Effect Of Shear Strain Research Articles

A numerical study on the effects of cavitation on orifice flow

Previous experimental studies have shown better atomization of sprays generated by high-pressure liquid injectors when cavitation occurs inside the nozzle. It has been proposed that the collapse of traveling cavitation bubbles increases the disturbances inside the liquid flow. These disturbances will later trigger the instabilities in the emerged jet and cause a shorter breakup distance. In this paper, effects of cavitation on increasing the disturbances in the flow through the orifice of an atomizer are studied. In previous cavitation models, spherical cavitation bubbles are considered. Here, the cavitation bubbles are allowed to deform as they travel through the orifice. Dynamics of the cavitation bubble, traveling in the separated shear layer in the orifice, is analyzed through a one-way coupling between the orifice flow and bubble dynamics. Effects of shear strain, normal strain, and pressure variation are examined. Three mechanisms are suggested that could be responsible for the increase in disturbances in the flow due to cavitation. These mechanisms are monopole, quadrupole, and vorticities generated during growth and collapse of cavitation bubbles. The effects of these mechanisms are estimated by postprocessing of the solutions to the Navier–Stokes equations to identify monopole and quadrupole behaviors.

Raman spectroscopy study of nitromethane in a shear diamond anvil cell

In addition to pressure and temperature effects, shear strain has been proposed to play an important role in the initiation and decomposition mechanisms of energetic materials. To study the effect of shear strain in more detail, a shear diamond anvil cell has been developed. In this paper, we present a Raman spectroscopy study of the effects of shear strain on the high-pressure behaviour of nitromethane (NM). Two major effects are observed in our experiments. The first one is a lowering of the pressures at which the different structural modifications of NM occur. The second one is observed at 28 GPa, where the sample decomposes suddenly just after shear application. Examination of the black residue showed that it is composed of carbon, as indicated by the Raman spectrum.

Effect of strain and oxygen vacancies on the structure of 180° ferroelectric domain walls in PbTiO3

Abstract In this paper, we study the effect of normal and shear strains and oxygen vacancies on the structure of 180° ferroelectric domain walls in PbTiO3. It is known that oxygen vacancies move to the domain walls and pin them. Hence, we assume a periodic arrangement of oxygen vacancies on both Pb-centered and Ti-centered domain walls in PbTiO3. We use a semi-analytic anharmonic lattice statics method for obtaining the relaxed configurations using a shell potential. In agreement with recent ab initio calculations, we observe that a Pb-centered domain wall with oxygen vacancies is not stable even under strain. Our semi-analytic calculations for PbTiO3 show that oxygen vacancies affect the structure of 180° domain walls significantly but do not have a considerable effect on the thickness of domain walls; they broaden the domain walls by about 50%. We also study the effect of normal and shear strains on both perfect and defective 180° domain walls. We observe that normal and shear strains affect the structure but do not change the domain wall thickness.

Phenomenological analysis of phase transitions in epitaxial perovskite ferroelectric thin films

A phenomenological Landau–Ginzburg–Devonshire theory is employed to investigate the effect of biaxial misfit strains and in-plane shear strain on thermodynamic equilibrium states and dielectric properties of single domain KNbO 3, BaTiO 3, and PbTiO 3 thin films. For KNbO 3 thin films grown on cubic substrates, the constructed isotropic misfit strain–temperature phase diagram is in qualitative agreement with the result from first-principle calculations. For BaTiO 3 and PbTiO 3, misfit strain–temperature phase diagrams at constant in-plane shear strains are constructed. In-plane shear strain is shown to restrain formation of a phase (polarization along [1 0 0]). The anisotropic misfit strain–temperature and misfit strain–misfit strain phase diagrams are also developed for KNbO 3 thin films grown on orthorhombic substrates. The anisotropic biaxial misfit strains lead to appearance of orthorhombic phases (a 1, a 2) and monoclinic phases (a 1c, a 2c).

Effect of Shear Strain on the Microstructural Evolution of a Low Carbon Steel during Warm Deformation

The microstructural evolution of a low carbon steel was investigated under two different conditions with and without shear strain, using electron backscattered diffraction (EBSD) when a uniaxial compression of 67% was applied at a warm working temperature of 773 K. The equivalent strain and shear strain imposed by the compression test were calculated quantitatively by finite element analysis (FEA). As the equivalent strain was increased without any shear strain, the texture of the α and γ fibers was strongly developed, and the grain refinement was accelerated. However, as the shear strain was increased at the same equivalent strain, the thickness of the pancaked ferrite decreased and the texture was weakened. With increasing shear strain, a shear texture, such as (110) // TD and {110} // ND, was observed and a high angle boundary over 15° developed at the expense of low and medium angle boundaries below 15°. The shear strain accelerated the subdivision of the ferrite grain and randomized the texture.

Shear Strain Influence on Fiber Bragg Grating Measurement Systems

Fiber Bragg grating (FBG) sensors have become commercially available sensors for the measurement of temperature, strain, and many other quantities. One interesting application is the embedding of these sensors, during which shear strains can arise inside the sensor. As we have recently demonstrated by a full-tensor coupled-mode analysis, shear strains do influence the spectral response of fiber Bragg sensors, and thus have to be considered. In this paper, we use the theory behind this analysis to compute the direct influence of shear strains on the output of a FBG measurement system, and show cases where shear strain effects are relevant. Furthermore, we compare the sensitivity of different interrogation algorithms toward shear strain influences on the measurement system output. To model the experimentally relevant unpolarized light sources, we derive a model using the monochromatic waves of coupled-mode theory. We apply the unpolarized light to the FBG shear strain problem and show that for unpolarized light, shear strain has to be taken into account as well. We find absolute measurement errors in the range of 100 pm. For typical normal strain measurements, this would be of an order of 10% of relative error.

Shear effects in lateral piezoresponse force microscopy at 180° ferroelectric domain walls

In studies using piezoresponse force microscopy, we observe a nonzero lateral piezoresponse at 180° domain walls in out-of-plane polarized, c-axis-oriented tetragonal ferroelectric Pb(Zr0.2Ti0.8)O3 epitaxial thin films. We attribute these observations to a shear strain effect linked to the sign change of the d33 piezoelectric coefficient through the domain wall, in agreement with theoretical predictions. We show that in monoclinically distorted tetragonal BiFeO3 films, this effect is superimposed on the lateral piezoresponse due to actual in-plane polarization and has to be taken into account in order to correctly interpret the ferroelectric domain configuration.

Transfer Matrix Approach to Four Mode Coupling in Fiber Bragg Gratings

Shear strain effects within fiber Bragg grating sensors have been neglected in the theoretical treatment of these devices. Shear strains do however occur in everyday applications and additionally shear strains do change the spectral response of these sensors. This may lead to a nonlinear behavior or measurement errors. We develop a transfer matrix method using coupled mode theory, that is capable of modeling the encountered effects. The effects include intra grating polarization mode coupling and changes of the spectral response. We show how the transfer matrix is derived and construct a test case for checking the correctness of its results. We compute different load cases and compare the obtained solutions to the numerically integrated coupled mode equations.

Borehole failure analysis in a sandstone under anisotropic stresses

AbstractBorehole failure under anisotropic stresses in a sandstone is analyze numerically for various borehole sizes using a nonlinear elastic–plastic constitutive model for a Cosserat continuum. Borehole failure is identified as macroscopic failure of the borehole through the development of shear bands and breakouts. The results compare well both qualitatively and quantitatively with experimental results from polyaxial tests on Red Wildmoor sandstone. They show that the hole size effect of the borehole failure strength is independent of the far‐field stress anisotropy and follows a ⅖ power law of the hole size. A similar scale effect equation with a ⅘ power law is proposed for the scale effect of the maximum plastic shear strain at failure. This equation can be useful for better predicting hole‐size‐dependent failure with standard codes based on classical continua. The effect of stress anisotropy on the borehole failure stress is found to be independent of the hole size. The failure stress decreases linearly to 40% as the stress anisotropy increases. However, the maximum plastic shear strain at failure is stress anisotropy independent and therefore the critical plastic shear strain for failure is only hole‐size dependent. Copyright © 2009 John Wiley & Sons, Ltd.

Principal component analysis of shear strain effects

Shear stresses are always present during quasi-static strain imaging, since tissue slippage occurs along the lateral and elevational directions during an axial deformation. Shear stress components along the axial deformation axes add to the axial deformation while perpendicular components introduce both lateral and elevational rigid motion and deformation artifacts into the estimated axial and lateral strain tensor images. A clear understanding of these artifacts introduced into the normal and shear strain tensor images with shear deformations is essential. In addition, signal processing techniques for improved depiction of the strain distribution is required. In this paper, we evaluate the impact of artifacts introduced due to lateral shear deformations on the normal strain tensors estimated by varying the lateral shear angle during an axial deformation. Shear strains are quantified using the lateral shear angle during the applied deformation. Simulation and experimental validation using uniformly elastic and single inclusion phantoms were performed. Variations in the elastographic signal-to-noise and contrast-to-noise ratios for axial deformations ranging from 0% to 5%, and for lateral deformations ranging from 0 to 5° were evaluated. Our results demonstrate that the first and second principal component strain images provide higher signal-to-noise ratios of 20 dB with simulations and 10 dB under experimental conditions and contrast-to-noise ratio levels that are at least 20 dB higher when compared to the axial and lateral strain tensor images, when only lateral shear deformations are applied. For small axial deformations, the lateral shear deformations significantly reduces strain image quality, however the first principal component provides about a 1–2 dB improvement over the axial strain tensor image. Lateral shear deformations also significantly increase the noise level in the axial and lateral strain tensor images with larger axial deformations. Improved elastographic signal and contrast-to-noise ratios in the first principal component strain image are always obtained for both simulation and experimental data when compared to the corresponding axial strain tensor images in the presence of both axial and lateral shear deformations.

Contact interface in seismic analysis of circular tunnels

The seismic analysis of underground structures requires a careful consideration of the important effect of shear strains in the soil due to vertically propagating horizontal shear waves. These strains result in ovaling deformations of circular tunnels or racking deformations of rectangular tunnels. Closed-form solutions as well as numerical analyses are used to characterize this soil-structure interaction problem. Many of these solutions assume full normal contact at the interface between the soil and tunnel lining. This work describes a numerical finite element study of soil-circular tunnel lining interaction with contact conditions that allow both limited slippage and separation to prevent development of potentially unrealistic normal tensile and tangential forces at the interface. The analyses highlight the significant limitations of widely used closed-form solutions in engineering practice. The finite element solutions demonstrate the need for realistic representation of the soil-tunnel interaction using numerical modeling approaches.

Effect of in-plane shear strain on phase states and dielectric properties of epitaxial ferroelectric thin films

A modified thermodynamic potential based on the eight-order Landau–Devonshire polynomial is derived for ferroelectric thin films grown on dissimilar substrates that induce anisotropic tensile/compressive strains and the shear strain in the film plane. The effect of the shear strain on the ferroelectric phase transition occurring in considered films is analyzed theoretically. It is shown that the application of the shear strain suppresses the formation of ferroelectric c phase and raises the temperature of aa∗ phase formation. The directional dependence of in-plane dielectric permittivity of a ferroelectric film is also calculated and compared with the dependence observed in (Ba0.60Sr0.40)TiO3 films deposited on NdGaO3.

Modal analysis of the thin-walled composite spoke of an umbrella-type deployable space antenna

Abstract The paper presents the solution of the problem of free vibrations of the composite spoke of a large-scale umbrella-type deployable space antenna. The spoke is modeled as the thin-walled orthotropic composite cantilever rod of circular cross section. The motion equations incorporate the effects of transverse shear strain and inertia of rotation of the rod’s cross section. The analytical solution is obtained and parametric analysis performed for various angles of the reinforcement orientation and length-to-diameter ratios. Using this solution, the optimum parameters of the composite spoke design are determined subject to constraints imposed on the natural frequencies.

Vibration analysis with second-order effects of pultruded FRP frames using locking-free elements

Vibrations of pultruded (FRP) thin-walled beams and frames are analysed. A second-order approximation of the displacement field is adopted, accounting for shear strain effects due to both nonuniform bending and torsion. Geometric nonlinearities arising from concentrated or distributed external loads are considered. A simple two-node finite element model using polynomial interpolation is adopted. In particular, the interpolating polynomials follow from the solutions to the homogeneous Timoshenko-beam problem and to the warping-torsion problem for a beam with doubly-symmetrical cross-section. Such shape functions contain parameters which tend to zero when the influence of shear deformations becomes negligible, resulting in a locking- free formulation. The convergence properties of the adopted element in the presence of flexural–torsional vibrations are highlighted with reference to mono-symmetrical cross-section carbon-FRP profiles. Vibration frequencies and mode shapes of pultruded glass-FRP portal frames are extensively evaluated as a function of the applied loads and sudden exchanges of fundamental modes are pointed out. The influence of frame geometry, shear deformations, participating masses and geometrical effects due to distributed external loads is investigated.

The Effect of Shear Strain on Transformation between Burr and Negative Burr

In most machining operations undersirable burr or negative burr is created at workpiece edges. The burr/negative burr formation mechanism is analyzed based on shear strain which is obtained from simulation results of the finite element model of burr/negative burr forming process. To varify the simulation results, experiments are conducted. We observered that there exists a critical value of shear strain for burr/negative burr transformation. Burr or negative burr, which to be formed at workpiece edges can be controlled by adjusting the cutting conditions or tool geometric parameters. Edge quality of workpiece can be controlled by converting burr or negative burr forming.

Shear-strain-induced low symmetry phase and domain ordering in epitaxial La0.7Sr0.3MnO3 thin films

The domain structure in epitaxial La0.7Sr0.3MnO3 films grown on (LaAlO3)0.3(Sr2AlTaO6)0.7(001) substrates has been investigated by x-ray reciprocal space maps on (003), (103), (1¯03), (013), and (01¯3) reflections in the high-resolution scattering zone containing the c* axis, and the transmission electron microscopy. We revealed that at above 20nm, the films show clearly a low symmetry monoclinic phase, and the shear strain relaxation can induce a patterned domain structure and in-plane superlattice in the films. The domain width versus the film thickness and the shear strain effect on the Curie temperature of the films were also discussed.

Effect of transverse shear strains on plates resting on elastic foundation using modified Vlasov model

A four-noded quadrilateral (PBQ4) and an eight-noded quadrilateral (PBQ8) plate bending element based on Mindlin plate theory are adopted for the analysis of thin and thick plates resting on elastic foundation using modified Vlasov model. The terms of vertical deflection stiffness matrix and shear deformation stiffness matrix of the subsoil are evaluated using finite element method, and presented in explicit forms. Selective reduced integration technique is used in addition to full integration technique for both the types of the elements to avoid shear-locking problem that occurs under the thin plate limit. It has been demonstrated that the performance of the eight-noded quadrilateral element is excellent for thin and thick plates on elastic foundation when selective-reduced integration technique is used. General conclusion can be drawn from the results that the effect of the shear strain on the behavior of the plate resting on subsoil is always quite small for free plates compare to the supported ones.

Deformation analysis of a film-overlapped micro-pump membrane structure

A novel approach is developed to study a film-overlapped membrane structure. Meanwhile,the established model is employed to design the micro-pump membrane structure and toevaluate its pumping efficiency. Two-dimensional coupling effects between the overlappingactuator films and the deformable membrane are thoroughly investigated, including theinfluences on the membrane from the overlapping films’ elongation effects, Poisson’s ratioeffects and shear strain effects. Overall deformations and interactions for the three-layermembrane structures are accurately calculated through exercising the developed model, incontrast to what difficulties are usually encountered in carrying out FEM methodswith very thin elements meshed for the actuator films. Furthermore, this studydemonstrates that the high stiffness of the actuating metal films needs to be reflected inthe equivalent stiffness of the membrane structures, especially when the sizes ofthe actuator films become compatible with the sizes of the membranes. Hence,the optimal micro-pumping efficiency of a membrane structure is acquired uponexercising the developed model, and larger sizes of the actuating films do notdefinitely obtain larger pumping efficiencies for the electromagnetically actuatedmicro-pumps.

The Effects of Temperature Cyclic Loading on Lead-Free Solder Joints of Wafer Level Chip Scale Package by Taguchi Method

In this study, the effects of the temperature cyclic loading on three lead-free solder joints of 96.5Sn–3.5Ag, 95.5Sn–3.8Ag-0.7Cu, and 95.5Sn–3.9Ag-0.6Cu bumped wafer level chip scale package (WLCSP) on printed circuit board assemblies are investigated by Taguchi method. The orthogonal arrays of L16 is applied to examine the shear strain effects of solder joints under five temperature loading parameters of the temperature ramp rate, the high and low temperature dwells, and the dwell time of both high and low temperatures by means of three simulated analyses of creep, plastic, and plastic-creep behavior on the WLCSP assemblies. It is found that the temperature dwell is the most significant factor on the effects of shear strain range from these analyses. The effect of high temperature dwell on the shear strain range is larger than that of low temperature dwell in creep analysis, while the effect of high temperature dwell on the shear strain range is smaller than that of low temperature dwell in both plastic and plastic-creep analyses.

Modeling of sensor function for piezoelectric bender elements

An analytical sandwich beam model for piezoelectric bender elements is derived based on the first-order shear deformation theory (FSDT), which assumes a single rotation angle for the whole cross-section and a quadratic distribution for coupled electric potential in piezoelectric layers. Shear coefficient is introduced to correct the effect of transverse shear strain on shear force and the electric displacement integration. Static and free vibration analyses of simply-supported bender elements are carried out for the sensor function. The results illustrate the high accuracy of the present model compared with the exact 2D solutions.