Influence Of Shear Strain Research Articles

Method for strain tensor reconstruction with embedded fiber Bragg grating sensors

Fiber Bragg grating (FBG) sensors are being considered for health and conditionmonitoring of composite structures, where they may be embedded inside thematerial during the fabrication process. So far, research efforts have been directedtowards reconstruction of the strain tensor inside the material at the position of theFBG, using FBGs in polarization-maintaining fibers. However, the influence ofshear strains on the signals reflected from the FBG has hindered attempts toaccurately reconstruct the strain tensors. In this work, we employ a theoreticaldescription of FBGs which also describes the influence of shear strain. We proposean algorithm which, based on this underlying theory, allows for reconstructingthe principal strains, as well as the shear strain components. Further, we testthe algorithm on simulation data with noise levels comparable to those found inreal applications. Finally, we demonstrate the feasibility of the algorithm and itslimitations.

Electron subband structure in strained silicon UTB films from the Hensel–Hasegawa–Nakayama model – Part 1 analytical consideration and strain-induced valley splitting

Multi-gate FinFETs and ultra-thin silicon body SOI FETs are considered as perfect candidates for future technology nodes. Strong size quantization leads to a formation of quasi-two-dimensional subbands in carrier systems within thin silicon films. The employed Hensel–Hasegawa–Nakayama k·p Hamiltonian accurately describes the bulk structure up to the energies of 0.5–0.8eV and includes a shear strain component. Shear strain is responsible for effective mass modification and is therefore an important source of the electron mobility enhancement in ultra-thin silicon films. The influence of shear strain on the subband structure in thin silicon films is investigated.

Influence of shear strain on the hydrogen trapped in bcc-Fe: A first-principles-based study

To advance our understanding of hydrogen-related fractures of metals and alloys, it is essential to understand the influence of lattice defects and stress on the hydrogen existence state and its concentrations. In this study, we use density functional theory and interatomic potential to clearly show that shear strain in body-centered cubic Fe yields strong hydrogen trap energy, comparable to that of volumetric strain.

Shear strain-induced changes in liquid crystal alignment monitored by planar array infrared spectroscopy

Planar array infrared (PAIR) spectroscopy was applied to the study of the orientational motions of liquid crystals (LCs) under the influence of shear strain. Due to the ability to simultaneously monitor spectral bands corresponding to transition moments oriented along different directions along the molecular axes, it is possible to unambiguously determine the motion of the nematic director under the influence of external stimuli. Unlike previous attempts at spectroscopic studies of shear-induced liquid crystal orientation, PAIR is able to study the samples in real time, without the need to continuously subject the samples to cyclic perturbation. Of the three classical geometries employed in the rheological study of LCs, it was found that only one produced a measurable spectroscopic signal. This geometry was further explored by constant shear rate experiments over a range of shear rates and by exposing the samples to electric fields of varying strengths during shearing. The results obtained were seen to agree qualitatively with theoretical predictions.

The influence of shear strain and hydrostatic stress on stability and elastic waves in a layer

The theory of incremental motions superimposed on a large static deformation of an elastic solid is used to investigate the propagation of infinitesimal waves along a layer of material of uniform finite thickness. The layer is subject to an underlying simple shear deformation accompanied by an arbitrary uniform hydrostatic stress. In respect of a general form of incompressible, isotropic elastic strain-energy function, the dispersion equation for infinitesimal waves is obtained for two different sets of incremental boundary conditions on the faces of the layer. When the wave speed vanishes the dispersion equation becomes a bifurcation equation, which identifies configurations in which quasi-static incremental deformations can first appear on a path of simple shearing and hydrostatic stressing from the natural (undeforformed, unstressed) configuration of the layer. Explicit bifurcation criteria are obtained for a general form of strain-energy function and their consequences are illustrated by numerical results showing the dependence of bifurcation on certain deformation, stress and layer-thickness parameters. For a particular class of strain-energy functions, dispersion equations are obtained in explicit form for both incremental boundary-value problems, and the dependence of the wave speed on the same parameters is illustrated in detail.

Influence of shear strain on magnesium impurity atom distribution in aluminum

An aluminum crystallite containing 500 atoms with an effective dual interaction potential computed within the framework of the theory of pseudopotential was modeled by using the method of molecular dynamics. The binding energies of complexes from impurity magnesium atoms and vacancies as well as the migration activation energies (MA) of the magnesium and aluminum atoms were computed under shear strain conditions. It is shown that shear strain results in separating out of the individual directions energetically most favorable for the formation of complexes of impurity atoms and vacancies, as well as the directions in which the MA energy values are lowered.

Influence of shear strain, as a pre-deformation, on the subsequent mechanical properties of A-K steel

Low-carbon steel sheet has been subjected to two-stage straining: an initial planar simple shear pre-strain in three directions (0, 45 and 90 degrees to the rolling direction), followed by subsequent tensile strain at a range of orientations with respect to the initial shear direction. The experimental results show that the changes in the direction of straining have considerable influence on the mechanical behaviour of the material. When the angle between the direction of the pre-shear and the direction of the subsequent tensile test is equal to zero or 90 degrees, the pre-strain produces a latent hardening, the yield stress increases and the work-hardening rate decreases in the subsequent tensile test: thus premature instability occurs. However, when this angle is equal to 45 degrees, the flow-stress decreases and the ductility increases. The anisotropy of the material is also found to be an important factor influencing the mechanical behaviour in the subsequent tensile test.

Viscous properties of solutions of cellulose and its derivatives in the mixture methylmorpholine-N-oxide plus dimethyl sulphoxide

The viscous properties of solutions of wood cellulose have been investigated in the mixture methylmorpholine-N-oxide with DMSO and of cellulose triacetate (CTA) with different degrees of polymerization in DMSO and the mixture methylmorpholine-N-oxide with DMSO over a wide range of shear stresses, concentrations and temperatures. The values of the apparent activation energy of the viscous flow of cellulose and CTA solutions have been calculated. The influence of shear strain, temperature, concentration, the naure of the polymer and the composition of the solents on the advent and destruction of the fluctuation network of hydrogen bonds in solutions of cellulose and its derivatives has been shown.

Structure and Strength Characteristics of Compacted Clays

The influence of soil structure on shrinkage, swelling, swell-pressures, stress-deformation characteristics, undrained strength, pore-water pressures and effective strength characteristics is described and examples of the relationships between composition and the 'as-compacted' strength of compacted clays are presented. The influence of shear strain on soil structure is demonstrated and used to explain the effect of various methods of compaction on soil strength characteristics.