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Auswahl der wissenschaftlichen Literatur zum Thema „Microstructures under stress“
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Zeitschriftenartikel zum Thema "Microstructures under stress"
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Zheng, Xiaomeng, Yongzhen Zhang und Sanming Du. „Preliminary Research on Response of GCr15 Bearing Steel under Cyclic Compression“. Materials 13, Nr. 16 (05.08.2020): 3443. http://dx.doi.org/10.3390/ma13163443.
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During the bearing service, a series of microstructural evolutions will arise inside the material, such as the appearance of feature microstructures. The essential reason for the microstructural evolution is the cumulative effect of cyclic stress. The Hertz Contact formula is usually adopted to calculate the internal stress, and there is a correlation between the shape and distribution of the feature microstructure and the stress distribution. But it is insufficient to explain the relationship between the morphology of feature microstructures and the rolling direction, such as specific angles in butterfly and white etching bands. The rolling phenomenon will cause the asymmetry of stress distribution in the material, which is the source of the rolling friction coefficient. Moreover, slipping or microslip will produce additional stress components, which also cause the asymmetry of the stress field. However, there is no experimental or theoretical explanation for the relationship between the asymmetry of the stress field and the feature microstructure. According to the current theory, the appearance of feature microstructures is caused by stress with or without rolling. Therefore, it is of great significance to study the formation mechanism: whether feature microstructures will appear in the uniaxial cyclic compression stress field without rolling. In this paper, uniaxial cyclic compressive stress was loaded into a plate-ball system and a cylinder system. The characteristics of microstructural change of bearing steel (GCr15) were studied. It was found that the hardness of the material increased after the cyclic compressive load, and the inclusions interacted with the matrix material. In the local microregion a white etching area was found, although the scale is very small. No large-scale feature microstructures appeared. Other phenomena in the experiment are also described and analyzed. For example, the production of oil film in the contact area and the changing law of alternating load.
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Barboza, Luis, Enrique López, Hugo Guajardo und Armando Salinas. „Effect of Initial Microstructure on the Temperature Dependence of the Flow Stress and Deformation Microstructure under Uniaxial Compression of Ti-407“. Metals 14, Nr. 5 (26.04.2024): 505. http://dx.doi.org/10.3390/met14050505.
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In this study, the influence of initial microstructure and deformation temperature on the flow stress behavior and microstructural evolution of TIMETAL®407 (Ti-407) alloy are investigated. For this purpose, compression cylinders were β-annealed at 940 °C and then cooled to room temperature using furnace cooling, static air, and water quenching to promote three initial microstructures with different α lath thicknesses. The annealed cylinders were compressed isothermally in the range of 750 °C to 910 °C at a constant crosshead speed of 0.05 mm/s up to an engineering strain of −0.8. The resulting stress–strain curves are discussed in terms of the morphology and distribution of the α and β phases. It was found that flow stress is inversely proportional to deformation temperature for all initial microstructures. At the lowest temperatures, compressive yield strength was higher in water-quenched and air-cooled samples than in furnace-cooled specimens, suggesting that the acicular α-phase morphology obtained by rapid cooling could enhance mechanical strength by hindering dislocation motion. Two high-temperature flow regimes were determined based on the shape of the flow stress curves, indicating microstructural changes occurring during deformation. At higher temperatures, the effect of the initial microstructure is negligible as the primary α phase is transformed to the β phase at around 850 °C irrespective of the initial α-lath thickness.
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Xi, Shangbin, und Yu Su. „Phase Field Study of the Microstructural Dynamic Evolution and Mechanical Response of NiTi Shape Memory Alloy under Mechanical Loading“. Materials 14, Nr. 1 (02.01.2021): 183. http://dx.doi.org/10.3390/ma14010183.
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For the purpose of investigating the microstructural evolution and the mechanical response under applied loads, a new phase field model based on the Ginzburg-Landau theory is developed by designing a free energy function with six potential wells that represent six martensite variants. Two-dimensional phase field simulations show that, in the process of a shape memory effect induced by temperature-stress, the reduction-disappearance of cubic austenite phase and nucleation-growth of monoclinic martensite multi-variants result in a poly-twined martensitic microstructure. The microstructure of martensitic de-twinning consists of different martensite multi-variants in the tension and compression, which reveals the microstructural asymmetry of nickel-titanium (NiTi) alloy in the tension and compression. Furthermore, in the process of super-elasticity induced by tensile or compressive stress, all martensite variants nucleate and expand as the applied stress gradually increases from zero. Whereas, when the applied stress reaches critical stress, only the martensite variants of applied stress-accommodating continue to expand and others fade gradually. Moreover, the twinned martensite microstructures formed in the tension and compression contain different martensite multi-variants. The study of the microstructural dynamic evolution in the phase transformation can provide a significant reference in improving properties of shape memory alloys that researchers have been exploring in recent years.
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Hanhan, Imad, und Michael D. Sangid. „Design of Low Cost Carbon Fiber Composites via Examining the Micromechanical Stress Distributions in A42 Bean-Shaped versus T650 Circular Fibers“. Journal of Composites Science 5, Nr. 11 (07.11.2021): 294. http://dx.doi.org/10.3390/jcs5110294.
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Recent advancements have led to new polyacrylonitrile carbon fiber precursors which reduce production costs, yet lead to bean-shaped cross-sections. While these bean-shaped fibers have comparable stiffness and ultimate strength values to typical carbon fibers, their unique morphology results in varying in-plane orientations and different microstructural stress distributions under loading, which are not well understood and can limit failure strength under complex loading scenarios. Therefore, this work used finite element simulations to compare longitudinal stress distributions in A42 (bean-shaped) and T650 (circular) carbon fiber composite microstructures. Specifically, a microscopy image of an A42/P6300 microstructure was processed to instantiate a 3D model, while a Monte Carlo approach (which accounts for size and in-plane orientation distributions) was used to create statistically equivalent A42/P6300 and T650/P6300 microstructures. First, the results showed that the measured in-plane orientations of the A42 carbon fibers for the analyzed specimen had an orderly distribution with peaks at |ϕ|=0∘,180∘. Additionally, the results showed that under 1.5% elongation, the A42/P6300 microstructure reached simulated failure at approximately 2108 MPa, while the T650/P6300 microstructure did not reach failure. A single fiber model showed that this was due to the curvature of A42 fibers which was 3.18 μm−1 higher at the inner corner, yielding a matrix stress that was 7 MPa higher compared to the T650/P6300 microstructure. Overall, this analysis is valuable to engineers designing new components using lower cost carbon fiber composites, based on the micromechanical stress distributions and unique packing abilities resulting from the A42 fiber morphologies.
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Chen, Haisheng, Fang Hao, Shixing Huang, Jing Yang, Shaoqiang Li, Kaixuan Wang, Yuxuan Du, Xianghong Liu und Xiaotong Yu. „The Effects of Microstructure on the Dynamic Mechanical Response and Adiabatic Shearing Behaviors of a Near-α Ti-6Al-3Nb-2Zr-1Mo Alloy“. Materials 16, Nr. 4 (07.02.2023): 1406. http://dx.doi.org/10.3390/ma16041406.
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The formation and evolution of adiabatic shear behaviors, as well as the corresponding mechanical properties of a near-Ti-6Al-3Nb-2Zr-1Mo (Ti-6321) alloy during dynamic compression process, were systematically investigated by the split Hopkinson pressure bar (SHPB) compression tests in this paper. Ti-6321 samples containing three types of microstructures, i.e., equiaxed microstructure, duplex microstructure and Widmanstätten microstructure, were prepared to investigate the relationship between microstructures and dynamic mechanical behaviors under different strain rates in a range from 1000 s−1 to 3000 s−1. It was found by the dynamic strain–stress relation that the Ti-6321 alloys containing equiaxed microstructure, duplex microstructure and Widmanstätten microstructure all exhibited a strong strain-hardening effect. The samples containing equiaxed microstructure exhibited a larger flow stress than samples containing duplex microstructure and Widmanstätten microstructure. The adiabatic shearing behaviors in Ti-6321 alloy are significantly influenced by different types of microstructures. The formation of adiabatic shearing bands occurs in equiaxed microstructure when the strain rate is increased to 2000 s−1. The adiabatic shear bands are formed in duplex microstructure when the strain rate reaches 3000 s−1. However, the initiation of adiabatic shear bands is found in Widmanstätten microstructure under the strain rate of 1000 s−1. The Widmanstätten microstructure shows a larger sensitivity to adiabatic shearing than the equiaxed microstructure and duplex microstructure samples.
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Kim, K., B. Forest und J. Geringer. „Two-dimensional finite element simulation of fracture and fatigue behaviours of alumina microstructures for hip prosthesis“. Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 225, Nr. 12 (19.09.2011): 1158–68. http://dx.doi.org/10.1177/0954411911422843.
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This paper describes a two-dimensional (2D) finite element simulation for fracture and fatigue behaviours of pure alumina microstructures such as those found at hip prostheses. Finite element models are developed using actual Al2O3 microstructures and a bilinear cohesive zone law. Simulation conditions are similar to those found at a slip zone in a dry contact between a femoral head and an acetabular cup of hip prosthesis. Contact stresses are imposed to generate cracks in the models. Magnitudes of imposed stresses are higher than those found at the microscopic scale. Effects of microstructures and contact stresses are investigated in terms of crack formation. In addition, fatigue behaviour of the microstructure is determined by performing simulations under cyclic loading conditions. It is shown that crack density observed in a microstructure increases with increasing magnitude of applied contact stress. Moreover, crack density increases linearly with respect to the number of fatigue cycles within a given contact stress range. Meanwhile, as applied contact stress increases, number of cycles to failure decreases gradually. Finally, this proposed finite element simulation offers an effective method for identifying fracture and fatigue behaviours of a microstructure provided that microstructure images are available.
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Ospina-Correa, Juan D., Daniel A. Olaya-Muñoz, Juan J. Toro-Castrillón, Alejandro Toro, Abelardo Ramírez-Hernández und Juan P. Hernández-Ortíz. „Grain polydispersity and coherent crystal reorientations are features to foster stress hotspots in polycrystalline alloys under load“. Science Advances 7, Nr. 15 (April 2021): eabe3890. http://dx.doi.org/10.1126/sciadv.abe3890.
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The mechanical properties of metallic alloys are controlled through the design of their polycrystalline structure via heat treatments. For single-phase microstructures, they aim to achieve a particular average grain diameter to leverage stress hardening or softening. The stochastic nature of the recrystallization process generates a grain size distribution, and the randomness of the crystallographic orientation determines the anisotropy of a mechanical response. We developed a multiscale computational formalism to capture the collective mechanical response of polycrystalline microstructures at unprecedented length scales. We found that for an averaged grain size, the mechanical response is highly dependent on the grain size distribution. The simulations reveal the topological conditions that promote coherent grain texturization and grain growth inhibition during stress relaxation. We identify the microstructural features that are responsible for the appearance of stress hotspots. Our results provide the elusive evidence of how stress hotspots are ideal precursors for plastic and creep failure.
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Barua, A., Y. Horie und M. Zhou. „Microstructural level response of HMX–Estane polymer-bonded explosive under effects of transient stress waves“. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 468, Nr. 2147 (15.08.2012): 3725–44. http://dx.doi.org/10.1098/rspa.2012.0279.
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The effect of transient stress waves on the microstructure of HMX–Estane, a polymer-bonded explosive (PBX), is studied. Calculations carried out concern microstructures with HMX grain sizes on the order of 200 μm and grain volume fractions in the range of 0.50–0.82. The microstructural samples analysed have an aspect ratio of 5:1 (15×3 mm), allowing the transient wave propagation process resulting from normal impact to be resolved. Boundary loading is effected by the imposition of impact face velocities of 50–200 m s −1 . Different levels of grain–binder interface strength are considered. The analysis uses a recently developed cohesive finite element framework that accounts for coupled thermal–mechanical processes involving deformation, heat generation and conduction, failure in the forms of microcracks in both bulk constituents and along grain/matrix interfaces, and frictional heating along crack faces. Results show that the overall wave speed through the microstructures depends on both the grain volume fraction and interface bonding strength between the constituents and that the distance traversed by the stress wave before the initiation of frictional dissipation is independent of the grain volume fraction but increases with impact velocity. Energy dissipated per unit volume owing to fracture is highest near the impact surface and deceases to zero at the stress wavefront. On the other hand, the peak temperature rises are noted to occur approximately 2–3 mm from the impact surface. Scaling laws are developed for the maximum dissipation rate and the highest temperature rise as functions of impact velocity, grain volume fraction and grain–binder interfacial bonding strength.
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Miyazawa, Yuto, Fabien Briffod, Takayuki Shiraiwa und Manabu Enoki. „Prediction of Cyclic Stress–Strain Property of Steels by Crystal Plasticity Simulations and Machine Learning“. Materials 12, Nr. 22 (07.11.2019): 3668. http://dx.doi.org/10.3390/ma12223668.
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In this study, a method for the prediction of cyclic stress–strain properties of ferrite-pearlite steels was proposed. At first, synthetic microstructures were generated based on an anisotropic tessellation from the results of electron backscatter diffraction (EBSD) analyses. Low-cycle fatigue experiments under strain-controlled conditions were conducted in order to calibrate material property parameters for both an anisotropic crystal plasticity and an isotropic J2 model. Numerical finite element simulations were conducted using these synthetic microstructures and material properties based on experimental results, and cyclic stress-strain properties were calculated. Then, two-point correlations of synthetic microstructures were calculated to quantify the microstructures. The microstructure-property dataset was obtained by associating a two-point correlation and calculated cyclic stress-strain property. Machine learning, such as a linear regression model and neural network, was conducted using the dataset. Finally, cyclic stress-strain properties were predicted from the result of EBSD analysis using the obtained machine learning model and were compared with the results of the low-cycle fatigue experiments.
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Koh, S. U., J. S. Kim, B. Y. Yang und K. Y. Kim. „Effect of Line Pipe Steel Microstructure on Susceptibility to Sulfide Stress Cracking“. Corrosion 60, Nr. 3 (01.03.2004): 244–53. http://dx.doi.org/10.5006/1.3287728.
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Abstract The purpose of this experiment was to evaluate the effect of microstructure on sulfide stress cracking (SSC) properties of line pipe steel. Different kinds of microstructures, with chemical compositions identical to one steel heat, were produced by various thermomechanically controlled processes (TMCP). Coarse ferrite-pearlite, fine ferrite-pearlite, ferrite-acicular ferrite, and ferrite-bainite microstructures were investigated with respect to corrosion properties, hydrogen diffusion, and SSC behavior. SSC was evaluated using a constant elongation rate test (CERT) in a NACE TM0177 solution (5% sodium chloride [NaCl] + 0.5% acetic acid [CH3COOH], saturated with hydrogen sulfide [H2S]). The corrosion properties of steels were evaluated by potentiodynamic and linear polarization methods. Hydrogen diffusion through steel matrix was measured by an electrochemical method using a Devanathan-Stachurski cell. The effect of microstructure on cracking behavior also was investigated with respect to crack nucleation and propagation processes. Test results showed that ferrite-acicular ferrite microstructure had the highest resistance to SSC, whereas ferrite-bainitic and coarse ferritie-pearlitic microstructures had the lowest resistance. The high susceptibility to SSC inferritie-bainitic and coarse ferritic-pearlitic microstructures resulted from crack nucleation on hard phases such as grain boundary cementite in coarse ferritie-pearlitic microstructures and martensite/retained austenite (M/A) island in bainitic phases. Hard phase cementite at grain boundaries or M/A constituent in bainitic phases acted as crack nucleation sites and could be cracked easily under external stress; consequently, the susceptibility of steel to SSC increased. Metallurgical parameters including matrix structure and defects such as grain boundary carbides and inter-lath M/A constituents were more critical parameters for controlling SSC than the hydrogen diffusion rate.
Dissertationen zum Thema "Microstructures under stress"
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Gonzales, Manny. „The mechanochemistry in heterogeneous reactive powder mixtures under high-strain-rate loading and shock compression“. Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54393.
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This work presents a systematic study of the mechanochemical processes leading to chemical reactions occurring due to effects of high-strain-rate deformation associated with uniaxial strain and uniaxial stress impact loading in highly heterogeneous metal powder-based reactive materials, specifically compacted mixtures of Ti/Al/B powders. This system was selected because of the large exothermic heat of reaction in the Ti+2B reaction, which can support the subsequent Al-combustion reaction. The unique deformation state achievable by such high-pressure loading methods can drive chemical reactions, mediated by microstructure-dependent meso-scale phenomena. Design of the next generation of multifunctional energetic structural materials (MESMs) consisting of metal-metal mixtures requires an understanding of the mechanochemical processes leading to chemical reactions under dynamic loading to properly engineer the materials. The highly heterogeneous and hierarchical microstructures inherent in compacted powder mixtures further complicate understanding of the mechanochemical origins of shock-induced reaction events due to the disparate length and time scales involved.
A two-pronged approach is taken where impact experiments in both the uniaxial stress (rod-on-anvil Taylor impact experiments) and uniaxial strain (instrumented parallel-plate gas-gun experiments) load configurations are performed in conjunction with highly-resolved microstructure-based simulations replicating the experimental setup. The simulations capture the bulk response of the powder to the loading, and provide a look at the meso-scale deformation features observed under conditions of uniaxial stress or strain. Experiments under uniaxial stress loading reveal an optimal stoichiometry for Ti+2B mixtures containing up to 50% Al by volume, based on a reduced impact velocity threshold required for impact-induced reaction initiation as evidenced by observation of light emission. Uniaxial strain experiments on the Ti+2B binary mixture show possible expanded states in the powder at pressures greater than 6 GPa, consistent with the Ballotechnic hypothesis for shock-induced chemical reactions. Rise-time dispersive signatures are consistently observed under uniaxial strain loading, indicating complex compaction phenomena, which are reproducible by the meso-scale simulations. The simulations show the prevalence of shear banding and particle agglomeration in the uniaxial stress case, providing a possible rationale for the lower observed reaction threshold. Bulk shock response is captured by the uniaxial strain meso-scale simulations and is compared with PVDF stress gauge and VISAR traces to validate the simulation scheme. The simulations also reveal the meso-mechanical origins of the wave dispersion experimentally recorded by PVDF stress gauges.
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Hamma, Juba. „Modélisation par la méthode des champs de phase du maclage mécanique dans des alliages de titane β-métastables“. Electronic Thesis or Diss., Sorbonne université, 2020. http://www.theses.fr/2020SORUS381.
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Les alliages de titane beta-métastables ont des propriétés mécaniques remarquables à température ambiante, liées à l'évolution sous contrainte de la microstructure. Un mode de déformation spécifique à ces alliages joue un rôle essentiel : le système de maclage {332}<11-3>. On s'intéresse ainsi à une modélisation champ de phase de l'évolution sous contrainte des variants de macle {332}. Une première partie est consacrée à un modèle champ de phase de type Allen-Cahn avec prise en compte d'une élasticité dans un formalisme géométriquement linéaire (GL). On utilise une énergie d'interface isotrope ou anisotrope afin d'étudier l'influence de cette dernière sur la croissance et le degré d'anisotropie des variants de macle. Le rôle d'une élasticité formulée dans le formalisme géométriquement non-linéaire (GNL) est ensuite discuté et donne lieu à la deuxième partie de ces travaux. Un solveur mécanique dans le formalisme GNL par méthode spectrale est alors mis en place et validé. Il est ensuite utilisé dans le développement d'un modèle champ de phase de type Allen-Cahn avec prise en compte d'une élasticité GNL. Nous procédons alors à une étude comparative fine des microstructures obtenues en GL et GNL. Les résultats montrent une différence majeure entre les microstructures obtenues dans les deux cadres élastiques, concluant sur la nécessité d'une élasticité dans le GNL pour reproduire les microstructures de macle observées. Enfin, nous présentons une étude prospective d'un modèle basé sur une méthode de réduction de Lagrange, qui permettrait de prendre en compte le caractère reconstructif du maclage et la nature hiérarchique des microstructures observées expérimentalementBeta-metastable titanium alloys exhibit remarkable mechanical properties at room temperature, linked to the microstructure evolution under stress. A specific deformation mode plays an essential role: the {332}<11-3> twinning system. This thesis work thus concerns a modeling, by the phase field method, of {332} twin variants evolution under stress. The first part is devoted to an Allen-Cahn type phase field model with an elasticity taken into account in a geometrically linear formalism. This model is used with an isotropic or anisotropic interface energy in order to study the influence of the latter on the growth of twin variants. The role of an elasticity formulated in finite strain is then discussed and gives rise to the second part of this work. A mechanical equilibrium solver formulated in the geometrically non-linear formalism using a spectral method is then set up and validated. It is then used in the development of an Allen-Cahn type phase field model considering a geometrically non-linear elasticity. We then proceed to a fine comparative study of the microstructures obtained in linear and non-linear geometries. The results show a major difference between the microstructures obtained in the two elastic frameworks, concluding on the need for elasticity in finite strain formalism to reproduce the twin microstructures observed experimentally. Finally, we present a prospective study of a more general phase field formalism than the previous ones, based on a Lagrange reduction method, which would allow to fully take into account the reconstructive character of twinning and the hierarchical nature of the microstructures observed experimentally
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Minani, Evariste. „Microstructure, stress and defect evolution under illumination in hydrogenated amorphous silicon (a-Si:H)“. Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/6540.
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Includes abstract.Includes bibliographical references (leaves 151-157).
The purpose of this study is firstly to investigate the relation between microstructure, stress and hydrogen distribution in as deposited hydrogenated amorphous silicon (a-Si:H) layers, and secondly the investigation of the influence of illumination on hydrogen evolution and its relationship with the strain in illuminated layers.
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Tucker, Matthew Taylor. „Structure-property stress state dependent relationships under varying strain rates“. Diss., Mississippi State : Mississippi State University, 2009. http://library.msstate.edu/etd/show.asp?etd=etd-04022009-091044.
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Melhorn, Susan Jennifer. „The microstructure of food intake under conditions of high-fat diet, social stress and social subordination“. University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1243018975.
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Melhorn, Susan J. „The microstructure of food intake under conditions of high-fat diet, social stress and social subordination“. Cincinnati, Ohio : University of Cincinnati, 2009. http://rave.ohiolink.edu/etdc/view.cgi?acc_num=ucin1243018975.
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Thesis (Ph.D.)--University of Cincinnati, 2009.Advisor: Stephen C. Woods. Title from electronic thesis title page (viewed Aug. 12, 2009). Keywords: meal patterns; social stress; social subordination; Neuropeptide Y; body weight; body compostion. Includes abstract. Includes bibliographical references.
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Gardiner, Peter Christopher. „Microstructural damage and mechanical properties of a metal matrix composite (Al-particulate SiC) and an intermetallic (titanium aluminide) under various deformation regimes“. Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287656.
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Yang, Dong. „Factors affecting stress assisted corrosion cracking of carbon steel under industrial boiler conditions“. Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24809.
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Thesis (Ph.D.)--Mechanical Engineering, Georgia Institute of Technology, 2008.Committee Co-Chair: Preet M. Singh; Committee Co-Chair: Richard W. Neu; Committee Member: Hamid Garmestani; Committee Member: Timothy Patterson; Committee Member: W. Steven Johnson.
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„The microstructure of food intake under conditions of high-fat diet, social stress and social subordination“. UNIVERSITY OF CINCINNATI, 2010. http://pqdtopen.proquest.com/#viewpdf?dispub=3371601.
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Arbind, Archana. „Nonlinear Analysis of Conventional and Microstructure Dependent Functionally Graded Beams under Thermo-mechanical Loads“. Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-08-11478.
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Nonlinear finite element models of functionally graded beams with power-law variation of material, accounting for the von-Karman geometric nonlinearity and temperature dependent material properties as well as microstructure dependent length scale have been developed using the Euler-Bernoulli as well as the first-order and third- order beam theories. To capture the size effect, a modified couple stress theory with one length scale parameter is used. Such theories play crucial role in predicting accurate deflections of micro- and nano-beam structures. A general third order beam theory for microstructure dependent beam has been developed for functionally graded beams for the first time using a modified couple stress theory with the von Karman nonlinear strain. Finite element models of the three beam theories have been developed. The thermo-mechanical coupling as well as the bending-stretching coupling play significant role in the deflection response. Numerical results are presented to show the effect of nonlinearity, power-law index, microstructural length scale, and boundary conditions on the bending response of beams under thermo-mechanical loads. In general, the effect of microstructural parameter is to stiffen the beam, while shear deformation has the effect of modeling more realistically as a flexible beam.
Bücher zum Thema "Microstructures under stress"
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Kaufman, J. Gilbert, und Elwin L. Rooy. Aluminum Alloy Castings. ASM International, 2004. http://dx.doi.org/10.31399/asm.tb.aacppa.9781627083355.
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Aluminum Alloy Castings: Properties, Processes and Applications is a practical guide to the process, structure, property relationships associated with aluminum alloy castings and casting processes. It covers a wide range of casting methods, including variations of sand casting, permanent mold casting, and pressure die casting, showing how key process variables affect the microstructure, properties, and performance of cast aluminum parts. Other chapters provide similar information on the effects of alloying and heat treating and the influence and control of porosity and inclusions. A significant portion of the book contains curated collections of property and performance data, including many previously unpublished aging response curves, growth curves, and fatigue curves; tensile properties at high and low temperatures and at room temperature after high-temperature exposure; the results of creep rupture tests conducted at temperatures from 212 to 600 °F (100 to 315 °C); and stress-strain curves obtained from casting alloys in various tempers under tensile or compressive loads. The book also discusses the factors that contribute to corrosion and fracture resistance and includes test specimen drawings as well as a glossary of terms. For information on the print version, ISBN 978-0-87170-803-8, follow this link.
Buchteile zum Thema "Microstructures under stress"
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Veyssière, P. „Dislocation Organization Under Stress : Tial“. In Thermodynamics, Microstructures and Plasticity, 497–506. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-010-0219-6_31.
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Ohmura, Takahito. „Nanomechanical Characterization of Metallic Materials“. In The Plaston Concept, 157–95. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-7715-1_8.
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AbstractMechanical behavior of metallic materials on nanoscale is characterized by using Nanoindentation and Transmission Electron Microscope (TEM) to understand the fundamental plasticity mechanisms associated with microstructural factors including dislocations. The advanced characterization techniques enable us to grasp the behavior on the nanoscale in detail. New knowledges are obtained for the plasticity initiation under the extremely high stress close to the theoretical strength in regions with defect-free matrix and pre-existing defects such as grain boundaries, in-solution elements, and dislocations. The grain boundaries act as an effective dislocation source, the in-solution elements retard a nucleation of dislocation, and the pre-existing dislocations assist a plasticity initiation. The deformation behavior associated with microstructures is also described. The dislocation structure with a certain density was observed right after indentation-induced strain burst, which is so-called “pop-in,” suggesting a dislocation avalanche upon the pop-in. It has been directly observed that the lower mobility screw dislocation causes the higher flow stress in a bcc metal. A remarkable strain softening can be understood by an increase in dislocation density based on conventional physical models. Phase stability for indentation-induced transformation depends on a constraint effect by inter-phase boundary and grain boundary.
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Cook, Robert F. „Microstructural Control of Indentation Crack Extension under Externally Applied Stress“. In Fracture Mechanics of Ceramics, 57–67. Boston, MA: Springer US, 2005. http://dx.doi.org/10.1007/978-0-387-28920-5_5.
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Shibayama, Tamaki, Yutaka Yoshida, Yasuhide Yano und Heishichiro Takahashi. „Microstructure Evolution in Highly Crystalline SiC Fiber Under Applied Stress Environments“. In Ceramic Transactions Series, 301–7. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2012. http://dx.doi.org/10.1002/9781118406014.ch27.
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Duh, Jenq-Gong, Kuo-Chuan Liu und Bi-Shiou Chiou. „Microstructural Evaluation of Sn-Pb Solder and Pd-Ag Thick-Film Conductor Metallization Under Thermal Cycling and Aging Conditions“. In Thermal Stress and Strain in Microelectronics Packaging, 532–78. Boston, MA: Springer US, 1993. http://dx.doi.org/10.1007/978-1-4684-7767-2_17.
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Itoh, Yasumi, und Akira Shimamoto. „Effect of Microstructure on Fatigue Crack Growth Resistance of Magnesium Alloy under Biaxial Stress“. In Key Engineering Materials, 1559–64. Stafa: Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/0-87849-978-4.1559.
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Popov, D., S. Sinogeikin, C. Park, E. Rod, J. Smith, R. Ferry, C. Kenney-Benson, N. Velisavljevic und G. Shen. „New Laue Micro-diffraction Setup for Real-Time In Situ Microstructural Characterization of Materials Under External Stress“. In Advanced Real Time Imaging II, 43–48. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-06143-2_5.
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Li, D. Y., und L. Q. Chen. „Computer Simulation of Microstructural Evolution Under External Stresses“. In Computer-Aided Design of High-Temperature Materials, 212–28. Oxford University PressNew York, NY, 1999. http://dx.doi.org/10.1093/oso/9780195120509.003.0017.
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Abstract Coherent microstructures and their stability are influenced by both external and internal stresses. During thermo-mechanical processes such as constrained aging, external stresses are applied to modify microstructures for improved performance. This article summarizes our recent computational studies on microstructural evolution under applied stresses or strains, using a diffuse-interface phase-field approach. The coupling between an applied stress and the transformation strain in a coherent twophase microstructure and its variation with different constraints are discussed.
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Mlikota, M. „On the Critical Resolved Shear Stress and its Importance in the Fatigue Performance of Steels and other Metals with Different Crystallographic Structures“. In Multiscale and Multiphysics Modelling of Materials, 37–65. Materials Research Forum LLC, 2022. http://dx.doi.org/10.21741/9781644901656-3.
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This study deals with the numerical estimation of the fatigue life represented in the form of strength-life (S-N, or Wöhler) curves of metals with different crystallographic structures, namely body-centered cubic (BCC) and face-centered cubic (FCC). Their life curves are determined by analyzing the initiation of a short crack under the influence of microstructure and subsequent growth of the long crack, respectively. Micro-models containing microstructures of the materials are set up by using the finite element method (FEM) and are applied in combination with the Tanaka-Mura (TM) equation in order to estimate the number of cycles required for the crack initiation. The long crack growth analysis is conducted using the Paris law. The study shows that the crystallographic structure is not the predominant factor that determines the shape and position of the fatigue life curve in the S-N diagram, but it is rather the material parameter known as the critical resolved shear stress (CRSS). Even though it is an FCC material, the investigated austenitic stainless steel AISI 304 shows an untypically high fatigue limit (208 MPa), which is higher than the fatigue limit of the BCC vanadium-based micro-alloyed forging steel AISI 1141 (152 MPa).
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Mlikota, M. „Calculation of the Wöhler (S-N) Curve Using a Two-Scale Model“. In Multiscale and Multiphysics Modelling of Materials, 16–36. Materials Research Forum LLC, 2022. http://dx.doi.org/10.21741/9781644901656-2.
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This chapter deals with the initiation of a short crack and subsequent growth of the long crack in a carbon steel under cyclic loading, concluded with the estimation of the complete lifetime represented by the Wöhler (S-N) curve. A micro-model containing the microstructure of the material is generated using the Finite Element Method and the according non-uniform stress distribution is calculated afterwards. The number of cycles needed for crack initiation is estimated on the basis of the stress distribution in the microstructural model and by applying the physically-based Tanaka-Mura model. The long crack growth is handled using the Paris law. The analysis yields good agreement with experimental results from literature.
Konferenzberichte zum Thema "Microstructures under stress"
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Kang, Young Sup, Ryan D. Evans und Gary L. Doll. „Contact Mechanism of Tribological Coatings With Columnar Microstructure“. In STLE/ASME 2008 International Joint Tribology Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/ijtc2008-71119.
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Tribological coatings for mechanical components such as bearings and gears can experience failure occurring at the surface for highly localized contact conditions. In the present study, a finite element analysis (FEA) model was developed to study the stress distribution and deformation of tungsten carbide reinforced amorphous hydrocarbon coatings with and without columnar microstructures under nanoindentation. Results show that the microstructure of these tribological coatings significantly influences the stress distribution and deformation under heavily loaded conditions.
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Mueller, Andrew J., und Robert D. White. „Residual Stress Variation in Polysilicon Thin Films“. In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-13764.
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This paper compares the use of four mechanical methods for characterization of residual stress variation in low pressure chemical vapor deposited (LPCVD) polysilicon thin films deposited, doped, and annealed under different conditions. Stress was determined using buckling structures, vibrating microstructures, static rotating structures and the wafer curvature method. After deposition of 1.0 μm of polysilicon at 625°C and 588°C the stress in the wafers is 230 MPa compressive (stdev = 1.2 MPa) and 340 MPa compressive (stdev = 10.4 MPa), respectively. Deposition of 0.6 μm at 580°C results in a tensile stress of 66 MPa (stdev= 52 MPa). Following doping, all stresses are compressive. Boron doping of the 625°C and 588°C deposited films produces a compressive stress of 149 MPa (stdev= 28.6 MPa) and 100 MPa (stdev= 29.5 MPa). Phosphorous doping of the 588°C and 580°C deposited films produces a compressive stress of 54 MPa (stdev = 0.3 MPa) and 80 MPa (stdev= 5.3 MPa), respectively. Annealing through rapid thermal processing (RTP) at temperatures of 1000°C – 1100°C reduced the stresses by 20-50 MPa, but the stresses remained compressive. These values are measured using the wafer curvature method. Values obtained from the other microstructure methods agree with stresses determined by wafer curvature with the exception of the rotating structures which showed 20% lower stress readings.
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Kermanidis, Alexis T., und Spiros G. Pantelakis. „Fatigue Crack Growth and Remaining Life Assessment of 2024 Aluminum With Variation in Microstructure“. In ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-78019.
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The LTSM-F crack growth model is implemented in the present work for the assessment of crack growth and remaining fatigue life of 2024 aluminium alloy with different microstructure. The effect of microstructure in the crack growth analysis is simulated by means of respective yield strength and fracture toughness values of the material. The analytical results obtained are compared against experimental results performed on a series of fatigue crack growth specimens of the alloy under constant amplitude and irregular loading including overload and real stress histories. The analytical results demonstrate the potential of the model to account for crack growth behaviour under irregular loading conditions of dissimilar microstructures.
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Honma, Yuta, und Kunihiko Hashi. „Effect of Residual Stress on High Temperature Hydrogen Attack for Pressure Vessels“. In ASME 2019 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/pvp2019-94058.
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Abstract Nelson curve for carbon steel without post welding heat treatment (PWHT) was reconsidered in Annex F of API PR941 8th Edition because a lot of hydrogen damage cases of carbon steel for pressure vessels and pipes with weld joint were reported. However the mechanism of the damage initiation has not been extensively studied. For these reason, the purpose of this study was to clarify effect of residual stress on high temperature hydrogen attack (HTHA) and examine the mechanism in terms of microstructure. The specimens that were simulated welding residual stress by four point bending tool were exposed to high temperature and high pressure hydrogen gas to investigate relationship between damage initiation and condition of temperature and pressure. The frequency of damage occurred by residual stress under high temperature and low hydrogen pressure conditions was higher than that under low temperature and high pressure condition. The damage occurred on boundary of ferrite and pearlite. The grain reference orientation deviation (GROD) map obtained from EBSD measurement indicated the concentration of strain on the boundary generated by plastic deformation. Thus, the damage is most likely initiated by concentration of hydrogen on ferrite-pearlite boundary at which welding strain accumulated. Moreover the damage susceptibility of ferrite-pearlite structure was higher than that of bainite structure. The microstructures in base metal is ferrite-pearlite, but that in heat affected zone is bainite by reheating and cooling at welding. Hence, the base metal has higher damage susceptibility than HAZ.
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Olasumboye, Adewale, Gbadebo Owolabi, Olufemi Koya, Horace Whitworth und Nadir Yilmaz. „Comparative Study of the Dynamic Behavior of AA2519 Aluminum Alloy in T6 and T8 Temper Conditions“. In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-10978.
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Abstract This study investigates the dynamic response of AA2519 aluminum alloy in T6 temper condition during plastic deformation at high strain rates. The aim was to determine how the T6 temper condition affects the flow stress response, strength properties and microstructural morphologies of the alloy when impacted under compression at high strain rates. The specimens (with aspect ratio, L/D = 0.8) of the as-cast alloy used were received in the T8 temper condition and further heat-treated to the T6 temper condition based on the standard ASTM temper designation procedures. Split-Hopkinson pressure bar experiment was used to generate true stress-strain data for the alloy in the range of 1000–3500 /s strain rates while high-speed cameras were used to monitor the test compliance with strain-rate constancy measures. The microstructures of the as received and deformed specimens were assessed and compared for possible disparities in their initial microstructures and post-deformation changes, respectively, using optical microscopy. Results showed no clear evidence of strain-rate dependency in the dynamic yield strength behavior of T6-temper designated alloy while exhibiting a negative trend in its flow stress response. On the contrary, AA2519-T8 showed marginal but positive response in both yield strength and flow behavior for the range of strain rates tested. Post-deformation photomicrographs show clear disparities in the alloys’ initial microstructures in terms of the second-phase particle size differences, population density and, distribution; and in the morphological changes which occurred in the microstructures of the different materials during large plastic deformation. AA2519-T6 showed a higher susceptibility to adiabatic shear localization than AA2519-T8, with deformed and bifurcating transformed band occurring at 3000 /s followed by failure at 3500 /s.
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Zakin, Jacques L., Yunying Qi und Ying Zhang. „Recent Experimental Results on Surfactant Drag Reduction“. In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45654.
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Certain surfactant solutions are drag reducing in turbulent shear flows. Because they “self-repair” after mechanical degradation, they are very attractive for reducing pumping energy losses in recirculating water applications such as district heating and cooling systems. Some surfactant systems reduce drag below the Virk limiting drag reduction asymptote for high polymers. The surfactant asymptote is 40% below that for polymers and the limiting velocity profile slope for highly drag reducing surfactant systems is about twice that for polymers. Like polymers, surfactants show low turbulence intensities normal to the wall and may exhibit zero Reynolds stresses requiring the postulation of an “elastic” stress to satisfy the total stress balance. The influences of counterion chemical structure and shear on microstructures, rheology and therefore drag reduction of cationic surfactant solutions are also addressed. Viscoelasticity, high extensional/shear viscosity ratios and threadlike microstructures have been proposed as necessary physical criteria for surfactant drag reduction. Recently, however, several non-viscoelastic drag reducing surfactant solution systems (zero first normal stress differences, no recoil and no stress overshoot) have been reported. Most drag reducing surfactant solutions have extensional to shear viscosity ratios of 100 or more. However, two solutions with a low ratio in the shear/extensional rate range of 20∼1000 s−1 have been observed. The ratio tends to increase at higher extensional rates, however, so the second criterion may be valid. Finally, cryo-TEM images of some drag reducing surfactant micelle microstructures which lacked threadlike structures in the quiescent state have been observed. However, Zheng et al. [1] showed that vesicle microstructures in the quiescent state can change to threadlike micelles under shear, supporting the third criterion.
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Wang, Yun-Che, Jun-Liang Chen, Ming-Liang Liao, Chuan Chen, Yan-Chi Chen und Chi-Chuan Hwang. „Stress and Temperature Analysis of the Copper Substrate Indented With Nanotubes and Nanocones“. In ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer. ASMEDC, 2009. http://dx.doi.org/10.1115/mnhmt2009-18379.
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It has been shown that nanotubes and nanocones are most effective to make indents with large aspect ratios. Detailed studies in the heat transfer processes under the nano-scale indentation, and the accompanying stress distributions are required much attention. In this study, the copper substrate was indented with a nanotube or nano-cone. It is found that nano-cones may make indents with larger aspect ratios than the nanotubes due to the local shell buckling. Time-domain heat transfer and stress analysis was carried out by using a control-volume technique with an atomic spatial resolution, except near the boundaries. The effect of temperatures and stresses on the changes of the microstructures of the substrate will be discussed.
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Bahrami, Amir, Anais Bourgeon und Mohamad Cheaitani. „Effects of Strain Rate and Microstructure on Fracture Toughness of Duplex Stainless Steels Under Hydrogen Charging Conditions“. In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49131.
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Failures of ferritic-austenitic stainless steel due to hydrogen induced stress cracking (HISC) have been very costly and raised concerns regarding subsea system integrity, some of which remain unresolved. The susceptibility to HISC crack initiation shows a strong correlation with austenite spacing and tests performed on smooth samples have shown that coarse-grained microstructures, with large austenite spacing, such as in forgings, are more susceptible to HISC than fine grained structures, eg as in pipe [1]. In all reported failures, cracking has been independent of the presence of fabrication flaws, even though welds were typically present, and initiated at external stress concentrators, so the importance of flaws remains undetermined. There is no well established method for determining fracture toughness values applicable to flaws in duplex stainless steel in the presence of hydrogen and hence reliable data do not exist, leading to a lack of understanding of the criticality of flaws and whether fine austenite spacing provides any benefit in resistance to extension of flaws. This paper provides new data from fracture toughness tests conducted on duplex pipe and forging parent materials, to explore the effect of product type/ microstructure and strain rate on fracture toughness under active charging in seawater under cathodic polarisation. This is part of ongoing work aimed at the development of an engineering critical assessment (ECA) approach for assessing flaw tolerance under hydrogen charging conditions.
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Owolabi, Gbadebo, Daniel Odoh, Akindele Odeshi und Horace Whitworth. „Modeling and Simulation of Adiabatic Shear Bands in AISI 4340 Steel Under Impact Loads“. In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-89084.
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In this study, the effects of microstructure and strain rate on the occurrence and failure of adiabatic shear bands in AISI 4340 steel under high velocity impact loads are investigated using finite element analysis and experimental tests. The shear band generated due to impact load was divided into some set of elements separated by nodes using finite element method in ABAQUS environment with initial and boundary conditions specified. The material properties were assumed to be lower at the second element set in order to initialize the adiabatic shear bands. The strain energy density for each successive node was calculated successively starting from the first element where initial boundary condition, initial strain hardening constant, and stress resistance had been specified. As the load time is increased, its corresponding effect on the localized shear deformation and width of the adiabatic shear band was also determined. The finite element model was used to determine the maximum stress, the strain hardening, the thermal softening, and the time to reach critical strain for formation of adiabatic shear bands. Experimental results show that deformed bands were formed at low strain rates and there was a minimum strain rate required for formation of transformed band in the alloy. The experimental results also show that cracks were initiated and propagated along transformed bands leading to fragmentation under the impact loading. The susceptibility of the adiabatic shear bands to cracking was markedly influenced by strain-rates and the initial material microstructures. The numerical results obtained were compared with the experimental results obtained for the AISI 4340 steel under high strain-rate loading in compression using split impact Hopkinson bars. A good agreement between the experimental and simulation results are also obtained.
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Lee, Ki Myung, und Andreas A. Polycarpou. „Micro/Nano Scale Wear Behavior of Pearlitic and Bainitic Rail Steels“. In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63735.
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To develop rails with higher hardness and thus better durability and longer life, alternative microstructures have been suggested, since conventional pearlitic rail steels have reached their hardness limit. Such a newly developed material has a fine bainite microstructure (coded J6 bainitic steel) and showed higher initial hardness but poorer on-site wear performance, compared to conventional pearlitic steels. This was explained by the fact that pearlitic steels show significant work hardening under severe stress conditions, even though their initial hardness was lower. In this work, the wear behavior of pearlitic and J6 bainitic rail steels was investigated at the micro/nano scale, using the nanoscratch technique. It was found that pearlitic steel shows better wear performance at the micro scale as well, in agreement with large scale rail field tests.
Berichte der Organisationen zum Thema "Microstructures under stress"
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Patchett, B. M., und A. C. Bicknell. L51706 Higher-Strength SMAW Filler Metals. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), Dezember 1993. http://dx.doi.org/10.55274/r0010418.
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The welding of high strength steels in general, and for pipeline fabrication in particular, has shown that cracking due to hydrogen absorption during welding is more complex in these steels than in older, lower strength steels. In older steels, primary strengthening was accomplished with carbon, which caused hydrogen cracking in the base metal HAZ under reasonably predictable conditions involving microstructure, residual stress and hydrogen level. Pipeline steels were and are in the vanguard of change in strengthening philosophy. The change involves two areas of steel making, chemical composition and deformation processing. Pipeline steels now contain low carbon levels, in many cases less than 0.10%, and the resulting lack of strength is reclaimed by adding higher alloy levels to promote solution hardening (e.g. Mn), precipitation hardening (e.g. Cb, Cu) or transformation hardening (e.g. MO). In addition, alloy elements are added to improve toughness at high strength levels (e.g. Ni). At the same time, improvements have been made in reducing impurity and residual element levels, notably for S, P and O and N. Limitations on the effects of alloying additions on strength and toughness encouraged the use of deformation processing, primarily during rolling, to promote fine-grained microstructures to increase strength andtoughness simultaneously. Electrodes for the SMAW process have been developed for welding high-strength pipeline steels by using core wires made from high-strength microalloyed skelp extruded with cellulosic (Exx10) and low hydrogen (Exx16) flux coatings. The required alloy elements for high-strength deposits were therefore obtained from the core wire and not ferroalloy powders added to the flux, as is standard industrial practice. The idea behind this change was two fold: to avoid the possibility of introducing impurities from the varying sources of ferro alloy powders, including oxygen from the oxidized powder surfaces, and also to provide a closer match of the microalloy level to modern pipeline steel chemistries. The unknowns in this work were the effects of lower impurities/similar alloy content on the mechanical properties in the cast microstructure of a weld, compared to a pipe, and of the effect on electrode welding behaviour of a flux containing no ferro powders other than FeSi.