Pure Torsion Research Articles

Study on the effects of the tension and torsion loading sequence on the mechanical properties of a 20 carbon steel

Abstract In engineering applications, cylindrical bars of 20 carbon steel are often subjected to a combination of tensile loading and torsional loading during the service, thereby causing premature failure or an accident. In order to explore the influence of loading sequence of tension and torsion on the mechanical properties of 20 carbon steel, tests of combined tension-torsion loading and combined torsion-tension loading are employed in this work. During experiments, a microscope is used for the in situ characterization of micro-damage evolution on the surface of specimens. At the same time, to analyze the influence of loading sequence on the stress distribution, ABAQUS software is utilized to conduct the relevant finite element simulation, where the results of finite element analysis are consistent with the experiments. Evidently, the torsional strength of 20 carbon steel is decreased with an increase in the pre-tensile stress, under the combined tension-torsion. However, the tensile strength of 20 carbon steel is enhanced with the increasing pre-torsional angles, under the combined torsion-tension. Moreover, the in situ images characterized the micro-damage evolution of 20 carbon steel under pure tension, pure torsion, combined tension-torsion and combined torsion-tension. It is concluded that the deference in loading sequence changes the failure mechanism of 20 carbon steel is different.

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.

Improved Equations for the Torsional Strength of Reinforced Concrete Beams for Codes of Practice Based on the Space Truss Analogy.

Design codes provide the necessary tools to check the torsional strength of reinforced concrete (RC) members. However, some researchers have pointed out that code equations still need improvement. This study presents a review and a comparative analysis of the calculation procedures to predict the torsional strength of RC beams from some reference design codes, namely the Russian, American, European, and Canadian codes for RC structures. The reliability and accuracy of the normative torsional strengths are checked against experimental results from a broad database incorporating 202 RC rectangular beams tested under pure torsion and collected from the literature. The results show that both the readability and accuracy of the codes’ equations should be improved. Based on a correlation study between the experimental torsional strengths, and geometrical and mechanical properties of the beams, refined yet simple equations are proposed to predict torsional strength. It is demonstrated that the proposed formulation is characterized by a significant improvement over the reference design codes. The efficiency of the proposed formulae is also assessed against another equation earlier proposed in the literature, and an improvement is noted as well. From the results, it can be concluded that the proposed equations in this study can contribute to a more accurate and economical design for practice.

Quasi-static mechanical behavior of filament wound composite thin-walled tubes: Tension, torsion, and multi-axial loading

In recent years, with the application of filament wound composite (FWC) materials in shaft structures, the mechanical behavior study of this material under related loads is urgently needed. This paper presented the experimental study on the mechanical behavior of filament wound carbon fiber reinforced polymer under uniaxial tensile loading, torsional loading, and multi-axial loading. To alleviate the stress concentration effect caused by clamping, an improved filament wound specimen was designed and produced by reinforcing each end. A new method of analysis from the inside of a winding pattern was used to investigate failure modes and behavior under different loading conditions. To further describe the mechanical behavior, the strength, stiffness, and failure mechanisms were evaluated by the stress analysis and the measurement techniques, such as the extensometer, the strain gauge, and the scanning electron microscope (SEM). The results show that the pipe is nonlinearly progressively damaged until final failure under tensile load. Brittle failure is dominant under pure torsional load. Under tension–torsional load, the pipe is progressively damaged with slight nonlinearity and the final failure strength is much lower than the pure tension or torsion load condition.

The mechanical response of commercially pure copper under multiaxial loading at low and high strain rates

In this paper, we present the dynamic response of commercially pure copper subjected to combined tension-torsion loads representative of real case impact scenarios. Experiments were conducted both quasi statically, at a strain rate equal to 10−3 s−1, and dynamically at strain rates in the region between 500 s−1 and 1000 s−1. All high rate experiments were conducted using a novel Split Hopkinson Tension-Torsion Bar instrumented with high-speed photographic equipment. The dynamic combined loading experiments demonstrate the capability of the apparatus to generate longitudinal and torsional stress waves which are synchronised upon loading of the specimen. The presented data show that dynamic equilibrium conditions and nearly steady strain rates were achieved during the experiments. Additionally, the analyses of the loading paths show that nearly proportional strain loading was attained during testing.The measured experimental results illustrate, for the first time, the failure stress locus of the material over a wide range of stress states including pure torsion, shear-dominated combined tension-shear, tension-dominated combined tension-shear and plain tension. The quasi-static and dynamic failure envelopes are herein presented in the normal stress vs shear stress space to motivate the development of accurate and effective constitutive models. To conclude, the Drucker-Prager criterion was employed to approximate the failure loci and to assess the rate sensitivity of the material. A moderate asymmetry of the uniaxial ultimate stresses in tension and compression is predicted both at quasi-static and dynamic strain rates.

Investigating the Response of Single Pile Under Pure Torsion

Abstract The single pile is a structural element that has an important role in supporting any part of the superstructure. This paper adopted three dimensional finite element modelling by using ANSYS to discover the influence of soil size domain on pile diameter, pile length, load eccentricity and torsion magnitude. One type of soil was used and described by Drucker-Prager model. The numerical analysis has been performed to show how the variation in soil size domain effects on the behaviour of single pile under torsion load. The procedure which is adopted in the investigation depends on fixing all variables and changing one variable to show the impact of this variable on the pile response considering soil domain variation. From the investigation, it is obvious that the pile diameter, eccentricity and torsion load have a major influence on the pile response, while the pile length has a minor influence on the pile response. Here, the increase in pile diameter reduces the load transfer to the soil; also the increase in eccentricity increases the load transfer to the soil while the increase in soil domain reduces the pile response. When the torsion load increases the pile response increases too. The pile response refers to displacement, rotation, shear force and bending moment.

Characterization of pure torsion of a rubber-like cylinder using a hyperelastic model

Characterization of pure torsion of a rubber-like cylinder using a hyperelastic model

A constitutive model for fibrous tissues with cross-linked collagen fibers including dispersion — With an analysis of the Poynting effect

The present work deals with cross-links in collagenous tissues and proposes a planar continuum model for large strains to mechanically characterize, for example, the well-known stiffening effect associated with the presence of these cross-links. A key novelty of the paper is the consideration of dispersed fibers connected by randomly distributed cross-links. The model is essentially based on two mechanisms: (i) a fiber dispersion-induced cross-link dispersion and (ii) a fiber-independent cross-link dispersion connecting two arbitrary parallel fibers of the sample space. Within the framework of the generalized structure tensors, we derive appropriate invariants that enter the stored-energy function, taking into account the stiffness and relative orientation of the cross-links and the cross-link-fiber interaction. To illustrate the power of the proposed model, we first consider uniaxial tension and simple shear. We investigate the influence of different cross-link configurations on the stress response. In particular, we are interested in simple shear and the sign of the normal stress perpendicular to the shear planes, which is referred to as the Poynting effect. We show that the cross-links have a significant impact on the normal stress considered. This may provide a deeper insight into the microstructural mechanisms in semi-flexible biopolymer gels that are responsible for the tendency, in simple shear, of the top and bottom faces to approach each other. Finally, we investigate the Poynting effect that occurs in a circular hollow cylinder under pure torsion, i.e. how the axial normal force correlates with the cross-linked fibrous microstructure of the specimen.

Stress distribution in laminated composite tubular joints with damaged adhesive layer under torsion

ABSTRACT This study investigates the effect of geometric and mechanical properties of the adherends and adhesive layer on the shear stress distribution in a damaged adhesively bonded tubular lap joint (laminated composite to steel) under pure torsion. Using first-order shear deformation theory, the equilibrium equations are deduced and solved by the generalized differential quadrature (GDQ) method, results of which were compared and verified with those of finite element solution. Results show that for the steel and [±15]10 composite adherends, increasing the elastic modulus of the adhesive layer increases the maximum shear stresses in the adhesive layer while increasing the joint length beyond its so-called effective bond length has no additional effect on the peak shear stress in the adhesive. Additionally, selecting a quasi-isotropic lamination setup instead of [±15]10 reduces the peak shear stress, where the use of an orthotropic tube with the lamination sequence of ±45° further reduces this magnitude. Additionally, depending on the size and location of a void or debond in the adhesive layer, the peak shear stresses can gain higher values, with almost similar behaviors for the two defects. Nonetheless, for defects far enough from the adhesive ends, their effects on the adhesive peak shear stress seemed to be negligible.

An experimental study on reinforced concrete beam with continuous spiral stirrups under pure torsion

This research investigated continuous rectangular spiral shear reinforcement as transverse reinforcement under pure torsion and compared it with conventional concrete beams. This present study tested three different continuous rectangular spiral stirrup (80°, 75°, and 45°) and one with traditional type stirrup (90°). M30 grade concrete and Fe 415 steel were used. The Test results indicate that the maximum ultimate torque at 75° is 32 kNm. Also, the maximum percentage increase in ductility is 19%. The maximum stiffness was observed at 80° stirrups is 2104 kN.m/radians.

Closed form solutions for the strain localization problem in a softening circular bar in pure torsion with the continuum damage and the embedded discontinuity models

The boundary value problems and closed form solutions for the strain localization in a softening bar under pure torsion with the continuum damage and the embedded discontinuity formulations are developed. In this formulation, quasi-brittle materials such as concrete or mortar are considered. The boundary value problem is developed from a variational formulation and the corresponding Euler-Lagrange differential equation. These formulations include not only the continuum damage model, in which the twist angle jump and the angular strain concentration are smeared into the volume of the bar, but also the embedded discontinuity model, in which the twist angle jump and the angular strain localization are lumped into a zero thickness localization zone. The non-linear behaviour of the materials is described by a continuous constitutive model for the continuum damage model and by a discrete constitutive model for the embedded discontinuity model; both constitutive relationships include linear or exponential softening. Solutions to overcome the problem of crack bandwidth dependency when modelling strain localization with continuous models are developed, these solutions are based on a rational analysis of the kinematics of the strain model and on the fracture energy per unit area. To validate the developed closed form solutions for the strain localization problem in a softening bar under torsion, three examples of concrete cylindrical specimens under torsion are presented. The relationship between the total area under the twisting moment-twist angle curves and the fracture energy of the material guarantees the correctness of the developed closed form solutions.

Design and Kinematic Modeling of In-Situ Torsionally-Steerable Flexible Surgical Robots

Flexible robots have been widely used in minimally-invasive surgery because of their dexterity and accuracy. However, the torsion of end-effector under bending state usually produces unnecessary concomitant motion of the robot arm. This letter proposes a novel design of <i>in-situ</i> torsionally-steerable tendon-driven flexible robots for otolaryngology surgery. This kind of robots have three motion modes: pure torsion, pure bending and fusion modes. Among them, the fusion mode provides a novel <i>in-situ</i> torsional motion which can maintain the position and approach vector of the end-effector during the operation. A constant curvature-based kinematic model has been presented to handle different motion modes. Finite element analysis (FEA), numerical simulations and experiments have been conducted to test the robot design and the proposed model. The FEA shows that the maximum torsional deformations are 0.114 mm and 0.908 mm for straight and maximum bending configurations, respectively. The position, rotation and direction errors of the prototype are 1.53 mm, 2.08<inline-formula><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> and 2.71<inline-formula><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula>, respectively. The results indicate that the proposed flexible surgical robots are feasible for <i>in-situ</i> torsional motion.

A softened membrane model for single-box multi-cell composite box-girders with corrugated steel webs under pure torsion

To analyze the nonlinear torsional behavior of single-box multi-cell prestressed concrete (PC) or reinforced concrete (RC) composite box-girders with corrugated steel webs (BGCSWs), a new theoretical model called unified softened membrane model for torsion (USMMT) is proposed in this study. It is developed from the softened membrane model for torsion which was formerly proposed for the torsional analysis of single-box single-cell PC/RC composite BGCSWs. This proposed model incorporates the different contributions of inner and outer corrugated steel webs (CSWs) in the multi-cell BGCSW to the torsional capacity by introducing a rational relationship of shear strains between inner CSWs and outer CSWs. The satisfactory accuracy of the proposed model is obtained when comparing with the experimental and the finite element analysis results, including the torque-twist curves and the smeared shear strains in concrete slabs and CSWs in the full-range torsional analysis. The comparison indicates that the proposed model is capable of predicting the overall torsional behavior of single-box multi-cell BGCSWs.

Torsional behavior ofI‐steel–concretecomposite beam considering the composite effects

AbstractTo investigate the mechanical behavior of composite beams under pure torsion, considering the torsional contribution of the steel beam flanges, we established finite element models of I‐steel–concrete composite beams. The nonlinear material constitutive relationship of concrete and steel was adopted in the model, and we validated the relationship by tests. Afterward, parametric analyses were carried out to study the main factors affecting the torsional performance of the composite beam. Our primary investigation focused on the composite effects and load sharing ratio of the steel beam and the concrete slab under pure torsion. We established the formulas for obtaining the maximum shear stresses in the concrete slab and the steel beam based on the composite effects and superposition principle. From these tests and our calculations, we proposed a model defining the torsional bearing capacity and the torsional stiffness of the I‐steel–concrete composite beam; thus, the torsional contribution of the concrete slab and the steel beam were a primary concern in this research. Bearing capacity formulas are also proposed herein and are comparable with those in the literature, demonstrating that our formulas, with simple forms, are highly reliable when predicting the torsional behavior of the composite beam.

Structural Weight and Stiffness Optimization of a Midibus Using the Reinforcement and Response Surface Optimization (RSO) Method in Static Condition

Midibuses are medium-sized buses widely used for transportation purposes in Asia and Africa. However, most midibuses are locally built and indirectly regulated through inspecting the end product (finished bus) during licensing for the public transport business in Ethiopia. Due to lack of engineering analysis and testing, low stiffness and overweight of midibus were compromised. This research was aimed at analyzing and optimizing the midibus structure using the reinforcement and response surface optimization (RSO) method for pure bending and torsion loading cases. Results show that the maximum deformation occurred at the roof section of the original structure during both loading cases. Furthermore, the reinforcement design was found by replacing the cross section and layouts of structural members and adding reinforcements for the most suitable location of the original structure. Response surface optimization with the multiobjective genetic algorithm (MOGA) method in ANSYS DesignXplorer was performed on the reinforced structure to maximize the bending and torsional stiffness with reduced weight. The bending stiffness of the reinforced and optimized structure increased by 41.65% (1911.4 N/m) and 10.02% (651.7 N/m), respectively. In addition, the torsional rigidity or stiffness of the bus structure was improved by 12.56% (173.31 Nm/deg) via reinforcement design. Moreover, the torsional stiffness of the optimized (RSO) model was increased by 3.29% (51.07 Nm/deg). Reinforcement design was effectively reduced by 5.23% of the structure’s weight. Moreover, the RSO method has also decreased the weight of the reinforced structure by 2.64%.

Verification of a Torsional Behaviour Prediction Model for Reinforced Recycled Aggregate Concrete Beams

This study shows the torsional conduct of aggregate streaming beams of reinforced concrete recycling. Pure torsion was perceived for 15 reinforced concrete beams containing recycled concrete aggregates. The beams were grouped into five lengths and cross-sectional groups. The study’s principal parameters were the various percentages of longitudinal steel reinforcement and the proportions of recycled aggregates. The beams were purely twisted until failure and investigated for torsional and crack behaviour. The findings show that the beams with maximum steel enhancement and standard aggregate exhibited maximum cracking power and ultimate torsional strength. Recycled aggregates increased the presence of splitting and the ultimate strength, and the effects of steel strengthening in recycled beams were apparent. In a second analysis, the whole torsional reaction of the beams was analytically predicted. A soft truss model was used and matched with test results for standard beams. A strong compromise was generally reached.

Dynamic modeling of rotating blades system based on transfer matrix method of multibody system

Due to the coupling between the stator and the blades, the vibration characteristics of rotating blades play an important role in the structural reliability of rotating machinery. The computational modeling challenge lies in achieving the coupling of the rotating bending-torsional blade with the stator. To perform rapid and accurate vibration characteristics analysis, the Transfer Matrix Method of Multibody System (MSTMM) is proposed to study the multibody dynamics models of single rotating beam and rotor-stator coupled system. The models are verified by comparison with finite element method (FEM) results. Using the beam model, rotating blades pure bending and torsion frequencies can be simply computed, these are the key parameters for establishing critical instability dynamic models, such as 2D aerofoil or blade flutter models. By computing the vibration characteristics with varying rotating speed, the influence of the blade rotation is illustrated. The computational results show that, the influence of rotation is greater on the frequencies associated with the bending rather than with the one of the torsion mode, hence the adjacent natural frequencies may intersect. At the veering point, the mode shape of bending-torsion coupling mode changes greatly, compared with that of other rotation speeds. In addition, asymmetric modes can be observed in the rotor-stator coupled model due to the coupling of elastic deformation and rigid body motion. The modeling process is simple and rapid, only assembling the transfer matrix of each element like building blocks. This proposed model can be applied to compute coupled/uncoupled bending-torsional frequencies of helicopter and wind turbine blades, and the results can provide useful guidance for the modeling of rotating machinery.

On the torsional and coupled torsion-tension/compression behavior of magnesium alloy solid rod: A crystal plasticity evaluation

Extensive attention has been paid to magnesium (Mg) alloys considering their potential as lightweight structural materials. However, it is still challenging to process and manufacture Mg materials that carry high strength and good ductility. This issue mainly arises from a lack of understanding toward the anisotropic mechanical behavior of Mg alloys in response to large deformation in a multiaxial stress state, which is unavoidably in existence under various material processing routes. In this regard, we seek to understand the torsional and coupled torsion-tension/compression behaviors of a magnesium alloy subject to large-strain deformation. The elastic viscoplastic self-consistent (EVPSC) model, which incorporates the twinning-detwinning (TDT) scheme and takes a torsion-specific finite element (TFE) approach, was employed to illuminate the inhomogeneous and multiaxial features of the torsional deformation in the AZ31 Mg alloy subjected to free/fixed-end torsion and coupled torsion-tension/compression. Experimental validation was conducted by characterizing the mechanical responses of the torsional specimens under the loading paths of free-end torsion and coupled torsion-tension. Our model successfully captures the Swift effect along with the shear texture, which is hardly predicted by conventional constitutive models. In addition, our model reveals that twinning is nearly equally active under free-/fixed-end torsion, while twinning under coupled torsion-tension and torsion-compression is promoted and suppressed, respectively. The comparison between the simple shear and pure torsion by simulation demonstrates that the significant bulk stress existing within the torsional rod is ascribed to the strong interaction between the cylindrical elements in the EVPSC model. As a final thought, we believe that the TFE-EVPSC-TDT model not only highlights the inhomogeneous and multiaxial features underlying the torsional and coupled torsion-tension/compression behaviors of the Mg alloy solid rod, but more significantly, can be used as a numerical tool for designing/tuning gradient twinning structures that may lead to optimized properties of Mg alloys.