Torsional Properties Research Articles

Flexural and torsional properties of a glass fiber-reinforced composite diaphyseal bone model with multidirectional fiber orientation

Although widely used, metallic implants have certain drawbacks in reconstructive bone surgery. Their high stiffness in respect to cortical bone can lead to complications which include periprosthetic fractures and aseptic loosening. In contrast to metallic alloys, fiber-reinforced composites (FRC) composed of a thermoset polymer matrix reinforced with continuous E-glass fibers have elastic properties matching those of bone. We investigated the mechanical properties of straight FRC tubes and FRC bone models representing the diaphysis of rabbit femur prepared from glass fiber/bisphenol A glycidyl methacrylate (BisGMA) - triethylene glycol dimethacrylate (TEGDMA) composite in three-point bending and torsion. Three groups of straight FRC tubes with different fiber orientations were mechanically tested to determine the best design for the FRC bone model. Tube 1 consisted most axially oriented unidirectional fiber roving and fewest bidirectional fiber sleevings. Fiber composition of tube 3 was the opposite. Tube 2 had moderate composition of both fiber types. Tube 2 resisted highest stresses in the mechanical tests and its fiber composition was selected for the FRC bone model. FRC bone model specimens were then prepared and the mechanical properties were compared with those of cadaver rabbit femora. In three-point bending, FRC bone models resisted 39-54% higher maximum load than rabbit femora with similar flexural stiffness. In torsion, FRC bone models resisted 31% higher maximum torque (p < 0.001) and were 38% more rigid (p = 0.001) than rabbit femora. Glass fiber-reinforced composites have good biocompatibility and from a biomechanical perspective, they could be used even in reconstruction of segmental diaphyseal defects. Development of an implant applicable for clinical use requires further studies.

Effects of Level, Loading Rate, Injury and Repair on Biomechanical Response of Ovine Cervical Intervertebral Discs.

A need exists for pre-clinical large animal models of the spine to translate biomaterials capable of repairing intervertebral disc (IVD) defects. This study characterized the effects of cervical spinal level, loading rate, injury and repair with genipin-crosslinked fibrin (FibGen) on axial and torsional mechanics in an ovine cervical spine model. Cervical IVDs C2-C7 from nine animals were tested with cyclic tension-compression (-240 to 100N) and cyclic torsion (± 2° and ± 4°) tests at three rates (0.1, 1 and 2Hz) in intact, injured and repaired conditions. Intact IVDs from upper cervical levels (C2-C4) had significantly higher torque range and torsional stiffness and significantly lower axial range of motion (ROM) and tensile compliance than IVDs from lower cervical levels (C5-C7). A tenfold increase in loading rate significantly increased torque range and torsional stiffness 4-8% (depending on amplitude) (p < 0.001). When normalized to intact, FibGen significantly restored torque range (FibGen: 0.96 ± 0.14, Injury: 0.88 ± 0.14, p = 0.03) and axial ROM (FibGen: 1.00 ± 0.05, Injury: 1.04 ± 0.15, p = 0.02) compared to Injury, with a values of 1 indicating full repair. Cervical spinal level must be considered for controlling biomechanical evaluations, and FibGen restored some torsional and axial biomechanical properties to intact levels.

Quantitative Theoretical Predictions and Qualitative Bonding Analysis of the Divinylborinium System and Its Al, Ga, In, and Tl Congeners.

A substituted divinylborinium cation was synthesized recently and characterized crystallographically as a gauche structure with a 153° C1-C2-C3-C4 dihedral angle. A full theoretical geometrical optimization of the bis(2-mesityl-1,2-diphenylvinyl)-borane cation shows excellent agreement with the crystal structure. However, for the parent unsubstituted divinylborinium cation, we predict a nearly 90° C1-C2-C3-C4 dihedral angle using the CCSD(T)/cc-pVTZ coupled cluster method. The cis and trans planar geometries (0° and 180° for the C1-C2-C3-C4 dihedral angle) proved to be transition states with energy barriers of 2.8 and 2.3 kcal/mol, respectively, with respect to unimolecular conversion to the gauche equilibrium. The structures of the heavier boron group cations (Al, Ga, In, and Tl) have also been investigated here, finding even lower energy barriers (0.3-0.7 kcal/mol). After the ZPVE corrections, the barriers are further decreased. The torsional angles for the unknown Al, Ga, In, and Tl dimesityl substituted compounds should be somewhat less than 153°. Many of these findings may be understood in terms of qualitative electronic structure theory. The torsional folding of borane complex, including cationic divinylborinium and elementary vinylborane (C2H3BH2) or chlorovinylborane (C2H3BHCl) precursors, are investigated with natural bond orbital (NBO) analysis to unveil the electronic origins of the torsional properties. The NBO-based descriptors are employed to systematically deconstruct complex torsional dependence into a balanced portrayal of hyperconjugative and steric effects.

Effects of Alloying Elements, Si and Cr, on Aging and Delamination Behaviors in Cold-Drawn and Subsequently Annealed Hyper-eutectoid Steel Wires

The effects of alloying elements, Cr and Si, and the conditions of hot-dip galvanizing on the aging behaviors and their related tensile and torsional properties in cold drawn hyper-eutectoid steel wires were investigated. The Cr and Si additions were found to increase tensile strength, but decrease the limit of drawing strain without delamination in cold drawn steel wires. The Cr and Si additions encouraged the suppression of age hardening and age softening during annealing. The increased amount of deformation in cold drawn steel wires made age hardening occur at the lower annealing temperature and shorter annealing time, and expanded the delamination region to high temperature during annealing. The additions of Cr and Si did not show the noticeable improvement of tensile strength without delamination in cold drawn steel wires, but increased the upper limit of tensile strength without delamination in cold drawn and annealed steel wires.

Thermo-mechanical performances of polypropylene biocomposites based on untreated, treated and compatibilized spent coffee grounds

Abstract In this work, biocomposites were produced by compounding polypropylene (PP) with spent coffee grounds (SCG) obtained after soluble coffee preparation. The samples were prepared by extrusion compounding and injection molding using different SCG contents (0, 5, 10, 15 and 20wt.) in order to investigate the effect of particle loading on the thermal, rheological and mechanical properties. Then, the effect of bleaching treatments and the use of compatibilizers (silane and styrene-ethylene-butene-styrene-graft-maleic anhydride) on the biocomposites properties at 15 wt% was examined. The results showed that good SCG dispersion and distribution into PP was achieved and that bleaching led to better interfacial interaction, which was further increased by using a coupling agent. As a result, the tensile and torsion properties were increased.

Torsional wave band gap properties in a circular plate of a two-dimensional generalized phononic crystal

The torsional wave band gap properties of a two-dimensional generalized phononic crystal (GPC) are investigated in this paper. The GPC structure considered is consisted of two different materials being arranged with radial and circumferential periodicities simultaneously. Based on the viewpoint of energy distribution and the finite element method, the power flow, energy density, sound intensity vector together with the stress field of the structure excited by torsional load are numerically calculated and discussed. Our results show that, the band gap of Bragg type exists in these two-dimensional composite structures, and the band gap range is mainly determined by radial periodicity while the circumferential periodicity would result in some transmission peaks within the band gap. These peaks are mainly produced by two different mechanisms, the energy leakage occurred in circumferential channels and the excitation of the local eigenmodes of certain scatterers. These results may be useful in torsional vibration control for various rotational parts and components, and in the application of energy harvesting, etc.

Twisted Alexander invariants of complex hypersurface complements

We define and study twisted Alexander-type invariants of complex hypersurface complements. We investigate torsion properties for the twisted Alexander modules and extend the local-to-global divisibility results of Maxim and of Dimca and Libgober to the twisted setting. In the process, we also study the splitting fields containing the roots of the corresponding twisted Alexander polynomials.

Torsional and axial compressive properties of tibiotarsal bones of red-tailed hawks (Buteo jamaicensis).

OBJECTIVE To describe the torsional and axial compressive properties of tibiotarsal bones of red-tailed hawks (Buteo jamaicensis). SAMPLE 16 cadaveric tibiotarsal bones from 8 red-tailed hawks. PROCEDURES 1 tibiotarsal bone from each bird was randomly assigned to be tested in torsion, and the contralateral bone was tested in axial compression. Intact bones were monotonically loaded in either torsion (n = 8) or axial compression (8) to failure. Mechanical variables were derived from load-deformation curves. Fracture configurations were described. Effects of sex, limb side, and bone dimensions on mechanical properties were assessed with a mixed-model ANOVA. Correlations between equivalent torsional and compressive properties were determined. RESULTS Limb side and bone dimensions were not associated with any mechanical property. During compression tests, mean ultimate cumulative energy and postyield energy for female bones were significantly greater than those for male bones. All 8 bones developed a spiral diaphyseal fracture and a metaphyseal fissure or fracture during torsional tests. During compression tests, all bones developed a crushed metaphysis and a fissure or comminuted fracture of the diaphysis. Positive correlations were apparent between most yield and ultimate torsional and compressive properties. CONCLUSIONS AND CLINICAL RELEVANCE The torsional and axial compressive properties of tibiotarsal bones described in this study can be used as a reference for investigations into fixation methods for tibiotarsal fractures in red-tailed hawks. Although the comminuted and spiral diaphyseal fractures induced in this study were consistent with those observed in clinical practice, the metaphyseal disruption observed was not and warrants further research.

Effect of Dimension Parameters on the Torsion Property of A C/SiC Pipe

Through finite element numerical simulation and based on laminated plate theory, the effect of dimension on the torsion properties of uniform C/SiC composites pipe was studied to provide a theoretical guidance for preparing the C/SiC pipe with different dimensions. The results show that, with increasing length of pipe, the anti-torsion section coefficient of pipe increases whereas the torsion angle per unit length decreases. Increasing the length can improve the torsion property. Anti-torsion section coefficient rises with increasing internal radius, while the torsion angle per unit length decreases to a constant. With increasing thickness, the anti-torsion section coefficient increases whereas the amplitude decreases gradually, and the torsion angle per unit length is a constant. Increment of internal radius and thickness improves the torsion property finitely.

Characterization and analysis of torsion property of carbon fiber bundle combined with epoxy resin

This study established a torsion testing method for carbon fiber bundle combined epoxy resin and investigated torsional properties of several kinds of carbon fiber with different epoxy matrix. Torsion strength and modulus were calculated to characterize the torsional properties. The effects of testing conditions including aspect ratio of sample, testing speed and resin content in bundle on measured torsional results were ascertained for choosing appropriate conditions. Scanning electron microscope (SEM) observation on fractured sample and single fiber pull‐out test were carried out to illustrate the relationship between torsion property and the properties of carbon fiber, matrix, and interface. The experimental results show that the proposed method can obtain torsion strength and modulus with good data reliability using optimized testing conditions. Higher elongation of carbon fiber leads to larger torsion strength. SEM shows that low‐elongation carbon fiber tends to fail easier with brittle failure mode. Torsion modulus strongly depends on modulus of resin matrix, rather than tensile modulus of carbon fiber. Moreover, better interfacial adhesion between fiber and matrix results in large torsion strength when matrix elongation is at equivalent level. POLYM. COMPOS., 39:E2529–E2539, 2018. © 2018 Society of Plastics Engineers

Rotation of an optically trapped vaterite microsphere measured using rotational Doppler effect

The angular velocity of a vaterite microsphere spinning in the optical trap is measured using rotational Doppler effect. The perfectly spherical vaterite microspheres are synthesized via coprecipitation in the presence of silk fibroin nanospheres. When trapped by a circularly polarized beam, the vaterite microsphere is uniformly rotated in the trap center. The probe beams containing two Laguerre–Gaussian beams of opposite topological charge l = ± 7, l = ± 8, and l = ± 9 are illuminated on the spinning vaterite. By analyzing the backscattered light, a frequency shift is observed scaling with the rotation rate of the vaterite microsphere. The multiplicative enhancement of the frequency shift proportion to the topological charge has greatly improved the measurement precision. The reliability and practicability of this approach are verified through varying the topological charge of the probe beam and the trapping laser power. In consideration of the excellent measurement precision of the rotation frequency, this technique might be generally applicable in studying the torsional properties of micro-objects.

Measurement of epoxy film adhesive properties in torsion and tension using tubular butt joints

With the increasing amount of composite materials used for aircraft structures, structural bonding and bonded repairs are needed. However, a huge challenge is the availability of reliable material properties for the adhesives. A common approach for determining the material properties is to use adhesively bonded tubular butt joint specimens, tested in a biaxial testing system. In order to determine stress-strain curves of the adhesive systems local strain or deformation measurements needs to be performed. But because of the small bondline thickness of an e.g. epoxy film adhesive, the resulting deformations are very small. Within this study, two different strain measurement techniques are used. First a high resolution digital image correlation (DIC) system. Second capacitive sensors combined in a manner, which allows the decoupled measuring of axial and torsional movements. Both methods and results are compared and discussed. Both have their advantages and the ability to measure the small deformations.

Effects of {10–12} Twins on Dynamic Torsional Properties of Extruded AZ31 Magnesium Alloy

Effects of initial twins on dynamic torsional properties of extruded AZ31 alloy were investigated by introducing {10–12} twins into it through precompression to 3 and 6% strains along the extrusion direction and performing torsional testing at a strain rate of 1.4 × 103 s−1 using a torsional Kolsky bar system. The as-extruded sample without twins showed higher dynamic torsional properties than the precompressed samples with many initial twins; the maximum shear strength and fracture shear strain decreased with increasing amount of initial twins. In the as-extruded sample, twinning occurred vigorously throughout the gage section of the tubular specimen during high-strain-rate torsional tests, resulting in heavily deformed morphology, many macrocracks, and rough fractured surfaces. The increased amount of initial twins suppressed the twinning behavior and localized the applied torsional deformation; this resulted in an almost unchanged sample shape, no secondary cracks, and a flat fracture plane, thereby deteriorating the dynamic torsional properties of the extruded alloy.

Tensile and Torsional Structural Properties oftheNativeScapholunate Ligament.

The ideal material for reconstruction of the scapholunate interosseous ligament (SLIL) should replicate the mechanical properties of the native SLIL to recreate normal kinematics and prevent posttraumatic arthritis. The purpose of our study was to evaluate the cyclic torsional and tensile properties of the native SLIL and load to failure tensile properties of the dorsal SLIL. The SLIL bone complex was resected from 10 fresh-frozen cadavers. The scaphoid and lunate were secured in polymethylmethacrylate and mounted on a test machine that incorporated an x-y stage and universal joint, which permitted translations perpendicular to the rotation/pull axis as well as nonaxial angulations. After a 1 N preload, specimens underwent cyclic torsional testing (±0.45 N m flexion/extension at 0.5 Hz) and tensile testing (1-50 N at 1 Hz) for 500 cycles. Lastly, the dorsal 10 mm of the SLIL was isolated and displaced at 10 mm/min until failure. During intact SLIL cyclic torsional testing, the neutral zone was 29.7° ± 6.6° and the range of rotation 46.6° ± 7.1°. Stiffness in flexion and extension were 0.11 ± 0.02 and 0.12 ± 0.02 N m/deg, respectively. During cyclic tensile testing, the engagement length was 0.2 ± 0.1 mm, the mean stiffness was 276 ± 67 N/mm, and the range of displacement was 0.4 ± 0.1 mm. The dorsal SLIL displayed a 0.3 ± 0.2 mm engagement length, 240 ± 65 N/mm stiffness, peak load of 270 ± 91 N, and displacement at peak load of 1.8 ± 0.3 mm. We report the torsional properties of the SLIL. Our novel test setup allows for free rotation and translation, which reduces out-of-plane force application. This may explain our observation of greater dorsal SLIL load to failure than previous reports. By matching the natural ligament with respect to its tensile and torsional properties, we believe that reconstructions will better restore the natural kinematics of the wrist and lead to improved outcomes. Future clinical studies should aim to investigate this further.

Teriparatide (human PTH1-34) compensates for impaired fracture healing in COX-2 deficient mice.

Genetic ablation of cyclooxygenase-2 (COX-2) in mice is known to impair fracture healing. To determine if teriparatide (human PTH1-34) can promote healing of Cox-2-deficient fractures, we performed detailed in vivo analyses using a murine stabilized tibia fracture model. Periosteal progenitor cell proliferation as well as bony callus formation was markedly reduced in Cox-2-/- mice at day 10 post-fracture. Remarkably, intermittent PTH1-34 administration increased proliferation of periosteal progenitor cells, restored callus formation on day 7, and enhanced bone formation on days 10, 14 and 21 in Cox-2-deficient mice. PTH1-34 also increased biomechanical torsional properties at days 10 or 14 in all genotypes, consistent with enhanced bony callus formation by radiologic examinations. To determine the effects of intermittent PTH1-34 for callus remodeling, TRAP staining was performed. Intermittent PTH1-34 treatment increased the number of TRAP positive cells per total callus area on day 21 in Cox-2-/- fractures. Taken together, the present findings indicate that intermittent PTH1-34 treatment could compensate for COX-2 deficiency and improve impaired fracture healing in Cox-2-deficient mice.

Microstructure and Tribological Properties of Sub-Microcrystalline Carbon Steel Produced by Severe Plastic Deformation

The microstructure, hardness, and sliding wear properties of high-pressure torsion (HPT)-processed pure Fe and S45C carbon steel were comprehensively investigated. The grains of Fe and S45C were significantly refined to the submicron size range using the HPT process, and the grain sizes were found to decrease with an increased number of turns (N). The Vickers hardness of HPT-processed specimens increased with increasing N or with distance from the center (i.e., with an increase in the strain), which is attributed to grain refinement. In addition, the hardness of HPT-processed Fe was saturated with a further increase in the number of turns owing to the saturation of grain refinement. However, saturation with hardening was not observed in the case of S45C and the hardness values of S45C were much higher than those of Fe. The wear amount was considerably reduced by HPT processing for both Fe and S45C. A linear correlation was determined between the specific wear rate and the inverse of hardness, which agrees with the Archard wear equation. The experimental results show that the reduction in the wear of Fe and S45C is considered to be due to hardening by the HPT process.

Molecular dynamics simulation on the elastoplastic properties of copper nanowire under torsion

Influences of different factors on the torsion properties of single crystal copper nanowire are studied by molecular dynamics method. The length, torsional rate, and temperature of the nanowire are discussed at the elastic-plastic critical point. According to the average potential energy curve and shear stress curve, the elastic-plastic critical angle is determined. Also, the dislocation at elastoplastic critical points is analyzed. The simulation results show that the single crystal copper nanowire can be strengthened by lengthening the model, decreasing the torsional rate, and lowering the temperature. Moreover, atoms move violently and dislocation is more likely to occur with a higher temperature. This work mainly describes the mechanical behavior of the model under different states.

Torsion analysis of the anisotropic behavior of FDM technology

Several reports have studied the mechanical properties of the material extrusion additive manufacturing process, specifically referred to as fusion deposition modeling (FDM) developed by Stratasys. As the applications for 3D printed parts continue to grow in diversity (e.g., gears, propellers, and bearings), the loading conditions applied to printed parts have become more complex, and the need for thorough characterization is now paramount for increased adoption of 3D printing. To broaden the understanding of torsional properties, this study focused on the shear strength of specimens to observe the impact from additive manufacturing. A full factorial (42) design of experiments was used, considering the orientation and the raster angle as factors. XYZ, YXZ, ZXY, and XZY levels were considered for the orientation parameter, as well as 0°, 45°, 90°, and 45°/45° for the raster angle parameter. Ultimate shear strength, 0.2% yield strength, shear modulus, and fracture strain were used as response variables to identify the most optimal build parameters. Additionally, stress-strain diagrams are presented to contrast elastic and plastic regions with traditional injection molding. Results demonstrated an interaction of factors in all mechanical measured variables whenever an orientation and a raster angle were applied. Compared to injection molding, FDM specimens were similar for all measured torsion variables except for the fracture strain; this led to the conclusion that the FDM process can fabricate components with similar elastic properties but with less ductility than injection molding. The orientation in YXZ with the raster angle at 00 resulted in the most suitable combination identified in the response optimization analysis.

Designing an External Collar Torsional Damper Based on the Backlash Excitation Measurements and the Calculated Torsional Elastic Properties of the Engine Cold Test Driveline

The elastic properties of the cold test driveline are essential in predicting the torsional dynamic behavior of the system. The occurrence of torsional vibrations compels designers to apply several approaches to shift the critical speeds away from the machine operating range. This study reviews existing conventional methods for reducing the torsions deformation caused by the compliance backlash. A systematic approach is proposed for the backlash calculation through the torque signatures differentiation and for designing an external collar dampener for the suppression of backlash periodic impact.

Limited Dynamic Hip Screw for Treatment of Intertrochanteric Fractures: A Biomechanical Study.

BackgroundThe aim of this article is to introduce a novel technique of limited dynamic hip screw (LDHS) in the treatment of intertrochanteric fractures and to evaluate its biomechanical effects.Material/MethodsBased on the principle of providing both dynamic and static pressure to stabilize the fracture, we improved the dynamic hip screw (DHS) and designed the LDHS. Six fresh cadavers were collected and intertrochanteric fracture models were established, including Evan’s type I fracture (n=3) and type II (n=3). We used the left-to-right comparison in this study. LDHS technique was performed on the left femoral head of each cadaver (LDHS group: n=6), while DHS was performed on the right side (DHS group: n=6). After fixation by either LDHS or DHS, compressive strength, rigidity, shear stress and strain, torsional properties, and ultimate loads were measured and compared in both groups.ResultsUnder the 1200 N pressure, compressive strength, rigidity, shear stress and strain, and ultimate loads of LDHS were better than those of DHS in the 2 groups. All differences were statistically significant. Although LDHS enhanced the torsional properties, there was no significant difference.ConclusionsOur study demonstrates that the biomechanical effects of LDHS are superior than those of DHS, and there was no screw failure after implantation. Armed with those better properties, LDHS, as a new internal fixation device, may be a good alternative option in the treatment of intertrochanteric fractures.