Search

Enhanced sampling algorithms are indispensable when working with highly disconnected multimodal distributions. An important application of these is the conformational exploration of particular internal degrees of freedom of molecular systems. However, despite the existence of many commonly used enhanced sampling algorithms to explore these internal motions, they often rely on system-dependent parameters, which negatively impact efficiency and reproducibility. Here, we present fully adaptive simulated tempering (FAST), a variation of the irreversible simulated tempering algorithm, which continuously optimizes the number, parameters, and weights of intermediate distributions to achieve maximally fast traversal over a space defined by the change in a predefined thermodynamic control variable such as temperature or an alchemical smoothing parameter. This work builds on a number of previously published methods, such as sequential Monte Carlo, and introduces a novel parameter optimization procedure that can, in principle, be used in any expanded ensemble algorithms. This method is validated by being applied on a number of different molecular systems with high torsional kinetic barriers. We also consider two different soft-core potentials during the interpolation procedure and compare their performance. We conclude that FAST is a highly efficient algorithm, which improves simulation reproducibility and can be successfully used in a variety of settings with the same initial hyperparameters. [ABSTRACT FROM AUTHOR]

Mesogens, which are typically stiff rodlike or disklike molecules, are able to self-organize into liquid crystal (LC) phases in a certain temperature range. Such mesogens, or LC groups, can be attached to polymer chains in various configurations including within the backbone (main-chain LC polymers) or at the ends of side-chains attached to the backbone in an end-on or side-on configuration (side-chain LC polymers or SCLCPs), which can display synergistic properties arising from both their LC and polymeric character. At lower temperatures, chain conformations may be significantly altered due to the mesoscale LC ordering; thus, when heated from the LC ordered state through the LC to isotropic phase transition, the chains return from a more stretched to a more random coil conformation. This can cause macroscopic shape changes, which depend significantly on the type of LC attachment and other architectural properties of the polymer. Here, to study the structure–property relationships for SCLCPs with a range of different architectures, we develop a coarse-grained model that includes torsional potentials along with LC interactions of a Gay–Berne form. We create systems of different side-chain lengths, chain stiffnesses, and LC attachment types and track their structural properties as a function of temperature. Our modeled systems indeed form a variety of well-organized mesophase structures at low temperatures, and we predict higher LC-to-isotropic transition temperatures for the end-on side-chain systems than for analogous side-on side-chain systems. Understanding these phase transitions and their dependence on polymer architecture can be useful in designing materials with reversible and controllable deformations. [ABSTRACT FROM AUTHOR]

The piezoelectric properties of carbon nanotubes (CNTs) doped with boron (B) and nitrogen (N) were studied using the classical molecular dynamics (MD) simulation software package large scale atomic/molecular massively parallel simulator. The interactions among the nanotube atoms C, N, and B were calculated using the Tersoff potential. MD simulations were performed to observe the changes in the piezoelectric coefficient of the doped CNTs under loading conditions like tension, torsion, and a combination of both. We considered a wide range of chirality to determine the influence of structural variation on the piezoelectric effect. The study revealed that B-CNTs exhibit superior piezoelectric coefficients compared to N-CNTs, indicating the significant role of dopant type. Moreover, under tensile loading, zigzag-oriented B-CNTs showed higher piezoelectric coefficients with a maximum e 33 = 0.2441 C m−2, whereas under torsional loading, armchair-oriented B-CNTs showed enhanced response with a maximum e 36 = 0.0564 C m−2. A notable observation was that under combined loading conditions (tensile and torsional), the piezoelectric behavior of the B-CNTs was dependent on the nanotube's chirality and did not yield a linear additive response. The polarization induced under combined loading in most of the doped CNTs is significantly higher than the sum of polarization generated under tensile and torsional loading conditions. This behavior suggests that the overall piezoelectric effect under combined loading can be enhanced, which emphasizes the need for an approach to optimize the mechanical loading condition. The results showcase the potential of B-/N-CNTs to be engineered for efficient performance by demonstrating that tailored mechanical loading can enhance the piezoelectric responses in doped CNTs, opening a pathway for highly functional and efficient nanoscale piezoelectric devices. [ABSTRACT FROM AUTHOR]

In the present research, torsional buckling response of thick truncated conical shell panels supporting on Winkler-type elastic medium has been surveyed. The shell is constructed from a porous metal material reinforced by graphene platelets (GPLs) in which the porosity and volume weight fraction of nanofillers are graded along the thickness of shell. Three functions for porosity distribution and five patterns of GPLs are examined. To estimate the Young modulus of the shell, Tsai-Halpin micromechanical model, and for its mass density, extended rule of mixture is employed. Linear theory of 3D elasticity in conjunction with the virtual work principle and numerical graded finite element method (FEM) are applied to derive the state of equilibrium in pre-buckling mode. Torsional buckling forces are derived by applying nonlinear Green strains and by deriving geometric stiffness matrix of the system. The effect of various parameters such as coefficient of porosity, various distributions of porosity and different nanofiller patterns, weight fraction of graphene nanofillers, semi vertex angle of cone, span angle, stiffness of elastic medium and various boundary conditions on torsional buckling loads of functionally graded (FG) porous truncated conical panel reinforced by GPLs have been presented. The main purpose of this research is obtaining the best distribution of porosity and GPLs pattern and investigating the influence of adding nano particles on the torsional buckling forces of the shell. Results denote that employing GPL-X pattern in conjunction with porosity distribution 1 provides the maximum value of buckling loads. Besides by adding the nano particles, the amount of buckling loads will increase 100%. [ABSTRACT FROM AUTHOR]

In the current research work, the shear capacity of the cold-formed steel (CFS) three-bolted clip angle (CA) beam-to-column moment connection (3BM) is investigated with 45 laboratory test results. The 3BM connection comprises a three-bolted CA connector that connects the web portions and a bolted flange cleat (FC) that connects the flange portions of the beam and column; in comparison, the three-bolted shear connection (3BS) connects only the web portions of the beam and column. The presence of the FC improved the shear strength of the 3BM connection over the 3BS connection and it is quantified using a coefficient called the "rigidity factor (β)." A shift in the failure mode of CAs from shear local buckling in a 3BS connection to tearing failure in a 3BM connection was observed as the FC resists beam torsional deformation and delays the early local buckling of the CA. The existing design shear equation of the 3BS connection is improved by expressing it as a function of CA failure modes. Following the same trend, the existing design shear method for the CFS moment connection is improved by incorporating the failure modes of the CA boundary conditions along with the geometric and material properties of both the CA and FC for the present 3BM connection. In addition, an empirical shear design equation is suggested for the 3BM connection. The design factors of the proposed 3BM shear equations for load and resistance factor design, limit state design, and allowable strength design methods were evaluated from the reliability study. [ABSTRACT FROM AUTHOR]

The electronic and optical properties of hydrogenated silicene at different torsion angles are investigated using the density functional theory (DFT). It was found that when silicene was hydrogenated, the Si atoms were pulled out of plane due to covalent interactions between the Si and H atoms, increasing their flexural height to 0.731 Å. Torsional deformation decreases the structural stability of hydrogenated silicene and its adsorption energy decreases with increasing twist angle. Under the effect of torsion deformation, the bandgap of hydrogenated silicene increases and then decreases. The bandgap is 2.168 eV at a torsion angle of 0∘, indicating a wide bandgap semiconductor. Mulliken's charge population analysis shows that charge transfer occurs between Si–H atoms, with Si atoms losing electrons and becoming positively charged and H atoms gaining electrons and becoming negatively charged. From the analysis of optical properties, the torsional deformation induced the maximum absorption and reflection peaks of all the hydrogenated silicene systems to appear in the ultraviolet region. Compared with the system without torsional deformation, these peaks exhibit varying degrees of red and blue shifts. The above findings provide guidance for the application of silicene in nanooptoelectronic devices. [ABSTRACT FROM AUTHOR]

The monopile-friction wheel hybrid foundation withstands various loads in the marine environment, such as the vertical load (V) transmitted from the superstructure, horizontal loads (H) caused by wind or wave, torsional loads (T) caused by rotating structures. In this article, 1 g model tests are used to investigate the behavior of the monopile-friction wheel hybrid foundation under independent horizontal load (H) or torsional load (T), and combined loads (H-T) in sand soil, respectively. The failure envelopes of H-T loading plane are obtained from the measured load-displacement data with the simplified calculation equations presented as well. Finally, we also discuss quantitatively the influences of the pre-vertical loads, foundation geometry and loading eccentricity on the bearing capacity of the hybrid foundation via the three-dimensional finite element method. The results indicate that the displacement response of the hybrid foundation under independent loading is significantly different from that subjected to combined loads (H-T). The torsional bearing capacity of the hybrid foundation can be significantly improved by 6.6-33.34% under pre-horizontal load. The horizontal bearing capacity of the hybrid foundation decreases sharply after the pre-torsional load reaches a certain value, which decreases by about 20%. The presence of a friction wheel improves the torsional/bending moment distribution of pile shaft. [ABSTRACT FROM AUTHOR]

The mechanical properties of porcupine quills have attracted the interest of researchers due to their unique structure and composition. However, there is still a knowledge gap in understanding how these properties can be utilized to design biomimetic structures with enhanced performance. This study delves into the nanomechanical and macro-mechanical properties of porcupine quills, unveiling varied elastic moduli across different regions and cross sections. The results indicated that the elastic moduli of the upper and lower epidermis were higher at 8.13 ± 0.05 GPa and 7.71 ± 0.14 GPa, respectively, compared to other regions. In contrast, the elastic modulus of the mid-dermis of the quill mid-section was measured to be 7.16 ± 0.10 GPa. Based on the micro- and macro-structural analysis of porcupine quills, which revealed distinct variations in elastic moduli across different regions and cross sections, various biomimetic porous structures (BPSs) were designed. These BPSs were inspired by the unique properties of the quills and aimed to replicate and enhance their mechanical characteristics in engineering applications. Compression, torsion, and impact tests illustrated the efficacy of structures with filled hexagons and circles in improving performance. This study showed enhancements in maximum torsional load and crashworthiness with an increase in filled structures. Particularly noteworthy was the biomimetic porous circular structure 3 (BPCS_3), which displayed exceptional achievements in average energy absorption (28.37 J) and specific energy absorption (919.82 J/kg). Finally, a response surface-based optimization method is proposed to enhance the design of the structure under combined compression-torsion loads, with the goal of reducing mass and deformation. This research contributes to the field of biomimetics by exploring the potential applications of porcupine quill-inspired structures in fields such as robotics, drive shafts, and aerospace engineering. [ABSTRACT FROM AUTHOR]

Elastic beam structures connected by hinges are a common basic component of many mechanical systems. In this study, the nonlinear transverse vibration of a beam with one end free and the other end simply supported with a torsion spring is investigated. A torsional quasi-zero-stiffness vibration isolator is employed at the fixed end of the beam for isolating the vibration excitation from the base. Using Hamilton's principle, the differential equation of motion for the transverse vibration of the beam is obtained, and the natural characteristics of the beam are determined. The dynamic equation of the system is derived by using Galerkin truncation method and the harmonic balance method is adopted to obtain the nonlinear vibration response. Compared with the vibration transmissibility of the beam supported by the equivalent linear torsion spring, the quasi-zero-stiffness vibration isolation system shows superior vibration isolation performance. It is found that the beam fixed with a torsional quasi-zero-stiffness isolator can reduce the first resonant frequency and provide a wide effective isolation range at low frequency, which is rarely affected by the strong nonlinearity. The results would provide an innovative method of introducing the torsional quasi-zero-stiffness isolator into the passive vibration control of continuum system. [ABSTRACT FROM AUTHOR]

In this study, Eringen's nonlocal elasticity theory that applies the small size effects in functionally graded porous nanotubes embedded in an elastic matrix is discussed. The material properties of functionally graded porous nanotubes are taken into account to vary over the radius direction with a rule of mixture. The free torsional vibration relation according to nonlocal elasticity theory, via Hamilton's principle, is obtained and an eigenvalue solution is constructed for the free torsional vibration response of the presented work. The presented analytical model is validated by comparing the calculated mathematical results for homogeneous nanotubes with rigid and non-rigid boundary conditions. Special attention is given to deformable boundary conditions, porosity coefficient, material grading coefficient and also to the influence of elastic medium on the free torsional vibration frequencies. In this paper, it has been proven that the influence of length, elastic medium, elastic torsional spring rigidities, material grading and porosity coefficients on the vary in the torsional vibration frequency of the functionally graded nanotube is not small. [ABSTRACT FROM AUTHOR]

This paper reports numerical investigations on the bearing performance of a novel finned suction caisson foundation under combined vertical, horizontal, moment, and torsional loading in clay. From comprehensive comparison analyses between finned and nonfinned suction foundations, improvements in uniaxial and combined loading capacities due to the assembled fins are examined and interpreted by insights into the failure mechanisms. Effects of non-coplanar torsional loading on the combined loading capacity surfaces are investigated and evaluated with the aid of the failure envelope method. A set of closed-form expressions accommodated to three different loading scenarios (zero-, low- and high-torsion conditions) are proposed based on a detailed design chart to estimate the bearing performance under combined vertical (V), horizontal (H), moment (M), and torsional (T) loading (denoted as VHMT loading) in clay. The critical considerations in design including effects of loading direction and foundation–soil interface are also discussed. [ABSTRACT FROM AUTHOR]

This study introduces an innovative approach for the reconstruction of wind turbine tower states using a tangential recursion algorithm. The primary objective is to enable real-time monitoring of the operational condition of wind turbine towers. The proposed method is rooted in strain–load theory, which enables the accurate identification of tower load states. The tangential recursion algorithm is utilized to translate the strain data acquired from strategically placed sensors into reconstructed point positions. The subsequent refinement of these positions incorporates considerations of torsional loads and geometric deformations, culminating in the comprehensive and precise reconstruction of the tower's deformation behavior. Through the use of the OpenFAST V8 simulation software, a thorough analysis is conducted to investigate the load and deformation characteristics of the NREL 5 MW wind turbine tower across diverse operational scenarios. Furthermore, the load conditions corresponding to rated operating circumstances are applied to a finite element model constructed with the lumped mass method. The identification of tower load states and the comprehensive reconstruction of deformation patterns are realized through the extraction of strain data from critical points in the finite element model. The credibility and accuracy of the proposed method are rigorously evaluated by juxtaposing the identification and reconstruction outcomes with the results derived from the OpenFAST simulations and finite element analyses. Notably, the proposed method circumvents the requirement for external auxiliary calibration equipment for the tower, rendering it adaptable to a broader spectrum of operational contexts and making it consistent with unfolding trajectories in wind power advancement. [ABSTRACT FROM AUTHOR]

Prestressed concrete (PC) box girder is an innovative structure that is widely used in large-span bridges. Under eccentric loads such as vehicles, PC girders are inevitably under combined bending and torsion. To study its bending-torsional behavior, a refined full-range analysis model based on the combined action softening truss model (CA-STM) was proposed, where a simple and effective solution procedure and failure criteria were provided. The equilibrium equation, initial estimation equation for torque, and material constitutive model were modified by considering the prestressing effect to improve the CA-STM. An optimized algorithm was also employed to simplify the solution procedure instead of the traditional trial-and-error method, thus increasing the solution rate and stability. The theoretical curves predicted from the improved CA-STM exhibited great agreement with the available experimental results, and the predicted cracking and ultimate loads were also close to the experimental values. Hence, the improved CA-STM can reasonably predict the full-range mechanical response and failure modes of PC box girders subjected to combined bending and torsion, which provides great support to the design evaluation of such bridges. [ABSTRACT FROM AUTHOR]

The electronic structure of carbon nanotube bundles (CNTBs) can be a tough task for the routine first-principle calculation. The difficulty comes from several issues including the atomic structure, the boundary condition, and above all the very large number of atoms that makes the calculation quite cumbersome. In this work, we estimated the band gap of the CNTBs based on the results from single-walled carbon nanotubes (SWCNTs) under different deformations. The effects of squeezing, stretching, and torsion on the bands of SWCNTs were investigated through first-principle calculations, from which the band gaps of bundles were analyzed because the effects of these deformations were qualitatively independent when the distortions were small. Specifically, the gaps of (4,4) and (8,0) CNTBs under a reasonable torsional strength were predicted, wherein we were able to see metal–semiconductor and semiconductor–metal transitions, respectively. Such reversible mechanical modification of the conductivity may be helpful to the future band-gap engineering in nanoscale circuits. [ABSTRACT FROM AUTHOR]

Under the current scouring, submarine cables are prone to be exposed, suspended, and even vortex‐induced vibration (VIV), threatening their mechanical and electrical properties. In this contribution, a finite element simulation model of 110‐kV single‐core optical fibre composite submarine cable is established. The natural frequency and resonant frequency of the model are obtained through wet mode analysis and harmonic response analysis. Then the VIV is simulated by the fluid–structure coupling method. Moreover, the stress extraction method of the torsional optical fibre position under the VIV is proposed. The results show that when the reduced speed is 2.57, the submarine cable appears beating vibration, which is composed of two vibrations with similar frequencies. When the reduced speed is 7.08, the vibration frequency is about 7.813 Hz, causing a rapid increase in vibration amplitude. The stress distribution of the torsional optical fibre presents a mirror image relationship at two moments separated by half a vibration cycle. Also, the frequency of stress change is the same as the frequency of VIV, which can judge whether the VIV occurs. The VIV range and position can be determined by the location where the stress changes the most. [ABSTRACT FROM AUTHOR]

Dual plating of comminuted distal femoral fractures allows for early patient mobilization. An additional helically shaped medial plate avoids the medial vital structures of the thigh. The aim of this study is to investigate the biomechanical competence of an augmented lateral locking compression plate distal femur (LCP‐DF) using an additional straight versus a helically shaped medial LCP of the same length. Ten pairs of human cadaveric femora were instrumented with a lateral anatomical 15‐hole LCP‐DF. Following, they were pairwise instrumented with either an additional medial straight 14‐hole LCP (group 1) or a 90°‐helical shape LCP (group 2). All specimens were biomechanically tested under quasi‐static and progressively increasing combined cyclic axial and torsional loading until failure. Initial interfragmentary axial displacement and flexion under static compression were significantly smaller in group 1 (0.11 ± 0.12 mm and 0.21 ± 0.10°) versus group 2 (0.31 ± 0.14 mm and 0.68 ± 0.16°), p ≤ 0.007. Initial varus deformation under static compression remained not significantly different between group 1 (0.57 ± 0.23°) and group 2 (0.75 ± 0.34°), p = 0.085. Flexion movements during dynamic loading were significantly bigger in group 2 (2.51 ± 0.54°) versus group 1 (1.63 ± 1.28°), p = 0.015; however, no significant differences were observed in terms of varus, internal rotation, and axial and shear displacements between the groups, p ≥ 0.204. Cycles to failure and load at failure were higher in group 2 (25,172 ± 6376 and 3017 ± 638 N) compared to group 1 (22,277 ± 4576 and 2728 ± 458 N) with no significant differences between them, p = 0.195. From a biomechanical perspective, helical double plating may be considered a useful alternative to straight double plating, demonstrating ameliorated damping capacities during flexion deformation and safer application as the medial neurovascular structures of the thigh are avoided. [ABSTRACT FROM AUTHOR]

This study explores the effect of adding 3 wt.% Y to pure magnesium (Mg) on its mechanical behavior under cyclic torsional loadings at room temperature. The research examines deformation and cracking modes in both pure Mg and Mg‐3Y samples. Deformation modes are monitored using quasi‐in‐situ EBSD observations coupled with slip trace analysis. The findings reveal that basal slip dominates the cyclic deformation throughout the fatigue life of the pure Mg sample, while both basal and pyramidal slip dominate the cyclic deformation in the Mg‐3Y sample. Intergranular cracking is the primary cracking mode for both samples under cyclic torsional loadings. Basal and pyramidal slip persistent slip band (PSB) cracking serves as a primary transgranular cracking mode in the pure Mg and Mg‐3Y samples, respectively. The study also investigates the underlying mechanism governing the activity of various deformation modes, cracking modes, and mechanical behavior. Highlights: Under cyclic torsional loadings, the Mg‐3Y sample exhibited enhanced activity of nonbasal slip.Intergranular cracking was a dominant cracking mode for the pure Mg and Mg‐3Y samples under cyclic torsional loadings.Basal slip and pyramidal slip PSB cracking was a primary transgranular cracking mode in the pure Mg sample and Mg‐3Y sample, respectively.The increased activity of nonbasal slip in the Mg‐3Y sample is possibly responsible for its longer fatigue life. [ABSTRACT FROM AUTHOR]

This article aims to analyze the nonlinear instability of toroidal shell segment (TSS) made of functionally graded porous material (FGPM), exposed to elevated temperature and subjected to uniform torsion. The volume fraction of two material constituents is varied through the shell thickness according to a power-law function, while porous distribution into FGPM is modeled in forms of cosine functions. Governing equations in terms of deflection and stress function are established within the framework of classical shell theory incorporating geometrical nonlinearity. Two edges of the TSS are assumed to be simply supported and elastically restrained. Multi-term analytical solutions are assumed to satisfy boundary conditions and Galerkin method is applied to derive closed-form expressions of nonlinear load–deflection relations and buckling loads. Parametric studies are carried out to analyze the separate and combined influences of material and geometry properties, porous coefficient and distributions, degree of edge constraint and elevated temperature on the buckling resistance and postbuckling strength of torsionally loaded FGPM TSSs. [ABSTRACT FROM AUTHOR]

A comprehensive test program was performed to experimentally investigate the effect of CFRP strengthening on the axial strength and stability of CFS plain angle short columns subjected to monotonic axial compression. A total of 28 specimens were tested by varying the CFRP strengthening configurations for different column heights. Both uni-directional (CF_UD) and bi-directional (CF_BD) CFRP were considered. The influence of various parameters such as the type of CFRP, fiber orientation, and number of CFRP layers was investigated and discussed in detail. For single layer (ply) of CFRP, CF_UD-0° strengthening configuration resulted in maximum increase of axial capacity by 58.33% and 45.72% (in comparison to bare steel specimens), corresponding to 0.5 m and 1.0 m column lengths respectively. All the bare steel and skin-strengthened specimens failed predominantly due to torsional–flexural buckling mode. Additional layer of CFRP wrapping was found to enhance the axial capacity further and CF_UD-0°/BD was found to possess greater capacity in the case of double layer of CFRP. Adopting cardboard in-fill in addition to CF_UD-0° wrap has prevented the torsional mode of buckling and resulted in a peak increase of axial capacity by 192.55% and 240.61% corresponding to 500 mm and 100 mm long specimens, respectively. [ABSTRACT FROM AUTHOR]

In this paper, based on the non-linear mechanics theory of the drill pipe, a mechanical model of stick-slip vibration of the drill pipe has been established by considering the torsional properties of the drill pipe, kinetic energy and the motion law of the bit. The example calculations and sensitivity analysis of the parameters are carried out. The results show that increasing the rotational speed, viscous damping, length of the drill collar and de-creasing the weight of bit have the effect of suppressing the stick-slip vibration. [ABSTRACT FROM AUTHOR]

Context: The effects of selected substituent groups (-CH3, -Br, -CO2CH3, -COOH, and -NH2) and their relative positions on the electronic and structural properties of mono-substituted naphthalenes were investigated theoretically. In order to elucidate the suitability of the studied substituents in different fields including chemistry, spectroscopy, and materials sciences, accurate DFT calculations were performed at the dispersion-corrected B3LYP level of theory (B3LYP-D3/6–311 + + G(d,p)), and the obtained results were then validated by extensive comparisons with available experimental data. Among the studied substituents, the -NH2 group causes the maximum reduction of the HOMO–LUMO energy gap. This result revealed clearly the suitability of the -NH2 group, compared to other studied substituents, in the chemical synthesis of future organic-semiconductors having small energy gaps. In addition, the level of theory adopted in this study allowed the fine discrimination between the chemical reactivity parameters of the studied congeners, which is very difficult to perform experimentally. On the other hand, the rotational barriers of the studied non-halogen substituent groups were predicted. The greater sensitivity of the rotational barrier heights to the local environments, arising from intra-molecular interactions, was attributed to the -CH3 group. The torsional frequencies, calculated within the harmonic approximation, were also employed to relatively explore the differences between the environments of the same substituent at two different positions. The usefulness of these results can be manifested in the vibrational spectroscopy field, especially, for the IR/ Raman spectral analysis of polycyclic-aromatic congeners. Method: All calculations were conducted within the Density functional theory (DFT) using the so-called dispersion-corrected B3LYP functional (B3LYP-D3) with the carefully selected 6–311 + + G(d,p) basis set. The B3LYP-D3/6–311 + + G(d,p) calculations were performed using the Gaussian 09 program, and the obtained results were visualized by employing the GaussView 6.0.16 program. [ABSTRACT FROM AUTHOR]

Like metallic materials, fiber metal laminate (FML) lets the material has a simple metal structure behavior but with such advantages as specialized strength properties, impact, fire resistance, weight savings, corrosion resistance, and metal fatigue. The main focus of this article is to indicate the dynamic response of circular size-dependent circular plates made of FML material via 3D-elasticity theories. The size-dependent structure is simulated by coupling the modified nonlocal couple stress and 3D-elasticity theories (MNCS-3DET). For accurate modeling of the elastic substrate, torsional and linear spring and Pasternak foundation are modeled using the equations of horizontal friction force and torsional interaction. Harmonic differential quadrature method and Chebyshev–Gauss–Lobatto grid distribution points are coupled for solving the partial differential equations of the current micro/nano-structure. Novelties of this work consider the effects of MCS-3DET, torsional interaction, horizontal friction force, and FML material in the construction of the circular micro/nanoplate. In the results section, the outputs are verified with other published articles, and the outcomes show that the MCS-3DET parameter, elastic foundation coefficient, horizontal friction force coefficient, and geometry have an essential role in the dynamic stability of the FML micro/nano-structure. [ABSTRACT FROM AUTHOR]

This paper researches the free vibrations and corresponding material parameters of a functional gradient graphene platelets-reinforced composite (FG-GPLRC) cantilever torsional plates with both pore and graphene variations in the transverse direction. Utilizing the feature of closed-cell cellular solids, the mixture rule, and the modified Halpin–Tsai model, the material parameters of the composite are determined for different volume fractions of component materials. Then, using the classical plate theory (CLPT), the Rayleigh–Ritz technique and polynomials, the dynamic equation that can be used to obtain the free vibration mode shapes and frequencies of the rotating cantilever torsional plate is given. Comparison studies with the previous calculation results from available literature and the finite element (FE) models of cantilever plates are conducted, and the correctness of the present theoretical formulation and numerical calculation is verified. Finally, the effects of graphene platelet (GPL) distribution, porosity distribution (PD), GPL content, rotational speed, and average geometric size of GPL on free vibrations of the system are studied in depth. [ABSTRACT FROM AUTHOR]

Advanced 3D woven composites have become an enabling technology in many industrial applications due to their proven benefits, particularly the improvement of the out-of-plane mechanical behavior with respect to other reinforcement schemes. The latter property has been shown to be strongly affected by the effects of compaction during manufacturing. The present study proposes an automated framework, based on heuristic procedures, for the generation of representative volume elements (RVEs) of 3D woven composites, allowing to include global and local geometrical features induced by transverse compaction, such as overall thickness reduction, changes in yarn cross-sections and consistent global/local fiber fractions. The methodology is illustrated for three types of reinforcement, namely a plain weave, an angular through-thickness interlock and a 3D orthogonal RVE. The resulting geometries generated by the proposed method compare favourably with typical observations from the literature in a quantitative manner. Finally, the proposed framework is integrated with a previously developed meshing strategy to allow damage studies for a selected architecture (plain weave) under torsional loading, presenting a complete computational chain by building cohesive zone finite element models from compacted RVEs. The torque-angle response curves obtained after the damage simulations show a decrease in stiffness and an increase of damage levels with compaction, which is in line with the expectations. [ABSTRACT FROM AUTHOR]

This study aims to characterize the twisting behavior of bi-directional functionally graded (FG) micro-tubes under torsional loads within the modified couple stress theory framework. The two material properties involved in the torsional static model of FG small-scale tubes, i.e., shear modulus and material length scale parameter, are assumed to possess smooth spatial variations in both radial and axial directions. Through the utilization of Hamilton's principle, the governing equations and boundary conditions are derived, and then, the system of partial differential equations is numerically solved by using the differential quadrature method. A verification study is conducted by comparing limiting cases with the analytical results available in the literature to check the validity of the developed procedures. A detailed study is carried out on the influences of the phase distribution profile and geometric parameters upon twist angles and shear stresses developed in FG micro-tubes undergoing external distributed torques. [ABSTRACT FROM AUTHOR]

Antimicrobial and antituberculosis activities of transition metal complex Cu(I) and Cu(II) from salicylhydrazone of anthranihydrazide (HL1) have been theoretically investigated using DFT methods at ωB97XD, PBEPBE, MPW1PW91, HSEH1PBE, CAM-B3LYP/6-311++G(d,p) level of theory. Owing to the fact that microbial and tuberculosis attacked still prevail despite studies reported in the literatures. This study utilized a higher theoretical model to unravel necessary information about the possible application of the HL1 and its complexes as a potential drug candidate. The results obtained reveal that the ligand (HL1) had the higher energy gap for the HES and MPW whereas, it Cu(II) complex had the least energy gap making it more reactive in the biological environment compared to its counterpart. The Natural Bond orbital (NBO) analysis reveals molecular interactions are of four kinds; LP→BD*, LP→LP*, LP*→BD*, BD*→BD*, and BD*→LP* where the higher perturbation energy was observed from BD*(C2-C3) → BD*(C4- 5) with the energy of 231.74 kcal/mol. The vibration analysis shows that the studied complexes have 32 atoms and 90 normal modes, with 20 symmetric, 7 asymmetric, 31 bending, and 32 ring torsional distribution. And their theoretical wavelength of absorption was observed to be in good agreement with experimental reported values. Cu(II) was observed with the highest dipole moment and first-order hyperpolarizability (βtotal) with corresponding values of 9.30D and 19.268 which shows its can be good for medicinal application. Molecular docking screening showed that the ligand and its complexes have better antimicrobial activities compared to antituberculosis. [ABSTRACT FROM AUTHOR]

The shear modulus and damping ratio are arguably the two most crucial soil parameters to be used in seismic site-response analyses and a wide variety of other geotechnical engineering applications involving soil materials subjected to dynamic loading. The dependency of these parameters on the level of load-induced shear strains in the field has been investigated rather extensively for different types of soils. Most experimental studies, however, have relied on a limited set of controlled environmental factors and stress variables, mainly soil moisture and confinement. The present work is an attempt to gain further insights into the possible impact of an additional critical factor: soil temperature. A resonant column apparatus was upgraded to assess the dynamic response of three types of cohesive–frictional soils as they transitioned from linear to nonlinear behavior under thermo-controlled cyclic torsional loading. Emphasis was placed on shear modulus degradation, and hence variation in damping ratio, with increasing shear strain amplitude (cyclic torque magnitude). Results showed a mostly detrimental effect of increasing soil temperature on the normalized shear modulus, damping ratio, and threshold shear strain of clayey, silty, and sandy soils when subject to small to medium shear strain levels. [ABSTRACT FROM AUTHOR]

This work develops the optimization of torsional, wear, and fatigue life behaviors based on the hybrid emperor penguin social ski-driver for reinforced steel wire. Using granite and rutile particles reinforcement, steel wires are strengthened. Normal steel wire rope and reinforced wire rope are prepared with 7 strands and 15 wires. Using hybrid emperor penguin optimization-based social ski driver Optimization (Hybrid EPSSD), the failure tests such as wear analysis, fatigue life, and torsional behavior are optimized. Besides, the performances of the experimented wire rope are predicted by using hybrid Elman recurrent Neural Network-based EPO (Hybrid ERNN-EPO). Using the Matlab 2018a platform, the optimization and prediction processes are performed. In this, reinforced wire ropes deliver enhanced performances for both experimented and optimization behaviors. From the results, the reinforced wire rope has the best performance which possesses less wear rate, more fatigue life, and torsion behavior are obtained. The experimental outcome of wear depth for reinforced wire rope is 0.18 mm and the optimized wear depth outcome from the Hybrid EPSSD approach is 0.16 mm. For reinforced wire rope, the optimized fatigue life is 4.50 × 104 times at 500 KN and the maximum fatigue life experimentally is 4.20 × 104 times. At a particular hoisting time, the optimization value for the location of maximum torsion angle is 243 to 18 mm is obtained and the experimental values are 240 to 15 m. The reinforced wire rope has a better performance compared to the steel wire rope. [ABSTRACT FROM AUTHOR]

• Nonlinear torsional buckling of toroidal shell segments is presented using the Ritz energy method. • The corrugated core sandwich toroidal shell segments with FG-GRC coatings are considered. • The thermal forces are added to improve the homogeneous model for the corrugated core. • Ritz energy method, Donnell shells theory, and Pasternak's foundation model are applied. • Effects of corrugated core, material and geometrical parameters on the buckling behavior of shells are investigated. An investigation on the nonlinear torsional buckling of corrugated core sandwich toroidal shell segments with functionally graded graphene-reinforced composite (FG-GRC) laminated coatings in temperature change is mentioned in this paper using the Ritz energy method. The complex configuration of sandwich toroidal shell segments with double curvatures and the combination of the corrugated core and the FG-GRC coatings create the special behavior of structures. A homogenization model for corrugated structures and the extended Halpin-Tsai model can be applied to estimate the stiffnesses of shells. The effects of uniform temperature change are taken into account by supplementing the thermal forces into the total forces of shells. The Donnell shell theory and Pasternak's foundation model are used to establish the total potential energy of the structures. Ritz energy method is applied, and the closed condition and circumferential stress are taken into account, the postbuckling curve expressions of torsion-deflection and torsion-twist angle are obtained in explicit forms. The numerically obtained examples can show the significantly beneficial effects of FG-GRC laminated coatings and corrugated core on nonlinear buckling responses of structures. [ABSTRACT FROM AUTHOR]

Motivated by observations of loop formation and elimination phenomena in elastic filaments subjected to torsion and axial end displacement, we develop a tension–torsion tester to study the slack–extension responses of filaments with varied initial twists. The experiments are conducted by initially twisting the filament by a specific degree and subsequently adjusting the axial end displacement. By continuously monitoring the correlation between torque and filament configuration, we can accurately determine the critical points associated with buckling, loop formation and loop elimination. The interconversion of link, twist and writhe is also tracked in the experiment. We establish a relation between torque and end displacement of filament that provides an insight into the conditions leading to instabilities. Three buckling criteria are also evaluated in the context of measurement data. Simulations on the slack and extension of the twisted filaments based on the Cosserat rod theory are performed, providing reliable predictions of the configuration evolution. Our results highlight the importance of twist and slack in torsional buckling processes, providing guidance for the control of systems with twisted slender structures. [ABSTRACT FROM AUTHOR]

Pile foundations may be exposed to torsional loads caused by horizontal eccentric loads brought on waves, wind and earthquakes, as well as axial load brought on by supporting superstructures. This paper highlights a recent strategy to modify piles known as the finned pile. A series of experimental tests were conducted to increase the torsional capacity of a single pile with/without fins in sand under the influence of vertical loads (V), torsional loads (T) and combined loads (T → V), these experiments involved altering fins’ length, width, shape, and number and knowing the effect of these variables on the piles’ maximum torsional capacity. The vertical load-displacement response and the torsion-rotation response have been observed. The results showed that fins improve piles’ torsional capacity. It also showed that on piles’ maximum vertical capacity for independent vertical or torsional loads is different from that of piles under combined loading. It was found that fins’ optimum geometry is that their length equal to 0.6 of the embedded pile’s length and their width equal to the pile’s diameter, where piles’ maximum torsional capacity was (4.12 and 7.36) N.m for regular and finned piles, respectively. Fins increased piles’ maximum torsional capacity by about 79%. [ABSTRACT FROM AUTHOR]

In geotechnical engineering, dynamic soil models are used to predict soil behavior under different loading conditions. This is crucial for many dynamic geotechnical problems related to earthquakes, train loading and machine foundation design. Researchers agree that under dry or drained conditions, cohesionless soils increase in stiffness with each loading cycle. Soil models that simulate the dynamic behaviors of soils are often coupled with the Masing criteria. Such models neglect the impact of stiffening during cyclic loading, leading to an underestimation in the shear modulus (G). This study investigates the stiffening behavior by conducting laboratory tests on three types of Danube sands using the Resonant Column-Torsional Simple Shear device (RC-TOSS). The increase in the dynamic shear modulus with an increasing number of cycles is substantial, especially for samples with low density. Sometimes, the dynamic shear modulus doubles when loaded at high stress levels for more than 50 cycles. A new model is introduced to simulate the stiffening behavior of dry sand when subjected to cyclic torsional loading. Modifications are proposed for the Ramberg–Osgood and Hardin–Drnevich models and for the Masing criteria to overcome the limitations that accompany these models due to the influence of stiffening caused by repetitive loading being ignored. This model can be implemented in finite element and finite difference software to solve dynamic geotechnical problems. [ABSTRACT FROM AUTHOR]

The wings of birds exhibit multi-degree-of-freedom motions during flight. Among them, the flapping folding motion and chordwise passive deformation of the wings are prominent features of large birds in flight, contributing to their exceptional flight capabilities. This article presents a method for the fast and accurate calculation of folding passive torsional flapping wings in the early design stage. The method utilizes the unsteady three-dimensional panel method to solve the aerodynamic force and the linear beam element model to analyze the fluid–structure coupling problem. Performance comparisons of folding flapping wings with different kinematics are conducted, and the effects of various kinematic parameters on folding flapping wings are analyzed. The results indicate that kinematic parameters significantly influence the lift coefficient, thrust coefficient, and propulsion efficiency. Selecting the appropriate kinematic and geometric parameters is crucial for enhancing the efficiency of the folding flapping wing. [ABSTRACT FROM AUTHOR]

For polymer chains, the torsional potential is an important intramolecular energy influencing chain flexibility and segmental dynamics. Through molecular dynamics simulations of an atomistic model for melts of cis–trans-1,4-polybutadiene (PBD), we explore the effect of the torsions on conformational properties (bond vector correlations and mean-square internal distances), fundamental thermodynamic quantities (density, compressibility, internal energy, and specific heat), and glass transition temperature Tg. This is achieved by systematically reducing the strength of the torsional potential, starting from the chemically realistic chain (CRC) model with the full potential toward the freely rotating chain (FRC) model without the torsional potential. For the equilibrium liquid, we find that the effect of the torsions on polymer conformations is very weak. Still weaker is the influence on the monomer density ρ and isothermal compressibility κT of the polymer liquid, both of which can be considered as independent of the torsional potential. We show that a van der Waals-like model proposed by Long and Lequeux [Eur. Phys. J. E 4, 371 (2001)] allows us to describe very well the temperature (T) dependence of ρ and κT. We also find that our data obey the linear relation between 1 / k B T ρ κ T and 1/T (with the Boltzmann constant kB) that has recently been predicted and verified on the experiment by Mirigian and Schweizer [J. Chem. Phys. 140, 194507 (2014)]. For the equilibrium liquid, simulations result in a specific heat, at constant pressure and at constant volume, which increases on cooling. This T dependence is opposite to the one found experimentally for many polymer liquids, including PBD. We suggest that this difference between simulation and experiment may be attributed to quantum effects due to hydrogen atoms and backbone vibrations, which, by construction, are not included in the classical united-atom model employed here. Finally, we also determine Tg from the density–temperature curve monitored in a finite-rate cooling process. While the influence of the torsional potential on ρ(T) is vanishingly small in the equilibrium liquid, the effect of the torsions on Tg is large. We find that Tg decreases by about 150 K when going from the CRC to the FRC model. [ABSTRACT FROM AUTHOR]

BACKGROUND: Few studies are comparing the biomechanical characteristics of three internal fixation techniques in the treatment of distal tibial fractures. OBJECTIVE: To compare the biomechanical properties of distal tibial fractures fixed by medial distal tibial plate, anterior-grade expert tibial nail and retrograde tibial nail. METHODS: Based on the CT data of a SAWBONES 4th generation artificial composite tibia model, a simulation model of distal tibia fracture (AO/ASIF 43-A3) was constructed by digital 3D reconstruction technology. On this basis, three internal fixation methods including locking plate of the medial tibia, expert grade intramedullary nail and retrograde tibial nail were simulated. Finite element analysis was carried out for three groups of implanted assembly models under axial compression and axial torsion loading conditions respectively, and the differences in stress distribution, stress peak value and fracture space displacement were compared among the three groups. RESULTS AND CONCLUSION: (1) When the three groups of internal fixators were loaded under two load conditions, the peak stress of the expert tibial nail group was 283.53 MPa at the unlocked main nail hole under the torsion condition. In the medial distal tibial plate group, the stress peak was located on the third screw, which was 913.07 MPa under the torsional condition. In the retrograde tibial nail group, the stress peak was at the second main nail hole under the torsion condition, which was 435.42 MPa. In the retrograde tibial nail group, the stress peak of the cortical bone around the main nail hole at the medial malleolus appeared under high axial compression condition, which was 55.34 MPa. (2) In terms of fracture gap micromovement, the expert tibial nail group had the highest tangential displacement in the four regions under axial compression load. The axial displacement of the four regions in the medial distal tibial plate group was the highest, and the maximum value was in the lateral region. The peak axial displacement of the expert tibial nail group and retrograde tibial nail group was located in the posterior region. (3) When the axial torsional load was loaded, the peak axial displacement of the medial distal tibial plate group and retrograde tibial nail group was in the lateral region, and the tangential displacement of the four regions in the retrograde tibial nail group was smaller than that in the medial distal tibial plate group and expert tibial nail group. (4) It is indicated that retrograde tibial nail has a biomechanical advantage over the medial distal tibial plate and expert tibial nail in distal tibial fractures in terms of fracture end fretting and internal fixation stress. [ABSTRACT FROM AUTHOR]

BACKGROUND: Unilateral biportal endoscopic lumbar interbody fusion as a novel minimally invasive technique has been widely used in the treatment of lumbar degenerative diseases. However, as a postoperative complication, fusion cage subsidence cannot be completely avoided. OBJECTIVE: To analyze the biomechanical characteristics of unilateral biportal endoscopic lumbar interbody fusion technology by establishing a finite element model, as well as the risk of fusion cage subsidence under different heights of the fusion cage and osteoporosis conditions. METHODS: Based on the CT data of healthy adult male volunteers, the finite element models of the L4-L5 vertebral body were constructed. According to the unilateral biportal endoscopic lumbar interbody fusion operation method, the models with different cage heights of 8, 10 and 12 mm were successively constructed (normal bone and osteoporosis). The flexion, extension, right lateral bend, left lateral bend, right axial rotation, and left axial rotation motions were simulated in models with different bone conditions on the upper surface of L4 with 500 N follower-load and 10 Nm torsional torque. The range of motion, pedicle screw-rod system stress and endplate stress of each model under different working conditions were observed and analyzed. RESULTS AND CONCLUSION: Under the same motion state, the range of motion of the six kinds of lumbar fusion models was significantly lower than that of the normal lumbar model. The range of motion of six kinds of interbody fusion models was the largest under flexion and the smallest under extension. With the increase in cage height, the range of motion of the intervertebral fusion model decreased under the same bone and motion conditions. Under the same bone and motion conditions, with the increase in cage height, the stress of the pedicle screw rod system of interbody fusion model decreased. The stress of pedicle screw rod system in six kinds of interbody fusion models was the highest under lateral bending movement and the lowest under flexion and extension. When the height of the fusion cage was the same, the stress of the pedicle screw rod system in the osteoporosis model was greater than that in the normal model. Under the same bone and motion conditions, with the increase of cage height, the maximum stress of the L4 lower endplate (or L5 upper endplate) of the intervertebral fusion model increased. When the height of the fusion cage was the same, the maximum stress of the L4 lower endplate (or L5 upper endplate) in the osteoporosis model was slightly greater than that in the normal model. Under the same motion state, the maximum stress of the L4 lower endplate was greater than that of the L5 upper endplate in six kinds of intervertebral fusion models. The maximum stress of the L4 lower endplate (or L5 upper endplate) under the flexion was the largest and the maximum stress of the L4 lower endplate (or L5 upper endplate) under the extension was the smallest. The results show that the higher the fusion cage is, the better it is, but it needs to be properly stretched to ensure the stability of the segment and avoid the increased risk of fusion cage subsidence caused by too high fusion cage. [ABSTRACT FROM AUTHOR]

Insufficiently studied, the phenomenon of twisted wind is prevalent in mountainous regions. This study focuses on investigating the characteristics and aerodynamics of a single high-rise building subjected to a twisted wind field (TWF). By comparing the 0° conventional wind field (CWF) with two TWFs (TWF15 and TWF 30) with maximum twisted angle of 15° and 30°, both wind tunnel testing and computational fluid dynamics (CFD) are employed. A comprehensive analysis is conducted to examine the differences between TWFs and CWF in terms of wind profiles, turbulence, aerodynamic characteristics of single high-rise buildings, and wake vortex morphology. The results demonstrate notable disparities betweenTWFand CWF. Particularly, the twisted wind induces inflection in the wind profile, leading to significant acceleration or deceleration. Moreover, the twisted effect generates an asymmetric distribution of average building surface pressure, thereby introducing the potential for asymmetric or torsional loading extremes. Phenomenologically, the twisted effect weakens shear layer separation, creates squeezed separation bubbles, and promotes premature reattachment, resulting in distinct flow field morphologies compared to CWF. Furthermore, as the wind twisted angle increases, the energy concentration associated with Bernard-Karman shedding diminishes, thereby significantly altering the wake characteristics. [ABSTRACT FROM AUTHOR]

A combined method for measuring the thrust vector and roll torque of low-power Hall-effect thrusters is proposed, using a conventional torsional thrust pendulum, with a measurement accuracy of a few tens of micro-Newton meters. The 300–500 W class Hall-effect thruster is mounted horizontally on the pendulum, whose motion is determined only by the radial thrust vector and rolling torque of the thrusters. The contribution of the two components of a Hall-effect thruster is analyzed through the method of changing the position of accelerator and external hollow cathode, with the accelerator contributing a significant portion of the radial thrust vector and increasing linearly with thruster anode power. And the external hollow cathode contributing at a magnitude of one hundred micro-Newtons, in the direction opposite to the cathode. The combining method provides a way to measure the deviation angle of the stationary EP thrusters, an analysis of the contribution of the accelerator and the external hollow cathode, and a method for decreasing the deviation angle of a Hall-effect thruster by counteracting the effects of these two components. • Proposed a new direct measurement method of thrust vector and rolling torque for Hall effect thrusters with conventional torsional pendulum. • The first attempt to measure and analyze the thrust vector contribution of the accelerator and the external hollow cathode. • Firstly proposed a method for decreasing the deviation angle of a Hall-effect thruster by counteracting the effects of the accelerator and the cathode. [ABSTRACT FROM AUTHOR]

Torsion deformable spatial beam and Costello theory are used to establish longitudinal-torsional-lateral coupled model of round balance rope. Based on Coulomb's friction law and longitudinal-torsional-lateral coupled model, the nonlinear coupled dynamic model with friction constraint of round balance rope is established. Meanwhile, time-varying multi-segments non–equal-length element transformation method (TMN-ETM) is proposed to save computation time. Then, natural frequencies, lateral responses are calculated when the coupled stiffness coefficient is zero. And the calculations are compared with traditional solution method. The results show that only about few areas in the round balance rope loop have large stress norm value, while the rest parts have small stress values. Besides, dynamic responses of the balance rope with balance rope suspension rotor releasing are conducted. When the static friction is converted to dynamic friction, the friction torque and angle acceleration will be mutated at the switching instants, and slip-stick transition in angle acceleration occurs. [ABSTRACT FROM AUTHOR]

A new model for a one-dimensional (1D) metamaterial model is formulated based on the couple stress theory. Different point groups of crystal will affect the mechanical couplings in the 1D metamaterial model. We find that when the material belongs to D2 point group, an unusual set of equations is decoupled from governing equations: axial force–torsion–warping (FTW) metamaterial model, which describes an unusual mechanical coupling that cannot occur in traditional materials. The deformation behaviors of the current model under a different axial force are analyzed by using the FTW metamaterial model. The numerical results show that the middle part of the current model has maximum torsional deformation when subjected to sine-type axial force. Since the end of the current model is fixed, the current model does not have compressional deformation globally. Moreover, when the current model is subjected to cosine-type axial force, the FTW coupling is successfully achieved. Then, we study a rod-like metamaterial model under an axial end force. The results show that the compressional deformation occurs at the free end, with a counterclockwise torsion. The current work provides guidance for the structural design and theoretical analysis of the rod-like metamaterial when using the couple stress theory. [ABSTRACT FROM AUTHOR]

An advanced theoretical formulation along with a robust numerical evaluation method are employed to study the 3 D wave propagations and equivalent dynamic stiffnesses of a transversely isotropic elastic ground in rocking and torsional interactions with a harmonically loaded rigid foundation. Using appropriate dynamic Green's functions presented in the literature, the rocking and torsional harmonic oscillations of the foundation are formulated analytically in terms of several Fredholm integral equations of the second kind. Then the dynamic stiffnesses and flexibilities are presented analytically for rocking and torsional oscillations. To validate the analytical results, they are reduced to two simpler cases reported in the literature: the static problem and the case of isotropic materials. The semi-infinite integrals appeared in the solutions are evaluated numerically by utilizing the contour integration and residue theorem along with several commands of the Mathematica software. A complete discussion on the elastic wave propagations due to oscillations of the foundation are presented and a detailed comparison is performed between different waves propagate within the half-space and full-space elastic grounds including the P, SV, SH and the Rayleigh waves. Our results showed that due to rocking oscillation of the foundation, the Rayleigh wave does not propagate in the full-space medium but it propagates in the half-space medium. However due to torsional oscillation, the Rayleigh wave does not propagate neither in the full-space nor in the half-space elastic medium. In addition, due to rocking oscillation, the body waves including P, SV and SH propagate within both half-space and full-space elastic mediums; but due to torsional oscillation, only SH-wave propagates within both full-space and half-space elastic mediums. In some tables, numerical values and mathematical formulas for the dimensionless wave numbers and wave velocities are provided for the P, SV, SH and the Rayleigh waves. The Gaussian quadrature method is implemented for definite integrals appeared in the dynamic stiffnesses. Some graphical figures are provided to represent the dimensionless rocking and torsional dynamic stiffnesses and flexibilities versus the dimensionless frequency for different transversely isotropic materials. The effects of anisotropy of materials and the frequency of excitations on the responses are discussed. The results presented in this paper including the dynamic stiffnesses and wave propagations have direct applications in dynamic soil-structure interaction analyses in civil engineering. [ABSTRACT FROM AUTHOR]

This paper aims to analyze the effects of porosities, tangential constraints of boundary edges and elevated temperature on the buckling and postbuckling behaviors of thin functionally graded cylindrical shells subjected to uniform torsion. The porosities are assumed to exist within functionally graded material (FGM) according to even and uneven distributions. The properties of constituents are assumed to be temperature dependent and effective properties of porous FGM are determined using a modified rule of mixture. Mathematical formulations are established within the framework of classical shell theory taking into account von Kármán–Donnell nonlinearity and elasticity of tangential edge constraints. Multi-term analytical solutions are assumed to satisfy simply supported boundary conditions and Galerkin method is used to determine buckling torsional load and load–deflection relation for postbuckling analysis. Numerical results show that porosities have remarkably deteriorative influences on the torsional buckling resistance and postbuckling load capacities of FGM cylindrical shells. This study also reveals that tangential edge constraints have pronouncedly beneficial and detrimental effects on the postbuckling strength of torsion-loaded porous FGM cylindrical shells at room and elevated temperatures, respectively. [ABSTRACT FROM AUTHOR]

• forced torsional responses of elliptical nanorod based on the nonlocal theory are analyzed. • Linear and nonlinear external torques are selected in this paper. • The size effect is taken into account by investigating the nonlocal elasticity theory. • The effects of the horizontal and vertical aspect ratios, nonlocal parameter are discussed. • it is concluded that the aspect ratio and frequency of excitation are inversely related to angular displacement. The torsional vibration analysis of small-scaled rods is studied in the framework of Eringen's nonlocal theory. The equations of motion and related boundary conditions are deduced by employing the Hamilton principle. The nonlocal elasticity theory based on Eringen's model is used to cover the size-dependent behavior of the nanorods. Galerkin's analytical method is used to solve the equation of motion. In the present work, time-dependent torsional vibration in an elliptical nanorod under the linear and harmonic distributed external torques along with determined amplitude is considered with clamped-clamped end supports. When discussing free vibration analysis, the small-scale effect shows the sufficiency of natural frequencies in different modes. These results are best verified by comparison with results available in the literature. The influences of effective parameters such as nonlocal parameters, the value of aspect ratio, and excitation frequency variations in time-dependent angular displacement and non-dimensional angular displacement are discussed in detail. It is found that an increase in the nonlocal parameter leads to a rise in the value of non-dimensional angular displacement. Also, it is concluded that the aspect ratio and frequency of excitation are inversely related to angular displacement. [ABSTRACT FROM AUTHOR]

Present geophysical model analyzes the propagation characteristics of torsional wave in an inhomogeneous viscoelastic fiber‐reinforced layer sandwiched between superior porous layer and transversely isotropic piezoelectric subspace with imperfect interfaces. Porous layer and intermediate reinforced layer are endowed with initial stress and corrugated interfaces, whereas the lower piezoelectric half space possesses rectangular cavity at the welded contact. Earth's adjacent layers near mountainous region often endowed with initial stresses resemble the present geological setup. The material properties of intermediate layer are considered to be varying exponentially. Particular cases have been deduced for electrically open and short condition for validation with the standard Love wave expressions. Effects of the relevant parameters on resultant torsional velocity have been explored through numerical simulation and depicted for electrically short and open conditions. Findings of present model may be utilized in the field of signal testing, sensors design, seismic acoustic wave (SAW) devices, and geophysical application concerned with torsional wave based on non‐destructive evaluation. [ABSTRACT FROM AUTHOR]