Torsional Properties Research Articles

The connections of pseudo-Finsler spaces

We give an introduction to (pseudo-)Finsler geometry and its connections. For most results we provide short and self-contained proofs. Our study of the Berwald nonlinear connection is framed into the theory of connections over general fibered spaces pioneered by Mangiarotti, Modugno and other scholars. The main identities for the linear Finsler connection are presented in the general case, and then specialized to some notable cases like Berwald's, Cartan's or Chern–Rund's. In this way it becomes easy to compare them and see the advantages of one connection over the other. Since we introduce two soldering forms we are able to characterize the notable Finsler connections in terms of their torsion properties. As an application, the curvature symmetries implied by the compatibility with a metric suggest that in Finslerian generalizations of general relativity the mean Cartan torsion vanishes. This observation allows us to obtain dynamical equations which imply a satisfactory conservation law. The work ends with a discussion of yet another Finsler connection which has some advantages over Cartan's and Chern–Rund's.

Tuning the Shear Modulus of Single-Walled Carbon Nanotube by Feeding Van Der Waals Molecules

Torsional buckling of single-walled carbon nanotubes filled with light weight molecular via molecular dynamics is reported. The model accounts for the deformation of CNTs, and interactions among gas molecules; between gas and carbon atoms. The effect of particle loading is predicted to significantly change CNT’s critical torsional moment and stiffness. This is therefore an approach by which the torsional mechanical properties and oscillation frequencies of carbon nanotubes may be tuned. Importantly, the predicted changes in torsional siffness are unique relative to conventional linear elastic materials and are indicative of nonlinear oscillations due to nonlinear mechanical effects. CNTs subjects to large deformations reversibly switch into different morphological patterns. Each shape change corresponds to an abrupt release of energy and a singularity in the stress-strain curve. At higher torsional angle, van der Waals (VDW: He, Ar, H2) molecules reveal a stability effect on carbon nanotubes.

Torsional Characteristics of Single Walled Carbon Nanotube with Water Interactions by Using Molecular Dynamics Simulation

The torsional characteristics of single walled carbon nanotube (SWCNT) with water interactions are studied in this work using molecular dynamics simulation method. The torsional properties of carbon nanotubes (CNTs) in a hydrodynamic environment such as water are critical for its key role in determining the lifetime and stability of CNT based nano-fluidic devices. The effect of chirality, defects and the density of water encapsulation is studied by subjecting the SWCNT to torsion. The findings show that the torsional strength of SWCNT decreases due to interaction of water molecules and presence of defects in the SWCNT. Additionally, for the case of water molecules encapsulated inside SWCNT, the torsional response depends on the density of packing of water molecules. Our findings and conclusions obtained from this paper is expected to further compliment the potential applications of CNTs as promising candidates for applications in nano-biological and nano-fluidic devices.

Torsional Characteristics of SingleWalled Carbon Nanotube with Water Interactions by Using Molecular Dynamics Simulation

Abstract The torsional characteristics of single walled carbon nanotube (SWCNT) with water interactions are studied in this work using molecular dynamics simulation method. The torsional properties of carbon nanotubes (CNTs) in a hydrodynamic environment such as water are critical for its key role in determining the lifetime and stability of CNT based nano-fluidic devices. The effect of chirality, defects and the density of water encapsulation is studied by subjecting the SWCNT to torsion. The findings show that the torsional strength of SWCNT decreases due to interaction of water molecules and presence of defects in the SWCNT. Additionally, for the case of water molecules encapsulated inside SWCNT, the torsional response depends on the density of packing of water molecules. Our findings and conclusions obtained from this paper is expected to further compliment the potential applications of CNTs as promising candidates for applications in nano-biological and nano-fluidic devices.

Torsional buckling behavior of boron-nitride nanotubes using molecular dynamics simulations

Based on molecular dynamics simulations, the mechanical properties and buckling behavior of boron-nitride nanotubes under the action of torsional load are investigated. According to the results, the torsional properties of a boron-nitride nanotube are higher than those of its carbon counterpart. The effect of geometrical parameters on these parameters is also investigated. It is observed that by increasing the radius of nanotubes of the same length, unlike the critical shear strain, the critical torque considerably increases. The effect of chirality is also found to be negligible in the cases of critical shear strain and buckling mode, unlike the critical torque.

Tensile, Hardness, and Torsion Behavior of Welded AA

Tensile, Torsion, and Hardness behavior of welded and un-welded Aluminium Alloy 6061 T6 were investigated. Tests were conducted to evaluate the impact of tungsten Gas Arc welding (TIG) on some of the mechanical properties of the alloy. Different zones with different mechanical properties were created as a result of the welding process. Welding was found to have enormous impact on the tensile, torsion, and hardness properties of the alloy. Welded tensile specimens were failed at the welded area whereas not welded ones were failed at the centre. Welded torsion specimens were failed at the HAZ but not welded ones failed at the centre. The hardness of HAZ was decreased as a result of the heat generated during the welding process. Hardness values were increased as we moved away from the welded region.

TORSIONAL WAVE PROPAGATION AND VIBRATION OF CIRCULAR NANOSTRUCTURES BASED ON NONLOCAL ELASTICITY THEORY

The presence of size effects represented by a small nanoscale on torsional wave propagation properties of circular nanostructure, such as nanoshafts, nanorods and nanotubes, is investigated. Based on the nonlocal elasticity theory, the dynamic equation of motion for the structure is formulated. By using the derived equation, simple analytical solutions for the relation between wavenumber and frequency via the differential nonlocal constitutive relation and the numerical solutions for a discrete nonlocal model via the integral nonlocal constitutive relation have been obtained. This results not only show that the dispersion characteristics of circular nanostructures are greatly affected by the small nanoscale and the classical theory overestimates the stiffness of nanostructures, but also highlights the significance of the integral nonlocal model which is able to capture some boundary characteristics that do not appear in the differential nonlocal model.

Torsional properties of distal femoral cortical defects.

The optimal management of pathologic long bone lesions remains a challenge in orthopedic surgery. The goal of the current study was to investigate the effect of defect depth on the torsional properties of the distal femur. A laterally placed distal metaphyseal cylindrical defect was milled in the cortex of the distal femur in 20 composite models. The proximal extent of the defects was constant. By decreasing the radius of the cylinder that intersected this predefined cord, 4 different radii defining 4 different depths of resection of the distal femur were created for testing: 17%, 33%, 50%, and 67% cortical defects, when normalized to the width of the femur at the level of resection. Each femur was mounted into a hydraulic axial/torsion materials testing machine and each specimen underwent torsional stiffness testing and torsional failure in external rotation. The specimens with less than a 33% cortical loss consistently demonstrated a superiorly oriented spiral fracture pattern, while the specimens with greater than a 50% cortical loss consistently demonstrated an inferiorly oriented transverse fracture pattern. The cortical defects were all statistically (P<.05) less stiff in torsion as the defect grew larger. There was a strong linear correlation between the mean torsional stiffness and cortical defect size (r(2)=0.977). This observation is supported by finite element analysis. The amount of femur remaining is crucial to stability. This biomechanical analysis predicts a critical loss of torsional integrity when a cortical defect approaches 50% of the width of the femur.

Effect of Fatigue on Torsional Failure of Nickel-Titanium Controlled Memory Instruments

IntroductionThe purpose of this study was to understand how fatigue affects the torsional properties of both traditional nickel-titanium (NiTi) and NiTi controlled memory (CM) files. MethodsTyphoon (TYP; Clinician's Choice Dental Products, New Milford, CT) 25/.04 and 40/.04 rotary files in both NiTi and CM were tested to obtain the mean number of cycles of failure (Nf) using a 3-point bending apparatus. New files were then precycled to 4 conditions (0%, 25%, 50%, and 75% of the Nf), and torsional resistance tests were performed. Each file was exposed to torsional stress until failure, and at that point the torque and distortion angles were measured. The fracture surface of each fragment was examined with a scanning electron microscope. ResultsTYP CM files had an Nf 7 times higher than that of TYP files (P < .05). No difference in torque between the CM files and the conventional NiTi files of either file size was detected (P > .05). The torque of the size 40/.04 files was significantly higher than the torque of the size 25/.04 files (P < .05). In the 40/.04 files group, TYP files in the 75% precycling group had a significantly lower torque than files in the group with no precycling (P < .05), whereas slight precycling (25%) significantly reduced the distortion angle on TYP CM files (P < .05). The CM files of both sizes had a significantly higher distortion angle than the corresponding NiTi files (P < .05). The fractured files in the precycling groups showed the typical pattern of torsional failure. ConclusionsWithin the same amount of precycling (25%, 50%, and 75%), the cyclic fatigue life of TYP CM instruments was significantly higher than that of the TYP instruments. However, the torque value of TYP CM was similar to TYP files. The larger instruments were not only less resistant to cyclic fatigue but were affected most by prestressing of both TYP and TYP CM files.

Evaluation of Bending and Torsional Properties of Different Ice Hockey Sticks

The purpose of this study was to develop a measurement setup to identify bending and torsional properties of ice hockey sticks with similar stiffness and length from various manufacturers during static bending and torsion tests on a test stand. The test stand is composed of a clamp system, a spindle lifting gear with a load cell and three distance sensors. For the bending test the ice hockey sticks were clamped to the test stand and a three point load test simulated real conditions. To bend the stick identically to an actual wrist shot the supports were positioned in order that the distance of the supports conforms to the distance between the hands of an ice hockey player during a wrist shot. Three different loads of 150, 200 and 250N were applied on ten test positions along the hockey sticks’ shaft and blade. For the torsion test the hockey sticks were also clamped to the test stand, but the second support was removed. A special rotatable frame was mounted on five different positions along the shaft down to the blade where torque was applied (29, 43.5 and 58Nm). The bending test showed that the differences increase with increasing distance to clamping position and higher loads. At each position the deviation of stick B is higher compared to the deviation of stick A, despite similar FLEX values. The results for the torsion tests show that the torsion of stick A is higher compared to the torsion of stick B. This trend could be observed at each position and torque. With the same torque applied at the same position the torsion angle of stick A is twice as high compared to stick B. Based on the findings of this research further studies of how the different bending and torsional properties affect the accuracy and speed of actual wrist shots will be performed in the near future.

Effect of Surface Crack and its Size on Mechanical Characteristics of Gold Nano-wires

Nano-crystalline materials are well known for properties resulting from well ordered structure and lack of unevenness due to presence of defects like cracks, inclusions, voids etc. Occurrence of these defects in nano-crystalline materials cannot be ignored and their presence strongly influences many of the properties of the materials. In present study, atomistic simulations have been used to investigate the torsional mechanical properties of gold nano-wires having surface-crack like defect. Cracks with its length parallel to nano-wire axis and its width lying in radial direction, carrying various depths have been created on the nano-wire surface. Crack is positioned at center of nano-wire in longitudinal direction. On the cross-section of the nano-wire, loading is applied at a particular twisting rate. The inter-atomic interactions are represented by employing Embedded Atom Potential (EAM). The effect of different sizes of the crack on strain energy due to twisting, torsional stiffness (or torsional rigidity) of the nano-wire has been investigated. It is predicted from our simulations that there is significant effect of the surface crack and its size on the mechanical properties of the gold nano-wire.

Asymmetric Illumination of Optically Anisotropic Beads for Detecting Rotational Motion

Many biological molecules, including RNA polymerases and ATP synthases, undergo rotational motion during their biological processes. Characterizing these processes at the single molecule level with high temporal and spatial resolution can reveal valuable information about their mechanical and dynamical properties. We are particularly interested in the dynamics of conformational changes of DNA molecules under torsion. Toward this long term goal we have developed a methodology that enables us to directly record the angular displacement of particles undergoing rotational motion by using asymmetric illumination of optically anisotropic beads. The method is implemented by illuminating a partially metal-coated bead with a laser beam coupled into the back side of the objective. The laser beam illuminating beads in the sample plane is oriented at an oblique angle to form asymmetric illumination. We observe that the scattering signal of the bead changes with the angular displacement of the coating on the bead relative to the illuminating laser beam. We use an optoelectronic system to detect scattering signal which is the direct high-speed measurement of the angular displacement of the bead. We conclude that our method is able to map angular displacements to electrical signal and we can determine the angular displacement of the biological molecule when conjugated to the bead. Our method obviates image acquisition and image processing procedures commonly used in previous studies, and it has the potential to significantly enhance the bandwidth of detection. We envision usage of this method in a range of biophysical measurements including magnetic trapping, tethered particle motion. We plan to use this rotational tracking method in combination with magnetic tweezers, a single-molecule technique that enables the application of torsional stress to twist single DNA molecules to extract high bandwidth torsional mechanical properties and dynamics of the molecules.

Buckling resistance, bending stiffness, and torsional resistance of various instruments for canal exploration and glide path preparation.

ObjectivesThis study compared the mechanical properties of various instruments for canal exploration and glide-path preparations.Materials and MethodsThe buckling resistance, bending stiffness, ultimate torsional strength, and fracture angle under torsional load were compared for C+ file (CP, Dentsply Maillefer), M access K-file (MA, Dentsply Maillefer), Mani K-file (MN, Mani), and NiTiFlex K-file (NT, Dentsply Maillefer). The files of ISO size #15 and a shaft length of 25 mm were selected. For measuring buckling resistance (n = 10), the files were loaded in the axial direction of the shaft, and the maximum load was measured during the files' deflection. The files (n = 10) were fixed at 3-mm from the tip and then bent 45° with respect to their long axis, while the bending force was recorded by a load cell. For measuring the torsional properties, the files (n = 10) were also fixed at 3-mm, and clockwise rotations (2-rpm) were applied to the files in a straight state. The torsional load and the distortion angle were recorded until the files succumbed to the torque.ResultsThe CP was shown to require the highest load to buckle and bend the files, and the NT showed the least. While MA and MN showed similar buckling resistances, MN showed higher bending stiffness than MA. The NT had the lowest bending stiffness and ultimate torsional strength (p < 0.05).ConclusionsThe tested instruments showed different mechanical properties depending on the evaluated parameters. CP and NT files were revealed to be the stiffest and the most flexible instruments, respectively.

Finite element model of the cyclic bending behavior of hollow structural sections

Hollow structural sections (HSS) are desirable for utilization in structural applications due to their inherent flexural, compression, and torsional properties. These sections are highly efficient, but have been underutilized in cyclic bending applications due to a lack of understanding of their behavior under these loads. To address the limited experimental data and determine potential limiting parameters for the use of HSS in seismic bending applications, a finite element model (FEM) considering experimentally measured material properties, section geometry, and geometric imperfections has been calibrated and validated to experimental findings. A parametric study is conducted on 133 different standard HSS beam members of sizes ranging from HSS 152×50.8×4.8 to HSS 508×305×15.9. To provide insight into the parameters that limit stable hysteretic behavior, the decrease in the overall maximum moment capacity with cycling at a given rotation level, rotational capacity at a given degradation of the moment capacity, and decrease of the secant stiffness with cycling are considered. The findings provide information about the interdependence of the width–thickness and depth–thickness ratios on the cyclic bending behavior of HSS. Linear regression analyses provide a relationship between the width–thickness and depth–thickness ratios and member performance from which equations for predicting the degradation of moment capacity and rotational capacity can be defined.

Structural, torsional, vibrational and response electric properties of 2,2′-bitellurophene rotamers. An ab initio and density functional theory investigation

The molecular structure, conformational behaviour, vibrational spectra and electronic (hyper)polarizabilities of tellurophene and 2,2′-bitellurophene rotamers were determined in gas by correlated ab initio and density functional theory calculations. The torsional potential for the rotation around the C2–C2′ inter-ring bond shows two minima corresponding to anti-gauche and syn-gauche structures and three maxima to planar anti and syn forms and to perpendicular conformation. The potential energy curve is rather flat over the entire 0°–180° twisting range and free rotation cannot be excluded. The IR and Raman spectra of the gauche structures are rather similar to each other, vibrational transitions being scarcely helpful for an unambiguous identification of the rotamers. The dipole moment and the first-order hyperpolarizability increase on passing from the anti-gauche to the syn-gauche conformation by a factor of five and four, respectively. The second harmonic generation nonlinear optical process can be useful to identify the 2,2′-bitellurophene rotamers. On the other hand, the electronic polarizabilities of these structures are much more closer to each other, being predicted to be within 2–13 %.

Optically probing torsional superelasticity in spider silks

We investigate torsion mechanics of various spider silks using a sensitive optical technique. We find that spider silks are torsionally superelastic in that they can reversibly withstand great torsion strains of over 102−3 rotations per cm before failure. Among various silks from a spider, we find the failure twist-strain is greatest in the sticky capture silk followed by dragline and egg-case silk. Our in situ laser-diffraction measurements reveal that torsional strains on the silks induce a nano-scale transverse compression in its diameter that is linear and reversible. These unique torsional properties of the silks could find applications in silk-based materials and devices.

Prediction of Elastic Mechanical Behavior and Stability of Single-Walled Carbon Nanotubes Using Bar Elements

A computationally effective structural mechanics approach based on the exclusive use of bar elements is developed in order to test its efficiency to predict the elastic longitudinal, torsional, and radial mechanical properties of zigzag, chiral, and armchair single-walled carbon nanotubes (SWCNTs). In addition, the proposed method is used for the investigation of the stability of SWCNTs under compressive and radial loads. The proposed model uses three-dimensional, two-noded, linear bar finite elements of three degrees-of-freedom per node to represent the force field appearing between carbon atoms due to the basic interatomic interactions. The numerical results, which are compared with corresponding data given in the open literature, demonstrate the convergence and stability of the method in predicting the elastic properties and critical forces that cause the instability of the tubes. The effect of chirality, length, and radius of carbon nanotubes on numerical predictions is thoroughly and clearly demonstrated.

The Effects on Tensile Properties of Different Winding Way on GFRP Bar

The influence of different surface forms on GFRP reinforcement mainly manifest in bonding between reinforcement materials and concrete, especially when the GFRP bars are used in slope, the form of the surface of GFRP bar will affect reinforced materials torsion and shear properties directly. This article made some tensile tests on several different surface forms of GFRP reinforcement, and learned that the form of the surface wound of GFRP bar make the influence on tensile strength, ultimate elongation and modulus of elasticity. Test results show that the surface of the winding way will affect on the tensile strength, ultimate elongation and modulus of elasticity of GFRP bar.

Failure Analysis of Motor Tire Bead Wires During Torsion Test

Torsion testing is used to determine the quality of steel wire used for motor tire beads in pneumatic tires. These steel wires must have good-tensile strength so that the tire bead can support the finished tire safely, and yet retain adequate ductility to deform easily around the forming wheel. The present paper highlights premature failure of bead wire which failed during torsion test. Torsion property is one of the important parameters of tire bead as it monitors both the metallurgical soundness and surface quality of a drawn wire. From the analysis, it has been concluded that probable reason for premature failure is due to strain aging (dynamic and static) caused by interstitial atoms which bounds the mobile dislocations resulting in increases yield strength and decreases bead formability. Moreover, the microstructural study indicates that failed specimen has misaligned and broken lamella of pearlite with globular cementite which creates the array of voids. These voids hinder the rotation of pearlite during torsion test thus leading to brittle fracture.

Torsional, tensile and structural properties of acrylonitrile–butadiene–styrene clay nanocomposites

Torsional and tensile behaviour of acrylonitrile–butadiene–styrene (ABS)-clay nano-composites have been investigated and correlated with morphological and rheological characterisations. Nano-composites of ABS are prepared by melt compounding with different loading levels of nanoclay (Cloisite 30B) in a twin screw extruder and have been characterised in terms of torsional, axial and impact behaviour for their application in external orthotic devices. Tensile stress strain curve of nanocomposites are investigated to quantify resilience, toughness and ductility. Torque values of the nanocomposites are observed under torsion (10°–90°) and compared with that of neat ABS. Performance of ABS under torsional load improved by addition of nanoclay. Both modulus of elasticity and rigidity are found to improve in presence of nanoclay. State of dispersion in nano-composites is investigated using conventional methods such as transmission electron microscopy (TEM), X-ray diffraction (XRD), as well as by parallel plate rheometry. Addition of clay exhibits shear thinning effect and results in increase in storage modulus as well as complex viscosity of the nanocomposites. Zero shear viscosity rises tenfold with 1–2% addition of nanoclay, indicating the formation of structural network. It is found that state of dispersion of nanoclay governs the torsional and mechanical properties in ABS-clay nanocomposites.