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1
Dmowski, Wojtek, and Takeshi Egami. "Observation of structural anisotropy in metallic glasses induced by mechanical deformation." Journal of Materials Research 22, no. 2 (February 2007): 412–18. http://dx.doi.org/10.1557/jmr.2007.0043.
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We have investigated atomic structure of a Fe81B13Si4C2 metallic glass after mechanical creep deformation. We determined the structure function and pair density function resolved for azimuthal angle using x-ray scattering and a two-dimensional detector. The results are analyzed by the spherical harmonics expansion, and are compared to the often-used simple analysis of the anisotropic pair density function determined by measuring the structure function along two directions with respect to the stress. We observed uniaxial structural anisotropy in a sample deformed during creep experiment. The observed macroscopic shear strain is explained in terms of local bond anisotropy induced by deformation at elevated temperature. The bond anisotropy is a “memory” of this deformation after load was removed. We showed that use of sine-Fourier transformation to anisotropic glass results in systematic errors in the atomic pair distribution function.
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Kahraman, Hasan, and Edmund Haberstroh. "DIRECTION-DEPENDENT AND MULTIAXIAL STRESS-SOFTENING BEHAVIOR OF CARBON BLACK–FILLED RUBBER." Rubber Chemistry and Technology 87, no. 1 (March 1, 2014): 139–51. http://dx.doi.org/10.5254/rct.13.87910.
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ABSTRACT The mechanical behavior of filled rubbers depends on the maximum stretch previously reached and consequently on the induced stress softening. This softening effect is referred to as the Mullins effect. Current investigations point out that the Mullins effect exhibits a significant directional dependence, which calls for an anisotropic material model. But for the formulation and validation of anisotropic material models, there is still a lack of suitable experimental data. For this the purpose, experiments based on chloroprene rubber (CR) are reported. To trace the anisotropic Mullins effect, the standard test method for characterization of the isotropic mechanical behavior must be extended. The appropriate type of specimen enables us to perform multiple load steps with alternating load directions. After repeated stretching in the same direction, a subsequent first uniaxial loading in any other direction is characterized by a stiffer stress–strain behavior compared with the stabilized curve of the previous primary load. Hence, the experimental results confirm the deformation-induced anisotropy. To identify the multiaxial material behavior after the prestretching in one direction, a biaxial tensile-testing machine is developed. A specific property of the biaxial tensile-testing machine is the independent control of both the loading axes. Thus, the rubber material can be subjected to arbitrary loading histories. Therefore, a cross-shaped specimen with four arms is used. Multiple slits parallel to the sides on each arm ensures the homogenous uniaxial load condition in the primary load. In the secondary load step, the loading axis, which was previously inactive, is moved in a uniform manner as the master axis or in any arbitrary defined ratio. The experimental results confirm the deformation-induced anisotropy of the Mullins effect. In summary, the material behavior significantly results from the deformation mode and the loading direction applied in the loading history.
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Litewka, A. "Load-induced oriented damage and anisotropy of rock-like materials." International Journal of Plasticity 19, no. 12 (December 2003): 2171–91. http://dx.doi.org/10.1016/s0749-6419(03)00064-0.
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Karasahin, Mustafa. "An anisotropic model of unbound granular material under repeated loading." Thermal Science 23, Suppl. 1 (2019): 295–302. http://dx.doi.org/10.2298/tsci181021043k.
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The base and subbase layers of a pavement are compacted to the desired density by rollers. This cause the anisotropy in other words the layer more stiffer in the vertical direction than the horizontal direction. In the study inherent and stress induced anisotropy were measured by using the repeated load triaxial test equipment which is able to cycle both confining and axial pressure. The test results were then modelled using the stepwise regression. A new cross anisotropic model was proposed to predict the unbound stress-strain behavior. The proposed model is able to predict the axial strain more accurately than the radial strain.
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De Marchi, Nico, WaiChing Sun, and Valentina Salomoni. "Shear Wave Splitting and Polarization in Anisotropic Fluid-Infiltrating Porous Media: A Numerical Study." Materials 13, no. 21 (November 5, 2020): 4988. http://dx.doi.org/10.3390/ma13214988.
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The triggering and spreading of volumetric waves in soils, namely pressure (P) and shear (S) waves, developing from a point source of a dynamic load, are analyzed. Wave polarization and shear wave splitting are innovatively reproduced via a three-dimensional Finite Element research code upgraded to account for fast dynamic regimes in fully saturated porous media. The mathematical–numerical model adopts a u-v-p formulation enhanced by introducing Taylor–Hood mixed finite elements and the stability features of the solution are considered by analyzing different implemented time integration strategies. Particularly, the phenomena have been studied and reconstructed by numerically generating different types of medium anisotropy accounting for (i) an anisotropic solid skeleton, (ii) an anisotropic permeability tensor, and (iii) a Biot’s effective stress coefficient tensor. Additionally, deviatoric-volumetric coupling effects have been emphasized by specifically modifying the structural anisotropy. A series of analyses are conducted to validate the model and prove the effectiveness of the results, from the directionality of polarized vibrations, the anisotropy-induced splitting, up to the spreading of surface waves.
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Thomopoulos, Stavros, Gregory M. Fomovsky, Preethi L. Chandran, and Jeffrey W. Holmes. "Collagen Fiber Alignment Does Not Explain Mechanical Anisotropy in Fibroblast Populated Collagen Gels." Journal of Biomechanical Engineering 129, no. 5 (February 15, 2007): 642–50. http://dx.doi.org/10.1115/1.2768104.
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Many load-bearing soft tissues exhibit mechanical anisotropy. In order to understand the behavior of natural tissues and to create tissue engineered replacements, quantitative relationships must be developed between the tissue structures and their mechanical behavior. We used a novel collagen gel system to test the hypothesis that collagen fiber alignment is the primary mechanism for the mechanical anisotropy we have reported in structurally anisotropic gels. Loading constraints applied during culture were used to control the structural organization of the collagen fibers of fibroblast populated collagen gels. Gels constrained uniaxially during culture developed fiber alignment and a high degree of mechanical anisotropy, while gels constrained biaxially remained isotropic with randomly distributed collagen fibers. We hypothesized that the mechanical anisotropy that developed in these gels was due primarily to collagen fiber orientation. We tested this hypothesis using two mathematical models that incorporated measured collagen fiber orientations: a structural continuum model that assumes affine fiber kinematics and a network model that allows for nonaffine fiber kinematics. Collagen fiber mechanical properties were determined by fitting biaxial mechanical test data from isotropic collagen gels. The fiber properties of each isotropic gel were then used to predict the biaxial mechanical behavior of paired anisotropic gels. Both models accurately described the isotropic collagen gel behavior. However, the structural continuum model dramatically underestimated the level of mechanical anisotropy in aligned collagen gels despite incorporation of measured fiber orientations; when estimated remodeling-induced changes in collagen fiber length were included, the continuum model slightly overestimated mechanical anisotropy. The network model provided the closest match to experimental data from aligned collagen gels, but still did not fully explain the observed mechanics. Two different modeling approaches showed that the level of collagen fiber alignment in our uniaxially constrained gels cannot explain the high degree of mechanical anisotropy observed in these gels. Our modeling results suggest that remodeling-induced redistribution of collagen fiber lengths, nonaffine fiber kinematics, or some combination of these effects must also be considered in order to explain the dramatic mechanical anisotropy observed in this collagen gel model system.
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Barret, C., and S. Baste. "Effective Elastic Stiffnesses of an Anisotropic Medium Permeated by Tilted Cracks." Journal of Applied Mechanics 66, no. 3 (September 1, 1999): 680–86. http://dx.doi.org/10.1115/1.2791562.
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This paper is concerned with the relationship between the effective stiffness tensor and the intensity of damage in individual modes for an anisotropic material with tilted cracks. The predictions are compared favorably with the experimentally measured load-induced changes of the 13 stiffnesses of a two-dimensional C/C-SiC ceramic matrix composite subjected to an off-axis solicitation. By taking into account the thickness of the cracks, it is possible to understand the change of the elastic anisotropy of the material and of its inelastic strain.
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Prioul, Romain, Andrey Bakulin, and Victor Bakulin. "Nonlinear rock physics model for estimation of 3D subsurface stress in anisotropic formations: Theory and laboratory verification." GEOPHYSICS 69, no. 2 (March 2004): 415–25. http://dx.doi.org/10.1190/1.1707061.
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We develop a rock physics model based on nonlinear elasticity that describes the dependence of the effective stiffness tensor as a function of a 3D stress field in intrinsically anisotropic formations. This model predicts the seismic velocity of both P‐ and S‐waves in any direction for an arbitrary 3D stress state. Therefore, the model overcomes the limitations of existing empirical velocity‐stress models that link P‐wave velocity in isotropic rocks to uniaxial or hydrostatic stress. To validate this model, we analyze ultrasonic velocity measurements on stressed anisotropic samples of shale and sandstone. With only three nonlinear constants, we are able to predict the stress dependence of all five elastic medium parameters comprising the transversely isotropic stiffness tensor. We also show that the horizontal stress affects vertical S‐wave velocity with the same order of magnitude as vertical stress does. We develop a weak‐anisotropy approximation that directly links commonly measured anisotropic Thomsen parameters to the principal stresses. Each Thomsen parameter is simply a sum of corresponding background intrinsic anisotropy and stress‐induced contribution. The stress‐induced part is controlled by the difference between horizontal and vertical stresses and coefficients depending on nonlinear constants. Thus, isotropic rock stays isotropic under varying but hydrostatic load, whereas transversely isotropic rock retains the same values of dimensionless Thomsen parameters. Only unequal horizontal and vertical stresses alter anisotropy. Since Thomsen parameters conveniently describe seismic signatures, such as normal‐moveout velocities and amplitude‐variation‐with‐offset gradients, this approximation is suitable for designing new methods for the estimation of 3D subsurface stress from multicomponent seismic data.
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Yeh, Wei-Ching, Chia-Dou Ho, and Wen-Fung Pan. "An endochronic theory accounting for deformation induced anisotropy of metals under biaxial load." International Journal of Plasticity 12, no. 8 (January 1996): 987–1004. http://dx.doi.org/10.1016/s0749-6419(96)00038-1.
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Niazi, M. S., V. Timo Meinders, H. H. Wisselink, C. H. L. J. ten Horn, Gerrit Klaseboer, and A. H. van den Boogaard. "A Plasticity Induced Anisotropic Damage Model for Sheet Forming Processes." Key Engineering Materials 554-557 (June 2013): 1245–51. http://dx.doi.org/10.4028/www.scientific.net/kem.554-557.1245.
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The global fuel crisis and increasing public safety concerns are driving the automotive industry to design high strength and low weight vehicles. The development of Dual Phase (DP) steels has been a big step forward in achieving this goal. DP steels are used in many automotive body-in-white structural components such as A and B pillar reinforcements, longitudinal members and crash structure parts. DP steels are also used in other industrial sectors such as precision tubes, train seats and Liquid Petroleum Gas (LPG) cylinders. Although the ductility of DP steel is higher than classical high strength steels, it is lower than that of classical deep drawing steels it has to replace. The low ductility of DP steels is attributed to damage development. Damage not only weakens the material but also reduces the ductility by formation of meso-cracks due to interacting micro defects. Damage in a material usually refers to presence of micro defects in the material. It is a known fact that plastic deformation induces damage in DP steels. Therefore damage development in these steels have to be included in the simulation of the forming process. In ductile metals, damage leads to crack initiation. A crack is anisotropic which makes damage anisotropic in nature. However, most researchers assume damage to be an isotropic phenomenon. For correct and accurate simulation results, damage shall be considered as anisotropic, especially if the results are used to determine the crack propagation direction. This paper presents an efficient plasticity induced anisotropic damage model to simulate complex failure mechanisms and accurately predict failure in macro-scale sheet forming processes. Anisotropy in damage can be categorized based on the cause which induces the anisotropy, i.e. the loading state and the material microstructure. According to the Load Induced Anisotropic Damage (LIAD) model, if the material is deformed in one direction then damage will be higher in this direction compared to the other two orthogonal directions, irrespective of the microstructure of the material. According to Material Induced Anisotropic Damage (MIAD) model, if there is an anisotropy in shape or distribution of the particles responsible for damage (hard second phase particles, inclusions or impurities) then the material will have different damage characteristics for different orientations in the sheet material. The LIAD part of the damage model is a modification of Lemaitre’s (ML) anisotropic damage model. Modifications are made for damage development under compression state and influence of strain rate on damage, and are presented in this paper. Viscoplastic regularization is used to avoid pathological mesh dependency. The MIAD part of the model is an extension of the LIAD model. Experimental evidence is given of the MIAD phenomenon in DP600 steel. The experimental analysis is carried out using tensile tests, optical strain measurement system (ARAMIS) and scanning electron microscopy. The extension to incorporate MIAD in the ML anisotropic damage model is presented in this paper as well. The paper concludes with a validation of the anisotropic damage model for different applications. The MIAD part of the model is validated by experimental cylindrical cup drawing wheras the LIAD part of the model is validated by the cross die drawing process.
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Zhang, Kun Yong, Yan Gang Zhang, and Chi Wang. "Anisotropic Behavior of Geomaterial under Three-Dimensional Stress States." Advanced Materials Research 160-162 (November 2010): 1425–31. http://dx.doi.org/10.4028/www.scientific.net/amr.160-162.1425.
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Most soil constitutive models were developed based on the traditional triaxial tests with isotropic assumption, in which the load is applied as the major principal stress direction and the other two principal stresses are symmetric. When such isotropic models are applied to practical analysis, stress induced anisotropy under complex stress state and the middle principal stress effects are often neglected, thus there are many disagreements between the calculated results and the infield testing data. To simulate the practical loading process, true triaxial tests were carried out on geomaterial under three-dimensional stress state. It was found that the stress induced anisotropy effects are remarkable and the middle principal stress effects are obvious because of the initial three-dimensional stress state. Such kind of stress-induced anisotropy could have important impact on the numerical analysis results and should be taken into consideration when developing the constitutive model.
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Zhang, Kunyong, Zhenjun Zang, Leslie Okine, and Jose Luis Chavez Torres. "Microstudy of the Anisotropy of Sandy Material." Advances in Civil Engineering 2018 (August 14, 2018): 1–13. http://dx.doi.org/10.1155/2018/3971643.
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Through numerical simulation based on the particle flow method, DEM numerical test samples were generated with the results of laboratory tests on standard sand. The method consists of the use of gravity deposition and radius expansion modeling of irregular sand particles, where samples of the biaxial test are assembled by generated long particle units. Different steps of deposition or initial stresses were applied during the sample generation process in order to simulate different sample states. The loads from the horizontal and vertical directions are, respectively, applied to samples, and then the stress-strain curve and macroscopic mechanical parameters are acquired. The numerical experiment results show that the gravitational deposits have significant impact on the major axis orientation arrangement of particles and on the average coordination number, as well as the initial stress has a significant effect on it. There is a remarkable effect on the stress-strain curve and on the acquired mechanical parameters as a result of the application of load to samples from the horizontal and vertical directions. The sand samples show an obvious property of inherent anisotropy and stress-induced anisotropy.
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Kourkoulis, S. K. "Quantifying the Plastic Anisotropy for Particulate Metal Matrix Composites." Advanced Composites Letters 11, no. 4 (July 2002): 096369350201100. http://dx.doi.org/10.1177/096369350201100401.
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The failure of orthotropic materials, traditionally described by Hill's criterion, in terms of the anisotropy ratio r, i.e. the ratio of transverse to through thickness increments of logarithmic strain, is studied in the present work. In spite of the critical role of r for the description of the failure of such materials, its quantification is not yet standardized. Based on results obtained from long series of experiments r is here quantified, for the case of a modern particulate composite material, extensively used in aerospace applications. The variation of r versus the level of the plastic strain is determined and it is concluded that its values depend both on the orientation of the specimen and load with respect to the initial orthotropy axes as well as on the plastic strain induced in case the specimen and load are not oriented along one of the axes of orthotropy.
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Zhang, Zheng-Zheng, You-Rong Chen, Shao-Jie Wang, Feng Zhao, Xiao-Gang Wang, Fei Yang, Jin-Jun Shi, et al. "Orchestrated biomechanical, structural, and biochemical stimuli for engineering anisotropic meniscus." Science Translational Medicine 11, no. 487 (April 10, 2019): eaao0750. http://dx.doi.org/10.1126/scitranslmed.aao0750.
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Reconstruction of the anisotropic structure and proper function of the knee meniscus remains an important challenge to overcome, because the complexity of the zonal tissue organization in the meniscus has important roles in load bearing and shock absorption. Current tissue engineering solutions for meniscus reconstruction have failed to achieve and maintain the proper function in vivo because they have generated homogeneous tissues, leading to long-term joint degeneration. To address this challenge, we applied biomechanical and biochemical stimuli to mesenchymal stem cells seeded into a biomimetic scaffold to induce spatial regulation of fibrochondrocyte differentiation, resulting in physiological anisotropy in the engineered meniscus. Using a customized dynamic tension-compression loading system in conjunction with two growth factors, we induced zonal, layer-specific expression of type I and type II collagens with similar structure and function to those present in the native meniscus tissue. Engineered meniscus demonstrated long-term chondroprotection of the knee joint in a rabbit model. This study simultaneously applied biomechanical, biochemical, and structural cues to achieve anisotropic reconstruction of the meniscus, demonstrating the utility of anisotropic engineered meniscus for long-term knee chondroprotection in vivo.
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Panich, Sansot, Vitoon Uthaisangsuk, Surasak Suranuntchai, and Suwat Jirathearanat. "Anisotropic Plastic Behavior of TRIP 780 Steel Sheet in Hole Expansion Test." Key Engineering Materials 504-506 (February 2012): 89–94. http://dx.doi.org/10.4028/www.scientific.net/kem.504-506.89.
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Plastic behavior of advanced high strength steel sheet of grade TRIP780 (Transformation Induced Plasticity) was investigated using three different yield functions, namely, the von Mises’s isotropic, Hill’s anisotropic (Hill’48), and Barlat’s anisotropic (Yld2000-2d) criterion. Uniaxial tensile and balanced biaxial test were conducted for the examined steel in order to characterize flow behavior and plastic anisotropy in different stress states. Additionally, disk compression test was performed for obtaining the balanced r-value. According to the different yield criteria, yield stresses and r-values were calculated for different directions and then compared with experimental data. To verify the modeling accuracy, a hole expansion test was carried out experimentally and numerically by FE simulation. Stress-strain curve from the biaxial test was described using voce and swift hardening models. Punch load and stroke, final hole radius, and strain distribution on specimen surface along the hole circumference and the specimen diameter in rolling and transverse directions were determined and compared with the experimental results. It was found that the simulations applying Yld2000-2d yield function provided an acceptable agreement. Consequently, it is noted that the anisotropic yield potential significantly affects the accuracy of the predicted deformation behavior of sheet metal subjected to hole expanding load.
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Moehring, Kerstin, and Frank Walther. "Load Direction-Dependent Influence of Forming-Induced Initial Damage on the Fatigue Performance of 16MnCrS5 Steel." Materials 13, no. 12 (June 12, 2020): 2680. http://dx.doi.org/10.3390/ma13122680.
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Forming processes influence the mechanical properties of manufactured workpieces in general and by means of forming-induced initial damage in particular. The effect of the latter on performance capability is the underlying research aspect for the investigations conducted. In order to address this aspect, fatigue tests under compressive, tensile and compressive-tensile loads were set-up with discrete block-by-block increased amplitudes and constant amplitudes, and performed up to fracture or distinct lifetimes. Aiming at the correlation of the macroscale mechanical testing results at the mesoscale, intensive metallographic investigations of cross-sections using the microscopical methods of secondary electron analysis, energy dispersive spectroscopy and electron backscatter diffraction were performed. Thereby, the correlation of forming-induced initial damage and fatigue performance was determined, the relevance of compressive loads for the cyclic damage evolution was shown, and material anisotropy under compressive loads was indicated. Finally, the need was addressed to perform further investigations regarding crack propagations and crack arrest investigations in order to clarify the mechanism by which initial damage affects cyclic damage evolution. The relevance of the principal stress axis relative to the extrusion direction was emphasized and used as the basis of an argument for investigations under load paths with different stress directions.
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Lukshina, V. A., N. V. Dmitrieva, and A. P. Potapov. "Field- and Stress-Induced Magnetic Anisotropy in Nanocrystalline Fe-Based and Amorphous Co-Based Alloys." Textures and Microstructures 32, no. 1-4 (January 1, 1999): 289–94. http://dx.doi.org/10.1155/tsm.32.289.
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For nanocrystalline alloy Fe73.5Cu1Nb3Si13.5B9 thermomechanical treatment was carried out simultaneously with nanocrystallizing annealing (1) or after it (2). It was shown that a change in magnetic properties for the case 1 is essentially greater than for the case 2. Complex effect of thermomagnetic and thermomechanical treatments on magnetic properties was studied in the above-mentioned nanocrystalline alloy as well as in the amorphous alloy Fe5Co70.6Si15B9.4., During the annealings both field and stress were aligned with the long side of the specimens. It was shown that the magnetic field, AC or DC, decreases an effect of loading. Moreover, the magnetic field, AC or DC, applied after stress-annealing can destroy the magnetic anisotropy already induced under load.
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Allan, Adam M., Anthony C. Clark, Tiziana Vanorio, Waruntorn Kanitpanyacharoen, and Hans-Rudolf Wenk. "On the evolution of the elastic properties of organic-rich shale upon pyrolysis-induced thermal maturation." GEOPHYSICS 81, no. 3 (May 2016): D263—D281. http://dx.doi.org/10.1190/geo2015-0514.1.
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The evolution of the elastic properties of organic-rich shale as a function of thermal maturity remains poorly constrained. This understanding is pivotal to the characterization of source rocks and unconventional reservoirs. To better constrain the evolution of the elastic properties and microstructure of organic-rich shale, we have studied the acoustic velocities and elastic anisotropy of samples from two microstructurally different organic-rich shales before and after pyrolysis-induced thermal maturation. To more physically imitate in situ thermal maturation, we performed the pyrolysis experiments on intact core plugs under applied reservoir-magnitude confining pressures. Iterative characterization of the elastic properties of a clay-rich, laminar Barnett Shale sample documents the development of subparallel to bedding cracks by an increase in velocity sensitivity to pressure perpendicular to the bedding. These cracks, however, are not visible through time-lapse scanning electron microscope imaging, indicating either submicrometer crack apertures or predominant development within the core of the sample. At elevated confining pressures, in the absence of pore pressure, these induced cracks close, at which point, the sample is acoustically indistinguishable from the prepyrolysis sample. Conversely, a micritic Green River sample does not exhibit the formation of aligned compliant features. Rather, the sample exhibits a largely directionally independent decrease in velocity as load-bearing, pore-filling kerogen is removed from the sample. Due to the weak alignment of minerals, there is comparatively little intrinsic anisotropy; further, due to the relatively directionally independent evolution of velocity, the evolution of the anisotropy as a function of thermal maturity is not indicative of aligned compliant features. Our results have indicated that horizons of greater thermal maturity may be acoustically detectable in situ through increases in the elastic anisotropy of laminar shales or decreases in the acoustic velocities of nonlaminar shales, micritic rocks, or siltstones.
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Lin, P., Z. x. Li, A. Garg, and J. S. Yadav. "Simplified analyses of stress induced anisotropy in remolded soft clay under undrained conditions." Archives of Materials Science and Engineering 2, no. 105 (October 1, 2020): 56–64. http://dx.doi.org/10.5604/01.3001.0014.5762.
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Purpose: The soil’s anisotropy induced by stress (i.e. stress induced anisotropy) has an important effect on the behavior of soil. This paper focuses on analyzing the anisotropy of remolded Shantou soft clay under compression stress path. Design/methodology/approach: Experiments were executed by using three axle experimental instruments. The data obtained from the plain strain tests were analyzed and the relationship between stress and strain was calculated by using the modified Duncan- Chang and Lade-Duncan models. The models were modified under the condition of plain strain and cohesion. Findings: It was concluded that in complex stress path conditions, the conventional triaxial tests may not fully reflect the actual stress of soil and its response in the Duncan-Chang and Lade-Duncan models. Research limitations/implications: The formulation of Mohr-Coulomb failure criterion in the plasticity framework is quite diffcult. As a result, dilatancy cannot be described. The properties of soil in unload or drained conditions remain to be part of further investigated. Practical implications: Based upon the two stiffness parameters, the modified Duncan- Chang model has captured the soil behaviour in a very conformable way and is recommened for practical modeling. These constitutive models of soil are widely used in the numerical analyses of soil structure such as embankments. Originality/value: Duncan-Chang and Lade-Duncan models widely used in engineering practices are modes based on conventional triaxial cases. Both models have have some inherent limitations to represent the stress-strain characteristics of soils, such as shear-induced dilatancy and stress path dependency and required corrections. In this investigation, the tests are carried out in undrained conditions. It is related to the properties of soil in load conditions.
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Hu, Shaohua, Jianxin Chen, Ben Fabry, Yasushi Numaguchi, Andrew Gouldstone, Donald E. Ingber, Jeffrey J. Fredberg, James P. Butler, and Ning Wang. "Intracellular stress tomography reveals stress focusing and structural anisotropy in cytoskeleton of living cells." American Journal of Physiology-Cell Physiology 285, no. 5 (November 2003): C1082—C1090. http://dx.doi.org/10.1152/ajpcell.00159.2003.
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We describe a novel synchronous detection approach to map the transmission of mechanical stresses within the cytoplasm of an adherent cell. Using fluorescent protein-labeled mitochondria or cytoskeletal components as fiducial markers, we measured displacements and computed stresses in the cytoskeleton of a living cell plated on extracellular matrix molecules that arise in response to a small, external localized oscillatory load applied to transmembrane receptors on the apical cell surface. Induced synchronous displacements, stresses, and phase lags were found to be concentrated at sites quite remote from the localized load and were modulated by the preexisting tensile stress (prestress) in the cytoskeleton. Stresses applied at the apical surface also resulted in displacements of focal adhesion sites at the cell base. Cytoskeletal anisotropy was revealed by differential phase lags in X vs. Y directions. Displacements and stresses in the cytoskeleton of a cell plated on poly-l-lysine decayed quickly and were not concentrated at remote sites. These data indicate that mechanical forces are transferred across discrete cytoskeletal elements over long distances through the cytoplasm in the living adherent cell.
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Zhou, Jiangcun, Ernian Pan, and Michael Bevis. "Deformation due to surface temperature variation on a spherically layered, transversely isotropic and self-gravitating Earth." Geophysical Journal International 225, no. 3 (February 10, 2021): 1672–88. http://dx.doi.org/10.1093/gji/ggab056.
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SUMMARY We present a theory of modern, thermally induced deformation in a realistic Earth. The heat conduction equation is coupled with standard elastic deformation theory to construct a boundary-value problem comprised of eighth-order differential equations. The accurate and stable dual variable and position propagating matrix technique is introduced to solve the boundary-value problem. The thermal load Love numbers are defined to describe the displacements and potential changes driven by thermally induced deformation. The proposed analytical method is validated by comparing the present results with exact solutions for a homogeneous sphere, which are also derived in this paper. The analytical method is then applied to a realistic Earth model to evaluate the effects of layering and self-gravitation of the Earth on displacement and changes of potential. Furthermore, the frequency dependence in the thermal load is illustrated by invoking different thermal periodicities in the computation. Thermal anisotropy is also considered by comparing the results obtained using isotropic and transversely isotropic Earth models. Results show that, when simulating thermally induced deformation, invoking a homogeneous spherical Earth leads to results that substantially differ from those obtained using a more realistic Earth model.
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Neslušan, Miroslav, Jana Šugárová, Petr Haušild, Peter Minárik, Jiří Čapek, Michal Jambor, and Peter Šugár. "Barkhausen Noise Emission in AISI 321 Austenitic Steel Originating from the Strain-Induced Martensite Transformation." Metals 11, no. 3 (March 5, 2021): 429. http://dx.doi.org/10.3390/met11030429.
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This paper investigates the sensitivity of the Barkhausen noise technique against strain-induced martensite in AISI 321 austenitic stainless steel. Martensite transformation was induced by the uniaxial tensile test, and a variable martensite fraction was obtained at different plastic strains. It was found that Barkhausen noise emission progressively increases with plastic straining, while its evolution is driven by the martensite fraction in the deformed matrix. This study also demonstrates that the uniaxial tensile stressing produced a certain level of stress and magnetic anisotropy in the samples. The number of strong Barkhausen pulses increased for more developed strains, whereas the position of the Barkhausen noise envelope remained less affected. This study clearly demonstrates the good sensitivity of the Barkhausen noise technique against the degree of martensite transformation in austenitic stainless steel. Moreover, this technique is sensitive to the direction of the exerted load.
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Gong, Xiaobo, Fang Xie, Liwu Liu, Yanju Liu, and Jinsong Leng. "Electro-active Variable-Stiffness Corrugated Structure Based on Shape-Memory Polymer Composite." Polymers 12, no. 2 (February 8, 2020): 387. http://dx.doi.org/10.3390/polym12020387.
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Shape-memory polymers (SMPs) can adjust their stiffness, lock a temporary shape, and recover the permanent shape upon an appropriate stimulus. They are applied in the field of morphing skins. This work presents a variable-stiffness corrugated sheet based on a carbon fiber felt (CFF)-reinforced epoxy-based SMP composite that shows variable stiffness and extreme mechanical anisotropy for potential morphing skin applications. The corrugated sheet exhibits a variable stiffness with a change in temperature, which can help the skin adjust its stiffness according to different service environments. The corrugated sheet can be electrically heated rapidly and homogeneously due to its high electrical conductivity and enhanced heat transfer efficiency. Its Joule-heating effect acts as an effective active stimulation of the variable stiffness and shape-memory effect. The CFF-reinforced epoxy-based SMP composite was manufactured into a corrugated shape to obtain extreme mechanical anisotropy. The corrugated sheet shows a low in-plane stiffness to minimize the actuation energy, while it also possesses high out-of-plane stiffness to transfer the aerodynamic pressure load. Its mechanical properties, electrical heating performance, and shape-memory effect were investigated using experiments. The results show that the proposed SMP composite exhibits extreme mechanical anisotropy, considerable deformation ability, and variable stiffness induced by Joule heating without an external heater.
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Shapiro, Serge A., and Axel Kaselow. "Porosity and elastic anisotropy of rocks under tectonic stress and pore-pressure changes." GEOPHYSICS 70, no. 5 (September 2005): N27—N38. http://dx.doi.org/10.1190/1.2073884.
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Elastic properties of rocks depend on tectonic stress. Using the theory of poroelasticity as a constraint, we analyze features of these dependencies related to changes in rock pore-space geometry. We develop a formalism describing elastic moduli and anisotropy of rocks as nonlinear functions of confining stress and pore pressure. This formalism appears to agree with laboratory observations. To a first approximation, elastic moduli and seismic velocities as well as porosity depend only on the difference between the confining tectonic stress and pore pressure. However, in general, both the confining stress tensor and the pore pressure must be taken into account as independent variables. The stress-dependent geometry of the pore space fully controls the stress-induced changes in elastic moduli and seismic velocities. Specifically, the compliant porosity plays the most important role, despite the fact that in many rocks the compliant porosity is a very small part of total porosity. Changes in compliant porosity with pressure and stress explain the often observed behavior of elastic moduli: in the low compressive stress regime — say, below 50 to 100 MPa — moduli increase rapidly and then taper exponentially into a flat and linear increase with increasing load. Taking into account the strain of the compliant pore space, we introduce a tensor quantity defining the sensitivity of elastic moduli of rocks to the difference between confining stress and pore pressure. We call it the stress sensitivity tensor. This tensor is an important physical characteristic directly related to elastic nonlinearity of rocks. The stress sensitivity tensor governs the changes in elastic anisotropy of a drained poroelastic system as it depends upon the applied load.
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Kim, Dong Uk, Seong Gyoon Kim, Won Tae Kim, Jae Hyung Cho, Heung Nam Han, and Pil Ryung Cha. "Effect of Micro-Elasticity on Grain Growth and Texture Evolution: A Phase Field Study." Materials Science Forum 654-656 (June 2010): 1590–93. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.1590.
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In this presentation, a novel phase field grain growth model combined with a micro-elasticity effect including elastic anisotropy and inhomogeity is presented to demonstrate the effect of micro-elasticity on grain growth and texture evolution. We report on texture evolution and abnormal grain growth induced by external elastic load from the viewpoint of micro-elasticity and first demonstrate that the previous mechanism (macroscopic viewpoint) on the effect of external elastic load on grain growth does not work in strain-controlled system. In contrast to the macro-elastic descriptions, strong localization of strain energy density and inhomogeneous distribution even inside grains are observed. Moreover, elastically soft grains with a higher strain energy density grow at the expense of the elastically hard grains to reduce the total strain energy. It is observed that strong <100>//ND fiber texture was developed in poly-crystalline Cu with initial random texture by biaxial external strain while <111>//ND fiber texture evolved in biaxial external stress condition. Even, grain growth of <100>//ND textured grains is occurred as abnormal grain growth when <100>//ND textured grains are surrounded by <111>//ND fiber textured grains.
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VREMAN, A. W. "Turbulence characteristics of particle-laden pipe flow." Journal of Fluid Mechanics 584 (July 25, 2007): 235–79. http://dx.doi.org/10.1017/s0022112007006556.
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Turbulence characteristics of vertical air–solid pipe flow are investigated in this paper. Direct numerical simulations of the gas phase have been performed, while the solid particles have been simulated by a Lagrangian approach, including particle collisions. The modelling of wall roughness is shown to be important to obtain agreement with experimental data. Reynolds stresses and Reynolds stress budgets are given for both phases and for a wide range of solid–air mass load ratios (mass loads), varying from 0.11 to 30. Air turbulence intensities, Reynolds shear stress, and turbulence production reduce with increasing mass load. The mean air profile does not alter for low mass loads. In this regime, a simple theory predicts that the reduction of air turbulent production relative to unladen turbulent production is approximately equal to the mass load ratio. The insight that the solids Reynolds shear stress can be significant, even for low mass loads, is essential for this explanation. It is shown that at least two mechanisms cause the turbulence reduction. In addition to the classically recognized mechanism of dissipation of turbulent fluctuations by particles, there is another suppressing mechanism in inhomogeneous flows: the non-uniform relative velocity of the phases, created because particles slip at the wall, collide, and slowly react with the continuous phase. Investigation of the air turbulent kinetic energy equation demonstrates that the relative reduction of air pressure strain is larger than the reduction of turbulent production and dissipation, and pressure strain may therefore be a cause of the reduction of the other quantities. The fluctuational dissipation induced by the drag forces from particles is small compared to the other terms, but not negligible. For intermediate and high mass loads the air turbulence remains low. The relatively small turbulence intensities are not generated by the standard turbulent mechanisms any more, but directly caused by the particle motions. The particle–fluid interaction term in the turbulent kinetic energy equation is no longer dissipative, but productive instead. On increasing the mass load, the radial and azimuthal fluctuations of the particles grow. The corresponding reduction of solids anisotropy is an effect of the inter-particle collisions, which act as a solids pressure strain term. For intermediate and high mass loads, fluctuational drag force and particle collisions appear to be the relevant dissipation mechanisms in the solids fluctuational energy equation. In contrast to the air turbulent production, the solids ‘turbulent’ production term has the same level for low and high mass loads, while it attains a clear local minimum between. With increasing mass load, large-scale coherent turbulent fluid structures weaken, and eventually disappear. Simultaneously, the fluid fluctuations at relatively small length scales are enhanced by the motion of the particles. The highest particle concentration occurs near the wall for low mass loads, but on increasing the mass load, the concentration profile becomes uniform, while for the highest mass load particles accumulate in the centre of the pipe. Two-point correlation functions indicate that the addition of a small number of small solid particles to a clean pipe flow increases the streamwise length scale of the turbulence.
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Lee, Seunghyun, and Matt Pharr. "Sideways and stable crack propagation in a silicone elastomer." Proceedings of the National Academy of Sciences 116, no. 19 (April 19, 2019): 9251–56. http://dx.doi.org/10.1073/pnas.1820424116.
Full textAbstract:
We have discovered a peculiar form of fracture that occurs in a highly stretchable silicone elastomer (Smooth-On Ecoflex 00–30). Under certain conditions, cracks propagate in a direction perpendicular to the initial precut and in the direction of the applied load. In other words, the crack deviates from the standard trajectory and instead propagates perpendicular to that trajectory. The crack arrests stably, and thus the material ahead of the crack front continues to sustain load, thereby enabling enormous stretchabilities. We call this phenomenon “sideways” and stable cracking. To explain this behavior, we first perform finite-element simulations that demonstrate a propensity for sideways cracking, even in an isotropic material. The simulations also highlight the importance of crack-tip blunting on the formation of sideways cracks. Next, we provide a hypothesis on the origin of sideways cracking that relates to microstructural anisotropy (in a nominally isotropic elastomer). To substantiate this hypothesis, we transversely prestretch samples to various extents before fracture testing, as to determine the influence of microstructural arrangement (chain alignment and strain-induced crystallization) on fracture energy. We also perform microstructural characterization that indicates that significant chain alignment and strain-induced crystallization indeed occur in this material upon stretching. We conclude by characterizing how a number of loading conditions, such as sample geometry and strain rate, affect this phenomenon. Overall, this paper provides fundamental mechanical insight into basic phenomena associated with fracture of elastomers.
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Hopmann, Ch, and C. Zimmermann. "Characterisation of the quasi-static material behaviour of thermoplastic elastomers (TPE) under consideration of temperature and stress state." Journal of Elastomers & Plastics 52, no. 3 (March 21, 2019): 199–215. http://dx.doi.org/10.1177/0095244319835868.
Full textAbstract:
This article deals with the determination of the mechanical material behaviour of injection-moulded thermoplastic elastomers (TPE). For this purpose, the mechanical behaviour of TPE is investigated on basis of different materials (type and hardness) and process parameters with regard to the process-induced anisotropy. Based on these investigations, an almost isotropic material was selected for the investigations about the influence of temperature, stress state and load level. The results confirm that the hardness of the material and type of the processed material have an impact on the mechanical properties longitudinal and transversal to the flow direction. Furthermore, TPE behave quite similar to pure elastomers, as they showed a non-linear material behaviour, a stress softening after initial loading and a residual deformation after unloading. All these effects also depend on the temperature, stress state and load level, which results in a complex material behaviour. At the end of the article, two calibration approaches of a hyperelastic material model were shown (one set of parameters for all stress states vs. one set of parameters for each stress state). The second approach (one set of parameters for each stress state) shows a much higher accuracy in approximation of the test results.
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Huang, Hui, Jie Lian, Jiaxing Li, Bin Jia, Dong Meng, and Zhizhong Wu. "Design and Evaluation of a New Resin-Filled GFRP Pipe Connection System for Butt Splicing of FRP Bars." Materials 14, no. 1 (December 31, 2020): 161. http://dx.doi.org/10.3390/ma14010161.
Full textAbstract:
Fiber-reinforced polymer (FRP) bars are one of the promising alternatives for steel bars used in concrete structures under corrosion or non-magnetic environments due to the unique physical properties of FRP materials. When compared with steel bars, FRP bars are difficult to be spliced in field application due to their anisotropy and low shear and compressive strengths. In view of this, the paper presents a new non-metallic connection system (i.e., resin-filled glass fiber-reinforced polymer (GFRP) pipe connection system) for the butt splicing of FRP bars. With the proposed connection system and a simplified trilinear interfacial bond-slip model, a set of design formulas were derived based on the requirement that the proposed connection system should provide a load transfer capacity beyond the tensile capacity of the spliced FRP bars (i.e., to fulfill the high tensile strength of FRP materials). Besides, considering the fabrication error-induced load transfer capacity reduction of the connection system in field application, a correction factor was introduced in the paper to compensate for the reduced load transfer capacity by increasing the FRP bar anchorage length. At last, to estimate the effectiveness of the proposed connection system and the derived design formulas, nine specimens were fabricated with a kind of commercially available basalt fiber-reinforced polymer (BFRP) bars and the designed connection system and tested under unidirectional tension to study their tensile performance. With the comparison between the tested and theoretical results, the effectiveness of the proposed connection system and the derived design formulas are verified.
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Qiang, He, Nie Jingkai, Zhang Songyang, Xiao Weimin, Ji Shengchang, and Chen Xin. "Study of Transformer Core Vibration and Noise Generation Mechanism Induced by Magnetostriction of Grain-Oriented Silicon Steel Sheet." Shock and Vibration 2021 (May 3, 2021): 1–15. http://dx.doi.org/10.1155/2021/8850780.
Full textAbstract:
The problem of vibration and noise in the iron core of power transformers remains quite topical. Insofar as the state-of-the-art iron core and binding production adopt the lamination method and weft-free adhesive tape, respectively, the transformer core vibration is mainly attributed to the silicon steel sheet (SSS) magnetostriction. In this paper, based on the magnetostriction of grain-oriented SSS, an in-depth analysis of the vibration generation mechanism in the transformer core was performed. The SSS microstructure was observed, its magnetostrictive properties at different magnetic flux densities were tested, and a core-simulating four-corner iron core model was constructed to analyze the vibration characteristics. Modal, vibration, and noise tests were performed on an actual 110 kV transformer core under no-load conditions. The results show that the core vibration is related to SSS’s deformation mechanism. The vibration magnitude in different core parts varies due to the magnetostriction anisotropy. The vibration in vertical to the core plane is the largest, and its magnitude in the core center is lower than those at the seams in the same plane. The core vibration and noise exhibit a significant correlation, while modal characteristics strongly influence the core vibration and noise intensity.
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Wong, R. C. K., W. E. Barr, and P. R. Kry. "Stress–strain response of Cold Lake oil sands." Canadian Geotechnical Journal 30, no. 2 (April 1, 1993): 220–35. http://dx.doi.org/10.1139/t93-019.
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The stress–strain response of Cold Lake oil sands at confining stresses and temperatures up to 18 MPa and 200 °C, respectively, was studied in a triaxial apparatus using 89-mm full diameter cores. Tests that have been performed include conventional triaxial tests such as hydrostatic compression, initial Young's modulus determination, and cyclic drained and undrained compression. Tests involving pore-pressure increase and decrease under constant total stresses were also performed to simulate the stress path encountered in the field during the cyclic steam stimulation process. Treating oil sand as a particulate medium, possible modes of granular interaction were explored for all tests along different stress paths. Four modes of granular interaction were identified: (i) contact elastic deformation, (ii) rolling, (iii) shear dilation, and (iv) crushing. These modes provide a useful framework for explaining the behaviour arising from the effects of variation in void ratio owing to sample disturbance, stress level, stress path, induced anisotropy, and temperature. Other behaviour relating to critical state, localized shear deformation, and load–unload–reload are also examined. Key words : oil sand, stress, strain, void ratio, pore pressure, temperature, mode of granular interaction, critical state.
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Groh, R. M. J., and P. M. Weaver. "Deleterious localized stress fields: the effects of boundaries and stiffness tailoring in anisotropic laminated plates." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, no. 2194 (October 2016): 20160391. http://dx.doi.org/10.1098/rspa.2016.0391.
Full textAbstract:
The safe design of primary load-bearing structures requires accurate prediction of stresses, especially in the vicinity of geometric discontinuities where deleterious three-dimensional stress fields can be induced. Even for thin-walled structures significant through-thickness stresses arise at edges and boundaries, and this is especially precarious for laminates of advanced fibre-reinforced composites because through-thickness stresses are the predominant drivers in delamination failure. Here, we use a higher-order equivalent single-layer model derived from the Hellinger–Reissner mixed variational principle to examine boundary layer effects in laminated plates comprising constant-stiffness and variable-stiffness laminae and deforming statically in cylindrical bending. The results show that zigzag deformations, which arise due to layerwise differences in the transverse shear moduli, drive boundary layers towards clamped edges and are therefore critically important in quantifying localized stress gradients. The relative significance of the boundary layer scales with the degree of layerwise anisotropy and the thickness to characteristic length ratio. Finally, we demonstrate that the phenomenon of alternating positive and negative transverse shearing deformation through the thickness of composite laminates, previously only observed at clamped boundaries, can also occur at other locations as a result of smoothly varying the material properties over the in-plane dimensions of the laminate.
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Tralli, A., C. Alessandri, and G. Milani. "Computational Methods for Masonry Vaults: A Review of Recent Results." Open Civil Engineering Journal 8, no. 1 (October 29, 2014): 272–87. http://dx.doi.org/10.2174/1874149501408010272.
Full textAbstract:
The present paper makes a critical review of some methods and models, now available in the technical litera-ture and commonly used in the analysis of masonry vaults up to their collapse, by highlighting advantages and drawbacks of each approach. All methods adopted to describe the mechanical behavior of masonry structures, in order to be reliable, must take into account the distinctive aspects of masonry, namely the scarce (or zero) tensile strength, the good resistance in compression and the occurrence of failure mechanisms through rotation-translation of rigid macro-blocks. Classic no-tension material models disregard the small existing tensile strength and make the assumption of (1) infinitely elastic be-havior in compression and (2) isotropy, giving thus the possibility to deal with either semi-analytical approaches (espe-cially for arches) or robust numerical procedures. More advanced but rather complex models are nowadays able to deal al-so with anisotropy induced by texture, small tensile strength and softening in tension, as well as by finite strength in com-pression. Traditionally – and nowadays it is still an opinion commonly accepted, in contrast with step by step complex procedures, Limit Analysis has proved to be the most effective Method for a fast and reliable evaluation of the load bear-ing capacity of vaulted masonry structures: classic lower and upper bound theorems recall respectively the concepts of equilibrium and occurrence of failure mechanisms with rigid elements. The so-called Thrust Network Method moves its steps from lower bound theorems, whereas FE limit analysis approaches with infinitely resistant elements and dissipation on interfaces take inspiration from the upper bound point of view. An alternative to Limit Analysis is represented by tradi-tional FEM combined with either elastic-plastic or damaging models with softening, commonly used for other materials but recently adapted also to masonry. They are able to provide a large set of output numerical information but further studies are still needed to ensure their proper application.
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Gualtieri, P., F. Picano, G. Sardina, and C. M. Casciola. "Clustering and turbulence modulation in particle-laden shear flows." Journal of Fluid Mechanics 715 (January 9, 2013): 134–62. http://dx.doi.org/10.1017/jfm.2012.503.
Full textAbstract:
AbstractTurbulent fluctuations induce the common phenomenon known as clustering in the spatial arrangement of small inertial particles transported by the fluid. Particles spread non-uniformly, and form clusters where their local concentration is much higher than in nearby rarefaction regions. The underlying physics has been exhaustively analysed in the so-called one-way coupling regime, i.e. negligible back-reaction of the particles on the fluid, where the mean flow anisotropy induces preferential orientation of the clusters. Turbulent transport in suspensions with significant mass in the disperse phase, i.e. particles back-reacting in the carrier phase (the two-way coupling regime), has instead been much less investigated and is still poorly understood. The issue is discussed here by addressing direct numerical simulations of particle-laden homogeneous shear flows in the two-way coupling regime. Consistent with previous findings, we observe an overall depletion of the turbulent fluctuations for particles with response time of the order of the Kolmogorov time scale. The depletion occurs in the energy-containing range, while augmentation is observed in the small-scale range down to the dissipative scales. Increasing the mass load results in substantial broadening of the energy cospectrum, thereby extending the range of scales driven by anisotropic production mechanisms. As discussed throughout the paper, this is due to the clusters which form the spatial support of the back-reaction field and give rise to a highly anisotropic forcing, active down to the smallest scales. A certain impact on two-phase flow turbulence modelling is expected from the above conclusions, since the frequently assumed small-scale isotropy is poorly recovered when the coupling between the phases becomes significant.
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Arrasmith, S. R., M. J. Kramer, B. D. Merkle, T. G. Holesinger, and R. W. McCallum. "Rapidly texturedBi2Sr2CaCu2O8." Journal of Materials Research 8, no. 6 (June 1993): 1247–57. http://dx.doi.org/10.1557/jmr.1993.1247.
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Amorphous Bi2Sr2CaCu2O8 (Bi-2212) was crystallized under uniaxial loads (up to 1500 N) at temperatures up to 890 °C to induce texture. Well-textured samples (19 mm in diameter and 0.15 mm thick) were obtained for samples heated to 890 °C and quenched. Heated (10 °C/min) and quenched samples at 550, 750, 850, and 870 °C demonstrate that the crystallization path is Bi2Sr2CuO6 (Bi-2201) (550 °C) to Bi-2212 (850 °C), with texturing occurring during grain growth (T > 850 °C). Comparison of samples crystallized under load and no load demonstrates that the texturing is a result of the plane stress biasing the normal anisotropic grain growth normal to the applied stress direction.
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Fang, Yong, Zhigang Yao, Gabriel Walton, Jian Zhou, Wanghao Xu, and Yuchao Zheng. "Evaluating the Impact of Blast-Induced Damage on the Rock Load Supported by Liner in Construction of a Deep Shaft: A Case Study of Ventilation Shaft of Micangshan Road Tunnel Project." Advances in Civil Engineering 2020 (January 29, 2020): 1–19. http://dx.doi.org/10.1155/2020/9068345.
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The rock load acting on the lining of an underground excavation is influenced by multiple factors, including rock type, rock mass condition, depth, and construction method. This study focuses on quantifying the magnitude and distribution of the radial loads on the lining of a deep shaft constructed in hard rock by the so-called short-step method. The blasting-induced damage zone (BDZ) around the shaft was characterized using ultrasonic testing and incorporated into the convergence-confinement method (CCM) and 3D numerical analyses to assess the impact of BDZ on rock loading against the liner. The results show that excavation blasting of shafts is an important controlling factor for the degradation of the rock mass, while the orientation and magnitude of the principal stress had a minimal influence on the distribution of blast-induced damage. The analysis shows that increasing the depth of blast damage in the walls can increase the loads acting on the lining, and the shear loads acting on the liner could be significant for shafts sunk by the short-step method in an area with anisotropic in situ stresses.
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Tutumluer, Erol, and Marshall R. Thompson. "Anisotropic Modeling of Granular Bases in Flexible Pavements." Transportation Research Record: Journal of the Transportation Research Board 1577, no. 1 (January 1997): 18–26. http://dx.doi.org/10.3141/1577-03.
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A new cross-anisotropic model is proposed to predict the performance of granular bases in flexible pavements. A cross-anisotropic representation has different material properties (i.e., elastic modulus and Poisson’s ratio) assigned in the horizontal and vertical directions. Repeated-load triaxial tests with vertical and lateral deformation measurements can be used to establish these anisotropic properties. Simple stress-dependent granular material models, obtained from analysis of the laboratory test data, are used in a nonlinear finite element program, named GT-PAVE, to predict pavement responses. The horizontal and shear stiffnesses are typically found to be less than the vertical. The nonlinear anisotropic approach is shown to account effectively for the dilative behavior observed under the wheel load and the effects of compaction-induced residual stresses. The main advantage of using a cross-anisotropic model in the base is the drastic reduction or elimination of significant tensile stresses generally predicted by isotropic linear elastic layered programs.
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Mohd Zawawi, Fazila, Peng Lv, Sebastien Prothin, Joseph Morlier, Emmanuel Benard, and Jean Marc Moschetta. "Performance Enhancement of Tilt-Body Micro Air Vehicle by Use of Orthotropic Laminated Proprotors." Applied Mechanics and Materials 819 (January 2016): 585–90. http://dx.doi.org/10.4028/www.scientific.net/amm.819.585.
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A passive twist control is considered as an adaptive way to maximize the overall efficiency of a proprotor developed for convertible Micro Air Vehicles (MAV). In this paper, adaptation of the proprotor geometry in accordance to flight configurations is achieved by induced twist generated by the inherent structural coupling effect in anisotropic composite material and centrifugal force emanating from the tip load. Beam Finite Element Model based on Rotating Timoshenko Theory is used to predict structural loads, while Blade Element Momentum Theory is employed to predict the aerodynamic performance of adaptive proprotor as applied on Micro Air Vehicles (MAV). The iterative process of combination of aerodynamic model and structural model is used to compute the steady-state deformation of the flexible laminated proprotor blade due aerodynamic loads. Finally, the optimal design of lamina blade material is carried out to investigate the potential of flexible blade in the proprotorperformance enhancement.
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Go´mez-Benito, M. J., J. M. Garcı´a-Aznar, and M. Doblare´. "Finite Element Prediction of Proximal Femoral Fracture Patterns Under Different Loads." Journal of Biomechanical Engineering 127, no. 1 (February 1, 2005): 9–14. http://dx.doi.org/10.1115/1.1835347.
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The main purpose of this work is to discuss the ability of finite element analyses, together with an appropriate anisotropic fracture criterion, to predict the ultimate load and type of fracture in bones and more specifically in the proximal femur. We show here that the use of a three-dimensional anisotropic criterion provides better results than other well-known isotropic criteria. The criterion parameters and the anisotropic elastic properties were defined in terms of the bone tissue microstructure, quantified by the apparent density and the so-called “fabric tensor”, whose spatial distributions were obtained by means of an anisotropic remodeling model able to capture the main features of the internal structure of long bones. In order to check the validity of the results obtained, they have been compared with those of an experimental work that analyzes different types of fractures induced in the proximal femur by a static overload.
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Le Bourhis, E., G. Patriarche, L. Largeau, and J. P. Rivière. "Polarity-induced changes in the nanoindentation response of GaAs." Journal of Materials Research 19, no. 1 (January 2004): 131–36. http://dx.doi.org/10.1557/jmr.2004.19.1.131.
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We studied the polarity-induced changes in the nanoindentation response of GaAs{111}. The nanoindentations were made under a large range of loads (Fmax between 0.2 mN and 50 mN) at room temperature on {111} faces of A (Ga) or B (As) character. The loading–unloading curves were compared first, with special attention addressed to pop-in events and hardness values (reported previously for microindentation). Transmission electron microscopy was used to observe the nanoindentation structures generated at the two polar surfaces. The size of the dense plastic zone generated around the indent site was found to increase linearly with √Fmax and similarly for both polar surfaces. The indentation rosettes possess a threefold symmetry with arms developed along the <110> directions parallel to the surface. Sizes were found to be very close for both polar surfaces and the entire load range. For an A-polar face, the rosette arms are constituted by two arms: a long arm (LA, α dislocations) and a short arm (β dislocations). At the B surface, only the LA (β dislocations) are formed. Furthermore, microtwinning was observed only for an A-polar face, similar to previous observations of anisotropic microtwinning at GaAs(001) surfaces.
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Bouzakis, Konstantinos D., G. Skordaris, Emmanouil Bouzakis, and Eleftheria Lili. "Determination of the Effective Film Mechanical Properties in the Impact Test Imprint of Coated Specimens." Key Engineering Materials 438 (May 2010): 131–38. http://dx.doi.org/10.4028/www.scientific.net/kem.438.131.
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If the film of a coated component deforms plastically because of operational loads, residual stresses are developed in the coating material after the load removal. In this way, material mechanical properties changes occur due to endogenous reasons i.e. induced by the coating crystalline structure plastic deformation. In this case, the determination of the effective film mechanical properties has been introduced in a recent publication [1]. Moreover, if the loading conditions lead only to a substrate plastic deformation, the coating remains elastically deformed during the relaxation, due to the substrate residual stresses. Thus, the associated material mechanical properties changes are caused by exogenous parameters related to the permanent substrate deformation. In the present paper, a novel experimental-analytical method based on FEM calculations is introduced to determine the effective film mechanical properties when the coating is stressed elastically due to a plastic substrate deformation. The perpendicular impact test is a convenient experimental procedure to investigate such an effect because under appropriate loading conditions, the substrate deforms plastically and the coating elastically. The pristine constitutive law of the applied PVD film was determined by nanoindentation and FEM supported results evaluation. Impact tests were conducted at various loads and loading cycles. The impact test was simulated by a two dimensional FEM model. Additionally, the developed elastic residual stress fields in the coating and the plastic ones of the substrate in the imprint were determined. In these calculations, a rate-independent anisotropic plasticity with kinematic hardening material law was considered and the film as an anisotropic material with variable mechanical properties in three main directions. Finally, by a FEM supported simulation of the nanoindention, the coating’s load-displacement behaviour in various areas of the impact imprint were predicted and the effective coating mechanical properties as well.
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Liou, J. Y., and J. C. Sung. "Supersonic responses induced by point load moving steadily on an anisotropic half-plane." International Journal of Solids and Structures 49, no. 17 (September 2012): 2254–72. http://dx.doi.org/10.1016/j.ijsolstr.2012.04.024.
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Tong, Van-Canh, and Seong-Wook Hong. "The effect of angular misalignment on the stiffness characteristics of tapered roller bearings." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 231, no. 4 (August 9, 2016): 712–27. http://dx.doi.org/10.1177/0954406215621098.
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The effect of angular misalignment between inner and outer raceways on the stiffness characteristics of tapered roller bearings (TRBs) is investigated. A computational procedure is introduced to solve the equations of TRB in the presence of angular misalignment. A dynamic analysis of a spindle supported by TRBs is also performed to investigate the natural frequency behavior by the stiffness variation due to angular misalignment. An extensive simulation demonstrates the effect of angular misalignment on the TRB characteristics such as roller–raceway contact loads, radial and axial displacements, and induced moment load. Computational results show that angular misalignment alters TRB stiffness characteristics and results in the splitting of the spindle natural frequencies by inducing anisotropic behavior of the TRBs. The proposed model and computational procedure are effective in estimating TRB characteristics and thus would aid in selecting TRBs or determining TRB loading conditions in practical applications.
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Campos-Silva, Ivan, N. López-Perrusquia, E. Hernández-Sánchez, M. Ortíz-Domínguez, D. Bravo-Bárcenas, and José Martínez-Trinidad. "Anisotropy of Boride Layers: Effect on the Mechanical Properties of AISI 4140 Borided Steels." Defect and Diffusion Forum 297-301 (April 2010): 142–47. http://dx.doi.org/10.4028/www.scientific.net/ddf.297-301.142.
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The growth of iron borides over the surface of different steels is of high anisotropy. It was determined that the anisotropy of borided phases reveals a significant instability of properties in service. One of the techniques to determine the effect of anisotropy on the mechanical properties of boride layers is the induced-fracture by Vickers microindentation. During the present work, the fracture toughness (KC) of the Fe2B hard coatings has been estimated at the surface of AISI 4140 borided steels. The force criterion of fracture toughness was determined from the extent of brittle cracks originating at the tips of an indenter impression. The indentation loads were established between 1.9 to 9.8 N at three different distances from the borided surface. The KC values were expressed as a function of temperature, treatment time and the indentation distances from the surface. Likewise, the adherence of the coated system was evaluated by Rockwell-C indentation, where the borided steel showed sufficient adhesion.
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Dornowski, W., and P. Perzyna. "Constitutive Modeling of Inelastic Solids for Plastic Flow Processes Under Cyclic Dynamic Loadings." Journal of Engineering Materials and Technology 121, no. 2 (April 1, 1999): 210–20. http://dx.doi.org/10.1115/1.2812368.
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The main objective of the paper is the description of the behavior and fatigue damage of inelastic solids in plastic flow processes under dynamic cyclic loadings. Experimental motivations and physical foundations are given. Recent experimental observations for cycle fatigue damage mechanics at high temperature of metals suggest that the intrinsic microdamage process does very much depend on the strain rate effects as well as on the wave shape effects. The microdamage process has been treated as a sequence of nucleation, growth and coalescence of microcracks. The microdamage kinetics interacts with thermal and load changes to make failure of solids a highly rate, temperature and history dependent, nonlinear process. A general constitutive model of elasto-viscoplastic damaged polycrystalline solids is developed within the thermodynamic framework of the rate type covariance structure with finite set of the internal state variables. A set of the internal state variables is assumed and interpreted such that the theory developed takes account of the effects as follows: (i) plastic non-normality; (ii) plastic strain induced anisotropy (kinematic hardening); (iii) softening generated by microdamage mechanisms; (iv) thermomechanical coupling (thermal plastic softening and thermal expansion); (v) rate sensitivity. To describe suitably the time and temperature dependent effects observed experimentally and the accumulation of the plastic deformation and damage during dynamic cyclic loading process the kinetics of microdamage and the kinematic hardening law have been modified. The relaxation time is used as a regularization parameter. By assuming that the relaxation time tends to zero, the rate independent elastic-plastic response can be obtained. The viscoplastic regularization procedure assures the stable integration algorithm by using the finite difference method. Particular attention is focused on the well-posedness of the evolution problem (the initial-boundary value problem) as well as on its numerical solutions. The Lax-Richtmyer equivalence theorem is formulated and conditions under which this theory is valid are examined. Utilizing the finite difference method for regularized elasto-viscoplastic model, the numerical investigation of the three-dimensional dynamic adiabatic deformation in a particular body under cyclic loading condition is presented. Particular examples have been considered, namely, a dynamic, adiabatic and isothermal, cyclic loading processes for a thin steel plate with small rectangular hole located in the centre. Small two regions which undergo significant deformations and temperature rise have been determined. Their evolution until occurrence of final fracture has been simulated. The accumulation of damage and equivalent plastic deformation on each considered cycle has been obtained. It has been found that this accumulation distinctly depends on the wave shape of the assumed loading cycle.
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Chady, Tomasz, and Ryszard Łukaszuk. "Examining Ferromagnetic Materials Subjected to a Static Stress Load Using the Magnetic Method." Materials 14, no. 13 (June 22, 2021): 3455. http://dx.doi.org/10.3390/ma14133455.
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This paper discusses the experimental examination of anisotropic steel-made samples subjected to a static stress load. A nondestructive testing (NDT) measurement system with a transducer, which enables observation of local hysteresis loops and detection of samples’ inhomogeneity, is proposed. Local hysteresis loops are measured on two perpendicular axes, including one parallel to the rolling direction of the samples. The results confirm that the selected features of the local hysteresis loops provide important information about the conditions of ferromagnetic materials. Furthermore, it is shown that the selected parameters of the statistical analysis of the achieved measurements are beneficial for evaluating stress and fatigue changes induced in the material.
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Islam, Rashed Adnan, and Y. C. Chan. "Behavior of Anisotropic Conductive Film (ACF) Joint under Mechanical Shock." Journal of Electronic Packaging 127, no. 4 (February 14, 2005): 375–80. http://dx.doi.org/10.1115/1.2056570.
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The contact resistances investigated by this study of ACF joints using Au∕Ni bumps and flexible substrates are found to be increased by the induced mechanical shock and also by the combined effect of heat/humidity and the mechanical shock. The samples humidified at 85°C/85% RH for 384 h, on which a load of 3.164 Kg was dropped four times from a height of 0.4 m, exhibit the most severe results. The contact resistance increases by 700%, which had been about 62 mΩ in the as-bonded condition. The samples without humidification showed a sluggish and gentle increase in contact resistance with the induced mechanical shock. The contact resistance was found to be increased by 400% after the sixth drop from a height of 0.5 m. Scanning electron microscope images show particle deformation due to abrasion and friction between the contacting surfaces resulting from the sudden impact. Joints are also observed with no connections, which signify open circuits. Almost 25% of the circuits were found open in the samples (after 384 h in a humid environment), which have suffered severe mechanical shock (load drops four times from 0.4 m height). Breaking of the conductive layer of the particle and exposing the underlying polymeric portion were also observed.
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Brock, L. M. "Transient Green’s Function Behavior for a Prestressed Highly Elastic Half-Space." Journal of Applied Mechanics 68, no. 2 (August 28, 2000): 162–68. http://dx.doi.org/10.1115/1.1357167.
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A plane-strain study of a prestressed isotropic compressible neo-Hookean half-space subjected to shear and normal surface loads is performed. The loads are either stationary and applied for an instant, or travel at an arbitrary constant speed. The transient process is viewed as the superposition of infinitesimal deformations upon large, and exact expressions for the displacements, within and upon, the half-space are obtained. These, and the associated wave patterns, demonstrate the anisotropy induced by prestress. The wave speeds themselves are sensitive to prestress; in particular, Rayleigh waves disappear beyond a critical compressive prestress. A critical tensile prestress also exists, beyond which a negative Poisson effect occurs.
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Wang, Cheng-Der. "Lateral Force Induced by Rectangular Surcharge Loads on a Cross-Anisotropic Backfill." Journal of Geotechnical and Geoenvironmental Engineering 133, no. 10 (October 2007): 1259–76. http://dx.doi.org/10.1061/(asce)1090-0241(2007)133:10(1259).
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Liou, J. Y., and J. C. Sung. "Surface responses induced by point load or uniform traction moving steadily on an anisotropic half-plane." International Journal of Solids and Structures 45, no. 9 (May 2008): 2737–57. http://dx.doi.org/10.1016/j.ijsolstr.2007.12.021.
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