Influence Of Shear Strain Research Articles

Microstructure Evolution and Mechanical Properties of AlCoCrFeNi2.1 Eutectic High-Entropy Alloys Processed by High-Pressure Torsion.

High-entropy alloys (HEAs) have garnered significant attention for their exceptional properties, with eutectic high-entropy alloys (EHEAs) emerging as particularly notable due to their incorporation of eutectic structures comprising soft and hard phases. This study investigated the influence of shear strain on the microstructural refinement and mechanical properties of AlCoCrFeNi2.1 EHEAs, which were subjected to high-pressure torsion (HPT) at room temperature under a pressure of 6 GPa across 0.5 to 3 turns, compared to the initial material. After HPT treatment, significant grain refinement occurred due to strong shear strain, evidenced by the absence of B2 phase peaks in X-ray diffraction (XRD) analysis. Microhardness increased substantially post-HPT, reaching a saturation point at approximately 575 HV after three turns, significantly higher than that of the original sample. Moreover, the ultimate tensile strength of HPT-treated specimens reached around 1900 MPa after three revolutions, compared to approximately 1100 MPa for the as-cast alloy, with a mixed fracture mode maintained. This investigation underscores the efficacy of HPT in enhancing the mechanical properties of AlCoCrFeNi2.1 EHEAs through microstructural refinement induced by shear deformation, offering insights into the design and optimization of advanced HEAs for various engineering applications.

Influence of Shear Strain on the Deflection of Girders

Numerical calculations are a standard part of modern structural design. Engineers remain particularly interested in real problems where analytical and numerical solutions can be compared with experimental results. Such cases are typical examples of benchmarks because they are used to verify the assumptions introduced. This study shows in detail how shear stresses affect the deflection of a relatively short and high cantilever when the span-to-height ratio of the cross-section is less than five. Such models are frequently used in the design of cantilevers that support heavily loaded beams, for example in the cement industry (e.g., often as structural elements for a heat exchanger system) or for the assessment of short cantilever limit states that appear during excavation in rock sediments. The models are also suitable for designing the various details and joints in the industry of prefabricated elements. This work analyzes in depth the analytical solutions for the displacement field of the linear elastic plane stress theory with two displacement boundary conditions. Also, the solutions were compared with the beam, two-, and three-dimensional numerical models using SAP2000. The results highlight the fundamental principles and solutions behind plane stress and beam theories, with an insight into the advantages and limitations of such models. Doi: 10.28991/CEJ-2024-010-05-04 Full Text: PDF

Exploring electronic features in monolayer and bilayer MX2 (M = Hf, Zr; X = S, Se) structures under shear strain

This study employed first-principles calculations to investigate the dynamic stability of monolayer, bilayer, and heterostructure systems of four MX2 (M = Hf, Zr and X = S, Se) TMDCs, as well as the influence of shear strain on their electronic properties. The computed binding energies and phonon dispersions demonstrate the excellent dynamic stability of bilayer systems, while the small effective masses of electrons and holes in monolayer systems suggest high carrier mobility. Under shear strain, the bandgap size and type of monolayer MX2 system and their vdW heterostructures are effectively modulated, transitioning to metallic behavior under certain strain conditions. Both types of heterostructures exhibit type-II band alignment, serving as direct bandgap semiconductors, facilitating effective electron-hole separation between different layers and thereby reducing recombination. This study elucidates the tunability of the electronic properties of monolayers, bilayers, and heterostructures of MX2 systems under shear strain, which is important for expanding material functionalities and optimizing device performance.

Influence of shear strain on the electronic properties of monolayers MoS2, WS2, and MoS2/WS2 vdW heterostructure.

This study investigates the dynamic stability of monolayers MoS2, WS2, and MoS2/WS2 van der Waals heterostructures (vdWHs) and the influence of shear strain on their electronic properties. The computational results of the binding energy and phonon dispersion demonstrate the excellent dynamic stability of MoS2/WS2 vdWHs. The MoS2/WS2 vdWH, with a type-II band alignment and an indirect bandgap, reduces electron-hole recombination, enhancing the efficiency and performance of optoelectronic devices. Under shear strain, the bandgap size and type of monolayers MoS2, WS2, and MoS2/WS2 vdWHs were effectively modulated, along with the interlayer charge redistribution in the MoS2/WS2 vdWHs. This work reveals the tunability of the electronic properties of monolayers MoS2, WS2, and MoS2/WS2 vdWHs under shear strain, offering new possibilities and solutions for developing optoelectronic devices, sensors, and related fields. This work employed the CASTEP module within the Materials Studio software package for first-principles calculations. Ultrasoft pseudopotentials were employed during geometry optimizations to account for ion-electron interactions using the GGA-PBE functional for exchange-correlation potentials. The electronic configurations of the S, Mo, and W atoms were chosen as their typical arrangements: (3s2p4), (4s2p6d55s1), and (5s2p6d46s2), respectively. A vacuum layer of 20Å was added to avoid interactions between the atomic layers. A cutoff energy of 500eV was set for structural optimization and self-consistent calculations, with k-point grids of 6 × 6 × 1 and 9 × 9 × 1. During the structural optimization process, the energy convergence criterion was set to 1 × 10-5eV, and the thresholds for interatomic forces and stresses were set to 0.01eV/Å and 0.01 GPa, respectively. Grimmer's DFT-D2 correction accounted for the interlayer vdW interactions in the MoS2/WS2 vdWH, while the phonon dispersion was calculated using the linear response method.

Effects of shear deformation and rotary inertia on elastically constrained beam resting on pasternak foundation

This study investigates the free vibrations of elastically constrained shear and Rayleigh beams placed on the Pasternak foundation. Of particular interest, it is aimed to analyze the influence of shear strain, rotational inertia, elastic stiffness, and shear layer on the natural frequencies and eigenmodes of beam vibrations. For this purpose, the eigenfrequencies and eigenmodes are determined using analytical and numerical techniques. A finite element scheme is developed employing quadratic and cubic polynomials for slope and transverse displacement, respectively. The efficiency and accuracy of the finite element method are illustrated by comparing it with the analytical results for generalized and special cases. The underlying model analysis justifies that the natural frequencies of the beam vibration depend only on the geometry of the Rayleigh beam, while these frequencies depend on the physical and geometric properties of the shear beam. However, the natural frequencies of the Euler-Bernoulli depend solely on the geometric conditions of the beam.

High pressure torsion, a large‐scale manufacturing tool for high ZT skutterudite thermoelectrics

AbstractFor mass production of thermoelectric generators, a cheap/sustainable method is required to fabricate leg material with a high figure of merit, ZT. Severe plastic deformation, SPD, increases the defect density, and in parallel decreases the grains to nano‐size. SPD via high‐pressure torsion, HPT, was used to process hot pressed discs, whereby the Seebeck coefficient remained unchanged and the enhanced electrical resistivity was overcompensated by a low thermal conductivity, resulting in a raise of ZT. Secondly, cold pressed commercial p‐ and n‐type skutterudite‐powder was deformed via HPT, exhibiting higher ZT values than the hot‐pressed reference samples. This method was upscaled to samples of 30 mm diameter (heights: 1 mm, 8 mm). These large samples, enabled to study the influence of shear strain with all its impact on micro‐structural, physical and mechanical properties, revealing for the thin samples record high ZTs. Both thick samples showed homogeneous properties and ZTs∼1.3.

Properties of HPT-Processed Large Bulks of p-Type Skutterudite DD0.7Fe3CoSb12 with ZT > 1.3

The influence of shear strain on the microstructural, physical, and mechanical properties was studied on large bulk samples (diameter: 30 mm, thickness: 1 or 8 mm), which were consolidated by high-pressure torsion (HPT) from a commercial powder DD0.7Fe3CoSb12. Particularly, the thick sample (mass �53 g) allowed measuring the thermoelectric (TE) properties with respect to various orientations of the specimen in the sample. All data were compared with those of a hot-pressed (HP) reference sample, prepared with the same powder. Transmission electron microscopy, as well as X-ray powder diffraction profile analyses, Hall measurements, and positron annihilation spectroscopy, supported these investigations. Furthermore, synchrotron data for the temperature range from 300 to 825 K were used to evaluate the changes in the grain size and dislocation density as well as the thermal expansion coefficient via the change in the lattice parameter during heating. In addition, hardness and direct thermal expansion measurements of the HPT samples were performed and compared with the HP reference sample's values. With the increase of the shear strain from the center to the rim of the sample, the electrical resistivity becomes higher, whereas the thermal conductivity becomes lower, but the Seebeck coefficient remained almost unchanged. For the thin as well as thick samples, the enhanced electrical resistivity was balanced out by a decreased thermal conductivity such that the maximum ZT values (ZT = 1.3-1.35 at 856 K) do not vary much as a function of the shear strain throughout the sample, however, all ZTs are higher than that of the HP sample. The thermal-electric conversion efficiencies are in the range of 14-15 (for 423-823 K). With similar high ZT values for the n-type skutterudites, fabricated in the same fast and sustainable way, these p- and n-type skutterudites may serve as legs for TE generators, directly cut from the big HPT bulks. ©

Dynamic Analysis of Functionally Graded Porous Beams Using Complementary Functions Method in the Laplace Domain

In this study, an efficient numerical procedure is introduced to the solution of the dynamic response of functionally graded porous (FGP) beams. The elastic modulus and mass density of the porous materials are considered to have non-uniform distributions along the thickness direction. The typical open-cell metal foam is assumed to govern the material constitutive law. Within the framework of the first-order shear deformation theory (FSDT) the influence of shear strain is included in the formulations. The impact of damping is also considered. By using the canonically conjugate momentums and their derivatives, the governing canonical equations of motion of FGP beams are derived for the first time. These equations are then transformed into the Laplace space and solved numerically with the aid of the Complementary Functions Method (CFM). Obtained results are retransformed to the time domain by using an efficient inverse transform method. The dynamic response of FGP beams is studied for several boundary and loading conditions. The suggested procedure is verified with the available published literature and the finite element method. Detailed parametric studies are conducted to show the influence of porosity constants, symmetric and asymmetric porosity distributions and damping ratios on the dynamic response of FG porous beams.

Influence of shear strain on HPT-processed n-type skutterudites yielding ZT=2.1

After our successful new and energy-saving production route to prepare bulk skutterudites with high ZTs from commercial powders via cold pressing (CP) and high-pressure torsion (HPT), we present in this paper a detailed study of the influence of shear strain and the preparation parameters, especially the temperature, on the micro-structural, thermoelectric and mechanical properties by analyzing specimens cut from various positions of the HPT disks of (Sm,Mm)0.15Co4Sb12. Across these large discs (30 mm in diameter and about 1 mm thickness) the shear strain γ rises linearly from the center of the sample to the rim reaching γ ∼ 450 (for 5 revolutions), a value first time realized for skutterudites. HPT-straining is essential for the introduction of high densities of crystal lattice defects, particularly dislocations, which result in a significant refining of the grains. Whereas the processing temperature mainly influences the density of the HPT consolidated samples and as a consequence, physical and mechanical properties, the applied shear strain rules the thermoelectric parameters. As an important feature, the Seebeck coefficient remained roughly unchanged under strain. Although the increasing shear strain caused the thermal conductivity to significantly decrease, this beneficial effect is accompanied by a concomitant significant increase of the electrical resistivity. Consequently, the interplay of the two controversial influences results in a maximum and record high thermoelectric figure of merit ZT ∼2.1.

HPT production of large bulk skutterudites

This paper documents that consolidation and subsequent severe plastic deformation of commercial skutterudite powders via high pressure torsion (HPT) serves for an easy, fast, cheap and sustainable production method for excellent n-type skutterudite bulks, (Sm,Mm)0.15Co4Sb12, with high ZT values. Large cylindrical samples with 30 mm in diameter and 8 mm thickness (∼55 g) were successfully prepared in one step. These large samples enabled for the first time to (i) study the influence of shear strain on the micro-structural, thermoelectric and mechanical properties by analysing specimens cut from various positions of the HPT disks and (ii) to evaluate these properties orientation sensitive. These investigations were supported by electron probe microanalyses, transmission electron microscopy as well as XPD full profile analyses, XPS, Raman and Hall measurements. Whilst the orientation dependence on the electrical and thermal conductivity is found to be rather weak, the applied shear strain has a pronounced influence, as with increasing strains the thermal conductivity was reduced to the targeted levels. This beneficial effect, however, is accompanied by a massive increase of the electrical resistivity. ZT values turned out to be rather homogeneous over the entire sample with ZT∼1.3 at 850 K.

The Influence of Shear Strain on the Torsion Capacity of Hybrid Beams

This research discusses experimentally the shear strain of the reinforcement concrete hybrid beams composed of reactive powder concrete (RPC) at the peripheral and conventional concrete (CC) at the core beams under torsional strength tests. Shear strain is usually represented by (), which is explained as the tangent of the angle and is be like the length of deformation at its maximum divided by the length of perpendicular in the plane of the force application. Twelve reinforced concrete beams are tested having the following dimensions: 100, 200 and 1500mm as width, height and length respectively with thickness of the RPC concrete were 40 and 20mm. The beams were cast and tested to failure in torsion by using two opposite cantilevers steel arms that contribute to transferring the torque to the centre of the beams. Two control (CC and RPC) beams were poured, and the ten other beams were all poured as hybrid ones. Experimental data of the three strain gauges locations in the middle of the beams in one of the side surface face, to calculate shear strain (). The percentage of shear strain at ultimate torsion capacity was reduced by about 76% for RPC (RP) to CC (NC) beams and 63% for hybrid beam (H1) to CC (NC) beam.

Multiaxial fatigue experiments and life prediction for silicone sealant bonding butt-joints

Uniaxial and multiaxial fatigue experiments were conducted on the adhesively bonded hollow cylindrical butt-joint specimen under load-controlled mode, and several prediction criteria were used for multiaxial fatigue life prediction. The experimental results showed that the fatigue life of uniaxial tensile cycle was shorter than that of uniaxial torsional cycle, and the fatigue life of the non-proportional circular loading path was shorter than that of the proportional loading path. In addition, the multiaxial fatigue life prediction results showed that Smith-Watson-Topper criterion based on the maximum principal strain as the critical plane had a conservative life prediction for the non-proportional circular loading path. Fatemi-Socie criterion mainly considered the influence of shear strain which yielded the non-conservative prediction for some data points of proportional loading path. Chen-Xu-Huang criterion combined energy density and critical plane achieved better fatigue life predictions than those from the previous two criteria. Furthermore, considering general failure modes of the adhesively bonded butt-joints, the modified Chen-Xu-Huang model was proposed, and the predicted results are good agreement with the experiments.

Reciprocal space mapping study of CdTe epilayer grown by molecular beam epitaxy on (2 1 1)B GaAs substrate

We examine high quality, single crystal CdTe epilayer grown by molecular beam epitaxy (MBE) on ()B GaAs substrate using both positions and full width at half maximums (FWHMs) of reciprocal lattice points (RLPs). Our results demonstrate that reciprocal space mapping (RSM) is an effective way to study the structural characteristics of the high-index oriented epitaxial thin films having a large lattice mismatch with the substrate. The measurement method is defined first, and then the influence of shear strain () on the position of the () node of epilayer is clarified. It is concluded that the lattice tilting is likely to be related with the lattice mismatch. Nondestructive measurement of the dislocation density is achieved by applying the mosaic crystal model. The screw dislocation density, estimated to be cm−2, was calculated utilizing the broadened peakwidths of the asymmetric RLP of the epilayer lattice.

Thermal conductivity of graphene nanoribbons under shear deformation: A molecular dynamics simulation

Tensile strain and compress strain can greatly affect the thermal conductivity of graphene nanoribbons (GNRs). However, the effect of GNRs under shear strain, which is also one of the main strain effect, has not been studied systematically yet. In this work, we employ reverse nonequilibrium molecular dynamics (RNEMD) to the systematical study of the thermal conductivity of GNRs (with model size of 4 nm × 15 nm) under the shear strain. Our studies show that the thermal conductivity of GNRs is not sensitive to the shear strain, and the thermal conductivity decreases only 12–16% before the pristine structure is broken. Furthermore, the phonon frequency and the change of the micro-structure of GNRs, such as band angel and bond length, are analyzed to explore the tendency of thermal conductivity. The results show that the main influence of shear strain is on the in-plane phonon density of states (PDOS), whose G band (higher frequency peaks) moved to the low frequency, thus the thermal conductivity is decreased. The unique thermal properties of GNRs under shear strains suggest their great potentials for graphene nanodevices and great potentials in the thermal managements and thermoelectric applications.

Development of Sliding Connections for Structural Analysis by a Total Lagrangian FEM Formulation

In this study a total lagrangian 2D finite element formulation is used to model plane frames developing large displacements and rotations considering sliding connections. This kind of connections is usually called prismatic and cylindrical joints. In order to be self-containing, the steps of the development of a frame finite element of any approximation order that considers the influence of shear strain by means of a generalized Reissner kinematics is presented. The adopted degrees of freedom are positions and rotations. Using positions as degrees of freedom simplifies the total lagrangian description and enables a comprehensive presentation of the proposed connections. Revolute connections are considered by direct degrees of freedom matching. Prismatic connections are modelled by the Lagrange multiplier technique that constrains positions and rotation of a sliding node to the varying position and rotation of a path element. Cylindrical joints are introduced in similar way by Lagrange multipliers releasing the sliding node rotation. The principle of stationary potential energy is used to write the non-linear equilibrium equation including the Lagrange multiplier influence. To solve the non-linear equation a Taylor expansion is carried out and the Newton-Raphson procedure is employed. The frame element is considered elastic, following the Saint-Venant-Kirchhoff constitutive model. Selected examples are used to validate the formulation and to show its possibilities of application.

Influence of Shear Strain on the Poisson’s Ratio of Clean Sands

In the present study, a series of resonant column tests was performed to determine the influence of confining pressure, shear strain and relative density on the dynamic properties and Poisson's ratio of poorly graded clean sand. The tests were performed on the sand specimens of size 50 × 100 mm compacted at relative densities 30, 50 and 75 %. To achieve the corresponding relative density, sand was compacted in 5 equal layers with a specific number of blows. A fixed-free type resonant column apparatus was used to determine the dynamic soil properties at various confining pressures. It has been inferred from the data that the shear modulus ( $$G$$ ) increases with an increase in confining pressure and relative density; and decreases with an increase in shear strain. In addition, damping ratio ( $$D$$ ) decreases with an increase in confining pressure and relative density; and increases with an increase in shear strain. In addition, Poisson’s ratio ( $$\nu$$ ) decreases with an increase in confining pressure and relative density and increases with an increase in the shear strain. The variation of shear modulus with Poisson’s ratio is also discussed. It has been found that there has been a decrease in shear modulus with an increase in Poisson’s ratio of the soil. It is noticed that the small strain shear modulus determined from the present study closely matches with the value determined using the correlations from the literature.

The influence of shear strain on critical load bearing capacity. Determination of instability factor $$ \varvec{k}_{\varvec{c}}^{\varvec{G}} $$ k c G

The paper is concerned with timber constructions. The paper presents a solution of a rod deflection differential equation. The rod deflection equation describes a compressed rod to which a transverse force is applied. The equation accounts for the influence of shearing forces on the magnitude of displacement. Based on the equation, the critical force and the rod deflection function at the rod’s initial curvature defined by a sinusoid were determined. Having found the rod deflection function and the critical force, a formula for the instability factor $$ k_{c}^{G} $$ was derived to account for the influence of shear strain. The paper demonstrates in which particular cases it is necessary to take into account the influence of deflection caused by shearing on the critical load bearing.

Spin Lifetime Enhancement by Shear Strain in Thin Silicon-On-Insulator Films

Spintronics attracts at present much interest because of the potential to build novel spin-based devices which are superior to nowadays charge-based microelectronic elements. Utilizing spin properties of electrons opens great opportunities to reduce device power consumption in future electronic circuits. Silicon, the main element of microelectronics, is promising for spin-driven applications. Understanding the details of the spin propagation in silicon structures is a key for building novel spin-based nanoelectronic devices. We investigate the influence of shear strain on surface roughness induced spin relaxation in a thin silicon-on-insulator-based transistor. Shear strain dramatically influences the spin, which opens a new opportunity to boost spin lifetime in a silicon spin field-effect transistor.

Change in morphology of fuel cell membranes under shearing

The effect of shearing on Nafion/water systems was investigated using Dissipative Particle Dynamics (DPD). This simulation approach has been shown to accurately reveal the morphology of such systems in the steady state. We first confirmed that the length of the Nafion chain, 5 and 20 DPD units, has no influence on the overall morphology for four different concentrations, 10, 20, 30, and 40%, of water. Shearing effects with 0.05 and 0.2 rates were then studied according to the Nafion chain length, 5 and 20 DPD units, and water content, 10 and 30%. It was shown that low water contents and long chain length lead to the formation of water-rich tubes, aligned with the shear direction. The formation of such channels can ultimately lead to an increase in the proton conductivity at low humidity. The size of these water tubes thus results from a combined influence of shear strain, chain relaxation time, interfacial tension and water content.

Analytical Modeling to Predict Adiabatic Shear Critical Condition for Orthogonal Cutting

As the deformation of chip increases with cutting speed, the morphology of chip changes from continuous to serrated type. It is supposed that serrated chips generate due to adiabatic shear instability in the primary deformation zone. A new analytical model for predicting adiabatic shear critical condition in orthogonal cutting is proposed by considering cutting conditions and properties of workpiece material. It is found that the influence of shear strain on the onset of adiabatic shear could be neglected. The shear strain rate and temperature, however, play a leading role on the onset of adiabatic shear. At lower cutting speed the shear strain rate plays a dominant role while at higher cutting speed the situation is just the reverse. With the increase of cutting speed, the yield stress, material characteristic constant and uncut chip thickness will facilitate adiabatic shear instability, while the coefficient of strain rate hardening, coefficient of strain hardening, coefficient of thermal softening, thermal diffusivity and tool rake angle have negative effect on adiabatic shear instability.