Effect Of Stress-induced Anisotropy Research Articles

Anisotropic seabed soil failure description and three-dimensional simulation method

In order to find out the underlying effect of anisotropy on the failure characteristics from the mesoscopic mechanism, using the concept of fabric tensor and assumption of mutual mapping between isotropic space and anisotropic space, a compound stress is proposed based on the combination of ordinary stress and fabric tensor. This compound stress can be used to describe the primary anisotropic properties effectively. For the difference in the effect of stress-induced anisotropy on shear strength of various geotechnical materials in the deviatoric plane, a generalized failure criterion is proposed. This failure criterion can effectively describe various criteria forms from Von-Mises criterion to SMP criterion within a relatively large range. The hydrostatic pressure effect can also be indicated by the shape of the power function on the meridional plane. A primary anisotropy generalized failure criterion can be obtained when the compound stress is used to describe the new generalized failure criterion and the corresponding transformation stress method has been proposed. This method can consider the effect of native induced anisotropy and stress induced anisotropy on the shear strength simultaneously. The comparison between predicted and tested results shows that the proposed anisotropic generalized stress failure criterion and its transformation method can be applied to the geotechnical engineering practice simply, its rationality and applicability have also been verified.

Effect of stress-induced anisotropy on shear modulus response of compacted coal ash under small-strain dynamic loading conditions

Un-utilized coal ash is commonly used as fill material for the construction of highway and railway embankment, which experiences different anisotropic stress conditions under different types of loading conditions. This study investigated the shear modulus of compacted coal ash under different anisotropic stress conditions simulating highway and railway embankment stress states. The small-strain shear modulus was obtained by performing the bender element tests under consolidation and shearing stages of consolidated undrained (CU) triaxial testing. The effect of different consolidation stress paths on the small-strain shear modulus of coal ash was evaluated using experimental data obtained from a bender element system affiliated with a stress-path controlled advanced triaxial setup. The small-strain shear modulus of coal ash at different ranges of mean effective stresses (at the end of consolidation) was also determined under various anisotropic stress conditions. The measured shear modulus (Gmax) of compacted coal ash under small-strain dynamic loading conditions was determined to be the function of mean effective stresses and deviatoric stress. At the later stage of shearing, the shear modulus was observed to attain a constant value subjected to large strain levels.

Effect of Anisotropic Consolidation on Response of Aggregates Subjected to Repeated Loading

Resilient modulus and permanent deformations are two important aspects which need to be considered in the design of pavements. The use of rollers in the field during pavement construction leads to a higher degree of compaction of material in the vertical direction which alters the properties of the base material used and contributes to stress-induced anisotropy. In this paper, the effects of stress-induced anisotropy on the properties of the granular material and the effect of loading on permanent deformation and resilient modulus, at different confining pressures and loading conditions, are discussed for both isotropically and anisotropically consolidated samples. The excess pore pressure patterns generated during the experiments are used to explain the behavior of both anisotropically and isotropically consolidated samples. It was observed from the studies that the properties of the anisotropically consolidated samples are superior to the results obtained for isotropically consolidated samples.

Effect of stress-induced anisotropy on high frequency magnetoimpedance effect of Fe and Co-rich glass-coated microwires

The influence of stress-annealing on the magnetic softness and the magnetoimpedance effect of Fe-and Co-based glass-coated microwires is studied. As-prepared Co-rich glass-coated microwires present better magnetic softness and rather higher magnetoimpedance ratio with a double-peak dependence, typical for materials with transverse magnetic anisotropy. As-prepared Fe-based microwires present a rectangular hysteresis loop with a coercivity an order of magnitude higher and a magnetoimpedance ratio of an order of magnitude lower. Stress-annealing of Co- and Fe-based glass-coated microwire allows considerable magnetoimpedance ratio increasing. The impact of stress-annealing is especially pronounced in a Fe-based microwire, where transverse magnetic anisotropy, large (an order of magnitude) improvement of the magnetic softness and magnetoimpedance ratio are observed.In Co-based microwire a magnetoimpedance ratio improvement for short annealing time and a change of hysteresis loop from linear to rectangular are observed. Observed stress-induced anisotropy and related changes of magnetic properties are discussed considering internal stresses relaxation and “back-stresses”.Obtained experimental results yield new and important insights into the influence of stress-induced magnetic anisotropy on the magnetoimpedance effect and hysteresis loops of glass-coated microwires.

Effect of stress-induced anisotropy on localized mode of one-dimensional photonic crystal with mirror symmetry

Using 4×4 transfer matrix method, the effect of stress-induced anisotropy on localized mode has been investigated. It is found that the change of the crystal thickness caused by stress, would leads localized modes to move linearly in the transmission spectrum. Further study confirmed that anisotropy causing by elastic-optic effect enhances or suppresses this effect.

应力各向异性对一维镜像光子晶体局域态的影响

应力各向异性对一维镜像光子晶体局域态的影响

Effect of Stress-Induced Anisotropy on the Noise of Ring-Core Fluxgate

In this paper, we show how an anisotropy perpendicular to the direction of excitation is favorable to obtain low noise in fluxgate sensors. We produced ring cores by electroplating NiFe thin film (6 μm) over a bended copper substrate. After the electroplating process, the sample was released and back-stress-induced anisotropy in the magnetic film due to magnetostriction of the material. As a result, we obtained rings with regions showing hard behavior and orthogonal regions showing soft behavior. Then, we used such rings as core for fluxgate and measured both noise and sensitivity for different orientation of the ring in the pick-up coil. When the pick-up coil covers the area with anisotropy perpendicular to the direction of excitation, the sensitivity is lower due to lower permeability, but finally, the noise is lower. On the other hand, rotating the core by 90°, the anisotropy becomes parallel to the direction of excitation and thus the sensitivity increases. Nevertheless, the noise also increases, showing that such anisotropy parallel to direction of excitation is unfavorable even if it brings higher sensitivity.

Studay on the Anisotropy of Clay

The development of stress-induced anisotropy in clay which was not only decided by the maximum stress endured before, but mainly lied on the stress route that reaching the maximum stress point of clay. The development or disappearance means of stress-induced anisotropy of normally consolidated clay, anisotropic consolidation clay and over-consolidated clay with different stress history are analyzed by experiments. Additionally, the effect of stress-induced anisotropy on deformation is also analyzed.

Pore-Pressure-Coefficient Anisotropy Measurements for Intrinsic and Induced Anisotropy in Sandstone

SummaryIn this study, we determine experimentally the effect of inherent and stress-induced anisotropy on stiffness components, elastic moduli, and Biot's pore-pressure coefficients (PPCs) for Lyons outcrop Colorado sandstone, which exhibits a clear transverse isotropic rock structure. Both dynamic and quasistatic methods were used under a nonhydrostatic state of stress to perform the measurements on dry core samples. Our assumption of apparent transverse anisotropy was confirmed initially with acoustic velocity measurements and at a later stage in the loading with experimental transverse anisotropic failure analysis. The objective of this study is to identify and isolate the effect of stress-induced anisotropy from the inherent transverse anisotropy on the measured stiffness components, elastic moduli, and Biot's PPCs. The effect of stress-induced anisotropy appears to have significant control on measured stiffness components, elastic moduli, and Biot's PPCs in comparison to the inherent-transverse-anisotropy effect. Our work shows that the stiffness components, Mij and thus the computed elastic moduli, are highly influenced by the stress-induced anisotropy, especially the off-diagonal stiffness components, M12 and M13, where the increase in their magnitudes from the dynamic measurements before failure is determined to be 100 and 81%, respectively. The difference in the magnitude between the axial and lateral Biot's PPCs in line with bedding planes and perpendicular to them is measured to be 24 and 16% from the quasistatic and dynamic methods, respectively; whereas, the effect of stress-induced anisotropy reduced the dynamic average magnitude of the Biot's PPCs along the bedding planes and transverse to these planes by 63% across a stress range of 145 MPa.

Low-field microwave magnetic permeability on FeSiBNbCu thin films

This work presents the dynamic and static magnetic properties of an 85 nm-thick amorphous thin film precursor of the well-known Finemet material, deposited by RF sputtering. Hysteresis evidences in-plane isotropic properties that are distinguished as contributions of hard and soft axis simultaneously. High-frequency permeability measurements were performed by using the network inductive method in the frequency range 100 kHz–1.8 GHz. The low-field FMR relation dispersion obtained from the permeability spectra shows peculiar properties, from which the effects of stress-induced anisotropy are discussed.

The effect of stress-induced anisotropy in patterned FeCo thin-film structures

In this work, 1-μm-thick FeCo films with −320MPa compressive stress and FeCo∕NiFe films with 600MPa tensile stress were patterned into 5×20μm2 elements. The stress anisotropy resulting from patterning was measured using x-ray diffraction to be 220MPa for the tensile films and −170MPa for the compressive films and is in agreement with finite element modeling. Scanning electron microscopy with spin-polarization analysis imaging shows that the domain structure of the elements was influenced by this stress-induced anisotropy. Calculations of the effect of stress anisotropy were performed on domain configurations for the patterned structures. Results indicate that tensile stresses should reinforce closure domains, while compressive stresses of magnitude greater than 50MPa should result in an easy axis rotation, and are in agreement with the experimental results.

Effect of Stress-induced Magnetic Anisotropy on the Properties of Giant Magnetostrictive Single Layer and Multilayer Thin Films

ABSTRACTGiant magnetostrictive thin films deposited on nonmagnetic substrates can constitute effective sensors and actuators for microdevices. In this work, we investigated the effects of a stress-induced anisotropy on the magnetic properties of Tb0.4Fe0.6, Fe0.5Co0.5 single layer films and [Tb0.4Fe0.6/Fe0.5Co0.5]n multilayers deposited on Si substrates. The magnetostrictive thin films were fabricated by means of RF sputtering and were subjected to a post-deposition annealing treatment. The uniaxial magnetic anisotropy was induced by bending the substrate before deposition and then allowing it to resume its original flat shape after depositing the film. The heat treatment was performed in a vacuum system with a vacuum of 10−6 Torr. The magnetic properties of the fabricated specimens were measured using a SQUID. SEM and XRD analyses were performed to ensure that the thermal treatment would relax the internal stresses induced during the deposition process without crystallizing the film. The thickness of the single layer thin films studied was between 300 and 800 nm while multilayer samples consisted of 6 layers with each layer thickness ranged from about 20 to 40 nm. Compared to single layer samples, multilayer samples with stress anneal growth exhibited an improvement in magnetic saturation by a factor of two while maintaining a low coercive field. Manipulations of the magnitude and direction of magnetic anisotropy was observed by introducing various values of tensile and compressive stress into the film.

Effect of stress-induced anisotropy and porosity on elastic properties of polycrystals

Recent ultrasonic measurements performed on hot-pressed polycrystalline materials as a function of pressure and temperature simultaneously indicate that the interiors of the specimens may not be strain free. Residual strain arising from the fabrication process produces an anisotropic effect separate from any anisotropy that may arise simply from relative grain orientations that may or may not be randomized. Internal strain has a significant effect on measurements of the bulk modulus and particularly of its pressure derivative. The effect of residual porosity and permeability on the pressure derivative of the bulk modulus is also examined.