    2015-04-01

    Ionic polymer metal composite (IPMC) is a novel smart material which has been widely implemented in MEMS, biomimetic mechanical and electrical integrated system and micro operation system. While the IPMC with different shapes and dimensions has been implemented in many different types of biomechanical integrated systems, one of its inherent properties called creep characteristic is difficult to be handled, which limits the further application of different IPMCs in integrated systems. A promising control method called sliding mode control (SMC) is proposed to resist the creep characteristics in this paper. The SMC controller can regulate IPMC actuators with different shapes and dimensions effectively to resist the creep characteristics without changing parameters of the control system. Experiments of four different types of IPMC actuators were conducted on the semi-physical SMC experimental platform. All the experimental results confirm the feasibility of the SMC control approach on regulating the multi-IPMCs with different shapes and dimensions based integrated system.

  19. The effect of environment on the creep deformation of ultra-high purity nickel-chromium-iron alloys at 360 degrees Celcius

    NASA Astrophysics Data System (ADS)

    Paraventi, Denise Jean

    2000-10-01

    Steam generators in pressurized water nuclear power plants have experienced significant problems with intergranular stress corrosion cracking (IGSCC) on the inner diameter of steam generator tubing for over 25 years. In the course of research to understand IGSCC, it has been shown that creep deformation may play a significant role in the cracking of commercial Alloy 600 (Ni-16Cr-9Fe-0.03C). The primary water environment can cause decreases in creep resistance (i.e., faster creep rates, shorter time to failure, and higher creep strains). During corrosion under the conditions of interest, both hydrogen reduction and metal dissolution occur. One or both may contribute to the enhancement of creep. The purpose of this work was to isolate the mechanism by which the water environment causes the creep deformation to increase. Activation area and activation enthalpy for glide were measured in argon and primary water on high purity Ni-16Cr-9Fe alloys. The results indicated that the activation area was reduced by primary water, consistent with a hydrogen enhanced plasticity mechanism for enhanced creep. The stress dependence of creep was also examined in argon and primary water. The results indicated that the internal stress of the alloy is reduced by the primary water environment. Lower internal stress is consistent with both a hydrogen model as well as a vacancy-aided climb model for enhanced creep. To isolate the effect of hydrogen on the creep of the alloy, experiments were conducted in a dissociated hydrogen environment. The results indicated that hydrogen would only increase the steady state creep rate if present before loading of the samples. However, if the sample was already in steady state creep and hydrogen introduced, a transient in the creep strain was observed. The creep rate returned to the original steady state rate in a short time. The results indicate that while hydrogen does affect the steady state creep to an extent, hydrogen cannot completely account for

  20. Effects of cold rolling deformation on microstructure, hardness, and creep behavior of high nitrogen austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Sun, Shi-Cheng; Sun, Gui-Xun; Jiang, Zhong-Hao; Ji, Chang-Tao; Liu, Jia-An; Lian, Jian-She

    2014-02-01

    Effects of cold rolling deformation on the microstructure, hardness, and creep behavior of high nitrogen austenitic stainless steel (HNASS) are investigated. Microstructure characterization shows that 70% cold rolling deformation results in significant refinement of the microstructure of this steel, with its average twin thickness reducing from 6.4 μm to 14 nm. Nanoindentation tests at different strain rates demonstrate that the hardness of the steel with nano-scale twins (nt-HNASS) is about 2 times as high as that of steel with micro-scale twins (mt-HNASS). The hardness of nt-HNASS exhibits a pronounced strain rate dependence with a strain rate sensitivity (m value) of 0.0319, which is far higher than that of mt-HNASS (m = 0.0029). nt-HNASS shows more significant load plateaus and a higher creep rate than mt-HNASS. Analysis reveals that higher hardness and larger m value of nt-HNASS arise from stronger strain hardening role, which is caused by the higher storage rate of dislocations and the interactions between dislocations and high density twins. The more significant load plateaus and higher creep rates of nt-HNASS are due to the rapid relaxation of the dislocation structures generated during loading.

  1. Submarine creeping landslide deformation controlled by the presence of gas hydrates: The Tuaheni Landslide Complex, New Zealand

    NASA Astrophysics Data System (ADS)

    Gross, Felix; Mountjoy, Joshu; Crutchle, Garethy; Koch, Stephanie; Bialas, Jörg; Pecher, Ingo; Woelz, Susi; Dannowski, Anke; Carey, Jon; Micallef, Aaron; Böttner, Christoph; Huhn, Katrin; Krastel, Sebastian

    2016-04-01

    Methane hydrate occurrence is bound to a finite pressure/temperature window on continental slopes, known as the gas hydrate stability zone (GHSZ). Hydrates within sediment pore spaces and fractures are recognized to act like a cement, increasing shear strength and stabilizing slopes. However, recent studies show that over longer strain periods methane hydrates can undergo ductile deformation. This combination of short term strengthening and longer term ductile behavior is implicated in the development of slow creeping submarine landforms within the GHSZ. In order to study this phenomenon, a new high-resolution seismic 3D volume was acquired at the Tuaheni Landslide Complex (TLC) at the Hikurangi margin offshore the North Island of New Zealand. Parts of TLC have been interpreted as a slow moving landslide controlled by the gas hydrate system. Two hypotheses for its slow deformation related to the presence of methane hydrates have been proposed: i) Hydrofracturing, driven by gas pressure at the base of the GHSZ, allows pressurized fluids to ascend toward the seafloor, thereby weakening the shallow debris and promoting failure. ii) The mixture of methane hydrates and sediment results in a rheology that behaves in a ductile way under sustained loading, resulting in slow deformation comparable to that of terrestrial and extra-terrestrial rock glaciers. The 3D dataset reveals the distribution of gas and the extend of gas hydrate stability within the deformed debris, as well as deformation fabrics like tectonic-style faulting and a prominent basal décollement, known to be a critical element of terrestrial earth-flows and rock glaciers. Observations from 3D data indicate that the TLC represents the type example of a new submarine landform - an active creeping submarine landslide - which is influenced by the presence of gas hydrates. The morphology, internal structure and deformation of the landslide are comparable with terrestrial- and extra-terrestrial earth flows and

  2. Creep deformation of a fully lamellar gamma based titanium aluminide alloy

    SciTech Connect

    Herrouin, F.; Bowen, P.; Jones, I.P.

    1997-12-31

    A complex two phase {gamma}-TiAl alloy, Ti-47Al-1Cr-1Mn-2Ta-0.2Si (at.%) in a fully lamellar condition, has been creep tested at a stress of 200 MPa and a temperature of 700 C. This simulates the in-service operating conditions for several potential gas turbine aero engine applications where creep resistance is a design limiting material property. The results indicate that reduction in lamellae thickness and avoidance of feathery type microstructures contribute to improved creep resistance.

  3. Elevated Temperature Creep Deformation in Solid Solution <001> NiAL-3.6Ti Single Crystals

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Noebe, Ronald D.; Darolia, Ram

    2003-01-01

    The 1100 to 1500 K slow plastic strain rate compressive properties of <001> oriented NiAl-3.6Ti single crystals have been measured, and the results suggests that two deformation processes exist. While the intermediate temperature/faster strain rate mechanism is uncertain, plastic flow at elevated temperature/slower strain rates in NiAl-3.6Ti appears to be controlled by solute drag as described by the Cottrell-Jaswon solute drag model for gliding b = a(sub 0)<101> dislocations. While the calculated activation energy of deformation is much higher (approximately 480 kJ/mol) than the activation energy for diffusion (approximately 290 kJ/mol) used in the Cottrell-Jaswon creep model, a forced temperature compensated - power law fit using the activation energy for diffusion was able to adequately (greater than 90%) predict the observed creep properties. Thus we conclude that the rejection of a diffusion controlled mechanism can not be simply based on a large numerical difference between the activation energies for deformation and diffusion.

  4. The high temperature creep deformation of Si3N4-6Y2O3-2Al2O3

    NASA Technical Reports Server (NTRS)

    Todd, J. A.; Xu, Zhi-Yue

    1988-01-01

    The creep properties of silicon nitride containing 6 wt percent yttria and 2 wt percent alumina have been determined in the temperature range 1573 to 1673 K. The stress exponent, n, in the equation epsilon dot varies as sigma sup n, was determined to be 2.00 + or - 0.15 and the true activation energy was found to be 692 + or - 25 kJ/mol. Transmission electron microscopy studies showed that deformation occurred in the grain boundary glassy phase accompanied by microcrack formation and cavitation. The steady state creep results are consistent with a diffusion controlled creep mechanism involving nitrogen diffusion through the grain boundary glassy phase.

  5. Oscillation of structure characteristics in polycrystalline nickel during plastic deformation

    SciTech Connect

    Dvorovienko, N.A.; Gernov, S.A.; Sirenko, A.F. . Dept. of Solid State Physics); Hamana, D. . Research Unit of Materiale Physic)

    1993-07-01

    The variation of X-ray diffraction characteristics (breadth at half maximum intensity, integrated intensity, dislocation density and residual stresses), as a function of plastic deformation rate, which occurs by uniaxial tensile test, has been studied. At room temperature the observed oscillation of studied characteristics in deformed polycrystalline nickel is due to the deformation mechanism change. The latter can be a translational displacement due to dislocations or a rotational displacement due to disclination.

  6. Analysis of slip activity and heterogeneous deformation in tension and tension-creep of Ti-5Al-2.5Sn (wt %) using in-situ SEM experiments

    NASA Astrophysics Data System (ADS)

    Li, H.; Boehlert, C. J.; Bieler, T. R.; Crimp, M. A.

    2012-08-01

    The deformation behavior of a Ti-5Al-2.5Sn (wt %) near-α alloy was investigated during in-situ deformation inside a scanning electron microscope. Tensile experiments were performed at 296 K and 728 K (≈0.4 T m), while tensile-creep experiments were performed at 728 K and 763 K. Active deformation systems were identified using electron backscattered diffraction-based slip trace analysis. Both basal and prismatic slip systems were active during the tensile experiments. Basal slip was observed for grains clustered around high Schmid factor orientations, while prismatic slip exhibited less dependence on the crystallographic orientation. The tension-creep experiments revealed less slip but more development of grain boundary ledges than in the higher strain rate tensile experiments. Some of the grain boundary ledges evolved into grain boundary cracks, and grain boundaries oriented nearly perpendicular to the tensile axis formed ledges earlier in the deformation process. Grain boundaries with high misorientations also tended to form ledges earlier than those with lower misorientations. Most of the grain boundary cracks formed in association with grains displaying hard orientations, where the c-axis was nearly perpendicular to the tensile direction. For the tension-creep experiments, pronounced basal slip was observed in the lower-stress creep regime and the activity of prismatic slip increased with increasing creep stress and temperature.

  7. Madelung deformity and Madelung-type deformities: a review of the clinical and radiological characteristics.

    PubMed

    Ali, Sayed; Kaplan, Summer; Kaufman, Theresa; Fenerty, Sarah; Kozin, Scott; Zlotolow, Dan A

    2015-11-01

    Madelung deformity of the distal radius results from premature closure of the medial volar aspect of the distal radial physis, leading to increased volar tilt and increased inclination of the radial articular surface, triangulation of the carpus with proximal migration of the lunate and dorsal displacement of the distal ulna. The deformity is particularly common in Leri-Weill dyschondrosteosis, but it may also occur in isolation. True Madelung deformity can be differentiated from Madelung-type deformities by the presence of an anomalous radiolunate ligament (Vickers ligament). In this article, we will review the imaging characteristics of true Madelung deformity, including the common "distal radius" variant, the less common "entire radius" variant and "reverse" Madelung deformity. We will discuss the role of the Vickers ligament in disease pathogenesis and its use in differentiating true Madelung deformity from Madelung-type deformities arising from trauma or multiple hereditary exostoses. Surgical management of these patients will also be addressed. PMID:26135644

  8. Creep deformation and fracture behaviour of a nitrogen-bearing type 316 stainless steel weld metal

    NASA Astrophysics Data System (ADS)

    Sasikala, G.; Mathew, M. D.; Bhanu Sankara Rao, K.; Mannan, S. L.

    1999-08-01

    Creep properties of a nuclear grade type 316 stainless steel (SS) weld metal containing ˜0.08 wt% of nitrogen were studied at 873 and 923 K. These properties were compared with those of a type 316 SS weld metal without nitrogen. In general, the nitrogen-bearing weld metal exhibited better creep and rupture properties. The rupture strengths of the nitrogen-containing weld metal was ˜40% higher than that for the type 316 SS weld metal at both the temperatures. The steady-state (minimum) creep rates were up to two orders of magnitude lower for the nitrogen-containing weld metal compared to 316 SS weld metal. Rupture ductility of nitrogen-containing weld metal was lower at all the test conditions; the long-term ductility at 923 K was below 5%. The differences in creep behaviour of the two weld metals are discussed with respect to the influence of nitrogen on microstructural evolution in the two weld metals.

  9. High-temperature measurements of lattice parameters and internal stresses of a creep-deformed monocrystalline nickel-base superalloy

    NASA Astrophysics Data System (ADS)

    Biermann, Horst; Strehler, Marcus; Mughrabi, Haël

    1996-04-01

    High-temperature X-ray line profile measurements were performed to maximal temperatures of 1050 °C on samples of the nickel-base superalloy SRR 99. The samples with rod axes near the [001] direction were investigated in the initially undeformed state and after creep deformation at different temperatures and stresses. For the measurements of the (002) and (020) line profiles, a special X-ray double crystal diffractometer with negligible line broadening was used which was equipped with a high-temperature vacuum chamber. The line profiles were evaluated for the lattice parameters of the matrix phase γ and the precipitated γ' phase and for values of the lattice mismatch parallel and perpendicular to the stress axis, respectively, which were found to be different. Elastic, tetragonal distortions of the phases γ and γ' could be determined between room temperature and about 900 °C. These distortions are thermally induced due to the different thermal expansion coefficients of the two phases and deformation induced due to interfacial dislocation networks which were built up during deformation. At the high temperatures of the X-ray measurements, at least partial recovery of the deformation-induced internal stresses occurred, depending on the temperature of the X-ray measurements. The results are discussed and compared with data obtained by complementary techniques.

  10. Examination of the distribution of the tensile deformation systems in tension and tension-creep of Ti-6Al-4V (wt.%) at 296 K and 728 K

    NASA Astrophysics Data System (ADS)

    Li, H.; Boehlert, C. J.; Bieler, T. R.; Crimp, M. A.

    2015-03-01

    The deformation behaviour of an α + β Ti-6Al-4V (wt.%) alloy was investigated during in situ deformation inside a scanning electron microscopy (SEM). Tensile experiments were performed at 296 and 728 K (~0.4Tm), while a tensile-creep experiment was performed at 728 K and 310 MPa (σ/σys = 0.74). The active deformation systems were identified using electron backscattered diffraction-based slip-trace analysis and SEM images of the specimen surface. The distribution of the active deformation systems varied as a function of temperature. Basal slip deformation played a major role in the tensile deformation behaviour, and the relative activity of basal slip increased with increasing temperature. For the 296 K tension deformation, basal slip was less active than prismatic slip, whereas this was reversed at 728 K. Twinning was observed in both the 296 and 728 K tension experiments; however, no more than 4% of the total deformation systems observed was twins. The tension-creep experiment revealed no slip traces, however grain boundary ledge formation was observed, suggesting that grain boundary sliding was an active deformation mechanism. The results of this work were compared with those from previous studies on commercially pure Ti, Ti-5Al-2.5Sn (wt.%) and Ti-8Al-1Mo-1V (wt.%), and the effects of alloying on the deformation behaviour are discussed. The relative amount of basal slip activity increased with increasing Al content.

  11. Creep Measurement Video Extensometer

    NASA Technical Reports Server (NTRS)

    Jaster, Mark; Vickerman, Mary; Padula, Santo, II; Juhas, John

    2011-01-01

    Understanding material behavior under load is critical to the efficient and accurate design of advanced aircraft and spacecraft. Technologies such as the one disclosed here allow accurate creep measurements to be taken automatically, reducing error. The goal was to develop a non-contact, automated system capable of capturing images that could subsequently be processed to obtain the strain characteristics of these materials during deformation, while maintaining adequate resolution to capture the true deformation response of the material. The measurement system comprises a high-resolution digital camera, computer, and software that work collectively to interpret the image.

  12. Steady-state creep of bent reinforced metal-composite plates with consideration of their reduced resistance to transverse shear. 1. Deformation model

    NASA Astrophysics Data System (ADS)

    Yankovskii, A. P.

    2014-05-01

    The problem of deformation of reinforced metal-composite plates is formulated in rectangular Cartesian coordinates using the second version of Timoshenko theory and taking into account the reduced transverse shear resistance of the plates under steady-state creep conditions. A similar model problem of axisymmetric bending of reinforced plates is considered in polar coordinates.

  13. Evaluation of Permanent Deformation of CRM-Reinforced SMA and Its Correlation with Dynamic Stiffness and Dynamic Creep

    PubMed Central

    Mashaan, Nuha Salim; Karim, Mohamed Rehan

    2013-01-01

    Today, rapid economic and industrial growth generates increasing amounts of waste materials such as waste tyre rubber. Attempts to inspire a green technology which is more environmentally friendly that can produce economic value are a major consideration in the utilization of waste materials. The aim of this study is to evaluate the effect of waste tyre rubber (crumb rubber modifier (CRM)), in stone mastic asphalt (SMA 20) performance. The virgin bitumen (80/100) penetration grade was used, modified with crumb rubber at four different modification levels, namely, 6%, 12%, 16%, and 20% by weight of the bitumen. The testing undertaken on the asphalt mix comprises the indirect tensile (dynamic stiffness), dynamic creep, and wheel tracking tests. By the experimentation, the appropriate amount of CRM was found to be 16% by weight of bitumen. The results show that the addition of CRM into the mixture has an obvious significant effect on the performance properties of SMA which could improve the mixture's resistance against permanent deformation. Further, higher correlation coefficient was obtained between the rut depth and permanent strain as compared to resilient modulus; thus dynamic creep test might be a more reliable test in evaluating the rut resistance of asphalt mixture. PMID:24302883

  14. Evaluation of permanent deformation of CRM-reinforced SMA and its correlation with dynamic stiffness and dynamic creep.

    PubMed

    Mashaan, Nuha Salim; Karim, Mohamed Rehan

    2013-01-01

    Today, rapid economic and industrial growth generates increasing amounts of waste materials such as waste tyre rubber. Attempts to inspire a green technology which is more environmentally friendly that can produce economic value are a major consideration in the utilization of waste materials. The aim of this study is to evaluate the effect of waste tyre rubber (crumb rubber modifier (CRM)), in stone mastic asphalt (SMA 20) performance. The virgin bitumen (80/100) penetration grade was used, modified with crumb rubber at four different modification levels, namely, 6%, 12%, 16%, and 20% by weight of the bitumen. The testing undertaken on the asphalt mix comprises the indirect tensile (dynamic stiffness), dynamic creep, and wheel tracking tests. By the experimentation, the appropriate amount of CRM was found to be 16% by weight of bitumen. The results show that the addition of CRM into the mixture has an obvious significant effect on the performance properties of SMA which could improve the mixture's resistance against permanent deformation. Further, higher correlation coefficient was obtained between the rut depth and permanent strain as compared to resilient modulus; thus dynamic creep test might be a more reliable test in evaluating the rut resistance of asphalt mixture. PMID:24302883

  15. On The Creep Behavior and Deformation Mechanisms Found in an Advanced Polycrystalline Nickel-Base Superalloy at High Temperatures

    NASA Astrophysics Data System (ADS)

    Deutchman, Hallee Zox

    Polycrystalline Ni-base superalloys are used as turbine disks in the hot section in jet engines, placing them in a high temperature and stress environment. As operating temperatures increase in search of better fuel efficiency, it becomes important to understand how these higher temperatures are affecting mechanical behavior and active deformation mechanisms in the substructure. Not only are operating temperatures increasing, but there is a drive to design next generation alloys in shorter time periods using predictive modeling capabilities. This dissertation focuses on mechanical behavior and active deformation mechanisms found in two different advanced polycrystalline alloy systems, information which will then be used to build advanced predictive models to design the next generation of alloys. The first part of this dissertation discusses the creep behavior and identifying active deformation mechanisms in an advanced polycrystalline Ni-based superalloy (ME3) that is currently in operation, but at higher temperatures and stresses than are experienced in current engines. Monotonic creep tests were run at 700°C and between 655-793MPa at 34MPa increments, on two microstructures (called M1 and M2) produced by different heat treatments. All tests were crept to 0.5% plastic strain. Transient temperature and transient stress tests were used determine activation energy and stress exponents of the M1 microstructure. Constant strain rate tests (at 10-4s-1) were performed on both microstructures as well. Following creep testing, both M1 and M2 microstructures were fully characterized using Scanning Electron Microscopy (SEM) for basic microstructure information, and Scanning Transmission Electron Microscopy (STEM) to determine active deformation mechanism. It was found that in the M1 microstructure, reorder mediated activity (such as discontinuous faulting and microtwinning) is dominant at low stresses (655-724 MPa). Dislocations in the gamma matrix, and overall planar

  16. Creep deformation of grain boundary in a highly crystalline SiC fibre.

    PubMed

    Shibayama, Tamaki; Yoshida, Yutaka; Yano, Yasuhide; Takahashi, Heishichiro

    2003-01-01

    Silicon carbide (SiC) matrix composites reinforced by SiC fibres (SiC/SiC composites) are currently being considered as alternative materials in high Ni alloys for high-temperature applications, such as aerospace components, gas-turbine energy-conversion systems and nuclear fusion reactors, because of their high specific strength and fracture toughness at elevated temperatures compared with monolithic SiC ceramics. It is important to evaluate the creep properties of SiC fibres under tensile loading in order to determine their usefulness as structural components. However, it would be hard to evaluate creep properties by monoaxial tensile properties when we have little knowledge on the microstructure of crept specimens, especially at the grain boundary. Recently, a simple fibre bend stress relaxation (BSR) test was introduced by Morscher and DiCarlo to address this problem. Interpretation of the fracture mechanism at the grain boundary is also essential to allow improvement of the mechanical properties. In this paper, effects of stress applied by BSR test on microstructural evolution in advanced SiC fibres, such as Tyranno-SA including small amounts of Al, are described and discussed along with the results of microstructure analysis on an atomic scale by using advanced microscopy. PMID:12741492

  17. Creep deformation and rupture behavior of 2.25Cr-1Mo steel weldments and its constituents (base metal, weld metal and simulated heat affected zones)

    SciTech Connect

    Laha, K.; Chandravathi, K.S.; Rao, K.B.S.; Mannan, S.L.

    1995-12-31

    Microstructure across a weldment base metal through transformed heat-affected zone (HAZ) to cast weld metal. HAZ of 2.25Cr-1Mo weldment consists of coarse-grain bainite, fine-grain bainite and intercritical region. These HAZ microstructures were simulated by isothermal heat-treatments. Creep tests were carried out on base metal, weld metal, weldment and the simulated HAZ structures. Creep deformation and fracture behavior of 2.25Cr-1Mo weldments has been assessed based on the properties of its constituents. Coarse-grain bainite with low ductility and intercritical structure with low strength are the critical components of HAZ determining performance of the weldments.

  18. Creep deformation and buttressing capacity of damaged ice shelves: theory and application to Larsen C ice shelf

    NASA Astrophysics Data System (ADS)

    Borstad, C. P.; Rignot, E.; Mouginot, J.; Schodlok, M. P.

    2013-07-01

    Around the perimeter of Antarctica, much of the ice sheet discharges to the ocean through floating ice shelves. The buttressing provided by ice shelves is critical for modulating the flux of ice into the ocean, and the presently observed thinning of ice shelves is believed to be reducing their buttressing capacity and contributing to the acceleration and thinning of the grounded ice sheet. However, relatively little attention has been paid to the role that fractures play in the flow and stability of ice shelves and their capacity to buttress the flow of grounded ice. Here, we develop an analytical framework for describing the role that fractures play in the creep deformation and buttressing capacity of ice shelves. We apply principles of continuum damage mechanics to derive a new analytical relation for the creep of an ice shelf as a function of ice thickness, temperature, material properties, resistive backstress and damage. By combining this analytical theory with an inverse method solution for the spatial rheology of an ice shelf, both backstress and damage can be calculated. We demonstrate the applicability of this new theory using satellite remote sensing and Operation IceBridge data for the Larsen C ice shelf, finding damage associated with known crevasses and rifts. We find that increasing thickness of mélange between rift flanks correlates with decreasing damage, with some rifts deforming coherently with the ice shelf as if completely healed. We quantify the stabilizing backstress caused by ice rises and lateral confinement, finding high backstress associated with two ice rises that likely stabilize the ice front in its current configuration. Though overall the ice shelf appears stable at present, the ice in contact with the Bawden ice rise is weakened by fractures, and additional damage or thinning in this area could portend significant change for the shelf. Using this new approach, field and remote sensing data can be utilized to monitor the structural

  19. Creep deformation and buttressing capacity of damaged ice shelves: theory and application to Larsen C ice shelf

    NASA Astrophysics Data System (ADS)

    Borstad, C. P.; Rignot, E.; Mouginot, J.; Schodlok, M. P.

    2013-12-01

    Around the perimeter of Antarctica, much of the ice sheet discharges to the ocean through floating ice shelves. The buttressing provided by ice shelves is critical for modulating the flux of ice into the ocean, and the presently observed thinning of ice shelves is believed to be reducing their buttressing capacity and contributing to the acceleration and thinning of the grounded ice sheet. However, relatively little attention has been paid to the role that fractures play in the ability of ice shelves to sustain and transmit buttressing stresses. Here, we present a new framework for quantifying the role that fractures play in the creep deformation and buttressing capacity of ice shelves. We apply principles of continuum damage mechanics to derive a new analytical relation for the creep of an ice shelf that accounts for the softening influence of fractures on longitudinal deformation using a state damage variable. We use this new analytical relation, combined with a temperature calculation for the ice, to partition an inverse method solution for ice shelf rigidity into independent solutions for softening damage and stabilizing backstress. Using this new approach, field and remote sensing data can be utilized to monitor the structural integrity of ice shelves, their ability to buttress the flow of ice at the grounding line, and thus their indirect contribution to ice sheet mass balance and global sea level. We apply this technique to the Larsen C ice shelf using remote sensing and Operation IceBridge data, finding damage in areas with known crevasses and rifts. Backstress is highest near the grounding line and upstream of ice rises, in agreement with patterns observed on other ice shelves. The ice in contact with the Bawden ice rise is weakened by fractures, and additional damage or thinning in this area could diminish the backstress transmitted upstream. We model the consequences for the ice shelf if it loses contact with this small ice rise, finding that flow speeds

  20. Effect of boron on creep characteristics in 9Cr-1.5Mo alloys

    NASA Astrophysics Data System (ADS)

    Kim, Bumjoon; Yun, Haksu; Lee, Dongbok; Lim, Byeongsoo

    2009-01-01

    For thick-section components such as headers and pipes of the power plants, high creep rupture strength and oxidation resistance are required. It is known that the addition of boron can improve the creep strength and oxidation resistance through the stabilization of M23C6 carbides in the vicinity of prior austenite grain boundaries. In this study, the effect of boron addition with the range of 0.0033~0.0133 wt% on the creep behavior of 9Cr-1.5Mo steel was investigated. Small punch creep tests were carried out to investigate the effect of boron addition on creep properties. Microstructure observation was performed to analyze the effect of boron addition on creep strength and rupture life. Also, the relationship between the minimum creep rate and the amount of boron addition were analyzed. The addition of boron is beneficial in lowering the steady-state creep rate.

  1. Evidence of post-seismic creep type deformations derived by tilt and acoustic emission monitoring of mining induced seismic events

    NASA Astrophysics Data System (ADS)

    Milev, Alexander; Share, Pieter-Ewald; Naoi, Makoto; Durrheim, Raymond; Yabe, Yasuo; Ogasawara, Hiroshi; Nakatani, Masao

    2015-04-01

    In this study we try to understand pre- and post-failure rock behavior associated with mining induced seismic events. This involves underground installation of various high precision instruments, including geophones, acoustic emission sensors, tilt- and strain-meters at a number of sites in deep level South African gold mines. The rate of tilt, strain and the seismic ground motion were analysed in order to understand the coseismic and aseismic deformation of the rocks. A good correspondence between the coseismic and the aseismic deformations was found. The rate of coseismic and aseismic tilt, as well as seismicity recorded by the mine seismic network, are approximately constant until the daily blasting time, which takes place from about 19:30 until shortly before 21:00. During the blasting time and the subsequent seismic events, the coseismic tilt and strain shows a rapid increase. Much of the aseismic deformation, however, occurs independently of the seismic events and blasting. In an attempt to distinguish between the different mechanisms of tilting two types of events were recognized. The "fast" seismic events characterized with sharp increase of the tilt during the seismic rupture and "slow" seismic events characterized by creep type post seismic deformations. Tilt behaviour before and after a seismic event was also analysed. The fact that no recognizable aftertilt was observed for more of the "fast" seismic events means that there is no gradual release of stress and an associated continuous strain rate change afterwards. It can therefore be concluded that a large seismic event causes a rapid change in the state of stress rather than a gradual change in the strain rate During the monitoring period a seismic event with MW 2.2 occurred in the vicinity of the instrumented site. This event was recorded by both the CSIR integrated monitoring system and JAGUARS acoustic emission network. More than 21,000 AE aftershocks were located in the first 150 hours after the

  2. Implications of Microstructural Studies of the SAFOD Gouge for the Strength and Deformation Mechanisms in the Creeping Segment of the San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Hadizadeh, J.; Gratier, J. L.; Mittempergher, S.; Renard, F.; Richard, J.; di Toro, G.; Babaie, H. A.

    2010-12-01

    The San Andreas Fault zone (SAF) in the vicinity of the San Andreas Fault Observatory at Depth (SAFOD)in central California is characterized by an average 21 mm/year aseismic creep and strain release through repeating M<3 earthquakes. Seismic inversion studies indicate that the ruptures occur on clusters of stationary patches making up 1% or less of the total fault surface area. The existence of these so-called asperity patches, although not critical in determining the fault strength, suggests interaction of different deformation mechanisms. What are the deformation mechanisms, and how do the mechanisms couple and factor into the current strength models for the SAF? The SAFOD provides core samples and geophysical data including cores from two shear zones where the main borehole casing is deforming. The studies so far show a weak fault zone with about 200m of low-permeability damage zone without anomalous temperature or high fluid pressure (Zoback et al. EOS 2010). To answer the above questions, we studied core samples and thin sections ranging in measured depths (MD) from 3059m to 3991m including gouge from borehole casing deformation zones. The methods of study included high resolution scanning and transmission electron microscopy, cathodoluminescence imaging, X-ray fluorescence mapping, and energy dispersive X-ray spectroscopy. The microstructural and analytical data suggest that deformation is by a coupling of cataclastic flow and pressure solution accompanied by widespread alteration of feldspar to clay minerals and other neomineralizations. The clay contents of the gouge and streaks of serpentinite are not uniformly distributed, but weakness of the creeping segment is likely to be due to intrinsically low frictional strength of the fault material. This conclusion, which is based on the overall ratio of clay/non-clay constituents and the presence of talc in the actively deforming zones, is consistent with the 0.3-0.45 coefficient of friction for the drill

  3. Nanoindentation Creep Behavior of an Al0.3CoCrFeNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Lijun; Yu, Pengfei; Cheng, Hu; Zhang, Huan; Diao, Haoyan; Shi, Yunzhu; Chen, Bilin; Chen, Peiyong; Feng, Rui; Bai, Jie; Jing, Qin; Ma, Mingzhen; Liaw, P. K.; Li, Gong; Liu, Riping

    2016-03-01

    Nanoindentation creep behavior was studied on a coarse-grained Al0.3CoCrFeNi high-entropy alloy with a single face-centered cubic structure. The effects of the indentation size and loading rate on creep behavior were investigated. The experimental results show that the hardness, creep depth, creep strain rate, and stress exponent are all dependent on the holding load and loading rate. The creep behavior shows a remarkable indentation size effect at different maximum indentation loads. The dominant creep mechanism is dislocation creep at high indentation loads and self-diffusion at low indentation loads. An obvious loading rate sensitivity of creep behavior is found under different loading rates for the alloy. A high loading rate can lead to a high strain gradient, and numerous dislocations emerge and entangle together. Then during the holding time, a large creep deformation characteristic with a high stress exponent will happen.

  4. Compilation of Surface Creep on California Faults and Comparison of WGCEP 2007 Deformation Model to Pacific-North American Plate Motion

    USGS Publications Warehouse

    Wisely, Beth A.; Schmidt, David A.; Weldon, Ray J., II

    2008-01-01

    This Appendix contains 3 sections that 1) documents published observations of surface creep on California faults, 2) constructs line integrals across the WG-07 deformation model to compare to the Pacific ? North America plate motion, and 3) constructs strain tensors of volumes across the WG-07 deformation model to compare to the Pacific ? North America plate motion. Observation of creep on faults is a critical part of our earthquake rupture model because if a fault is observed to creep the moment released as earthquakes is reduced from what would be inferred directly from the fault?s slip rate. There is considerable debate about how representative creep measured at the surface during a short time period is of the whole fault surface through the entire seismic cycle (e.g. Hudnut and Clark, 1989). Observationally, it is clear that the amount of creep varies spatially and temporally on a fault. However, from a practical point of view a single creep rate is associated with a fault section and the reduction in seismic moment generated by the fault is accommodated in seismic hazard models by reducing the surface area that generates earthquakes or by reducing the slip rate that is converted into seismic energy. WG-07 decided to follow the practice of past Working Groups and the National Seismic Hazard Map and used creep rate (where it was judged to be interseismic, see Table P1) to reduce the area of the fault surface that generates seismic events. In addition to following past practice, this decision allowed the Working Group to use a reduction of slip rate as a separate factor to accommodate aftershocks, post seismic slip, possible aseismic permanent deformation along fault zones and other processes that are inferred to affect the entire surface area of a fault, and thus are better modeled as a reduction in slip rate. C-zones are also handled by a reduction in slip rate, because they are inferred to include regions of widely distributed shear that is not completely

  5. Modeling creep deformation of a two-phase TiAl/Ti[sub 3]Al alloy with a lamellar microstructure

    SciTech Connect

    Bartholomeusz, M.F. ); Wert, J.A. . Dept. of Materials Science and Engineering)

    1994-10-01

    A two-phase TiAl/Ti[sub 3]Al alloy with a lamellar microstructure has been previously shown to exhibit a lower minimum creep rate than the minimum creep rates of the constituent TiAl and Ti[sub 3]Al single-phase alloys. Fiducial-line experiments described in the present article demonstrate that the creep rates of the constituent phases within the two-phase TiAl/Ti[sub 3]Al lamellar alloy tested in compression are more than an order of magnitude lower than the creep rates of single-phase TiAl and Ti[sub 3]Al alloys tested in compression at the same stress and temperature. Additionally, the fiducial-line experiments show that no interfacial sliding of the phases in the TiAl/Ti[sub 3]Al lamellar alloy occurs during creep. The lower creep rate of the lamellar alloy is attributed to enhanced hardening of the constituent phases within the lamellar microstructure. A composite-strength model has been formulated to predict the creep rate of the lamellar alloy, taking into account the lower creep rates of the constituent phases within the lamellar microstructure. Application of the model yields a very good correlation between the predicted an experimentally observed minimum creep rates over moderate stress and temperature ranges.

  6. Modeling creep deformation of a two-phase TiAI/Ti3Al alloy with a lamellar microstructure

    NASA Astrophysics Data System (ADS)

    Bartholomeusz, Michael F.; Wert, John A.

    1994-10-01

    A two-phase TiAl/Ti3Al alloy with a lamellar microstructure has been previously shown to exhibit a lower minimum creep rate than the minimum creep rates of the constituent TiAl and Ti3Al single-phase alloys. Fiducial-line experiments described in the present article demonstrate that the creep rates of the constituent phases within the two-phase TiAl/Ti3Al lamellar alloy tested in compression are more than an order of magnitude lower than the creep rates of single-phase TiAl and Ti3Al alloys tested in compression at the same stress and temperature. Additionally, the fiducial-line experiments show that no interfacial sliding of the phases in the TiAl/Ti3Al lamellar alloy occurs during creep. The lower creep rate of the lamellar alloy is attributed to enhanced hardening of the constituent phases within the lamellar microstructure. A composite-strength model has been formulated to predict the creep rate of the lamellar alloy, taking into account the lower creep rates of the constituent phases within the lamellar micro-structure. Application of the model yields a very good correlation between predicted and experimentally observed minimum creep rates over moderate stress and temperature ranges.

  7. Interseismic deformation and creep along the central section of the North Anatolian Fault (Turkey): InSAR observations and implications for rate-and-state friction properties

    NASA Astrophysics Data System (ADS)

    Kaneko, Y.; Fialko, Y.; Sandwell, D. T.; Tong, X.; Furuya, M.

    2013-01-01

    AbstractWe present high-resolution measurements of interseismic <span class="hlt">deformation</span> along the central section of the North Anatolian Fault (NAF) in Turkey using interferometric synthetic aperture radar data from the Advanced Land Observing Satellite and Envisat missions. We generated maps of satellite line-of-sight velocity using five ascending Advanced Land Observing Satellite tracks and one descending Envisat track covering the NAF between 31.2°E and 34.3°E. The line-of-sight velocity reveals discontinuities of up to ˜5 mm/yr across the Ismetpasa segment of the NAF, implying surface <span class="hlt">creep</span> at a rate of ˜9 mm/yr; this is a large fraction of the inferred slip rate of the NAF (21-25 mm/yr). The lateral extent of significant surface <span class="hlt">creep</span> is about 75 km. We model the inferred surface velocity and shallow fault <span class="hlt">creep</span> using numerical simulations of spontaneous earthquake sequences that incorporate laboratory-derived rate and state friction. Our results indicate that frictional behavior in the Ismetpasa segment is velocity strengthening at shallow depths and transitions to velocity weakening at a depth of 3-6 km. The inferred depth extent of shallow fault <span class="hlt">creep</span> is 5.5-7 km, suggesting that the deeper locked portion of the partially <span class="hlt">creeping</span> segment is characterized by a higher stressing rate, smaller events, and shorter recurrence interval. We also reproduce surface velocity in a locked segment of the NAF by fault models with velocity-weakening conditions at shallow depth. Our results imply that frictional behavior in a shallow portion of major active faults with little or no shallow <span class="hlt">creep</span> is mostly velocity weakening.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006JSG....28..902W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006JSG....28..902W"><span id="translatedtitle">Quartz veins <span class="hlt">deformed</span> by diffusion <span class="hlt">creep</span>-accommodated grain boundary sliding during a transient, high strain-rate event in the Southern Alps, New Zealand</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wightman, Ruth H.; Prior, David J.; Little, Timothy A.</p> <p>2006-05-01</p> <p>The crystallographic preferred orientations (CPOs) and microstructures of <span class="hlt">deformed</span> quartz veins were measured for four samples in the hanging-wall of the Alpine Fault in the Southern Alps, New Zealand. Their <span class="hlt">deformation</span> and exhumation has occurred since 4 Ma. The quartz veins have been ductilely sheared to finite shear-strains of 5-15 in late Cenozoic shear zones at 450±50 °C, 310±90 MPa and strain-rates between 2×10 -11 and 2×10 -9 s -1. The sheared veins have a polygonal microstructure with few subgrains and an average grain-size of ˜100 μm. The CPO of the veins is random to very weak within the shear zones. We suggest that dislocation <span class="hlt">creep</span> accommodated initial shear <span class="hlt">deformation</span>, at high stresses and strain-rates. The <span class="hlt">deformation</span> must have created a strong CPO and concomitant dynamic recrystallization reduced the grain-size significantly. Dissipation of stresses during initial <span class="hlt">deformation</span> lead to a stress and strain-rate drop required for a switch to diffusion <span class="hlt">creep</span>-accommodated grain boundary sliding (GBS). Continued shearing accommodated by GBS destroyed the CPO. Post-<span class="hlt">deformational</span> grain growth gave rise to a final polygonal microstructure with a similar grain size in veins and in the wall rocks. Analysis of existing experimental data suggest that this sequence of events is possible in the time available. Rates of all processes may have been enhanced by the presence of a water-rich fluid within the shear zones. These observations of naturally <span class="hlt">deformed</span> rocks provide a model for the processes that may occur during short-lived <span class="hlt">deformation</span> at transiently-high stresses at mid-crustal depths or deeper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996MMTA...27..127W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996MMTA...27..127W"><span id="translatedtitle">Effect of <span class="hlt">creep</span> strain on microstructural stability and <span class="hlt">creep</span> resistance of a TiAi/Ti3ai lamellar alloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wert, J. A.; Bartholomeusz, M. F.</p> <p>1996-01-01</p> <p><span class="hlt">Creep</span> of a TiAl/Ti3Al alloy with a lamellar microstructure causes progressive spheroidization of the lamellar microstructure. Microstructural observations reveal that <span class="hlt">deformation</span>-induced spheroidization (DIS) occurs by <span class="hlt">deformation</span> and fragmentation of lamellae in localized shear zones at interpacket boundaries and within lamellar packets. <span class="hlt">Deformation</span>-induced spheroidization substantially increases the interphase interfacial area per unit volume, demonstrating that DIS is not a coarsening process driven by reduction of interfacial energy per unit volume. <span class="hlt">Creep</span> experiments reveal that DIS increases the minimum <span class="hlt">creep</span> rate (ɛmin) during <span class="hlt">creep</span> at constant stress and temperature; the activation energy ( Q c ) and stress exponent ( n) for <span class="hlt">creep</span> are both reduced as a result of DIS. Values of n and Q c for the lamellar microstructure are typical of a dislocation <span class="hlt">creep</span> mechanism, while estimated values of n and Q c for the completely spheroidized microstructure are <span class="hlt">characteristic</span> of a diffusional <span class="hlt">creep</span> mechanism. The increase in (ɛmin) associated with DIS is thus attributed primarily to a change of <span class="hlt">creep</span> mechanism resulting from microstructural refinement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014PhDT........16G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014PhDT........16G&link_type=ABSTRACT"><span id="translatedtitle">In-situ scanning electron microscopy (sem) observations of the tensile and tensile-<span class="hlt">creep</span> <span class="hlt">deformation</span> of Titanium-8Aluminum-1mo-1v (wt.%) alloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghosh Dastidar, Indraroop</p> <p></p> <p>Titanium (Ti) and titanium alloys (Ti alloys) are attractive for structural applications, such as in the aerospace and automotive industries due to their high specific strength, excellent corrosion resistance and good ability to withstand elevated temperatures. To develop Ti alloys with better mechanical properties, it is necessary to comprehend the <span class="hlt">deformation</span> behavior of available Ti alloys. Previous studies performed by another graduate student, Dr. Hongmei Li, involved investigation of the <span class="hlt">deformation</span> behavior of commercially pure (CP) Ti, Ti-5Al-2.5Sn (wt.%), Ti-3Al-2.5V (wt.%) and Ti-6Al-4V (wt.%) alloys. The current thesis focused on investigating the <span class="hlt">deformation</span> behavior of Ti-8Al-1Mo-1V (wt.%). In-situ tensile and tensile-<span class="hlt">creep</span> experiments were performed at temperatures ranging from room temperature (RT) to 650OC inside a scanning electron microscope (SEM), which allowed for the observation of the surface <span class="hlt">deformation</span> evolution. Electron Back Scattered Diffraction (EBSD) was used to identify the distribution of the active <span class="hlt">deformation</span> systems. In this thesis efforts were made to characterize the various <span class="hlt">deformation</span> modes of the Ti-8Al-1Mo-1V (wt.%) alloy as a function of the testing conditions (stress and temperature). It was observed that prismatic slip made up the majority of the observed slip systems during the RT tensile <span class="hlt">deformation</span>, while basal and prismatic slip were almost equally active during the 455OC tensile <span class="hlt">deformation</span>. Grain boundary ledges were observed during the elevated temperature tensile-<span class="hlt">creep</span> <span class="hlt">deformation</span> and from this observation it was suggested that grain boundary sliding was an active <span class="hlt">deformation</span> mode. This work also involved estimating the Critical Resolved Shear Stress (CRSS) ratios of the alpha-phase <span class="hlt">deformation</span> modes. The CRSS ratios were compared with the CRSS ratios of CP Ti and other Ti alloys. Overall, this work was intended to add more data to the scientific literature of Ti alloys in order to better comprehend their</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T31C2607R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T31C2607R"><span id="translatedtitle">Time and space evolution of an active <span class="hlt">creeping</span> zone: competition between brittle and ductile <span class="hlt">deformations</span>, new insights from microstructure studies of SAFOD (San Andreas Fault Observatory at Depth) samples</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Richard, J.; Gratier, J.; Doan, M.; Renard, F.; Boullier, A.</p> <p>2012-12-01</p> <p><span class="hlt">Creep</span> processes can relax an important part of the tectonic stresses in active faults, either by permanent steady-state <span class="hlt">creep</span> or by episodic post-seismic <span class="hlt">creep</span>. Here, our goal is to better constrain the micro-physical parameters that control this transition between seismic and aseismic behavior, both in time and in space. We present new results from microstructural studies on natural samples collected from the SAFOD (San Andreas Fault Observatory at Depth) drilling project, located on the Parkfield segment of the San Andreas Fault (SAF). Seven samples were collected from the main active <span class="hlt">creeping</span> zone: the Central <span class="hlt">Deforming</span> Zone at 3301-3303m depth. We performed chemical and mineralogical analyses and microscope observations on twenty thin sections cut from those samples. In a previous study (Gratier et al., Geology, 2011), we have already shown that pressure solution <span class="hlt">creep</span> is an active <span class="hlt">deformation</span> process in the SAF. We propose a model of microstructural evolution to characterize in which conditions pressure solution <span class="hlt">creep</span> is efficient enough to relax stress and to prevent the nucleation of moderate to large earthquakes. We show that two crucial parameters may accelerate pressure solution: the presence of phyllosilicates and the degree of rock fracturing. The initial structure and composition of the rocks may explain why pressure solution <span class="hlt">creep</span> is efficient or not. Moreover, both the content of phyllosilicates and the degree of fracture may evolve with time at various scales during the seismic cycle: - During interseismic periods (years to millennia): fracturing activates postseismic <span class="hlt">creep</span>. However, the progressive healing of the fracture annihilates this effect. Meanwhile, growth of phyllosilicate minerals, associated with postseismic fluid flow may also activate the <span class="hlt">creep</span> rate. - During much longer geological periods (hundred thousands to millions of years), the composition of gouge material <span class="hlt">deformed</span> by pressure solution evolves by the passive concentration of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRB..121.3278K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRB..121.3278K"><span id="translatedtitle">Dislocation <span class="hlt">creep</span> of dry quartz</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kilian, Rüdiger; Heilbronner, Renée.; Holyoke, Caleb W.; Kronenberg, Andreas K.; Stünitz, Holger</p> <p>2016-05-01</p> <p>Small-scale shear zones within the Permian Truzzo meta-granite developed during the Alpine orogeny at amphibolite facies conditions. In these shear zones magmatic quartz <span class="hlt">deformed</span> by dislocation <span class="hlt">creep</span> and recrystallized dynamically by grain boundary migration with minor subgrain rotation recrystallization to a grain size of around 250-750 µm, consistent with flow at low differential stresses. Fourier transform infrared (FTIR) spectroscopy reveals very low water contents in the interior of recrystallized grains (in the form of discrete OH peaks, ~20 H/106Si and very little broad band absorption, <100 H/106Si). The spectral <span class="hlt">characteristics</span> are comparable to those of dry Brazil quartz. In FTIR spectra, magmatic quartz grains show a broad absorption band related with high water concentrations only in those areas where fluid inclusions are present while other areas are dry. Drainage of fluid inclusions and synkinematic growth of hydrous minerals indicates that a hydrous fluid has been available during <span class="hlt">deformation</span>. Loss of intragranular water during grain boundary migration recrystallization did not result in a microstructure indicative of hardening. These FTIR measurements provide the first evidence that quartz with extremely low intragranular water contents can <span class="hlt">deform</span> in nature by dislocation <span class="hlt">creep</span> at low differential stresses. Low intragranular water contents in naturally <span class="hlt">deformed</span> quartz may not be necessarily indicative of a high strength, and the results are contrary to implications taken from <span class="hlt">deformation</span> experiments where very high water contents are required to allow dislocation <span class="hlt">creep</span> in quartz. It is suggested that dislocation <span class="hlt">creep</span> of quartz in the Truzzo meta-granite is possible to occur at low differential stresses because sufficient amounts of intergranular water ensure a high recovery rate by grain boundary migration while the absence of significant amounts of intragranular water is not crucial at natural conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004SPIE.5387...47K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004SPIE.5387...47K"><span id="translatedtitle">Dynamic <span class="hlt">characteristics</span> of piezoelectric shear <span class="hlt">deformable</span> composite plates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kolar, Ramesh</p> <p>2004-07-01</p> <p>Layered composites have attracted attention for their high specific stiffness, high specific strength, and application specific tailoring of their properties. It is also recognized that layered composites are prone to delamination failure in addition to other failure modes. Consideration of transverse shear on the <span class="hlt">deformation</span> behavior of the composites is an important aspect in the study of delamination mode failure of such plates. In this paper, we consider the effects of including the transverse shear <span class="hlt">deformation</span> on the vibration <span class="hlt">characteristics</span> of layered piezoelectric composites. The formulation is based on the Raleigh-Ritz method using the beam <span class="hlt">characteristic</span> functions. MATLAB based symbollic math tool box is used in evaluating th eintegrals resulting from the Raleigh Ritz approach. Various commonly occuring boundary conditions are discussed. Results are provided showing the effects of the shear <span class="hlt">deformation</span> on the dynamics of layered laminated composites. The effects of laminate thickness, fiber orientation, and the plate aspect ratios on the free vibration <span class="hlt">characteristics</span> of the composite laminates are given to demonstrate the methodology described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JNuM..443..484P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JNuM..443..484P"><span id="translatedtitle"><span class="hlt">Creep</span> <span class="hlt">deformation</span> and mechanisms in Haynes 230 at 800 °C and 900 °C</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pataky, Garrett J.; Sehitoglu, Huseyin; Maier, Hans J.</p> <p>2013-11-01</p> <p><span class="hlt">Creep</span> was studied in Haynes 230, a material candidate for the very high temperature reactor's intermediate heat exchanger, at 800 °C and 900 °C. This study focused on the differences between the behavior at the two elevated temperature, and using the microstructure, grain boundary serrations and triple junction strain concentrations were quantitatively identified. There was significant damage in the 900 °C samples and the <span class="hlt">creep</span> was almost entirely tertiary. In contrast, the 800 °C sample exhibited secondary <span class="hlt">creep</span>. Using an Arrhenius equation, the minimum <span class="hlt">creep</span> rate exponents were found to be n ≈ 3 and n ≈ 5 for 900 °C and 800 °C, respectively. The <span class="hlt">creep</span> mechanisms were identified as solute drag for n ≈ 3 and dislocation climb for n ≈ 5. Strain concentrations were identified at triple junctions and grain boundary serrations using high resolution digital image correlation overlaid on the microstructure. The grain boundary serrations restrict grain boundary sliding which may reduce the <span class="hlt">creep</span> damage at triple junctions and extend the <span class="hlt">creep</span> life of Haynes 230 at elevated temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999MMTA...30.2049L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999MMTA...30.2049L"><span id="translatedtitle"><span class="hlt">Creep</span> <span class="hlt">deformation</span> and fracture of a Cr/Mo/V bolting steel containing selected trace-element additions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Larouk, Z.; Pilkington, R.</p> <p>1999-08-01</p> <p>The article reports the <span class="hlt">creep</span> behavior, at 565 °C, of 1Cr1Mo0.75V (Ti, B) (Durehete D1055) steel, in each of two grain sizes and doped with individual trace elements such as P, As, and Sn, in comparison to a reference cast of the base material containing 0.08 wt pct Ti. The addition of the trace elements P, As, or Sn (each <0.045 wt pct) appears to produce no significant effect on <span class="hlt">creep</span> strength or <span class="hlt">creep</span> crack-growth resistance at 565 °C. The fine-grained material shows low <span class="hlt">creep</span> strength but notch strengthening, while the coarse-grained material shows higher <span class="hlt">creep</span> strength and exhibits notch weakening for test times up to 2750 hours. From <span class="hlt">creep</span> crack-growth tests, it appears that the C* parameter is not appropriate for correlating the <span class="hlt">creep</span> crack-growth rate under the present test conditions. The parameters K I or σ net are found to correlate better, but, from the present data, it is not possible to judge which of these parameters is more appropriate for general use. It is suggested that the presence of Ti in CrMoV steels has an inhibiting effect on trace-element embrittlement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/3651','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/3651"><span id="translatedtitle">Correlation of <span class="hlt">Creep</span> Behavior of Domal Salts</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Munson, D.E.</p> <p>1999-02-16</p> <p>The experimentally determined <span class="hlt">creep</span> responses of a number of domal salts have been reported in, the literature. Some of these <span class="hlt">creep</span> results were obtained using standard (conventional) <span class="hlt">creep</span> tests. However, more typically, the <span class="hlt">creep</span> data have come from multistage <span class="hlt">creep</span> tests, where the number of specimens available for testing was small. An incremental test uses abrupt changes in stress and temperature to produce several time increments (stages) of different <span class="hlt">creep</span> conditions. Clearly, the ability to analyze these limited data and to correlate them with each other could be of considerable potential value in establishing the mechanical <span class="hlt">characteristics</span> of salt domes, both generally and specifically. In any analysis, it is necessary to have a framework of rules to provide consistency. The basis for the framework is the Multimechanism-<span class="hlt">Deformation</span> (M-D) constitutive model. This model utilizes considerable general knowledge of material <span class="hlt">creep</span> <span class="hlt">deformation</span> to supplement specific knowledge of the material response of salt. Because the <span class="hlt">creep</span> of salt is controlled by just a few micromechanical mechanisms, regardless of the origin of the salt, certain of the material parameters are values that can be considered universal to salt. Actual data analysis utilizes the methodology developed for the Waste Isolation Pilot Plant (WIPP) program, and the response of a bedded pure WIPP salt as the baseline for comparison of the domal salts. <span class="hlt">Creep</span> data from Weeks Island, Bryan Mound, West Hackberry, Bayou Choctaw, and Big Hill salt domes, which are all sites of Strategic Petroleum Reserve (SPR) storage caverns, were analyzed, as were data from the Avery Island, Moss Bluff, and Jennings salt domes. The analysis permits the parameter value sets for the domal salts to be determined in terms of the M-D model with various degrees of completeness. In turn this permits detailed numerical calculations simulating cavern response. Where the set is incomplete because of the sparse database, reasonable</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......261S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......261S"><span id="translatedtitle"><span class="hlt">Creep</span> <span class="hlt">Deformation</span>, Rupture Analysis, Heat Treatment and Residual Stress Measurement of Monolithic and Welded Grade 91 Steel for Power Plant Components</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shrestha, Triratna</p> <p></p> <p>Modified 9Cr-1 Mo (Grade 91) steel is currently considered as a candidate material for reactor pressure vessels (RPVs) and reactor internals for the Very High Temperature Reactor (VHTR), and in fossil-fuel fired power plants at higher temperatures and stresses. The tensile <span class="hlt">creep</span> behavior of Grade 91 steel was studied in the temperature range of 600°C to 750°C and stresses between 35 MPa and 350 MPa. Heat treatment of Grade 91 steel was studied by normalizing and tempering the steel at various temperatures and times. Moreover, Thermo-Ca1c(TM) calculation was used to predict the precipitate stability and their evolution, and construct carbon isopleths of Grade 91 steel. Residual stress distribution across gas tungsten arc welds (GTAW) in Grade 91 steel was measured by the time-of-flight neutron diffraction using the Spectrometer for Materials Research at Temperature and Stress (SMARTS) diffractometer at Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, NM, USA. Analysis of <span class="hlt">creep</span> results yielded stress exponents of ˜9-11 in the higher stress regime and ˜1 in the lower stress regime. The <span class="hlt">creep</span> behavior of Grade 91 steel was described by the modified Bird-Mukherjee-Dorn relation. The rate-controlling <span class="hlt">creep</span> <span class="hlt">deformation</span> mechanism in the high stress regime was identified as the edge dislocation climb with a stress exponent of n = 5. On the other hand, the <span class="hlt">deformation</span> mechanism in the Newtonian viscous <span class="hlt">creep</span> regime (n = 1) was identified as the Nabarro-Herring <span class="hlt">creep</span>. <span class="hlt">Creep</span> rupture data were analyzed in terms of Monkman-Grant relation and Larson-Miller parameter. <span class="hlt">Creep</span> damage tolerance factor and stress exponent were used to identify the cause of <span class="hlt">creep</span> damage. The fracture surface morphology of the ruptured specimens was studied by scanning electron microscopy to elucidate the failure mechanisms. Fracture mechanism map for Grade 91 steel was developed based on the available material parameters and experimental observations. The microstructural</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20634764','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20634764"><span id="translatedtitle"><span class="hlt">Creep</span> <span class="hlt">deformation</span> behavior of Sn-3.5Ag solder/Cu couple at small length scales</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kerr, M.; Chawla, N</p> <p>2004-09-06</p> <p>In order to adequately characterize the behavior of solder balls in electronic devices, the mechanical behavior of solder joints needs to be studied at small length scales. The <span class="hlt">creep</span> behavior of single solder ball Sn-Ag/Cu solder joints was studied in shear, at 25, 60, 95, and 130 deg. C, using a microforce testing system. A change in the <span class="hlt">creep</span> stress exponent with increasing stress was observed and explained in terms of a threshold stress for bypass of Ag{sub 3}Sn particles by dislocations. The stress exponent was also temperature dependent, exhibiting an increase in exponent of two from lower to higher temperature. The activation energy for <span class="hlt">creep</span> was found to be temperature dependant, correlating with self-diffusion of pure Sn at high temperatures, and dislocation core diffusion of pure Sn at lower temperatures. Normalizing the <span class="hlt">creep</span> rate for activation energy and the temperature-dependence of shear modulus allowed for unification of the <span class="hlt">creep</span> data. Microstructure characterization, including preliminary TEM analysis, and fractographic analysis were conducted in order to fully describe the <span class="hlt">creep</span> behavior of the material.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/8074091','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/8074091"><span id="translatedtitle">In vitro torque-<span class="hlt">deformation</span> <span class="hlt">characteristics</span> of orthodontic polycarbonate brackets.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Feldner, J C; Sarkar, N K; Sheridan, J J; Lancaster, D M</p> <p>1994-09-01</p> <p>The purpose of this study was to investigate the torque-<span class="hlt">deformation</span> <span class="hlt">characteristics</span> of the following four types of polycarbonate brackets: (1) pure polycarbonate, PPC (anterior Miura, RMO, Denver, Colo.), (2) ceramic reinforced polycarbonate, CRPC (Silkon bracket, American, Sheboygan, Wis.), (3) metal slot reinforced polycarbonate, MRPC (Plastic bracket, Tella Tech, Miami, Fla.), and (4) metal slot and ceramic reinforced polycarbonate, MCRPC (Spirit, Ormco, Glendora, Calif.). A stainless steel bracket, (Mini Diamond, Ormco, Glendora, Calif.), was used as a control. Ten brackets of each type were tested. Each bracket was bonded to a porcelain tooth and engaged in a torquemeter. The tooth-bracket assembly was made stationary by embedding it in die stone. Torsion was applied to the bracket at 4 degrees per minute and the resultant torque (grams.centimeters) and <span class="hlt">deformation</span> (degree) were measured. For optimum labiolingual tooth movement for a maxillary incisor at 175 grams . centimeters, the amount of angular deflection necessary for the different polycarbonate brackets was the following: (a) 15 degrees for MRPC, (b) 17 degrees for MRPC, (c) 24 degrees for CRPC, and (d) > 30 degrees for PPC. The amount of <span class="hlt">deformation</span> at this deflection was the least for MRCP followed by MCRPC, CRCP, and PPC. When compared with the stainless steel bracket, all polycarbonate brackets showed significantly (p < 0.0001) higher <span class="hlt">deformation</span> and lower torque. Within the polycarbonate group, there was a significant difference (p < 0.0001) between each bracket for both measurements. The MRPC produced the highest torque and lowest <span class="hlt">deformation</span> values followed by the MCRPC, CRCP, and PPC. It appears that only the metal slot reinforced brackets are clinically capable of torquing teeth sufficiently. PMID:8074091</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5591849','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5591849"><span id="translatedtitle">ACCEPT: a three-dimensional finite element program for large <span class="hlt">deformation</span> elastic-plastic-<span class="hlt">creep</span> analysis of pressurized tubes (LWBR/AWBA Development Program)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hutula, D.N.; Wiancko, B.E.</p> <p>1980-03-01</p> <p>ACCEPT is a three-dimensional finite element computer program for analysis of large-<span class="hlt">deformation</span> elastic-plastic-<span class="hlt">creep</span> response of Zircaloy tubes subjected to temperature, surface pressures, and axial force. A twenty-mode, tri-quadratic, isoparametric element is used along with a Zircaloy materials model. A linear time-incremental procedure with residual force correction is used to solve for the time-dependent response. The program features an algorithm which automatically chooses the time step sizes to control the accuracy and numerical stability of the solution. A contact-separation capability allows modeling of interaction of reactor fuel rod cladding with fuel pellets or external supports.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3627449','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3627449"><span id="translatedtitle">Investigation of <span class="hlt">creep</span> mechanical <span class="hlt">characteristics</span> of femoral prostheses by simulated hip replacement</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>LIU, GUANG-YAO; JIN, YAN; LI, PENG</p> <p>2013-01-01</p> <p>In order to provide <span class="hlt">creep</span> mechanical parameters for the clinical application of both traditional and reserved anatomy femoral artificial joint replacements, simulated hip replacement femoral stress relaxation and <span class="hlt">creep</span> experiments were performed. Twenty-four corpse femoral specimens were obtained, with 8 specimens being randomly assigned to the control group and 8 specimens being randomly assigned to the traditional prosthesis group. Our results showed that the retaining femoral neck prosthesis and traditional prosthesis groups have different stress relaxation and <span class="hlt">creep</span> mechanical properties. PMID:23596489</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AGUFM.S22A0425M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFM.S22A0425M"><span id="translatedtitle"><span class="hlt">Creep</span>: Long-term Time-Dependent Rock <span class="hlt">Deformation</span> in a Deep-sea Laboratory in the Ionian sea: a Pilot Study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meredith, P. G.; Boon, S.; Vinciguerra, S.; Bowles, J.; NEMO Group,.</p> <p>2003-12-01</p> <p>Time-dependent brittle rock <span class="hlt">deformation</span> is of first-order importance for understanding the long-term behavior of water saturated rocks in the Earth's upper crust. Interpretation of results from traditional laboratory brittle <span class="hlt">creep</span> experiments have generally been in terms of three individual <span class="hlt">creep</span> phases; primary (decelerating), secondary (constant strain rate or quasi-steady-state) and tertiary (accelerating or unstable). The <span class="hlt">deformation</span> may be distributed during the first two, but localizes onto a fault plane during phase three. More recently, models have been proposed that explain the trimodal shape of <span class="hlt">creep</span> curves in terms of the competition between a weakening mechanism and a strengthening mechanism, with the weakening mechanism eventually dominating and leading to localized failure. However, a major problem is that it is difficult to distinguish between these competing mechanisms and models given the lower limit of strain rates achievable in laboratory experiments over practicable time scales. This study aims to address that problem directly by extending significantly the range of achievable strain rates through much longer-term experiments conducted in a deep-sea laboratory in the Ionian sea. The project takes advantage of a collaboration with the NEMO Group-INFN, a consortium that is developing a large volume (1 km3) deep-sea detector for high-energy (>1019 eV) cosmic neutrinos. A suitable test site has been identified, some 20km north-east of Catania in Sicily, at a depth of 2100m. Within the <span class="hlt">CREEP</span> <span class="hlt">deformation</span> apparatus, confining pressure is provided by the ambient water pressure (>22MPa), and the constant axial stress is provided by an actuator that amplifies this pressure. Measurement transducers and a data acquisition system are sealed internally, with power provided for up to 6 months by an internal battery pack. The great advantage of operating in the deep sea in this way is that the system is essentially passive, has few moving parts, and requires no</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19900029846&hterms=alloy+crystals&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dalloy%2Bcrystals','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900029846&hterms=alloy+crystals&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dalloy%2Bcrystals"><span id="translatedtitle">High temperature <span class="hlt">creep</span> behavior of single crystal gamma prime and gamma alloys</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nathal, M. V.; Diaz, J. O.; Miner, R. V.</p> <p>1989-01-01</p> <p>The <span class="hlt">creep</span> behavior of single crystals of gamma-prime and gamma alloys were investigated and compared to the response of two-phase superalloys tested previously. High temperature <span class="hlt">deformation</span> in the gamma alloys was <span class="hlt">characteristic</span> of a climb-controlled mechanism, whereas the gamma-prime based materials exhibited glide-controlled <span class="hlt">creep</span> behavior. The superalloys were much more <span class="hlt">creep</span> resistant than their constituent phases, which indicates the importance of the gamma/gamma-prime interface as a barrier for dislocation motion during <span class="hlt">creep</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6436507','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6436507"><span id="translatedtitle"><span class="hlt">Deformation</span> and fracture <span class="hlt">characteristics</span> of spent Zircaloy fuel cladding</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chung, H.M.; Yaggee, F.L.</p> <p>1982-09-01</p> <p>For a better understanding of Zircaloy fuel-rod failure by the pellet-cladding interaction (PCI) phenomenon, a mechanistic study of <span class="hlt">deformation</span> and fracture behavior of spent power reactor fuel cladding under simulated PCI conditions was conducted. Zircaloy-2 cladding specimens, obtained from fuel assemblies of operating power reactors, were <span class="hlt">deformed</span> to fracture at 325/sup 0/C by internal gas pressurization in the absence of fission product simulants. Fracture <span class="hlt">characteristics</span> and microstructures were examined via SEM, TEM, and HVEM. Numerous dislocation tangles and cell structures, observed in TEM specimens of cladding tubes that failed in a ductile manner, were consistent with SEM observations of a limited number of dimples <span class="hlt">characteristic</span> of microvoid coalescence. A number of brittle-type failures were produced without the influence of fission product simulants. The brittle cracks occurred near the areas compressed by the Swagelok fittings of the internally pressurized tube and propagated from the outer to the inner surface. Since the outer surface was isolated and maintained under a flowing stream of pure helium, it is unlikely that the brittle-type failure was influenced by any fission product traces. SEM fractography of the brittle-type failure revealed a large area of transgranular pseudocleavage with limited areas of ductile fluting, which were similar in appearance to the surfaces produced by in-reactor PCI-type failures. A TEM evaluation of the cladding in the vicinity of the through-wall crack revealed numerous locations that contained an extensive amount of second-phase precipitate (Zr/sub 3/O). We believe that the brittle-type failures of the irradiated spent fuel cladding in the stress rupture experiments are associated with segregation of oxygen, which leads to the formation of the order structure, an immobilization of dislocations, and minimal plastic <span class="hlt">deformation</span> in the material.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740022222','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740022222"><span id="translatedtitle"><span class="hlt">Deformation</span> <span class="hlt">characteristics</span> and time-dependent notch sensitivity of Udimet 700 at intermediate temperatures</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilson, D. J.</p> <p>1974-01-01</p> <p>Time dependent notch sensitivity was observed in Udimet 700 sheet, bar, and investment castings between 1000 and 1400 F (538 -760 C), but not at 1600 F (871 C). As was the case for modified Waspaloy, Waspaloy and Inconel 718, it occurred in notched specimens loaded below the yield strength when the <span class="hlt">creep</span> <span class="hlt">deformation</span> was localized. For each alloy and notched specimen geometry, a stress-average particle size zone can be defined that characterizes the notch sensitive behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/12078720','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/12078720"><span id="translatedtitle">Effect of <span class="hlt">creep</span> feed consumption on individual feed intake <span class="hlt">characteristics</span> and performance of group-housed weanling pigs.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bruininx, E M A M; Binnendijk, G P; van der Peet-Schwering, C M C; Schrama, J W; den Hartog, L A; Everts, H; Beynen, A C</p> <p>2002-06-01</p> <p>To assess the effects of <span class="hlt">creep</span> feed consumption on individual feed intake <span class="hlt">characteristics</span> and performance of group-housed weaned pigs, 16 litters (149 piglets) were fed a commercial <span class="hlt">creep</span> feed (3,040 kcal NE/kg, 15.2 g lysine/kg) supplemented with 1% chromic oxide. Another five litters (48 piglets) were not given access to <span class="hlt">creep</span> feed (no-feed). Piglets were weaned at 28 d after birth. On d 18, 22, and 27 of age, fecal samples from all the piglets were taken using fecal loops. A green color of the feces indicated that the piglet had eaten <span class="hlt">creep</span> feed. Piglets that had green-colored feces three times were considered as eaters. Piglets that never showed green-colored feces were considered as non-eaters. At weaning 22 piglets of each type (no-feed, non-eaters, and eaters) were selected based on BW, litter origin, and sex. These 66 pigs were assigned to six pens equipped with computerized feeding stations. Eaters, non-eaters, and no-feed pigs were equally divided over all six pens. After weaning a prestarter (d 0 to 13) and a starter diet (d 14 to 34) were offered for ad libitum consumption. The individual feed intake <span class="hlt">characteristics</span> of latency time (interval between weaning and first feed intake) and initial feed intake (intake during the first 24 h following first feed intake) and performance traits were determined for all piglets. The pigs that were designated as eaters needed less time between weaning and first feed intake than the pigs that were designated as non-eaters and no-feed pigs (P = 0.04 and P = 0.06, respectively). Initial feed intake was not affected (P > 0.1) by feed intake prior to weaning. However, during d 0 to 8 the eaters had more visits per day during which feed was consumed than both the non-eaters and no-feed pigs. Averaged over the first 8 d after weaning, the ADFI and ADG of the eaters were higher than that of the non-eaters and no-feed pigs (P < 0.05). Averaged over the total 34-d period the effect of <span class="hlt">creep</span> feed intake on postweaning ADFI was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013FrME....8..181M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013FrME....8..181M"><span id="translatedtitle">A model for <span class="hlt">creep</span> life prediction of thin tube using strain energy density as a function of stress triaxiality under quasistatic loading employing elastic-<span class="hlt">creep</span> & elastic-plastic-<span class="hlt">creep</span> <span class="hlt">deformation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mahmood, Tahir; Kanapathipillai, Sangarapillai; Chowdhury, Mahiuddin</p> <p>2013-06-01</p> <p>This paper demonstrates the application of a new multiaxial <span class="hlt">creep</span> damage model developed by authors using stress traixiality to predict the failure time of a component made of 0.5%Cr-0.5%Mo-0.25%V low alloy steel. The model employs strain energy density and assumes that the uniaxial strain energy density of a component can be easily calculated and can be converted to multi-axial strain energy density by multiplying it to a function of stress trixiality which is a ratio of mean stress to equivalent stress. For comparison, an elastic-<span class="hlt">creep</span> and elastic-plastic-<span class="hlt">creep</span> finite element analysis (FEA) is performed to get multi-axial strain energy density of the component which is compared with the calculated strain energy density for both cases. The verification and application of the model are demonstrated by applying it to thin tube for which the experimental data are available. The predicted failure times by the model are compared with the experimental results. The results show that the proposed model is capable of predicting failure times of the component made of the above-mentioned material with an accuracy of 4.0%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.T33B1888J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.T33B1888J"><span id="translatedtitle"><span class="hlt">Deformation</span> <span class="hlt">characteristics</span> and history along the Ilkwang Fault, SE Korea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jin, K.; Kim, Y.; Yang, S.; Choi, J.</p> <p>2009-12-01</p> <p>The NNE-SSW trending Ilkwang Fault is one of the major structural features around SE Korea. It is a high angle, right-lateral strike-slip fault with a displacement of about 1.2 km. The basement around the fault is Cretaceous sedimentary and volcanic rocks forming a part of the Gyeongsang Basin in SE Korea, and it is intruded by later igneous rocks. The fault has not been studied intensively due to poor exposure along the fault. However, understanding the <span class="hlt">characteristics</span> of the Ilkwang Fault is important because three nuclear power plants and one nuclear waste disposal site are located around the fault. We have mainly investigated along the new road-cut sections of the Busan-Ulsan Highway. Many geologic structures such as dykes, folds, and faults are measured in several studied sites. The analyzed structural patterns indicate multi-<span class="hlt">deformation</span> including reactivation of pre-existing faults. In this study, we analyzed variation patterns of attitude on the beddings and fractures around some parts of the Ilkwang Fault. The strike/dip variation from the general attitude of the structural elements (e.g. beddings) is here used as an indicator of <span class="hlt">deformation</span> intensity across the fault. This analysis indicates that respect distances (highly <span class="hlt">deformed</span> area affected by faulting) along the Ilkwang Fault is about 1 km in sedimentary rocks and 200 m in volcanic rocks, respectively. It indicates that the Ilkwang Fault is a relatively big fault, and layered sedimentary rock is relatively weaker than massive volcanic rock under brittle <span class="hlt">deformation</span>. <span class="hlt">Deformation</span> history in the studied area, based on kinematic analysis of faults, joints and dykes, is as follows: 1) NNE-SSW trending reverse fault and fold. 2) E-W trending reverse fault and N-S trending acidic dykes. 3) ENE-WSW trending left-lateral fault, NNE-SSW trending right-lateral fault, and NE-SW trending basic dykes. 4) E-W trending normal fault. 5) N-S or NNE-SSW trending reverse fault.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.5115H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.5115H"><span id="translatedtitle">Brittle and compaction <span class="hlt">creep</span> in porous sandstone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heap, Michael; Brantut, Nicolas; Baud, Patrick; Meredith, Philip</p> <p>2015-04-01</p> <p>Strain localisation in the Earth's crust occurs at all scales, from the fracture of grains at the microscale to crustal-scale faulting. Over the last fifty years, laboratory rock <span class="hlt">deformation</span> studies have exposed the variety of <span class="hlt">deformation</span> mechanisms and failure modes of rock. Broadly speaking, rock failure can be described as either dilatant (brittle) or compactive. While dilatant failure in porous sandstones is manifest as shear fracturing, their failure in the compactant regime can be characterised by either distributed cataclastic flow or the formation of localised compaction bands. To better understand the time-dependency of strain localisation (shear fracturing and compaction band growth), we performed triaxial <span class="hlt">deformation</span> experiments on water-saturated Bleurswiller sandstone (porosity = 24%) under a constant stress (<span class="hlt">creep</span>) in the dilatant and compactive regimes, with particular focus on time-dependent compaction band formation in the compactive regime. Our experiments show that inelastic strain accumulates at a constant stress in the brittle and compactive regimes leading to the development of shear fractures and compaction bands, respectively. While <span class="hlt">creep</span> in the dilatant regime is characterised by an increase in porosity and, ultimately, an acceleration in axial strain to shear failure (as observed in previous studies), compaction <span class="hlt">creep</span> is characterised by a reduction in porosity and a gradual deceleration in axial strain. The overall deceleration in axial strain, AE activity, and porosity change during <span class="hlt">creep</span> compaction is punctuated by excursions interpreted as the formation of compaction bands. The growth rate of compaction bands formed during <span class="hlt">creep</span> is lower as the applied differential stress, and hence background <span class="hlt">creep</span> strain rate, is decreased, although the inelastic strain required for a compaction band remains constant over strain rates spanning several orders of magnitude. We find that, despite the large differences in strain rate and growth rate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/203524','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/203524"><span id="translatedtitle">Effect of <span class="hlt">creep</span> strain on microstructural stability and <span class="hlt">creep</span> resistance of a TiAl/Ti{sub 3}Al lamellar alloy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wert, J.A.; Bartholomeusz, M.F.</p> <p>1996-01-01</p> <p><span class="hlt">Creep</span> of a TiAl/Ti{sub 3}Al alloy with a lamellar microstructure causes progressive spheroidization of the lamellar microstructure. Microstructural observations reveal that <span class="hlt">deformation</span>-induced spheroidization (DIS) occurs by <span class="hlt">deformation</span> and fragmentation of lamellae in localized shear zones at interpacket boundaries and within lamellar packets. <span class="hlt">Deformation</span>-induced spheroidization substantially increases the interphase interfacial area per unit volume, demonstrating that DIS is not a coarsening process driven by reduction of interfacial energy per unit volume. <span class="hlt">Creep</span> experiments reveal that DIS increases the minimum <span class="hlt">creep</span> rate ({dot {var_epsilon}}{sub min}) during <span class="hlt">creep</span> at constant stress and temperature; the activation energy (Q{sub c}) and stress exponent (n) for <span class="hlt">creep</span> are both reduced as a result of DIS. Values of n and Q{sub c} for the lamellar microstructure are typical of a dislocation <span class="hlt">creep</span> mechanism, while estimated values of n and Q{sub c} for the completely spheroidized microstructure are <span class="hlt">characteristic</span> of a diffusional <span class="hlt">creep</span> mechanism. The increase in {dot {var_epsilon}}{sub min} associated with DIS is thus attributed primarily to a change of <span class="hlt">creep</span> mechanism resulting from microstructural refinement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994AIAAJ..32..190X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994AIAAJ..32..190X"><span id="translatedtitle">Treatment of material <span class="hlt">creep</span> and nonlinearities in flexible mulitbody dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xie, M.; Amirouche, F. M. L.</p> <p>1994-01-01</p> <p>This paper addresses the modeling of the generalized active forces resulting from <span class="hlt">deformable</span> bodies when subjected to high temperature conditions, elastic-plastic <span class="hlt">deformations</span>, <span class="hlt">creep</span> effects, and material nonlinearities. The effects of elastic-plastic <span class="hlt">deformations</span> are studied making use of the nonlinear stress-strain relationship and the geometrical stiffness concepts. <span class="hlt">Creep</span> conditions resulting from high temperature are studied through several proposed models. Materials nonlinearities for isotropic and composites are accounted for by their tangential elasticity matrix. A general procedure used in the study of multibody systems dynamics with elastic-plastic bodies depicting the <span class="hlt">characteristics</span> mentioned is developed. This includes an explicit formulation of the equations of motion using Kane's equations, finite element method, continuum mechanics, and modal coordinate reduction techniques. A numerical simulation of a flexible robotic arm with a prescribed angular velocity subject to high temperature conditions is analyzed. The effects of <span class="hlt">creep</span> are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730003880','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730003880"><span id="translatedtitle">Effect of temperature on tensile and <span class="hlt">creep</span> <span class="hlt">characteristics</span> of PRD49 fiber/epoxy composites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hanson, M. P.</p> <p>1972-01-01</p> <p>Tensile and <span class="hlt">creep</span> data of PRD49-1 and 3 fiber/epoxy-resin composites are presented. Tensile data were obtained from 20 to 477 K (-423 to 400 F). Tensile strengths and moduli were determined at selected temperatures. <span class="hlt">Creep</span> data are presented for fiber composites at 297, 422 and 450 K (75, 300, and 350 F) for as long as 1000 hours at stress levels of approximately 50 and 80 percent of the ultimate tensile strength at 297 K (75 F). Details of tensile specimens and test procedures used in the investigation are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/624244','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/624244"><span id="translatedtitle"><span class="hlt">Creep</span> crack growth behavior of aluminum alloy 2519. Part 1: Experimental analysis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hamilton, B.C.; Saxena, A.; McDowell, D.L.; Hall, D.E.</p> <p>1997-12-31</p> <p>The discipline of time-dependent fracture mechanics has traditionally focused on the <span class="hlt">creep</span> crack growth behavior of high-temperature materials that display <span class="hlt">creep</span>-ductile behavior, such as stainless steels and chromium-molybdenum steels. Elevated temperature aluminum alloys, however, have been developed that exhibit <span class="hlt">creep</span>-brittle behavior; in this case, the <span class="hlt">creep</span> crack growth rate correlates with the stress intensity factor, K. The fracture <span class="hlt">characteristics</span> of aluminum alloy 2519-T87 were studied at 135 C, and the <span class="hlt">creep</span> and <span class="hlt">creep</span> crack growth behavior were characterized utilizing experimental and numerical methods. The strain to failure for <span class="hlt">creep</span> <span class="hlt">deformation</span> specimens was limited to only 1.2 to 2.0%. <span class="hlt">Creep</span> crack growth tests revealed a unique correlation between the <span class="hlt">creep</span> crack growth rate and K, a result consistent with <span class="hlt">creep</span>-brittle behavior. No experimental correlation was found between the <span class="hlt">creep</span> crack growth rate and the C{sub t} parameter. Microscopy of fracture surfaces revealed distinct regions of intergranular and transgranular fracture, and the transition between the fracture regions was found to occur at a critical K-level. Experimental results also appeared to show that initiation of crack growth (incubation) is controlled by the accumulation of a critical amount of damage ahead of the crack tip and that a correlation exists between the incubation time and K. Total time to failure is viewed as a summation of the incubation period and the crack growth period, and the design importance of incubation time is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JSG....26..793I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JSG....26..793I"><span id="translatedtitle">Development of shape- and lattice-preferred orientations of amphibole grains during initial cataclastic <span class="hlt">deformation</span> and subsequent <span class="hlt">deformation</span> by dissolution-precipitation <span class="hlt">creep</span> in amphibolites from the Ryoke metamorphic belt, SW Japan [review article</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Imon, Reiko; Okudaira, Takamoto; Kanagawa, Kyuichi</p> <p>2004-05-01</p> <p>Amphibolites from the Ryoke metamorphic belt, SW Japan were <span class="hlt">deformed</span> initially by cataclasis and subsequently by dissolution-precipitation <span class="hlt">creep</span>. Initial cataclastic <span class="hlt">deformation</span> produced a rather weak shape-preferred orientation (SPO) of brown amphibole grains with small aspect ratios as well as a poorly developed amphibole lattice-preferred orientation (LPO) with n α (≈ a[100]) axes scattered subnormal to the foliation and n γ or c[001] axes scattered around the lineation. During later <span class="hlt">deformation</span> by dissolution-precipitation <span class="hlt">creep</span>, preferential dissolution at grain boundaries subparallel to the foliation and simultaneous compaction normal to the foliation have likely produced a distinct SPO of elongate brown amphibole grains subparallel to the foliation as well as their LPO such that their n γ or c axes are scattered around the lineation, while n α (≈ a) and n β (= b[010]) are spread along a girdle normal to the lineation. Also during this <span class="hlt">deformation</span> green amphibole precipitated as isolated grains or in pressure shadow regions around brown amphibole grains. Nucleation and anisotropic growth of isolated green amphibole grains according to the orientations of the principal stress directions produced an LPO of these grains such that their n α (≈ a) are oriented normal to foliation, n β (= b) within the foliation normal to the lineation and n γ (or c) axes are parallel to the lineation. In addition, there is an associated SPO. Growth of green amphibole in pressure shadow regions around brown amphibole grains occurs either syntaxially or anisotropically according to the orientations of the principal stress directions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....4338M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....4338M"><span id="translatedtitle"><span class="hlt">Creep</span>: long-term time-dependent rock <span class="hlt">deformation</span> in a deep-sea laboratory in the ionian sea: a pilot study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meredith, P.; Boon, S.; Vinciguerra, S.; Bowles, J.; Hughes, N.; Migneco, E.; Musumeci, M.; Piattelli, P.; Riccobene, G.; Vinciguerra, D.</p> <p>2003-04-01</p> <p>Time-dependent brittle rock <span class="hlt">deformation</span> is of first-order importance for understanding the long-term behaviour of water saturated rocks in the Earth's upper crust. The traditional way of investigating this has been to carry out laboratory "brittle <span class="hlt">creep</span>" experiments. Results have been interpreted involving three individual <span class="hlt">creep</span> phases; primary (decelerating), secondary (constant strain rate or steady state) and tertiary (accelerating or unstable). The <span class="hlt">deformation</span> may be distributed during the first two, but localizes onto a fault plane during phase three. However, it is difficult to distinguish between competing mechanisms and models given the lower limit of strain rates practicably achievable in the laboratory. The study reported here aims to address this problem directly by extending significantly the range of achievable strain rates through much longer-term experiments conducted in a deep-sea laboratory in the Ionian sea. The project takes advantage of a collaboration with the Laboratori Nazionali del Sud (LNS) of the Italian National Institute of Nuclear Physics (INFN), that is developing a deep-sea laboratory for a very large volume (1 km3) deep-sea detector of high-energy (>1019 eV) cosmic neutrinos (NEMO). A suitable deep-sea site has been identified, some 20km south-west of Catania in Sicily, with flat bathymetry at a depth of 2100m. The <span class="hlt">CREEP</span> <span class="hlt">deformation</span> apparatus is driven by an actuator that amplifies the ambient water pressure, while the confining pressure around the rock sample is provided by the ambient water pressure (>20MPa). Measurement transducers and a low-energy data acquisition system are sealed internally, with power provided for up to 6 months by an internal battery pack. The great advantage of operating in the deep sea in this way is that the system is simple; it is "passive", has few moving parts, and requires no maintenance. The apparatus is fixed approximately 10m above the seabed; held in place by a disposable concrete anchor and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JSG....37...89Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JSG....37...89Z"><span id="translatedtitle">Extreme ductile <span class="hlt">deformation</span> of fine-grained salt by coupled solution-precipitation <span class="hlt">creep</span> and microcracking: Microstructural evidence from perennial Zechstein sequence (Neuhof salt mine, Germany)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Závada, Prokop; Desbois, Guillaume; Schwedt, Alexander; Lexa, Ondrej; Urai, Janos L.</p> <p>2012-04-01</p> <p>Microstructural study revealed that the ductile flow of intensely folded fine-grained salt exposed in an underground mine (Zechstein-Werra salt sequence, Neuhof mine, Germany) was accommodated by coupled activity of solution-precipitation (SP) <span class="hlt">creep</span> and microcracking of the halite grains. The grain cores of the halite aggregates contain remnants of sedimentary microstructures with straight and chevron shaped fluid inclusion trails (FITs) and are surrounded by two concentric mantles reflecting different events of salt precipitation. Numerous intra-granular or transgranular microcracks originate at the tips of FITs and propagate preferentially along the interface between sedimentary cores and the surrounding mantle of reprecipitated halite. These microcracks are interpreted as tensional Griffith cracks. Microcracks starting at grain boundary triple junctions or grain boundary ledges form due to stress concentrations generated by grain boundary sliding (GBS). Solid or fluid inclusions frequently alter the course of the propagating microcracks or the cracks terminate at these inclusions. Because the inner mantle containing the microcracks is corroded and is surrounded by microcrack-free outer mantle, microcracking is interpreted to reflect transient failure of the aggregate. Microcracking is argued to play a fundamental role in the continuation and enhancement of the SP-GBS <span class="hlt">creep</span> during halokinesis of the Werra salt, because the transgranular cracks (1) provide the ingress of additional fluid in the grain boundary network when cross-cutting the FITs and (2) decrease grain size by splitting the grains. More over, the ingress of additional fluids into grain boundaries is also provided by non-conservative grain boundary migration that advanced into FITs bearing cores of grains. Described readjustments of the microstructure and mechanical and chemical feedbacks for the grain boundary diffusion flow in halite-brine system are proposed to be comparable to other rock-fluid or</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014PhyB..435...40B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014PhyB..435...40B&link_type=ABSTRACT"><span id="translatedtitle">Memory <span class="hlt">characteristics</span> of hysteresis and <span class="hlt">creep</span> in multi-layer piezoelectric actuators: An experimental analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Biggio, Matteo; Butcher, Mark; Giustiniani, Alessandro; Masi, Alessandro; Storace, Marco</p> <p>2014-02-01</p> <p>In this paper we provide an experimental characterization of <span class="hlt">creep</span> and hysteresis in a multi-layer piezoelectric actuator (PEA), taking into account their relationships in terms of memory structure. We fit the well-known log-t model to the response of the PEA when driven by piecewise-constant signals, and find that both the instantaneous and the delayed response of the PEA display hysteretic dependence on the voltage level. We investigate experimentally the dependence of the <span class="hlt">creep</span> coefficient on the input history, by driving the PEA along first-order reversal curves and congruent minor loops, and find that it displays peculiar features like strict congruence of the minor loops and discontinuities. We finally explain the observed experimental behaviors in terms of a slow relaxation of the staircase interface line in the Preisach plane.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811121S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811121S"><span id="translatedtitle">The role of fluid pressure in fault <span class="hlt">creep</span> vs. frictional instability: insights from rock <span class="hlt">deformation</span> experiments on carbonates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scuderi, Marco M.; Collettini, Cristiano</p> <p>2016-04-01</p> <p>Fluid overpressure is one of the primary mechanisms for tectonic fault slip. This mechanism is appealing as fluids lubricate the fault and fluid pressure, Pf, reduces the effective normal stress that holds the fault in place. However, current models of earthquake nucleation imply that stable sliding is favored by the increase of pore fluid pressure. Despite this opposite effects, currently, there are only a few studies on the role of fluid pressure under controlled, laboratory conditions. Here, we use laboratory experiments, conducted on a biaxial apparatus within a pressure vessel on limestone fault gouge, to: 1) evaluate the rate- and state- friction parameters as the pore fluid pressure is increased from hydrostatic to near lithostatic values and 2) fault <span class="hlt">creep</span> evolution as a function of a step increase in fluid pressure. In this second suite of experiments we reached 85% of the maximum shear strength and than in load control we induced fault slip by increasing fluid pressure. Our data show that the friction rate parameter (a-b) evolves from slightly velocity strengthening to velocity neutral behaviour and the critical slip distance, Dc, decreases from about 100 to 20 μm as the pore fluid pressure is increased. Fault <span class="hlt">creep</span> is slow (i.e 0.001μm/s) away from the maximum shear strength and for small increases in fluid pressure and it accelerates near the maximum shear strength and for larger fluid pressure build-ups, where we observe episodic accelerations/decelerations that in some cases evolve to small dynamic events. Our data suggest that fluid overpressure can increase aseismic <span class="hlt">creep</span> with the development of frictional instability. Since fault rheology and fault stability parameters change with fluid pressure, we suggest that a comprehensive characterization of these parameters is fundamental for better assessing the role of fluid pressure in natural and human induced earthquakes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014SMaS...23g5014X&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014SMaS...23g5014X&link_type=ABSTRACT"><span id="translatedtitle">Active disturbance rejection control for output force <span class="hlt">creep</span> <span class="hlt">characteristics</span> of ionic polymer metal composites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiong, Yan; Chen, Yang; Sun, Zhiyong; Hao, Lina; Dong, Jie</p> <p>2014-07-01</p> <p>Ionic polymer metal composites (IPMCs) are a type of electroactive polymer (EAP) that can be used as both sensors and actuators. An IPMC has enormous potential application in the field of biomimetic robotics, medical devices, and so on. However, an IPMC actuator has a great number of disadvantages, such as <span class="hlt">creep</span> and time-variation, making it vulnerable to external disturbances. In addition, the complex actuation mechanism makes it difficult to model and the demand of the control algorithm is laborious to implement. In this paper, we obtain a <span class="hlt">creep</span> model of the IPMC by means of model identification based on the method of <span class="hlt">creep</span> operator linear superposition. Although the mathematical model is not approximate to the IPMC accurate model, it is accurate enough to be used in MATLAB to prove the control algorithm. A controller based on the active disturbance rejection control (ADRC) method is designed to solve the drawbacks previously given. Because the ADRC controller is separate from the mathematical model of the controlled plant, the control algorithm has the ability to complete disturbance estimation and compensation. Some factors, such as all external disturbances, uncertainty factors, the inaccuracy of the identification model and different kinds of IPMCs, have little effect on controlling the output block force of the IPMC. Furthermore, we use the particle swarm optimization algorithm to adjust ADRC parameters so that the IPMC actuator can approach the desired block force with unknown external disturbances. Simulations and experimental examples validate the effectiveness of the ADRC controller.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980228107','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980228107"><span id="translatedtitle">Deterministic Multiaxial <span class="hlt">Creep</span> and <span class="hlt">Creep</span> Rupture Enhancements for CARES/<span class="hlt">Creep</span> Integrated Design Code</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jadaan, Osama M.</p> <p>1998-01-01</p> <p>High temperature and long duration applications of monolithic ceramics can place their failure mode in the <span class="hlt">creep</span> rupture regime. A previous model advanced by the authors described a methodology by which the <span class="hlt">creep</span> rupture life of a loaded component can be predicted. That model was based on the life fraction damage accumulation rule in association with the modified Monkman-Grant <span class="hlt">creep</span> rupture criterion. However, that model did not take into account the deteriorating state of the material due to <span class="hlt">creep</span> damage (e.g., cavitation) as time elapsed. In addition, the material <span class="hlt">creep</span> parameters used in that life prediction methodology, were based on uniaxial <span class="hlt">creep</span> curves displaying primary and secondary <span class="hlt">creep</span> behavior, with no tertiary regime. The objective of this paper is to present a <span class="hlt">creep</span> life prediction methodology based on a modified form of the Kachanov-Rabotnov continuum damage mechanics (CDM) theory. In this theory, the uniaxial <span class="hlt">creep</span> rate is described in terms of sum, temperature, time, and the current state of material damage. This scalar damage state parameter is basically an abstract measure of the current state of material damage due to <span class="hlt">creep</span> <span class="hlt">deformation</span>. The damage rate is assumed to vary with stress, temperature, time, and the current state of damage itself. Multiaxial <span class="hlt">creep</span> and <span class="hlt">creep</span> rupture formulations of the CDM approach are presented in this paper. Parameter estimation methodologies based on nonlinear regression analysis are also described for both, isothermal constant stress states and anisothermal variable stress conditions This <span class="hlt">creep</span> life prediction methodology was preliminarily added to the integrated design code CARES/<span class="hlt">Creep</span> (Ceramics Analysis and Reliability Evaluation of Structures/<span class="hlt">Creep</span>), which is a postprocessor program to commercially available finite element analysis (FEA) packages. Two examples, showing comparisons between experimental and predicted <span class="hlt">creep</span> lives of ceramic specimens, are used to demonstrate the viability of Ns methodology and the</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70027629','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70027629"><span id="translatedtitle">Postseismic relaxation and transient <span class="hlt">creep</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Savage, J.C.; Svarc, J.L.; Yu, S.-B.</p> <p>2005-01-01</p> <p>Postseismic <span class="hlt">deformation</span> has been observed in the epicentral area following the 1992 Landers (M = 7.3), 1999 Chi-Chi (M = 7.6), 1999 Hector Mine (M = 7.1), 2002 Denali (M = 7.9), 2003 San Simeon (M = 6.5), and 2004 Parkfield (M = 6.0) earthquakes. The observations consist of repeated GPS measurements of the position of one monument relative to another (separation ???100 km). The early observations (t < 0.1 year) are well fit by the function a' + c'log(t), where t is the time after the earthquake and a' and c' are constants chosen to fit the data. Because a log(t) time dependence is <span class="hlt">characteristic</span> of transient (primary) <span class="hlt">creep</span>, the early postseismic response may be governed by transient <span class="hlt">creep</span> as Benioff proposed in 1951. That inference is provisional as the stress conditions prevailing in postseismic relaxation are not identical to the constant stress condition in <span class="hlt">creep</span> experiments. The observed logarithmic time dependence includes no <span class="hlt">characteristic</span> time that might aid in identifying the micromechanical cause.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMOS21H..04M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMOS21H..04M"><span id="translatedtitle"><span class="hlt">Characteristics</span> of tsunamis generated by 3D <span class="hlt">deformable</span> granular landslides</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mohammed, F.; Fritz, H. M.; McFall, B.</p> <p>2010-12-01</p> <p>Landslides can trigger tsunamis with locally high amplitudes and runup, which can cause devastating effects in the near field region. The events of 1958 Lituya Bay, 1998 Papua New Guinea and 2006 Java tsunamis are reminders of the hazards associated with impulse waves. Tsunamis generated by granular landslides were studied in the three dimensional NEES tsunami wave basin (TWB) at Oregon State University (OSU) based on the generalized Froude similarity. A novel pneumatic landslide generator was deployed to simulate landslides with varying geometry and kinematics. Granular materials were used to model <span class="hlt">deformable</span> landslides. Measurement techniques such as particle image velocimetry (PIV), multiple above and underwater video cameras, multiple acoustic transducer arrays (MTA), as well as resistance wave and runup gauges were applied. Tsunami wave generation and propagation is studied off a hill slope, in fjords and around curved headlands. The wave generation was characterized by an extremely unsteady three phase flow consisting of the slide granulate, water and air entrained into the flow. Landslide <span class="hlt">deformation</span> is quantified and the slide kinematics with reference to slide surface velocity distribution and slide front velocity is obtained. Empirical equations for predicting the wave amplitude, period and wavelength are obtained. The generated waves depend on determined non-dimensional landslide and water body parameters such as the slide Froude number and relative slide shape at impact, among others. Attenuation functions of the leading wave crest amplitude, the lateral wave runup on the hill slope, the wave length and the time period were obtained to describe the wave behavior in the near field and to quantify the wave amplitude decay away from the landslide source. The measured wave celerity of the leading wave corresponds well to the solitary wave speed while the trailing waves are considerably slower in propagation. The individual waves in the wave train span from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MMTA...47.2421W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MMTA...47.2421W"><span id="translatedtitle">Analysis of Slip Activity and <span class="hlt">Deformation</span> Modes in Tension and Tension-<span class="hlt">Creep</span> Tests of Cast Mg-10Gd-3Y-0.5Zr (Wt Pct) at Elevated Temperatures Using In Situ SEM Experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Huan; Boehlert, Carl J.; Wang, Qudong; Yin, Dongdi; Ding, Wenjiang</p> <p>2016-05-01</p> <p>The tension and tension-<span class="hlt">creep</span> <span class="hlt">deformation</span> behavior at elevated temperatures of a cast Mg-10Gd-3Y-0.5Zr (wt pct, GW103) alloy was investigated using in situ scanning electron microscopy. The tests were performed at temperatures ranging from 473 K to 598 K (200 °C to 325 °C). The active slip systems were identified using an EBSD-based slip trace analysis methodology. The results showed that for all of the tests, basal slip was the most likely system to be activated, and non-basal slip was activated to some extent depending on the temperature. No twinning was observed. For the tension tests, non-basal slip consisted of ~35 pct of the <span class="hlt">deformation</span> modes at low temperatures (473 K and 523 K (200 °C and 250 °C)), while non-basal slip accounted for 12 and 7 pct of the <span class="hlt">deformation</span> modes at high temperatures (573 K and 598 K (300 °C and 325 °C)), respectively. For the tension-<span class="hlt">creep</span> tests, non-basal slip accounted for 31 pct of the total slip systems at low temperatures, while this value decreased to 10 to 16 pct at high temperatures. For a given temperature, the relative activity for prismatic slip in the tension-<span class="hlt">creep</span> tests was slightly greater than that for the tension tests, while the activity for pyramidal slip was lower. Slip-transfer in neighboring grains was observed for the low-temperature tests. Intergranular cracking was the main cracking mode, while some intragranular cracks were observed for the tension-<span class="hlt">creep</span> tests at high temperature and low stress. Grain boundary ledges were prevalently observed for both the tension and tension-<span class="hlt">creep</span> tests at high temperatures, which suggests that besides dislocation slip, grain boundary sliding also contributed to the <span class="hlt">deformation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19750054660&hterms=waspaloy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dwaspaloy','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19750054660&hterms=waspaloy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dwaspaloy"><span id="translatedtitle"><span class="hlt">Deformation</span> <span class="hlt">characteristics</span> and time-dependent notch sensitivity of Udimet 700 at intermediate temperatures</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilson, D. J.</p> <p>1975-01-01</p> <p>Time-dependent notch sensitivity of Udimet 700 sheet, bar, and investment castings was observed between 1000 and 1400 F (538-760 C) but not at 1600 F (871 C). As was the case for Modified Waspaloy, Waspaloy, Rene 41, Inconel 718, and TD-NiCr, it occurred when notched specimens were loaded below the yield strength and when <span class="hlt">creep</span> <span class="hlt">deformation</span> was localized. For each gamma-prime strengthened alloy and notched specimen geometry, a stress-average particle size zone can be defined to characterize the notch-sensitive behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000SuScT..13..202Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000SuScT..13..202Y"><span id="translatedtitle">Current-voltage <span class="hlt">characteristics</span> and flux <span class="hlt">creep</span> in melt-textured YBa2Cu3O7-δ</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamasaki, H.; Mawatari, Y.</p> <p>2000-02-01</p> <p>We investigated the current-voltage (E - J) <span class="hlt">characteristics</span> in melt-textured YBa2Cu3O7-icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> strips by measuring the magnetic-field sweep rate dependence of magnetization. We took account of the current density J distribution in the specimen using a previously developed method (Mawatari Y et al 1997 Appl. Phys. Lett. 70 2300). For a wide temperature and magnetic-field range (60-80 K, 0.2-5.0 T), the E - J curves in the electric-field window E = 10-10 -10-5 V m-1 exhibited power-law behaviour E icons/Journals/Common/propto" ALT="propto" ALIGN="TOP"/> Jn, and the power index n generally became smaller at higher magnetic fields and temperatures. In low magnetic fields (µ0 Ha icons/Journals/Common/le" ALT="le" ALIGN="TOP"/> 0.5 T) the n values were large (icons/Journals/Common/ge" ALT="ge" ALIGN="TOP"/> 20), and thus the Bean model becomes a good approximation. The E - J <span class="hlt">characteristics</span> in the lower E window were also derived from the relaxation of magnetization, the flux <span class="hlt">creep</span>, and we found that the wide-range E - J <span class="hlt">characteristics</span> exhibit near-power-law behaviour but that there exist slight downward curvatures in the log E versus log J plots. This downward curvature reveals that the dissipation approaches zero when the current is substantially reduced. The drastic decrease of the flux <span class="hlt">creep</span>, which was observed when the sample temperature was decreased in a fixed magnetic field, is consistent with the observed E - J <span class="hlt">characteristics</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22163132','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22163132"><span id="translatedtitle">Microstructure and <span class="hlt">creep</span> <span class="hlt">characteristics</span> of dissimilar T91/TP316H martensitic/austenitic welded joint with Ni-based weld metal</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Falat, Ladislav; Svoboda, Milan; Vyrostkova, Anna; Petryshynets, Ivan; Sopko, Martin</p> <p>2012-10-15</p> <p>This paper deals with characterization of microstructure and <span class="hlt">creep</span> behavior of dissimilar weldment between the tempered martensitic steel T91 and the non-stabilized austenitic steel TP316H with Ni-based weld metal (Ni WM). Microstructure analyses were performed using light microscopy, scanning and transmission electron microscopy and energy-dispersive X-ray spectroscopy. The martensitic part of the welded joint exhibited a wide heat-affected zone (HAZ) with typical microstructural gradient from its coarse-grained to the fine-grained/intercritical region. In contrast, the HAZ of austenitic steel was limited to only a narrow region with coarsened polygonal grains. The microstructure of Ni WM was found to be very heterogeneous with respect to the size, morphology and distribution of grain boundaries and MC-type precipitates as a result of strong weld metal dilution effects and fast non-equilibrium solidification. Cross-weld <span class="hlt">creep</span> tests were carried out in a temperature range from 600 to 650 Degree-Sign C at applied stresses from 60 to 140 MPa. The obtained values of apparent stress exponents and <span class="hlt">creep</span> activation energies indicate thermally activated dislocation glide to be the governing <span class="hlt">creep</span> <span class="hlt">deformation</span> mechanism within the range of used testing conditions. The <span class="hlt">creep</span> samples ruptured in the T91 intercritical HAZ region by the 'type IV cracking' failure mode and the <span class="hlt">creep</span> fracture mechanism was identified to be the intergranular dimple tearing by microvoid coalescence at grain boundaries. The TEM observations revealed pronounced microstructural differences between the critical HAZ region and the T91 base material before as well as after the <span class="hlt">creep</span> exposure. - Highlights: Black-Right-Pointing-Pointer Phase transformations affect the microstructures of T91 and TP316H HAZ regions. Black-Right-Pointing-Pointer High weld metal dilution results in heterogeneous microstructure with MC carbides. Black-Right-Pointing-Pointer <span class="hlt">Creep</span> behavior of the studied weldment is controlled</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27198891','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27198891"><span id="translatedtitle">Clinical, angiographic and procedural <span class="hlt">characteristics</span> of longitudinal stent <span class="hlt">deformation</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Guler, A; Guler, Y; Acar, E; Aung, S M; Efe, S C; Kilicgedik, A; Karabay, C Y; Barutcu, S; Tigen, M K; Pala, S; İzgi, A; Esen, A M; Kirma, C</p> <p>2016-08-01</p> <p>Recently, longitudinal stent <span class="hlt">deformation</span> (LSD) has been reported increasingly. Even though the reported cases included almost all stent designs, most cases were seen in the Element™ stent design (Boston Scientific, Natick, MA, USA). It is considered that stent design, lesion and procedural <span class="hlt">characteristics</span> play a role in the etiology of LSD. Yet, the effect of LSD on long-term clinical outcomes has not been studied well. Element stents implanted between January 2013 and April 2015 in our hospital were examined retrospectively. Patients were grouped into two according to the presence of LSD, and their clinical, lesion and procedural <span class="hlt">characteristics</span> were studied. Twenty-four LSD's were detected in 1812 Element stents deployed in 1314 patients (1.83 % of PCI cases and 1.32 % of all Element stents). LMCA lesions (16.7 % vs 1.6 %, p < 0.001), complex lesions (75 % vs 35.1 %, p < 0.001), bifurcation lesions (37.5 % vs 18.3 %, p = 0.017), ostial lesions (33.3 % vs 12.8 %, p = 0.003), using of extra-support guiding catheter (54.2 % vs 22.3 %, p < 0.001) and extra-support guidewire (37.5 % vs 16.2 %, p = 0.005) were found to be more frequent in cases with LSD than in cases without it. In addition, the number of stents, stent inflation pressure and the use of post-dilatation were significantly different between the two groups. Two patients had an adverse event during the follow-up period. LSD is a rarely encountered complication, and is more common in complex lesions such as ostial, bifurcation and LMCA lesions. The use of extra-support guiding catheter, extra-support guidewires and low stent inflation pressure increases the occurrence of LSD. Nevertheless, with increased awareness of LSD and proper treatment, unwanted long-term outcomes can be successfully prevented. PMID:27198891</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19990008062&hterms=B12&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DB12','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19990008062&hterms=B12&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DB12"><span id="translatedtitle">Transient <span class="hlt">Creep</span> of a Composite Lower Crust. 2; A Polymineralic Basis for Rapidly Evolving Postseismic <span class="hlt">Deformation</span> Modes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ivins, Erik R.</p> <p>1996-01-01</p> <p>Postseismic horizontal strain and displacement following the June 28, 1992, Landers, California, earthquake (M(sub W) 7.3) is broad scale and cannot be explained solely by delayed afterslip located at the rupturing fault trace. Both the observed strain at Pifion Flat Observatory (PFO) and observed Global Positioning System receiver velocities evolve rapidly after the Landers-Big Bear earthquake sequence. The observed exponential decay of these motions, with timescales of 4-34 days, may reflect a soft <span class="hlt">creep</span> rheology in the lower crust and brittle-ductile transition zone or even within the seismogenic crust itself. Here a simple model of a two-dimensional screw dislocation in a layered Maxwell viscoelastic Earth is employed in conjunction with a composite rheology to demonstrate that the short timescale transient response modes (approx. = 4-34 days) are consistent with the behavior of a biviscous lower crust. The lowest viscosity of this system is derivable from laboratory experimental data on the long-term <span class="hlt">creep</span> of natural quarztites, and the highest viscosity is consistent with isostasy-related lower crustal flow in a continental extensional tectonic environment. The model predicts significant stress relaxation at the base of the seismogenic crust. Near the base of the seismogenic zone, and about 4 km away from the mainshock, the rate of predicted relaxation is of the order of 0.01 MPa/ d during the first 20 days of postseismic flow. Oblate spheroidal inclusions at 5% concentration levels that are both aligned and fairly flat in shape and that have a viscosity of 3-4 x 10(exp 15) Pa s are consistent with both the amplitude and decay time of horizontal crustal strain observed at PFO after the Landers mainshock. It is speculated that the structures exposed in cross sections and in seismic reflection profiles of the lower crust that have mylonitic associations are, in part, the cause of such rapid postseismic evolution in southeastern California. Unmylonitized quartz</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ApPhA.122..715L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ApPhA.122..715L&link_type=ABSTRACT"><span id="translatedtitle">Non-instantaneous growth <span class="hlt">characteristics</span> of martensitic transformation in high Cr ferritic <span class="hlt">creep</span>-resistant steel</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Chenxi; Shao, Yi; Chen, Jianguo; Liu, Yongchang</p> <p>2016-08-01</p> <p>Microstructural observation and high-resolution dilatometry were employed to investigate kinetics of martensitic transformation in high Cr ferritic <span class="hlt">creep</span>-resistant steel upon different quenching/cooling rates. By incorporating the classical athermal nucleation and impingement correction, a non-instantaneous growth model for martensitic transformation has been developed. The developed model describes austenite/martensite interface mobility during martensite growth. The growth rate of martensite is found to be varied from 1 × 10-6 to 3 × 10-6 m/s. The low interface mobility suggests that it is not appropriate to presume the instantaneous growth behavior of martensite. Moreover, based on the proposed model, nucleation rate of martensite under different cooling rates is found to be nearly the same, while the growth rate of martensite is promoted by increasing the cooling rate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5901443','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5901443"><span id="translatedtitle"><span class="hlt">Creep</span> and <span class="hlt">creep</span>-rupture behavior of Alloy 718</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Brinkman, C.R.; Booker, M.K.; Ding, J.L.</p> <p>1991-01-01</p> <p>Data obtained from <span class="hlt">creep</span> and <span class="hlt">creep</span>-rupture tests conducted on 18 heats of Alloy 718 were used to formulate models for predicting high temperature time dependent behavior of this alloy. <span class="hlt">Creep</span> tests were conducted on specimens taken from a number of commercial product forms including plate, bar, and forgoing material that had been procured and heat treated in accordance with ASTM specifications B-670 or B-637. Data were obtained over the temperature range of 427 to 760{degree}C ad at test times to about 87,000 h. Comparisons are given between experimental data and the analytical models. The analytical models for <span class="hlt">creep</span>-rupture included one based on lot-centering regression analysis and two based on the Minimum Commitment Method. A master'' curve approach was used to develop and equation for estimating <span class="hlt">creep</span> <span class="hlt">deformation</span> up to the onset of tertiary <span class="hlt">creep</span>. 11 refs., 13 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993IJIMW..14.1717Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993IJIMW..14.1717Y&link_type=ABSTRACT"><span id="translatedtitle">The effect of electron beam geometric <span class="hlt">deformation</span> errors on the small-signal <span class="hlt">characteristic</span> of ECRM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yongjian, Yu</p> <p>1993-08-01</p> <p>In this paper is studied the effect of electron beam geometric <span class="hlt">deformation</span> errors on the small — signal <span class="hlt">characteristics</span> of the TE{mn/o} mode Electron Cyclotron Resonance Maser (ECRM), based on the elliptically cross—sectional e—beam <span class="hlt">deformation</span> model. As an example, the effect of small geometric <span class="hlt">deformation</span> errors on the TE{01/o} mode fundamental ECRM coupling coefficient is quantitatively shown.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRB..120..827F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRB..120..827F"><span id="translatedtitle">Micromechanisms of <span class="hlt">creep</span> in clay-rich gouge from the Central <span class="hlt">Deforming</span> Zone of the San Andreas Fault</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>French, M. E.; Chester, F. M.; Chester, J. S.</p> <p>2015-02-01</p> <p>We report the strength and constitutive behavior of gouge sampled from the Central <span class="hlt">Deforming</span> Zone (CDZ) of the San Andreas Fault. Layers of flaked CDZ gouge were sheared in the triaxial saw cut configuration using the stress relaxation technique to measure the gouge strength over 4 orders of magnitude in shear strain rate and at rates as low as 5 × 10-10s-1 and within an order of magnitude of in situ rates. <span class="hlt">Deformation</span> conditions correspond to the in situ effective normal stress (100 MPa) and temperature (65 to 120°C) at the sampling depth of 2.7 km. Gouge was sheared dry and with brine pore fluid at 25 MPa pore pressure. Dry gouge is stronger and more rate strengthening than brine-saturated gouge. Brine-saturated CDZ gouge strengthens with increasing strain rate and decreasing temperature, and the dependencies of strength on strain rate and temperature increase at rates below ˜5 × 10-9s-1. At strain rates greater than ˜5 × 10-9s-1, the rate dependence is consistent with previous studies on the CDZ gouge conducted at even higher rates. The increase in rate dependence below ˜5 × 10-9s-1 indicates a change in the rate-controlling <span class="hlt">deformation</span> mechanism. The magnitude of the friction rate dependence parameter, a, and the temperature sensitivity of a are consistent with crystal plasticity of the phyllosilicates. We hypothesize a micromechanical model for the CDZ gouge whereby a transition from fracture and delamination-accommodated frictional flow to crystal plasticity-accommodated frictional flow occurs with decreasing strain rate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015MMTA..tmp..525W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015MMTA..tmp..525W&link_type=ABSTRACT"><span id="translatedtitle">Fracture Morphology and Local <span class="hlt">Deformation</span> <span class="hlt">Characteristics</span> in the Metallic Glass Matrix Composite Under Tension</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Y. S.; Sun, X. H.; Hao, G. J.; Guo, Z. X.; Zhang, Y.; Lin, J. P.; Sui, M. L.; Qiao, J. W.</p> <p>2015-11-01</p> <p>Fracture and <span class="hlt">deformation</span> <span class="hlt">characteristics</span> of the Ti-based metallic glass matrix composite have been studied by the tensile test and the in situ TEM tension test. Typically, the composite exhibits the high strength and considerable plasticity. Microscopically, it was found that shear <span class="hlt">deformation</span> zone formed at the crack tip in glass phase, which can bring about quick propagation of shear bands. However, the plastic <span class="hlt">deformation</span> zone nearby the crack tip in dendrites will postpone or retard the crack extension by dislocations. The attributions of micro-<span class="hlt">deformations</span> to mechanical properties of composites were discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930063288&hterms=blade+shape+edge&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dblade%2Bshape%2Bedge','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930063288&hterms=blade+shape+edge&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dblade%2Bshape%2Bedge"><span id="translatedtitle"><span class="hlt">Characteristics</span> of <span class="hlt">deformable</span> leading edge for high performance helicopter rotor</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lee, Soogab; Mcalister, K. W.; Tung, Chee</p> <p>1993-01-01</p> <p>The <span class="hlt">deformable</span> leading edge (DLE) concept to improve the blade capability in lift, drag and pitching moments has been investigated for the purpose of meeting new rotor maneuverability and susceptibility requirements. The advantages and disadvantages of this concept have been carefully examined with limited computational and experimental results. This work showed that this concept achieves a substantial improvement in lift capability and also reduces the drag and pitching moment at the same time. Effects of various parameters, such as Reynolds number, reduced frequency, mean angle of oscillation, and airfoil shape, on the performance of these airfoils were also investigated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001JGR...10613443B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001JGR...10613443B"><span id="translatedtitle"><span class="hlt">Creep</span> of dry clinopyroxene aggregates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bystricky, Misha; Mackwell, Stephen</p> <p>2001-01-01</p> <p>We have determined diffusional and dislocation <span class="hlt">creep</span> rheologies for clinopyroxenite Ca1.0Mg0.8Fe0.2Si2O6 under dry conditions by <span class="hlt">deforming</span> natural and hot-pressed samples at confining pressures of 300-430 MPa and temperatures of 1100°-1250°C with the oxygen fugacity buffered by either nickel-nickel oxide or iron-wüstite powders. The coarse-grained natural Sleaford Bay clinopyroxenite yielded a stress exponent of n = 4.7 ± 0.2 and an activation energy for <span class="hlt">creep</span> of Q = 760 ± 40 kJ mol-1, consistent with <span class="hlt">deformation</span> in the dislocation <span class="hlt">creep</span> regime. The strength of the natural clinopyroxenite is consistent with previous high-temperature measurements of dislocation <span class="hlt">creep</span> behavior of Sleaford Bay clinopyroxenite by Kirby and Kronenberg [1984] and Boland and Tullis [1986]. Fine-grained clinopyroxenite was prepared from ground powders of the natural clinopyroxenite. Hot-pressed samples were <span class="hlt">deformed</span> under similar conditions to the natural samples. Mixed-mode <span class="hlt">deformation</span> behavior was observed, with diffusional <span class="hlt">creep</span> (n = 1) at lower differential stresses and dislocation <span class="hlt">creep</span> (with n and Q similar to those of the natural samples) at higher differential stresses. Within the dislocation <span class="hlt">creep</span> field the predried hot-pressed samples generally yielded <span class="hlt">creep</span> rates that were about an order of magnitude faster than the natural samples. Thus, even at the highest differential stresses, a component of strain accommodation by grain boundary diffusion was present in the hot-pressed samples. Optical and electron microscope investigations of the <span class="hlt">deformation</span> microstructures of the natural and hot-pressed samples show evidence for mechanical twinning and activation of dislocation slip systems. When extrapolated to geological conditions expected in the deep crust and upper mantle on Earth and other terrestrial planets, the strength of dry single-phase clinopyroxene aggregates is very high, exceeding that of dry olivine-rich rocks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MMTA...45..343Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MMTA...45..343Z"><span id="translatedtitle">Tensile Properties and <span class="hlt">Deformation</span> <span class="hlt">Characteristics</span> of a Ni-Fe-Base Superalloy for Steam Boiler Applications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhong, Zhihong; Gu, Yuefeng; Yuan, Yong; Shi, Zhan</p> <p>2014-01-01</p> <p>Ni-Fe-base superalloys due to their good manufacturability and low cost are the proper candidates for boiler materials in advanced power plants. The major concerns with Ni-Fe-base superalloys are the insufficient mechanical properties at elevated temperatures. In this paper, tensile properties, <span class="hlt">deformation</span>, and fracture <span class="hlt">characteristics</span> of a Ni-Fe-base superalloy primarily strengthened by γ' precipitates have been investigated from room temperature to 1073 K (800 °C). The results showed a gradual decrease in the strength up to about 973 K (700 °C) followed by a rapid drop above this temperature and a ductility minimum at around 973 K (700 °C). The fracture surfaces were studied using scanning electron microscopy and the <span class="hlt">deformation</span> mechanisms were determined by the observation of <span class="hlt">deformed</span> microstructures using transmission electron microscopy. An attempt has been made to correlate the tensile properties and fracture <span class="hlt">characteristics</span> at different temperatures with the observed <span class="hlt">deformation</span> mechanisms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/605795','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/605795"><span id="translatedtitle">The influence of magnesium on carbide <span class="hlt">characteristics</span> and <span class="hlt">creep</span> behavior of the Mar-M247 superalloy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bor, H.Y.; Chao, C.G.; Ma, C.Y.</p> <p>1997-12-22</p> <p>In recent investigations, it has been shown that the microaddition of Mg in wrought superalloys significantly enhances stress rupture life, ductility and fatigue endurance at elevated temperatures. These improvements are mainly associated with carbide refinement arising from segregation of Mg to GB and carbide/matrix interface. Although, some studies related to Mg segregation phenomenon have been carried out, the true mechanisms are not fully understood. Furthermore, little work has been reported in introducing Mg as a microalloying element in cast superalloys which are normally poor in ductility and toughness at both room and elevated temperatures. On this basis, Mar-M247 superalloy was chosen for the first time in this work for studying the influence of Mg microaddition on high temperature properties. The objectives of present study were to determine the microstructural <span class="hlt">characteristics</span> and to investigate the <span class="hlt">creep</span> behavior of Mar-M247 superalloy due to the microaddition of Mg, particularly in ductility. In addition, some available mechanisms associated with the microstructure change and property enhancement were discussed in this paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MMTA...46.1843L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MMTA...46.1843L"><span id="translatedtitle">Precipitation Behavior in the Heat-Affected Zone of Boron-Added 9Cr-3W-3Co Steel During Post-Weld Heat Treatment and <span class="hlt">Creep</span> <span class="hlt">Deformation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Yuan; Tsukamoto, Susumu; Sawada, Kota; Tabuchi, Masaaki; Abe, Fujio</p> <p>2015-05-01</p> <p>In the previous paper, we demonstrated that the addition of boron was effective in preventing type IV failure due to suppression of grain refinement in the heat-affected zone at the peak temperature of around AC3 (AC3 HAZ). However, some fine prior austenite grains (PAGs) still remained around the coarse PAG boundaries, and these fine PAGs may affect the <span class="hlt">creep</span> property of the welded joint. In the present study, the effect of these fine PAGs on the <span class="hlt">creep</span> property of the boron-added 9Cr-3Co-3W steel (B steel) Ac3 HAZ is investigated. Different heat treatments are carried out on B steel base metal to form different Ac3 HAZ-simulated microstructures of coarse PAG with and without fine PAGs. Ac3 HAZ microstructure shows that a lot of M23C6 carbides are formed at the block boundary in the interior of coarse PAG. On the other hand, few M23C6 carbides are formed at the fine PAG boundaries, but a number of μ phases (W6Fe7 type) cover the boundary. The formation of μ phase retards the recovery of dislocation at the fine PAG boundary and contributes to stabilizing the microstructure in the primary and transient <span class="hlt">creep</span> regions. The μ phase transforms to the Laves phase during <span class="hlt">creep</span>. As the growth rate of Laves phase is higher than that of M23C6 carbides during <span class="hlt">creep</span>, the <span class="hlt">creep</span> strength of fine PAG boundary, which is strengthened only by Laves phase, becomes a little bit lower than the other boundaries strengthened by M23C6 carbides after long-term <span class="hlt">creep</span>. The mismatch of <span class="hlt">creep</span> strength between the fine PAG boundary and the matrix should be taken into account to attain an excellent long-term <span class="hlt">creep</span> property of the B steel welded joint.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22403525','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22403525"><span id="translatedtitle">Powder metallurgy processing and <span class="hlt">deformation</span> <span class="hlt">characteristics</span> of bulk multimodal nickel</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Farbaniec, L.; Dirras, G.; Krawczynska, A.; Mompiou, F.; Couque, H.; Naimi, F.; Bernard, F.; Tingaud, D.</p> <p>2014-08-15</p> <p>Spark plasma sintering was used to process bulk nickel samples from a blend of three powder types. The resulting multimodal microstructure was made of coarse (average size ∼ 135 μm) spherical microcrystalline entities (the core) surrounded by a fine-grained matrix (average grain size ∼ 1.5 μm) or a thick rim (the shell) distinguishable from the matrix. Tensile tests revealed yield strength of ∼ 470 MPa that was accompanied by limited ductility (∼ 2.8% plastic strain). Microstructure observation after testing showed debonding at interfaces between the matrix and the coarse entities, but in many instances, shallow dimples within the rim were observed indicating local ductile events in the shell. Dislocation emission and annihilation at grain boundaries and twinning at crack tip were the main <span class="hlt">deformation</span> mechanisms taking place within the fine-grained matrix as revealed by in-situ transmission electron microscopy. Estimation of the stress from loop's curvature and dislocation pile-up indicates that dislocation emission from grain boundaries and grain boundary overcoming largely contributes to the flow stress. - Highlights: • Bulk multi-modal Ni was processed by SPS from a powder blend. • Ultrafine-grained matrix or rim observed around spherical microcrystalline entities • Yield strength (470 MPa) and ductility (2.8% plastic strain) were measured. • Debonding was found at the matrix/microcrystalline entity interfaces. • In-situ TEM showed twinning, dislocation emission and annihilation at grain boundaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19990005979','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990005979"><span id="translatedtitle">Deterministic and Probabilistic <span class="hlt">Creep</span> and <span class="hlt">Creep</span> Rupture Enhancement to CARES/<span class="hlt">Creep</span>: Multiaxial <span class="hlt">Creep</span> Life Prediction of Ceramic Structures Using Continuum Damage Mechanics and the Finite Element Method</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jadaan, Osama M.; Powers, Lynn M.; Gyekenyesi, John P.</p> <p>1998-01-01</p> <p>High temperature and long duration applications of monolithic ceramics can place their failure mode in the <span class="hlt">creep</span> rupture regime. A previous model advanced by the authors described a methodology by which the <span class="hlt">creep</span> rupture life of a loaded component can be predicted. That model was based on the life fraction damage accumulation rule in association with the modified Monkman-Grant <span class="hlt">creep</span> ripture criterion However, that model did not take into account the deteriorating state of the material due to <span class="hlt">creep</span> damage (e.g., cavitation) as time elapsed. In addition, the material <span class="hlt">creep</span> parameters used in that life prediction methodology, were based on uniaxial <span class="hlt">creep</span> curves displaying primary and secondary <span class="hlt">creep</span> behavior, with no tertiary regime. The objective of this paper is to present a <span class="hlt">creep</span> life prediction methodology based on a modified form of the Kachanov-Rabotnov continuum damage mechanics (CDM) theory. In this theory, the uniaxial <span class="hlt">creep</span> rate is described in terms of stress, temperature, time, and the current state of material damage. This scalar damage state parameter is basically an abstract measure of the current state of material damage due to <span class="hlt">creep</span> <span class="hlt">deformation</span>. The damage rate is assumed to vary with stress, temperature, time, and the current state of damage itself. Multiaxial <span class="hlt">creep</span> and <span class="hlt">creep</span> rupture formulations of the CDM approach are presented in this paper. Parameter estimation methodologies based on nonlinear regression analysis are also described for both, isothermal constant stress states and anisothermal variable stress conditions This <span class="hlt">creep</span> life prediction methodology was preliminarily added to the integrated design code CARES/<span class="hlt">Creep</span> (Ceramics Analysis and Reliability Evaluation of Structures/<span class="hlt">Creep</span>), which is a postprocessor program to commercially available finite element analysis (FEA) packages. Two examples, showing comparisons between experimental and predicted <span class="hlt">creep</span> lives of ceramic specimens, are used to demonstrate the viability of this methodology and</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JNuM..416..273G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JNuM..416..273G"><span id="translatedtitle">Microstructural degradation mechanisms during <span class="hlt">creep</span> in strength enhanced high Cr ferritic steels and their evaluation by hardness measurement</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghassemi Armaki, Hassan; Chen, Ruiping; Kano, Satoshi; Maruyama, Kouichi; Hasegawa, Yasushi; Igarashi, Masaaki</p> <p>2011-09-01</p> <p>There are two <span class="hlt">creep</span> regions with different <span class="hlt">creep</span> <span class="hlt">characteristics</span>: short-term <span class="hlt">creep</span> region "H", where precipitates and subgrains are thermally stable, and long-term <span class="hlt">creep</span> region "L", where thermal coarsening of precipitates and subgrains appear. In region "H", the normalized subgrain size (λ-λ0)/(λ∗-λ0) has a linear relation with <span class="hlt">creep</span> strain and its slope is 10 ɛ-1. But, region L is the time range in which the static recovery and the strain-induced recovery progress simultaneously. In this region, the static recovery accelerates the strain-induced recovery, and subgrain size is larger than that line which neglects the contribution of the static recovery. In region "L", the Δλ/Δλ∗-strain present a linear relation with a slope 35 ɛ-1. There is a linear relation between hardness and subgrain size. Hardness drop, H0 - H, as a function of Larson-Miller parameter can be a good measure method for assessment of hardness drop and consequently degradation of microstructure. Hardness drop shows an identical slope in <span class="hlt">creep</span> region "H", whereas hardness drop due to thermal aging and <span class="hlt">creep</span> in region "L" show together a similar slope. In region "H", degradation of microstructure is mainly due to recovery of subgrains controlled by <span class="hlt">creep</span> plastic <span class="hlt">deformation</span>, and precipitates do not have a major role. However, in <span class="hlt">creep</span> region "L", there are three degradation mechanisms that accelerate <span class="hlt">creep</span> failure; (1) strain-induced recovery of subgrains due to <span class="hlt">creep</span> plastic <span class="hlt">deformation</span>, (2) static-recovery of subgrains and precipitates and (3) strain-induced coarsening of precipitates due to the appearance of static-recovery.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19541652','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19541652"><span id="translatedtitle">Nanogranular origin of concrete <span class="hlt">creep</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vandamme, Matthieu; Ulm, Franz-Josef</p> <p>2009-06-30</p> <p>Concrete, the solid that forms at room temperature from mixing Portland cement with water, sand, and aggregates, suffers from time-dependent <span class="hlt">deformation</span> under load. This <span class="hlt">creep</span> occurs at a rate that deteriorates the durability and truncates the lifespan of concrete structures. However, despite decades of research, the origin of concrete <span class="hlt">creep</span> remains unknown. Here, we measure the in situ <span class="hlt">creep</span> behavior of calcium-silicate-hydrates (C-S-H), the nano-meter sized particles that form the fundamental building block of Portland cement concrete. We show that C-S-H exhibits a logarithmic <span class="hlt">creep</span> that depends only on the packing of 3 structurally distinct but compositionally similar C-S-H forms: low density, high density, ultra-high density. We demonstrate that the <span class="hlt">creep</span> rate ( approximately 1/t) is likely due to the rearrangement of nanoscale particles around limit packing densities following the free-volume dynamics theory of granular physics. These findings could lead to a new basis for nanoengineering concrete materials and structures with minimal <span class="hlt">creep</span> rates monitored by packing density distributions of nanoscale particles, and predicted by nanoscale <span class="hlt">creep</span> measurements in some minute time, which are as exact as macroscopic <span class="hlt">creep</span> tests carried out over years. PMID:19541652</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2705587','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2705587"><span id="translatedtitle">Nanogranular origin of concrete <span class="hlt">creep</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Vandamme, Matthieu; Ulm, Franz-Josef</p> <p>2009-01-01</p> <p>Concrete, the solid that forms at room temperature from mixing Portland cement with water, sand, and aggregates, suffers from time-dependent <span class="hlt">deformation</span> under load. This <span class="hlt">creep</span> occurs at a rate that deteriorates the durability and truncates the lifespan of concrete structures. However, despite decades of research, the origin of concrete <span class="hlt">creep</span> remains unknown. Here, we measure the in situ <span class="hlt">creep</span> behavior of calcium–silicate–hydrates (C–S–H), the nano-meter sized particles that form the fundamental building block of Portland cement concrete. We show that C–S–H exhibits a logarithmic <span class="hlt">creep</span> that depends only on the packing of 3 structurally distinct but compositionally similar C–S–H forms: low density, high density, ultra-high density. We demonstrate that the <span class="hlt">creep</span> rate (≈1/t) is likely due to the rearrangement of nanoscale particles around limit packing densities following the free-volume dynamics theory of granular physics. These findings could lead to a new basis for nanoengineering concrete materials and structures with minimal <span class="hlt">creep</span> rates monitored by packing density distributions of nanoscale particles, and predicted by nanoscale <span class="hlt">creep</span> measurements in some minute time, which are as exact as macroscopic <span class="hlt">creep</span> tests carried out over years. PMID:19541652</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1077140','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1077140"><span id="translatedtitle">1/2 <span class="hlt">CREEP</span> FRACTURE IN CERAMIC POLYCRYSTALS I. <span class="hlt">CREEP</span> CAVITATION EFFECTS IN POLYCRYSTALLINE ALUMINA</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Porter, J. R.; Blumenthal, W.; Evans, A. G.</p> <p>1980-09-01</p> <p>Fine grained polycrystalline alumina has been <span class="hlt">deformed</span> in <span class="hlt">creep</span> at high temperatures, to examine the evolution of cavities at grain boundaries. Cavities with equilibrium and crack-like morphologies have been observed, distributed non-uniformly throughout the material. The role of cavities during <span class="hlt">creep</span> has been described. A transition from equilibrium to crack-like morphology has been observed and correlated with a model based on the influence of the surface to boundary diffusivity ratio and the local tensile stress. The contribution of cavitation to the <span class="hlt">creep</span> rate and total <span class="hlt">creep</span> strain has been analyzed and excluded as the principal cause of the observed non-linear <span class="hlt">creep</span> rate,</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012APS..MART45010T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012APS..MART45010T"><span id="translatedtitle">Heterogeneous Dynamics During <span class="hlt">Creep</span> of Rod Containing Polymer Nanocomposites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Toepperwein, Gregory; Riggleman, Robert; de Pablo, Juan</p> <p>2012-02-01</p> <p>Polymer glasses exhibit regions of locally higher or lower mobility leading to heterogeneous dynamics. While heterogeneous dynamics have been examined in some detail in pure polymers, less is known about polymer nanocomposites (PNCs). We have previously studied PNCs, providing descriptions of how particles alter the network of entanglements, measuring local mechanical heterogeneity, demonstrating strain response under uniaxial <span class="hlt">deformation</span>, and examining crazing and failure under multiaxial <span class="hlt">deformation</span>. In the present work, we examine dynamic heterogeneity in rod-containing PNCs by performing <span class="hlt">creep</span> <span class="hlt">deformation</span> simulations and monitoring several measures of mobility. We are able to directly probe how dynamic heterogeneity evolves during <span class="hlt">deformation</span>, and explore the origins of molecular mobility in polymer glasses. Examination of the segmental motion of a PNC undergoing <span class="hlt">creep</span> reveals that the glassy heterogeneity of these systems decreases significantly following the onset of flow. It is found that the more heterogeneous distribution of relaxation times <span class="hlt">characteristic</span> of PNCs in the bulk remains unaltered regardless of <span class="hlt">deformation</span> state. It is found that the mobility and heterogeneity of PNCs are less susceptible to change upon <span class="hlt">deformation</span> than those for the pure polymer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015EGUGA..17.7358P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015EGUGA..17.7358P&link_type=ABSTRACT"><span id="translatedtitle">Utilizing microstructural <span class="hlt">characteristics</span> to derive insights into <span class="hlt">deformation</span> and annealing behaviour: Numerical simulations, experiments and nature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Piazolo, Sandra; Montagnat, Maurine; Prakash, Abhishek; Borthwick, Verity; Evans, Lynn; Griera, Albert; Bons, Paul D.; Svahnberg, Henrik; Prior, David J.</p> <p>2015-04-01</p> <p>Understanding the influence of the pre-existing microstructure on subsequent microstructural development is pivotal for the correct interpretation of rocks and ice that stayed at high homologous temperatures over a significant period of time. The microstructural behaviour of these materials through time has an important bearing on the interpretation of <span class="hlt">characteristics</span> such as grain size, for example, using grain size statistics to detect former high strain zones that remain at high temperatures but low stress. We present a coupled experimental and modelling approach to better understand the evolution of recrystallization <span class="hlt">characteristics</span> as a function of <span class="hlt">deformation</span>-annealing time paths in a material with a high viscoplastic anisotropy e.g. polycrystalline ice and magnesium alloys. <span class="hlt">Deformation</span> microstructures such as crystal bending, subgrain boundaries, grain size variation significantly influence the <span class="hlt">deformation</span> and annealing behaviour of crystalline material. For numerical simulations we utilize the microdynamic modelling platform, Elle (www.elle.ws), taking local microstructural evolution into account to simulate the following processes: recovery within grains, rotational recrystallization, grain boundary migration and nucleation. We first test the validity of the numerical simulations against experiments, and then use the model to interpret microstructural features in natural examples. In-situ experiments are performed on laboratory grown and <span class="hlt">deformed</span> ice and magnesium alloy. Our natural example is a <span class="hlt">deformed</span> then recrystallized anorthosite from SW Greenland. The presented approach can be applied to many other minerals and crystalline materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.T43C3015K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.T43C3015K&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Creep</span> avalanches on the Central San Andreas Fault: Clues and Causes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khoshmanesh, M.; Shirzaei, M.; Nadeau, R. M.</p> <p>2015-12-01</p> <p>The Central segment of San Andreas Fault (CSAF) is characterized by a nearly continuous right-lateral aseismic slip. However, observations of the <span class="hlt">creep</span> rate obtained using <span class="hlt">Characteristically</span> Repeating Earthquakes (CREs) show a quasi-periodic temporal variation, which is recently confirmed using both InSAR surface <span class="hlt">deformation</span> time series and geodetic-based time-dependent kinematic model of <span class="hlt">creep</span> along the CSAF. Here, we show that the statistical analysis of <span class="hlt">creep</span> fronts along the CSAF indicates a sporadic behavior, signature of a burst-like <span class="hlt">creep</span> dynamics. Moreover, the probability of <span class="hlt">creep</span> velocities follows a Gumbel distribution characterized by longer tail toward the extreme positive rates. Fourier analysis of the time series of surface <span class="hlt">creep</span> rate indicates a self-affine regime with Hurst exponent altering between 0.6 and 0.9 during the observation period of 2003-2011. The variable Hurst component is an indicator for temporal variation in the roughness of the fault zone. To explain the causes of <span class="hlt">creep</span> avalanches, two possible mechanisms are considered, including temporal variation in: 1) fault geometry, and 2) Ambient normal stress. We find that the overall statistical dependence between the pattern of surface <span class="hlt">creep</span> rate and the fault geometry is insignificant. To investigate the effect of ambient normal stress, primarily due to variation in pore pressure, we implement a rate and state friction law to link the time-dependent kinematic <span class="hlt">creep</span> model to the spatiotemporal variations of the normal stress on the velocity-strengthening fault zones. These observations and models help to understand the driving mechanisms that govern the <span class="hlt">creep</span> rate variations at short spatial length and low velocities. Under these circumstances, the other mechanisms such as thermal pressurization are not feasible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/78368','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/78368"><span id="translatedtitle">The <span class="hlt">creep</span> <span class="hlt">deformation</span> and elevated temperature microstructural stability of a two-phase TiAl/Ti{sub 3}Al lamellar alloy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bartholomeusz, M.F.; Wert, J.A.</p> <p>1995-08-01</p> <p>Enhanced work hardening of the phases in the lamellar microstructure has been cited as an explanation for the lower minimum <span class="hlt">creep</span> rates of a two-phase TiAl/Ti{sub 3}Al lamellar alloy compared with the minimum <span class="hlt">creep</span> rates of the individual TiAl and Ti{sub 3}Al single-phase alloys tested between 980 K and 1,130 K. This proposition is confirmed by TEM observations. Thermal and thermomechanical exposure result in the microstructural evolution, which increases the minimum <span class="hlt">creep</span> rate ({dot {var_epsilon}}{sub min}) of the lamellar alloy. The effect of microstructural evolution on {dot {var_epsilon}}{sub min} will be discussed in the present paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16774517','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16774517"><span id="translatedtitle">EBSD investigation of the microstructure and texture <span class="hlt">characteristics</span> of hot <span class="hlt">deformed</span> duplex stainless steel.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cizek, P; Wynne, B P; Rainforth, W M</p> <p>2006-05-01</p> <p>The microstructure and crystallographic texture <span class="hlt">characteristics</span> were studied in a 22Cr-6Ni-3Mo duplex stainless steel subjected to plastic <span class="hlt">deformation</span> in torsion at a temperature of 1000 degrees C using a strain rate of 1 s(-1). High-resolution EBSD was successfully used for precise phase and substructural characterization of this steel. The austenite/ferrite ratio and phase morphology as well as the crystallographic texture, subgrain size, misorientation angles and misorientation gradients corresponding to each phase were determined over large sample areas. The <span class="hlt">deformation</span> mechanisms in each phase and the interrelationship between the two are discussed. PMID:16774517</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhyC..523...10M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhyC..523...10M"><span id="translatedtitle">Vortex and <span class="hlt">characteristics</span> of prestrained type-II <span class="hlt">deformable</span> superconductors under magnetic fields</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Zeling; Wang, Xingzhe; Zhou, Youhe</p> <p>2016-04-01</p> <p>Based on the time-dependent Ginzburg-Landau (TDGL) theory and the linear <span class="hlt">deformation</span> theory, we present a numerical investigation of magnetic vortex <span class="hlt">characteristics</span> of a type-II <span class="hlt">deformable</span> superconductor with prestrain. The effect of prestrain on the wave function, vortex dynamics and energy density of a superconducting film is analyzed by solving the nonlinear TDGL equations in the presence of magnetic field. The results show that the prestrain has a remarkable influence on the magnetic vortex distribution and the vortex dynamics, as well as value of wave function of the superconductor. The different prestrains, i.e., pre-given compression and tension strains, result in dissimilar <span class="hlt">characteristics</span> on a half-plane of <span class="hlt">deformable</span> superconductor in an applied magnetic field, and the vortex distribution and entrance in a two dimensional superconducting film. The studies demonstrated that the compression prestrain may speed up the vortexes entering into the region of the superconducting film and increases the vortex number in comparison with those of free-prestrain case, while the tension prestrain shows the reversal features. The energy density and spectrum in the superconductor are further demonstrated numerically and discussed. The present investigation is an attempt to give insight into the superconductivity and electromagnetic <span class="hlt">characteristics</span> taking into account the elastic <span class="hlt">deformation</span> in superconductors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008IJMPB..22.6161F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008IJMPB..22.6161F"><span id="translatedtitle">Homogenized <span class="hlt">Creep</span> Behavior of CFRP Laminates at High Temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fukuta, Y.; Matsuda, T.; Kawai, M.</p> <p></p> <p>In this study, <span class="hlt">creep</span> behavior of a CFRP laminate subjected to a constant stress is analyzed based on the time-dependent homogenization theory developed by the present authors. The laminate is a unidirectional carbon fiber/epoxy laminate T800H/#3631 manufactured by Toray Industries, Inc. Two kinds of <span class="hlt">creep</span> analyses are performed. First, 45° off-axis <span class="hlt">creep</span> <span class="hlt">deformation</span> of the laminate at high temperature (100°C) is analyzed with three kinds of <span class="hlt">creep</span> stress levels, respectively. It is shown that the present theory accurately predicts macroscopic <span class="hlt">creep</span> behavior of the unidirectional CFRP laminate observed in experiments. Then, high temperature <span class="hlt">creep</span> <span class="hlt">deformations</span> at a constant <span class="hlt">creep</span> stress are simulated with seven kinds of off-axis angles, i.e., θ = 0°, 10°, 30°, 45°, 60°, 75°, 90°. It is shown that the laminate has marked in-plane anisotropy with respect to the <span class="hlt">creep</span> behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19750059599&hterms=Uranium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DUranium','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19750059599&hterms=Uranium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DUranium"><span id="translatedtitle"><span class="hlt">Creep</span> behavior of uranium carbide-based alloys</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Seltzer, M. S.; Wright, T. R.; Moak, D. P.</p> <p>1975-01-01</p> <p>The present work gives the results of experiments on the influence of zirconium carbide and tungsten on the <span class="hlt">creep</span> properties of uranium carbide. The <span class="hlt">creep</span> behavior of high-density UC samples follows the classical time-dependence pattern of (1) an instantaneous <span class="hlt">deformation</span>, (2) a primary <span class="hlt">creep</span> region, and (3) a period of steady-state <span class="hlt">creep</span>. <span class="hlt">Creep</span> rates for unalloyed UC-1.01 and UC-1.05 are several orders of magnitude greater than those measured for carbide alloys containing a Zr-C and/or W dispersoid. The difference in <span class="hlt">creep</span> strength between alloyed and unalloyed materials varies with temperature and applied stress.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22254042','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22254042"><span id="translatedtitle">Electrochemical control of <span class="hlt">creep</span> in nanoporous gold</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ye, Xing-Long; Jin, Hai-Jun</p> <p>2013-11-11</p> <p>We have investigated the mechanical stability of nanoporous gold (npg) in an electrochemical environment, using in situ dilatometry and compression experiments. It is demonstrated that the gold nano-ligaments <span class="hlt">creep</span> under the action of surface stress which leads to spontaneous volume contractions in macroscopic npg samples. The <span class="hlt">creep</span> of npg, under or without external forces, can be controlled electrochemically. The <span class="hlt">creep</span> rate increases with increasing potential in double-layer potential region, and deceases to almost zero when the gold surface is adsorbed with oxygen. Surprisingly, we also noticed a correlation between <span class="hlt">creep</span> and surface diffusivity, which links the <span class="hlt">deformation</span> of nanocrystals to mobility of surface atoms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22066169','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22066169"><span id="translatedtitle"><span class="hlt">Deformation</span> <span class="hlt">characteristics</span> of {delta} phase in the delta-processed Inconel 718 alloy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zhang, H.Y.; Zhang, S.H.; Cheng, M.; Li, Z.X.</p> <p>2010-01-15</p> <p>The hot working <span class="hlt">characteristics</span> of {delta} phase in the delta-processed Inconel 718 alloy during isothermal compression <span class="hlt">deformation</span> at temperature of 950 deg. C and strain rate of 0.005 s{sup -1}, were studied by using optical microscope, scanning electron microscope and quantitative X-ray diffraction technique. The results showed that the dissolution of plate-like {delta} phase and the precipitation of spherical {delta} phase particles coexisted during the <span class="hlt">deformation</span>, and the content of {delta} phase decreased from 7.05 wt.% to 5.14 wt.%. As a result of <span class="hlt">deformation</span> breakage and dissolution breakage, the plate-like {delta} phase was spheroidized and transferred to spherical {delta} phase particles. In the center with largest strain, the plate-like {delta} phase disappeared and spherical {delta} phase appeared in the interior of grains and grain boundaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008EnGeo..54.1197T&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008EnGeo..54.1197T&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Characteristics</span> of <span class="hlt">deformation</span> of saturated soft clay under the load of Shanghai subway line No. 2</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tang, Yi-Qun; Yang, Ping; Zhao, Shu-Kai; Zhang, Xi; Wang, Jian-Xiu</p> <p>2008-05-01</p> <p>Shanghai subway Line No. 2 passes through the center of Shanghai from Songhong Road station in the west to Zhangjianggaoke station in the east. The total length of Shanghai subway Line No. 2 is 25 km. The tunnel mostly lies in the saturated soft clay and the environment issue can not be ignored. The response frequency and response stress of soil around the tunnel are monitored when the subway train passes through. The cyclic triaxial test of the saturated soft clay around the subway tunnel is conducted using the data monitored. The <span class="hlt">characteristics</span> of <span class="hlt">deformation</span> of the saturated soft clay of Shanghai under the subway load are analyzed. The results show that when the subway train Line No. 2 begins to run, a small and vertical rebound first occurs in the saturated soft clay at the side wall of the tunnel. Although a large <span class="hlt">deformation</span> does not occur in the saturated soft clay at the side wall of the tunnel when the subway train has run for a period of time, yet with the lapse of time, a perceptive and non-uniform <span class="hlt">deformation</span> will still occur. The vertical rebound is transitory and a plastic <span class="hlt">deformation</span> occurs immediately in the saturated soft clay at the bottom of the tunnel, the large <span class="hlt">deformation</span> at the bottom of the tunnel is 30 times that of the saturated soft clay at the side wall of the tunnel.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1323556','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1323556"><span id="translatedtitle">Room temperature <span class="hlt">creep</span> in metals and alloys</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Deibler, Lisa Anne</p> <p>2014-09-01</p> <p>Time dependent <span class="hlt">deformation</span> in the form of <span class="hlt">creep</span> and stress relaxation is not often considered a factor when designing structural alloy parts for use at room temperature. However, <span class="hlt">creep</span> and stress relaxation do occur at room temperature (0.09-0.21 T<sub>m</sub> for alloys in this report) in structural alloys. This report will summarize the available literature on room temperature <span class="hlt">creep</span>, present <span class="hlt">creep</span> data collected on various structural alloys, and finally compare the acquired data to equations used in the literature to model <span class="hlt">creep</span> behavior. Based on evidence from the literature and fitting of various equations, the mechanism which causes room temperature <span class="hlt">creep</span> is found to include dislocation generation as well as exhaustion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930083689','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930083689"><span id="translatedtitle">The <span class="hlt">Creep</span> of Single Crystals of Aluminum</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Johnson, R D; Shober, F R; Schwope, A D</p> <p>1953-01-01</p> <p>The <span class="hlt">creep</span> of single crystals of high-purity aluminum was investigated in the range of temperatures from room temperature to 400 F and at resolved-shear-stress levels of 200, 300, and 400 psi. The tests were designed in an attempt to produce data regarding the relation between the rate of strain and the mechanism of <span class="hlt">deformation</span>. The <span class="hlt">creep</span> data are analyzed in terms of shear strain rate and the results are discussed with regard to existing <span class="hlt">creep</span> theories. Stress-strain curves were determined for the crystals in tinsel and constant-load-rate tests in the same temperature range to supplement the study of plastic <span class="hlt">deformation</span> by <span class="hlt">creep</span> with information regarding the part played by crystal orientation, differences in strain markings, and other variables in plastic <span class="hlt">deformation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19830021122','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19830021122"><span id="translatedtitle"><span class="hlt">Creep</span> of plasma sprayed zirconia</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Firestone, R. F.; Logan, W. R.; Adams, J. W.</p> <p>1982-01-01</p> <p>Specimens of plasma-sprayed zirconia thermal barrier coatings with three different porosities and different initial particle sizes were <span class="hlt">deformed</span> in compression at initial loads of 1000, 2000, and 3500 psi and temperatures of 1100 C, 1250 C, and 1400 C. The coatings were stabilized with lime, magnesia, and two different concentrations of yttria. <span class="hlt">Creep</span> began as soon as the load was applied and continued at a constantly decreasing rate until the load was removed. Temperature and stabilization had a pronounced effect on <span class="hlt">creep</span> rate. The <span class="hlt">creep</span> rate for 20% Y2O3-80% ZrO2 was 1/3 to 1/2 that of 8% Y2O3-92% ZrO2. Both magnesia and calcia stabilized ZrO2 crept at a rate 5 to 10 times that of the 20% Y2O3 material. A near proportionality between <span class="hlt">creep</span> rate and applied stress was observed. The rate controlling process appeared to be thermally activated, with an activation energy of approximately 100 cal/gm mole K. <span class="hlt">Creep</span> <span class="hlt">deformation</span> was due to cracking and particle sliding.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JOM....63b..81C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JOM....63b..81C"><span id="translatedtitle"><span class="hlt">Deformation</span> <span class="hlt">characteristics</span> during Y-shaped tube hydroforming of 6061 aluminum alloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chu, Guannan; Li, Feng; Liu, Wenjian</p> <p>2011-02-01</p> <p>To manufacture lightweight tube components for aerospace oil circuit systems, an experiment was run to investigate the <span class="hlt">deformation</span> <span class="hlt">characteristics</span> on Y-shaped tube hydroforming of 6061 aluminum alloy. Both strain state and metallurgical structure indicate that there are four kinds of prevailing defects during Y-shaped tube hydroforming: bursting, lack of cylindricity, wrinkling, and thinning due to the poor plastic property of 6061 aluminum alloy. The danger of bursting prevails at the early stage of the operation as a result of excessively high internal pressure. In contrast, wrinkling prevails after the middle stage of the operation as a result of excessively axial feeding and cannot be eliminated during subsequent <span class="hlt">deformation</span>. Lack of cylindricity is mainly because of insufficient axial feeding and internal pressure but can be eliminated by increasing internal pressure. Elongation and compression <span class="hlt">deformations</span> are originated on protrusion and main pipe of Y-shape tube respectively all the way through the bulging process. Consequently, minimum and maximum thicknesses are at the top of protrusion and the bottom of Y-shape tube respectively, which induces a V-shape borderline of thickness distribution. According to the excessive plastic <span class="hlt">deformation</span>, microstructure evolution is originated. Crystal grain of protrusion is elongated and its grain size is about 150 μm. In contrast, crystal grain of the middle zone of main tube is refined greatly, which grain size is 50 μm, decreased by 75%. These are useful to improve the component.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AGUFM.T41D0247X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFM.T41D0247X"><span id="translatedtitle">Dislocation <span class="hlt">Creep</span> in Magnesium Calcite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, L.; Xiao, X.; Evans, B. J.</p> <p>2003-12-01</p> <p>To investigate the effect of dissolved Mg on plastic <span class="hlt">deformation</span> of calcite, we performed triaxial <span class="hlt">deformation</span> experiments on synthetic calcite with varying amount of Mg content. Mixtures of powders of calcite and dolomite were isostatically hot pressed (HIP) at 850° C and 300 MPa confining pressure for different intervals (2 to 20hrs) resulting in homogeneous aggregates of high-magnesium calcite; Mg content varied from 0.07 to 0.17 mol%. <span class="hlt">Creep</span> tests were performed at differential stresses from 20 to 160 MPa at 700 to 800° C. Grain sizes before and after <span class="hlt">deformation</span> were determined from the images obtained from scanning electron microscope (SEM) and optical microscope. Grain sizes are in the range of 5 to 20 microns depending on the HIP time, and decrease with increasing magnesium content. Both BSE images and chemical analysis suggest that all dolomite are dissolved and the Mg distribution is homogeneous through the sample, after 2 hrs HIP. At stresses below 40 MPa, the samples <span class="hlt">deformed</span> in diffusion region (Coble <span class="hlt">creep</span>), as described previously by Herwegh. The strength decreases with increasing magnesium content, owing to the difference of grain size. At stresses above 80 MPa, the stress exponent is greater than 3, indicating an increased contribution of dislocation <span class="hlt">creep</span>. The transition between diffusion to dislocation <span class="hlt">creep</span> occurs at higher stresses for the samples with higher magnesium content and smaller grain size. Preliminary data suggests a slight increase in strength with increasing magnesium content, but more tests are needed to verify this effect. In a few samples, some strain weakening may have been evident. The activation energy in the transition region (at 80 MPa) is ˜200 KJ/mol with no dependence on magnesium content, agreeing with previous measurements of diffusion <span class="hlt">creep</span> in natural and synthetic marbles.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5098692','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5098692"><span id="translatedtitle">The <span class="hlt">characteristics</span> of cavitation during superplastic <span class="hlt">deformation</span> of a warm-rolled Al-Li-Cu-Mg-Zr alloy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Liu, Q. ); Huang, X.; Yang, J.; Yao, M. )</p> <p>1991-01-01</p> <p>The process of superplastic forming has become important in numerous commercial applications. However, there may be some deleterious defects on the properties of superplastically-formed components due to the presence of minor levels of cavitation introduced during the forming process. Thus, it is important to obtain information on nucleation, growth and interlinkage of cavities in a wide range of superplastic materials. Two different thermomechanical processing routes may be employed to develop fine grain sizes conducive to superlasticity in Al-Li alloys. In one of them, a fine grain size microstructure is obtained by static recrystallization prior to superplastic <span class="hlt">deformation</span>, and in another, a fine grain size microstructure is obtained by <span class="hlt">deformation</span>-induced recrystallization during the initial stage of superplastic <span class="hlt">deformation</span>. The <span class="hlt">deformation</span>-induced recrystallization of a cold (or warm)-rolled Al-Li alloy is strongly dependent on the strain rate microstructural change during the initial stage of superplastic <span class="hlt">deformation</span> due to <span class="hlt">deformation</span>-induced recrystallization. There have been some studies dealing with cavitation in superplastic Al-Li alloys. However, there is no research work reported on the effect of <span class="hlt">deformation</span>-induced recrystallization on the <span class="hlt">characteristics</span> of cavitation during superplastic <span class="hlt">deformation</span> of a warm-rolled Al-Li alloy. This paper deals with the relationship between <span class="hlt">deformation</span>-induced recrystallization and cavitation <span class="hlt">characteristics</span> during superplastic <span class="hlt">deformation</span> of a warm-rolled Al-Li-Cu-Mg-Zr alloy. The results show that there are three kinds of cavities. The first includes the fine cavities formed at the beginning stage of <span class="hlt">deformation</span>, the second the large cavities formed around the intermetallic particles and the third the grain boundary cavities. All three kinds of cavities are closely related to <span class="hlt">deformation</span>-induced recrystallization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MS%26E...91a2030K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MS%26E...91a2030K"><span id="translatedtitle">Investigation of defect copper substructure disrupted in <span class="hlt">creep</span> condition under the action of magnetic field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Konovalov, S. V.; Yaropolova, N. G.; Zaguyliaev1, D. V.; Gromov, V. E.; Ivanov, Yu F.; Komissarova, I. A.</p> <p>2015-09-01</p> <p>The defect substructure of M00b copper samples loaded up to disruption in <span class="hlt">creep</span> condition both under and without the action of 0.35 T magnetic field is investigated in the paper. Material near the disrupted surface and at certain distances from it received the serious study. It has been ascertained that when copper disrupting without magnetic action on <span class="hlt">creep</span> process the main type of dislocation substructure is the cellular one irrespectively of the distance to disruption surface. As the result of magnetic field influence on <span class="hlt">creep</span> process the main type of dislocation substructure is replaced by the stripe-like one. The distinctive quantitative <span class="hlt">characteristics</span> of dislocation substructures are observed. Moreover, a gradient behavior of the number of stress raisers has been revealed when moving away from disruption surface both in <span class="hlt">deformation</span> conditions with and without a magnetic field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T53A2570Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T53A2570Z"><span id="translatedtitle">Combination of metamorphism and <span class="hlt">deformation</span> affect the nano-scale pore structures and macromolecule <span class="hlt">characteristics</span> of high-rank <span class="hlt">deformed</span> coals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, W.; Li, H.; Ju, Y.</p> <p>2013-12-01</p> <p>Coal constitutes a large proportion of total energy supply in the world. Coalbed Methane (CBM) composes the greenhouse gases, which has attracted more and more scientists' concern and attention. The adsorption/desorption <span class="hlt">characteristics</span> and mechanism of CBM on high-rank <span class="hlt">deformed</span> coals are in favor of enhancing gas recovery, reducing coal mining accidents and carbon emission. Although the influence factors of CBM adsorption/desorption on different coals have been intensively studied, the combined action of metamorphism and <span class="hlt">deformation</span> on high-rank coals have been rarely researched. Nevertheless. Metamorphism and <span class="hlt">deformation</span> are the most fundamental driving forces that cause the changes of inner structures and compositions in coal strata, and then alter the adsorption/desorption capacities of CBM on different coalbeds. South of Qinshui Basin in Shanxi province developed with abundant high-rank coals is the first demonstrate area of CBM development in China. Meanwhile Southwest of Fujian province represents high metamorphic-<span class="hlt">deformed</span> coals region due to the intense volcanic activities. Therefore samples were taken in both areas to elaborate the adsorption/desorption <span class="hlt">characteristics</span> and mechanism of CBM. Based on hand specimens description, coal macerals testing, proximate analysis, ultimate analysis and vitrinite reflectance testing, the physical properties and composition <span class="hlt">characteristics</span> of high-rank <span class="hlt">deformed</span> coals have been studied. Combined with liquid nitrogen adsorption experiments, Transmission Electron Microscopy (TEM) observation, Fourier Transform Infrared Spectrometry (FTIR) and Nuclear Magnetic Resonance (NMR) experiments, the results show that nano-pores increase and become homogenization with metamorphic-<span class="hlt">deformation</span> enhancement, stacking of the macromolecular basic structural units (BSU) enhances, aromatic compound increases while aliphatic chain compound and oxygen-containing function groups decrease. Comparing to coal adsorption/desorption isotherm</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10182881','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10182881"><span id="translatedtitle">Irradiation <span class="hlt">creep</span> in structural materials at ITER operating conditions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Grossbeck, M.L.</p> <p>1994-09-01</p> <p>Irradiation <span class="hlt">creep</span> is plastic <span class="hlt">deformation</span> of a material under the influence of irradiation and stress. Below the regime of thermal <span class="hlt">creep</span>, there remains a <span class="hlt">deformation</span> mechanism under irradiation that is weakly temperature dependent and clearly different from thermal <span class="hlt">creep</span>. This is irradiation <span class="hlt">creep</span>. Both stress and irradiation are required for irradiation <span class="hlt">creep</span>. Irradiation <span class="hlt">creep</span> studies for applications in the past focused mostly on liquid metal fast breeder reactors where temperatures are usually above 400{degrees}C. Fusion reactors, especially nearterm devices such as the ITER will have components operating at temperatures as low as 100{degrees}C exposed to high neutron fluxes. Theories of irradiation <span class="hlt">creep</span> based on steady-state point defect concentrations do not predict significant irradiation <span class="hlt">creep</span> <span class="hlt">deformation</span> at these temperatures; however, data from research reactors show that irradiation <span class="hlt">creep</span> strains at 60{degrees}C are as high or higher than at temperatures above 300{degrees}C for austenitic stainless steels. Irradiation <span class="hlt">creep</span> of nickel has also been observed at cryogenic temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001PhDT.......121C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001PhDT.......121C"><span id="translatedtitle"><span class="hlt">Creep</span> induced substructures in titanium aluminide</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cerreta, Ellen Kathleen</p> <p></p> <p>Many investigations have examined the <span class="hlt">creep</span> properties of titanium aluminides. Attempts to classify observed behaviors with existing models for high temperature <span class="hlt">deformation</span> have been met with limited success. Several researchers have shown that an understanding of substructural evolution in the early stages of the <span class="hlt">creep</span> curve may offer insight into the mechanisms, which control the rate of <span class="hlt">deformation</span>. <span class="hlt">Creep</span> <span class="hlt">deformation</span> has been shown to include twinning, recrystallization, grain boundary sliding, ordinary and super dislocation activity, and faulting depending on the microstructure of the alloy and testing conditions. However, the environments that these alloys are likely to be exposed to are not similar to the test conditions in the literature. Furthermore the emphasis of much of the research into this group of alloys has been on the effects of microstructure particularly, the volume fraction of lamellar phase and ternary elemental additions. With all of these studies little information is available on the <span class="hlt">deformation</span> behavior of the gamma phase. The alloys in these studies are mostly composed of the gamma phase and yet its <span class="hlt">creep</span> behavior is not well understood. For this reason single phase binary gamma titanium aluminides were investigated in this study. To understand the effects of aluminum, interstitial oxygen content, and stress on <span class="hlt">creep</span>, five alloys of varying Al concentrations and interstitial oxygen contents were <span class="hlt">deformed</span> at temperatures ranging from 700--800°C and at stresses of 150, 200, and 250MPa. Full <span class="hlt">creep</span> curves were developed under these conditions and phenomenological parameters for <span class="hlt">creep</span> were calculated from these data. Additional tests were interrupted during primary and secondary <span class="hlt">creep</span> at 760°C. Specimens from the interrupted tests as well as from the as-processed materials were examined optically and by TEM. <span class="hlt">Creep</span> data and the microscopy were analyzed in concert to determine rate-controlling mechanisms for <span class="hlt">creep</span>. Evolution of the substructure</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=232704','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=232704"><span id="translatedtitle">Study on <span class="hlt">creep</span> properties of Japonica cooked rice and its relationship with rice chemical compositions and sensory evaluation</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p><span class="hlt">Creep</span> properties of four varieties japonica cooked rice were tested using a Dynamic Mechanical Analyser (DMA Q800). The <span class="hlt">creep</span> curve was described by Burgers model. The <span class="hlt">creep</span> process of japonica cooked rice mainly consisted of retarded elastic <span class="hlt">deformation</span>, epsilonR and viscous flow <span class="hlt">deformation</span>, epsil...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JGRB..116.1203F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JGRB..116.1203F"><span id="translatedtitle">Dislocation <span class="hlt">creep</span> of fine-grained olivine</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Faul, U. H.; Fitz Gerald, J. D.; Farla, R. J. M.; Ahlefeldt, R.; Jackson, I.</p> <p>2011-01-01</p> <p><span class="hlt">Deformation</span> experiments conducted in a gas medium apparatus at temperatures from 1200 to 1350°C with a fine-grained, solution-gelation derived Fe-bearing olivine show a stress dependence of the strain rate at stresses above ˜150 MPa, which is much stronger than previously reported for polycrystalline samples. The data can be fit by a power law with ??σn with n ˜ 7-8, or equally well by a Peierls <span class="hlt">creep</span> law with exponential stress dependence. Due to the observed strong stress dependence the samples <span class="hlt">deform</span> at significantly higher strain rates at a given stress than single crystals or coarse-grained polycrystals with n ˜ 3.5. TEM observations indicate the presence of dislocations with at least two different Burgers vectors, with free dislocations predominantly of screw character. Subgrain walls are present but are only weakly developed and have small misorientation angles. Both the rheology and dislocation structures are consistent with <span class="hlt">creep</span> rate-limited by dislocation glide or cross slip for aggregates with grain sizes smaller than or approaching the recrystallized grain size. <span class="hlt">Deformation</span> mechanism maps extrapolated to lithospheric temperatures using the melt-free diffusion <span class="hlt">creep</span> rheology of Faul and Jackson (2007), the dislocation <span class="hlt">creep</span> rheology of Hirth and Kohlstedt (2003), and the results described here indicate that <span class="hlt">deformation</span> conditions of ultramylonitic shear zones fall near the triple point of Peierls, dislocation, and diffusion <span class="hlt">creep</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JMEP...23.4350L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JMEP...23.4350L"><span id="translatedtitle">A New <span class="hlt">Creep</span> Constitutive Model for 7075 Aluminum Alloy Under Elevated Temperatures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Y. C.; Jiang, Yu-Qiang; Zhou, Hua-Min; Liu, Guan</p> <p>2014-12-01</p> <p>Exposure of aluminum alloy to an elastic loading, during "<span class="hlt">creep</span>-aging forming" or other manufacturing processes at relatively high temperature, may lead to the lasting <span class="hlt">creep</span> <span class="hlt">deformation</span>. The <span class="hlt">creep</span> behaviors of 7075 aluminum alloy are investigated by uniaxial tensile <span class="hlt">creep</span> experiments over wide ranges of temperature and external stress. The results show that the <span class="hlt">creep</span> behaviors of the studied aluminum alloy strongly depend on the <span class="hlt">creep</span> temperature, external stress, and <span class="hlt">creep</span> time. With the increase of <span class="hlt">creep</span> temperature and external stress, the <span class="hlt">creep</span> strain increases quickly. In order to overcome the shortcomings of the Bailey-Norton law and θ projection method, a new constitutive model is proposed to describe the variations of <span class="hlt">creep</span> strain with time for the studied aluminum alloy. In the proposed model, the dependences of <span class="hlt">creep</span> strain on the <span class="hlt">creep</span> temperature, external stress, and <span class="hlt">creep</span> time are well taken into account. A good agreement between the predicted and measured <span class="hlt">creep</span> strains shows that the established <span class="hlt">creep</span> constitutive model can give an accurate description of the <span class="hlt">creep</span> behaviors of 7075 aluminum alloy. Meanwhile, the obtained stress exponent indicates that the <span class="hlt">creep</span> process is controlled by the dislocation glide, which is verified by the microstructural observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/11008740','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11008740"><span id="translatedtitle">Early <span class="hlt">characteristic</span> findings in bowleg <span class="hlt">deformities</span>: evaluation using magnetic resonance imaging.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mukai, S; Suzuki, S; Seto, Y; Kashiwagi, N; Hwang, E S</p> <p>2000-01-01</p> <p>We used magnetic resonance imaging (MRI) to evaluate bowleg <span class="hlt">deformities</span> in infancy. Twenty-five tibiae of 13 infants were examined and divided into two groups based on MRI findings: group A had high intensity area in the medial epiphyseal cartilage on T2-weighted images. Group B had depression of medial physis and abnormal signal in the perichondrial region in addition to the epiphyseal lesion. At the final follow-up, all cases in group A demonstrated normal lower leg alignments, whereas five cases in group B showed <span class="hlt">characteristic</span> roentogenographic findings of Blount's disease. The improvement rate of metaphyseal-diaphyseal angle was correlated with this classification. These findings suggested that abnormal findings in physis and perichondrial region might be preliminary findings in early stage of Blount's disease. The high intensity areas in the medial epiphyseal cartilage were commonly found among the cases with bowing <span class="hlt">deformities</span>, which suggested that there might be a common pathomechanism between physiologic bowing and infantile Blount's disease. PMID:11008740</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015SolED...7.3179L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015SolED...7.3179L&link_type=ABSTRACT"><span id="translatedtitle">Analysis of crustal <span class="hlt">deformation</span> and strain <span class="hlt">characteristics</span> in the Tianshan Mountains with least-squares collocation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, S. P.; Chen, G.; Li, J. W.</p> <p>2015-11-01</p> <p>By fitting the observed velocity field of the Tianshan Mountains from 1992 to 2006 with least-squares collocation, we established a velocity field model in this region. The velocity field model reflects the crustal <span class="hlt">deformation</span> <span class="hlt">characteristics</span> of the Tianshan reasonably well. From the Tarim Basin to the Junggar Basin and Kazakh platform, the crustal <span class="hlt">deformation</span> decreases gradually. Divided at 82° E, the convergence rates in the west are obviously higher than those in the east. We also calculated the parameter values for crustal strain in the Tianshan Mountains. The results for maximum shear strain exhibited a concentration of significantly high values at Wuqia and its western regions, and the values reached a maxima of 4.4×10-8 a-1. According to isogram distributions for the surface expansion rate, we found evidence that the Tianshan Mountains have been suffering from strong lateral extrusion by the basin on both sides. Combining this analysis with existing results for focal mechanism solutions from 1976 to 2014, we conclude that it should be easy for a concentration of earthquake events to occur in regions where maximum shear strains accumulate or mutate. For the Tianshan Mountains, the possibility of strong earthquakes in Wuqia-Jiashi and Lake Issyk-Kul will persist over the long term.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130014001','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130014001"><span id="translatedtitle">Low Temperature <span class="hlt">Creep</span> of Hot-Extruded Near-Stoichiometric NiTi Shape Memory Alloy. Part I; Isothermal <span class="hlt">Creep</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Raj, S. V.; Noebe, R. D.</p> <p>2013-01-01</p> <p>This two-part paper is the first published report on the long term, low temperature <span class="hlt">creep</span> of hot-extruded near-stoichiometric NiTi. Constant load tensile <span class="hlt">creep</span> tests were conducted on hot-extruded near-stoichiometric NiTi at 300, 373 and 473 K under initial applied stresses varying between 200 and 350 MPa as long as 15 months. These temperatures corresponded to the martensitic, two-phase and austenitic phase regions, respectively. Normal primary <span class="hlt">creep</span> lasting several months was observed under all conditions indicating dislocation activity. Although steady-state <span class="hlt">creep</span> was not observed under these conditions, the estimated <span class="hlt">creep</span> rates varied between 10(exp -10) and 10(exp -9)/s. The <span class="hlt">creep</span> behavior of the two phases showed significant differences. The martensitic phase exhibited a large strain on loading followed by a primary <span class="hlt">creep</span> region accumulating a small amount of strain over a period of several months. The loading strain was attributed to the detwinning of the martensitic phase whereas the subsequent strain accumulation was attributed to dislocation glide-controlled <span class="hlt">creep</span>. An "incubation period" was observed before the occurrence of detwinning. In contrast, the austenitic phase exhibited a relatively smaller loading strain followed by a primary <span class="hlt">creep</span> region, where the <span class="hlt">creep</span> strain continued to increase over several months. It is concluded that the <span class="hlt">creep</span> of the austenitic phase occurs by a dislocation glide-controlled <span class="hlt">creep</span> mechanism as well as by the nucleation and growth of <span class="hlt">deformation</span> twins.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMMR33C..02K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMMR33C..02K"><span id="translatedtitle">In Situ <span class="hlt">Creep</span> Strength Measurements on Ringwoodite at 18 GPa and 1700K Using a <span class="hlt">Deformation</span>-DIA Apparatus Combined with Synchrotron Radiation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kawazoe, T.; Nishihara, Y.; Ohuchi, T.; Maruyama, G.; Higo, Y.; Funakoshi, K.; Irifune, T.</p> <p>2013-12-01</p> <p>In order to study rheology of deep Earth materials at pressure-temperature conditions of the lower mantle transition zone, technical improvements in <span class="hlt">deformation</span> experiments with a <span class="hlt">deformation</span>-DIA (D-DIA) apparatus have been made. We optimized dimensions of anvil truncation, a pressure medium and gasket to achieve the <span class="hlt">deformation</span> experiments at 18 GPa at relatively low press load (0.5 MN) to minimize damage of X-ray transparent second-stage anvils. Stress and strain of a sample were determined quantitatively by means of in situ X-ray radial diffraction and radiography, respectively, in conjunction with synchrotron radiation at BL04B1 beamline, SPring-8. We adopted low X-ray absorption materials (e.g. cubic BN anvils, graphite window in a LaCrO3 heater) along an X-ray path to enable the in situ stress-strain measurements. Based on the developed technique, the <span class="hlt">deformation</span> experiments on ringwoodite were carried out in uniaxial geometry at pressures of 17-18 GPa and temperatures of 1500-1700 K with strain rates of 3.38-5.56 × 10-5 s-1 and strains up to 26.0 %. In the present study, the pressure condition of the in situ stress-strain measurements in the D-DIA apparatus was successfully expanded from 14.5 GPa to 18 GPa at temperatures of 1500-1700 K. The present technical improvements in the in situ stress-strain measurements with the D-DIA apparatus should greatly contribute to studies on rheology of the deep Earth materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4071770','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4071770"><span id="translatedtitle"><span class="hlt">Creep</span> of trabecular bone from the human proximal tibia</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Novitskaya, Ekaterina; Zin, Carolyn; Chang, Neil; Cory, Esther; Chen, Peter; D'Lima, Darryl; Sah, Robert L.; McKittrick, Joanna</p> <p>2014-01-01</p> <p><span class="hlt">Creep</span> is the <span class="hlt">deformation</span> that occurs under a prolonged, sustained load and can lead to permanent damage in bone. <span class="hlt">Creep</span> in bone is a complex phenomenon and varies with type of loading and local mechanical properties. Human trabecular bone samples from proximal tibia were harvested from a 71-year old female cadaver with osteoporosis. The samples were initially subjected to one cycle load up to 1% strain to determine the <span class="hlt">creep</span> load. Samples were then loaded in compression under a constant stress for two hours and immediately unloaded. All tests were conducted with the specimens soaked in phosphate buffered saline with proteinase inhibitors at 37°C. Steady state <span class="hlt">creep</span> rate and final <span class="hlt">creep</span> strain were estimated from mechanical testing and compared with published data. The steady state <span class="hlt">creep</span> rate correlated well with values obtained from bovine tibial and human vertebral trabecular bone, and was higher for lower density samples. Tissue architecture was analyzed by micro-computed tomography (μCT) both before and after <span class="hlt">creep</span> testing to assess <span class="hlt">creep</span> <span class="hlt">deformation</span> and damage accumulated. Quantitative morphometric analysis indicated that <span class="hlt">creep</span> induced changes in trabecular separation and the structural model index. A main mode of <span class="hlt">deformation</span> was bending of trabeculae. PMID:24857486</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/335410','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/335410"><span id="translatedtitle">Contribution to irradiation <span class="hlt">creep</span> arising from gas-driven bubbles</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Woo, C.H.; Garner, F.A.</p> <p>1998-03-01</p> <p>In a previous paper the relationship was defined between void swelling and irradiation <span class="hlt">creep</span> arising from the interaction of the SIPA and SIG <span class="hlt">creep</span>-driven <span class="hlt">deformation</span> and swelling-driven <span class="hlt">deformation</span> was highly interactive in nature, and that the two contributions could not be independently calculated and then considered as directly additive. This model could be used to explain the recent experimental observation that the <span class="hlt">creep</span>-swelling coupling coefficient was not a constant as previously assumed, but declined continuously as the swelling rate increased. Such a model thereby explained the <span class="hlt">creep</span>-disappearance and <span class="hlt">creep</span>-damping anomalies observed in conditions where significant void swelling occurred before substantial <span class="hlt">creep</span> <span class="hlt">deformation</span> developed. At lower irradiation temperatures and high helium/hydrogen generation rates, such as found in light water cooled reactors and some fusion concepts, gas-filled cavities that have not yet exceeded the critical radius for bubble-void conversion should also exert an influence on irradiation <span class="hlt">creep</span>. In this paper the original concept is adapted to include such conditions, and its predictions then compared with available data. It is shown that a measurable increase in the <span class="hlt">creep</span> rate is expected compared to the rate found in low gas-generating environments. The <span class="hlt">creep</span> rate is directly related to the gas generation rate and thereby to the neutron flux and spectrum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/755861','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/755861"><span id="translatedtitle"><span class="hlt">Creep</span> in electronic ceramics</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Routbort, J. L.; Goretta, K. C.; Arellano-Lopez, A. R.</p> <p>2000-04-27</p> <p>High-temperature <span class="hlt">creep</span> measurements combined with microstructural investigations can be used to elucidate <span class="hlt">deformation</span> mechanisms that can be related to the diffusion kinetics and defect chemistry of the minority species. This paper will review the theoretical basis for this correlation and illustrate it with examples from some important electronic ceramics having a perovskite structure. Recent results on BaTiO{sub 3}, (La{sub 1{minus}x}Sr){sub 1{minus}y}MnO{sub 3+{delta}}, YBa{sub 2}Cu{sub 3}O{sub x}, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x}, (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} and Sr(Fe,Co){sub 1.5}O{sub x} will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/7029371','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/7029371"><span id="translatedtitle">Effect of unloading time on interrupted <span class="hlt">creep</span> in copper</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chandler, H.D. . School of Mechanical Engineering)</p> <p>1994-06-01</p> <p>The effect of unloading time on the interrupted <span class="hlt">creep</span> behavior of polycrystalline copper specimens was investigated over the temperature range 298--773 K. Up to 553 K, cyclic <span class="hlt">creep</span> acceleration could be explained in terms of <span class="hlt">deformation</span> and hardening using a dislocation glide model with recovery during unloading being due to dislocation climb. At higher temperatures, recrystallization effects probably influence behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910000604&hterms=reduce+stress&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dreduce%2Bstress','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910000604&hterms=reduce+stress&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dreduce%2Bstress"><span id="translatedtitle">Temperature, Thermal Stress, And <span class="hlt">Creep</span> In A Structure</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jenkins, Jerald M.</p> <p>1991-01-01</p> <p>Report presents comparison of predicted and measured temperatures, thermal stresses, and residual <span class="hlt">creep</span> stresses in heated and loaded titanium structure. Study part of continuing effort to develop design capability to predict and reduce deleterious effects of <span class="hlt">creep</span>, which include excessive <span class="hlt">deformations</span>, residual stresses, and failure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4419272','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4419272"><span id="translatedtitle">Quantitative analysis of tissue <span class="hlt">deformation</span> dynamics reveals three <span class="hlt">characteristic</span> growth modes and globally aligned anisotropic tissue <span class="hlt">deformation</span> during chick limb development</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Morishita, Yoshihiro; Kuroiwa, Atsushi; Suzuki, Takayuki</p> <p>2015-01-01</p> <p>Tissue-level characterization of <span class="hlt">deformation</span> dynamics is crucial for understanding organ morphogenetic mechanisms, especially the interhierarchical links among molecular activities, cellular behaviors and tissue/organ morphogenetic processes. Limb development is a well-studied topic in vertebrate organogenesis. Nevertheless, there is still little understanding of tissue-level <span class="hlt">deformation</span> relative to molecular and cellular dynamics. This is mainly because live recording of detailed cell behaviors in whole tissues is technically difficult. To overcome this limitation, by applying a recently developed Bayesian approach, we here constructed tissue <span class="hlt">deformation</span> maps for chick limb development with high precision, based on snapshot lineage tracing using dye injection. The precision of the constructed maps was validated with a clear statistical criterion. From the geometrical analysis of the map, we identified three <span class="hlt">characteristic</span> tissue growth modes in the limb and showed that they are consistent with local growth factor activity and cell cycle length. In particular, we report that SHH signaling activity changes dynamically with developmental stage and strongly correlates with the dynamic shift in the tissue growth mode. We also found anisotropic tissue <span class="hlt">deformation</span> along the proximal-distal axis. Morphogenetic simulation and experimental studies suggested that this directional tissue elongation, and not local growth, has the greatest impact on limb shaping. This result was supported by the novel finding that anisotropic tissue elongation along the proximal-distal axis occurs independently of cell proliferation. Our study marks a pivotal point for multi-scale system understanding in vertebrate development. PMID:25858459</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19730048309&hterms=stress+degradation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dstress%2Bdegradation','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19730048309&hterms=stress+degradation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dstress%2Bdegradation"><span id="translatedtitle">Diffusional <span class="hlt">creep</span> and <span class="hlt">creep</span>-degradation in dispersion-strengthened Ni-Cr base alloys.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Whittenberger, J. D.</p> <p>1973-01-01</p> <p>Dispersoid-free regions were observed in the dispersion-strengthened alloy TD-NiCr (Ni-20 Cr-2 ThO2) after slow strain rate testing (stress rupture, <span class="hlt">creep</span>, and fatigue) in air from 1145 to 1590 K. Formation of the dispersoid-free regions appears to be the result of diffusional <span class="hlt">creep</span>. The net effect of <span class="hlt">creep</span> in TD-NiCr is the degradation of the alloy to a duplex microstructure. <span class="hlt">Creep</span> degradation of TD-NiCr is further enhanced by the formation of voids and intergranular oxidation in the dispersoid-free bands. Void formation was observed after as little as 0.13% <span class="hlt">creep</span> <span class="hlt">deformation</span> at 1255 K. The dispersoid-free regions apparently provide sites for void formation and oxide growth since the strength and oxidation resistance of Ni-20 Cr-2 ThO2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJWC..9401061B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9401061B"><span id="translatedtitle">Experimental and calculated approach to the study of <span class="hlt">deformation</span> and strength <span class="hlt">characteristics</span> of elastoviscoplastic materials by direct impact method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bazhenov, V. G.; Baranova, M. S.; Nagornykh, E. V.; Osetrov, D. L.</p> <p>2015-09-01</p> <p>It is proposed to develop experimental and calculated approach to the study of the strength <span class="hlt">characteristics</span> of elastoviscoplastic materials in a non-uniform strain-stress state. Integral <span class="hlt">characteristics</span> (forces, displacements and displacement speed) of the <span class="hlt">deformation</span> process of hat-shaped specimens in tension are determined by a direct impact method, and their strain - stress states are determined by numerical solution of the axisymmetric problem. The results of experimental and theoretical study of the <span class="hlt">deformation</span> and failure of hat-shaped specimens in the presence of stress concentrators are obtained.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMMR23C4365Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMMR23C4365Z"><span id="translatedtitle">Diffusion <span class="hlt">creep</span> of enstatite at high pressures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, G.; Mei, S.; Kohlstedt, D. L.</p> <p>2014-12-01</p> <p><span class="hlt">Deformation</span> behavior of fine-grained enstatite (g.s. ~ 8 μm) was investigated with triaxial compressive <span class="hlt">creep</span> experiments at high pressures (4.2 - 6.9 GPa) and high temperatures (1373 - 1573 K) using a <span class="hlt">deformation</span>-DIA apparatus. Experiments were carried out under anhydrous conditions. In each experiment, a sample column composed of a sample and alumina pistons was assembled with a boron nitride sleeve and graphite resistance heater into a 6.2-mm edge length cubic pressure medium. Experiments were carried out at the National Synchrotron Light Source at Brookhaven National Laboratory. In a run, differential stress and sample displacement were monitored in-situ using synchrotron x-ray diffraction and radiography, respectively. Based on results from this study, the <span class="hlt">deformation</span> behavior of enstatite under anhydrous conditions has been quantitatively presented in the form of a flow law that describes the dependence of <span class="hlt">deformation</span> rate on stress, temperature, and pressure. Specifically, data fitting yields the dependence of <span class="hlt">creep</span> rate on stress with an exponent of n ≈ 1; indicating samples were <span class="hlt">deformed</span> in the regime of diffusion <span class="hlt">creep</span>. Experimental results also yield the dependences of <span class="hlt">creep</span> rate on temperature and pressure with an activation energy of ~250 kJ/mol and activation volume of ~3.5×10-6 m3/mol, respectively. The flow laws for enstatite, one important constituent component for the upper mantle, quantified from this study provides a necessary constraint for modeling the dynamic activities occurring within Earth's interior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19890043229&hterms=CLEM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DCLEM','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19890043229&hterms=CLEM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DCLEM"><span id="translatedtitle"><span class="hlt">Creep</span> and <span class="hlt">creep</span>-recovery of a thermoplastic resin and composite</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hiel, Clem</p> <p>1988-01-01</p> <p>The database on advanced thermoplastic composites, which is currently available to industry, contains little data on the <span class="hlt">creep</span> and viscoelastic behavior. This behavior is nevertheless considered important, particularly for extended-service reliability in structural applications. The <span class="hlt">creep</span> <span class="hlt">deformation</span> of a specific thermoplastic resin and composite is reviewed. The problem to relate the data obtained on the resin to the data obtained on the composite is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JMEP..tmp..315K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMEP..tmp..315K"><span id="translatedtitle">Hot <span class="hlt">Deformation</span> <span class="hlt">Characteristics</span> of 13Cr-4Ni Stainless Steel Using Constitutive Equation and Processing Map</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kishor, Brij; Chaudhari, G. P.; Nath, S. K.</p> <p>2016-06-01</p> <p>Hot compression tests were performed to study the hot <span class="hlt">deformation</span> <span class="hlt">characteristics</span> of 13Cr-4Ni stainless steel. The tests were performed in the strain rate range of 0.001-10 s-1 and temperature range of 900-1100 °C using Gleeble® 3800 simulator. A constitutive equation of Arrhenius type was established based on the experimental data to calculate the different material constants, and average value of apparent activation energy was found to be 444 kJ/mol. Zener-Hollomon parameter, Z, was estimated in order to characterize the flow stress behavior. Power dissipation and instability maps developed on the basis of dynamic materials model for true strain of 0.5 show optimum hot working conditions corresponding to peak efficiency range of about 28-32%. These lie in the temperature range of 950-1025 °C and corresponding strain rate range of 0.001-0.01 s-1 and in the temperature range of 1050-1100 °C and corresponding strain rate range of 0.01-0.1 s-1. The flow <span class="hlt">characteristics</span> in these conditions show dynamic recrystallization behavior. The microstructures are correlated to the different stability domains indicated in the processing map.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JMEP...25.2651K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMEP...25.2651K"><span id="translatedtitle">Hot <span class="hlt">Deformation</span> <span class="hlt">Characteristics</span> of 13Cr-4Ni Stainless Steel Using Constitutive Equation and Processing Map</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kishor, Brij; Chaudhari, G. P.; Nath, S. K.</p> <p>2016-07-01</p> <p>Hot compression tests were performed to study the hot <span class="hlt">deformation</span> <span class="hlt">characteristics</span> of 13Cr-4Ni stainless steel. The tests were performed in the strain rate range of 0.001-10 s-1 and temperature range of 900-1100 °C using Gleeble® 3800 simulator. A constitutive equation of Arrhenius type was established based on the experimental data to calculate the different material constants, and average value of apparent activation energy was found to be 444 kJ/mol. Zener-Hollomon parameter, Z, was estimated in order to characterize the flow stress behavior. Power dissipation and instability maps developed on the basis of dynamic materials model for true strain of 0.5 show optimum hot working conditions corresponding to peak efficiency range of about 28-32%. These lie in the temperature range of 950-1025 °C and corresponding strain rate range of 0.001-0.01 s-1 and in the temperature range of 1050-1100 °C and corresponding strain rate range of 0.01-0.1 s-1. The flow <span class="hlt">characteristics</span> in these conditions show dynamic recrystallization behavior. The microstructures are correlated to the different stability domains indicated in the processing map.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.G43A0845A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.G43A0845A"><span id="translatedtitle">Investigating the <span class="hlt">creeping</span> section of the San Andreas Fault using ALOS PALSAR interferometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Agram, P. S.; Wortham, C.; Zebker, H. A.</p> <p>2010-12-01</p> <p>In recent years, time-series InSAR techniques have been used to study the temporal <span class="hlt">characteristics</span> of various geophysical phenomena that produce surface <span class="hlt">deformation</span> including earthquakes and magma migration in volcanoes. Conventional InSAR and time-series InSAR techniques have also been successfully used to study aseismic <span class="hlt">creep</span> across faults in urban areas like the Northern Hayward Fault in California [1-3]. However, application of these methods to studying the time-dependent <span class="hlt">creep</span> across the Central San Andreas Fault using C-band ERS and Envisat radar satellites has resulted in limited success. While these techniques estimate the average long-term far-field <span class="hlt">deformation</span> rates reliably, <span class="hlt">creep</span> measurement close to the fault (< 3-4 Km) is virtually impossible due to heavy decorrelation at C-band (6cm wavelength). Shanker and Zebker (2009) [4] used the Persistent Scatterer (PS) time-series InSAR technique to estimate a time-dependent non-uniform <span class="hlt">creep</span> signal across a section of the <span class="hlt">creeping</span> segment of the San Andreas Fault. However, the identified PS network was spatially very sparse (1 per sq. km) to study temporal <span class="hlt">characteristics</span> of <span class="hlt">deformation</span> of areas close to the fault. In this work, we use L-band (24cm wavelength) SAR data from the PALSAR instrument on-board the ALOS satellite, launched by Japanese Aerospace Exploration Agency (JAXA) in 2006, to study the temporal <span class="hlt">characteristics</span> of <span class="hlt">creep</span> across the Central San Andreas Fault. The longer wavelength at L-band improves observed correlation over the entire scene which significantly increased the ground area coverage of estimated <span class="hlt">deformation</span> in each interferogram but at the cost of decreased sensitivity of interferometric phase to surface <span class="hlt">deformation</span>. However, noise levels in our <span class="hlt">deformation</span> estimates can be decreased by combining information from multiple SAR acquisitions using time-series InSAR techniques. We analyze 13 SAR acquisitions spanning the time-period from March 2007 to Dec 2009 using the Short Baseline</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015MS%26E...93a2026G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015MS%26E...93a2026G&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Deformation</span> <span class="hlt">characteristics</span> of the near-surface layers of zirconia ceramics implanted with aluminum ions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghyngazov, S. A.; Vasiliev, I. P.; Frangulyan, T. S.; Chernyavski, A. V.</p> <p>2015-10-01</p> <p>The effect of ion treatment on the phase composition and mechanical properties of the near-surface layers of zirconium ceramic composition 97 ZrO2-3Y2O3 (mol%) was studied. Irradiation of the samples was carried out by accelerated ions of aluminum with using vacuum-arc source Mevva 5-Ru. Ion beam had the following parameters: the energy of the accelerated ions E = 78 keV, the pulse current density Ji = 4mA / cm2, current pulse duration equal τ = 250 mcs, pulse repetition frequency f = 5 Hz. Exposure doses (fluence) were 1016 и 1017 ion/cm2. The depth distribution implanted ions was studied by SIMS method. It is shown that the maximum projected range of the implanted ions is equal to 250 nm. Near-surface layers were investigated by X-ray diffraction (XRD) at fixed glancing incidence angle. It is shown that implantation of aluminum ions into the ceramics does not lead to a change in the phase composition of the near-surface layer. The influence of implanted ions on mechanical properties of ceramic near-surface layers was studied by the method of dynamic nanoindentation using small loads on the indenter P=300 mN. It is shown that in ion- implanted ceramic layer the processes of material recovery in the <span class="hlt">deformed</span> region in the unloading mode proceeds with higher efficiency as compared with the initial material state. The <span class="hlt">deformation</span> <span class="hlt">characteristics</span> of samples before and after ion treatment have been determined from interpretation of the resulting P-h curves within the loading and unloading sections by the technique proposed by Oliver and Pharr. It was found that implantation of aluminum ions in the near-surface layer of zirconia ceramics increases nanohardness and reduces the Young's modulus.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22163150','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22163150"><span id="translatedtitle">Quantitative investigation of the tensile plastic <span class="hlt">deformation</span> <span class="hlt">characteristic</span> and microstructure for friction stir welded 2024 aluminum alloy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hu, Z.L.; Wang, X.S.; Yuan, S.J.</p> <p>2012-11-15</p> <p>The effect of the microstructure heterogeneity on the tensile plastic <span class="hlt">deformation</span> <span class="hlt">characteristic</span> of friction stir welded (FSW) 2024 aluminum alloy was investigated for the potential applications on light weight design of vehicles. The microstructure <span class="hlt">characteristics</span> of the FSW joints, such as the grain structure, dislocation density and the distribution of precipitation, were studied by electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). The tensile <span class="hlt">deformation</span> <span class="hlt">characteristic</span> of the FSW joints was examined using the automatic strain measuring system (ASAME) by mapping the global and local strain distribution, and then was analyzed by mechanics calculation. It is found that the tensile <span class="hlt">deformation</span> of the FSW joints is highly heterogeneous leading to a significant decrease in global ductility. The FSW joints mainly contain two typical <span class="hlt">deformation</span> zones, which show great effect on the regional inhomogeneous <span class="hlt">deformation</span>. One is the nugget zone (NZ) with a region of 8 mm in width, and the other is part of the BM with a region of 10 mm in width. The BM of the joints is the weakest region where the strain localizes early and this localization extends until fracture with a strain over 30%, while the strain in the NZ is only 4%. Differences in regional strain of FSW joints, which are essentially controlled by grain structure, the distribution of precipitation and dislocation density, result in decrease on the overall mechanical properties. - Highlights: Black-Right-Pointing-Pointer Microstructure heterogeneity of welds on tensile <span class="hlt">deformation</span> behavior is studied. Black-Right-Pointing-Pointer The welds contain two typical <span class="hlt">deformation</span> zones, affecting the global ductility. Black-Right-Pointing-Pointer Regional strain of welds is controlled by grain structure and dislocation density. Black-Right-Pointing-Pointer Theoretical calculation is in good agreement with experimental result.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MMTA...46.4601T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MMTA...46.4601T"><span id="translatedtitle"><span class="hlt">Creep</span> Mechanisms of a Ni-Co-Based-Wrought Superalloy with Low Stacking Fault Energy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tian, Chenggang; Xu, Ling; Cui, Chuanyong; Sun, Xiaofeng</p> <p>2015-10-01</p> <p>In order to study the influences of stress and temperature on the <span class="hlt">creep</span> <span class="hlt">deformation</span> mechanisms of a newly developed Ni-Co-based superalloy with low stacking fault energy, <span class="hlt">creep</span> experiments were carried out under a stress range of 345 to 840 MPa and a temperature range of 923 K to 1088 K (650 °C to 815 °C). The mechanisms operated under the various <span class="hlt">creep</span> conditions were identified and the reasons for their transformation were well discussed. A <span class="hlt">deformation</span> mechanism map under different <span class="hlt">creep</span> conditions was summarized, which provides a qualitative representation of the operative <span class="hlt">creep</span> mechanisms as a function of stress and temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhRvE..92b2405L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhRvE..92b2405L&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Creep</span> rupture of fiber bundles: A molecular dynamics investigation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Linga, G.; Ballone, P.; Hansen, Alex</p> <p>2015-08-01</p> <p>The <span class="hlt">creep</span> <span class="hlt">deformation</span> and eventual breaking of polymeric samples under a constant tensile load F is investigated by molecular dynamics based on a particle representation of the fiber bundle model. The results of the virtual testing of fibrous samples consisting of 40 000 particles arranged on Nc=400 chains reproduce <span class="hlt">characteristic</span> stages seen in the experimental investigations of <span class="hlt">creep</span> in polymeric materials. A logarithmic plot of the bundle lifetime τ versus load F displays a marked curvature, ruling out a simple power-law dependence of τ on F . A power law τ ˜F-4 , however, is recovered at high load. We discuss the role of reversible bond breaking and formation on the eventual fate of the sample and simulate a different type of <span class="hlt">creep</span> testing, imposing a constant stress rate on the sample up to its breaking point. Our simulations, relying on a coarse-grained representation of the polymer structure, introduce new features into the standard fiber bundle model, such as real-time dynamics, inertia, and entropy, and open the way to more detailed models, aiming at material science aspects of polymeric fibers, investigated within a sound statistical mechanics framework.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AIPC..700.1248K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AIPC..700.1248K"><span id="translatedtitle">On the Detection of <span class="hlt">Creep</span> Damage in a Directionally Solidified Nickel Base Superalloy Using Nonlinear Ultrasound</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kang, Jidong; Qu, Jianmin; Saxena, Ashok; Jacobs, Larry</p> <p>2004-02-01</p> <p>A limited experimental study was conducted to investigate the feasibility of using nonlinear ultrasonic technique for assessing the remaining <span class="hlt">creep</span> life of a directionally solidified (DS) nickel base superalloy. Specimens of this alloy were subjected to <span class="hlt">creep</span> testing at different stress levels. <span class="hlt">Creep</span> tests were periodically interrupted at different <span class="hlt">creep</span> life fractions to conduct transmission ultrasonic tests to explore if a correlation exists between the higher order harmonics and the accumulated <span class="hlt">creep</span> damage in the samples. A strong and unique correlation was found between the third order harmonic of the transmitted wave and the exhausted <span class="hlt">creep</span> life fraction. Preliminary data also show an equally strong correlation between plastic <span class="hlt">deformation</span> accumulated during monotonic loading and the second harmonic of the transmitted ultrasonic wave while no correlation was found between plastic strain and the third order harmonic. Thus, the nonlinear ultrasonic technique can potentially distinguish between damage due to plastic <span class="hlt">deformation</span> and <span class="hlt">creep</span> <span class="hlt">deformation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998PhDT.......112F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998PhDT.......112F"><span id="translatedtitle"><span class="hlt">Creep</span> behavior of thin laminates of iron-cobalt alloys for use in switched reluctance motors and generators</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fingers, Richard Todd</p> <p></p> <p>The United States Air Force is in the process of developing magnetic bearings as well as an aircraft Integrated Power Unit and an Internal Starter/Generator for main propulsion engines. These developments are the driving force behind a new emphasis on high temperature, high strength magnetic materials for power applications. Analytical work, utilizing elasticity theory, in conjunction with design requirements, indicates a need for magnetic materials to have strengths in excess of 80 ksi up to about 1000sp°F. It is this combination of desired material <span class="hlt">characteristics</span> that is the motivation for this effort to measure, model, and predict the <span class="hlt">creep</span> behavior of such advanced magnetic materials. Hipercosp°ler Alloy 50HS, manufactured by Carpenter Technology Corporation, is one of the leading candidates for application and is studied in this effort by subjecting mechanical test specimens to a battery of tensile and <span class="hlt">creep</span> tests. The tensile tests provide stress versus strain behaviors that clearly indicate: a yield point, a heterogeneous <span class="hlt">deformation</span> described as Luders elongation, the Portevin-LeChatelier effect at elevated temperatures, and, most often, a section of homogeneous <span class="hlt">deformation</span> that concluded with necking and fracture. <span class="hlt">Creep</span> testing indicated two distinct types of behavior. The first was a traditional response with primary, secondary and tertiary stages, while the second type could be characterized by an abrupt increase in strain rate that acted as a transition from one steady state behavior to another. This second linear region was then followed by the tertiary stage. The relationship between the tensile response and the <span class="hlt">creep</span> responses is discussed. Analyses of the mechanical behavior includes double linear regression of empirically modeled data, scanning electron microscopy for microstructural investigations, isochronous stress-strain relations, and constant strain rate testing to relate the tensile and <span class="hlt">creep</span> test parameters. Also, elastic and <span class="hlt">creep</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998JNuM..254...74S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998JNuM..254...74S"><span id="translatedtitle">Deuteron irradiation <span class="hlt">creep</span> of chemically vapor deposited silicon carbide fibers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scholz, R.</p> <p>1998-03-01</p> <p>Irradiation <span class="hlt">creep</span> tests were conducted on Textron SCS-6 silicon carbide (SiC) fibers during irradiation with 14 MeV deuterons at 450 and 600°C. The fibers are produced by a CVD procedure; their microstructure may therefore be representative for the matrix of a SiC composite. There is a significant radiation induced increase in <span class="hlt">creep</span> <span class="hlt">deformation</span>. Both quantities, irradiation <span class="hlt">creep</span> strain and <span class="hlt">creep</span> rate, are higher at 450°C than at 600°C for doses <0.07 dpa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.6732R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.6732R"><span id="translatedtitle">Investigating the <span class="hlt">Creeping</span> Segment of the San Andreas Fault using InSAR time series analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rolandone, Frederique; Ryder, Isabelle; Agram, Piyush S.; Burgmann, Roland; Nadeau, Robert M.</p> <p>2010-05-01</p> <p>We exploit the advanced Interferometric Synthetic Aperture Radar (InSAR) technique referred to as the Small BAseline Subset (SBAS) algorithm to analyze the <span class="hlt">creeping</span> section of the San Andreas Fault in Central California. Various geodetic <span class="hlt">creep</span> rate measurements along the Central San Andreas Fault (CSAF) have been made since 1969 including creepmeters, alignment arrays, geodolite, and GPS. They show that horizontal surface displacements increase from a few mm/yr at either end to a maximum of up to ~34 mm/yr in the central portion. They also indicate some discrepancies in rate estimates, with the range being as high as 10 mm/yr at some places along the fault. This variation is thought to be a result of the different geodetic techniques used and of measurements being made at variable distances from the fault. An interferometric stack of 12 interferograms for the period 1992-2001 shows the spatial variation of <span class="hlt">creep</span> that occurs within a narrow (<2 km) zone close to the fault trace. The <span class="hlt">creep</span> rate varies spatially along the fault but also in time. Aseismic slip on the CSAF shows several kinds of time dependence. Shallow slip, as measured by surface measurements across the narrow <span class="hlt">creeping</span> zone, occurs partly as ongoing steady <span class="hlt">creep</span>, along with brief episodes with slip from mm to cm. <span class="hlt">Creep</span> rates along the San Juan Bautista segment increased after the 1989 Loma Prieta earthquake and slow slip transients of varying duration and magnitude occurred in both transition segments The main focus of this work is to use the SBAS technique to identify spatial and temporal variations of <span class="hlt">creep</span> on the CSAF. We will present time series of line-of-sight (LOS) displacements derived from SAR data acquired by the ASAR instrument, on board the ENVISAT satellite, between 2003 and 2009. For each coherent pixel of the radar images we compute time-dependent surface displacements as well as the average LOS <span class="hlt">deformation</span> rate. We compare our results with <span class="hlt">characteristic</span> repeating microearthquakes that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1132965','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1132965"><span id="translatedtitle">Irradiation <span class="hlt">creep</span> of nano-powder sintered silicon carbide at low neutron fluences</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Koyanagi, Takaaki; Shimoda, Kazuya; Kondo, Sosuke; Hinoki, Tatsuya; Ozawa, Kazumi; Katoh, Yutai</p> <p>2014-12-01</p> <p>The irradiation <span class="hlt">creep</span> behavior of nano-powder sintered silicon carbide was investigated using the bend stress relaxation method under neutron irradiation up to 1.9 dpa. The <span class="hlt">creep</span> <span class="hlt">deformation</span> was observed at all temperatures ranging from 380 to 1180 °C mainly from the irradiation <span class="hlt">creep</span> but with the increasing contributions from the thermal <span class="hlt">creep</span> at higher temperatures. Microstructural observation and data analysis were performed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..MARX34010C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MARX34010C"><span id="translatedtitle"><span class="hlt">Creep</span> dynamics in soft matter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cabriolu, Raffaela</p> <p></p> <p>Detecting any precursors of failure in Soft Matter Systems (SMS) is an inter-disciplinary topic with important applications (e.g. prediction of failure in engineering processes). Further, it provides an ideal benchmark to understand how mechanical stress and failure impacts the flow properties of amorphous condensed matter. Furthermore, some SMS are viscoelastic, flowing like viscous liquids or <span class="hlt">deforming</span> like a solid according to applied forces. Often SMS are fragile and local rearrangements trigger catastrophic macroscopic failure. Despite the importance of the topic little is known on the local <span class="hlt">creep</span> dynamics before the occurrence of such catastrophic events. To study <span class="hlt">creep</span> and failure at an atomic/molecular level and at time scales that are not easily accessible by experiments we chose to carry out microscopic simulations. In this work we present the response of a colloidal system to uniaxial tensile stress applied and we compare our results to experimental works [8].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvE..94b3002K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvE..94b3002K"><span id="translatedtitle">Predicting sample lifetimes in <span class="hlt">creep</span> fracture of heterogeneous materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koivisto, Juha; Ovaska, Markus; Miksic, Amandine; Laurson, Lasse; Alava, Mikko J.</p> <p>2016-08-01</p> <p>Materials flow—under <span class="hlt">creep</span> or constant loads—and, finally, fail. The prediction of sample lifetimes is an important and highly challenging problem because of the inherently heterogeneous nature of most materials that results in large sample-to-sample lifetime fluctuations, even under the same conditions. We study <span class="hlt">creep</span> <span class="hlt">deformation</span> of paper sheets as one heterogeneous material and thus show how to predict lifetimes of individual samples by exploiting the "universal" features in the sample-inherent <span class="hlt">creep</span> curves, particularly the passage to an accelerating <span class="hlt">creep</span> rate. Using simulations of a viscoelastic fiber bundle model, we illustrate how <span class="hlt">deformation</span> localization controls the shape of the <span class="hlt">creep</span> curve and thus the degree of lifetime predictability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JAfES..81...28S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JAfES..81...28S"><span id="translatedtitle">Quartz c-axis evidence for <span class="hlt">deformation</span> <span class="hlt">characteristics</span> in the Sanandaj-Sirjan metamorphic belt, Iran</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Samani, Babak</p> <p>2013-05-01</p> <p>Quartz c-axis fabric, finite strain, and kinematic vorticity analyses were carried out in well-exposed quartz mylonites to investigate the heterogeneous nature of ductile <span class="hlt">deformation</span> within the Eghlid <span class="hlt">deformed</span> area in the High Pressure-Low Temperature (HP-LT) Sanandaj-Sirjan metamorphic belt (Zagros Mountains, Iran). This belt belongs to a sequence of tectonometamorphic complexes with low- to high-grade metamorphic rocks affected by a polyphase <span class="hlt">deformation</span> history. Asymmetric quartz c-axis fabrics (type I) confirm a localized top-to-the-southeast sense of shear. Quantitative finite strain analysis in the XZ, XY and YZ principal planes of the finite strain ellipsoid demonstrate that the strain ratio increases towards the thrust planes of the Zagros Thrust System. Kinematic vorticity analysis of <span class="hlt">deformed</span> quartz grains showed sequential variation in the kinematic vorticity number from ˜0.5 to ˜0.8 between the thrust sheets. Such vorticity numbers show that both simple and pure shear components contribute to the <span class="hlt">deformation</span>. Our results show that simple shear dominated <span class="hlt">deformation</span> near the thrust faults, and pure shear dominated <span class="hlt">deformation</span> far from them. Quartz c-axis opening angles suggest <span class="hlt">deformation</span> temperatures range between 450° ± 50 °C and 600° ± 50 °C, which yield greenschist to amphibolite facies conditions during ductile <span class="hlt">deformation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/989906','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/989906"><span id="translatedtitle">In-situ <span class="hlt">Creep</span> Testing Capability Development for Advanced Test Reactor</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>B. G. Kim; J. L. Rempe; D. L. Knudson; K. G. Condie; B. H. Sencer</p> <p>2010-08-01</p> <p><span class="hlt">Creep</span> is the slow, time-dependent strain that occurs in a material under a constant strees (or load) at high temperature. High temperature is a relative term, dependent on the materials being evaluated. A typical <span class="hlt">creep</span> curve is shown in Figure 1-1. In a <span class="hlt">creep</span> test, a constant load is applied to a tensile specimen maintained at a constant temperature. Strain is then measured over a period of time. The slope of the curve, identified in the figure below, is the strain rate of the test during Stage II or the <span class="hlt">creep</span> rate of the material. Primary <span class="hlt">creep</span>, Stage I, is a period of decreasing <span class="hlt">creep</span> rate due to work hardening of the material. Primary <span class="hlt">creep</span> is a period of primarily transient <span class="hlt">creep</span>. During this period, <span class="hlt">deformation</span> takes place and the resistance to <span class="hlt">creep</span> increases until Stage II, Secondary <span class="hlt">creep</span>. Stage II <span class="hlt">creep</span> is a period with a roughly constant <span class="hlt">creep</span> rate. Stage II is referred to as steady-state <span class="hlt">creep</span> because a balance is achieved between the work hardening and annealing (thermal softening) processes. Tertiary <span class="hlt">creep</span>, Stage III, occurs when there is a reduction in cross sectional area due to necking or effective reduction in area due to internal void formation; that is, the <span class="hlt">creep</span> rate increases due to necking of the specimen and the associated increase in local stress.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850006569','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850006569"><span id="translatedtitle"><span class="hlt">Creep</span> of chemically vapor deposited SiC fibers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dicarlo, J. A.</p> <p>1984-01-01</p> <p>The <span class="hlt">creep</span>, thermal expansion, and elastic modulus properties for chemically vapor deposited SiC fibers were measured between 1000 and 1500 C. <span class="hlt">Creep</span> strain was observed to increase logarithmically with time, monotonically with temperature, and linearly with tensile stress up to 600 MPa. The controlling activation energy was 480 + or - 20 kJ/mole. Thermal pretreatments near 1200 and 1450 C were found to significantly reduce fiber <span class="hlt">creep</span>. These results coupled with <span class="hlt">creep</span> recovery observations indicate that below 1400 C fiber <span class="hlt">creep</span> is anelastic with neglible plastic component. This allowed a simple predictive method to be developed for describing fiber total <span class="hlt">deformation</span> as a function of time, temperature, and stress. Mechanistic analysis of the property data suggests that fiber <span class="hlt">creep</span> is the result of beta-SiC grain boundary sliding controlled by a small percent of free silicon in the grain boundaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995MMTA...26.3257B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995MMTA...26.3257B"><span id="translatedtitle">Modeling the minimum <span class="hlt">creep</span> rate of discontinuous lamellar- reinforced composites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bartholomeusz, Michael F.; Wert, John A.</p> <p>1995-12-01</p> <p>An analytical model has been developed to predict the <span class="hlt">creep</span> rate of discontinuous lamellar-reinforced composites in which both phases plastically <span class="hlt">deform</span>. The model incorporates effects associated with lamellar orientation relative to the uniaxial stress axis. For modest to large differences between matrix and reinforcement <span class="hlt">creep</span> rates, lamellar aspect ratio has a significant impact on composite <span class="hlt">creep</span> rate. For a prescribed reinforcing phase volume fraction, microstructural inhomogeneity can have a pronounced effect on composite <span class="hlt">creep</span> properties. In the case of uniaxially aligned rigid lamellar-reinforced composites, an inhomogeneous distribution of reinforcing lamellae in the microstructure substantially increases the composite <span class="hlt">creep</span> rate. Model results demonstrate that there is no significant improvement in <span class="hlt">creep</span> resistance for aligned fiber-reinforced composites compared to aligned lamellar-reinforced composites, unless the reinforcing phase is essentially nondeforming relative to the matrix phase.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003PhDT........16I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003PhDT........16I"><span id="translatedtitle">Modeling <span class="hlt">creep</span> behavior in a directionally solidified nickel base superalloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ibanez, Alejandro R.</p> <p></p> <p>Directionally solidified (DS) nickel-base superalloys provide significant improvements relative to the limitations inherent to equiaxed materials in the areas of <span class="hlt">creep</span> resistance, oxidation, and low and high cycle fatigue resistance. Since these materials are being pushed to the limits of their capability in gas turbine applications, accurate mathematical models are needed to predict the service lives of the hot-section components to prevent unscheduled outages due to sudden mechanical failures. The objectives of this study are to perform critical experiments and investigate the high temperature tensile, fracture toughness, <span class="hlt">creep</span> <span class="hlt">deformation</span>, <span class="hlt">creep</span> rupture and <span class="hlt">creep</span> crack growth behavior of DS GTD111 as well as to apply <span class="hlt">creep</span> <span class="hlt">deformation</span>, rupture and crack growth models that will enable the accurate representation of the life times of the DS GTD111 superalloy gas turbine components that are exposed to high temperatures under sustained tensile stresses. The applied models will be capable of accurately representing the <span class="hlt">creep</span> <span class="hlt">deformation</span>, rupture and crack growth behavior as a function of stress, time and temperature. The yield strength and fracture toughness behavior with temperature is governed by the gamma particles. The longitudinal direction showed higher ductility and strength than the transverse direction. The TL direction exhibited higher fracture toughness than the LT orientation because the crack follows a more tortuous path. The longitudinal direction showed higher <span class="hlt">creep</span> ductility, lower minimum strain rates and longer <span class="hlt">creep</span> rupture times than the transverse direction. The results in the transverse direction were similar to the ones for the equiaxed version of this superalloy. Two models for <span class="hlt">creep</span> <span class="hlt">deformation</span> have been evaluated. The power-law model includes a secondary and a tertiary <span class="hlt">creep</span> term with the primary <span class="hlt">creep</span> represented by a constant. A theta-projection model has also been evaluated and it appears to provide a more accurate representation of <span class="hlt">creep</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1168621','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1168621"><span id="translatedtitle"><span class="hlt">CREEP</span> AND <span class="hlt">CREEP</span>-FATIGUE OF ALLOY 617 WELDMENTS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wright, Jill; Carroll, Laura; Wright, Richard</p> <p>2014-08-01</p> <p>The Very High Temperature Reactor (VHTR) Intermediate Heat Exchanger (IHX) may be joined to piping or other components by welding. <span class="hlt">Creep</span>-fatigue <span class="hlt">deformation</span> is expected to be a predominant failure mechanism of the IHX1 and thus weldments used in its fabrication will experience varying cyclic stresses interrupted by periods of elevated temperature <span class="hlt">deformation</span>. These periods of elevated temperature <span class="hlt">deformation</span> are greatly influenced by a materials’ <span class="hlt">creep</span> behavior. The nickel-base solid solution strengthened alloy, Alloy 617, is the primary material candidate for a VHTR-type IHX, and it is expected that Alloy 617 filler metal will be used for welds. Alloy 617 is not yet been integrated into Section III of the Boiler and Pressure Vessel Code, however, nuclear component design with Alloy 617 requires ASME (American Society of Mechanical Engineers) Code qualification. The Code will dictate design for welded construction through significant performance reductions. Despite the similar compositions of the weldment and base material, significantly different microstructures and mechanical properties are inevitable. Experience of nickel alloy welds in structural applications suggests that most high temperature failures occur at the weldments or in the heat-affected zone. Reliably guarding against this type of failure is particularly challenging at high temperatures due to the variations in the inelastic response of the constituent parts of the weldment (i.e., weld metal, heat-affected zone, and base metal) [ref]. This work focuses on the <span class="hlt">creep</span>-fatigue behavior of nickel-based weldments, a need noted during the development of the draft Alloy 617 ASME Code Case. An understanding of Alloy 617 weldments when subjected to this important <span class="hlt">deformation</span> mode will enable determination of the appropriate design parameters associated with their use. Specifically, the three main areas emphasized are the performance reduction due to a weld discontinuity in terms of the reduced number of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JMBM...24...19D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JMBM...24...19D"><span id="translatedtitle"><span class="hlt">Creep</span> relaxation and fully reversible <span class="hlt">creep</span> of foam core sandwich composites in seawater</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de la Paz, Ismael; Shafiq, Basir</p> <p>2015-12-01</p> <p>Foam core sandwich composites were subjected to (i) <span class="hlt">creep</span> to failure, (ii) cyclic <span class="hlt">creep</span>-relaxation and (iii) fully reversible cyclic <span class="hlt">creep</span> loading in seawater in order to mimic an actual ship hull's service lifetime scenario. The results indicate a strong dependence of lifetime on the mode of loading. A significant reduction in the overall life was observed under cyclic <span class="hlt">creep</span> as compared with the conventional <span class="hlt">creep</span> to failure. <span class="hlt">Creep</span> relaxation (R=1) tests were performed at loading-relaxation periods of 24/24, 24/12, 24/6, 12/12 and 6/6 h, while the fully reversible (R=-1) <span class="hlt">creep</span> tests were conducted at loading-reversed loading times of 36/36, 24/24, 12/12, 6/6, and 3/3 h. The results suggest that <span class="hlt">creep</span>-relaxation lifetime <span class="hlt">characteristics</span> depend predominantly on the relaxation time as opposed to loading times, i.e. longer relaxation periods lead to shorter life. Whereas, fully reversible <span class="hlt">creep</span> appears to be dependent upon the number of reversals whereby, life is observed to reduce as the number of reversals increase. These significant observations are explained in terms of various possible paths to interface cell wall collapse. Modes of failure were predominantly indentation and core compression in the vicinity of the loading site.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/7055246','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/7055246"><span id="translatedtitle">Unified <span class="hlt">creep</span>-plasticity model for halite</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Krieg, R. D.</p> <p>1980-11-01</p> <p>There are two national energy programs which are considering caverns in geological salt (NaCl) as a storage repository. One is the disposal of nuclear wastes and the other is the storage of oil. Both short-time and long-time structural <span class="hlt">deformations</span> and stresses must be predictable for these applications. At 300K, the nominal initial temperature for both applications, the salt is at 0.28 of the melting temperature and exhibits a significant time dependent behavior. A constitutive model has been developed which describes the behavior observed in an extensive set of triaxial <span class="hlt">creep</span> tests. Analysis of these tests showed that a single <span class="hlt">deformation</span> mechanism seems to be operative over the stress and temperature range of interest so that the secondary <span class="hlt">creep</span> data can be represented by a power of the stress over the entire test range. This simple behavior allowed a new unified <span class="hlt">creep</span>-plasticity model to be applied with some confidence. The resulting model recognizes no inherent difference between plastic and <span class="hlt">creep</span> strains yet models the total inelastic strain reasonably well including primary and secondary <span class="hlt">creep</span> and reverse loadings. A multiaxial formulation is applied with a back stress. A Bauschinger effect is exhibited as a consequence and is present regardless of the time scale over which the loading is applied. The model would be interpreted as kinematic hardening in the sense of classical plasticity. Comparisons are made between test data and model behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JMEP...25.1191Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMEP...25.1191Z"><span id="translatedtitle">Hot <span class="hlt">Deformation</span> <span class="hlt">Characteristics</span> and Processing Maps of the Cu-Cr-Zr-Ag Alloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Yi; Chai, Zhe; Volinsky, Alex A.; Sun, Huili; Tian, Baohong; Liu, Ping; Liu, Yong</p> <p>2016-03-01</p> <p>The hot <span class="hlt">deformation</span> behavior of the Cu-Cr-Zr-Ag alloy has been investigated by hot compressive tests in the 650-950 °C temperature and 0.001-10 s-1 strain rate ranges using Gleeble-1500D thermo-mechanical simulator. The microstructure evolution of the alloy during <span class="hlt">deformation</span> was characterized using optical and transmission electron microscopy. The flow stress decreases with the <span class="hlt">deformation</span> temperature and increases with the strain rate. The apparent activation energy for hot <span class="hlt">deformation</span> of the alloy was 343.23 kJ/mol. The constitutive equation of the alloy based on the hyperbolic-sine equation was established to characterize the flow stress as a function of the strain rate and the <span class="hlt">deformation</span> temperature. The processing maps were established based on the dynamic material model. The optimal processing parameters for hot <span class="hlt">deformation</span> of the Cu-Cr-Zr-Ag alloy are 900-950 °C and 0.001-0.1 s-1 strain rate. The evolution of DRX microstructure strongly depends on the <span class="hlt">deformation</span> temperature and the strain rate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JMEP...25..374M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JMEP...25..374M&link_type=ABSTRACT"><span id="translatedtitle">Effect of Preaging <span class="hlt">Deformation</span> on Aging <span class="hlt">Characteristics</span> of 2507 Super Duplex Stainless Steel</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mishra, M. K.; Rao, A. G.; Sarkar, R.; Kashyap, B. P.; Prabhu, N.</p> <p>2016-02-01</p> <p>In the present study, precipitation of sigma (σ) phase was investigated over the temperature range of 700-850 °C in undeformed and <span class="hlt">deformed</span> (60% cold rolling) samples of 2507 super duplex stainless steel. The fraction of sigma phase formed as a result of the transformation α → σ + γ2 increases with increasing time and temperature. The increase in sigma phase leads to increase in yield strength and decrease in ductility. Preaging <span class="hlt">deformation</span> leads to accelerated precipitation of sigma phase. The activation energy for sigma phase precipitation in <span class="hlt">deformed</span> sample is found to be lower than that in undeformed sample.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014MMTA...45.6053L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014MMTA...45.6053L&link_type=ABSTRACT"><span id="translatedtitle">Analysis of the <span class="hlt">Deformation</span> Behavior in Tension and Tension-<span class="hlt">Creep</span> of Ti-3Al-2.5V (wt pct) at 296 K and 728 K (23 °C and 455 °C) Using In Situ SEM Experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Hongmei; Boehlert, Carl J.; Bieler, Thomas R.; Crimp, Martin A.</p> <p>2014-12-01</p> <p>The <span class="hlt">deformation</span> behavior of a Ti-3Al-2.5V (wt pct) near-α alloy was investigated during in situ <span class="hlt">deformation</span> inside a scanning electron microscopy (SEM). Two plates with distinct textures were examined. Tensile experiments were performed at 296 K and 728 K (455 °C) (~0.4 T m), while a tensile-<span class="hlt">creep</span> experiment was performed at 728 K (455 °C) and 180 MPa ( σ/ σ ys = 0.72). The active <span class="hlt">deformation</span> systems were identified in the α phase using electron backscattered diffraction based slip-trace analysis and SEM images of the surface. Prismatic slip <span class="hlt">deformation</span> was the dominant slip mode observed for all the experiments in both plates, which was supported by a critical resolved shear stress (CRSS) ratio analysis. However, due to the texture of plate 1, which strongly favored the activation of prismatic slip, the percentages of prismatic slip activity for specimens from plate 1 tested at 296 K and 728 K (23 °C and 455 °C) were higher than the specimens from plate 2 under the same testing conditions. T1 twinning was an active <span class="hlt">deformation</span> mode at both 296 K and 728 K (23 °C and 455 °C), but the extent of twinning activity decreased with increased temperature. T1 twinning was more frequently observed in specimens from plate 2, which exhibited a higher fraction of twinning systems favoring activation at both 296 K and 728 K (23 °C and 455 °C). The tension-<span class="hlt">creep</span> experiment revealed less slip and more grain boundary sliding than in the higher strain rate tensile experiments. Using a previously demonstrated bootstrapping statistical analysis methodology, the relative CRSS ratios of prismatic, pyramidal < a>, pyramidal < c+ a>, and T1 twinning <span class="hlt">deformation</span> systems compared with basal slip were calculated and discussed in light of similar measurements made on CP Ti and Ti-5Al-2.5Sn (wt pct).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016HTMP...35..188A&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016HTMP...35..188A&link_type=ABSTRACT"><span id="translatedtitle">Small Two-Bar Specimen <span class="hlt">Creep</span> Testing of Grade P91 Steel at 650°C</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ali, Balhassn S. M.; Hyde, Tom H.; Sun, Wei</p> <p>2016-03-01</p> <p>Commonly used small <span class="hlt">creep</span> specimen types, such as ring and impression <span class="hlt">creep</span> specimens, are capable of providing minimum <span class="hlt">creep</span> strain rate data from small volumes of material. However, these test types are unable to provide the <span class="hlt">creep</span> rupture data. In this paper the recently developed two-bar specimen type, which can be used to obtain minimum <span class="hlt">creep</span> strain rate and <span class="hlt">creep</span> rupture <span class="hlt">creep</span> data from small volumes of material, is described. Conversion relationships are used to convert (i) the applied load to the equivalent uniaxial stress, and (ii) the load line <span class="hlt">deformation</span> rate to the equivalent uniaxial <span class="hlt">creep</span> strain rate. The effects of the specimen dimension ratios on the conversion factors are also discussed in this paper. This paper also shows comparisons between two-bar specimen <span class="hlt">creep</span> test data and the corresponding uniaxial <span class="hlt">creep</span> test data, for grade P91 steel at 650°C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26899951','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26899951"><span id="translatedtitle">Molecular dynamics simulations of the atom packing <span class="hlt">characteristics</span> of three <span class="hlt">deformed</span> silver nanoparticles at room temperature.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Lin</p> <p>2016-03-14</p> <p><span class="hlt">Deformation</span> is of significance in controlling the shape of materials, but the key structural information of metal nanoparticles is still limited. Molecular dynamics simulations are performed to explore the microscopic details of atom packing differences in three <span class="hlt">deformed</span> silver nanoparticles with one atom difference. Analytical tools are used to demonstrate the effects of external load and surface atoms of particles on the packing patterns in these <span class="hlt">deformed</span> nanoparticles including internal energy per atom, pair numbers, and pair distribution functions as well as cross-sectional images. The simulation results show that under small compression, the particles present elastic behaviors. The increasing compression results in the sliding of the atoms in different parts of these particles, and some interfaces are formed between these parts. As the external load becomes large, these <span class="hlt">deformed</span> particles are compressed into the thickness of several atomic layers. The unloaded particles present different behaviors. PMID:26899951</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790014393','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790014393"><span id="translatedtitle">Endochronic theory of transient <span class="hlt">creep</span> and <span class="hlt">creep</span> recovery</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wu, H. C.; Chen, L.</p> <p>1979-01-01</p> <p>Short time <span class="hlt">creep</span> and <span class="hlt">creep</span> recovery were investigated by means of the endochronic theory of viscoplasticity. It is shown that the constitutive equations for constant-strain-rate stress-strain behavior, <span class="hlt">creep</span>, <span class="hlt">creep</span> recovery, and stress relaxation can all ber derived from the general constitutive equation by imposing appropriate constraints. In this unified approach, the effect of strain-hardening is naturally accounted for when describing <span class="hlt">creep</span> and <span class="hlt">creep</span> recovery. The theory predicts with reasonable accuracy the <span class="hlt">creep</span> and <span class="hlt">creep</span> recovery behaviors for Aluminum 1100-0 at 150 C. It was found that the strain-rate history at prestraining stage affects the subsequent <span class="hlt">creep</span>. A critical stress was also established for <span class="hlt">creep</span> recovery. The theory predicts a forward <span class="hlt">creep</span> for <span class="hlt">creep</span> recovery stress greater than the critical stress. For <span class="hlt">creep</span> recovery stress less than the critical stress, the theory then predicts a normal strain recovery.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JMEP...23.2858O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JMEP...23.2858O"><span id="translatedtitle">Material Parameters for <span class="hlt">Creep</span> Rupture of Austenitic Stainless Steel Foils</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Osman, H.; Borhana, A.; Tamin, M. N.</p> <p>2014-08-01</p> <p><span class="hlt">Creep</span> rupture properties of austenitic stainless steel foil, 347SS, used in compact recuperators have been evaluated at 700 °C in the stress range of 54-221 MPa to establish the baseline behavior for its extended use. <span class="hlt">Creep</span> curves of the foil show that the primary <span class="hlt">creep</span> stage is brief and <span class="hlt">creep</span> life is dominated by tertiary <span class="hlt">creep</span> <span class="hlt">deformation</span> with rupture lives in the range of 10-2000 h. Results are compared with properties of bulk specimens tested at 98 and 162 MPa. Thin foil 347SS specimens were found to have higher <span class="hlt">creep</span> rates and higher rupture ductility than their bulk specimen counterparts. Power law relationship was obtained between the minimum <span class="hlt">creep</span> rate and the applied stress with stress exponent value, n = 5.7. The value of the stress exponent is indicative of the rate-controlling <span class="hlt">deformation</span> mechanism associated with dislocation <span class="hlt">creep</span>. Nucleation of voids mainly occurred at second-phase particles (chromium-rich M23C6 carbides) that are present in the metal matrix by decohesion of the particle-matrix interface. The improvement in strength is attributed to the precipitation of fine niobium carbides in the matrix that act as obstacles to the movement of dislocations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014HTMP...33..447L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014HTMP...33..447L"><span id="translatedtitle">Microstructure and <span class="hlt">Creep</span> Property of Isothermal Forging GH4169G Superalloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Zhenrong; Ma, Chunlei; Tian, Sugui; Chen, Liqing; Liu, Xianghua</p> <p>2014-09-01</p> <p>By means of direct aging, microstructure observation and <span class="hlt">creep</span> property measurement, the microstructure and <span class="hlt">creep</span> behaviors of GH4169G superalloy are investigated. Results show that, after direct aging, the grain size is inhomogeneous in the alloy, and some δ precipitates discontinuously distribute in the grain and along the boundaries, which may improve the bonding strength of the boundaries. Under the experimental conditions, the <span class="hlt">creep</span> activation energy of the alloy during steady-state <span class="hlt">creep</span> are calculated to be Q = 594.7 kJ/mol. During <span class="hlt">creep</span>, the <span class="hlt">deformation</span> features of the alloy are twinning <span class="hlt">deformation</span> and dislocations slipping in the matrix. As <span class="hlt">creep</span> goes on, <span class="hlt">deformed</span> dislocations pile up near the boundary regions to induce stress concentration for promoting the initiation and propagation of cracks along boundaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/9758','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/9758"><span id="translatedtitle">Transient Analysis for the Multimechanism-<span class="hlt">Deformation</span> Parameters of Several Domal Salts</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Munson, Darrell E.</p> <p>1999-08-16</p> <p>Use of Gulf Coast salt domes for construction of very large storage caverns by solution mining has grown significantly in the last several decades. In fact, a nationally important Strategic Petroleum Reserve (SPR) storage occurs in large cavern arrays in some of these domes. Although caverns have been operated economically for these many years, these caverns have a range of relatively poorly understood behaviors, involving <span class="hlt">creep</span> closure fluid loss and damage from salt falls. It is certainly possible to postulate that many of these behaviors stem from geomechanical or <span class="hlt">deformational</span> aspects of the salt response. As a result, a method of correlating the cavern response to mechanical <span class="hlt">creep</span> behavior as determined in the laboratory could be of considerable importance. Recently, detailed study of the <span class="hlt">creep</span> response of domal salts has cast some insight into the influence of different salt origins on cavern behavior. The study used a simple graphical analysis of the limited non-steady state data to give a bound, or an approach to steady state, as an estimate of the steady state behavior of a given domal salt. This permitted the analysis of sparse <span class="hlt">creep</span> databases for domal salts. It appears that a shortcoming of the steady state analysis was in masking some of the salt material differences. In an attempt to overcome the steady state analysis shortcomings, a method was developed based on the integration of the Multimechanism-<span class="hlt">Deformation</span> (M-D) <span class="hlt">creep</span> constitutive model to fit the transient response. This integration process essentially permits definition of the material sensitive parameters of the model, while those parameters that are either constants or material insensitive parameters are fixed independently. The transient analysis method has proven more sensitive to differences in the <span class="hlt">creep</span> <span class="hlt">characteristics</span> and has provided a way of defining different behaviors within a given dome. <span class="hlt">Creep</span> <span class="hlt">characteristics</span>, as defined by the transient analysis of the <span class="hlt">creep</span> rate, are related</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/10450408','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/10450408"><span id="translatedtitle">Number and type of vertebral <span class="hlt">deformities</span>: epidemiological <span class="hlt">characteristics</span> and relation to back pain and height loss. European Vertebral Osteoporosis Study Group.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ismail, A A; Cooper, C; Felsenberg, D; Varlow, J; Kanis, J A; Silman, A J; O'Neill, T W</p> <p>1999-01-01</p> <p>Vertebral <span class="hlt">deformity</span> is the classical hallmark of osteoporosis. Three types of vertebral <span class="hlt">deformity</span> are usually described: crush, wedge and biconcave <span class="hlt">deformities</span>. However, there are few data concerning the descriptive epidemiology of the individual <span class="hlt">deformity</span> types, and differences in their underlying pathogenesis and clinical impact remain uncertain. The aim of this study was to compare the epidemiological <span class="hlt">characteristics</span> of the three types of vertebral <span class="hlt">deformity</span> and to explore the relationships of the number and type of <span class="hlt">deformity</span> with back pain and height loss. Age-stratified random samples of men and women aged 50 years and over were recruited from population registers in 30 European centers (EVOS study). Subjects were invited to attend for an interviewer-administered questionnaire and lateral spinal radiographs. The presence, type and number of vertebral <span class="hlt">deformities</span> was determined using the McCloskey-Kanis algorithm. A total of 13,562 men and women were studied; mean age in men was 64.4 years (SD 8.5), and in women 63.8 years (SD 8.5 years). There was evidence of variation in the occurrence of wedge, crush and biconcave <span class="hlt">deformity</span> by age, sex and vertebral level. Wedge <span class="hlt">deformities</span> were the most frequent <span class="hlt">deformity</span> and tended to cluster at the mid-thoracic and thoraco-lumbar regions of the spine in both men and women. Similar predilection for these sites was observed for crush and to a lesser extent biconcave <span class="hlt">deformities</span> though this was much less marked than for wedge <span class="hlt">deformities</span>. In both sexes the frequency of biconcave <span class="hlt">deformities</span> was higher in the lumbar than the thoracic spine and unlike the other <span class="hlt">deformity</span> types it did not decline in frequency at lower lumbar vertebral levels. The prevalence of all three types of vertebral <span class="hlt">deformity</span> increased with age and was more marked in women. There were no important differences in the effect of age on the different <span class="hlt">deformity</span> types. All types of <span class="hlt">deformity</span> were associated with height loss, which was greatest for individuals</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMMR33A1659O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMMR33A1659O"><span id="translatedtitle">Transition between dislocation <span class="hlt">creep</span> and diffusion <span class="hlt">creep</span> in upper greenschist- to lower amphibolite-facies metacherts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Okudaira, T.; Ogawa, D.; Miyazaki, T.; Michibayashi, K.</p> <p>2009-12-01</p> <p>To clarify the dominant <span class="hlt">deformation</span> mechanism in continental middle crust at an arc-trench system, we used an SEM-EBSD system to measure the lattice-preferred orientations of quartz grains in fine-grained (~10 μm) metachert from the low-grade (chlorite and chlorite-biotite zones) part of the Ryoke metamorphic belt, SW Japan. The metacherts are composed mainly by quartz (> 94 vol.%), with small amounts of chlorite, muscovite and biotite. Quartz grain-sizes vary from 9 to 20 μm in diameter; grain sizes of quartz are weakly related to quartz modal abundances. Quartz c-axis fabrics do not exhibit distinct patterns that could be formed by dislocation <span class="hlt">creep</span>. Fabric intensities are calculated: values of fabric intensity index proposed by Lisle (1985) and those of by Skemer et al. (2005), that is 'M-index', are 0.060-0.074 and 0.027-0.073, respectively. These values are very small, indicating that the quartz c-axis fabric patterns are comparable with a random distribution. In these samples, there are <span class="hlt">deformed</span> radiolarian fossils and they are used as strain marker to analyze strain geometry and magnitude of the metacherts. According to the results of strain analysis using Rφ-f method, k-value and strain magnitude are 0.4-1.0 and 0.6-0.7, respectively. The strain magnitude is enough to form distinct fabric patterns, when dislocation <span class="hlt">creep</span> is a dominant <span class="hlt">deformation</span> mechanism. Therefore, in the metachert samples studied here, it suggests that dominant <span class="hlt">deformation</span> mechanism is not dislocation <span class="hlt">creep</span>, but diffusion <span class="hlt">creep</span>. Although, when the grain size of quartz is ~10 mm, shear stress is ~several tens megapascal and upper greenschist- to lower amphibolite-facies condition (~500°C at 200-300 MPa), it has been considered that high-strained natural quartzose rocks, e.g., quartz-rich layers in banded ultramylonites, <span class="hlt">deformed</span> by dislocation <span class="hlt">creep</span>, the very-fine grained metacherts from the Ryoke metamorphic belt formed under the upper greenschist- to lower amphibolite</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6136555','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6136555"><span id="translatedtitle"><span class="hlt">Creep</span> <span class="hlt">deformation</span> of a two-phase TiAl/Ti[sub 3]Al lamellar alloy and the individual TiAl and Ti[sub 3]Al constituent phases</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bartholomeusz, M.F.; Wert, J.A. ); Qibin Yang )</p> <p>1993-08-01</p> <p>Two-phase TiAl/Ti[sub 3]Al alloys in which the constituent phases form a lamellar microstructure are reported to possess good combinations of low-temperature fracture toughness, tensile strength and fatigue resistance. However, information about the high-temperature <span class="hlt">creep</span> properties of the two-phase TiAl/Ti[sub 3]Al alloys with lamellar microstructures (referred to as lamellar alloys in the remainder of the paper) is limited. Based on a simple rule of mixtures model of strength, it would be expected that the <span class="hlt">creep</span> rates of the lamellar alloy would be between the <span class="hlt">creep</span> rates of TiAl and Ti[sub 3]Al. In contrast to composite model predictions of strength, Polvani and coworkers found that the minimum <span class="hlt">creep</span> rates of two duplex alloys, a [gamma]/[gamma][prime] nickel-base superalloy and NiAl/Ni[sub 2]AlTi, were significantly lower than the minimum <span class="hlt">creep</span> rates of either of the constituent phases. They also reported that most dislocations in the two-phase NiAl/Ni[sub 2]AlTi alloy were contained within the semi-coherent interfacial dislocation networks between the two phases. Based on this observation they proposed that the <span class="hlt">creep</span> rate is controlled by the rate at which dislocations moving through both phases are emitted and absorbed by the interphase dislocation networks. The greater strain hardening rate of the lamellar TiAl/Ti[sub 3]Al alloy suggests that it may exhibit lower steady-state <span class="hlt">creep</span> rates that the individual constituent phases. The objective of the present study is to evaluate the <span class="hlt">creep</span> properties of a TiAl/ Ti[sub 3]Al lamellar alloy and of the individual constituent phases. In this paper, the results of this investigation will be presented and compared with previously published results for this alloy system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFMMR51A..01S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFMMR51A..01S&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Creep</span> Behavior of Organic-Rich Shales - Evidences of Microscale Strain Partitioning</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sone, H.; Morales, L. F. G.; Dresen, G. H.</p> <p>2015-12-01</p> <p>Laboratory <span class="hlt">creep</span> experiments conducted using organic-rich shales show that these rocks exhibit some ductility under sustained loading conditions although they may appear to be elastic and brittle (Young's modulus 15-80 GPa) at shorter time scales. At room-temperature and in-situ pressure conditions, <span class="hlt">creep</span> strain observed after 3 hours of sustained loading reach strains on the order of 10-5per megapascal of applied differential stress. The <span class="hlt">creep</span> behavior is highly anisotropic such that <span class="hlt">creep</span> occurs more in the direction perpendicular to the bedding plane than in the direction parallel to the bedding plane. In general, we find that the <span class="hlt">creep</span> behavior is largely controlled by the amount of clay mineral and organic content. This is also supported by evidences of elastic stiffening and sample volume reduction during <span class="hlt">creep</span> which imply that the <span class="hlt">creep</span> is accommodated by localized compaction occurring within clay-aggregates and/or organic materials, the relatively porous members in the rock. We also find that the tendency to <span class="hlt">creep</span> has a unique relation with the Young's modulus regardless of the loading direction or the mineral composition. Sone and Zoback (2013) explained this correlation by appealing to the stress partitioning behavior that occurs between the relatively stiff and soft components of the rock, and also by assuming that <span class="hlt">creep</span> only occurs within the soft components, namely the clay and organic contents, with a specific local 3-hour <span class="hlt">creep</span> compliance value of 10-4 MPa-1. In order to confirm that such strain-partitioning occurs during <span class="hlt">creep</span> <span class="hlt">deformation</span>, we also performed <span class="hlt">creep</span> experiments under a scanning electron microscope using a <span class="hlt">deformation</span> stage setup. Such experiments allow us to directly observe the <span class="hlt">deformation</span> and quantify the strain-partitioning occurring between the different mineral constituents with the aid of digital image correlation analysis. Results suggest that strain-partitioning do occur during <span class="hlt">creep</span> <span class="hlt">deformation</span> and inferred <span class="hlt">creep</span> properties of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GGG....15.1515S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GGG....15.1515S"><span id="translatedtitle">Central Cascadia subduction zone <span class="hlt">creep</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmalzle, Gina M.; McCaffrey, Robert; Creager, Kenneth C.</p> <p>2014-04-01</p> <p>Cascadia between 43°N and 46°N has reduced interseismic uplift observed in geodetic data and coseismic subsidence seen in multiple thrust earthquakes, suggesting elevated persistent fault <span class="hlt">creep</span> in this section of the subduction zone. We estimate subduction thrust "decade-scale" locking and crustal block rotations from three-component continuous Global Positioning System (GPS) time series from 1997 to 2013, as well as 80 year tide gauge and leveling-derived uplift rates. Geodetic observations indicate coastal central Oregon is rising at a slower rate than coastal Washington, southern Oregon and northern California. Modeled locking distributions suggest a wide locking transition zone that extends inland under central Oregon. Paleoseismic records of multiple great earthquakes along Cascadia indicate less subsidence in central Oregon. The Cascade thrust under central Oregon may be partially <span class="hlt">creeping</span> for at least 6500 years (the length of the paleoseismic record) reducing interseismic uplift and resulting in reduced coseismic subsidence. Large accretions of Eocene age basalt (Siletzia terrane) between 43°N and 46°N may be less permeable compared to surrounding terranes, potentially increasing pore fluid pressures along the fault interface resulting in a wide zone of persistent fault <span class="hlt">creep</span>. In a separate inversion, three-component GPS time series from 1 July 2005 to 1 January 2011 are used to estimate upper plate <span class="hlt">deformation</span>, locking between slow-slip events (SSEs), slip from 16 SSEs and an earthquake mechanism. Cumulative SSEs and tectonic tremor are weakest between 43°N and 46°N where partial fault <span class="hlt">creep</span> is increased and Siletzia terrane is thick, suggesting that surrounding rock properties may influence the mode of slip.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JMEP...23.3467F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JMEP...23.3467F"><span id="translatedtitle">Effect of Phosphorous Inoculation on <span class="hlt">Creep</span> Behavior of a Hypereutectic Al-Si Alloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Faraji, Masoumeh; Khalilpour, Hamid</p> <p>2014-10-01</p> <p><span class="hlt">Creep</span> behavior of Al-Si hypereutectic alloys inoculated with phosphorus was investigated using the impression <span class="hlt">creep</span> testing. The results showed that at stress regimes of up to 400-450 MPa and temperatures up to 300 °C, no significant <span class="hlt">creep</span> <span class="hlt">deformation</span> occurred in both uninoculated and inoculated specimens; however, at temperatures above 300 °C, the inoculated alloys presented better <span class="hlt">creep</span> properties. <span class="hlt">Creep</span> data were used to calculate the stress exponent of steady-state <span class="hlt">creep</span> rate, n, and <span class="hlt">creep</span> activation energy, Q, for different additive conditions where n was found varied between 5 and 8. Owing to the fact that most alloys have lower values for n (4, 5), threshold stress was estimated for studied conditions. The <span class="hlt">creep</span> governing mechanisms for different conditions are discussed here, with a particular attention to the effect of phosphorous addition on the microstructural features, including number of primary silicon particles, mean primary silicon spacing, and morphology and distribution of eutectic silicon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.1055D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.1055D"><span id="translatedtitle">Interface Evolution During Transient Pressure Solution <span class="hlt">Creep</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dysthe, D. K.; Podladchikov, Y. Y.; Renard, F.; Jamtveit, B.; Feder, J.</p> <p></p> <p>When aggregates of small grains are pressed together in the presence of small amounts of solvent the aggregate compacts and the grains tend to stick together. This hap- pens to salt and sugar in humid air, and to sediments when buried in the Earths crust. Stress concentration at the grain contacts cause local dissolution, diffusion of the dissolved material out of the interface and deposition on the less stressed faces of the grains{1}. This process, in geology known as pressure solution, plays a cen- tral role during compaction of sedimentary basins{1,2}, during tectonic <span class="hlt">deformation</span> of the Earth's crust{3}, and in strengthening of active fault gouges following earth- quakes{4,5}. Experimental data on pressure solution has so far not been sufficiently accurate to understand the transient processes at the grain scale. Here we present ex- perimental evidence that pressure solution <span class="hlt">creep</span> does not establish a steady state inter- face microstructure as previously thought. Conversely, cumulative <span class="hlt">creep</span> strain and the <span class="hlt">characteristic</span> size of interface microstructures grow as the cubic root of time. A sim- ilar transient phenomenon is known in metallurgy (Andrade <span class="hlt">creep</span>) and is explained here using an analogy with spinodal dewetting. 1 Weyl, P. K., Pressure solution and the force of crystallization - a phenomenological theory. J. Geophys. Res., 64, 2001-2025 (1959). 2 Heald, M. T., Cementation of Simpson and St. Peter Sandstones in parts of Okla- homa, Arkansas and Missouri, J. Geol. Chicago, 14, 16-30 (1956). 3 Schwartz, S., Stöckert, B., Pressure solution in siliciclastic HP-LT metamorphic rocks constraints on the state of stress in deep levels of accretionary complexes. Tectonophysics, 255, 203-209 (1996). 4 Renard, F., Gratier, J.P., Jamtveit, B., Kinetics of crack-sealing, intergranular pres- sure solution, and compaction around active faults. J. Struct. Geol., 22, 1395-1407, (2000). 5 Miller, S. A., BenZion, Y., Burg, J. P.,A three-dimensional fluid-controlled earth</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT........15I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT........15I"><span id="translatedtitle">Probabilistic models for <span class="hlt">creep</span>-fatigue in a steel alloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ibisoglu, Fatmagul</p> <p></p> <p>In high temperature components subjected to long term cyclic operation, simultaneous <span class="hlt">creep</span> and fatigue damage occur. A new methodology for <span class="hlt">creep</span>-fatigue life assessment has been adopted without the need to separate <span class="hlt">creep</span> and fatigue damage or expended life. Probabilistic models, described by hold times in tension and total strain range at temperature, have been derived based on the <span class="hlt">creep</span> rupture behavior of a steel alloy. These models have been validated with the observed <span class="hlt">creep</span>-fatigue life of the material with a scatter band close to a factor of 2. Uncertainties of the <span class="hlt">creep</span>-fatigue model parameters have been estimated with WinBUGS which is an open source Bayesian analysis software tool that uses Markov Chain Monte Carlo method to fit statistical models. Secondly, <span class="hlt">creep</span> <span class="hlt">deformation</span> in stress relaxation data has been analyzed. Well performing <span class="hlt">creep</span> equations have been validated with the observed data. The <span class="hlt">creep</span> model with the highest goodness of fit among the validated models has been used to estimate probability of exceedance at 0.6% strain level for the steel alloy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JNuM..412...82C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JNuM..412...82C"><span id="translatedtitle"><span class="hlt">Creep</span> behaviour of modified 9Cr-1Mo ferritic steel</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Choudhary, B. K.; Isaac Samuel, E.</p> <p>2011-05-01</p> <p><span class="hlt">Creep</span> <span class="hlt">deformation</span> and fracture behaviour of indigenously developed modified 9Cr-1Mo steel for steam generator (SG) tube application has been examined at 823, 848 and 873 K. <span class="hlt">Creep</span> tests were performed on flat <span class="hlt">creep</span> specimens machined from normalised and tempered SG tubes at stresses ranging from 125 to 275 MPa. The stress dependence of minimum <span class="hlt">creep</span> rate obeyed Norton's power law. Similarly, the rupture life dependence on stress obeyed a power law. The fracture mode remained transgranular at all test conditions examined. The analysis of <span class="hlt">creep</span> data indicated that the steel obey Monkman-Grant and modified Monkman-Grant relationships and display high <span class="hlt">creep</span> damage tolerance factor. The tertiary <span class="hlt">creep</span> was examined in terms of the variations of time to onset of tertiary <span class="hlt">creep</span> with rupture life, and a recently proposed concept of time to reach Monkman-Grant ductility, and its relationship with rupture life that depends only on damage tolerance factor. SG tube steel exhibited <span class="hlt">creep</span>-rupture strength comparable to those reported in literature and specified in the nuclear design code RCC-MR.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013IJMPS..2460012C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013IJMPS..2460012C"><span id="translatedtitle">Investigation of Uncertainty from <span class="hlt">Creep</span> and <span class="hlt">Creep</span> Recovery of Force Calibration Result in Accordance with ISO 376:2011</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chaemthet, Kittipong; Amornsakun, Chanchai; Sumyong, Noppadon; Changpan, Tawat; Heamawatanachai, Sumet</p> <p></p> <p>This paper presents an investigation of the uncertainties from <span class="hlt">creep</span> and <span class="hlt">creep</span> recovery of force proving instruments calibrated at NIMT in year 2012 and 2013. In this study, the NIMT's 100kN deadweight force standard machine was used as a standard to calibrate force proving instruments (from various manufacturers and models) in accordance with ISO 376:2011. The comparison of <span class="hlt">creep</span> uncertainties calculated from <span class="hlt">creep</span> measured at maximum load (Cmax), <span class="hlt">creep</span> recovery measured at zero load (Czero) and reversibility errors were also investigated. The results of this study show that, for most of the calibration results (>60%), the maximum value between WCmax/WCzero and WCzero/WCmax were larger than 2. Indicating that, WCmax and WCzero could not assume to be equal. For the comparison between <span class="hlt">creep</span> uncertainties calculated from <span class="hlt">creep</span> error and reversibility error, more than 80% of the calibration results, the <span class="hlt">creep</span> uncertainties calculated from reversibility were larger than 3 time of the calculated values form <span class="hlt">creep</span> measurement. These gave conclusion that, for the unknown history of <span class="hlt">creep</span> and reversibility <span class="hlt">characteristic</span> of instruments, it is more appropriate to estimate the uncertainty of <span class="hlt">creep</span> from reversibility error.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25771255','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25771255"><span id="translatedtitle"><span class="hlt">Creep</span>-assisted slow crack growth in bio-inspired dental multilayers.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Du, Jing; Niu, Xinrui; Soboyejo, Wole</p> <p>2015-06-01</p> <p>Ceramic crown structures under occlusal contact are often idealized as flat multilayered structures that are <span class="hlt">deformed</span> under Hertzian contact loading. Previous models treated each layer as linear elastic materials and resulted in differences between the measured and predicted critical loads. This paper examines the combined effects of <span class="hlt">creep</span> (in the adhesive and substrate layers) and <span class="hlt">creep</span>-assisted slow crack growth (in the ceramic layer) on the contact-induced <span class="hlt">deformation</span> of bio-inspired, functionally graded multilayer (FGM) structures and the conventional tri-layers. The time-dependent moduli of each of the layers were determined from constant load <span class="hlt">creep</span> tests. The resulting modulus-time <span class="hlt">characteristics</span> were modeled using Prony series. These were then incorporated into a finite element model for the computation of stress distributions in the sub-surface regions of the top ceramic layer, in which sub-surface radial cracks, are observed as the clinical failure mode. The time-dependent stresses are incorporated into a slow crack growth (SCG) model that is used to predict the critical loads of the dental multilayers under Hertzian contact loading. The predicted loading rate dependence of the critical loads is shown to be consistent with experimental results. The implications of the results are then discussed for the design of robust dental multilayers. PMID:25771255</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10168891','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10168891"><span id="translatedtitle">Development of a constitutive model for <span class="hlt">creep</span> and life prediction of advanced silicon nitride ceramics</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ding, J.L.; Liu, K.C.; Brinkman, C.R.</p> <p>1992-12-31</p> <p>A constitutive model capable of describing <span class="hlt">deformation</span> and predicting rupture life was developed for high temperature ceramic materials under general thermal-mechanical loading conditions. The model was developed based on the <span class="hlt">deformation</span> and fracture behavior observed from a systematic experimental study on an advanced silicon nitride (Si{sub 3}N{sub 4}) ceramic material. Validity of the model was evaluated with reference to <span class="hlt">creep</span> and <span class="hlt">creep</span> rupture data obtained under constant and stepwise-varied loading conditions, including the effects of annealing on <span class="hlt">creep</span> and <span class="hlt">creep</span> rupture behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27556970','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27556970"><span id="translatedtitle">Surface <span class="hlt">deformation</span> and friction <span class="hlt">characteristic</span> of nano scratch at ductile-removal regime for optical glass BK7.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Chen; Zhang, Feihu; Ding, Ye; Liu, Lifei</p> <p>2016-08-20</p> <p>Nano scratch for optical glass BK7 based on the ductile-removal regime was carried out, and the influence rule of scratch parameters on surface <span class="hlt">deformation</span> and friction <span class="hlt">characteristic</span> was analyzed. Experimental results showed that, with increase of normal force, the <span class="hlt">deformation</span> of burrs in the edge of the scratch was more obvious, and with increase of the scratch velocity, the <span class="hlt">deformation</span> of micro-fracture and burrs in the edge of the scratch was more obvious similarly. The residual depth of the scratch was measured by atomic force microscope. The experimental results also showed that, with increase of normal force, the residual depth of the scratch increased linearly while the elastic recovery rate decreased. Furthermore, with increase of scratch velocity, the residual depth of the scratch decreased while the elastic recovery rate increased. The scratch process of the Berkovich indenter was divided into the cutting process of many large negative rake faces based on the improved cutting model, and the friction <span class="hlt">characteristic</span> of the Berkovich indenter and the workpiece was analyzed. The analysis showed that the coefficient of friction increased and then tended to be stable with the increase of normal force. Meanwhile, the coefficient of friction decreased with the increase of scratch velocity, and the coefficients, k ln(v) and μ<sub>0</sub>, were introduced to improve the original formula of friction coefficient. PMID:27556970</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009CoMP..157..339X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009CoMP..157..339X"><span id="translatedtitle">The effect of dissolved magnesium on <span class="hlt">creep</span> of calcite II: transition from diffusion <span class="hlt">creep</span> to dislocation <span class="hlt">creep</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, Lili; Renner, Jörg; Herwegh, Marco; Evans, Brian</p> <p>2009-03-01</p> <p>We extended a previous study on the influence of Mg solute impurity on diffusion <span class="hlt">creep</span> in calcite to include <span class="hlt">deformation</span> under a broader range of stress conditions and over a wider range of Mg contents. Synthetic marbles were produced by hot isostatic pressing (HIP) mixtures of calcite and dolomite powders for different intervals (2-30 h) at 850°C and 300 MPa confining pressure. The HIP treatment resulted in high-magnesian calcite aggregates with Mg content ranging from 0.5 to 17 mol%. Both back-scattered electron images and chemical analysis suggested that the dolomite phase was completely dissolved, and that Mg distribution was homogeneous throughout the samples at the scale of about two micrometers. The grain size after HIP varied from 8 to 31 μm, increased with time at temperature, and decreased with increasing Mg content (>3.0 mol%). Grain size and time were consistent with a normal grain growth equation, with exponents from 2.4 to 4.7, for samples containing 0.5-17.0 mol% Mg, respectively. We <span class="hlt">deformed</span> samples after HIP at the same confining pressure with differential stresses between 20 and 200 MPa using either constant strain rate or stepping intervals of loading at constant stresses in a Paterson gas-medium <span class="hlt">deformation</span> apparatus. The <span class="hlt">deformation</span> tests took place at between 700 and 800°C and at strain rates between 10-6 and 10-3 s-1. After <span class="hlt">deformation</span> to strains of about 25%, a bimodal distribution of large protoblasts and small recrystallized neoblasts coexisted in some samples loaded at higher stresses. The <span class="hlt">deformation</span> data indicated a transition in mechanism from diffusion <span class="hlt">creep</span> to dislocation <span class="hlt">creep</span>. At stresses below 40 MPa, the strength was directly proportional to grain size and decreased with increasing Mg content due to the reductions in grain size. At about 40 MPa, the sensitivity of log strain rate to log stress, ( n), became greater than 1 and eventually exceeded 3 for stresses above 80 MPa. At a given strain rate and temperature, the stress at</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/619482','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/619482"><span id="translatedtitle">Diffusional <span class="hlt">creep</span> and diffusion-controlled dislocation <span class="hlt">creep</span> and their relation to denuded zones in Mg-ZrH{sub 2} materials</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ruano, O.A.; Sherby, O.D.; Wadsworth, J.; Wolfenstine, J.</p> <p>1998-03-13</p> <p>Langdon`s contention that <span class="hlt">creep</span> of Mg-0.5 wt% Zr is well characterized by diffusional <span class="hlt">creep</span> at 400 C is in error. It is shown that Langdon and Gifkins` single analysis of denuded zones formed during <span class="hlt">creep</span> at 2 MPa, purporting to occur as a result of diffusional <span class="hlt">creep</span>, in fact, took place in the power-law dislocation <span class="hlt">creep</span> range where solute atoms are interacting with moving dislocations. This observation supports the earlier conclusions made for <span class="hlt">creep</span> and denuded zones observed in the hydrided Mg-Zr alloy at 500 C. Furthermore, it is shown that Pickles` data at stresses below 2 MPa at 400 C are not related to diffusional <span class="hlt">creep</span> as considered by Langdon. In this region, denuded zones appear in both longitudinal and transverse boundaries indicating that grain boundary sliding, accompanied by grain boundary migration, is the principal <span class="hlt">deformation</span> process. It is proposed that denuded zones are caused by dissolution of precipitates at moving grain boundaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ChPhB..22c7303B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ChPhB..22c7303B"><span id="translatedtitle">Dislocation-mediated <span class="hlt">creep</span> process in nanocrystalline Cu</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mu, Jun-Wei; Sun, Shi-Cheng; Jiang, Zhong-Hao; Lian, Jian-She; Jiang, Qing</p> <p>2013-03-01</p> <p>Nanocrystalline Cu with average grain sizes ranging from ~ 24.4 to 131.3 nm were prepared by the electric brush-plating technique. Nanoindentation tests were performed within a wide strain rate range, and the <span class="hlt">creep</span> process of nanocrystalline Cu during the holding period and its relationship to dislocation and twin structures were examined. It was demonstrated that <span class="hlt">creep</span> strain and <span class="hlt">creep</span> strain rate are considerably significant for smaller grain sizes and higher loading strain rates, and are far higher than those predicted by the models of Cobble <span class="hlt">creep</span> and grain boundary sliding. The analysis based on the calculations and experiments reveals that the significant <span class="hlt">creep</span> <span class="hlt">deformation</span> arises from the rapid absorption of high density dislocations stored in the loading regime. Our experiments imply that stored dislocations during loading are highly unstable and dislocation activity can proceed and lead to significant post-loading plasticity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1984JMPSo..32..373T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1984JMPSo..32..373T"><span id="translatedtitle">On the <span class="hlt">creep</span> constrained diffusive cavitation of grain boundary facets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tvergaard, Viggo</p> <p></p> <p><span class="hlt">CREEP</span> rupture in a polycrystalline metal at a high temperature, by cavity growth on a number of grain boundary facets, is studied numerically. An axisymmetric model problem is analysed, in which a cavitating facet is represented as disk-shaped, and the model dimensions are taken to represent spacings between neighbouring cavitating facets. For the grains both power law <span class="hlt">creep</span> and elastic <span class="hlt">deformations</span> are taken into account, and the description of cavity growth is based on an approximate expression that incorporates the coupled influence of grain boundary diffusion and power law <span class="hlt">creep</span>. The cases considered include <span class="hlt">creep</span>-constrained cavity growth at low stresses, where the voids link up to form grain boundary cracks at relatively small overall strains, as well as the power law <span class="hlt">creep</span> dominated behaviour at higher stress levels, where rupture occurs at large overall strains. The numerical results are compared with results based on various simplified analyses.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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