Showing papers on "Creep published in 2019"
TL;DR: In this paper, the elastic and plastic mechanical properties and creep behavior of Li metal solid-state batteries (LMSSB) have been characterized using an acoustic technique (pulse-echo) and the Young's modulus, shear modulus and Poisson's ratio were determined to be 7.82, 2.83 and 0.381, respectively.
Abstract: With the potential to dramatically increase energy density compared to conventional lithium ion technology, lithium metal solid-state batteries (LMSSB) have attracted significant attention. However, little is known about the mechanical properties of Li. The purpose of this study was to characterize the elastic and plastic mechanical properties and creep behavior of Li. Elastic properties were measured using an acoustic technique (pulse-echo). The Young’s modulus, shear modulus, and Poisson’s ratio were determined to be 7.82 GPa, 2.83 GPa, and 0.381, respectively. To characterize the stress–strain behavior of Li in tension and compression, a unique load frame was used inside an inert atmosphere. The yield strength was determined to be between 0.73 and 0.81 MPa. The time-dependent deformation in tension was dramatically different compared to compression. In tension, power law creep was exhibited with a stress exponent of 6.56, suggesting that creep was controlled by dislocation climb. In compression, time-dependent deformation was characterized over a range of stress believed to be germane to LMSSB (0.8–2.4 MPa). At all compressive stresses, significant barreling and a decrease in strain rate with increasing time were observed. The implications of this observation on the charge/discharge behavior of LMSSB will be discussed. We believe the analysis and mechanical properties measured in this work will help in the design and development of LMSSB.
224 citations
22 Jan 2019
TL;DR: In this article, the logarithmic creep law for secondary compression is transformed into a differential form in order to include transient loading conditions, and a 1-D creep model for oedometer-type strain conditions is then extended towards general 3-D states of stress and strain by incorporating concepts of Modified Cam-Clay and viscoplasticity.
Abstract: The well-known logarithmic creep law for secondary compression is transformed into a differential form in order to include transient loading conditions. This 1-D creep model for oedometer-type strain conditions is then extended towards general 3-D states of stress and strain by incorporating concepts of Modified Cam-Clay and viscoplasticity. Considering lab test data it is shown that phenomena such as undrained creep, overconsolidation and aging are well captured by the model.
220 citations
TL;DR: In this article, an equivalent Burgers model for rheological fracture of rock cracks under different hydraulic pressure and far field stresses has been proposed, which can be used to reveal the rheology behavior of fractured rock mass.
212 citations
TL;DR: In this article, the authors presented a multi-stage hierarchical micromechanical model to investigate the creep response of polymer nanocomposites containing randomly dispersed carbon nanotubes (CNTs).
Abstract: The present work is aimed at presenting a multi-stage hierarchical micromechanical model to investigate creep response of polymer nanocomposites containing randomly dispersed carbon nanotubes (CNTs). Two frequently real situations-encountered fundamental aspects affecting the polymer nanocomposite mechanical behavior including the CNT/polymer interphase region and CNT agglomeration are taken into account. It is assumed that the CNT to be a transversely isotropic material and the polymer matrix obeys a viscoelastic constitutive law. The multi-stage procedure homogenizes the nanocomposite by exploiting a unit cell-based micromechanical model coupled with Eshelby method. Generally, an excellent agreement is found between the results of the current model and available experiment. The outcomes clearly prove that for a more realistic prediction in the case of creep performance of CNT-polymer nanocomposites, considering the (i) random dispersion and (ii) transversely isotropic behavior of CNTs as well as (iii) viscoelastic interphase region is essential. Moreover, when CNTs are not well-dispersed into the polymer nanocomposites, the three significant factors together with the CNTs agglomerated state must be precisely incorporated in the analysis to achieve a more accurate estimation of the creep response. It is shown that the CNT agglomeration dramatically influences and degrades the creep resistance of the CNT-polymer nanocomposites. Also, the effects of CNT volume fraction and interphase characteristics on the nanocomposites creep behavior are extensively examined.
123 citations
TL;DR: In the creep tests, stress is no longer a constant and increases gradually under the influence of damage occurring during accelerating creep, which is a slow-loading process rather than a conventio...
Abstract: In the creep tests, stress is no longer a constant and increases gradually under the influence of damage occurring during accelerating creep, which is a slow-loading process rather than a conventio...
120 citations
TL;DR: In this paper, precipitation-hardened Al-Cu alloys are normally used at temperatures below its ageing temperature of ∼225°C, to avoid thermally induced precipitate coarsening and resultant softening.
Abstract: Commercial precipitation-hardened Al-Cu alloys are normally used at temperatures below its ageing temperature of ∼225°C, to avoid thermally induced precipitate coarsening and resultant softening. M...
119 citations
TL;DR: In this article, the authors investigated the storage of geometrically necessary (GND) and statistically stored (SSD) dislocations in a nickel-based superalloy.
113 citations
TL;DR: In this article, the authors investigated the influence of incorporating different types of carbon nanotubes (CNTs) on the long-term creep and shrinkage of concrete, and found that incorporating CNTs were able to improve the compressive strength up to 21%, but only slightly increased the modulus of elasticity.
102 citations
TL;DR: A review of the evolution in measurement methodologies (either from controlled experiments in materials test reactors or gauging of power reactor components) is described together with the results gleaned from such measurements.
84 citations
TL;DR: This study demonstrates a much higher ductility for an amorphous oxide at low temperature than previous observations, which may facilitate the realization of damage-tolerant glass materials that contribute in new ways, with the potential to improve the mechanical resistance and reliability of applications such as electronic devices and batteries.
Abstract: Oxide glasses are an integral part of the modern world, but their usefulness can be limited by their characteristic brittleness at room temperature. We show that amorphous aluminum oxide can permanently deform without fracture at room temperature and high strain rate by a viscous creep mechanism. These thin-films can reach flow stress at room temperature and can flow plastically up to a total elongation of 100%, provided that the material is dense and free of geometrical flaws. Our study demonstrates a much higher ductility for an amorphous oxide at low temperature than previous observations. This discovery may facilitate the realization of damage-tolerant glass materials that contribute in new ways, with the potential to improve the mechanical resistance and reliability of applications such as electronic devices and batteries.
83 citations
TL;DR: In this article, the effect of glass powder (GP) on the compressive strength, elastic modulus and creep of concrete has been investigated, and the internal microstructure is also determined by mercury intrusion porosimetry, scanning electron microscope and nanoindentation techniques.
Abstract: Glass powder (GP) is a solid waste with increasing reserves. GP can be used as a supplementary cementitious material (SCM) to produce concrete in order to effectively save resources and solve environmental pollution problems. The effect of GP to replace cement partially by weight on the compressive strength, elastic modulus and creep of concrete has experimentally been studied, and the internal microstructure is also determined by mercury intrusion porosimetry, scanning electron microscope and nanoindentation techniques. The results show that the use of GP reduces the compressive strengths and elastic modulus at the early ages, but the use of GP content less than 20% increases the compressive strengths and elastic modulus at the later ages. The use of GP content less than 20% can obviously reduce the creep and the use of 20% GP content seems to be the best in terms of the reduction of the creep. The use of GP with the appropriate content can effectively improve the internal microstructure of concrete and increase the content of high density calcium silicate hydrate at the later ages which is helpful in reducing the creep. This may be attributed to the pozzolanic reaction and microfiller effect of GP.
TL;DR: In this article, a series of uniaxial compressive strength tests and multistage creep tests were performed on red sandstone specimens under different water soaking conditions, and the results showed that the peak strength and elastic modulus of the red sandstones decrease with not only water content but also immersion time, which can be better expressed by a negative exponential function.
TL;DR: In this article, acoustic emission (AE) experiments were carried out to study short-time creep behavior under uniaxial compression for cuboid-shaped fine sandstone specimens with two pre-existing cracks.
TL;DR: It is concluded that various wall properties are not tightly coupled and thus reflect distinctive aspects of wall structure, which is crucial for constructing realistic molecular models that define how wall mechanics and growth depend on primary cell wall structure.
Abstract: How cell wall elasticity, plasticity, and time-dependent extension (creep) relate to one another, to plant cell wall structure and to cell growth remain unsettled topics. To examine these issues without the complexities of living tissues, we treated cell-free strips of onion epidermal walls with various enzymes and other agents to assess which polysaccharides bear mechanical forces in-plane and out-of-plane of the cell wall. This information is critical for integrating concepts of wall structure, wall material properties, tissue mechanics and mechanisms of cell growth. With atomic force microscopy we also monitored real-time changes in the wall surface during treatments. Driselase, a potent cocktail of wall-degrading enzymes, removed cellulose microfibrils in superficial lamellae sequentially, layer-by-layer, and softened the wall (reduced its mechanical stiffness), yet did not induce wall loosening (creep). In contrast Cel12A, a bifunctional xyloglucanase/cellulase, induced creep with only subtle changes in wall appearance. Both Driselase and Cel12A increased the tensile compliance, but differently for elastic and plastic components. Homogalacturonan solubilization by pectate lyase and calcium chelation greatly increased the indentation compliance without changing tensile compliances. Acidic buffer induced rapid cell wall creep via endogenous α-expansins, with negligible effects on wall compliances. We conclude that these various wall properties are not tightly coupled and therefore reflect distinctive aspects of wall structure. Cross-lamellate networks of cellulose microfibrils influenced creep and tensile stiffness whereas homogalacturonan influenced indentation mechanics. This information is crucial for constructing realistic molecular models that define how wall mechanics and growth depend on primary cell wall structure.
TL;DR: In this article, a nonlinear creep damage model for sandstone is proposed based on multi-loading creep tests of sandstone with different initial damage levels, which is composed of four components, a Hooke body, a Kelvin body, an improved viscous element, and a new nonlinear visco-plastic damage component.
Abstract: The experimental results show that initial damage has a clear effect on the creep behavior of rock. However, among the current creep models for rock, few consider the effect of the initial damage state. In the present study, a new nonlinear creep damage model for rock is proposed based on multi-loading creep tests of sandstone with different initial damage levels. The new model is composed of four components, a Hooke body, a Kelvin body, an improved viscous element, and a new nonlinear visco-plastic damage component. The creep damage model can not only describe the three typical creep stages (primary creep, secondary creep and tertiary creep) but also show the effect of initial damage on the creep failure stress. The parameters of the nonlinear creep damage model are obtained using the nonlinear least squares method. A unified set of creep parameters is proposed to predict the creep behavior of sandstone in different initial damage states. The agreement between the experimental data and numerical prediction demonstrates the applicability of the proposed model.
TL;DR: In this paper, the authors proposed a phase field formulation in which fracture of viscoelastic solids is driven by both elastic and viscous components of the energy and showed that at low strain rates viscous energy dissipation accelerates the fracture growth rate but essentially does not affect the crack path, while at high rates the effect of viscous dissipation is minor.
TL;DR: In this paper, the authors investigated quartzite flow laws based on data from 21 different experimental studies on samples deformed with added water at temperatures from 700 to 1200°C and found that the change in stress exponent indicates a transition in the rate-limiting process of dislocation creep.
TL;DR: In this paper, the microstructure evolution, hardness, adhesive strength and tensile strength were investigated systematically on the cold-sprayed and heat-treated Inconel 718 alloy.
20 Sep 2019
16 Jan 2019-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the microstructure evolution and creep behavior of a novelly designed as-cast Ni3Al-based superalloy with multiphase configuration are investigated by high-temperature annealing treatments.
Abstract: The microstructure evolution and creep behavior of a novelly designed as-cast Ni3Al-based superalloy with multiphase configuration are investigated by high-temperature annealing treatments. The as-cast microstructure comprises dominant γ′+γ dendritic and less (~19.37 vol%) interdendritic β areas, annealing treatments at 1160–1280 °C promoted the growth of γ'Ⅰ phase in the γ'+γ dendrite, during which the interdendritic β phase aggregated and coarsened rapidly in width with keeping its relatively constant volume fraction. Meanwhile, the annealing treatments significantly promoted the precipitation of quasi-spherical α-Cr phase particles within the β phase. The original as-cast microstructure exhibited inferior creep resistance at 800 °C/200 MPa with the shortest creep rupture life of 194 h, however, the annealing treatments at 1160–1280 °C prolonged the creep rupture life to beyond 611 h. Although the steady-state creep rate was gradually reduced with increasing annealing temperatures, the creep ductility was degraded by higher-temperature annealing at 1240 and 1280 °C compared with original as-cast microstructure. The 1160 °C annealed microstructure exhibited the longest creep rupture life of 665 h and the maximum creep strain to fracture of 3.21%, while the minimum steady-state creep rate was obtained on account of the largest γ'Ⅰ phase sized 0.91 µm after annealing at 1280 °C. Despite its positive role in the castability, thermoplasticity and weldability of the explored multiphase Ni3Al-based superalloy, interdendritic β phase has negative effects on the creep properties due to its incoherent existence with the dominant γ′+γ dendrite.
TL;DR: In this paper, the authors investigate ternary Al 6Ni-0.2Sc and Al 6 Ni 0.4Sc alloys with both types of strengthening precipitates and compare them to binary alloys.
TL;DR: This material is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form.
Abstract: Powered by TCPDF (www.tcpdf.org) This material is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form. You must obtain permission for any other use. Electronic or print copies may not be offered, whether for sale or otherwise to anyone who is not an authorised user. Viitanen, Leevi; Ovaska, Markus; Ram, Sumit Kumar; Alava, Mikko J.; Karppinen, Pasi
TL;DR: In this article, the effects of tensile and compressive strain hold times on creep-fatigue lifetimes were experimentally explored with varying total strain ranges in order to elucidate the damage mechanisms under complex loading waveforms.
TL;DR: In this article, the authors investigated the underlying creep deformation mechanism of AM processed IN738LC using the serial sectioning technique, electron backscatter diffraction (EBSD), transmission electron microscopy (TEM).
22 May 2019-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the hot compressive deformation mechanism and processing maps of the equiatomic FCC CoCrFeMnNi high-entropy alloy (HEA) were studied in the temperature range between 1023 and 1323
Abstract: The hot compressive deformation mechanism and processing maps of the equiatomic FCC CoCrFeMnNi high-entropy alloy (HEA) were studied in the temperature range between 1023 and 1323 K and in the strain rate range between 10−3 and 10 s−1. At high strain rates above 1 s-1, strain hardening was dominant even at the very high temperature of 0.84Tm, which may be attributed to the sluggish diffusion coefficient and low stacking fault energy of the CoCrFeMnNi HEA, leading to suppression of dynamic recovery. According to the processing maps, the best condition for hot working was near 10−3 s−1 at 1323 K. Power-law breakdown and unstable flow occurred at low temperatures and high strain rates where the strain hardening was pronounced. The activation energy for plastic flow measured in the power-law creep regime when considering the dependence of elastic modulus on temperature was 312.2 kJ/mol; this value is close to the activation energy for the weighted diffusion coefficient calculated by weighting the contribution of each element in the CoCrFeMnNi HEA (284 kJ/mol). The size and fraction of the dynamically recrystallized grains increased as the strain rate decreased and the temperature increased, as in conventional metals. Both discontinuous dynamic recrystallization and continuous dynamic recrystallization (CDRX) occurred. CDRX became more distinct as the temperature increased. The deformation mechanism and behavior of the CoCrFeMnNi HEA were very similar to those of FCC pure metals in terms of the stress exponent and the effect of the stacking fault energy and diffusivity on the creep rates.
TL;DR: In this paper, the authors measured early-age shrinkage and tensile creep of geopolymer concrete and assessed their influence on early age cracking in reinforced concrete members, showing that higher curing temperature leads to less shrinkage strains.
TL;DR: In this article, the strengthening mechanisms of a creep-resistant Mg-0.5Gd-1.2Ca (at.%) alloy at both room and elevated temperatures were studied.
TL;DR: In this paper, a selective laser melting (SLM) was used to fabricate an equiatomic CoCrFeMnNi high-entropy alloy (HEA), which was studied with X-ray diffraction, field-emission scanning electron microscopy (FESEM), electron backscatter diffraction (EBSD), and nanoindentation techniques.
Abstract: Selective laser melting (SLM) was used to fabricate an equiatomic CoCrFeMnNi high-entropy alloy (HEA). The SLM-fabricated CoCrFeMnNi HEA samples were studied with X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), electron backscatter diffraction (EBSD) and nanoindentation techniques to characterize the microstructure and creep behavior. It was found that the HEA comprised a single face-centered cubic (fcc) structure. Due to the fast solidification and high temperature gradients of the molten pool during the SLM process, the microstructure comprised cellular subgrains with grain boundary angles lower than 5°. Based on energy dispersive spectrometry (EDS) maps, the constituent elements of the SLM-fabricated HEA were homogenously distributed. Moreover, the effect of the peak holding load on the nanoindentation creep deformation of the SLM-fabricated HEA was investigated using a Berkovich indenter. The results of this study indicated that the creep was mainly dominated by deformation controlled by dislocation motion.
TL;DR: In this paper, the authors observed an abnormal γ-prime with tailored orientation and shape in directly aged cold-rolled Inconel 718, and the results proved its substantial benefits in improving creep resistance at 650 ǫ°C superior to commonly perpendicular γ′ prime.
TL;DR: In this article, a creep test was conducted on multi-pass shielded metal arc welded P91 steel weld joint at creep exposure temperature of 620°C for an applied stress of 150 and 200 MPa in as-welded, and post weld heat treatments (PWHTs) state.