Effect Of Torsional Deformation Research Articles

First-principles study on the effect of torsional deformation on WSe2 as an anode material for calcium ion batteries.

In this paper, the effects of torsional deformation on the electronic properties of intrinsic WSe2 system and Ca-adsorbed WSe2 system were systematically studied by first-principles method. The results show that Ca can be stably adsorbed on the vacancy (H site) of WSe2 surface in all deformation systems, and the adsorption energy of the system without deformation is the highest. Intrinsic WSe2 is a semiconductor with a direct band gap of 1.53 eV. The torsional deformation makes WSe2 change from a direct band gap semiconductor to an indirect band gap semiconductor and finally to a metal property. The adsorption of Ca makes the conduction band of WSe2 move down and increases the number of peaks in the conduction band region. The new density of state peaks are mainly derived from the contribution of W-d, Se-p, and d orbitals of adsorbed atoms in each adsorption system. Mulliken charge analysis shows that Ca transfers most of the valence electrons to the substrate, and the torsional deformation changes the amount of transferred charge. The twist deformation reduces the diffusion barrier of Ca on WSe2 surface from 0.20 to 0.14 eV. The above results provide a basis for the improved application of WSe2 in ion batteries. In this study, all the first-principles calculations are based on Materials Studio 8.0 software package. The generalized gradient approximation (GGA) functional Perdew-Burke-Ernzerhof (PBE) is used for the electron exchange correlation interactions in all systems. The optimization algorithm uses Broyden-Fletcher-Goldfarb-Shanno (BFGS) to optimize the model structure and calculate the energy. The measured cutoff energy is optimized to 450 eV, and the radius of the vacuum layer in the Z-axis direction is 20 Å. The K-point of 7 × 7 × 1 is selected by Monkhorst-Pack method. The structural optimization criterion is selected, the convergence radius of the force is 0.01 eV/Å, and the displacement radius between atoms is within 0.001 Å distance. The energy convergence radius of each atom is less than 1.0 × 10-6 eV/atom.

High-fidelity flexible multibody model considering torsional deformation for nonequatorial space elevator

Space elevators are a promising technology for future space transportation. The primary component of a space elevator is a tether deployed from a geostationary orbit towards the Earth and into deep space. Payloads can be transported using a climber moving along the tether. However, obtaining a deeper comprehension of the precise dynamics of a space elevator is challenging. The tether could have various deformations such as elongation, bending, and torsion owing to its flexible nature and the low level of vibration damping in space. Therefore, understanding those effects on the tether is essential for the design concept of a space elevator. Reproducing the behavior of space tether systems on the ground is challenging, which is primarily due to the scale of the system and the difficulty of accurately replicating a space environment. Thus, high-fidelity numerical analysis methods are required to analyze the dynamic response of space elevators precisely. Previously proposed analysis models of space tether systems with climbers have focused on elongation, bending, and rigid body motion of the tether, and the effect of torsional deformation has been neglected. However, a tether can be twisted easily owing to its low torsional stiffness. This study established high-fidelity numerical simulation models for space elevators considering large deformations including the torsion of a tether. This study developed a flexible multibody model with a moving climber using the absolute nodal coordinate formulation with 14 degrees of freedom. Further, the gravitational perturbation caused by the non-sphericity of the Earth was considered. Using the constructed model, the motion and deformation of nonequatorial space elevators caused by the climber motion and the disturbance in the space environment were investigated. The obtained results indicate that gravitational perturbation can induce torsional deformation, particularly at higher anchor latitudes.

Effect of torsional deformation on microstructure and mechanical properties of pure copper

This study investigates the influence of torsional deformation with different equivalent strains on the microstructural evolution and mechanical properties in pure copper at room temperature. The grain size exhibits a gradient distribution pattern with decreasing shear strains. Texture analysis reveals the development of a typical torsion texture during deformation. And the texture component is significantly influenced by the strain level. In samples subjected to low strain at the center position, the dominant texture components are mainly A and A* components. As strain increases in the 1/4 layer sample region, there is a gradual decrease in strength for A* component, while A component remains dominant; additionally, B and C textures exhibit increased strength. At positions subjected to maximum strain near the surface area, B texture replaces A as the strongest texture component. Results also indicate that torsional deformation enhances hardness, strength, and plasticity due to dislocation strengthening, fine grain strengthening and synergistic effects during deformation. Furthermore, the formation of torsional texture during this process may contribute to improved plasticity.

Theoretical study on the effect of torsional deformation on WTe2 as a cathode material for calcium ion batteries.

In this study, the electronic structure and diffusion barrier of the Ca-adsorbed WTe2 system under different torsion angles were calculated based on the first-principles method. The results show that the structure and properties of the pure WTe2 system and Ca-adsorbed WTe2 system are affected by torsional deformation. When the torsion angle is 6°, the intrinsic WTe2 changes from a direct band gap to an indirect band gap. The torsional deformation does not change the metallicity of the Ca-adsorbed WTe2 system. The Ca-d state electrons contribute to the electron density of WTe2. The calculation of the diffusion barrier shows that the torsion deformation promotes the diffusion of calcium on the surface of WTe2. This study provides a theoretical basis for the regulation of electrode materials. In this study, Materials Studio 8.0 software was used to construct the WTe2 model and Ca-adsorbed WTe2 model, and CASTEP module was used for first-principles calculation.

Effect of torsional deformation on electronic structure and optical properties of silicon-doped WS2

In this paper, the structural, electrical and optical effects of WS2 doped with silicon atoms after torsional deformation are investigated using first-principles calculations. First-principles calculations for metal disulfide-WS2. The doping of Si atoms gives WS2 a tunable band gap, and the surface state is successfully transformed from a 2.0[Formula: see text]eV band gap to a quasi-metal with a 0.254[Formula: see text]eV band gap, and the change of the doped Si atoms causes a redshift in the absorption peak and a blueshift in the reflection peak. The band gap of WS2 can be effectively adjusted by torsional deformation on the basis of Si-doped atoms in the range 0.254–0.052[Formula: see text]eV. Calculations of optical properties show that Si-doped WS2 with a torsion angle of [Formula: see text] has the lowest light absorption peak and Si-doped WS2 with a torsion angle of [Formula: see text] has the lowest light reflection peak. This paper opens up new possibilities for designing materials on demand.

Microstructure, properties and crystallographic orientation of novel austenitic Fe–26Mn-3.4Cr-0.4C steel under hot torsion process

An experimental austenitic twin-induced plasticity (TWIP) steel was deformed under hot torsion tests. Two different total equivalent strains (2.2 and 2.6) were employed in order to raise its yield strength while keeping reasonable toughness. The material was isothermally strained at 900 °C with a low strain rate of 0.05 s−1. The effects of torsional deformation on the microstructure, texture and mechanical properties of the TWIP steel were investigated and compared with the as-received samples. X-Ray Diffraction (XRD) measurements were performed to identify the phases present in the metal before and after the thermomechanical process. Scanning electron microscopy (SEM), Electron backscatter diffraction (EBSD), Orientation distribution function (ODF) analysis and tensile experiments complemented the investigation of this research. The main deformation mechanism changed from conventional sliding inside the grain to nucleated twinning from the grain boundaries, which led to the decrease of the grain size to less than 1 μm (UFG - Ultrafine Grains). The results indicate that the transition in the deformation mechanisms is dependent on grain size associated with the flow profile of the material. This was due to changes in the dislocation density within the grain and the movement of dislocations around the yield point. No martensitic transformation was detected during the strain and neither from the twinning mechanism in the microstructure after the torsion deformation. The best balance between high strength and good ductility (920 MPa and 52%) was obtained after the total equivalent strain of 2.6. It was verified that the employed thermomechanical schedule affects the displacement of the substructure with the formation of sub-grains influencing the hardening behavior, texture and yield strength of the metal.

Effect of torsional deformation on crystallographic evolution of carbide-free nano-bainitic steels prepared at two different austempering temperatures

The current study investigates the nature and extent of crystallographic change after torsional deformation in nano-structured bainite. This is extremely useful as nano-structured bainite is not stable under mechanical deformation and the evolved structure under torsion is finally going to determine other mechanical responses like fracture and fatigue. Two blocks of nano-bainitic steels were prepared after austenitization at 950°C and austempering at 250°C (NB250) and 350°C (NB350) respectively. It was found that there was a decrease in the bainitic ferrite (BF) and retained austenite (RA) length scale with a reduction in austempering temperature along with reduction in the RA content. Specimens from the undeformed two blocks (NB250-UD and NB350-UD) were subjected to torsional deformation till failure (NB250-T and NB350-T) and the crystallographic characteristics of the torsion-tested and undeformed specimens were obtained using electron back-scattered diffraction (EBSD). The orientation relationship (OR) between BF and RA for NB250-UD and NB350-UD was close to Kurdjumov-Sachs (K-S) which changed to predominantly Nishiyama Wassermann (NW) after torsion deformation (NB250-T and NB350-T). Significant refinement in packet and block was observed as a result of torsional deformation. Variant selection was stricter for NB350-UD than NB250-UD but torsional deformation led to weakening of variant selection. The extent of lowest misorientation V1-V4 variant pairing was higher for NB350-UD but it did not change much with torsion in case of NB250-T whereas NB350-T displayed a reduction. Fractography revealed that the dimple size corresponded to block size range between the undeformed and torsion-tested sample for the respective austempering condition.

Influence of Sulfur Defects on the Electronic and Optical Properties of Torsional NbS2: First‐Principles Calculation

For single‐layer NbS2, the effect of torsional deformation on the electronic structure of defect NbS2 is studied by first principles. The electronic structure changes caused by two defect states are recorded: energy band, bond length, defect formation energy, electronic state density, and differential charge density. Single‐air sulfur defect VS and double‐air sulfur defect V2S are studied. Based on the two states, the defect system is twisted. The results show that the indirect bandgap of NbS2 is successfully induced by twisting the defect system, and the single‐layer NbS2 is transited into a diluted semiconductor. At the same time, the electronic characteristics can be controlled regularly. On the other hand, the hybrid system can significantly improve the absorption coefficient and transmittance of single‐layer NbS2 in the visible light region, promote the reflection of ultraviolet light, and effectively improve the optical response and photocatalytic activity in the low‐energy region. The results herein lay a foundation for the flexible application of 1T‐NbS2 according to its electronic and optical properties.

Effect of Torsional Deformation on Spin–Orbit Interaction in Metallic Silicon Nanotubes

Effect of Torsional Deformation on Spin–Orbit Interaction in Metallic Silicon Nanotubes

Effect of Torsional Deformation on the Electrical and Optical Properties of Be Adsorbed Stanene

Effect of Torsional Deformation on the Electrical and Optical Properties of Be Adsorbed Stanene

Torsion induced topological deformations in C60

Computational torsional deformation experiments were performed under the framework of density functional theory with C60 based on the anisotropy in the molecule inducing different topological defects. The effects of torsional deformation on spheroid cage and strain energy were investigated. Different isomers possessing different strain energies during the deformation experiments were noticed. Stable as well as reactive isomers of C60 which could withstand high pressures were identified including those induced with Stone-Wales defect.

Effect of planar torsional deformation on the thermal conductivity of 2D nanomaterials: A molecular dynamics study

The thermal conductivity of nanoscale materials is largely dependent on the applied strain and deformations. In this paper, the effect of torsional deformation and consequent wrinkles on the thermal conductivity of graphene, hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS2) nanostructures have been investigated by performing non-equilibrium molecular dynamics simulation. The nanostructure geometry is considered as a ring with different inner and outer radii so that the torsional deformation is applied on the inner boundary. It is found that the wrinkles caused by applying the torsion, result in reducing the thermal conductivity of nanostructures. Although the effect of created distortions is tangible, these wrinkles have the most influence on the thermal conductivity of MoS2 and the least on the thermal conductivity of h-BN. The effect of inner radius size is also studied and found that the reduction of the thermal conductivity is enhanced by increasing the inner radius size. The results of this study can be beneficial to thermal applications of 2D nanostructures under mechanical stress or strain and also for estimating the values of applied torsion and wrinkle amplitude by measuring the thermal conductivity variations.

Influence of Torsion on Precipitation and Hardening Effects during Aging of an Extruded AZ91 Alloy

The effect of torsional deformation by various routes prior to artificial aging treatment on the microstructure of extruded AZ91 rods was investigated. The tension and compression properties along the extruded direction were tested to evaluate the hardening effect. The results showed that torsional deformation can largely enhance the subsequent age-hardening effect. A detailed microstructural characterization revealed that torsional deformation produced a high density of dislocations and {10-12} twins, which can promote continuous precipitation and increase the number density of the Mg17Al12 phase. In addition, part of dislocations and the {10-12} twins were retained after aging treatment. The combination of the increased precipitation hardening by Mg17Al12, dislocation strengthening and refinement strengthening contributed to the high hardening effect. Moreover, the hardening effect can be further increased by tailoring the torsion route. The torsion route exhibited little influence on the age-hardening effect, while it remarkably affected the texture of the twisted AZ91 rods. Reciprocating torsion had little influence on the texture. In contrast, unidirectional torsion caused the c-axis of the texture to rotate toward the extrusion direction, resulting in a texture softening effect. Therefore, combining reciprocating torsion and aging caused a higher hardening effect than combining unidirectional torsion and aging. The detailed strengthening mechanism was analyzed and is discussed.

A Nonlinear Tire Model to Describe an Unwanted Flat Vibrations of the Wheels

A simplified nonlinear mathematical tire model has been created. The model takes into account the radial and torsional stiffness of the tire, as well as the effect of radial deformation on torsional rigidity and, conversely, the effect of torsional deformation on radial rigidity. The results will be used to study the conditions for the occurrence of undesirable oscillations of vehicle wheels.

Dynamic Instability of High-Speed Rotating Shaft with Torsional Effect

Today’s design of machine rotor requires the rotor to operate at a high rotational speed to improve the efficiency of the machine. However, the existence of disturbances such as periodic axial load may cause parametric resonance to the rotor system in addition to the common force resonance. Previous studies on this parametric resonance of shaft typically included the element of translational and rotary inertia, gyroscopic moments and bending and shear deformation but surprisingly neglected the effect of the axial torque. This paper investigated the parametric instability behaviour of the shaft rotating at high speed while considering the torsional effect of the shaft. Based on the finite element method, a shaft model that includes torsional deformation as one of its degree of freedom was established. The Mathieu-Hill equation was derived, and then the Bolotin’s method was used to solve the equation by establishing the parametric instability chart. Two types of the rotary system were studied: a shaft with different boundary conditions and shaft with different bearing types. The results were initially validated with past findings. Following that the results were compared to the results correspond to the Timoshenko’s beam formulation that omits the torsional degree of freedom. The effect of axial torsional deformation was found to be very significant especially at high speed. The developed model in this study shows that at the shaft speed of 40000 rpm, the effect of torsional deformation has given the difference of more than 100% in the frequency ratios correspond to the 4DOF and 5DOF models for the case of fix-free boundary condition.

Effects of Torsional Deformation on the Mechanical Properties and Microstructures of a Commercial Pure Copper

The effects of torsional deformation on the mechanical properties and microstructural evolution of pure copper rods with cylindrical shape have been investigated in this study by twisting the rods by different numbers of revolution. The torsional deformation can introduce gradient hardness along the radial direction due to the formation of gradient grains and dislocation substructures along the radial direction. Tensile testing results indicated that the torsional deformation can significantly enhance the strength of pure copper with consuming the ductility. Due to the large grain size and relative high SFE of pure copper in this study, only gradient grain size and dislocation substructures formed along the radial direction after torsional deformation.

Electronic theoretical study on the influence of torsional deformation on the electronic structure and optical properties of BN-doped graphene

Based on the density functional theory, the effect of torsional deformation on the electronic structure and optical properties of boron nitride (BN)-doped graphene is studied by using the first-principles calculations. The band structure calculations show that the intrinsic graphene is a semi-metallic material with zero band gap and the torsional deformation has a large effect on its band gap, opening its band gap and turning it from the semi-metal to the medium band gap semiconductor. The doping of BN in graphene makes its band gap open and becomes a medium band gap semiconductor. When it is subjected to a torsional effect, it is found to have a weak influence on its band gap. In other words, the doping of BN makes the changes of the band gap of graphene no longer sensitive to torsional deformation. Optical properties show that the doping of BN leads to a significant decrease in the light absorption coefficient and reflectivity of the graphene at the characteristic peak and that of BN-doped graphene system is also weakened by torsional deformation at the characteristic peak. In the absorption spectrum, the absorption peaks of the doping system of the torsion angle of 2–20[Formula: see text] are redshifted compared with that of the BN-doped system (the torsion angle is 0[Formula: see text]). In the reflection spectrum, the two reflection peaks are all redshifted relative to that of the BN-doped system (the torsion angle is 0[Formula: see text]) and when the torsion angle exceeds 12[Formula: see text], the size relationship between the two peaks is interchanged. The results of this paper are of guiding significance for the study of graphene-based nanotube devices in terms of deformation.

DFT Study on the Interaction of Paracetamol and Torsional Deformed Graphene

The interaction between paracetamol molecule and graphene sheet and the influence of torsional deformation on it were studied on the basis of density functional theory. Our results show that paracetamol molecule is physically adsorbed on the graphene sheet in a parallel adsorption model. Torsional deformation can change the bonding strength between paracetamol and graphene sheet, so by adjusting the deformation, the sustained and controlled release of drugs may be achieved. The results of global reactivity descriptors show that the stability of paracetamol-graphene complex is reduced by the presence of graphene, but the chemical activity is improved. The effect of torsional deformation is opposite to that of graphene. The paracetamol-graphene complex is easy to bond with electrophilic groups. The increased strain decreases the electrophilic ability of paracetamol-graphene complex. Analysis confirms that global reactivity descriptors have reasonably good correlation with the solubility and dispersion of paracetamol graphene complex,but they cannot be used to determine the pharmacological activity of drugs. Analysis of frontier orbitals and Fukui indices suggests that the active sites of the paracetamol include benzene rings, phenolic hydroxyl groups (electrophilic active site) and carbonyl group (both the nucleophilic and electrophilic active sites). For paracetamol-graphene complex, the active sites are mainly distributed from the graphene, there is almost no the active sites distribution on the paracetamol molecule. Hence, we can deduce that paracetamol will not exert its efficacy before it dissolves from the paracetamol-graphene complex, as a result, the efficacy of the paracetamol can be controlled by graphene carriers.

Effects of torsional deformation on the microstructures and mechanical properties of a CoCrFeNiMo0.15 high-entropy alloy

The effects of torsional deformation on the microstructures and mechanical properties of a CoCrFeNiMo0.15 high-entropy alloy have been investigated. The torsional deformation generates a gradient microstructure distribution due to the gradient torsional strain. Both dislocation activity and deformation twinning dominated the torsional deformation process. With increasing the torsional equivalent strain, the microstructural evolution can be described as follows: (1) formation of pile-up dislocations parallel to the trace of {1 1 1}-type slip planes; (2) formation of Taylor lattices; (3) formation of highly dense dislocation walls; (3) formation of microbands and deformation twins. The extremely high deformation strain (strained to fracture) results in the activation of wavy slip. The tensile strength is very sensitive to the torsional deformation, and increases significantly with increasing the torsional angle.

Electron-theoretical study on the influences of torsional deformation on electrical and optical properties of O atom absorbed graphene

The effects of torsional deformation on the structural stability, the electronic structures and the optical properties, including adsorption energy, band gap, absorption coefficient and reflectivity of O atom adsorbed graphene are studied by using the first-principles calculations. Our results indicate that the C atom closest to O atom is pulled up, causing the graphene plane to be distorted after the O atom has been adsorbed. The adsorption energy calculations show that due to the adsorption of O atom, the structural stability of graphene system decreases, but the degree of torsion has a weak effect on the structural stability. The analysis of band structure shows that the adsorption of O atom causes the graphene to convert into a semiconductor from a metal. Torsional deformation makes it change from a semiconductor to a metal, and to a semiconductor. The O atom adsorption system with a torsion angle of 12° has an indirect band gap but the band gaps of other systems are all direct bandgaps. Compared with the intrinsic graphene torsion system, the adsorbed O atom system has an electronic structure that is less sensitive to torsional deformation. When the torsion angle changes from 10° to 16°, the bandgap is always stable at around 0.11 eV. And the adsorption system always corresponds to a narrow bandgap semiconductor in this torsion angle range. For optical properties, comparing with the O atoms adsorbed on graphene with the 0° torsion angle, the peaks of the absorption coefficient and the reflectivity of the system are reduced, and have a transform of red shift into blue shift in a torsion angle ranging from 2° to 20°.