Torsional Properties Research Articles

Irradiation-enhanced torsional buckling capacity of carbon nanotube bundles

Molecular dynamics simulations are used to understand the torsional buckling of pristine and irradiated carbon nanotube (CNT) bundles. Irradiation-induced inter-tube defects are shown to significantly increase the critical buckling torque and critical buckling angle, while slightly increasing the torsional stiffness. In contrast, intra-tube defects are found to degrade the torsional properties. Such competing interactions cause irradiation enhancement to occur in large bundles where significant inter-tube bonding can occur. However, the irradiation enhancement effect becomes weak for very large bundles in which enhanced inter-tube interactions already exist in unirradiated bundles. In pristine CNT bundles of all sizes under torsional loading, CNTs can slip via the weakly interacting van der Waals force, whereas in the irradiated bundles, the inter-tube defects prevent slipping. The study further shows that the formation of one-dimensional carbon chain defects contributes to enhanced friction under slipping.

Effect of Glass Fiber Tex on the Torsional Properties of FW-GFRP Shafts

Effect of Glass Fiber Tex on the Torsional Properties of FW-GFRP Shafts

Effect of microstructure and cycling frequency on the torsional fatigue properties of 17-4PH stainless steel

Torsional fatigue tests in the high and very high cycle regime were performed with martensitic stainless steel 17-4PH. Tests were conducted with a servo-hydraulic machine and an ultrasonic equipment at cyclic frequencies of 15–35 Hz and 19 kHz, respectively. Fatigue lifetimes were significantly longer for smooth specimens tested at 19 kHz. Fatigue limits were not affected by testing frequency. This behaviour was explained by the presence of δ ferrite grains, in which crack initiation at conventional frequency is accelerated, but their size is too small to significantly decrease the fatigue limit. In the presence of detrimental defects – i.e. small drilled holes that were introduced into test specimens –, no frequency effect could be observed. The geometry of non-propagating shear cracks emanating from δ ferrite grains and in the martensitic matrix was measured by stepwise polishing of a run-out specimen. Fracture-mechanics considerations suggest that the threshold condition for the propagation of Mode-I cracks determines the fatigue limit under torsional loading.

Combined Force-Torque Spectroscopy of Proteins by Means of Multiscale Molecular Simulation

Assessing the structural properties of large proteins is important to gain an understanding of their function in, e.g., biological systems or biomedical applications. We propose a method to examine the mechanical properties of proteins subject to applied forces by means of multiscale simulation. Both stretching and torsional forces are considered, and these may be applied independently of each other. As a proof of principle, we apply torsional forces to a coarse-grained continuum model of the antibody protein immunoglobulin G using fluctuating finite element analysis and use it to identify the area of strongest deformation. This region is essential to the torsional properties of the molecule as a whole because it represents the softest, most deformable domain. Zooming in, this part of the molecule is subjected to torques and stretching forces using molecular dynamics simulations on an atomistically resolved level to investigate its torsional properties. We calculate the torsional resistance as a function of the rotation of the domain while subjecting it to various stretching forces. From this, we assess how the measured twist-torque profiles develop with increasing stretching force and show that they exhibit torsion stiffening, in qualitative agreement with experimental findings. We argue that combining the twist-torque profiles for various stretching forces effectively results in a combined force-torque spectroscopy analysis, which may serve as a mechanical signature for a biological macromolecule.

Numeric Evaluation of Innovate Spring Machined Nickel-Titanium Rotary Instruments: A 3-dimensional Finite Element Study

IntroductionThe purpose of this study was to investigate if machined springs in nickel-titanium (NiTi) rotary instruments can improve their mechanical properties. The bending and torsion properties were assessed using finite element (FE) model analysis. MethodsA basic 3-dimensional file model without a spring was created with apical size #25, 25-mm full length, and 16-mm cutting flutes. Three other models were created with a spring machined into their shaft portion with different numbers of spring coils: standard (STspr), 10% more (INspr), and 10% less (DEspr). To compare the mechanical responses among the 4 FE models, file bending and torsion were simulated using FE analysis. ResultsSpring machined NiTi rotary instruments showed higher torsional resistance and less bending stiffness than the same instrument without. The spring machined models required more torque to bend or rotate the DEspr model than was required for the STspr and INspr models; however, the STSpr and INSpr models were similar. ConclusionsWithin the limitations of this study, the FE analysis indicated that machining a spring into the shaft of NiTi rotary instruments improved torsional resistance and bending flexibility. Therefore, spring machining has the potential to increase the durability of the NiTi rotary instruments.

A Biomechanical Evaluation of the Tibia after Retrograde Intramedullary Reaming

Category:Hindfoot; Ankle; Ankle Arthritis; Basic Sciences/Biologics; TraumaIntroduction/Purpose:Autologous bone graft is an important tool in the foot and ankle surgeon’s arsenal, and remains the gold standard despite the release of new biologics. The Reamer-Irrigator-Aspirator (RIA) system has become an option for local intramedullary bone graft harvest. Evidence supports the quality of graft and safety of RIA in the femur, and some series have demonstrated its value in tibial reaming for hindfoot fusion. However, there has been no analysis of the mechanical effects of the system on the tibia. The purpose of this study is to investigate the effect of retrograde intramedullary reaming on the mechanical properties of cadaveric tibias, with the hypothesis that this will produce no significant difference in torsional strength between groups.Methods:Intact, fresh frozen tibias were obtained for testing, totaling 11 matched pairs. One tibia was chosen for reaming from each pair with pre-test randomization. The selected tibia was reamed in a retrograde fashion over a guidewire to 12mm, which is the smallest diameter RIA device available. Each tibia was potted and mounted in a custom jig for testing on a servohydraulic test frame. Each specimen was first tested non-destructively for compressive properties using standardized loading rates. Each specimen was then loaded in torsion under constant angular velocity of 9˚/second until failure or the limit of the load cell was reached. Mechanical properties were determined from the load-displacement curve and compared between reamed and unreamed matched pairs using paired samples statistics, with statistical significance set at p=0.05.Results:Specimens were of mean age 56 (range 39-67) years, with 55% being female. The mean compressive stiffness of reamed (560.4 +- 111.7 N/mm) and unreamed (628.2 +- 117.2 N/mm) tibias were not statistically different (p = 0.167). Nine of the reamed specimens and 10 of the unreamed specimens fractured during torsional testing. Torsional testing for stiffness (178.4 Nm/rad +- 59.4 vs 168.1 +- 40.8, p=0.370), rigidity (50.4 Nm2/rad +- 19.1 vs 47.0 +- 13.7, p=0.331), and ultimate load capacity (71.2 Nm +- 24.3 vs 71.9 +- 20.5, p=0.880) showed minimal differences between reamed and unreamed specimens, respectively.Conclusion:Mechanical testing identified no statistically significant differences in torsional or compressive properties of our cadaveric tibias after intramedullary reaming. There was a trend towards decreased compressive stiffness, but this is not a common mechanism of fracture. Our findings suggest that the use of the smallest size RIA system in the tibia does not drastically alter the mechanical properties or require prophylactic fixation. The RIA can be used safely as a method of bone graft harvest or intramedullary debridement in the tibia, as long as appropriate technique is used to avoid eccentric reaming or excessive blood loss.

Molecular Dynamics Simulation of Chiral Carbon Nanothread Bundles for Nanofiber Applications

Carbon nanofibers as constructed from various one-dimensional carbon nanostructure, such as sp3 diamond nanowire, sp2 carbon nanotubes, and carbyne, have received enormous interest from both scientific and engineering communities. The newly synthesized nanostructure carbon nanothreads (C_NTH) show superior properties and make them ideal building blocks for high-performance carbon nanofibers. This work systematically investigates the torsional properties of C_NTH bundles through high-throughput large-scale molecular dynamics simulations. Our results show that the torsional behavior of C_NTH bundles depends strongly on the loading direction. By adjusting the enantiomer ratios, we can effectively tune the mechanical properties of the bundle structure, including the strain energy density, elastic limit, and torsional rigidity. Benefiting from their rich structural varieties, this work suggests that carbon nanothreads are promising candidates for the next-generation high-performance carbon nanofiber.

Engineered Microstructure Derived Hierarchical Deformation of Flexible Pressure Sensor Induces a Supersensitive Piezoresistive Property in Broad Pressure Range.

Fabricating flexible pressure sensors with high sensitivity in a broad pressure range is still a challenge. Herein, a flexible pressure sensor with engineered microstructures on polydimethylsiloxane (PDMS) film is designed. The high performance of the sensor derives from its unique pyramid‐wall‐grid microstructure (PWGM). A square array of dome‐topped pyramids and crossed strengthening walls on the film forms a multiheight hierarchical microstructure. Two pieces of PWGM flexible PDMS film, stacked face‐to‐face, form a piezoresistive sensor endowed with ultrahigh sensitivity across a very broad pressure range. The sensitivity of the device is as high as 383 665.9 and 269 662.9 kPa−1 in the pressure ranges 0–1.6 and 1.6–6 kPa, respectively. In the higher pressure range of 6.1–11 kPa, the sensitivity is 48 689.1 kPa−1, and even in the very high pressure range of 11–56 kPa, it stays at 1266.8 kPa−1. The pressure sensor possesses excellent bending and torsional strain detection properties, is mechanically durable, and has potential applications in wearable biosensing for healthcare. In addition, 2 × 2 and 4 × 4 sensor arrays are prepared and characterized, suggesting the possibility of manufacturing a flexible tactile sensor.

Effects of high-pressure torsion treatment on the microstructural aspects and electrochemical behaviour of austenitic NiTi shape memory alloy

In this study, microstructural aspects and electrochemical properties of high-pressure torsion (HPT)-treated austenitic NiTi alloy were investigated. Microstructural characterizations were performed by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) analysis. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were used to evaluate the electrochemical properties in simulated body fluid (SBF) solution. It was found that HPT process increased the martensitic phase from 8.22 to 71.31 wt%. HRTEM results revealed a combination of amorphous/nanocrystalline austenitic and martensitic phases of NiTi after HPT. The lower value of corrosion current density of HPT-treated NiTi (2.5 × 10−6A/cm2) was observed compared with the untreated sample (7.6 × 10−6 A/cm2). EIS tests confirmed higher corrosion resistance of the HPT-treated sample. EIS analysis showed a decrease and increase in the impedance value of the specimens at different immersion times indicating the formation and degradation of oxide films over time on the specimens’ surface. However, the impedance value of the HPT-treated sample was more than that of the untreated sample. Localized corrosion is observed at the surface of the untreated specimen due to the absence of a dense oxide protective film but no evidence of localized and pitting corrosion on the surface of HPT-treated sample was observed.

Potential energy function for a photo-switchable lipid molecule.

Photo-switchable lipids are synthetic lipid molecules used in photo-pharmacology to alter membrane lateral pressure and thus control opening and closing of mechanosensitive ion channels. The molecular picture of how photo-switchable lipids interact with membranes or ion channels is poorly understood. To facilitate all-atom simulations that could provide a molecular picture of membranes with photo-switchable lipids, we derived force field parameters for atomistic computations of the azobenzene-based fatty acid FAAzo-4. We implemented a Phyton-based algorithm to make the optimization of atomic partial charges more efficient. Overall, the parameters we derived give good description of the equilibrium structure, torsional properties, and non-bonded interactions for the photo-switchable lipid in its trans and cis intermediate states, and crystal lattice parameters for trans-FAAzo-4. These parameters can be extended to all-atom descriptions of various photo-switchable lipids that have an azobenzene moiety.

Highly reliable electromagnetic MOEMS scanning grating mirror based on folded torsion beam with fillet corners

To overcome the problems of poor structural reliability, high driving voltage and small scanning angle, a novel electromagnetic MOEMS scanning grating mirror (SGM) with folded torsion beam is reported in this work. Compared with the conventional straight torsion beam, the folded torsion beam has better elastic torsion property and can effectively improve the structural reliability of the MOEMS SGM. Furthermore, the fillet structure is added to the folded torsion beam to prevent stress concentration. The stress analysis and impact resistance of the proposed MOEMS SGM are simulated by FEM (ANSYS 18.2), and the simulation results are compared with that of the MOEMS SGM without fillet structure. The stress simulation is carried out under different fillet radius of 40–70 [Formula: see text]m, the maximum stress can be reduced to 85[Formula: see text] and the stress is redistributed uniformly. Meanwhile, in the impact resistance simulation, the impact displacement can be reduced by 10.1[Formula: see text]. A prototype is fabricated and tested, it has a large mirror area of 6 mm ×7 mm. The MOEMS SGM can reach the maximum scanning half angle of [Formula: see text] at 7.63 V under resonance (@602.1 Hz), which means that the full mechanical scanning angle of the MOEMS SGM can reach [Formula: see text].

Journal Vol – 15 No -7, July 2020 Journal > Journal > Journal Vol – 15 No -7, July 2020 > Page 6 PERFORMANCE AND EMISSION CHARACTERISTICS OF GASOLINE-ETHANOL BLENDS ON PFI-SI ENGINE Authors: D.Vinay Kumar ,G.Samhita Priyadarsini,V.Jagadeesh Babu,Y.Sai Varun Teja, DOI NO: https://doi.org/10.26782/jmcms.2020.07.00051 admin July 26, 2020 Abstract: Alcohol based fuels can be produced from renewable energy sources and

Journal Vol – 15 No -7, July 2020 Journal > Journal > Journal Vol – 15 No -7, July 2020 > Page 6 PERFORMANCE AND EMISSION CHARACTERISTICS OF GASOLINE-ETHANOL BLENDS ON PFI-SI ENGINE Authors: D.Vinay Kumar ,G.Samhita Priyadarsini,V.Jagadeesh Babu,Y.Sai Varun Teja, DOI NO: https://doi.org/10.26782/jmcms.2020.07.00051 admin July 26, 2020 Abstract: Alcohol based fuels can be produced from renewable energy sources and

Comparison of torsional properties between a Fixateur Externe du Service de Santé des Armées and an acrylic tie-in external skeletal fixator in a red-tailed hawk (Buteo jamaicensis) synthetic tibiotarsal bone model.

To compare the torsional mechanical properties of 2 external skeletal fixators (ESFs) placed with 2 intramedullary pin (IP) and transfixation pin (TP) size combinations in a model of raptor tibiotarsal bone fracture. 24 ESF-synthetic tibiotarsal bone model (polyoxymethylene) constructs. Synthetic bone models were fabricated with an 8-mm (simulated fracture) gap. Four types of ESF-synthetic bone model constructs (6/group) were tested: a FESSA with a 1.6-mm IP and 1.6-mm TPs, a FESSA with a 2.0-mm IP and 1.1-mm TPs, an acrylic connecting bar with a 1.6-mm IP and 1.6-mm TPs, and an acrylic connecting bar with a 2.0-mm IP and 1.1-mm TPs. Models were rotated in torsion (5°/s) to failure or the machine angle limit (80°). Mechanical variables at yield and at failure were determined from load deformation curves. Effects of overall construct type, connecting bar type, and IP and TP size combination on mechanical properties were assessed with mixed-model ANOVAs. Both FESSA constructs had significantly greater median stiffness and median torque at yield than both acrylic bar constructs; FESSA constructs with a 1.6-mm IP and 1.6-mm TPs had greatest stiffness of all tested constructs and lowest gap strain at yield. No FESSA constructs failed during testing; 7 of 12 acrylic bar constructs failed by fracture of the connecting bar at the interface with a TP. Although acrylic bar ESFs have been successfully used in avian patients, the FESSA constructs in this study were mechanically superior to acrylic bar constructs, with greatest benefit resulting from use with the larger TP configuration.

Cyclic shear response of additively manufactured Inconel 718

PurposeAdditive manufacturing (AM) studies on Inconel 718 (IN718) have focused on exploring its tensile and fatigue response. As IN718 is used in the propulsion and energy sector, the impact of shearing is also critical to ensuring the durability of these components. As such, this study aims to explore the relation between build orientation on the shear cyclic response of direct metal laser sintered (DMLS) IN718.Design/methodology/approachIN718 torsion specimens were manufactured along six build orientations: (100)-X, (010)-Y, (001)-Z, (110)-XY45, (101)-XZ45 and (011)-YZ45, using the DMLS process. Torsional fatigue testing was performed on as-built specimens, from which fracture behavior, surface roughness, softening/hardening response and monotonic/cyclic shear torsional properties were assessed.FindingsDMLS IN718 was found to exhibit transversely isotropic behavior. In terms of shear stress range and shear modulus, Z > (X, XY45, Y) > (XZ45, YZ45). Specimens cyclically hardened to stabilization and softened to fracture. In terms of torsional fatigue fracture response, the Z, XZ45 and YZ45 specimens exhibited crack initiation and propagation from internal defects, whereas cracks were found to initiate at the surface and propagate between and through build layers for the X, Y and XY45 specimens.Originality/valueThis study reports the torsional cyclic response and shear moduli exhibited by as-built DMLS IN718 manufactured along varying build orientations. The findings are applicable for researchers because of the wide use of IN718 in the gas turbine industry, and the current trend to replace conventional manufacturing with AM.

Are Magnesium Screws Proper for Mandibular Condyle Head Osteosynthesis?

Recently, magnesium alloys have gained a significant amount of recognition as potential biomaterials for degradable implants for craniofacial bone screws. Purpose: The aim of this work was to compare screws made specifically for mandibular head osteosynthesis from different materials. Materials and Methods: Screws measuring 14 mm made by one manufacturer specifically for mandibular head osteosynthesis out of the following materials were selected: magnesium (MgYREZr), titanium (Ti6Al7Nb), and polymer (PLGA). The axial pull-out strength and torsional properties were investigated. Results: Each type of screw presented different pull-out forces (Kruskal–Wallis test, p < 0.001). The magnesium screw had the highest pull-out force of 399 N (cracked without the screw out being pulled out), followed by the titanium screw, with a force of 340 N, and the PLGA screw, with a force of 138 N (always cracked at the base of the screw head without the screw being pulled out). ANOVA was performed for the maximal torques before damage to the screw (torsional properties), revealing that the maximal torque of the magnesium screw was 16 N·cm, while that of the titanium screw was 19 N·cm. The magnesium screw was significantly weaker than the titanium screw (p < 0.05). The measured torque and pull-out force were not related to each other (p > 0.05). Conclusion: Among the screws compared, the metal biodegradable magnesium screw seems to be the most suitable material for multiscrew mandibular head osteosynthesis, considering the condition of the fragile screwdriver socket.

Wear and Adhesion Properties of High-Pressure Torsion Processed Carbon Steel

High-pressure torsion (HPT) is one of the most promising methods employed to fabricate ultra-fine grained (UFG) materials for use in industrial applications. The aim of this work is to investigate the tribological behavior of UFG carbon steels produced by an HPT. In cases where the counter ball material was tungsten and cobalt cemented carbide (WC-Co), the wear rate (0.2~2.0x10-7 mm2/N) decreased with increasing the Vickers hardness (Hv200~650) for both HPT processed and quenched-tempered (QT) steels. On the other hand, in cases where the counter ball material was high carbon-chromium bearing steel (SUJ2), the wear rate of HPT (1.0~2.5x10-6 mm2/N) increased with increasing the hardness, which was an abnormal wear behavior. There was a tendency that the wear rate increased with an increase of the coefficient of friction, and that the coefficient of friction of HPT was 13-18 % higher than that of QT. Moreover, the adhesion force of HPT was 6-7 times higher than that of QT. Thus we have concluded that the high wear rate of HPT steels in the case of the SUJ2 ball wear tests were due to the high coefficient of friction as a result of the high adhesion force, which was caused by the high density of the grain boundaries in the UFG materials.

Potential Energy Function for Fentanyl-Based Opioid Pain Killers.

Opioids are molecules whose binding to specialized G-Protein Coupled Receptors (GPCRs) triggers a signaling cascade that leads to the downregulation of pain pathways. Binding of an opioid to the membrane-embedded GPCR occurs when the opioid molecule is protonated, which provides a potential strategy to design nontoxic opioids that are protonated and bind to the GPCR only at the low pH of injured or inflamed tissue. Excellent model systems to study protonation-dependent binding of opioids to GPCRs are fentanyl, which is protonated and binds to the GPCR at both physiological and low pH, and the fluorinated fentanyl derivative NFEPP, which is protonated and binds to the GPCR only at low pH. The molecular mechanisms of fentanyl and NFEPP binding to the GPCR are largely unknown. To enable atomistic studies of opioid binding to GPCRs, we have carried out extensive quantum mechanical and classical mechanical computations to derive a potential energy function for fentanyl and NFEPP and present force field parameters for both opioid molecules. We find that fluorination alters the electronic ground state properties of fentanyl. As a consequence, fentanyl and NFEPP have distinct torsional and electrostatic properties likely to impact how they bind to receptors.

Study of Torsional, Flexural and Other Properties in Reinforced Concrete Structures Wrapped With FRP

Study of Torsional, Flexural and Other Properties in Reinforced Concrete Structures Wrapped With FRP

Torsional shear strength and elastic properties of adhesively bonded glass-to-steel components

Nowadays glass is widely used in building applications and coupled to steel through adhesive joining. Reliable mechanical characterization of these joints is necessary to design and predict the final structure performance.In this framework, the aim of this paper is to measure the pure shear strength and elastic modulus for design and modelling of adhesive joined glass-to-steel structures.Torsional shear strength and elastic properties of an adhesively bonded glass-to-steel component were measured on several joined steel-to-steel and steel-to-glass samples.An epoxy resin-based adhesive was used as joining material for AISI304 steel and soda-lime glass.The same steel and adhesive were used to obtain steel-to-steel joined sample bars to be tested in asymmetrical four-point bending, for comparison purposes.The indentation elastic modulus of the adhesive, both inside the joined region and as a bulk, was measured by nano-indentation and impulse excitation technique.Finally, the effect of etching on the glass was studied and correlated to the glass-steel joint strength.This study shows that torsion test can be used to provide reliable shear strength values for design and modelling glass-to-steel adhesive joined components.

Effects of microstructure on the torsional properties of biodegradable WE43 Mg alloy

Torsional properties are important performance parameters for bone screw applications, but they are seldom studied, especially for newly developed biodegradable Mg alloys. In this study, WE43 Mg alloy with different microstructures was achieved by equal channel angular pressing (ECAP) and heat treatment, and their torsional properties were studied. In addition, tensile properties were also tested as a comparison. The results indicated that grain refinement led to higher torsional strength and ductility, while the second phases improved the torsional strength but reduced the ductility. The texture was strengthened after ECAP, as a result the tensile strength increased, but the torsional strength did not increase and even decreased, especially for 2-pass ECAP sample with a typical basal fiber texture. The basal plane orientation deviation from the extrusion direction after 4-pass ECAP resulted in higher torsional strength and lower torsional ductility, but lower tensile strength and higher tensile ductility were obtained. This implied that a strong fiber texture would reduce the torsional strength but improve the torsional ductility, which was different from its effect on tensile properties.