Higher Torsional Strength Research Articles

Curvature limits for composite steel box girder bridges

Composite concrete deck-over steel box girder bridges are used in curved alignments as an economical solution because of their high flexural and torsional strength. Curvature effects on bending, shear, and deflection may be ignored for bridges with light curvature. Canadian Highway Bridge Design Code (CHBDC), AASHTO Guide Specifications for Horizontally Curved Bridges, and AASHTO-LRFD Bridge Design Specifications specify limitations to treat a horizontally curved bridge as a straight one in structural design for only girder bending moment. Also, CHBDC curvature limitation does not differentiate between open- and closed bridge cross-sections. The curvature limitation of the ASSHTO Guide does not consider the effect of bridge width, leading to an inaccurate estimate of the structural response. To investigate the accuracy of these curvature limitations, a series of horizontally curved composite steel box-girder bridges were analyzed using finite-element modeling. The key parameters considered in this study were the degree of curvature and bridge span, width, and continuity. Longitudinal bending stresses, support reactions, deflections, and frequencies were determined and compared with those obtained for straight bridges of identical configurations. Results showed that code curvature limits were unsafe and needed to be updated. Empirical expressions were developed to determine curvature limits more accurately and reliably.

Effect of Mean Torsional Stress on Very High Cycle Torsional Fatigue Strength of High Strength Steel

Effect of Mean Torsional Stress on Very High Cycle Torsional Fatigue Strength of High Strength Steel

Evaluation of Cyclic Fatigue and Torsional Strength of Three Different Thermally Treated Reciprocating Nickel-Titanium Instruments

Objectives. This article's objective was to assess the reciprocating single-file systems Reciproc Blue 25.08 and Pro design R 25.06's cyclic and torsion fatigue resistance. The systems Reciproc Blue R25 (RB #25.08 taper), Prodesign R (PDR #25.06 taper), and WaveOne Gold (WOG #25.07 taper) (n = 20) were utilized to make sixty reciprocating instruments. The period to breakdown in an artificial stainless-steel canal with a 60° angle of curvature and a 5-mm radius was measured during cyclic fatigue resistance testing (n = 10). The torque and angle of rotation at failure of new instruments (n = 10) were assessed during the torsional test (ISO 3630-1) in the area 3 mm from the tip. Scanning electron microscopy was also used to view each fragment's shattered surface (SEM). In addition, a supplementary examination was performed to measure the cross- sectional area of each instrument 3 and 5 mm from the tip. The data were analyzed using one-way ANOVA and Tukey’s test, and the level of significance was set at 5%. Cycle Fatigue Resistance scores for PDR 25.06 were much higher (P 0.05). Both WOG 25.07 and RB 25.08 showed less resistance to fatigue (P 0.05). Based on the torsional analysis, PDR 25.06 had weaker torsional strength (P 0.05). No changes were found with RB 25.08 and WOG 25.07 (P > 0.05). PDR 25.06 showed higher angular rotation values than RB 25.08 and WOG 25.07. (P 0.05). Greater angular rotation was seen in both WOG 25.07 and RB 25.08. (P 0.05). The cross-sectional area analysis revealed that PDR 25.06 had the smallest cross-sectional areas at 3 and 5 mm from the tip (P 0.05). In comparison to RB 25.08 and WOG 25.07, PDR 25.06 had the highest cyclic fatigue resistance and angular rotation until fracture. Additionally, torsional strength was higher in RB 25.08 and WOG 25.07 than PDR 25.06. Clinical applicability in endodontic practise, reciprocating instruments that have undergone thermal treatment are used to prepare the root canals of canals that are curved and constrained; as a result, these instruments must exhibit high flexibility and suitable torsional strength to reduce the risk of instrument deformation.

Effect of functionalized graphene addition on mechanical and thermal properties of high density polyethylene

Abstract High density polyethylene (HDPE)/graphene nanocomposites were successfully synthesized by compounding of HDPE, as polymer matrix, with hexamethylenediamine functionalized graphene. The resulting nanocomposite was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), scanning electron microscope (SEM) and thermal gravimetric analysis (TGA) techniques. SEM characterization confirmed the good dispersion (homogeneous and uniform) of graphene in the polyethylene matrix. The TGA technique revealed a slight improvement in thermal resistance. Functionalized graphene improved a better thermal stability of HDPE (up to 6 °C) than non-functionalized graphene (up to 2 °C). Mechanical tensile and torsion tests showed that HDPE/functionalized graphene nanocomposites exhibit high tensile strength and low torsional strength compared to HDPE/non-functionalized graphene nanocomposites. Compared to pure HDPE, the Young’s modulus increased by 80% and 30%, whereas, the torsion modulus increased by about 34% and 44% for the HDPE/functionalized and HDPE/non-functionalized graphene, respectively. Regardless of this increase, it can be seen that the torsion modulus of HDPE/non-functionalized graphene is much higher than that of HDPE/functionalized graphene.

Process Parameter Investigation and Torsional Strength Analysis of the Additively Manufactured 3D Structures Made of 20MnCr5 Steel

An ongoing growth of the available materials dedicated to additive manufacturing (AM) significantly extends the possibilities of their usage in many applications. A very good example is 20MnCr5 steel which is very popular in conventional manufacturing technologies and shows good processability in AM processes. This research takes into account the process parameter selection and torsional strength analysis of AM cellular structures. The conducted research revealed a significant tendency for between-layer cracking which is strictly dependent on the layered structure of the material. Additionally, the highest torsional strength was registered for specimens with a honeycomb structure. To determine the best-obtained properties, in the case of the samples with cellular structures, a torque-to-mass coefficient was introduced. It indicated the best properties of honeycomb structures, which have about 10% smaller torque-to-mass coefficient values than monolithic structures (PM samples).

Torsional cracks development in carbon-fiber 3-D braided composite tubes

Torsional cracks development is key to design high torsional strength tubes, especially for heterogeneous materials such as fiber reinforced composite tubes. Here we report torsional cracks initiation and development in carbon-fiber 3-D braided composite tubes. 3D digital image correlation (3D-DIC) and micro computed-tomography (micro-CT) techniques were used to observe inner crack distributions. The correlation between cracks and braided structure is revealed. We found that the torsional damage propagates along the helix of braided bundles in torsion direction and inhibits in vertical direction within repeated braid units. The bundles are subjected to axial tension in the torsion direction and axial compression in vertical direction. This leads to slippage and cross-section deformation in braided yarns at intersection points. Strain distribution has the same periodic form with the braided structure, i.e., low-strain locates on fiber bundles and high-strain concentrates on the edges and interlacing gap of bundles. Interface cracks are main damage modes and induces final torsional failure both after resin and yarn damages.

Effect of Mean Torsional Stress on Very High Cycle Torsional Fatigue Strength of High Strength Steel

Effect of Mean Torsional Stress on Very High Cycle Torsional Fatigue Strength of High Strength Steel

Biomechanical evaluation of compression buttress screw and medial plate fixation for the treatment of vertical femoral neck fractures

ObjectiveTo compare the biomechanical properties of compression buttress screw (CBS) fixation with three plate fixation methods for the treatment of vertical femoral neck fractures (FNFs). MethodsA total of forty synthetic femoral models with simulated Pauwels type III fractures (angle of 70°) were equally assigned to one of four fixation groups: CBS fixation, anteromedial plate fixation (AMP), medial buttress plate fixation (MBP) and medial buttress plate fixation without proximal screw (MBPw). Within each group, half of the specimens were randomly assigned to two loading settings, an axial compression loading test and a hip-flexion torsion test. ResultsThere were no significant differences in axial load to failure, axial stiffness, torsional strength, or torsional stiffness when comparing CBS with MBP (p>0.05). In the axial compression loading test, both CBS and MBP showed higher load to failure and axial stiffness than MBPw (p<0.05). In torsional testing, AMP exhibited superior torsional strength and torsional stiffness than both MBPw and MBP (all p<0.05) and a higher torsional strength than CBS fixation (p<0.05). There were no significant differences in torsional stiffness between the CBS and AMP fixation groups (p>0.05). ConclusionThe biomechanical parameters of CBS fixation are comparable to that of AMP and MBP, and demonstrate superior axial stiffness than MBPw fixation. Although the CBS method for surgical fixation of vertical FNF holds promise as a less invasive surgical technique than plate fixation with similar biomechanical assessments, further clinical evaluation is warranted.

Analysis and optimisation of the cutting parameters based on machinability factors in turning AISI 4140 steel

ABSTRACT AISI 4140 alloy steel has high abrasion resistance, toughness, torsional, and fatigue strength. Different types of this alloy with different hardness are used to manufacture gears, crankshafts, collars, jigs, and milling spindles. In this study, turning tests were carried out on AISI 4140 steel using coated carbide inserts considering Taguchi L9 orthogonal array at three different cutting speeds, feed rates, and cutting depths. The output parameters were selected as cutting forces, surface roughness, current and sound intensity. According to the ANOVA results, feed rate was the most effective parameter on the cutting force and surface roughness. As the feed rate increases, the cutting force and surface roughness value enhance. The feed rate was also the most important factor affecting the current with 81.61% contribution, followed by cutting depth with 12.67% contribution. The cutting depth with 66.95% contribution has the highest impact on the sound intensity. It was followed by a feed rate with 26.07% contribution. According to the optimisation results, the experimental and the estimated values ⁣⁣were significantly close to each other.

Torsional behavior of non-crimp orthogonal woven composite using experimental and numerical methods

Nowadays, using three dimensional fabric as a reinforcement part in the composite has been increased. Non-crimp three dimensional orthogonal woven fabric is a subgroup of 3D woven fabrics that in this study was used to fabricate composite preforms. The fabrics were produced by glass yarn in two different fiber volume fractions. All fabric preforms were utilized to produce composites with polyester and epoxy resins. To compare the torsional behavior of the composites, a torsion test was applied to all samples and torque-revolution curves from the experimental results were compared together. Results showed that composites that were fabricated by epoxy resin have more torsional strength in comparison with composites in that their matrix is polyester resin. Moreover, preforms with high fiber volume fractions showed high torsional strength in each type of matrix. The torsion strength of high volume fraction for polyester matrix was 47.34 KPa, however for the sample with epoxy matrix the torsion strength was determined 81.26 KPa. Furthermore, a multiscale finite element model was applied to calculate elastic constants and predict the torsional behavior of the composites. The numerical results were compared with experimental results that a good agreement between numerical and experimental results was observed. Therefore, the proposed model can predict the torsional behavior of the composite with different fiber volume fractions.

Stents With Torsional Strength for Superficial Femoral Artery Disease: The Prospective Q3-Registry

Purpose: This postmarketing surveillance study aimed to assess effectiveness and safety of a peripheral self-expanding stent with high torsional strength (POLARIS stent) for the treatment of de novo superficial femoral artery (SFA) lesions in the routine clinical practice. Materials and Methods: Consecutive patients with symptomatic de novo SFA occlusive disease who underwent POLARIS stent implantation were enrolled into the prospective, multicenter, observational postmarket surveillance study. Primary outcome measure was freedom from clinically driven target lesion revascularization (cdTLR) at 12 months. Main secondary outcomes were procedural success, primary clinical improvement, and freedom from major adverse cardiovascular and limb events (MACLE) throughout 24 months. Results: A total of 199 participants (70±11 years, 70.4% men) were included in the study at 9 German sites from December 2014 to August 2018. Half of them (52.6%) were current smokers, 37.6% had diabetes, and 25.0% were obese. Most participants suffered from intermittent claudication (88.4%). Mean lesion length was 98±83 mm, 43.5% of lesions were occluded, and 27.3% were severely calcified. Freedom from 12 months cdTLR was 94.4% (95% confidence interval [CI], 90.6–98.2). At 24 months, freedom from cdTLR was 88.7% (95% CI, 83.0–94.4). Procedural success was achieved in 96.2% of participants. Primary clinical improvement occurred in 87.5% and 85.4% of participants at 12 and 24 months, respectively. Freedom from MACLE was 94.8% (95% CI, 91.4–98.1) and 93.8% (95% CI, 89.9–97.6) at 12 and 24 months, respectively. Conclusions: Treatment of SFA occlusive disease in a real-world setting using the POLARIS stent with high bidirectional torsional strength is efficacious and does not raise any safety concern in the medium term. The study is registered with ClinicalTrials.gov (Identifier: NCT02307292).

A Comparative Investigation on Normal and High Strength Concrete Beams under Torsion

In this study, an experimental investigation was done to study the behaviour of Normal Strength Concrete (NSC) and High Strength Concrete (HSC) Plain beams under torsion with the concrete mix of M40 and M100. No mineral admixtures are used to obtain the required strength of concrete. Eight NSC beams and eight HSC beams whose width was varying with 75 mm, 100 mm, and 150 mm; depth varying as 75 mm, 100 mm, 150 mm and 200 mm; and span of the beams varying 600 mm, 800 mm and 1200 mm were casted and cured to stud the effect of torsion. The principle aim of this study was to understand the torsional behaviour of the NSC and HSC beams for rotation, cracking, size effect and torsional strength. A standard torsional loading method was used for conducting the testing of beams. The results obtained were compared with different theories and code equations. It was observed that the torsional strength of the beam increases with the increase in strength of concrete. HSC beams have higher torsional strength than the NSC beams which has the same amount of reinforcement.

Design and analysis of concrete-filled tubular flange girders under combined loading

This paper is concerned with the behaviour of concrete-filled tubular flange girders (CFTFGs) under the combination of bending and tensile axial force. CFTFG is a relatively new structural solution comprising a steel beam in which the compression flange plate is replaced with a concrete-filled hollow section to create an efficient and effective load-carrying solution. These members have very high torsional stiffness and lateral torsional buckling strength in comparison with conventional steel I-girders of similar depth, width and steel weight and are there-fore capable of carrying very heavy loads over long spans. Current design codes do not explicitly include guidance for the design of these members, which are asymmetric in nature under the combined effects of tension and bending. The current paper presents a numerical study into the behaviour of CFTFGs under the combined effects of positive bending and axial tension. The study includes different loading combinations and the associated failure modes are identified and discussed. To facilitate this study, a finite element (FE) model is developed using the ABAQUS software which is capable of capturing both the geometric and material nonlinearities of the behaviour. Based on the results of finite element analysis, the moment–axial force interaction relationship is presented and a simplified equation is proposed for the design of CFTFGs under combined bending and tensile axial force.

Carbon nanotube-reduced graphene oxide fiber with high torsional strength from rheological hierarchy control

High torsional strength fibers are of practical interest for applications such as artificial muscles, electric generators, and actuators. Herein, we maximize torsional strength by understanding, measuring, and overcoming rheological thresholds of nanocarbon (nanotube/graphene oxide) dopes. The formed fibers show enhanced structure across multiple length scales, modified hierarchy, and improved mechanical properties. In particular, the torsional properties were examined, with high shear strength (914 MPa) attributed to nanotubes but magnified by their structure, intercalating graphene sheets. This design approach has the potential to realize the hierarchical dimensional hybrids, and may also be useful to build the effective network structure of heterogeneous materials.

Bending, buckling and torsional resistance of rotary and reciprocating glide path instruments.

To evaluate the bending, buckling and torsional resistance of ProGlider (PG) (Dentsply Sirona, Ballaigues, Switzerland), R-Pilot (RP) (VDW, Munich, Germany) and WaveOne Gold Glider (WOGG) (Dentsply Sirona). Ninety instruments were used: 30 PG (size 0.16, .02v taper), 30 RP (size 0.125, .04 taper) and 30 WOGG (size 0.15, .02v taper). The bending resistance test was performed on 10 randomly selected instruments of each system according to ISO 3630-1 specifications. For the buckling resistance test, a loading was applied in the axial direction of each instrument using a universal test machine, with a 20N cell and 15mmmin-1 speed, in the axial direction. When a lateral elastic displacement of 1mm occurred, the force was registered. The torsional resistance test was performed according to ISO 3630-1 specifications. Statistical analysis was performed using one-way anova and post hoc Student-Newman-Keuls test (P<0.05). WOGG had the lowest bending resistance, whilst RP had the highest bending resistance (P<0.05). RP also had the highest buckling resistance, and WOGG had the lowest (P<0.05). PG had intermediate results regarding bending and buckling resistance, with significant differences to RP and WOGG (P<0.05). RP had the highest torsional strength and the lowest angular deflection when compared to PG and WOGG (P<0.05). No differences in the torsional strength and angular deflection were observed between WOGG and PG (P>0.05). The glide path instruments had different behaviours in term of bending, buckling and torsional resistance.

Effects of a novel biodegredable implant system on a rat tibia fracture model.

This study aimed to determine the effects of a novel biodegradable implant releasing platelet-derived growth factor (PDGF) at the fracture site on fracture healing in a rat tibia fracture model. In this study, 35 male Sprague-Dawley rats weighing between 300 and 350 g were used. The rats were divided into four groups: Group A (control group without any treatment, n=10), Group B (spacer without PDGF Group, n=10), Group C (spacer with PDGF group, n=10), and Group D (healthy rat Group, n=5). Standardized fractures were created in the right tibias of rats, and then biodegradable implants made of poly-β-hydroxybutyrate-co-3-hydroxy valerate were implanted at the fracture sites in Groups B and C. In Group C, implants were loaded with 600 ng of PDGF. Animals were sacrificed 30 days after the operation, and fracture healing in each group was assessed radiologically based on the Goldberg score. Furthermore, the anteroposterior (AP) and mediolateral (ML) callus diameters were measured macroscopically, and fracture sites were mechanically tested. In the radiological assessment, Group C showed higher fracture healing rate than Groups A and B (p=0.001), whereas no significant difference was found between group C and Group D (p>0.05). In the macroscopic assessment, while Group C exhibited the thickest AP callus diameter (p=0.02), no significant differences in ML callus diameters existed among the groups (p>0.05). Mechanical testing revealed that Group C had higher torsional strength (p=0.001) and stiffness than Groups A and B (p=0.001) while there was no significant difference between Groups C and D (p>0.05). Biodegradable implant releasing PDGF may have positive effects on fracture healing.

A Compliant Robotic Instrument With Coupled Tendon Driven Articulated Wrist Control for Organ Retraction

Organ retraction is a common and important task in minimally invasive surgery. It is a surgical technique to push aside or manipulate tissues/organs to improve the access and visualization of the surgical sites. Typical manual retractors are rigid and without any articulation. Physicians often struggle with minimizing the force applying onto the tissue while positioning the retractor to maintain optimal exposure. In this letter, we propose a novel compliant robotic organ retractor with coupled tendon driven articulated wrist control to address the aforementioned clinical risks. The compliant retractor exploits the buckling principle of a continuum bending beam mechanism, allowing it to interact with organ safely and smoothly. We also present a new tendon-driven, high torsional strength articulated joint and corresponding kinematics model to address the lack of dexterity issue. For the instrument control, a general algorithm framework is proposed to design the controller gain systematically, while eliminating the “disturbance” leaking caused by the coupled multitendon driven mechanism. Initial prototypes were built and integrated with the state-of-the-art surgical robotic platform, da Vinci Research Kit for basic functional evaluation. Preliminary simulation and experimental results demonstrate the capability of the proposed device for organ retraction. It is our hope that this novel instrument will become a new benchmark for organ retraction in terms of safety, precision, and dexterity.

Design, Fabrication and Testing of Carbon Fiber Reinforced Epoxy Drive Shaft for All Terrain Vehicle using Filament Winding

Filament winding is a composite material fabrication technique that is used to manufacture concentric hollow components. In this study Carbon/Epoxy composite drive shafts were fabricated using filament winding process with a fiber orientation of [852/±452/252]s. Carbon in the form of multifilament fibers of Tairyfil TC-33 having 3000 filaments/strand was used as reinforcement with low viscosity epoxy resin as the matrix material. The driveshaft is designed to be used in SAE Baja All Terrain Vehicle (ATV) that makes use of a fully floating axle in its rear wheel drive system. The torsional strength of the shaft was tested and compared to that of an OEM steel shaft that was previously used in the ATV. Results show that the composite shaft had 8.5% higher torsional strength in comparison to the OEM steel shaft and was also lighter by 60%. Scanning electron microscopy (SEM) micrographs were studied to investigate the probable failure mechanism. Delamination, matrix agglomeration, fiber pull-out and matrix cracking were the prominent failure mechanisms identified.

Cyclic fatigue and torsional strength of three different thermally treated reciprocating nickel-titanium instruments.

The aim of this study was to evaluate the cyclic and torsional fatigue resistance of the reciprocating single-file systems Reciproc Blue 25.08 (VDW GmbH, Munich, Germany), Prodesign R 25.06 (Easy Dental Equipment, Belo Horizonte, Brazil), and WaveOne Gold 25.07 (Dentsply/Tulsa Dental Specialties, Tulsa, OK, USA). Sixty reciprocating instruments of the systems Reciproc Blue R25 (RB #25 .08 taper), Prodesign R (PDR #25 .06 taper), and WaveOne Gold (WOG #25 .07 taper) (n = 20) were used. Cyclic fatigue resistance testing was performed by measuring the time to failure in an artificial stainless steel canal with a 60° angle of curvature and a 5-mm radius located 5mm from the tip (n = 10). The torsional test (ISO 3630-1) evaluated the torque and angle of rotation at failure of new instruments (n = 10) in the portion 3mm from the tip. The fractured surface of each fragment was also observed using scanning electron microscopy (SEM). In addition, a supplementary examination was performed to measure the cross-sectional area of each instrument 3 and 5mm from the tip. The data were analyzed using one-way ANOVA and Tukey's test, and the level of significance was set at 5%. The cyclic fatigue resistance values of PDR 25.06 were significantly higher (P < 0.05). RB 25.08 showed higher fatigue resistance than WOG 25.07 (P < 0.05). The torsional test showed that PDR 25.06 had lower torsional strength (P < 0.05). No differences were observed between RB 25.08 and WOG 25.07 (P > 0.05). PDR 25.06 showed higher angular rotation values than RB 25.08 and WOG 25.07 (P < 0.05). RB 25.08 presented higher angular rotation than WOG 25.07 (P < 0.05). The cross-sectional area analysis showed that PDR 25.06 presented the smallest cross-sectional areas at 3 and 5mm from the tip (P < 0.05). PDR 25.06 presented the highest cyclic fatigue resistance and angular rotation until fracture compared to RB 25.08 and WOG 25.07. In addition, RB 25.08 and WOG 25.07 had higher torsional strength than PDR 25.06. In endodontic practice, thermally treated reciprocating instruments have been used for the root canal preparation of curved and constricted canals; therefore, these instruments should present high flexibility and suitable torsional strength to minimize the risk of instrument fracture.

Low-dose lithium regimen enhances endochondral fracture healing in osteoporotic rodent bone.

Osteoporotic bone fractures are highly prevalent and involve lengthy recovery. Lithium, commonly used in psychiatric medicine, inhibits glycogen synthase kinase-3β in the Wnt/β-catenin pathway, leading to up-regulation of osteogenesis. Our recent preclinical work demonstrated that a 20 mg/kg lithium dose administered beginning 7 days post-fracture for 14 days optimally improved femoral fracture healing in healthy rats at 4 weeks post fracture (46% higher torsional strength). In this study, lithium treatment was evaluated for healing of osteoporotic bone fractures. Six-month-old ovariectomized rats were subjected to closed, load-drop induced femoral diaphyseal fracture. Two regimens involving treatment initiation on day 7 and day 10, respectively, 20 mg/kg/day oral dose and 14 days duration were evaluated. Femurs of lithium- vs. saline- treated rats were analyzed at 4 weeks (for day 7 onset regimen) or 6 weeks (for day 10 onset regimen) post-fracture by stereology and torsional mechanical testing. Initiation on day 10 led to a significant 50% higher maximum yield torque (primary outcome measure) at 6 weeks (309 vs. 206 N-mm, p = 0.005; n = 7, 7). Initiation on day 7 suggested a trend toward a more modest improvement in maximum yield torque (13%) evaluated at 4 weeks post-fracture (234 vs. 206 N-mm, p = 0.10; n = 10, 13). Qualitatively, lithium-treated femurs demonstrated better periosteal and mineralized callus bridging in the day 10 initiation group. Lithium is a widely-available, orally administered, low-cost drug, which represents a feasible pharmacological intervention for both healthy and osteoporotic fracture healing. This study provides important guidelines for future clinical evaluation of lithium in osteoporotic fracture patients. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1783-1789, 2018.