Shear Coupling Effect Research Articles

An experimental and numerical study on the coupling effect of CLT wall-to-floor angle bracket connections

Cross-laminated timber (CLT) wall panels are commonly connected to the floor or foundation using metal connections, which play a critical role in determining the seismic performance and energy dissipation of the CLT shear walls. In this study, to comprehend the tension–shear coupling effect of the CLT wall-to-floor angle bracket connections under seismic loads, both monotonic and cyclic shear tests were conducted on the angle brackets that were also simultaneously applied with different levels of prescribed vertical axial tension. The influence of the co-existent axial tension on the horizontal shear performance of the angle brackets was analyzed. Furthermore, a numerical model of the angle brackets was developed and validated with the experimental results, which could predict the tension–shear coupling effect based on the monotonic loading scenario. Based on the numerical model, parametric analysis was conducted, and an analytical tension–shear interaction diagram representing the coupling effect of the angle brackets under seismic loads was established. It is found that with an increase of the axial tension from 0 to 30 kN, the shear resisting capacity of the angle brackets is diminished by 33.29%, and the pinching effect of their hysteretic load–displacement curves is mitigated. When the number of the connection-to-floor screws of the angle brackets was increased from 10 to 14, the shear resisting capacity of the angle brackets can be enhanced by 6.43%, and their shear strength degradation can be relieved by 12.85–56.25%. For the CLT wall-to-floor angle brackets, the analytical interaction diagram can be described using one bilinear function, which consists of the ratio between the shear to the shear resistance and the ratio between the tension to the pull-out resistance.

Chiral-based mechanical metamaterial with tunable normal-strain shear coupling effect

Different designs for mechanical metamaterials with tunable normal-strain shear coupling effect have been demonstrated over the last years. Their adjustable shear deformation makes them suitable as building blocks for soft robotics applications or structures with a desired deformation behavior, such as shape morphing structures. Herein, we present a modified 2.5D and 3D chiral-based mechanical metamaterials with tunable normal-strain shear coupling effect and Poisson’s Ratios close to zero. Advancing from conventional chiral-based metamaterials by introducing additional geometric freedoms into the design of the unit cell, a broad range of shear deformations, compression moduli and porosities can be achieved. 2.5D specimens with selected geometric parameters were additively manufactured with polypropylene using Fused Filament Fabrication. Compression tests were performed to investigate the mechanical properties and shear deformation. Two different numerical models were employed using ABAQUS to study the influence of the geometric parameters onto the mechanical properties and were verified by the experiments. The numerical material models were based on three-point-bending test data. The three-dimensional design was investigated with numerical simulations based on a homogenization approach to cover a broad range of geometric parameters.

Effects of handedness ratio and handedness distribution on the mechanical properties of Bi-chiral mechanical metamaterials

The elastic mechanical properties of bi-chiral mechanical metamaterials are explored via systematic finite element simulations. Designs of bi-chiral mechanical metamaterials with both periodic and complete random handedness distributions for various handedness ratio and domain size and length aspect ratios were investigated. It is found that in general, because of the interactions at the ‘twinned’ intercellular boundaries between neighboring domains, the handedness ratio, handedness distribution, domain size and length aspect ratio significantly influence the overall mechanical properties of bi-chiral designs. Specifically, when handedness ratio increases and domain size decreases, the effective stiffness and the auxetic effects increases, while the effective shear modulus is much less sensitive to either the handedness ratio or the domain size. The chirality-induced normal shear coupling effect is solely determined by the handedness ratio. An empirical mechanical model was proposed to quantify the influences of ‘twinned’ intercellular boundaries on the effective stiffness and effective Poisson’s ratio of bi-chiral designs. In addition, both upper and lower limits of the effective stiffness and the effective Poisson’s ratio of bi-chiral designs are identified.

Micropolar homogenization of wavy tetra-chiral and tetra-achiral lattices to identify axial–shear coupling and directional negative Poisson's ratio

Chiral lattices are generally considered to possess auxetic properties with negative Poisson's ratios and high compressibility. However, the effects of anisotropy and handedness (chirality) on their mechanical properties, such as directional moduli, Poisson's ratio, and other coupling effects, are not clearly understood due to the lack of analytical methods to handle both anisotropy and chirality. Herein, we construct a generalized micropolar homogenization method to characterize the elastic constants of tetra-chiral and tetra-achiral lattices having different joint types. The developed method can identify the directional moduli and Poisson's ratio and coupling effects in the anisotropic wavy lattices. The generalized micropolar homogenization of the wavy square lattices reveals i) the axial–shear coupling effect of tetra-chiral structures, ii) the weak correlation of the chirality of tetra-chiral lattices to auxeticity, and iii) the directional positive and negative Poisson's ratio of tetra-achiral lattices. This work offers a powerful platform for metamaterials' design via geometric reconfiguration of lattice structures to adjust both anisotropy and chirality.

Three-dimensional elasto-plastic damage model for gravelly soil-structure interface considering the shear coupling effect

The gravelly soil-structure interface was observed to exhibit a significant coupling effect among the orthogonal shear directions due to the three-dimensional shear application in different experimental investigations, which governs major three-dimensional features of the interface. In this paper, initially, a three-dimensional modeling framework is established based on the analyses of interface behavior under different shear coupling conditions. A series of concepts and assumptions are derived in this framework, banking on which a three-dimensional model scheme is proposed by reasonably modeling the shear coupling effect. Afterward, a three-dimensional elasto-plastic damage interface model is developed based on the proposed model scheme and modified formulations of a previous two-dimensional EPDI model. Only a single new parameter is introduced in the three-dimensional shear stress-strain relationship modeling scheme to quantify the three-dimensional shear response of the interface besides already known parameters of the EPDI model. The model can simulate the monotonic and cyclic response of interface along two and three-dimensional shear paths in a unified manner. The performance of the model is validated based on test data from the literature. The model can capture different essential features of the gravelly soil-structure interface behavior under three-dimensional conditions, e.g., coupling effect, volumetric change behavior and aeolotropy.

A generalized bond-based peridynamic model for quasi-brittle materials enriched with bond tension–rotation–shear coupling effects

A generalized bond-based micropolar peridynamic model is proposed to simulate the nonlinear deformation and mixed-mode crack propagation of quasi-brittle materials under arbitrary dynamic loads. The mechanical behaviors of the material points are reformulated by incorporating the bond tension–rotation–shear coupling effects, which makes the model suitable for complex discontinuous problems in both three-dimensional spatial and two-dimensional plane conditions. The governing equations of the bond are established by employing the Timoshenko beam theory to simulate the interaction between material points as well as the bond coupling effect. Three kinds of peridynamic parameters, corresponding to the compressive, shear and bending stiffness of the bond, are introduced to keep the consistence of the strain energy obtained from the proposed peridynamic model and from the continuum mechanics under arbitrary deformation fields. Moreover, a novel energy-based failure criterion, involving the maximum stretch, shear strain and rotation angle limits of the bond, is proposed to describe the nonlinear behaviors and progressive failure for general quasi-brittle materials. The proposed model is verified by providing comparisons between its results and those from known analytical solutions and experimental observations. The influences of the bond tension–rotation–shear coupling effect as well as the applicability of the proposed model for the wave propagation, complex deformation and mix-mode fracture problems are also investigated. Results show that the proposed model with the bond coupling effect will greatly improve the simulation accuracy for dynamic problems of quasi-brittle materials under complex loading conditions. Results also indicate that the proposed model can well capture the nonlinear deformation, crack propagation, as well as progressive failure of materials with variable Poisson’s ratios under complex combined loads

Shear coupling effect of monotonic and cyclic behavior of the interface between steel and gravel

Three-dimensional behavior of the interface between a structure and gravelly soil is of great concern in the design and construction of large-scale projects. A series of three-dimensional tests were conducted to investigate the effect of shear coupling on the monotonic and cyclic behavior of such an interface. In these tests, monotonic shear was applied to the interface first and then the monotonic and cyclic shears were applied in the orthogonal direction while the original shear was maintained. Based on the test observations, the shear strength of the interface was found to be independent of the shear coupling and proportional to the normal stress. Significant tangential displacement is induced by the orthogonal shear application and the deflection direction of the tangential displacement is proportional to the square of the ratio between the orthogonal shear stress and shear strength. The interface exhibits significant dilatancy due to a three-dimensional shear application, which is divided into reversible and irreversible components. Shear coupling remarkably affects the magnitude and transition shear stress of the reversible dilatancy component. There persists a significant aeolotropy of the interface evenly under the shear coupling condition. Particle crushing near the structure was observed to be enhanced due to the shear coupling.

Equivalent stiffness prediction and global buckling analysis using refined analytical model of composite laminated box beam

Abstract The analytical model applicable to calculate the equivalent stiffnesses of composite box beam has been refined. The calculation of equivalent stiffness coefficients of composite laminated box beam is simplified and the connection between shear-deformable beam theory and classical laminate theory is established. The equivalent stiffness analytic formulas expressed by beam cross-section geometry and laminate stiffness coefficients are obtained. These analytical formulas are suitable for composite laminated box beam with circumferential uniform stiffness, and accounts for bending- transverse shear and torsiontensile coupling effect. The correctness and precision of refined analytical model is verified by test and finite element method, respectively. The influences of the lay-ups on the elastic coupling of composite structures and their causes are studied. The variation of the equivalent stiffnesses of the laminated box beams with different lay-ups is predicted. The global buckling analysis of composite laminated box beam considering the transverse shear deformation is carried out. The formula of the global buckling critical load is obtained combining with the theoretical formulas of equivalent stiffnesses. The influences of the lay-ups, shear deformation and slenderness ratio on the global buckling critical load are studied.

Influence of tension–shear coupling on draping of plain weave fabrics

Although tension–shear coupling of weave fabrics in large deformation has been observed in experiments, most constitutive models for weave fabrics often ignore this coupling effect for simplicity. In this paper, a nonlinear anisotropic hyperelastic constitutive model is proposed to consider this tension–shear coupling effect. Draping experiments of a plain weave fabric over a tetrahedron mold are carried out to validate the proposed coupling constitutive model. Subsequently, the influences of tension–shear coupling on draping processes are investigated. Numerical simulation results indicate that the tension–shear coupling effect significantly changes fiber reorientation during draping process, which makes shear deformation tend to be uniform and reduces the local shear deformation concentration and should not be neglected in woven fabric stamping with salient double curvatures.

Compression–shear coupling rheological constitutive model of the deep-sea sediment

ABSTRACTIn deep-sea mining engineering, the compression–shear coupling effect of the sediment on the moving tracked mining vehicle must be considered, since it is proved to be existing in compression–shear creep test of the sediment simulant. Based on the endochronic theory, the compression–shear coupling rheological model is established by the definition of intrinsic time and calculation of deviatoric tensor, where the coupling rheological parameters can be obtained by the compression–shear creep test. For simulating sinkage and traction force of the moving tracked mining vehicle, the compression–shear coupling rheological model as well as compressive rheological model and direct shear rheological model (regardless of coupling rheological effect) is programmed and introduced into RecurDyn software (with only traditional elastic–plastic constitutive model) for comparison. Research results show that the sinkage is the largest, and the traction force is the smallest under the compression–shear coupling rheological model, which could better reflect the worse working situation. The compression–shear coupling rheological model could provide theoretical basis for optimal design and safety assessment of the tracked mining vehicle.

Anisotropic Continuum Stored Energy Functional Solved by Lie Group and Differential Geometry

An anisotropic continuum stored energy (CSE), which is essentially composed of invariant component groups (ICGs), is postulated to be balanced with its stress work done, constructing a partial differential equation (PDE). The anisotropic CSE PDE is generally solved by the Lie group and the ICGs through curvatures of elasticity tensor are particularly grouped by differential geometry, representing three general deformations: preferred translational deformations, preferred rotational deformations, and preferred powers of ellipsoidal deformations. The anisotropic CSE constitutive models have been curve-fitted for uniaxial tension tests of rabbit abdominal skins and porcine liver tissues, and biaxial tension and triaxial shear tests of human ventricular myocardial tissues. With the newly defined second invariant component, the anisotropic CSE constitutive models capture the transverse effects in uniaxial tension deformations and the shear coupling effects in triaxial shear deformations.

Zener Pinning of Grain Boundaries and Structural Stability of Immiscible Alloys

Immiscible Cu-Ta alloys produced by mechanical alloying are currently the subject of intensive research due to their mechanical strength combined with extraordinary structural stability at high temperatures. Previous experimental and simulation studies suggested that grain boundaries (GBs) in Cu-Ta alloys are stabilized by Ta nano-clusters coherent with the Cu matrix. To better understand the stabilization effect of Ta, we performed atomistic computer simulations of GB–cluster interactions in Cu-Ta alloys with various compositions and GB velocities. The study focuses on a single plane GB driven by an applied shear stress due to the shear-coupling effect. The results of the simulations are in close quantitative agreement with the Zener model of GB pinning. This agreement and the large magnitude of the unpinning stress confirm that the structural stability of these alloys is due to the drastically decreased GB mobility rather than a reduction in GB energy. For comparison, we simulated GB motion in a random solid solution. While the latter also reduces the GB mobility, the effect is not as strong as in the presence of Ta clusters. GB motion in the random solution itself induces precipitation of Ta clusters due to short-circuit diffusion of Ta in GBs, suggesting a possible mechanism of cluster formation inside the grains.

Shear coupling effects of the core in curved sandwich beams

We consider a composite package formed by two curved external Euler-Bernoulli beams, which sandwich an elastic core with negligible bending strength but providing the shear coupling of the external layers. This coupling considerably affects the gross response of the composite structure. There is an extensive literature on straight sandwich beams of this type, but very little attention has been paid to the effects of curvature. Here, an analytical linear elastic model is proposed for beams with arbitrary variable curvature. Equilibrium equations and boundary conditions are obtained through a variational approach. Useful simplifications are possible for the case of moderately curved beams and beams with constant curvature.

Ballistic Performance of Laminated Composite with TiB<sub>2</sub> Based Ceramic to Ti-6Al-4V Alloy in Continuously-Graded Microstructure

Laminated composite of TiB2 based ceramic to Ti-6Al-V alloy in graded microstructure were achieved by combustion synthesis in ultra-high gravity field. XRD and FESEM results showed the presence of the graded microstructures at the joint which was characterized by multilevel (TiC1-x-TiB-TiB2 + TiB2-Ti-TiC1-x-TiB + TiB2-TiC1-x-TiB-Ti + TiB-TiC1-x-Ti + TiC1-x-Ti) and multiscale (micro-submicro-nano) of the size and the distribution of TiB2 phases and TiB phases. It was considered that liquid fusion, atomic interdiffusion and a series of metallurgical reaction during solidification were reasoned for the continuously-graded microstructure from the ceramic to Ti alloy. Ballistic mass effectiveness coefficients of TiB2 based ceramic and the laminated composite with TiB2 based ceramic to Ti alloy were calculated to be 3.25 and 7.35 respectively by DOP test. The continuously-graded microstructures at the joint from the ceramic to Ti ally was considered to effectively reduce acoustic impedance mismatch between the ceramic and the metal, resulting in the enhanced ballistic performance of the target against the projectile by initiating intensive shear coupling effect.

Coupled polynomial field approach for elimination of flexure and torsion locking phenomena in the Timoshenko and Euler–Bernoulli curved beam elements

The curvature related locking phenomena in the out-of-plane deformation of Timoshenko and Euler–Bernoulli curved beam elements are demonstrated and a novel approach is proposed to circumvent them. Both flexure and Torsion locking phenomena are noticed in Timoshenko beam and torsion locking phenomenon alone in Euler–Bernoulli beam. Two locking-free curved beam finite element models are developed using coupled polynomial displacement field interpolations to eliminate these locking effects. The coupled polynomial interpolation fields are derived independently for Timoshenko and Euler–Bernoulli beam elements using the governing equations. The presence of penalty terms in the coupled displacement fields incorporates the flexure–torsion coupling and flexure–shear coupling effects in an approximate manner and produce no spurious constraints in the extreme geometric limits of flexure, torsion and shear stiffnesses. The proposed coupled polynomial finite element models, as special cases, reduce to the conventional Timoshenko beam element and Euler–Bernoulli beam element, respectively. These models are shown to perform consistently over a wide range of flexure-to-shear (EI/GA) and flexure-to-torsion (EI/GJ) stiffness ratios and are inherently devoid of flexure, torsion and shear locking phenomena. The efficacy, accuracy and reliability of the proposed models to straight and curved beam applications are demonstrated through numerical examples.

Functional gradient effects explain the low transverse shear modulus in spruce – Full-field strain data and a micromechanics model

An important failure mechanism in glulam beams is cracking caused by out-of-plane transverse loads. It has been demonstrated that the low transverse shear modulus G RT in spruce contributes to large transverse strain inhomogeneities due to the annual ring structure in combination with shear coupling effects. In the present study, improved understanding of annual ring effects is achieved by the development of a micromechanical model. It relates the functional density gradient in spruce annual rings to shear modulus G RT . The geometrical basis is a hexagonal cell model, and in shear it is demonstrated to deform primarily by cell wall bending. Full-field strain measurements by digital speckle photography (DSP) show very strong correlation with predicted shear strains at the annual ring scale. Predictions are obtained by implementation of the micromechanics model in a finite element (FE) model developed for the single cube apparatus shear specimen. The low G RT of spruce is due to the strong dependence of G RT on relative density ρ / ρ s ( G RT ∝ ( ρ / ρ s ) 3 ) . This is particularly important in spruce. Even though average density is typically quite high, the functional gradient structure includes local densities as low as 200 kg / m 3 .

Shear coupling effects on stress and strain distributions in wood subjected to transverse compression

The mechanical behaviour of a wood board subjected to transverse compression is relevant to the performance of glulam beams and solid wood structures. The wood material can be described as polar orthotropic, due to the annual ring structure and to the differences in moduli in different directions in the radial–tangential plane. Strain measurements are performed on single wood boards using a whole-field digital speckle photography technique. Finite element analysis is performed and compared with experimental data. Good agreement in terms of strain fields and apparent moduli is observed between predictions and data. The experimental data show strong variations in local strain due to the polar orthotropic behaviour of wood in this plane, and the extremely low value for shear modulus G rt as compared with the other moduli. This leads to shear coupling effects resulting in large local shear deformation and correspondingly low effective stiffness under transverse global loading.

Analysis of Locally Irregular Composites Using High-Fidelity Generalized Method of Cells

The generalized method of cells is a micromechanics model that is generally quite accurate at the macrolevel but not always accurate at the microlevel. This is due to the absence of so-called shear coupling, which provides the required bridge between macroscopically applied normal (shear) stresses and the microscopic shear (normal) stresses necessary for an accurate estimate of microlevel quantities. To overcome this deficiency, a new micromechanics model has been developed for the response of multiphase materials with arbitrary periodic microstructures, named high-fidelity generalized method of cells in part because it employs the same microstructural discretization as the original generalized method of cells. The model's framework is based on the homogenization theory, but the method of solution for the local fields borrows concepts previously employed in constructing the higher-order theory for functionally graded materials, in contrast with the typical finite element-based solution strategies. The model generates the average stress-strain response of heterogeneous materials such as ceramic, metal, and polymeric matrix composites, as well as the internal or microlevel stress and strain fields, with excellent accuracy. The model is employed to investigate the response of a metal matrix composite with locally irregular, but periodic, fiber distributions, and it is shown that irregular architectures affect shear and normal stress-strain response in a different manner. The new model's ability to capture these differences is attributed to the shear-coupling effect absent in the original model.

厚肉フィラメントワインディングパイプの構造解析

The stress distribution of anisotropic multilayer filament-wound composite pipes was analyzed. Based on the three-dimensional anisotropic elasticity and the classical laminated-plate theory, exact elastic solutions of stress and deformation were presented for the filament-wound pipes subjected either to internal pressure, axial force or torsion. The shear coupling effect is considered in the analysis. The influence of winding angle and winding sequence on stress distribution in pipes was investigated. The ratio of hoop-to-axial stress is 2:1 in orthotropic pipes; however, the ratio proved to be not 2:1 in anisotropic pipes due to the coupling effect. The stress and deformation of filament-wound pipes strongly depend on the winding angle and the winding sequence.

ON THE BEHAVIOUR OF FLUID-LOADED SANDWICH PANELS WITH MEAN FLOW

This paper considers a fluid-loaded sandwich panel, made up of layers of relatively rigid skin material surrounding a layer of less dense core material, with an unsteady point driver in steady mean flow. For a simple plate Brazier-Smith and Scott, and Crighton and Oswell predicted a number of unusual phenomena, including absolute instability, a neutral mode with its group velocity pointing towards the driver, and negative energy waves. The possible occurrence of these phenomena for realistic parameter values is considered. It is shown that absolute instability is unlikely to be found at normal speeds, but in contrast the anomalous propagation mode is present, although over a limited frequency range. It is shown that the negative energy waves could also well occur in practice. Study of both the full dispersion relation and asymptotic analysis demonstrate that at very low frequencies it is the ratio of core to skin stiffnesses and the flow speed which control the dynamics, but at higher frequencies shear coupling and rotational effects become important as well. Consideration of the relative magnitudes of the energy fluxes leads to the unexpected conclusion that for predominantly shear waves more energy is carried in the fluid than is carried in the plate.