Torsional Behavior Research Articles

Torsional behaviour of supercoiled DNA regulates recognition of architectural protein Fis on minicircle DNA

Three-dimensional genome organization is indispensable for regulating its functions. Experimental techniques based on the proximity ligation principle have identified spatially segregated domains at a sub-megabase level. The transcriptional activity of these domains is strongly coupled with the supercoiled DNA topology. The underlying molecular principle however remains unknown. By developing a computational framework, we investigate the differential kinetics of an architectural protein Fis on supercoiled DNA. We find that DNA supercoiling favours formation of juxtaposition sites where proteins can perform intersegmental transfer between the spatially close sites. The juxtaposition sites in positively supercoiled DNA are torsionally pinned that results in a slow protein diffusion on it, whereas the torsional behaviour of negatively supercoiled DNA ensures rapid protein-DNA communication and overall fast recognition of the cognate site by proteins. The result is robust for other proteins irrespective of their molecular features. Furthermore, our study suggests that variation in protein diffusivity on different supercoiled DNA also influences the shape of the latter. By unravelling the underlying molecular picture, our results unravel a plausible link between the degree of DNA supercoiling and the regulation of gene transcription that significantly advances the current understanding of the function and organization of chromatin inside cells.

Torsional Behavior of Nickel-titanium Rotary Instruments: What's New?

Torsional Behavior of Nickel-titanium Rotary Instruments: What's New?

Effect of loading modes on torsional behavior of an extruded Mg alloy bar

The torsional deformation with shear stress is crucial for improving mechanical performance of wrought Mg alloys. Consequently, the difference of mechanical behavior between fixed-end and free-end torsion was investigated. It is found that strain hardening behavior is affected by end constraint. The decreased hardening rate is exhibited which is dominated by prismatic slip during fixed-end torsion. For free-end loading, two stages of strain hardening are presented during torsion, i.e., constant hardening rate and slowly decreased hardening rate. The basal slip dominates the onset of plastic deformation. The prismatic slip becomes dominated mechanism at large shear strain. However, the axial effect is sensitive to forward and reversal torsion. The difference of axial stress between forward and reversal torsion under fixed-end is attributed to twin growth. The difference of axial strain is small during forward and reversal torsion under free-end, which is attributed to the activation of tensile twinning.

Simple lower bound limit analysis model for masonry double curvature structures

A new Lower Bound LB plate and shell limit analysis Finite Element FE model for the analysis at collapse of masonry double curvature structures is presented. The discretization relies into hexahedrons assumed infinitely resistant and quadrilateral interfaces where all plastic dissipation occurs. On such interfaces, the flexural behavior is ruled by the interaction between bending moment and axial load, whereas the shear and torsional behavior are modeled by means of an in-plane tangential force, out-of-plane shear and a plate torque. The resultant limit analysis problem obtained by such a formulation is particularly straightforward and the number of variables to deal with very limited. Equilibrium is indeed imposed only on hexahedrons and admissibility on interfaces between adjoining elements. Masonry can be modeled obeying a classic no-tension material or with more complex linearized failure surfaces, for example derived from suitable homogenization techniques. A simple Linear Programming LP problem is so derived, where the actual thickness of the structure is accurately accounted for, a key feature to assess the stability of a vault in case of the no-tension material assumption. The numerical model is validated by means of several meaningful structural examples. A detailed comparison with numerical data available in the literature, obtained for the same examples with alternative numerical approaches shows the accuracy of the method proposed and its usefulness for a fast and reliable prediction of the load carrying capacity of masonry double curvature structures.

BEHAVIOR OF RC BEAMS WITH WEB OPENING SUBJECTED TO PURE TORSION

Many design engineers used to take many services ducts, such as air conditions, water supply, sewage piping, electrical and mechanical conduits, through the space below reinforced concrete (RC) beams forming the floor systems. Then to enhance aesthetics, a false ceiling needs to be provided below the ducts, reducing the clear height of stories, or increasing the total height of structures, particularly for multistoried buildings. For better use of space, such ducts can be taken through web openings in RC beams wherever possible, thereby reducing the overall height of the building. With a focus on a better understanding of the behavior of these beams under pure torsion, this paper presents an experimental study carried out on 23 RC beams with web openings that were tested under pure torsion. Several parameters are studied, such as the length, width (i.e., size), the eccentricity of the openings, and the longitudinal and transverse steel in the chord members. The experimental results indicated that the web opening greatly influences the torsional behavior of the reinforced concrete beams. This paper provides the initial basis for forthcoming experiments and future numerical simulations of RC beams with web openings under combined flexural-shear-torsional behavior that are primary goals in future studies.

Failure mechanisms and loading capacity prediction for rectangular UHPC beams under pure torsion

This study presents an experimental investigation of the loading capacity and failure mechanism of ultra-high-performance concrete (UHPC) beams under pure torsion. Twelve rectangular solid beams were fabricated and tested. The investigated parameters include the volumetric fraction of steel fibers (1.5%, 2.5%, and 3.5%), the longitudinal reinforcement ratio (0–1.54%), and the stirrup ratio (0–1.29%). The torsional behavior, including the crack propagation and failure modes, torque–twist curves, torque–strain curves, cracking and ultimate strengths, and effectiveness of steel fibers were evaluated and presented. Considering the UHPC high tensile strength, a formula for UHPC solid beams was proposed and verified by a reliability analysis. The results showed that compared to conventional concrete beams, the UHPC beams exhibited similar suitably reinforced, partially over-reinforced, and over-reinforced failure modes. Additionally, two different failure modes (type-I and type-II barely reinforced) were identified for UHPC beams. The additional steel fibers improve the torsional properties and directly determine the effective reinforcement ratio. Moreover, the steel fibers with 1.5% or higher volume fractions were proven to be sufficient to replace stirrups, and the proposed formula is effective in predicting the torsional strength of UHPC rectangular solid beams.

Experimental study on Tapered Concrete-Filled Double Skin Steel Tubular columns under torsion

Recent developments in the high-output wind turbine have heightened the need for CFDST support towers. Tapered Concrete-Filled Double Skin Steel Tubular columns with Large Hollow Ratios (TLHR-CFDSTs) are the typical members in the wind turbine towers, which are usually subjected to torsion during the life cycle. It is necessary to pay more attention to these members under torsion due to their tapered shapes and thin-walled cross sections. This paper thus presents an experimental study on the torsional behaviour of the TLHR-CFDST column. Specimens with different tapered angles, hollow ratios, tubes’ thicknesses and axial compression ratios were tested under pure torsion and compression–torsion. The typical failure modes, torque versus deformation relations, strain distributions and the influence of important parameters are revealed. Based on the experimental results, the mechanism of TLHR-CFDST columns under torsion is discussed. The applicability of existing torsional capacity calculation methods is evaluated and finally a simplified method for predicting the torsional capacity of TLHR-CFDST columns is proposed.

Development of efficiency analysis for I-beam steel section with web opening via numerical method

PurposeDue to the enormous increase in economic development, structural steel material gives an advantage for the construction of stadiums, factories, bridges and cities building design. The purpose of this study is to investigate the behaviour of bending, buckling and torsion for I-beam steel section with and without web opening using non-linear finite element analysis.Design/methodology/approachThe control model was simulated via LUSAS software with the four main parameters which included opening size, layout, shape and orientation. The analysis used a constant beam span which is 3.5 m while the edge distance from the centre of the opening to the edge of the beam is kept constant at 250 mm at each end.FindingsThe analysis results show that the optimum opening size obtained is 0.65 D while optimum layout of opening is Layout 1 with nine web openings. Under bending behaviour, steel section with octagon shapes of web opening shows the highest yield load, yield moment and thus highest structural efficiency as compared to other shapes of openings. Besides, square shape of web opening has the highest structural efficiency under buckling behaviour. The lower buckling load and buckling moment contribute to the higher structural efficiency.Originality/valueFurther, the square web opening with counter clockwise has the highest structural efficiency under torsion behaviour.

Endurance Behavior of Cemented Tibial Tray Fixation Under Anterior Shear and Internal-External Torsional Shear Testing: A New Methodological Approach

BackgroundEarly total knee arthroplasty failures continue to surface in the literature. Cementation technique and implant design are two of the most important scenarios that can affect implant survivorship. Our objectives were to develop a more suitable preclinical test to evaluate the endurance of the implant-cement-bone interface under anterior shear and internal-external (I/E) torsional shear testing condition in a biomechanical sawbones. MethodsImplants tested included the AS VEGA System PS and the AS Columbus CR/PS (Aesculap AG, Germany), with zirconium nitride (ZrN) coating. Tibial implants were evaluated under anterior shear and I/E torsional shear conditions with 6 samples in 4 test groups. For the evaluation of the I/E torsional shear endurance behavior, a test setup was created allowing for clinically relevant I/E rotation with simultaneous high axial/tibio-femoral load. The test was performed with an I/E displacement of ±17.2°, for 1 million cycles with an axial preload of 3,000 N. ResultsAfter the anterior shear test an implant-cement-bone fixation strength for the AS VEGA System tibial tray of 2,674 ± 754 N and for the AS Columbus CR/PS tibial tray of 2,177 ± 429 N was determined (P = .191). After I/E rotational shear testing an implant-cement-bone fixation strength for the AS VEGA System PS tray of 2,561 ± 519 N and for the AS Columbus CR/PS tray of 2,824 ± 515 N was resulted (P = .39). ConclusionBoth methods had varying degrees of failure modes from debonding to failure of the sawbones foam. These two intense biomechanical loading tests are more strenuous and more representative of clinical activity.

Large-deformation mechanics of anti-curvature lattice materials for mode-dependent enhancement of non-linear shear modulus

Shear modulus assumes an important role in characterizing the applicability of different materials in various multi-functional systems and devices, such as deformation under shear and torsional modes and vibrational behavior involving torsion, wrinkling, and rippling effects. Lattice-based artificial microstructures have been receiving significant attention from the scientific community over the past decade due to the possibility of developing materials with tailored multifunctional capabilities that are not achievable in naturally occurring materials. In general, the lattice materials can be conceptualized as a network of beams with different periodic architectures, wherein the common practice is to adopt initially straight beams. While shear modulus and multiple other mechanical properties can be simultaneously modulated by adopting an appropriate network architecture in the conventional periodic lattices, the prospect of on-demand global specific stiffness and flexibility modulation has become rather saturated lately due to intense investigation in this field. Thus there exists a strong rationale for innovative design at a more elementary level in order to break the conventional bounds of specific stiffness that can be obtained only by lattice-level geometries. In this article, we propose a novel concept of anti-curvature in the design of lattice materials, which reveals a dramatic capability in terms of enhancing shear modulus in the nonlinear regime while keeping the relative density unaltered. A semi-analytical bottom-up framework is developed for estimating effective shear modulus of honeycomb lattices with the anti-curvature effect in cell walls considering geometric nonlinearity under large deformation. We propose to consider the complementary deformed shapes of cell walls of honeycomb lattices under anti-clockwise or clockwise modes of shear stress as the initial beam-level elementary configuration. A substantially increased resistance against deformation can be realized when such a lattice is subjected to the opposite mode of shear stress, leading to increased effective shear modulus. Within the framework of a unit cell based approach, initially curved lattice cell walls are modeled as programmed curved beams under large deformation. The combined effect of bending, stretching, and shear deformation is considered in the framework of Reddy’s third order shear deformation theory in a body embedded curvilinear frame. Governing equation of the elementary beam problem is derived using variational energy principle based Ritz method. In addition to application-specific design and enhancement of shear modulus, unlike conventional materials, we demonstrate through numerical results that it is possible to achieve non-invariant shear modulus under anti-clockwise and clockwise modes of shear stress. The developed physically insightful semi-analytical model captures nonlinearity in shear modulus as a function of the degree of anti-curvature and applied shear stress along with conventional parameters related to unit cell geometry and intrinsic material property. The concept of anti-curvature in lattices would introduce novel exploitable dimensions in mode-dependent effective shear modulus modulation, leading to an expanded design space including more generic scopes of nonlinear large deformation analysis.

Stress analysis of I-beam with web opening via finite element analysis and experimental study

PurposeThe purpose of this work is to perform the finite element analysis (FEA) for the numerical discretization of sections with different arrangements of Web openings to investigate the torsion behavior. Typical hexagonal and circular Web opening sections are extensively used in steel construction due to economic development in building design. However, the use of sections with different arrangements of Web opening had improved the performance of the section with Web opening in terms of structural behavior which leads to economic design compared to typical I-beam.Design/methodology/approachThe accuracy of FE results allows extensive numerical analysis of stress concentration magnitude for sections with Web openings, concentrating on the sizes and positions of the Web opening. Five shapes and three sizes of Web opening are used in this work. The shapes involved are c-hexagon, hexagon, octagon, circular and square, whereas the sizes of the Web opening involved are 0.67 D, 0.75 D and 0.80 D where D is the height of the Web. Two types of models for 200 × 100 × 8×6 mm steel section involved which is Model 1, where the section with 50 mm edge and 150 mm center-to-center distance and Model 2, where the section with 100 mm edge and 200 mm center-to-center distance.FindingsIt was found that these configurations affect the section with various shapes of Web openings sizes (0.67 D, 0.75 D, and 0.80 D). This also includes the spacing distances, with 50 mm edge and 150 mm center-to-center distance and also a section with 100 mm edge and 200 mm center-to-center distance. Through the FEA results of Model 1 and Model 2, it is found that 50% reduction in horizontal member length in hexagon Web opening, from 50 mm to 20 mm, caused increment about 30%–53% stress concentration in Web for c-hexagon. However, for a stress analysis of c-hexagon, geometry resulted in a lower stress concentration in the Web than other Web opening.Originality/valueAdditionally, the work emphasized the efficiency of Web opening shapes by using an appropriate Web opening radius in section with c-hexagon, hexagon, octagon, square and circular shapes. The final results show the contribution of appropriate Web opening radius to increase the section torsional capacity. It is observed that the torsional capacity at certain loading condition and its angle of twist is analysed.

Numerical analysis on torsional behavior of rectangular and square CFDST members

This paper numerically investigated the behavior of rectangular and square concrete-filled double skin steel tubular (CFDST) members under torsion. The finite element model of rectangular and square CFDST members was established and verified against the test results for the members under cyclic torque. The comparison of the finite element analysis results and experiment results show that the comprehensive finite element model can accurately predict the torsional behavior of rectangular and square concrete-filled double skin steel tubular members. Parametric analyses by using the calibrated finite element model were conducted to investigate the influence of various parameters, such as hollow ratio, concrete strength, yield strength and cross-sectional steel consumption of steel tubes on the torsional behavior of rectangular and square CFDST members. Based on the mechanical analysis and regression analysis methods, the design formula was proposed to predict the torsional capacity of rectangular and square CFDST members. The comparison results show that the proposed formula for predicting the torsional capacity of rectangular and square CFDST members has good accuracy.

Experimental study on torsional behaviour of square concrete filled CFRP-steel tube (S-CF-CFRP-ST)

In this study, the torsional behaviour of square concrete filled carbon fiber reinforced polymer (CFRP) steel tube is revealed by experimental study. Taking the confinement factor of transverse CFRP, strengthening factor of longitudinal CFRP and the compressive strength of cubic concrete as principal factors, total 18 specimens were designed and tested under torsional load. Based on the tests, a numerical simulation method is firstly proposed to estimate the torsional performance of square concrete filled CFRP steel tube (S-CF-CFRP-ST), and then validated against the representative tests results, such as the failure modes, torque-rotation angle curves, and torque-shear strain curves. The test results reveal that the CFRP sheets are all under tension during loading and can cooperate well with steel tube as strains measured on CFRPs are almost same with the ones on steel tube. The failure mode of S-CF-CFRP-ST, such as cracked concrete, ruptured CFRP and torsional deformation of steel tube, belongs to ductile failure. The obtained torque-rotation angle and torque-shear strain curves of tested specimens have similar characteristics and can be divided into elastic stage, elasto-plastic stage and plastic stage. Additionally, the torsional deformation of S-CF-CFRP-ST is in line with plane section assumption before the specimen gets into plastic stage. The good consistence between numerical results and experimental ones reveals that the proposed simulation method can predict the torsional behaviour of S-CF-CFRP-ST reasonably and accurately. Using this verified numerical models, parametric study is conducted to explore the influence of principle factors (e.g. CFPR layers, strength of concrete and steel, and steel ratio) on torsional behaviour of S-CF-CFRP-ST. It is found that the torsional bearing capacity of S-CF-CFRP-ST is slightly improved with the increase of CFRP layers and significantly affected by the strength of the used square steel tube. Additionally, the increase of steel ratio for CF-CFRP-ST member enhances not only the torsional strength but also the initial stiffness.

Experimental study and simulation of non-crimp 3D orthogonal composite shafts during torsional load

Non-crimp 3D orthogonal fabrics are high-tech textiles with three sets of orthogonal yarns. 3D composites reinforced by this fabric have a high performance and wide usages due to their structure. This study attempted to investigate the torsional behavior of Glass/epoxy composite rods reinforced by 3D fabrics experimentally and numerically. Accordingly, three different 3D weaves, including low-density and high-density non-crimp 3D orthogonal, and braid-pultruded fabrics were tested by a torsion tester machine. The results showed that non-crimp 3D orthogonal composites, especially those with a higher density, had better torsional properties than the others, due to the square cross-section and perpendicular fiber involvement in all directions. Optimal torsional properties were obtained for the high-density non-crimp 3D orthogonal composite with the lower void content. Also, a python code was developed to simulate the torsional behavior of the rod composite in macro-scale based on the geometry of the unit cell and the mechanical constants obtained from the meso-scale.

Torsional behaviour of tapered CFDST members with large void ratio

This paper investigated the mechanical behaviour of tapered concrete-filled double skin steel tubular (CFDST) members under combined axial compression and torsion. A series of experiments on CFDST specimens were tested including 8 tapered members and 2 normal members with various hollow ratios and axial compression ratios. The torsional performance of tapered members was analyzed on failure modes, torque-rotation angle curves, and torque-shear strain curves. Verified FE models were developed to carry out the full-range analysis, stress and strain distribution, and the contact stresses between the components. The results showed that the failure mode of tapered CFDST columns was the torsional deformation occurred between 0.5H and the top section. The specimens with a high axial compression ratio occurred additionally inclined outward buckling at 0.8H section, giving rise to a decline in torsional capacity. A low level of axial force promotes the torsional bearing capacity. The effects of the taper angle and hollow ratio on the distribution of shear strain and the torsional capacity at different heights are obvious. Furthermore, employing the section with the lowest torsional modulus for tapered CFDST members is conservative as the designed section, because the torsional capacity might be underestimated. Finally, a simplified method defined by a new calculated section for forecasting the torsional performance of tapered CFDST members is proposed.

Tribological behavior of high-pressure torsion processed biodegradable pure Zn under dry and wet conditions

PurposeZn has been attracting increasing attention with its biological compatibility property as a degradable implant material. Besides mechanical properties, especially for bone implant applications, wear resistance is a crucial mechanical property. The purpose of this study is to investigate HPTed Zn samples’ tribological behavior under dry and simulated body fluid (SBF) lubrication conditions.Design/methodology/approachPure Zn powders were consolidated via the high-pressure torsion (HPT) method with 1, 5 and 10 rotations. Cast pure Zn samples were used as the control group. The wear behavior of pure Zn samples was investigated under dry and SBF lubrication conditions with a ball-on testing method. The wear tracks were observed with a mechanical profilometer and scanning electron microscope (SEM).FindingsThe application of HPT not only improved the mechanical strength and degradation performance but also improved wear resistance. However, tests with SBF resulted in higher wear rates. Besides, SBF significantly masked the positive effect of HPT on the coefficient of friction (COF). Although with SBF tests, 10 HPT rotation samples resulted in the lowest wear width and volume.Originality/valueThe main originality of this study is to reveal the HPT process and SBF effects on the tribological behavior of pure Zn to observe their potential usage for bone implant applications.

Experimental investigation on torsional behaviors of ultra-high-performance fiber-reinforced concrete hollow beams

Limited studies have been conducted on the torsional performance of ultra-high-performance fiber-reinforced concrete (UHPFRC) hollow beams. This paper presents experimental investigations on eight UHPFRC hollow beams with various cross-sectional dimensions, wall thicknesses, and cross-section types. Their torsional responses, including the failure modes, torque−twist curves, torque−strain curves, torsional stiffness, and ductility indexes, are presented. Theoretical methods were employed to evaluate the cracking and ultimate torques. The results indicated that the UHPFRC hollow beams with and without flange plates exhibited a similar failure model, with the main cracks penetrating spirally. The cross-sectional dimensions, wall thicknesses, and cross-section types significantly affected the ultimate torque, whereas the cracking torque was affected only by the cross-sectional dimensions. A comparison of the experimental and theoretical results indicated that the American Concrete Institute code provisions provided good predictions for the cracking torque, whereas the existing theoretical methods offered unsatisfactory predictions for the ultimate torque. Thus, the equivalent wall thickness of UHPFRC hollow beams must be evaluated with a higher accuracy.

Experimental study of seismic torsional behavior of reinforced concrete walls

Experimental study of seismic torsional behavior of reinforced concrete walls

Experimental Findings and Validation on Torsional Behaviour of Fibre-Reinforced Concrete Beams: A Review.

Fibres have long been utilized in the construction sector to improve the mechanical qualities of structural elements such as beams, columns, and slabs. This study aims to review the torsional behaviour of various forms of fibre reinforced concrete to identify possible enhancements and the practicability of concrete structural beams. Concrete reinforced steel fibre, synthetic fibre, and hybrid fibre are examples of fibre reinforced concrete. The review found that the mixing, orientation, and volume of fibres, the size of coarse particles, the aspect ratio of fibres, and the stiffness of fibres all affect the torsional strength of fibre reinforced concrete. Nevertheless, the application of fibres to recycled self-consolidating concrete of various forms needs to be explored and studied to ascertain its feasibility to facilitate greener concrete. Thus, with the results compiled in this review paper, it was possible to delimit advances and gaps on the effect of editing reinforcement fibres in relation to the torsion of structural elements.

Structural Mechanics of cylindrical fish-cell zero Poisson’s ratio metamaterials

In this paper, a novel cylindrical metamaterial exhibiting zero Poisson’s ratio in two different directions is introduced. Detailed CAD modelling of a curved Fish-Cells necessary for numerical and experimental analysis are presented. High-fidelity finite element models are developed to assess the homogenisation studies of Poisson’s ratio, Young’s modulus and torsion behaviour, demonstrating the curvature effect and independency of the mechanical behaviour of cylindrical Fish-Cells metamaterial from tessellation numbers. Experimental analysis is performed to validate the zero Poisson’s ratio, deformation and fracture mechanism discussed in numerical simulations. Moreover, buckling and modal behaviours of the cylindrical Fish-Cells metamaterials are studied and compared with equivalent shell models.