Torsional Strength Research Articles

Design and Characterization of Mg Alloy Pedicle Screws for Atlantoaxial Fixation

To investigate the feasibility of using absorbable Mg alloy pedicle screws for atlantoaxial dislocation fixation, four types of Mg alloy pedicle screws of different thread forms were designed, and simulation analysis of the pull-out force was performed using the finite element method. Stress and displacement distributions of the atlantoaxial fixation model were obtained. Subsequently, screw samples were prepared using the WE43 Mg alloy for extraction, torsion, and immersion corrosion tests. Finite element analysis results showed that the pull-out forces of triangular, rectangular, trapezoidal, and zigzag thread screws were 552.61, 540.91, 546.4, and 542.74 N, respectively, and the stresses on the screws were 146, 185, 195, and 265 MPa, respectively, when they were pulled out. In other words, the triangular thread screw had the largest pull-out resistance and smallest stress peak. The average corrosion rate of Mg alloy screws in vitro was 0.46 mg·cm−2·day−1. Compared with that before corrosion, the extraction resistance of the corroded screws did not change significantly; however, the torsional strength decreased, but it was still greater than the torque required for screw implantation. It can be concluded that triangular thread Mg alloy pedicle screws have good extraction resistance and mechanical stability and can meet the load-bearing requirements for atlantoaxial dislocation fixation. The degradation of the Mg alloy reduced the mechanical strength of the screws, but the triangularly threaded screws can still maintain their effectiveness.

Influence of temperature on the torsional properties of two thermally treated NiTi rotary instruments

This study aimed to evaluate the influence of temperature on torsional strength and angular deflection of two experimental NiTi rotary instruments manufactured from Blue and Gold thermal treatments and with identical cross-sections. A total of 40 experimental NiTi instruments 25.06 and with a triangular cross-section and manufactured from Blue and Gold thermal treatments were used (n=20). The torsional test was performed in the 3 mm from the tip of the instrument according to ISO 3630-1. The torsional test evaluated the torsional strength and angular deflection to failure at room temperature (21°C ± 1° C) and body temperature (36°C ±1°C). The fractured surface of each fragment was observed by using scanning electron microscopy (SEM). Data were analyzed using an unpaired t test for inter and intra-group comparison and the level of significance was set at 5%. The results showed that the body temperature did not affect the torsional strength and angular deflection of the instruments when compared with room temperature (P>0.05). However, at body temperature, the Blue NiTi instruments presented significantly lower angular deflection in comparison with Gold NiTi instruments (P<0.05). There was no significant difference regarding the torsional strength of the instruments at body temperature (P>0.05). The temperature did not affect the torsional strength of the instruments manufactured from Blue and Gold technology. However, the Blue NiTi instruments presented significantly lower angular deflection than Gold instruments at 36°C temperature.

Lateral Torsional Buckling Capacity Assessment of Cellular Steel Beams

A cellular beam is a widened I-profile section with circular web openings. This type of perforated-web beam has been used immensely throughout the world during the last two decades. Lateral torsional buckling is one of the steel beam’s limit state designs. This study aims to investigate the behavior of cellular beams against lateral torsional buckling. A validated numerical model was employed in a sort of parametric study. The examined parameters are applied load configurations and the geometrical ratios of flange width-to-thickness, web height-to-thickness, openings’ spacing-to-diameter, beam’s span-to-depth, and opening’s diameter to beam-depth. Based on the results of the parametric study, a lower-bound design formula for predicting the lateral torsional buckling moment resistance of simply supported cellular beams was proposed. The suggested design formula can predict, with an acceptable degree of accuracy, the lateral torsional bending strength of simply supported cellular beams being subjected to various types of destabilizing loads.

Estimation of patch-loading resistance of steel girders with unequal trapezoidal web-corrugation folds using nonlinear FE models and artificial neural networks

Corrugated-web steel I-girders (CWGs) have better shear and torsional strengths, offering additional stability against out-of-plane web buckling and local crippling under patch loads than flat web girders. CWGs are lightweight and more cost-effective than flat web beams for applications in buildings and bridges. The existing design models for estimating patch-loading resistance in CWGs assume equal widths in web corrugation folds for a simply supported span. This study examined the parametric influence of unequal trapezoidal-web folds on the nonlinear behavior of CWGs under compressive patch loading. A total of 533 steel I-girders with simply supported (SS) and 478 cantilever spans (CS) were analyzed using a calibrated nonlinear finite element (FE) methodology. The generated datasets of CWGs consisting of governing parameters (i.e., girder geometry and material properties) were mapped to refined patch-loading resistance using artificial neural networks (ANNs) for both CS and SS-type spans. The proposed ANN formulation showed better prediction accuracy (mean absolute error of about 2–4% in this study) than the existing design models for estimating the patch-loading resistance of CWGs. For practical applications and conservative patch-loading resistance, prediction modification factors were also proposed for ANN formulation and existing design models within a targeted error margin.

Investigation of mechanical behavior of graphene nanoplatelets and carbon fiber-reinforced hybrid laminate composites under different environment aging conditions

In this study, the effect of graphene nanoplatelet (GNP) of different amounts (0, 0.25, 0.5, 0.75, and 1.0 wt.%) on the carbon fiber-reinforced polymer (CFRP) composites were investigated to determine mechanical properties under different environment aging conditions. The mechanical properties were examined under three different environment aging conditions (25°C, 55% RH (relative humidity); 25°C, 75% RH; and 75°C, 75% RH). Humidity and temperature are the main environmental factors discussed in this study to evaluate the mechanical characteristics. The results determine that the enhancement of GNP from 0.25 to 0.50 wt.% as a reinforcement improved the tensile, flexural, interlaminar shear strength, impact, and torsional strength of the developed hybrid composites. Further, an increase in wt.% of GNP in composites up to 1.0% reduces tensile, flexural, and interlaminar shear strength compared to neat CFRP in all aging conditions. But the torsional and impact strength are higher at 0.75–1.0 wt.% GNP as compared to neat CFRP in all conditions. It is observed that there is a reduction in tensile, flexural, shear, torsional, and impact properties at higher temperature and humidity conditions. The nanoparticle dispersion, agglomeration, and fracture surface of composites is analyzed by field emission scanning electron microscopy.

Torsional Strength of Recycled Coarse Aggregate Reinforced Concrete Beams

This study discusses the torsional capacity of recycled coarse aggregate (RCA) reinforced concrete beams under pure torsion based on the experimental findings available in the literature. The experimental data on RCA specimens were collected and compared with the conventional concrete specimens with key variables, such as compressive strength and longitudinal and transverse reinforcement ratios, as those variables affect the torsional capacity of reinforced concrete beams. Overall, the database consisted of experimental results from 30 RCA specimens and 256 natural coarse aggregate (NCA) specimens. The result shows that specimens with a 100 % replacement ratio have the lowest strength. In addition, as the structural mechanism of torsion is similar to the shear mechanism in reinforced concrete beams, a comparative analysis was performed with RCA specimens subjected to shear force. It was concluded that the RCA has a similar effect in strength reduction for the specimens subjected to torsion or shear with a 100% replacement ratio. However, further study and experimental evidence are required to confirm the applicability of the recycled aggregate to produce and design the structural members.

Effects of building direction and loading mode on the high cycle fatigue strength of the laser powder bed fusion 316L

The present study aims to investigate the high cycle fatigue (HCF) performance of steel 316L fabricated by the laser powder bed fusion (LPBF) process. Bending and torsional fatigue test specimens built horizontally (0°), inclined (45°), and vertically (90°) have been prepared and tested. Stress-relieving heat treatment was carried out to reduce the residual stresses. The 90°, 45°, and 0° built near-net-shape and polished specimens have fatigue strengths between 140 and 250 MPa under bending loading and 150 and 170 MPa under torsion loading. This difference illustrates a more pronounced defect sensitivity in bending compared to torsion. Fractographical analyses revealed the fatigue failure mechanisms. As the building direction inclines from vertical to horizontal, the effective areas of inherent defects diminish contributing to improving fatigue strength under bending loading whilst the differences from building directions in torsional fatigue strengths are minor. Microstructural features are seen to compete with inherent defects to affect fatigue performance in the condition that the effective defect sizes are close to the critical fatigue crack size.

Ideal Length and Diameter for Intramedullary Screw Fixation of Metacarpal Fractures: A Biomechanical Study

This biomechanical study evaluated the effect of intramedullary screw diameter and length relative to 3-point bending force and torsional force when used to stabilize metacarpal shaft fractures. Transverse osteotomies were made in the proximal metacarpal shaft in 36 middle finger metacarpal fourth-generation composite Sawbones. To compare screw diameters, antegrade intramedullary screws of 30-mm length were placed in 6 metacarpals, which included 4.7-mm Acutrak 2, Standard Acutrak 2 (4.0 mm), and Mini-Acutrak 2 (3.5 mm) screws. To compare screw lengths, metacarpals were fixated with Standard Acutrak 2 screws of 26, 30, or 34 mm in length, with screw tips bypassing the osteotomy by 6, 10, or 14 mm, respectively. A 6 degrees of freedom robot was used for torsional and 3-point bending testing. Increasing screw diameter demonstrated significant differences in both 3-point bending and torsional strengths. Maximum torsional loads were 69 Ncm (4.7-mm Acutrak 2), 45 Ncm (Standard Acutrak 2), and 27 Ncm (Mini-Acutrak 2) (P < .05). Loads to failure in the 3-point bending tests were 916 N (4.7-mm Acutrak 2), 713 N (Standard Acutrak 2), and 284 N (Mini-Acutrak 2) (P < .05). Differing screw lengths demonstrated significant differences with maximum torsional loads when comparing the 26-mm screws (22 Ncm) with 30- and 34-mm screws (45 and 55 Ncm, respectively) (P < .05). The 3-point dorsal bending strengths were significantly different between the 26-mm screws (320 N) and 30- and 34-mm screws (713 N and 702 N, respectively) (P < .05). The results demonstrated significantly higher torsional strength and resistance to 3-point bending with larger intramedullary screw diameters. Further, when selecting the intramedullary screw length, the screw tip should pass at least 10 mm beyond the fracture. This study provided biomechanical evidence to guide surgeons in selecting intramedullary screw diameter and length for treating metacarpal fractures.

Torsional Behavior of Steel-Concrete-Steel Sandwich Beams with Welded Stirrups as Shear Connectors

The structural performance of a steel-concrete-steel sandwich beam (SCSSB) with welded stirrups to the steel skin plates as shear connections exposed to a pure torsion load was studied in this paper. Eight SCSSB specimens were fabricated and tested under pure torsion. The effects of the compressive strength of the concrete core, 26 and 35 MPa, the thickness of the top and bottom steel skin plates, 2 and 4 mm, and the degree of shear interaction, which represents the number of beam stirrups, between the steel skin plates and the concrete core are 75, 100, and 125%. The experiment beams revealed a similar mode of failure for all SCSSB specimens regarding all considered variables, which started with inclined cracks along the specimens’ side faces and ended with local separation between one of the steel skin plates (top or bottom) and the concrete core. In addition, the experiment results showed an increase in the torsional strength with the increase in the shear connection ratio and the thickness of the steel skin plate, as well as with the increase in the strength of the concrete core. However, it was observed that the torsional ductility of the tested beams is proportional directly to the steel skin plate thickness and degree of interaction and inversely with the concrete compressive strength. The results showed that the use of steel skin plates with welded stirrups as a shear connection could reduce the negative effect of increasing the compressive strength of the concrete core on the torsional ductility of SCSSB. Doi: 10.28991/CEJ-2023-09-01-016 Full Text: PDF

RESISTÊNCIA AO CISALHAMENTO À COMPRESSÃO E À TORÇÃO DE JUNTAS COLADAS DE PINUS E ADESIVO POLIURETANO CONFECCIONADAS COM DIFERENTES ÂNGULOS

ABSTRACT Glued Laminated Timber technology allows the construction of wooden structural components bonded with adhesive. This technology enables the creation of large-scale structures, with technological control over the material, and in a competitive industrial system. Focusing on the structural application of wood, the present study assessed the strength of bonded joints with different angles between the fibers of Pinus sp. wood, joined with a two-component polyurethane adhesive based on vegetable oils. The bonded joints were fabricated with angles of 0°, 10°, 20°, 30°, 45°, 60°, 70°, 80°, and 90°, and were evaluated for shear strength under compression and torsion. When regression analysis was performed, shear compression values showed compliance with Hankinson’s equation, with an R2 value close to 0.76. However, shear torsion results yielded R2 values near 0.17. Thus, Hankinson’s equation was unsuitable as an estimator for torsional shear strength values. The specimens showed a different mechanical response to shear when tested in compression compared to those tested in torsion.

Improving the Torsional Strength of Reinforced Concrete Hollow Beams Strengthened with Externally Bonded Reinforcement CFRP Stripe Subjected to Monotonic and Repeated Loads

Improving the Torsional Strength of Reinforced Concrete Hollow Beams Strengthened with Externally Bonded Reinforcement CFRP Stripe Subjected to Monotonic and Repeated Loads

Enhancement of the torsional strength of commercial ABS samples manufactured using a tabletop 3D printer: an application of innovative hybridised tools and techniques

Enhancement of the torsional strength of commercial ABS samples manufactured using a tabletop 3D printer: an application of innovative hybridised tools and techniques

Enhancement of the torsional strength of commercial ABS samples manufactured using a tabletop 3D printer: an application of innovative hybridised tools and techniques

Enhancement of the torsional strength of commercial ABS samples manufactured using a tabletop 3D printer: an application of innovative hybridised tools and techniques

Meso‐scale modeling of size effect on pure torsional failure of concrete‐filled steel tubular columns

AbstractThe mechanical properties of concrete‐filled steel tubular (CFST) columns with different sizes under torsional load were studied, aiming to further explore the pure torsional failure mechanism and size effect behavior of CFST columns. First, a 3D meso‐scale numerical model of CFST is established and compared with the existing experimental data. Second, the torsional failure mechanism of CFST column under different section sizes, constraints (confinement coefficient), and cross‐sectional shapes is considered. Results show that: (1) the nominal torsional strength of CFST columns presents a size effect, and the columns with square cross‐section present stronger size effect than the ones with circular shape; (2) with the increase of the confinement coefficient, the size effect of the nominal torsion strength is weakened. Finally, considering the quantitative influence of the size effect, a formula for calculating the pure torsional capacity of CFST columns was developed.

Torsional strength analysis of universal joint’s ZP-11A due to yokes modification and materials

The study examined the strength of the universal joint after it was loaded with torsion. It used different materials that can withstand tensile stress in accordance with accepted principles and made modifications to the yoke as a result of the topology optimization process. The topology optimization determined that the yoke's part needed to withstand load without changing its dimensions and minimize stress distribution. According to the results, the maximum shear stress on the spider of the original universal joint model made of JIS-SF590A steel was 84.57 MPa, the shear stress on the yoke component was 30.84 MPa, and the maximum von Mises was 341.1 MPa. As a result of using JIS-SF590A steel, yoke modification 3 has produced a reduction in shear stress of 12.97 % and a reduction in von Mises stress of 35.33 % from the original yoke. This is the most efficient design of yoke and also this modified yoke form provides a wider elevation angle and is easier to manufacture.

Performance of recycled aggregate concrete-filled high-strength steel tubes under axial compression, tension and torsion

This paper reports the performance of recycled aggregate concrete-filled high-strength steel tubes (RAC-FHST) under axial compression, tension and torsion. A total of 50 specimens, including 22 compressive specimens, 16 tensile ones and 12 torsional ones, were tested. The main parameters varied in the tests were the sectional type, the steel yield strength and the replacement ratio of recycled coarse aggregate (RCA). Analysis on the full-range load–deformation response, the typical failure modes, the ultimate strength, the passive confinement effect and the influence of key parameters were conducted. Results reveal that the use of RCA affected the failure modes especially when subjected to tension or torsion. Meanwhile, the performance of RAC-FHST is improved due to the excellent confinement effect of high-strength steel tube. The finite element modelling method was used to investigate the mechanical property and the effects of important parameters. Simplified models for the calculation of ultimate compressive, tensile and torsional strengths of RAC-FHST were proposed. Based on reliability analysis, the effects of the steel yield strength, the concrete strength and the confinement factor on the reliability index of RAC-FHST were evaluated.

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.

Characterization of the file-specific heat-treated ProTaper Ultimate rotary system.

To compare design, metallurgy and mechanical performance of the ProTaper (PT) Ultimate system with instruments of similar dimensions from the ProGlider, PT Gold and PT Universal systems. New PT Ultimate instruments (n=248) were compared with instruments of similar dimensions from ProGlider (n=31), PT Gold (n=155) and PT Universal (n=155) systems regarding their number of spirals, helical angle, blade symmetry, tip geometry, surface finishing, nickel/titanium ratio, phase transformation temperatures and mechanical performance. One-way anova and nonparametric Mood's median tests were used for statistical comparison (α=5%). All instruments had symmetrical blades without radial lands or flat sides, similar surface finishing and an almost equiatomic nickel/titanium ratio, whilst the number of spirals, helical angles and the tip geometry were different. PT Ultimate instruments showed 3 distinct heat treatments that matched with the colour of their metal wire. Slider and ProGlider instruments had similar R-phase start (Rs) and R-phase finish (Rf) temperatures. SX, F1, F2, F3 and Shaper instruments showed equivalent heat treatments (Rs ~45.6°C and Rf ~28.3°C) that were similar to their PT Gold counterparts (Rs ~47.9°C and Rf ~28.2°C), but completely distinct to the PT Universal ones (Rs ~16.2°C and Rf ~-18.2°C). Amongst the PT Ultimate instruments, the lowest maximum torques were observed in the SX (0.44 N cm), Slider (0.45 N cm) and Shaper (0.60 N cm) instruments, whilst the highest was noted in the FXL (4.90 N cm). PT Ultimate Slider and ProGlider had similar torsional (~0.40 N cm) and bending loads (~145.0 gf) (p=1.000), whilst the other PT Ultimate instruments showed statistically significantly lower maximum torque, higher angle of rotation and lower bending load (higher flexibility) than their counterparts of the PT Universal and PT Gold systems. The PT Ultimate system comprises instruments with 3 distinct heat treatments that showed similar phase transformation temperatures to their heat-treated analogues. PT Ultimate instruments presented lower torsional strength and superior flexibility than their counterparts, whilst maximum torque, angle of rotation and bending loads progressively increased with their sizes.

Numerical study on Role of Shear Key in Precast Beam to Beam Connection Subjected to Torsion

Connections play an important role in behaviour of precast concrete structures. It is also observed that the failure of precast building took place because of connection failure. Generally connection between precast elements are designed for axial force, shear force and bending moment. But when the precast beam supports precast slab of different span on both the side, torsional moment cannot be neglected. Therefore, it is important to study the behaviour of precast connections under the effect of pure torsional loading. In this paper effectiveness of shear key on behaviour of precast beam to beam connection under pure torsion is presented. A numerical simulation is carried out to investigate the torsional behaviour of three different type of precast wet connections with and without shear key using Finite Element Method based software ABAQUS. Projected longitudinal reinforcement of precast beam elements are welded after their erection and the gap is filled with concrete. The damaged plasticity model is employed for modelling the behaviour of concrete and elastic perfectly plastic models are employed for the modelling of behaviour of steel reinforcement. A prefect bond is assumed between the steel reinforcement and concrete. The damage along cracks, are modelled through concrete damage parameters. Precast beam connection with out shear key is considered as control beam. While other beam to beam connections have shear key of different configuration. Torque v/s twist behaviour and damage patterns as obtained from numerical analysis of different precast beam connections with shear key are compared with control specimen. Analysis results exhibited enhanced torsional strength of precast beam connection with shear key in comparison of connection without shear key.

Determination of Ultimate Torque and Twist of High Strength RC Beams with Ferrocement “U” Wraps: Different Approaches

Designers are more interested in strength at cracking rather than ultimate strength. Still then beyond cracking, the structures are able to sustain more loads. So, determination of ultimate strength is an important parameter in design field. Evaluation of ultimate torsional capacity of high strength distressed beams with ferrocement “U” wrap has been presented here. The evaluation procedure involves experimental results, results obtained by analytical method. As the above two methods are not providing quick solution, rather than the first one is based on destruction of prototype structure for evaluation of strength. Other methods such as soft computing methods have been employed. Two methods MARS and WASPAS are employed here to compute the torsional strength of “U” wrapped beams. These two methods provide quick solutions to estimate the torque and twist at ultimate stage. Predicted values by these methods are within acceptable limits. At ultimate stage , the “U” wrapped beams are able to resist torque more than 41.37% than the unwrapped beams and a completely over reinforced beam resists 98.01% more than plain “U” wrapped beams. Under reinforced “U” wrap beams have undergone 23.9 times more twist than that of plain “U” wrap beams. This proves effectiveness of “U” wrap on periphery of distressed beams.