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1
Guo, Songfeng, Shengwen Qi, Bowen Zheng, Lei Xue, Xueliang Wang, Ning Liang, Yu Zou et al. "The Confinement-Affected Strength Variety of Anisotropic Rock Mass". Materials 15, n. 23 (27 novembre 2022): 8444. http://dx.doi.org/10.3390/ma15238444.
Testo completoAbstract (sommario):
It has been recognized that the anisotropic structures dominate the deformation and strength properties of laminated rock masses. The resultant strength anisotropy is strongly affected by confining pressures beyond anisotropic structures. Nevertheless, the effects of confinement are inconsistent among existing experiments and not fully understood. This study focuses on the effects of confining pressure on strength anisotropy through theoretical derivation together with experimental results analysis. The variations in the possibility of anisotropic structural plane dominant failure and strength anisotropy degree under different confining pressures are discussed. The different types of anisotropic structural planes, i.e., the fresh contact discontinuity or soft, thick layer, are found as the key factor resulting in different confinement effects. The strength anisotropy weakens gradually and vanishes eventually as confining stress increases for the anisotropic rock mass with the structural plane of fresh contact discontinuity. On the other hand, the strength does not vanish at very high confining stress and the anisotropic strength difference even rises as confining stress increases for the anisotropic rock mass with the anisotropic structural plane of the soft layer. This study improves the understanding of anisotropic rock mass mechanical behavior, especially at high confining stress, and may promote the development of excavation and supporting techniques for underground projects.
2
Reid, D., R. Fanni e A. Fourie. "Assessing the undrained strength cross-anisotropy of three tailings types". Géotechnique Letters 12, n. 1 (marzo 2022): 1–7. http://dx.doi.org/10.1680/jgele.21.00094.
Testo completoAbstract (sommario):
The cross-anisotropic nature of soil strength has been studied and documented for decades, including the increased propensity for cross-anisotropy in layered materials. However, current engineering practice for tailings storage facilities (TSFs) does not appear to generally include cross-anisotropy considerations in the development of shear strengths. This is despite the very commonly seen layering profile in subaerially deposited tailings. To provide additional data to highlight the strength cross-anisotropy of tailings, high-quality block samples from three TSFs were obtained and trimmed to enable hollow cylinder torsional shear tests to be sheared at principal stress angles of 0 and 45° during undrained shearing. The consolidation procedures were carried out such that the drained rotation of principal stress angle that would precede potential undrained shear events for below-slope tailings was reasonably simulated. The results indicated the significant effects of cross-anisotropy on the undrained strength, instability stress ratio, contractive tendency and brittleness of each of the three tailings types. The magnitude of cross-anisotropy effects seen was generally consistent with previous published data on sands.
3
Cheng, Jingyi, Zhijun Wan, Yidong Zhang, Wenfeng Li, Syd S. Peng e Peng Zhang. "Experimental Study on Anisotropic Strength and Deformation Behavior of a Coal Measure Shale under Room Dried and Water Saturated Conditions". Shock and Vibration 2015 (2015): 1–13. http://dx.doi.org/10.1155/2015/290293.
Testo completoAbstract (sommario):
This paper presents an experimental investigation of anisotropic strength and deformation behavior of coal measure shale. The effect of two factors (i.e., anisotropy and water content) on shale strength and deformation behavior was studied. A series of uniaxial and triaxial compression tests were conducted on both room dried and water saturated samples for different lamination angles. The test results indicate that (1) the compressive strength, cohesion, internal friction angle, tangent Young’s modulus, and axial strain corresponding to the peak and residual strengths of room dried specimens exhibit anisotropic behavior that strongly depends on the orientation angle(β); (2) in comparison to the room dried samples, the compressive strength and Young’s modulus as well as the anisotropy are all reduced for water saturated specimens; and (3) the failure mechanism of the samples can be summarized into two categories: sliding along lamination and shearing of rock material, with the type occurring in a particular situation depending strongly on the lamination orientation angles with respect to the major principal stress. According to the findings, it is strongly recommended that the effect of anisotropy and water content on the strength and deformation behavior of the rock must be considered in ground control designs.
4
Lai, Van Qui, Jim Shiau, Suraparb Keawsawasvong, Sorawit Seehavong e Lowell Tan Cabangon. "Undrained Stability of Unsupported Rectangular Excavations: Anisotropy and Non-Homogeneity in 3D". Buildings 12, n. 9 (10 settembre 2022): 1425. http://dx.doi.org/10.3390/buildings12091425.
Testo completoAbstract (sommario):
The stability of unsupported rectangular excavations in undrained clay is examined under the influence of anisotropy and heterogeneity using the three-dimensional finite element upper and lower bound limit analysis with the Anisotropic Undrained Shear (AUS) failure criterion. Three anisotropic undrained shear strengths are considered in the study, namely triaxial compression, triaxial extension, and direct simple shear. Special considerations are given to the study of the linearly-increased anisotropic shear strengths with depth. The numerical solutions are presented by an undrained stability number that is a function of four dimensionless parameters, i.e., the excavated depth ratio, the aspect ratio of the excavated site, the shear strength gradient ratio, and the anisotropic strength ratio. To the authors’ best knowledge, this is the first of its kind to present the stability solutions of 3D excavation considering soil anisotropy and heterogeneity. As such, this paper introduces a novel approach for predicting the stability of unsupported rectangular excavation in undrained clays in 3D space, accounting for soil anisotropy and non-homogeneity. Notably, it develops a basis to formulate a mathematical equation and design charts for estimating the stability factor of such type of excavation, which should be of great interest to engineering practitioners.
5
Jena, Pradipta Kumar, K. Siva Kumar e A. K. Singh. "Effect of Tempering Temperature on Microstructure, Texture and Mechanical Properties of a High Strength Steel". International Journal of Manufacturing, Materials, and Mechanical Engineering 4, n. 3 (luglio 2014): 33–49. http://dx.doi.org/10.4018/ijmmme.2014070102.
Testo completoAbstract (sommario):
This work describes the microstructure, texture and anisotropy in mechanical behavior of a high strength steel in various tempered conditions. The microstructures and mechanical properties change considerably with varying tempering temperatures. The material exhibits low in-plane anisotropy and low anisotropic index in terms of yield strength and elongation with increase in tempering temperature. The anisotropy of the material displays similar behavior to that of the yield strength.
6
Lee, K. M., e R. K. Rowe. "Effects of undrained strength anisotropy on surface subsidences induced by the construction of shallow tunnels". Canadian Geotechnical Journal 26, n. 2 (1 maggio 1989): 279–91. http://dx.doi.org/10.1139/t89-037.
Testo completoAbstract (sommario):
The implementation of an anisotropic soil model that allows consideration of the variation of undrained strength due to anisotropy is described. This analysis is then used to identify the significance of strength anisotropy on the prediction of deformation behaviour of a shallow tunnel. It is found that, for the case of an unlined tunnel, attention should be given to the effect of strength anisotropy particularly for a soil possessing type "K" anisotropy (i.e., where the smallest undrained strength occurs at an angle θ other than the vertical or the horizontal, and the smallest value usually occurs at θ = 45°). On the other hand, for a lined tunnel, the effect of strength anisotropy upon the surface settlement profile will depend upon the size of a so-called "gap" parameter. The gap represents the net effect of loss of ground and some "workmanship" factors in a plane strain finite element analysis. Increasing the gap eases the restrictions imposed by the tunnel lining upon possible soil deformations, thereby increasing the effect of strength anisotropy. However, it is shown that for a lined tunnel with a moderate value of gap, detailed consideration of strength anisotropy may not be necessary. Key words: strength anisotropy, tunnelling, predictions, surface subsidences, finite element method, soil model, soft clays, vane strength.
7
Seki, Hironori, Masakazu Tane e Hideo Nakajima. "Fatigue Strength of Lotus-Type Porous Magnesium". Materials Science Forum 561-565 (ottobre 2007): 1681–84. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.1681.
Testo completoAbstract (sommario):
We studied the fatigue strength of lotus-type porous magnesium with cylindrical pores aligned unidirectionally, which was fabricated through unidirectional solidification in pressurized hydrogen atmospheres. The fatigue strength shows anisotropy; the fatigue strength in the direction parallel to the longitudinal axis of pores is higher than that in the perpendicular direction. Not only anisotropic pores but also fiber texture grown along the pore direction contributes to the anisotropy in the fatigue strength.
8
Watson, Julian Matthew, Abouzar Vakili e Mateusz Jakubowski. "Rock Strength Anisotropy in High Stress Conditions: A Case Study for Application to Shaft Stability Assessments". Studia Geotechnica et Mechanica 37, n. 1 (1 marzo 2015): 115–25. http://dx.doi.org/10.1515/sgem-2015-0013.
Testo completoAbstract (sommario):
Abstract Although rock strength anisotropy is a well-known phenomenon in rock mechanics, its impact on geotechnical design is often ignored or underestimated. This paper explores the concept of anisotropy in a high stress environment using an improved unified constitutive model (IUCM), which can account for more complex failure mechanisms. The IUCM is used to better understand the typical responses of anisotropic rocks to underground mining. This study applies the IUCM to a proposed rock shaft located in high stress/anisotropic conditions. Results suggest that the effect of rock strength anisotropy must be taken into consideration when assessing the rock mass response to mining in high stress and anisotropic rock conditions.
9
Zapata-Medina, David G., Leon D. Cortes-Garcia, Richard J. Finno e Luis G. Arboleda-Monsalve. "Stiffness and strength anisotropy of overconsolidated Bootlegger Cove clays". Canadian Geotechnical Journal 57, n. 11 (novembre 2020): 1652–63. http://dx.doi.org/10.1139/cgj-2019-0068.
Testo completoAbstract (sommario):
This paper presents the evaluation of the stiffness and strength anisotropy of overconsolidated (OC) Bootlegger Cove Formation (BCF) clays at the Port of Alaska, formerly known as the Port of Anchorage. The stiffness and strength anisotropic material response was evaluated based on triaxial samples equipped with internal instrumentation including a submersible load cell and three subminiature linear variable displacement transducers (LVDTs). Three sets of bender elements were used in this research to measure shear wave velocities for different propagation and polarization directions. The effects of reproducing the stress history of the soil deposit on the stiffness cross-anisotropic behavior of the material are discussed. The laboratory test results are compared with in situ measurements of shear wave velocities based on suspension logging and crosshole and downhole soundings. The results of the experimental program showed that BCF clay is a cross-anisotropic material. Mean stiffness anisotropy ratios ranged from 0.90 to 1.22 and 0.93 to 1.46 for lightly OC and OC conditions, respectively. Strength anisotropy ratios, defined as the ratio of undrained shear strength under triaxial extension to compression, varied between 0.8 and 0.5. It is found that reproducing the stress history of the OC soil deposit during the laboratory reconsolidation stage did not have a significant impact on the initial stiffness anisotropy ratios of the BCF clay.
10
Shesterikov, S. A., A. M. Lokochtchenko e E. A. Mjakotin. "Creep Rupture of Anisotropic Pipes". Journal of Pressure Vessel Technology 120, n. 3 (1 agosto 1998): 223–25. http://dx.doi.org/10.1115/1.2842049.
Testo completoAbstract (sommario):
The problem of creep rupture of pipes from an anisotropic material is studied. The authors suggest a method describing the results of creep rupture tests on thin-walled pipes under complex stress state by taking the strength anisotropy of material into account. A coefficient of strength anisotropy has been determined from the results of creep rupture testing, and a method is given for calculation under various modes of complex stress state. This procedure is based on evaluating the values of the statistical spread from the experimental data. The anisotropy coefficient corresponding to the minimum spread is adopted. The suggested method of calculating the strength anisotropy coefficient is confirmed experimentally.
11
Alencar, A., M. Muñiz-Menéndez, I. Pérez-Rey e R. Galindo. "An experimental study of tensile stress and deformation in an anisotropic rock". IOP Conference Series: Earth and Environmental Science 1295, n. 1 (1 gennaio 2024): 012010. http://dx.doi.org/10.1088/1755-1315/1295/1/012010.
Testo completoAbstract (sommario):
Abstract Anisotropy is a very common condition in rock mass; it can be due to different factors and directly affects the failure mechanisms affecting the rock mass. For example, metamorphic rocks that are foliated, sedimentary rocks that are stratified or volcanic formations with alternating layers. Despite the existence of several studies related to anisotropy those specifically addressing the tensile strength of anisotropic rocks are quite limited. The present study is focused on the determination of the deformability, compressive and tensile strength of anisotropic rocks. It must be highlighted that the mechanical behavior of the anisotropic rock mass is dependent on the angle between the inclination of planes of weakness (e.g. foliation) and the direction of the load. Assuming a vertical load, the two extremes of tensile strength are 0°(horizontal) and 90° (vertical). A series of laboratory tests has been done in anisotropic sandstone (lithic arkose), from Burgos (Spain), including uniaxial compressive strength tests, direct tensile strength tests, and diametric compression (Brazilian tests). The tests were carried out with strain gauges that allowed estimating the elastic modulus. To determine the anisotropic direction, ultrasonic pulse wave velocity tests were also performed. The variation of strength and deformability as a function of anisotropy is analyzed, as well as the variation of elastic behavior in tensile and compressive.
12
Khan, R. "Anisotropic Deformation Behavior of Al2024T351 Aluminum Alloy". Journal of Engineering Research [TJER] 10, n. 1 (1 giugno 2013): 80. http://dx.doi.org/10.24200/tjer.vol10iss1pp80-87.
Testo completoAbstract (sommario):
The objective of this work was to investigate the effects of material anisotropy on the yielding and hardening behavior of 2024T351 aluminum alloy using isotropic and anisotropic yield criteria. Anisotropy may be induced in a material during the manufacturing through processes like rolling or forging. This induced anisotropy gives rise to the concept of orientation-dependent material properties such as yield strength, ductility, strain hardening, fracture strength, or fatigue resistance. Inclusion of the effects of anisotropy is essential in correctly predicting the deformation behavior of a material. In this study, uniaxial tensile tests were first performed in all three rolling directions, L , T and S , for smooth bar specimens made from hot rolled plate of Al2024 alloy. The experimental results showed that the L - and T -directions yielded higher yield strengths and a greater percentage of elongation before fracture than the S -direction. Subsequently, finite element analysis of tensile specimens was performed using isotropic (von Mises) and anisotropic (Hill) yield criteria to predict the onset of yielding and hardening behaviors during the course of deformation. Hill's criterion perfectly fitted with the test data in the S -direction, but slightly underestimated the yield strength in L -direction. The results indicated that the Hill yield criterion is the most suitable one to predict the onset of yielding and hardening behaviors for 2024T351 aluminum alloy in all directions.
13
Σαρόγλου, χ., Π. Μαρίνος e Γ. Τσιαμπάος. "GEOLOGICAL CONTROLS ON INTACT ROCK STRENGTH. THE EFFECT OF ANISOTROPY". Bulletin of the Geological Society of Greece 36, n. 4 (1 gennaio 2004): 1826. http://dx.doi.org/10.12681/bgsg.16653.
Testo completoAbstract (sommario):
The factors that influence the strength and deformation of the intact rock are the mineral composition, the fabric, the grain size and the degree of alteration and weathering. Anisotropy is a characteristic of intact foliated metamorphic rocks (slates, gneisses, phyllites, schists). The current paper deals with the pronounced effect of the fabric of anisotropic rocks on the strength and deformation characteristics of intact rocks. It is part of ongoing research in the Department of Geotechnical Engineering, National Technical University of Athens. Testing was used to establish the anisotropic behaviour of selected metamorphic rocks. The effect of anisotropy on various mechanical properties (strength, deformation) and dynamic properties (wave velocity) was examined. The degree of strength anisotropy of these rocks can be indirectly estimated, by wave propagation through the rock, and thus they can be classified by means of geological and geotechnical indexes.
14
Ou, Xuefeng, Xuemin Zhang, Han Feng, Cong Zhang, Xianshun Zhou e Lei Wang. "Static and Dynamic Brazilian Tests on Layered Slate considering the Bedding Directivity". Advances in Civil Engineering 2020 (16 dicembre 2020): 1–11. http://dx.doi.org/10.1155/2020/8860558.
Testo completoAbstract (sommario):
A layered rock usually exhibits strong anisotropy due to its layered structure. In order to study the anisotropic effect on its static and dynamic tensile properties, a medium strength anisotropy slate is chosen and tested in five groups of bedding plane dip angles. The dynamic tests were carried out by a split Hopkinson pressure bar (SHPB), and the failure process of rock samples is recorded by a high-speed camera. The failure mode and strength characteristic of the slate are analyzed. The static test results show that layered structure significantly affects the failure mode, and the influence of the bedding plane depends on the degree of anisotropy. The static and dynamic “tensile strength” exhibit the “U” type strength anisotropy. For samples in the same dip angle group, the “tensile strength” shows clear dynamic strengthening effect, and the growth rate is most significant at θ = 45°.
15
Chen, Rui, Zai Hong Li, Wei Dong Lei e Wen Bin Luo. "Strength Anisotropy of a Tailings Sand and its Effect on Stability of a Tailing Dam". Advanced Materials Research 261-263 (maggio 2011): 1719–23. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.1719.
Testo completoAbstract (sommario):
In current engineering practice, the effect of strength anisotropy on stability analysis of tailings dam is often ignored. This paper presents direct shear test results on a tailing sand with different angles between shear direction and bedding plane. It is found that shear strength of this soil is significantly directional dependent. The variations in peak friction angle are about 11o, which is approximately 28.3% of the minimum value. The effect of strength anisotropy on stability of a tailings dam is also investigated. The analysis considering anisotropic strength shows a smaller factor of safety and shallower most critical slip surface as compared with isotropic strength model that is used in current engineering practice. To achieve more accurate stability analysis of tailings dams, it is suggested to take into account shear strength anisotropy of tailings soils.
16
Garga, Vinod K., e Mahbubul A. Khan. "Interpretation of field vane strength of an anisotropic soil". Canadian Geotechnical Journal 29, n. 4 (1 agosto 1992): 627–37. http://dx.doi.org/10.1139/t92-070.
Testo completoAbstract (sommario):
Determination of the undrained shear strength (Su) of overconsolidated soils such as the weathered clay crust overlying Leda clay is important for the design of shallow foundations and embankments. In situ vane shear tests and isotropically consolidated undrained triaxial tests have been conventionally used for this purpose. Contrasting test results from these two methods, low Su obtained from triaxial tests and high Su obtained from in situ vane shear tests, motivated further research into this problem. Strength anisotropy, due to in situ anisotropic state of stress and orientation of soil fabric during deposition, is believed to be the reason for these contrasting results. Improved testing and interpretation techniques for this type of anisotropic soil have been proposed. Weathered crusts are generally heavily over-consolidated, with K0 values greater than unity. Undrained triaxial shear tests conducted to date by various researchers are either isotropically consolidated or are anisotropically consolidated assuming K0 smaller than unity. Neither of these two methods represents the in situ state of stress of a clay crust. Therefore, in this investigation, the undisturbed samples were reconsolidated anisotropically to the in situ state of stress (K0 > 1) before shearing undrained in the triaxial test. Direct shear tests on horizontal and vertical specimens consolidated to normal stresses equal to σvo′ and σho′, respectively, were also conducted to investigate the strength anisotropy. Field vane tests have been reinterpreted in terms of this strength anisotropy. The undrained shear strength on top and bottom horizontal planes (Suh) obtained from these field vane tests within the crust provided comparable results with those from laboratory triaxial and direct shear tests which were reconsolidated to in situ stresses. Key words : in situ vane test, undrained shear strength, strength anisotropy, rate effect, anisotropic in situ state, weathered clay crust, overconsolidation.
17
Kaldar-ool, A. K. B., R. N. Sandan e A. Kh H. Mongush. "Elastic con- stants of cylindrically anisotropic material". Vestnik Tomskogo gosudarstvennogo arkhitekturno-stroitel'nogo universiteta. JOURNAL of Construction and Architecture 26, n. 3 (13 giugno 2024): 158–69. http://dx.doi.org/10.31675/1607-1859-2024-26-3-158-169.
Testo completoAbstract (sommario):
This article examines new cylindrically anisotropic materials, including winding composite materials reinforced with various fiber, and a mathematical solution of the fourth-order partial differential equation with two variables in polar coordinates.Purpose: Ther aim of this work is to study anisotropy properties of composite materials with cylindrical anisotropy.Methodology/approach: Foe a solution, equations are translated into Cartesian coordinates, and stress functions are used as a sum of polynomials. As a result of the solution, two relations are obtained between the elastic constants in the main direction of anisotropy, i.e., elasticity parameters. These parameters are important to determine the mechanical properties of anisotropic material.Research findings: New high-strength composite materials are improved to apply in new technologies for building design and construction, high-strength structures are obtained using synthetic composite materials.Originality/value: Elastic constants for cylindrically anisotropic materials represent an innovative approach to determine the properties of composite materials with a flat anisotropy scheme, which make it easier and more efficient to determine elasticity parameters and strength in an arbitrary direction of coordinate axes.
18
Jafarzadeh, Fardin, Amirsajjad Poorakbar e Mahdi Moghayad. "Investigation on the effect of intermediate principal stress on shear behaviour of unsaturated soils". E3S Web of Conferences 544 (2024): 01033. http://dx.doi.org/10.1051/e3sconf/202454401033.
Testo completoAbstract (sommario):
Directional-dependent properties of the soil, like shear strength, stiffness and hydraulic conductivity, are known as anisotropy in soils. Shape and size of the soil particles and void distribution as microstructure characteristics and external factors such as stress history, environmental and geological conditions, and present stress condition can be the causes of the anisotropy in soils. In this paper, the behaviour of soil has been studied in stress-strain plain under monotonic anisotropic loading to investigate the effect of induced anisotropy on brittleness index of soil sample. The brittleness index of the soil is defined as the difference between the ultimate and peak shear strength divided by the peak shear strength of the soil. The two major parameters describing induced anisotropy or anisotropic loading are intermediate principal stress (b) and principal stress direction (α) which are representative of the difference between intermediate, maximum and minimum principal stresses and the rotation angle of the principal stresses’ axis, respectively. This paper only takes the effect of intermediate principal stress with the values of 0.25, 0.5, 0.75. In addition, the soil is in the unsaturated state with the saturation degree of 80% using the constant water (C.W.) method.
19
Skulanova, N. S., T. I. Polyakova, S. A. Golaido, V. G. Suchkov, A. I. Korotkova e A. A. Zotikov. "Anisotropy of Thread Strength". Fibre Chemistry 53, n. 1 (maggio 2021): 25–29. http://dx.doi.org/10.1007/s10692-021-10233-x.
Testo completo
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Mehta, PK, e AM Leshchinsky. "Anisotropy of Concrete Strength". Cement, Concrete and Aggregates 12, n. 2 (1990): 117. http://dx.doi.org/10.1520/cca10280j.
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Hwang, Jeaan, Mandar Dewoolkar e Hon-Yim Ko. "Stability analysis of two-dimensional excavated slopes considering strength anisotropy". Canadian Geotechnical Journal 39, n. 5 (1 ottobre 2002): 1026–38. http://dx.doi.org/10.1139/t02-057.
Testo completoAbstract (sommario):
Using the finite element method, a cohesive horizontal ground is sequentially excavated until the stress state along a potential slip surface of the excavated slope reaches the critical state. Mobilized friction angle and stress ratio contours in the slope generated by the finite element solution are examined to quantify the part of the slip surface that undergoes extension resulting in anisotropic conditions. The effects of factors such as excavation depths, drainage boundary conditions, slope angles, and initial stress conditions on slope stability are investigated. It is shown that excavated slopes display anisotropic behavior and that the consideration of strength anisotropy in slope stability analysis is essential. For the example considered, it was found that the extent of the extension zone of the slip surface increases as the slope angle decreases and that this relationship is linear.Key words: slope stability, strength anisotropy, finite element method, limiting equilibrium.
22
Zhang, Jun, Mingchang Ji, Yafei Jia, Chenxi Miao, Cheng Wang, Ziyang Zhao e Yewei Zheng. "Anisotropic Shear Strength Behavior of Soil–Geogrid Interfaces". Applied Sciences 11, n. 23 (1 dicembre 2021): 11387. http://dx.doi.org/10.3390/app112311387.
Testo completoAbstract (sommario):
This paper presents an experimental study on the anisotropic shear strength behavior of soil–geogrid interfaces. A new type of interface shear test device was developed, and a series of soil–geogrid interface shear tests were conducted for three different biaxial geogrids and three different triaxial geogrids under the shear directions of 0°, 45° and 90°. Clean fine sand, coarse sand, and gravel were selected as the testing materials to investigate the influence of particle size. The experimental results for the interface shear strength behavior, and the influences of shear direction and particle size are presented and discussed. The results indicate that the interface shear strength under the same normal stress varies with shear direction for all the biaxial and triaxial geogrids investigated, which shows anisotropic shear strength behavior of soil–geogrid interfaces. The soil–biaxial geogrid interfaces show stronger anisotropy than that of the soil–triaxial geogrid interfaces under different shear directions. Particle size has a great influence on the anisotropy shear strength behavior of soil–geogrid interfaces.
23
Ashour, Hamdy A. "A compressive strength criterion for anisotropic rock materials". Canadian Geotechnical Journal 25, n. 2 (1 maggio 1988): 233–37. http://dx.doi.org/10.1139/t88-027.
Testo completoAbstract (sommario):
This paper proposes a general compressive strength criterion for anisotropic rock materials under multiaxial states of stress. The proposed criterion is a generalization of the Von Mises' criterion for yielding of ductile metals, which has also been used previously as a strength criterion for brittle fracture in the spirit of both being limits of linear elastic behavior. The presently proposed criterion takes into consideration the effects of the confining pressure, the various stress components, and the material anisotropy on rock material failure in a multiaxial stress state. To verify the applicability of the proposed criterion, it has been used to construct the failure envelopes for several types of rock materials. Consequently, the constructed failure envelopes and the corresponding experimental results have been compared. In all cases, a close agreement with the experimental results has been achieved. This result demonstrates the versatility and applicability of the proposed strength criterion in representing the compressive strength behavior of anisotropic rock materials under complex multiaxial states of stress. Key words: strength, rock materials, anisotropy.
24
Kušnír, Jakub, Tomáš Grabec, Kristýna Zoubková, Pavla Stoklasová, Petr Sedlák e Hanuš Seiner. "Apparent anisotropic thermal diffusivity measured in cubic single crystals by transient grating spectroscopy". Journal of Applied Physics 133, n. 12 (28 marzo 2023): 125108. http://dx.doi.org/10.1063/5.0136850.
Testo completoAbstract (sommario):
The effect of elastic anisotropy on thermal diffusivity determination by transient grating spectroscopy (TGS) was studied. In experiments performed on a set of cubic single crystals, it was observed that TGS measurements may indicate anisotropy of thermal diffusivity in otherwise thermally isotropic materials, and that the strength of this apparent anisotropy is correlated with the strength of the elastic anisotropy. To find a source of the observed phenomenon, finite-element simulations of the TGS measurements were carried out. Time-domain TGS signals were generated from the simulations and processed identically to the experimental data. The simulation results revealed that the elastic anisotropy affects the detected time-domain signals. Consequently, the thermal diffusivity coefficients determined from them showed the artificial directional dependence. For the chosen set of cubic crystals, ranging from nearly isotropic to strongly anisotropic in terms of elastic constants, this simulated directional dependence was in full agreement with the one observed in the experiments.
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Decker, Luke, e Qunshan Zhang. "Quantifying and correcting residual azimuthal anisotropic moveout in image gathers using dynamic time warping". GEOPHYSICS 85, n. 5 (23 luglio 2020): O71—O82. http://dx.doi.org/10.1190/geo2019-0324.1.
Testo completoAbstract (sommario):
We have developed a novel application of dynamic time warping (DTW) for correcting residual moveout in image gathers, enhancing seismic images, and determining azimuthal anisotropic orientation and relative intensity when moveout is caused by wave propagation through a medium possessing elliptical horizontally transverse isotropy (HTI). The method functions by first using DTW to determine the sequences of integer shifts that most closely match seismic traces within an image gather to its stack and then applying those shifts to flatten the gather. Flattening shifts are fitted to an ellipse to provide an approximation for the orientation and relative strength of elliptical HTI anisotropy. We evaluated the method on synthetic and 3D field data examples to show how it is able to (1) correct for residual azimuthal anisotropic moveout, (2) accurately recover high-frequency information and improve feature resolution in seismic images, and (3) determine the anisotropic orientation while providing a measure of relative strength of elliptic anisotropy. Although the method is not intended to replace anisotropic processing techniques for moveout correction, we find that it has the ability to inexpensively approximate the effects of such operations while providing a representation of the elliptic HTI anisotropy present within a volume.
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Vavryčuk, Václav. "Weak anisotropy-attenuation parameters". GEOPHYSICS 74, n. 5 (settembre 2009): WB203—WB213. http://dx.doi.org/10.1190/1.3173154.
Testo completoAbstract (sommario):
Velocity anisotropy and attenuation in weakly anisotropic and weakly attenuating structures can be treated uniformly using weak anisotropy-attenuation (WAA) parameters. The WAA parameters are constructed in a way analogous to weak anisotropy (WA) parameters designed for weak elastic anisotropy. The WAA parameters generalize WA parameters by incorporating attenuation effects. They can be represented alternatively by one set of complex values or by two sets of real values. Assuming high-frequency waves and using the first-order perturbation theory, all basic wave quantities such as the slowness vector, the polarization vector, propagation velocity, attenuation, and the quality factor are linear functions of WAA parameters. Numerical modeling shows that perturbation equations have different accuracy for different wave quantities. The propagation velocity usually is calculated with high accuracy. However, the attenuation and quality factor can be reproduced with appreciably lower accuracy. This happens mostly when the strength of velocity anisotropy is higher than 10% and attenuation is moderate or weak [Formula: see text]. In this case, the errors of the attenuation or [Formula: see text]-factor can attain values comparable to the strength of anisotropy or even higher. A simple modification of the equations by including some higher-order perturbations improves accuracy by three to four times.
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Zdravkovic, Lidija, e Richard J. Jardine. "Undrained anisotropy of K0-consolidated silt". Canadian Geotechnical Journal 37, n. 1 (1 febbraio 2000): 178–200. http://dx.doi.org/10.1139/t99-094.
Testo completoAbstract (sommario):
Direct measurements of the initial shear strength and yielding anisotropy of a dense, K0-consolidated silt are described and interpreted within a bounding-surface framework. The experiments were performed using the Imperial College large hollow cylinder apparatus, in which samples were sheared undrained with a range of orientations, α, of the major principal stress, σ1, following initial K0 consolidation. The interpretation is aided by data from oedometer and triaxial stress path tests. Strongly anisotropic stiffness, yielding, undrained strength, and mobilized angle of shearing resistance, ϕ', characteristics are revealed. The effects of drained and undrained stress changes applied to the samples after K0 consolidation are also described.Key words: anisotropy, hollow cylinder, K0 consolidation, silt, bounding surface.
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Jayahari, L., K. Nagachary, Chandra Ch Sharath e SM Hussaini. "Anisotropy Study of Inconel 718 alloy at Sub-Zero temperatures". E3S Web of Conferences 184 (2020): 01004. http://dx.doi.org/10.1051/e3sconf/202018401004.
Testo completoAbstract (sommario):
There is an increase in demand for new alloys in aerospace, power generation and nuclear industries. Nickel Based super alloys are known for having distinctive properties which are best suitable for these industries. In this study Nickel based super alloy Inconel 718, is used. Over the many years of intense research and development, these alloys have seen considerable evolution in their properties and efficiency. Behaviour of materials and its forming characteristics can be precisely analysed by determining anisotropic behaviour and mechanical properties. In the present study, tried to analyse the mechanical properties of Inconel 718 like yield strength (Ys), ultimate tensile strength (UTS), strain hardening exponent (n) and strain hardening coefficient (k). Uni-axial tensile tests were conducted on specimens with various parameters such as orientations, temperature and Strain rate. Anisotropy of Inconel 718 alloy was measured based on measurable parameters. The normal anisotropy parameter (f) and planer anisotropy (Δr) were measured and observed that the anisotropy parametres are incresed with the decrease in temperature.
29
Shohda, Ahmed M., Waleed M. Draz, Faisal A. Ali, Mohamed A. Yassien e Mahrous Ali Mohamed Ali. "INVESTIGATING THE ANISOTROPY STRENGTH INDEX (ASI) FOR SOME EGYPTIAN ORNAMENTAL STONES". Rudarsko-geološko-naftni zbornik 38, n. 1 (2023): 41–48. http://dx.doi.org/10.17794/rgn.2023.1.4.
Testo completoAbstract (sommario):
The nature of ornamental stones is anisotropic. The heterogeneous characteristics of the anisotropic rocks vary with direction. The highest to lowest strength ratio is known as the anisotropy strength index (ASI). A thorough investigation of the ASI is necessary to determine the best-directed loads for these rocks. On core specimens that have been bored parallel and perpendicular to the weakness planes, this is estimated using both uniaxial compression and point load testing. For this examination, four different rock types had cores that were drilled conventionally and in line with weakness planes. The research shows that drilling cores to weakness planes at a normal or nearly normal angle (90° to 60°) yields the best, most dependable ASI. According to the current study’s findings, the ASI fluctuates depending on how uniformly the mineral content and texture of rocks are. A suggested way to calculate the ASI and the load point strength is also included. This study reveals that the employment of ornamental stone as is (for example, precipitation position is more robust and reliable than that perpendicular form) is critical in determining the resilience of this type of rock and its spatial implementation (e.g. flooring).
30
Deb, Debabrata, Banibrata Mukhopadhyay e Fridolin Weber. "Effects of Anisotropy on Strongly Magnetized Neutron and Strange Quark Stars in General Relativity". Astrophysical Journal 922, n. 2 (26 novembre 2021): 149. http://dx.doi.org/10.3847/1538-4357/ac222a.
Testo completoAbstract (sommario):
Abstract We investigate the properties of anisotropic, spherically symmetric compact stars, especially neutron stars (NSs) and strange quark stars (SQSs), made of strongly magnetized matter. The NSs are described by the SLy equation of state (EOS) and the SQSs by an EOS based on the MIT Bag model. The stellar models are based on an a priori assumed density dependence of the magnetic field and thus anisotropy. Our study shows that not only the presence of a strong magnetic field and anisotropy, but also the orientation of the magnetic field itself, have an important influence on the physical properties of stars. Two possible magnetic field orientations are considered: a radial orientation where the local magnetic fields point in the radial direction, and a transverse orientation, where the local magnetic fields are perpendicular to the radial direction. Interestingly, we find that for a transverse orientation of the magnetic field, the stars become more massive with increasing anisotropy and magnetic-field strength and increase in size since the repulsive, effective anisotropic force increases in this case. In the case of a radially oriented magnetic field, however, the masses and radii of the stars decrease with increasing magnetic-field strength because of the decreasing effective anisotropic force. Importantly, we also show that in order to achieve hydrostatic equilibrium configurations of magnetized matter, it is essential to account for both the local anisotropy effects as well as the anisotropy effects caused by a strong magnetic field. Otherwise, hydrostatic equilibrium is not achieved for magnetized stellar models.
31
Li, Li, e Michel Aubertin. "A crack-induced stress approach to describe the tensile strength of transversely isotropic rocks". Canadian Geotechnical Journal 39, n. 1 (1 febbraio 2002): 1–13. http://dx.doi.org/10.1139/t01-069.
Testo completoAbstract (sommario):
Rocks are generally more or less anisotropic, depending on their structure at the scale of interest. In engineering applications, the magnitude of such anisotropy must often be determined for compressive as well as tensile loading conditions. In this paper, the authors present the results of an investigation on tensile failure of transversely isotropic rocks, based on Inglis' analytical solution for the stress at the boundary of an elliptical flaw. The strength of transversely isotropic rocks is assumed to be controlled by the maximum tensile local stress along the crack boundary. Equations are developed and compared with tensile test data taken from the literature. The results show that the proposed formulations represent well the direct and indirect tensile strength of anisotropic rocks as a function of bedding plane orientation. It is also shown that the proposed physical model correlates well with the results obtained from more empirical formulations.Key words: rock mechanics, anisotropy, transverse isotropy, tensile strength, Brazilian test, crack.
32
Huang, Tao, Zhuo Song, Fuxiao Chen, Junqing Guo, Yanbo Pei, Binghui Xing, Nan Xiang e Kexing Song. "Influence of the Anisotropy on the Microstructure and Mechanical Properties of Ti/Al Laminated Composites". Materials 13, n. 16 (12 agosto 2020): 3556. http://dx.doi.org/10.3390/ma13163556.
Testo completoAbstract (sommario):
Anisotropy is the difference in the microstructure or mechanical properties of materials in different directions. Anisotropic behavior occurs in rolled sheets, and this anisotropy is very obvious in laminated composites. In this work, the influence of anisotropy on the microstructure and mechanical properties of Ti/Al laminated composites fabricated by rolling was investigated. The results show that the microstructure and mechanical properties of the Ti/Al laminated composites were obviously anisotropic. The grains in the Al layer of the composites were elongated along the rolling direction and were compressed perpendicular to the rolling direction. The grains in the Ti layer of the composites had no obvious preferential orientation and comprised mainly twins. With the rolling direction as 0°, the mechanical properties of the Ti/Al laminated composites varied greatly as the angle of the composites increased. The tensile strength, elongation and bond strength of the Ti/Al laminated composites decreased with increasing angle of the composites. In addition, the microhardness of the Ti/Al laminated composites increased with increasing angle of the composites.
33
Guo, Shao Hua. "The Shear Failure Modes and Anisotropy Based on the Shear Strength Theory in Classical Solid Mechanics". Applied Mechanics and Materials 387 (agosto 2013): 164–67. http://dx.doi.org/10.4028/www.scientific.net/amm.387.164.
Testo completoAbstract (sommario):
The shear failure modes of anisotropic solids are studied here based on the elastic standard space of physical presentation, some new shear failure phenomena for anisotropic solids are presented. The relations between shear failure modes and anisotropy are discussed. The results show that there are obvious differences in shear failure modes for different anisotropic solids.
34
Abrashkevych, Yurii, Hryhorii Machyshyn, Oleksandr Marchenko, Maksym Balaka e Olena Zhukova. "Mechanical strength increasing of abrasive reinforced wheel". Strength of Materials and Theory of Structures, n. 108 (30 maggio 2022): 295–308. http://dx.doi.org/10.32347/2410-2547.2022.108.295-308.
Testo completoAbstract (sommario):
The mechanical strength of unreinforced abrasive wheels is determined by centrifugal and bending forces, but their distribution during reinforcement is unknown. It was assumed that the stresses are distributed evenly, but a comparison of calculations on the theory of elasticity and real characteristics on a special stand showed complete discrepancy. Tensile tests of the wheels made it possible to compare the stresses results in the circumferential and radial directions. Was found that the reinforced wheel is an anisotropic body. Anisotropy can be reduced by displacing one reinforcement mesh relatively to the other by angle of 45°. In this paper, a mathematical model of the stress-strain state of the abrasive reinforced wheel was developed, taking into account the anisotropy of its properties. To determine the centrifugal forces, the theory of elasticity for an orthotropic body is applied. The bending forces that arise in the working wheel were determined during solving the problem of the distribution of deformations in the anisotropic annular plate rigidly fixed along the inner contour. As a result of experimental studies, it was found that stresses reach 8...23 MPa, which can be compared with the ultimate strength of the wheel matrix. The elastic module of the wheel matrix is noticeably greater than the elastic module of the reinforcing mesh, which practically does not perceive the load at the initial stage. The developed mathematical model of the strength indicators for abrasive reinforced wheels makes it possible to predict their reliability and safe operation.
35
Zhang, Hui, Fang Jun Ou, Guo Qing Yin, Jing Bing Yi, Fang Yuan, Bing Xie, Chao Li e Wei Zhao. "Research on Wellbore Stability in Formation with Anisotropic Strength". Advanced Materials Research 765-767 (settembre 2013): 3151–57. http://dx.doi.org/10.4028/www.scientific.net/amr.765-767.3151.
Testo completoAbstract (sommario):
As most of sedimentary rocks are anisotropic, it is significant to research the impact of the anisotropy of strength on wellbore stability in drilling engineering. Particularly, in the Kuqa piedmont exploration area, the anisotropy of strength caused by various jointed surfaces, fracture surfaces and fault planes in formation cause the formation of several groups of weak low-intensity planes traversing borehole . These weak planes will become failure earlier than the rock body in the context of strong stress and high pore pressure, causing chipping, breakouts and sticking. If fractures have good permeability and drilling fluid column pressure is greater than pore pressure, loss may occur. The loss pressure would not be controlled by fracturing pressure and horizontal minimum principal stress, but it depends on the relationship between fracture occurrence and triaxial stress state. In the event of loss, the drilling fluid will flow into these weak structural planes, causing the decrease of friction between rocks and increase of wellbore instability. As a result, for strongly anisotropic formation, the collapse pressure and leakage pressure of weak planes are key factors for evaluating well drilling stability. In this study, according to the stability evaluation on the transversely isotropic rock mechanics in Keshen zone of Kuqa piedmont, the impacts of fracture development on wellbore instability is analyzed; relevant suggestions on engineering geology for the special pressure window in strong anisotropic formation are also put forward.
36
Dai, Chunquan, Hongtao Sui e Chao Ma. "Study on the Ultimate Supporting Force of Shield Excavation Face Based on Anisotropic Strength Theory". Applied Sciences 10, n. 15 (29 luglio 2020): 5222. http://dx.doi.org/10.3390/app10155222.
Testo completoAbstract (sommario):
The determination of the ultimate supporting force of the shield excavation face is an important problem to be solved in shield construction. Considering that the tunnel burial depth ratio has a significant effect on the instability mode of the excavation face, the classic “wedge-prism” limit equilibrium model is improved. Based on the rotation effect of principal stress axis, the Casagrande anisotropic strength equation is introduced into the modified limit equilibrium model of “wedge-prism”, and then the limit equilibrium solution of the ultimate supporting force of shield excavation face in anisotropic soil is deduced. Finally, the influence of each calculation parameter on the ultimate supporting force is analyzed by examples. The research results show that the results of the modified “wedge-prism” calculation model proposed in this paper are slightly larger than those of the centrifugal test. If the influence of the instability mode of excavation face and the anisotropy of soil strength on ultimate supporting force of the shield excavation face is not taken into account, the calculation result will be unsafe. The limit supporting force of shield tunnel excavation surface has a simple linear relationship with the anisotropy ratio. When the anisotropy ratio is greater than 1, the ultimate supporting force of shield excavation face decreases first and then tends to be stable with an increase in the buried depth ratio. When the anisotropy ratio is less than 1, the law is reversed. The more obvious the anisotropy of soil strength, the greater the rate of change of ultimate supporting force. The limit supporting force of the shield excavation face decreases linearly with the exertion of loosening earth pressure, linearly decreases with the increase in soil cohesion, and decreases nonlinearly with the increase in the angle of internal friction in soil. The relevant conclusions will provide theoretical guidance for controlling the reasonable chamber pressure of shield tunneling, and ensure the safety of construction.
37
Glukhikh, Vladimir. "PROBLEM OF THE ANISOTROPY OF ELASTICITY AND STRENGTH IN ANISOTROPIC FIBER MATERIALS". Architecture and Engineering 6, n. 2 (2021): 31–36. http://dx.doi.org/10.23968/2500-0055-2021-6-2-31-36.
Testo completoAbstract (sommario):
Introduction: The paper presents new results of studies on the anisotropy of fiber materials with cylindrical anisotropy, which include filament-wound composite materials reinforced with various fibers. Methods: We suggest a mathematical solution to a fourth-order partial differential equation in polar coordinates with two variables for an orthotropic anisotropic body. To solve this equation, we converted it into Cartesian coordinates and presented the stress function as a sum of polynomials. Results and Discussion: As a result of the solution, we obtained two relationships between the elastic constants in the principal directions of anisotropy (so-called elasticity parameters). One of them was obtained for the first time, and the other results from the solution of the anisotropy problem for an orthotropic curved body, suggested by S. G. Lekhnitsky. The obtained solution does not contradict Lekhnitsky’s solution. Thus, in our opinion, orthotropic materials can be divided into two groups. In one group, when shifting from the radial to the tangential direction, the elastic constants take on extreme values when the layers are at angles of 0, 60, and 90°. In the other group, there is no intermediate extreme value and the elastic constants take on extreme values when the layers are at angles of 0 and 90°. The obtained results can be applied in the development of new high-strength composite materials and new technologies for the design and manufacture of building structures, as well as in the design of high-strength structures from synthetic composite materials.
38
Pan, Ning, e Xiaoshan Zhang. "Shear Strength of Fibrous Sheets: An Experimental Investigation". Textile Research Journal 67, n. 8 (agosto 1997): 593–600. http://dx.doi.org/10.1177/004051759706700807.
Testo completoAbstract (sommario):
This study of the shear strength of fibrous sheets first measures the in-plane shear strengths of various samples, including woven and nonwoven fabrics and paper, using a custom-made apparatus attached to an Instron tester. The structure of the apparatus and the measurement procedures are introduced in this article. The tested shear strength values are then compared with theoretical predictions from an earlier work. Discrepancies and possible causes are analyzed. Load-elongation curves for both tensile and shear are compared for individual fabrics and between fabrics. The relationship between the anisotropy of fabric tensile strength and the ratio of tested and predicted shear strength is explored. Also, the effect of fiber movement during textile deformation is examined. Finally, the original Tsai-Wu theory used for shear strength prediction of anisotropic materials is modified for application to the fibrous sheets, and the new predictions are provided for comparison.
39
Wang, Yangxin, Aijun Li, Chundong Hu, Xiaofei Guo, Xufei Li, Wenzhen Bi, Xicheng Wei e Han Dong. "Microstructure, Texture, and Anisotropic Properties of High-Strength Low-Alloy Steel". Coatings 13, n. 8 (16 agosto 2023): 1442. http://dx.doi.org/10.3390/coatings13081442.
Testo completoAbstract (sommario):
The effects of cold rolling reduction rates and recrystallization annealing temperature on the microstructure, texture, and anisotropic properties of high-strength low-alloy (HSLA) steel were investigated using scanning electron microscopy and electron backscatter diffraction. The results revealed that the constituents of recrystallized, substructured, and deformed structures were strongly affected by cold rolling reduction rates ranging from 33.3% to 66.7% and recrystallization temperatures ranging from 780 to 840 °C. At an annealing temperature of 820 °C, when the cold rolling reduction rate was 33.3%, HSLA steel exhibited a low percentage of recrystallization, with cubic, γ-linear, rolled, and Z-texture (the texture at Euler angles φ1 = 30° and Φ = 20°–30°) structures. The rolled texture and Z-texture increased the strength anisotropy and disappeared at high cold rolling reduction rates. When the annealing temperature was increased from 780 °C to 820 °C, the proportion of recrystallized grains increased, the rolling texture disappeared, and grain orientation gradually gathered in the cubic texture and γ line texture, resulting in low anisotropy of strength. At an annealing temperature of 840 °C, the deformation of the grain disappeared; however, the anisotropy increased compared to annealing at 820 °C because of the formation of a new texture of {001}<−1–20>.
40
Cantor, David, Carlos Ovalle e Emilien Azéma. "Strength and energy consumption of inherently anisotropic rocks at failure". EPJ Web of Conferences 249 (2021): 07003. http://dx.doi.org/10.1051/epjconf/202124907003.
Testo completoAbstract (sommario):
Using a discrete-element approach and a bonding interaction law, we model and test crushable inherently anisotropic structures reminiscent of the layering found in sedimentary and metamorphic rocks. By systematically modifying the level of inherent anisotropy, we characterize the evolution of the failure strength of circular rock samples discretized using a modified Voronoi tesselation under diametral point loading at different orientations relative to the sample’s layers. We characterize the failure strength, which can dramatically increase as the loading becomes orthogonal to the rock layers. We also describe the evolution of the macroscopic failure modes as a function of the loading orientation and the energy consumption at fissuring. Our simulation strategy let us conclude that the length of bonds between Voronoi cells controls the energy being consumed in fissuring the rock sample, although failure modes and strength are considerably changing. We end up this work showing that the microstructure is largely affected by the level of inherent anisotropy and loading orientation.
41
VanderBeek, Brandon P., e Manuele Faccenda. "Imaging upper mantle anisotropy with teleseismic P-wave delays: insights from tomographic reconstructions of subduction simulations". Geophysical Journal International 225, n. 3 (1 marzo 2021): 2097–119. http://dx.doi.org/10.1093/gji/ggab081.
Testo completoAbstract (sommario):
SUMMARY Despite the well-established anisotropic nature of Earth’s upper mantle, the influence of elastic anisotropy on teleseismic P-wave imaging remains largely ignored. Unmodelled anisotropic heterogeneity can lead to substantial isotropic velocity artefacts that may be misinterpreted as compositional heterogeneities. Recent studies have demonstrated the possibility of inverting P-wave delay times for the strength and orientation of seismic anisotropy. However, the ability of P-wave delay times to constrain complex anisotropic patterns, such as those expected in subduction settings, remains unclear as synthetic testing has been restricted to the recovery of simplified block-like structures using ideal self-consistent data (i.e. data produced using the assumptions built into the tomography algorithm). Here, we present a modified parametrization for imaging arbitrarily oriented hexagonal anisotropy and test the method by reconstructing geodynamic simulations of subduction. Our inversion approach allows for isotropic starting models and includes approximate analytic finite-frequency sensitivity kernels for the simplified anisotropic parameters. Synthetic seismic data are created by propagating teleseismic waves through an elastically anisotropic subduction zone model created via petrologic-thermomechanical modelling. Delay times across a synthetic seismic array are measured using conventional cross-correlation techniques. We find that our imaging algorithm is capable of resolving large-scale features in subduction zone anisotropic structure (e.g. toroidal flow pattern and dipping fabrics associated with the descending slab). Allowing for arbitrarily oriented anisotropy also results in a more accurate reconstruction of isotropic slab structure. In comparison, models created assuming isotropy or only azimuthal anisotropy contain significant isotropic and anisotropic imaging artefacts that may lead to spurious interpretations. We conclude that teleseismic P-wave traveltimes are a useful observable for probing the 3-D distribution of upper mantle anisotropy and that anisotropic inversions should be explored to better understand the nature of isotropic velocity anomalies particularly in subduction settings.
42
Hirsch, Jürgen. "Textures in Industrial Processes and Products". Materials Science Forum 702-703 (dicembre 2011): 18–25. http://dx.doi.org/10.4028/www.scientific.net/msf.702-703.18.
Testo completoAbstract (sommario):
Textures and related anisotropy effects which occur in certain industrial processes are presented for as-cast, deformed and annealed (recrystallized) Aluminium alloys and products. They are analyzed in detail and discussed based on their formation mechanisms, which are growth selection during solidification and the formation of new grains during casting and recrystallization, glide on selected slip planes during plastic deformation and oriented nucleation and oriented growth of new grains during recrystallization. Alloy composition and constitution that control microstructure evolution during processing (e.g. casting, extrusion, hot and cold rolling, annealing) determine the material quality and product performance.In these cases industrial processing of Aluminium alloys is specifically designed to control textures to achieve superior anisotropic properties and so better meet special product requirements. Examples are given for resulting properties, like strength and formability / anisotropy effects in packaging and automotive sheet applications. Other examples are given for the etching behaviour of high purity Aluminium capacitor foil and strength anisotropy of age hardened extrusions for aerospace applications.
43
Muslov, Sergey, Nataliya Zaitseva, Nataliya Astashina, Sergey Arutyunov e Vladislav Nikitin. "Calculation and visualization of the enamel and dentin matrix of elastic parameters". Russian Journal of Biomechanics 24, n. 2 (30 giugno 2020): 152–61. http://dx.doi.org/10.15593/rjbiomech/2020.2.05.
Testo completoAbstract (sommario):
The capabilities of the ELATE and MATLAB packages for visualization of the elastic properties of hard tooth tissues are demonstrated. A visual confirmation of the fact of the elastic anisotropy of the hard tissues of the tooth due to the crystal structure of their mineral component was obtained. The study of the indices of anisotropy of enamel and dentin as an inhomogeneous anisotropic medium becomes of practical importance when studying the problems of the strength of tooth tissues and the quality of restorations.
44
Pšenčík, Ivan, e Joe A. Dellinger. "Quasi‐shear waves in inhomogeneous weakly anisotropic media by the quasi‐isotropic approach: A model study". GEOPHYSICS 66, n. 1 (gennaio 2001): 308–19. http://dx.doi.org/10.1190/1.1444909.
Testo completoAbstract (sommario):
In inhomogeneous isotropic regions, S-waves can be modeled using the ray method for isotropic media. In inhomogeneous strongly anisotropic regions, the independently propagating qS1- and qS2-waves can similarly be modeled using the ray method for anisotropic media. The latter method does not work properly in inhomogenous weakly anisotropic regions, however, where the split qS-waves couple. The zeroth‐order approximation of the quasi‐isotropic (QI) approach was designed for just such inhomogeneous weakly anisotropic media, for which neither the ray method for isotropic nor anisotropic media applies. We test the ranges of validity of these three methods using two simple synthetic models. Our results show that the QI approach more than spans the gap between the ray methods: it can be used in isotropic regions (where it reduces to the ray method for isotropic media), in regions of weak anisotropy (where the ray method for anisotropic media does not work properly), and even in regions of moderately strong anisotropy (in which the qS-waves decouple and thus could be modeled using the ray method for anisotropic media). A modeling program that switches between these three methods as necessary should be valid for arbitrary‐strength anisotropy.
45
Zhang, Xidong, Yan Zhuang, Zhen’ang Wang, Changxing Yang e Shunlei Hu. "Anisotropy in the Liquefaction Resistance of Fibre Reinforced Sand". Materials 16, n. 21 (30 ottobre 2023): 6959. http://dx.doi.org/10.3390/ma16216959.
Testo completoAbstract (sommario):
Adding discrete fibres to sand has been seen as a feasible technique to improve sand’s strength as well as liquefaction resistance. Considering the anisotropic distribution of fibre orientations, the anisotropy in the liquefaction resistance of the reinforced sand is also introduced using fibres. Here, the triaxial compression and extension test results of unreinforced and fibre-reinforced sand in different density states are provided, from which the anisotropy in the liquefaction resistance of fibre-reinforced sand is demonstrated. Fibre reinforcement improves the liquefaction resistance of sand by introducing both the densifying effect and the confining effect. The inclusion of fibres increases both the slope and the intercept of the strength envelope in comparison with the unreinforced sand under triaxial compression, while the strength envelope is not affected by fibres under triaxial extension. Stress contribution of fibres makes the ESP of the composite under undrained loading reverse its direction to develop even though the phase transformation is absent. The stress ratio initiating the ESP reversal is irrespective of the fibre content but dependent on the density state under triaxial compression. Under triaxial extension, the stress ratio initiating the ESP reversal remains the same in the samples with varied density states and fibre contents. The mechanism correlating to the strength envelope and ESP reversal of the fibre-reinforced sand was demonstrated following a rule of mixture based constitutive modelling framework. By introducing an alternatively defined pore pressure ratio that incorporates the stress contribution of fibres, the liquefaction state of the fibre reinforced sand is reasonably assessed. Liquefaction remains absent in the sand once the fibres are mixed. The anisotropy in the liquefaction resistance of fibre-reinforced sand arises, as the predominant role played by the fibres to suppress the liquefaction is different when varied loading paths are involved, which is sourced from the anisotropic distribution of fibre orientations.
46
Su, Shi-Fon. "Undrained shear strengths of clay around an advancing cone". Canadian Geotechnical Journal 47, n. 10 (ottobre 2010): 1149–58. http://dx.doi.org/10.1139/t10-011.
Testo completoAbstract (sommario):
Strength anisotropy of clay is significantly associated with the orientation of principal strain. Mobilized undrained shear strength will vary with the orientation of the principal stresses because cone penetration imposes large rotations of the principal stresses in the surrounding soil. The objective of this paper is to investigate the undrained failure modes around an advancing cone. In this study, strain softening behavior is not considered. The strain field of the soil obtained using the strain path method shows that the principal strain conditions of the soil around an advancing cone can be simplified into the following zones: spherical expansion strain zone, plane strain shearing zone, cylindrical expansion shearing zone, cylindrical expansion zone, and transition zone. The mobilized undrained shear strength of clay in various strain states can be determined by employing the anisotropic strength criterion and the associated flow rule. The result shows that the ratio of the equivalent undrained strength mobilized in the vicinity of the cone tip over the undrained shear strength obtained from a Ko-consolidated undrained compression triaxial test is found to range from 0.88 to 1.07 when the strength anisotropy ratio ranges from 0.4 to 0.9.
47
Dong, Qian, Jia Kang, Jinshan Sun, Jingjie Li e Zhen Zhang. "Experimental Study on Anisotropic Mechanical Characteristics of Shale under Triaxial Loading". Applied Sciences 14, n. 9 (30 aprile 2024): 3849. http://dx.doi.org/10.3390/app14093849.
Testo completoAbstract (sommario):
Shale is composed of a rock matrix and bedding planes with a layered structure, resulting in significant anisotropy in its mechanical properties. In order to study the anisotropic mechanical properties of shale, the shale samples were prepared in different orientations with respect to the bedding planes, and the composition and microstructure of shale were first analyzed by X-ray diffractometer (XRD) and scanning electron microscope (SEM), and then the uniaxial and triaxial compression experiment on shale samples with five different bedding angles (the angle between the loading direction and the normal direction of the bedding planes, 0°, 30°, 45°, 60°, and 90°) were conducted under five confining pressures (0, 10, 20, 30, and 40 MPa), respectively; meanwhile, the acoustic emission (AE) test was carried out in the uniaxial test. The results indicate that the mechanical properties and parameters of shale have obvious anisotropy, and the AE characteristics of shale samples with different bedding angles are significantly different during uniaxial loading. Furthermore, the compressive strength and elastic modulus of the shale samples first decrease and then increase with the increase in the bedding angle under different confining pressures. Moreover, according to the anisotropic grade of compressive strength, the shale has moderate anisotropy. In addition, the failure mode of the shale samples is also anisotropic, and varies with the bedding angle and confining pressure.
48
Chen, Liping, Sui Wang, Bin Chen, Xiaokai Niu, Guogang Ying e Bo Wu. "Formulation of Anisotropic Strength Criterion for Geotechnical Materials". Advances in Civil Engineering 2020 (7 settembre 2020): 1–10. http://dx.doi.org/10.1155/2020/8825816.
Testo completoAbstract (sommario):
A new nonlinear unified strength (NUS) criterion is obtained based on the spatially mobilized plane (SMP) criterion and Mises criterion. New criterion is a series of smooth curves between SMP curved triangle and Mises circle in the π plane and thereby unifies the strength criteria. The new criterion can reflect the effect of the intermediate principal stress and consider the strength nonlinearity of a material. Based on the fabric tensor, the anisotropic parameter A is defined, and the anisotropic equation is proposed and introduced into the NUS criterion to form a nonlinear unified anisotropic strength criterion. The new criterion can be used to predict the strength variation of granular materials and cohesive materials under three-dimensional stress and can present the strength anisotropy of the geomaterials. The validity of the new criterion was checked using rock and soil materials. It is shown that the prediction results for the criterion agree well with the test data.
49
Covassi, Pedro A., e Víctor A. Rinaldi. "Measuring mechanical anisotropy on geogrid reinforced soil using a cubical triaxial apparatus". E3S Web of Conferences 92 (2019): 12008. http://dx.doi.org/10.1051/e3sconf/20199212008.
Testo completoAbstract (sommario):
This work describes the main findings of an experimental program focused on the characterization of the mechanical anisotropy of a reinforced cohesive soil using a cubical triaxial apparatus. Several authors have studied the influence of geometry, type, number and arrangement of reinforcement layers on the mechanical behaviour of reinforced soils, mainly dedicated to evaluate the improvement of stiffness and strength. The influence of anisotropy and principal intermediate stress has not been addressed. Conventional triaxial cell (axisymmetric) and pull-out tests are the most common type of devices used in the present studies. The implementation of an experimental program using a cubical triaxial apparatus allows us to consider all the aspects mentioned before, mainly those related to an anisotropic characterization and the principal intermediate stress influence on stress-strain and strength behaviour. Results obtained in this work, show that reinforced soil is a cross-anisotropic material, and its stress-strain and strength behaviour is strongly influenced in sectors I (lode angle between 0° and 60°) and II (lode angle between 60° and 120°) of the octahedral plane. Thus, a complete characterization of geogrid reinforced soil can be made selecting an appropriate set of stress paths in the cubical apparatus.
50
Li, Zhen Feng, Xiang Yun Guo e Ming Zhang. "Correction Factor of Surface Deflection for Inverted Asphalt Pavement Based on Linear-Anisotropy". Advanced Materials Research 255-260 (maggio 2011): 3311–15. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.3311.
Testo completoAbstract (sommario):
Inverted asphalt pavement has been widely used in practical application. Anisotropy of granular material has been proved by experiment, but the current design specifications are also based on isotropic theory. Based on linear-anisotropic model, on the condition of the high, medium and low strength of soil subgrade, 4 different thickness of asphalt layer and 3 different thickness of granular sandwich are been systematically studied, the results show that, the strength of the soil subgrade has bigger effect on the pavement deflection, the deflection difference of the low to the high subgrade is about 14~23%, with the increase of granular material anisotropy, the deflection correction factor is bigger, with the granular sandwich anisotropic rates from 0.1 to 0.5, the deflection correction factor is within 1.04, the thin asphalt layer and the thick granular sandwich have bigger effect on the deflection correction factor, for the common inverted asphalt pavement structure, the proposed deflection correction factor is 1.02~1.04, it can be used directly in asphalt pavement design.