Effect Of Shear Strain Research Articles

Enhancement of liquid-solid mixing and particle hydrophobization by an impeller-less flotation pulp conditioning device

An impeller-less device was proposed to employ opposite rotational jet flows conditioning pulp before flotation. The flow field characteristics and relevant effects on the liquid-solid mixing performance were investigated by the numerical simulation of computational fluid dynamics that was proved effective by the particle image velocimetry technique. The outcome of particle surface modification was clarified by variations in the contact angle and surface species of quartz particles. Results showed that the increase of turbulent kinetic energy induced by the opposite rotational flows remarkably improved the dispersion of mineral particles. Smaller particle size and larger circulation rate were conductive to a more uniform distribution of particles. In the case of a volume flow of 3.6 m3/h and a feed volume fraction of 7 % with an average particle size of −45 μm, nearly 4/5th of the whole device area exhibits a particle volume fraction within the range of 6 % and 7 %, and the coefficient of variation was as low as 0.151. Meanwhile, strong turbulence and high shear induced by opposite rotational flows provided favorable conditions for the collector adsorption and particle hydrophobization, which was responsible for the increase in contact angle under relatively higher volumetric flow rates. However, when the volume flow exceeded 3.0 m3/h, over-increasing shear stresses and excessive turbulence caused the desorption of adsorbed collectors, reflected as the decreased nitrogen content on quartz surfaces from 0.85 % to 0.51 %, thereby accounting for the declined contact angle of conditioned quartz particles. This study highlighted the dominant effect of turbulence and shear strain on particle surface modification, and the significance of proper parameter control.

Atomistic assessment of structural evolution for magnesium during hypervelocity nanoprojectile penetration.

In the present study, investigating the effect of ballistic penetration of spherical projectiles on a monocrystalline magnesium specimen is performed using embedded atom method (EAM) potential in molecular dynamics (MD) simulation. The dynamic investigations of structural evolution based on common neighbor analyses and Wigner-Seitz defect analysis are carried out for the varying depths of penetration and velocities of the projectile (v = 2kms-1, 6kms-1, and 10kms-1). It is found that the extent of amorphization in the specimen is more in the case of higher depth and lower projectile velocity. Voronoi cluster analyses are also done to identify cluster distribution and their transformation during ballistic penetration, which is accompanied by atomic strain and displacement vector evaluation to give light to the effect of shear strain and displacement of atoms respectively. According to Voronoi cluster analysis, Voronoi polyhedra having < 0, 4, 4, 6 > and < 0, 6, 0, 8 > clusters exhibit a higher population during hypervelocity projectile penetration. The findings have potential applications in hypervelocity applications such as defense and space technologies.

Understanding the Semiconducting-to-Metallic Transition in the CF2Si Monolayer under Shear Tensile Strain

With the ever-increasing interest in low-dimensional materials, it is urgent to understand the effect of strain on these kinds of structures. In this study, taking the CF2Si monolayer as an example, a computational study was carried out to investigate the effect of tensile shear strain on this compound. The structure was dynamically and thermodynamically stable under ambient conditions. By applying tensile shear, the structure showed a strain-driven transition from a semiconducting to a metallic behavior. This electronic transition’s nature was studied by means of the electron localization function index and an analysis of the noncovalent interactions. The result showed that the elongation of covalent bonds was not responsible for this metallization but rather noncovalent interactions governing the nonbonded bonds of the structure. This strain-tuned behavior might be capable of developing new devices with multiple properties involving the change in the nature of chemical bonding in low-dimensional structures.

Site specific seismic hazard analysis of monumental site Dharahara, Kathmandu, Nepal

This study was carried out to estimate the seismic requirement for analyzing and designing the monumental structure, Dharahara, in Kathmandu, Nepal. A probabilistic seismic hazard analysis of the study region was performed to develop the elastic response spectrum for the bedrock site. The obtained spectrum was compared with the existing seismic codes, NBC 105:2020 and IS 1893:2016, to estimate the target response spectrum. One-dimensional equivalent linear (EQL) and non-linear (NL) ground response analyses were performed using DEEPSOIL v7, incorporating a suite of ground motions. The three borehole logs exhibited very soft soil in the region. Due to the presence of soft soil strata in the region under study, strength-corrected modulus reduction and damping curves were adopted in the current study to overcome the effect of larger shear strain. The average response spectra from EQL analyses predicted higher values than NL analyses. Finally, a comparison of the proposed design response spectrum with the code spectra was performed. Comparisons revealed that the mean EQL and NL outputs fall in between the design spectra of similar soil classes in NBC 105:2020 and IS 1893:2016 seismic codes.

FUNCTIONALLY GRADED POROUS MATERIAL FOR PLATES WITH COMPLEX CUTOUTS AND FINITE ELEMENT MODELING FOR FREE VIBRATION BEHAVIOR

The free vibration behaviors of functionally graded porous plates with complex cutouts are investigated according to a novel C0 type high order shear deformation theory. Both the effect of normal and shear strains are included in this theory as well as shear correction factor is not needed in it. Numerical results have been presented and compared with those available in the literatures. The influences of some parameters like porosity factor and the exponent graded are also studied in this paper. Some new results are finally presented as benchmark for further validation in the future.

Three-dimensional, rotational flamelet closure model with two-way coupling

A new flamelet model is developed to be used for subgrid modelling and coupled with the resolved flow description for turbulent combustion. The model differs from current models in several critical ways. (i) Non-premixed flames, premixed flames or multi-branched flame structures are determined rather than prescribed. (ii) The effects of shear strain and vorticity on the flames are determined. (iii) The strain rates and vorticity applied at the subgrid level are directly determined from the resolved-scale strain rates and vorticity without the use of a contrived progress variable. (iv) The flamelet model is three-dimensional without need for assuming axisymmetry or planar geometry. (v) The effect of variable density is addressed in the flamelet model. Solutions to the Navier–Stokes equations and the associated scalar equations governing the flamelet model are obtained without the boundary-layer approximation. By appropriate coordinate transformation, a similar solution is found for the rotational flamelet model, reducing it to a system of ordinary differential equations. Vorticity is shown to create a centrifugal force on the subgrid counterflow that modifies the molecular transport rates and burning rate. Sample computations of the rotational flamelet model without coupling to the resolved flow are presented first to demonstrate the importance of the new features of the model. Scaling laws are presented for relating strain rates and vorticity at the subgrid level to those quantities at the resolved-flow level for coupling with large-eddy simulations or the time-averaged mean-flow level for Reynolds-averaged flows. The time-averaged behaviour of a simple turbulent flow is resolved with coupling to the rotational flamelet model. Specifically, a two-dimensional, multicomponent, time-averaged planar shear layer with variable density and energy release is employed using a mixing-length description for the eddy viscosity. Needs for future study are identified.

A general higher-order shear deformation theory for buckling and free vibration analysis of laminated thin-walled composite I-beams

A general higher-order shear deformation theory for buckling and free vibration analysis of laminated thin-walled composite I-beams is proposed in this paper. It is based on a unified nonlinear variation of shear strains in the wall thickness and then theoretical formulation is derived in the general form which can recover the previous conventional theories such as classical and first-order thin-walled beam theory. Series-type solutions with hybrid shape functions are developed for different boundary conditions. Numerical examples are performed on laminated thin-walled composite I-beams with arbitrary lay-ups. Effects of transverse shear strains, fiber angles and slenderness ratio on the critical buckling loads and natural frequencies of the beams are reported.

Decoupling of strain and temperature effects on microstructural evolution during high shear strain deformation

The interplay between defect generation by shear strain and defect annihilation by local heating is difficult to predict in shear-assisted processing techniques. Here, we decoupled the effects of high shear strain and external heating in an immiscible Cu-Nb alloy using a pin-on-disk tribometer to mimic the microstructural evolution of material during solid-phase processing. The change in sub-surface deformation, strain distribution, and redistribution of the second phase as a function of temperature were examined using transmission electron microscopy and atom probe tomography. Zener-Hollomon parameter is used to semi-quantify the deformation of Cu-Nb alloys as a function of strain and temperature.

Higher-order model for the thermal analysis of laminated composite, sandwich, and functionally graded curved beams

In this paper, a polynomial type fifth-order curved beam theory is developed and applied to investigate the bending response of laminated composite, sandwich, and functionally graded beams curved in elevation under the temperature load changing linearly through the thickness. The theory developed herein considered the effects of both transverse shear strain () and transverse normal strain () along with the curvature effects (1+z/R). Governing equations and boundary conditions of the curved beams are derived with the help of the principle of virtual work. Navier’s method is used to get the analytical solutions of simply supported curved beams under the action of thermal load. The numerical results are obtained for various (h/L) and (R/L) ratios along with the different values of the power-law exponent in the case of functionally graded beams. The numerical results obtained using the present theory for laminated composite, sandwich, and functionally graded straight beams are compared with previously published results and then the formulation and computer codes are extended to derive the numerical results corresponding to curved beams. The authors have presented many useful results in the present paper on curved beams which can be serving as a benchmark for further studies.

Lateral hysteretic behavior of a novel metal rubber bridge bearing

In this paper, a novel metal rubber bearing is proposed as an alternative to the conventional rubber bearings for small- and medium-span highway bridges to solve the aging-related issues of conventional rubber bearings such as chemical degradation and erosion. The bearing is made of porous metal wire by coiling, weaving and cold-pressing to specific shapes. A shear test program is then described on two metal rubber bearings of stainless steel wire with different densities in order to identify the characteristics of hysteretic curves. The effects of shear strain, compressive stress, loading frequency and repeated loading cycles on the hysteretic behavior were investigated. It was found that the lateral hysteretic curves are approximately in bilinear shape, which consists of an initial elastic stage and a post-yield stage. The equivalent damping ratio of the tested bearings was around 20% at 25% shear strain levels and meanwhile increased with the strain levels, indicating an appreciable energy dissipation capacity. In addition, stiffness degradation was observed for the hysteretic curves beyond a certain deformation limit due to the plastic deformation caused by wire delamination and bearing bulging. However, beyond this limit, the bearing could still work as a unit with stable hysteretic behavior. These characteristics make the metal rubber bearing a great candidate for the conventional rubber bearings. It was also found that the hysteretic behavior is related with a variety of parameters such as density, loading frequency and compressive stress. Finally, it was found that the Bouc-Wen model with appropriate input parameters representing the mechanical properties can accurately simulate the hysteretic curves of the proposed bearings.

Influences of elastic foundations on the nonlinear free vibration of composite shells containing carbon nanotubes within shear deformation theory

In this work, the solution of nonlinear free vibration problem of composite shells structures containing carbon nanotubes (CNTs) resting on elastic soils within shear deformation theory (ST) is presented. After modeling the mechanical properties of nanocomposite shell structures containing CNTs and elastic soils, the basic relations, and governing equations of double curved shell structures within the ST are established considering the geometric nonlinearity. The frequencies of nonlinear and linear free vibrations and their ratios for inhomogeneous nanocomposite structures on the soils within the ST are obtained using perturbation method for the first time. After checking the methodology of the research, the effects of soils, nonlinearity, shear strains and patterns of CNT on the frequency-amplitude dependence of nanocomposite shell structures for various geometric parameters are carried out.

Thermoelastic bending analysis of laminated composite shells using a trigonometric shear and normal deformation theory

In the present study, a trigonometric shear and normal deformation theory using trigonometric functions in the displacement field is developed and employed for the static analysis of laminated composite spherical shells subjected to sinusoidal mechanical/thermal loads with simply supported boundary conditions. In the present theory, the effect of both transverse shear and normal strain is considered. The present theory satisfies the zero transverse shear stress conditions at the top and the bottom surfaces of the shell. By using the principle of virtual work, the governing equations and boundary conditions are derived. Navier’s solution procedure is employed to solve the governing differential equations and satisfying the boundary conditions. For validation of the present theory, obtained results are compared with higher-order theories and 3D elasticity solutions wherever possible. Thermal stresses in laminated plates are deduced from the present shell theory and compared with the exact thermoelastic solutions. Thermal stresses presented for the laminated composite spherical shells can serve as a benchmark for future work.

Intrinsic dependence of welding quality and recrystallization on the surface-contacted micro-asperity scale during ultrasonic welding of Cu–Cu joints

Substantial shear deformation induced by high-frequency friction at the interface is inseparable from recrystallization and welding quality during ultrasonic welding. In this study, we prepared welding surfaces with various micro-asperity scales to analyze the comprehensive effects of deformation heat, shear strain and strain rate on the recrystallization and welding quality. Smaller surface-contacted micro-asperities with a size of 16.03 nm led to a surge in the low angle grain boundaries and recrystallization grains before the formation of a complete weld, which drastically increased the load carry capacity by 139% for joints welded at 1500 J comparing with larger micro-asperities. Molecular dynamics simulation indicated that weld formation involved a dynamic process, including micro-connection, tear, fracture, flattening and weld spread, and the reduction in the micro-asperity scale accelerated the flattening process and aggravated shear deformation at the intimate contact positions. According to the calculation model of recrystallization induced by the shear deformation, smaller micro-asperities promoted the coupling between high shear strain and low strain rate, and maximum shear strain of 1.57 and minimum average strain rate of 346/s were obtained simultaneously, which decreased critical recrystallization strain and enlarged the dynamic recrystallization regions during ultrasonic welding.

A new higher order shear and normal deformation theory for the free vibration analysis of sandwich curved beams

The free vibration analysis of functionally graded sandwich beams curved in elevation is presented in this paper using a fifth-order curved beam theory accounting for the effects of transverse shear and normal strains i.e. thickness stretching effects. The theory assumes higher-order variations of axial (tangential) as well as transverse (radial) displacements. Equations of motion are derived from the dynamic version of the principle of virtual work and solved analytically by using Navier’s technique. The present theory is applied for the free vibration analysis of sandwich curved beams with functionally graded face sheets and the homogenous core. The material properties of face sheets are graded in the thickness direction according to the power law. The non-dimensional fundamental frequencies are obtained for different parameters such as radius of curvature, the power-law index, and lamination scheme and compared with previously published results wherever possible and found in good agreement with those. It is observed that as the radius of curvature is decreased keeping length and thickness constant the value of non-dimensional fundamental frequency increases. It is also observed that as the power-law index increased the non-dimensional frequency decreases for all length to thickness ratios.

On the deformation of laminated composite and sandwich curved beams

Abstract Plenty of research articles are available on the static deformation analysis of laminated straight beams using refined shear deformation theories. However, research on the deformation of laminated curved beams with simply supported boundary conditions is limited and needs more attention nowadays. With this objective, the present study deals with the static analysis of laminated composite and sandwich beams curved in elevation using a new quasi-3D polynomial type beam theory. The theory considers the effects of both transverse shear and normal strains, i.e. thickness stretching effects. In the present theory, axial displacement has expanded up to the fifth-order polynomial in terms of thickness coordinates to effectively account for the effects of curvature and deformations. The present theory satisfies the zero traction boundary condition on the top and bottom surfaces of the beam. Governing differential equations and associated boundary conditions are established by using the Principal of virtual work. Navier’s solution technique is used to obtain displacements and stresses for simply supported beams curved in elevation and subjected to uniformly distributed load. The present results can be benefited to the upcoming researchers.

Effects of a stainless steel interlayer on the interfacial microstructure and bonding strength of Cu/Al clad sheets prepared via the powder-in-tube method

Cu/Al clad sheets with a 304 stainless steel foil (SUS304) interlayer are successfully fabricated by the powder-in-tube method. The influence of SUS304 thickness on the interfacial structure, elemental diffusion, and peeling strength of the clad sheets is studied. Experimental results indicate that the initial Cu/Al interface is partially transformed into a Cu/SUS304/Al interface after introducing the SUS304 interlayer. The proportion of SUS304 fragments at the bonding interface is shown to increase with thickness of the SUS304 interlayer. Differences in deformability between SUS304 interlayer and Cu/Al matrix promote the occurrence of shear deformation at the bonding interface via the cladding process, enhancing atomic diffusion at the Cu/SUS304/Al interface. Peeling tests reveal that interfacial cracks in clad sheets with an SUS304 interlayer propagate along the Cu/SUS304 and Cu/Al interfaces. Under combined effects of interfacial transfer and large shear strain, the interfacial strength of clad sheets is apparently improved. Clad sheets with the thickest SUS304 interlayer (30 μm) exhibit highest peeling strength (30.9 N/mm), demonstrating 73.6% improvement over clad sheets without an interlayer. These findings provide novel insights into the innovative design of clad sheets possessing extraordinary interfacial strength.

Nonlinear vibration of multilayer shell-type structural elements with double curvature consisting of CNT patterned layers within different theories

In this article, the nonlinear vibration of moderately thick multilayer shell-type structural elements with double curvature consisting of carbon nanotube (CNT) patterned layers is investigated within different shell theories. The first order shear deformation theory has been generalized on the motion for moderately thick multilayer shell-type structural elements with double curvature consisting of CNT patterned layers for the first time. Then, by applying Galerkin and semi-inverse perturbation methods to motion equations, and the frequency-amplitude relationship is obtained. From these formulas, the expressions for nonlinear frequencies of multilayer spherical and hyperbolic-paraboloid shells, rectangular plate and cylindrical panels patterned by CNTs within shear deformation and classical shell theories are obtained in special cases. The reliability of obtained results is verified by comparison with other results reported in the literature. The effects of transverse shear strains, volume fraction, sequence and number of nanocomposite layers on nonlinear frequency are discussed in detail.

The effect of shear strains on grain size in the Ni3Al intermetallic compound synthesized under pressure

Using a numerical simulation we investigated the distribution of the shear strains appeared in the Ni3Al intermetallic compound billet during its crystallization under high temperature synthesis from a powder mixture under uniaxial compression. The pressure varied from 326 to 434 MPa. The grain size distribution in the produced billet was measured experimentally. It was found that both maximal values of the shear strains and minimum grain size occur at the edges of the billet. The agreement between the distributions of the simulated shear strains and experimentally obtained grain size suggests correctness of the model used.

AN IMPROVED METHOD OF CALCULATING BEAM DEFORMATION CONSIDERING TRANSVERSE SHEAR STRAIN

In 1921, Timoshenko improved upon the Euler‒Bernoulli beam theory by adding the effect of transverse shear strains. In the Euler–Bernoulli beam theory, transverse shear strains are neglected, and cross- sections remain plane and perpendicular to the neutral axis. In the Timoshenko beam theory, cross-sections still remain plane but are no longer perpendicular to the neutral axis. Although the transverse shear strain approaches zero, the Timoshenko beam theory does not converge on the Euler‒Bernoulli beam theory due to the shear locking. Many authors have attempted to overcome this problem and although they have brought acceptable results, these still have theoretical limitations. Therefore, in this paper, the author presents an improved method of calculating the beam considering transverse shear strain to overcome the theoretical limitations of previous authors. The problem is addressed by the use of numerical methods which achieve convergence and avoid the issue of shear locking.

Magnetic field dependent viscoelasticity of a highly stable magnetorheological fluid under oscillatory shear

In our previous works, a new kind of magnetorheological fluid (MRF) consisting of high viscosity linear polysiloxane (HVLP) as carrier and carbonyl iron particles (CIPs) as magnetoactive dispersions, i.e., HVLP MRF, was proposed. HVLP MRF is a promising candidate in the field of heavy equipment for its long-term suspension stability. In this study, we further investigate the viscoelastic properties of HVLP MRF under oscillatory shear in order to evaluate its work performance. HVLP MRFs with different CIP concentrations (0, 20, 40, 60, and 70 wt. %) were synthesized. SEM microstructure, visible MR effect, and magnetic properties were performed. The effects of magnetic flux density, CIP concentration, shear strain, and shear angular frequency on the viscoelastic moduli were examined by using a Physica MCR-301 rheometer. The results show that the viscoelastic moduli are magnetic field dependent. The storage modulus increases with increasing the magnetic flux density, while the loss modulus presents a tendency of rising up at the beginning and declining in late. A critical particle concentration threshold (∼70 wt. %) was found to maximize the magneto-storage modulus increment. Both the upper limit of linear viscoelastic region and the flow point increase as the magnetic flux density increases. It reveals that the field dependent viscoelasticity of HVLP MRF is the result of competition between the structure-enhancement of magneto-induced particle chains and structural deformation under oscillatory shear. Additionally, in the linear viscoelastic region, HVLP MRF shows little dependence on shear angular frequency, implying an excellent working stability in a complex environment.