Torsional Shear Stress Research Articles

Combined effect of compressing fresh concrete and curing regime on bonding performance of high strength repair mortar

High strength concrete (HSC) is highly appropriate for the retrofitting and rehabilitation of reinforced concrete structures due to its low permeability and high bonding strength. However, its low workability and sensitivity to curing conditions pose significant challenges for its implementation in such projects. This study introduces a novel technique to overcome the workability barrier of HSC while enhancing its bonding strength under various curing conditions. To achieve this, four different pressures (0, 0.87, 2.61, and 5.23 MPa) were applied to fresh high strength repair mortar (HSRM) and HSC for durations of 2, 4, and 8 h. Subsequently, different curing methods, including the wet sack method, steam curing method, and the use of curing compounds, were employed. The modulus of elasticity and compressive strength of HSC, in addition to bonding performance between substrate HSC and 28-day compressed HSRM, were evaluated using the “friction-transfer” and “twist-off” techniques, which are standard techniques for measuring the bonding strength of concrete both in the laboratory and in-situ. Also, to further assess the effect of curing regime and pressure on the microstructures of HSRM, SEM images of 28-day HSRM specimens were collected. The results indicated that increasing the pressure to 5.23 MPa and extending the duration to 8 h enhanced the ultimate torsional shear strength between HSRM and substrate HSC by an average of 174%. Additionally, the mechanical properties of HSC were considerably enhanced by applying 5.23 MPa pressure over 8 h. It is worth mentioning that the bonding strength between HSRM and substrate HSC without curing was highly affected by the duration of pressure application compared to the three investigated curing methods. The wet sack curing method was found to be the most effective for enhancing the degree of hydration and increasing the failure torsional shear stress of compressed HSRM specimens.

Effect of torsional shear stress on the deformation characteristics of clay under traffic load

The soft clay under the road ground will suffer cyclic torsional shear stress encountered traffic load in addition to axial stress, which will cause further deformation of clay. To investigate the effect of torsional shear stress on the cumulative axial strain of clay, a series of undrained tests under cardioid stress path were performed on K0 consolidated undisturbed samples by using a hollow cylinder apparatus (HCA). The effect of vertical cyclic stress ratio (VCSR) and shear stress ratio (η) on the deformation and degradation characteristics of clay was investigated. The results indicate that there is inconsistency between the strain path and stress path. The increase in η further accelerates the accumulation of axial strain, which resulted from the degradation of clay induced by torsional shear stress. Considering the VCSR and η, a calculation method of degradation index was developed. Furthermore, a cumulative axial strain prediction model of clay under the cardioid stress path was established considering the degradation. This model addresses the limitation of traditional prediction models by considering the impact of torsional shear stress on cumulative axial strain.

Calculation of Shear Stress in New-Type Composite Box Girder with Corrugated Steel Webs under Restrained Torsion

The objective of this paper is to outline a method for the systematic analysis and calculation of the constrained torsional shear stress in corrugated steel web composite box girders. Initially, leveraging Umansky’s secondary theory, the calculation formula for the constrained torsional shear stress within the composite girder is derived from the conditions of cross-sectional torque equilibrium and continuity in warping displacement. Subsequently, a torsion test is conducted using a scaled model of an actual girder. Finally, the constrained torsional shear stress of the corrugated steel web composite girder is examined based on theoretical analyses and the results of torsion testing. The influence of wing plate length and web thickness on the torsional shear stress of the composite girder is also investigated. The findings reveal a strong agreement between the experimental results obtained from model testing and the theoretical calculations. Notably, under torsional constraint, it is observed that the shear stress in the web is maximal and evenly distributed, followed by the bottom plate and then the top plate, with no discernible shear stress observed at the free end of the cantilever plate. Numerical analysis indicates that an increase in the relative width of the cantilever plate initially leads to an increase in shear stress for both the cantilever plate and roof plate, followed by a decrease until reaching a relative width value around 0.6, where the changes tend to stabilize. Moreover, an increase in web thickness results in a monotonic decrease in web shear stress. Additionally, the shear stress of the roof and bottom plate decreases initially before subsequently increasing.

Development of a heavy vehicle torque rod applying continuous fiber reinforced thermoplastic composite materials instead of forged steel material: Design, analysis and optimization

The torque rod is an important component of the suspension system that connects the axle to the chassis in heavy commercial vehicles. The main motivation of this study is the development of a torque rod made of (1) plus cross-section, (2) continuous carbon and glass fiber reinforced hybrid thermoplastic composites, which can replace a forged steel torque rod used in heavy vehicles, has superior mechanical properties, provides minimum cost and weight. This study aims to develop a torque rod before its production within the framework of integration with Computer Aided Design (CAD), Finite Element Analysis (FEA), and Multi-Criteria Decision Making (MCDM). In this study, the design data and the properties of the composite materials were chosen as control factors. The minimum displacement, the best mechanical properties such as tensile stress, compressive stress, torsional shear stress, maximum critical buckling load, and the minimum part weight minimum production cost per piece were selected as quality characteristics. As a result of the FEA study, considering the experimental set of the Taguchi Method L25 orthogonal array, the data on mechanical properties, weight, and production cost per piece were subjected to the MCDM process using the Entropy Weighted TOPSIS method. As a result of the MCDM study, a torque rod made of continuous fiber-reinforced thermoplastic composite material, instead of a torque rod produced by forged steel, had the highest mechanical properties produced, the weight of the torque rod can be reduced by 64.76%, and the production costs per piece can be reduced by 37.5%. This study’s findings have shown that the torque rod produced from continuous fiber-reinforced thermoplastic composite materials in a new geometry with a plus cross-section can be substituted for the torque rod produced by steel forging. Thus, it will contribute to reducing the fixed vehicle weight, especially in heavy commercial vehicles, reducing CO2 emissions, and increasing the range of the vehicles.

Investigating the long-term deformation behaviour and non-coaxiality of siliceous sand under traffic cyclic loading

Subgrades composed of siliceous sand are often subjected to traffic-induced cyclic loads. However, there is a knowledge gap regarding the long-term deformation behaviour and non-coaxiality of siliceous sand under high-cyclic traffic loading. This study addresses this issue by conducting a series of drained high-cyclic tests using a hollow cylinder apparatus to simulate an anisotropic heart-shaped stress path. The effects of cyclic stress ratio (ζ) and torsion-shear stress ratio (ηd) were carefully evaluated and interpreted. The results showed that an increase in ζ and ηd results in a higher axial cumulative strain and resilient modulus, along with increased susceptibility to volumetric contraction. The dilatancy d (dεvacc/dεqacc) characterizing overall deformation accumulation experienced a transformation of first stabilizing then declining. By contrast, the individual stress-dilatancy relations within loading and unloading stages exhibited an inward movement trend. Moreover, the development and influencing factors of non-coaxiality were meticulously analysed, revealing that while the number of loading cycles had a negligible effect on non-coaxiality behaviour, it was considerably influenced by stress levels. A significant increase in the range of non-coaxiality angle variation was observed at larger ζ and ηd values. This study provides insights for the construction and design of tunnel foundations and pavement engineering.

Cumulative deformation and non-coaxial characteristics of fiber and cement-modified iron tailings under the rotation of principal stress

In order to study the deformation characteristics of fiber and cement-modified iron tailings (FCIT) under traffic loads, the cumulative deformation, stress–strain paths, cyclic stiffness, and non-coaxial characteristics of FCIT under the coupling of different cyclic stress ratios (CSR) and torsional shear stress ratios (η) were analyzed by using a heart-shaped stress path. The results indicate that: 1) The cumulative strain and torsional shear strain of FCIT under the rotation of the principal stress vary with CSR and η. The established empirical formula for the cumulative strain can be used to calculate the cumulative deformation of FCIT under different principal stress rotations based on the results of cyclic triaxial tests. 2) The difference between shear stiffness and positive deviation stiffness is the inherent mechanism that induces the non-coaxial characteristics of FCIT, that is, shear stiffness is subjected to torsional shear stress more than positive deviation stiffness is subjected to axial stress. 3) The non-coaxial characteristics of FCIT gradually weaken with the increase of axial force and torsional shear force, while the non-coaxial angle between the direction of strain increment and the direction of stress decreases.

Redesign of a Failed Hoisting Shaft of a Vertical Transfer Device

The redesign of a failed hoisting shaft belonging to a 10 m stroke vertical transfer device (VTD) is presented. Firstly, the operation of the VTD is thoroughly analysed, the variation of loads and moments along the operating cycle is characterised, and transients such as emergency stop loads are calculated. The selection of safety factors and duty cycle factors was followed by the shaft sizing. After an initial rough sizing, the high-cycle fatigue (HCF) design for cyclic bending moments was performed, first considering constant torque and then considering cyclic torque. The number of bending and torsion cycles performed by the hoisting shaft over 10 years was shown to exceed 106, and an infinite life design is mandatory. The analyses showed that the initial shaft diameter was insufficient, thus justifying the failures observed before the present redesign. A classical fatigue model combining torsional shear stresses with bending stresses was used to take into account reversed torsional loading and ensure infinite fatigue life. This work highlights the need to thoroughly understand a machine’s operating cycle so that the wrong premises for fatigue design calculations are not assumed.

Experimental Study on the Axial Deformation Characteristics of Compacted Lanzhou Loess under Traffic Loads

It is beneficial to the sustainable development of expressway engineering to reuse excavated soil as roadbed filling material. There are a large number of filling projects using loess as a filling material in Northwest China. In this paper, the loess subgrade of an expressway in Lanzhou is taken as the research object, and a series of experimental studies are conducted using a hollow cylindrical torsion shear system to simulate the formation of a “heart-shaped” stress path and the principal stress rotation (PSR) under long-term traffic loads. The effects of the vertical cyclic dynamic stress ratio, torsion shear stress ratio, initial static shear stress, and intermediate principal stress coefficient on the axial plastic deformation and rebound deformation of compacted loess in Lanzhou were studied. The results show that the vertical cyclic stress ratio (VCSR) has a significant effect on the axial deformation of compacted loess in Lanzhou. When the VCSR is less than 0.6, all the axial strain curves develop stably with the number of cycles. With an increasing VCSR, the axial plastic deformation increases obviously, and the axial rebound deformation also increases. The vertical cyclic dynamic stress of the specimen is constant. Moreover, increasing the torsional shear stress ratio (that is, increasing the amplitude of cyclic shear stress) can greatly increase the development of axial deformation, but it has no effect on the rebound deformation curve. When the initial static shear stress exists in the specimen, the larger the initial static stress ratio (SSR) is, the larger the axial plastic deformation. The axial plastic deformation increases by approximately 33% for every 0.1 increase in the SSR. The rebound deformation of different SSRs fluctuates at the initial stage of cyclic loading, but the final stable rebound deformation is basically the same as that at the initial stage of cyclic loading. The intermediate principal stress coefficient has no effect on the development of axial strain, and the effect on axial rebound deformation is negligible. Finally, the calculation model of the axial plastic strain of Lanzhou compacted loess under traffic loads is obtained. The research results can provide a reference for the durability and settlement prediction in loess engineering.

Analytical review of design aspects of helical spring

The curvature correction factor is an important parameter for evaluating the stress of helical springs. A novel modelled curvature correction factor (KG) was proposed in terms of the shear correction factor (KS) and spring index (C). This factor (KC) falls between the Wahl and Bergstrasser correction factors, considering the stresses due to shear, torsional, and curvature effects. The ratio of the actual deflection to estimated deflection and the ratio of the actual stiffness to estimated stiffness are mirror images of each other. In addition, when C continued to decrease, the curvature correction factor increased sharply. In practical design, the actual deviation is greater than the evaluated deflection, and the evaluated deflection may need to be increased by a certain percentage to obtain the actual deflection. Therefore, a general equation was developed for this purpose. The ratios of the actual and evaluated deflections and the actual and evaluated stiffnesses were mirror images of each other. For suitable assumed data, the torsional shear stress, maximum shear stress, and modelled curvature stress were almost straight and parallel to each other.

Torsional and compressive properties of bolted joint under forward-reverse tightening

Obtaining the stress evolution law of bolted joint during the assembly process is of great significance for tightening process design and improving assembly performance. In this study, the bolt tightening analytical model is used to obtain the deformation coordination mechanism. Then, the evolution law of the stress during assembly process are obtained by FEA model, and the influence of different assembly parameters on the stress change is analyzed. Finally, the bolt tightening experiment is carried out, which verified the theoretical hypothesis and the FEA model. The results show that: in addition to the tensile normal stress, the thread torque also generates torsional shear stress that causes the torsional deformation of the screw during the tightening process. The torsional shear stress can be reduced by forward-reverse tightening process. Meanwhile, the utilization rate of bolted joint can be improved. This can increase the assembly design margin and improve the assembly performance.

Assessment of torsional behavior of bone section using meshfree method based on TPS radial basis function

The torsional study of bone cross-sections consisting of porous and functionally graded material (FGM) is presented in this paper. The modeling of the bone can be thought of as an FGM. For the modeling of FGM material, a classical power law is used. The strength of the bone is reduced when the microstructure of the bone changes with age. Saint-Venant torsion theory is used to formulate the governing equation. Thin plate spline (TPS) radial basis function-based collocation meshfree method is used for discretization and solution of the governing differential equations. The discretized partial differential equations are solved using MATLAB programming. To assess the effectiveness and accuracy of the current TPS-based meshfree approach, numerical examples for circular and hollow circular sections were used to conduct a convergence and validation test. Finally, the torsional rigidity and shear stress of the FGM and porous bone sections are estimated using an actual cross-section of the bone. After conducting a convergence study, a method is developed to produce fresh findings for the actual bone shape section.

Experimental Investigation on the Deformation and Noncoaxial Characteristics of Fiber-Reinforced Aeolian Soil under Traffic Load

The cumulative plastic deformation of a foundation associated with traffic loading causes subgrade instability, and eventually, failure of retaining structures. In the present study, hollow torsional shear tests were conducted on fiber-reinforced aeolian soil involving varying fiber contents, cyclic deviator stresses, cyclic shear stresses, and consolidation confining pressures using the Small-Strain Hollow Cylinder Apparatus, developed by GDS Instruments Ltd. (GDS SS-HCA). This enabled an investigation of the deformation characteristics and noncoaxial angle changes of fiber-reinforced aeolian soil under a heart-shaped stress path. The results indicate that fiber-reinforced soil deformation under cyclic loading involves axial (ɛz), radial (ɛr), circumferential (ɛθ), and shear (γzθ) strains, and deformation increases with increasing the cyclic number. The strain increases rapidly during the first 200 cycles and then gradually. The axial deformation decreases with increasing fiber content when the fiber content is less than 2‰ and increases when the content is more than 2‰. The plastic strain and total deformation decrease with increasing confining pressure but increase as the cyclic dynamic stress and cyclic shear stress amplitudes increase. Functional equations of the cumulative axial plastic strain and vibration numbers are proposed. The relationships between the model parameters, including the fiber content and cyclic torsional shear stress, are analyzed. The principal stress axis rotation causes variations between the major principal strain increment and the principal stress directions, representing the noncoaxial angle (β). The noncoaxial angle fluctuates during each loading cycle, exhibiting a V shape, for principal stress axis angles (ασ) from −90° to −45° and −45° to 30°, and decreasing at angles varying from 30° to 90°, with a maximum noncoaxial angle of approximately 30° per cycle.

Effect of Ultrasonic Vibration on the Surface Adhesive Characteristic of Iced Aluminum Alloy Plate

Icings on moving machinery, such as wind turbines and aircraft wings, degrade their performance and safety. Ultrasonic vibration is considered one of the deicing methods. In this research, simulations and experiments are carried out to explore the effect of ultrasonic vibration on the adhesive characteristic of ice on aluminum alloy plates. Harmonic response analyses are conducted to analyze the changing and distributions of shear stresses at the adhesive interface under different frequencies and sizes of PZT patches. The results show that there is optimum side length and thickness of the PZT patch, as the size of the iced aluminum alloy plate is constant. In these conditions, the shear stresses at the adhesive interface are high. Then, experiments on adhesive torque of ice are carried out to calculate the adhesive shear stresses of ice. The results show that the adhesive force of ice decreases under the excitation of ultrasonic vibration. When the excited frequency is 79 kHz, the adhesive torsional shear stress is 0.014 MPa, which is only 7% of the one with no ultrasonic vibration.

Planar Chirality and Optical Spin-Orbit Coupling for Chiral Fabry-Perot Cavities.

We design, in a most simple way, Fabry–Perot cavities with longitudinal chiral modes by sandwiching between two smooth metallic silver mirrors a layer of polystyrene made planar chiral by torsional shear stress. We demonstrate that the helicity-preserving features of our cavities stem from a spin–orbit coupling mechanism seeded inside the cavities by the specific chiroptical features of planar chirality. Planar chirality gives rise to an extrinsic source of three-dimensional chirality under oblique illumination that endows the cavities with enantiomorphic signatures measured experimentally and simulated with excellent agreement. The simplicity of our scheme is particularly promising in the context of chiral cavity QED and polaritonic asymmetric chemistry.

Mechanical Behaviour and Failure Mode of High Interstitially Alloyed Austenite under Combined Compression and Cyclic Torsion

Multiaxial stress states frequently occur in technical components and, due to the multitude of possible load situations and variations in behaviour of different materials, are to date not fully predictable. This is particularly the case when loads lie in the plastic range, when strain accumulation, hardening and softening play a decisive role for the material reaction. This study therefore aims at adding to the understanding of material behaviour under complex load conditions. Fatigue tests conducted under cyclic torsional angles (5°, 7.5°, 10° and 15°), with superimposed axial static compression loads (250 MPa and 350 MPa), were carried out using smooth specimens at room temperature. A high nitrogen alloyed austenitic stainless steel (nickel free), was employed to determine not only the number of cycles to failure but particularly to aid in the understanding of the mechanical material reaction to the multiaxial stresses as well as modes of crack formation and growth. Experimental test results indicate that strain hardening occurs under the compressive strain, while at the same time cyclic softening is observable in the torsional shear stresses. Furthermore, the cracks’ nature is unusual with multiple branching and presence of cracks perpendicular in direction to the surface cracks, indicative of the varying multiaxial stress states across the samples’ cross section as cross slip is activated in different directions. In addition, it is believed that the static compressive stress facilitated the Stage I (mode II) crack to change direction from the axial direction to a plane perpendicular to the specimen’s axis.

Enhancement of plastic flow in lateral direction by torsional oscillation in upsetting and lateral extrusion

Plastic flow of hollow cylinders under combining axial compression with torsion was examined in upsetting and in lateral extrusion. The hollow cylinders with initial height/outer diameter of 0.5–2.5 and initial inner/outer diameter of 0.3–0.9 were compressed/extruded and simultaneously twisted with respect to the axisymmetric forging axis in one-way or cyclic alternating. Due to superposition of torsional shear stress, the lateral metal flow was found to be assisted. Barreling of the workpiece was reduced by approximately 10 % in upsetting with torsion/compression speed of 6 °/mm. The enhancement of the plastic flow in upsetting was applied to fill up tooth cavity in lateral extrusion. The extruded tooth depth of the workpiece was approximately 5–7% larger in lateral extrusion with torsion/extrusion speed of 30°/mm. In addition, cyclic alternating torsion was effective to extrude evenly in the tooth thickness direction due to the periodic reversal of die rotation in peripheral direction.

Meshfree Approach for the Torsional Analysis of Non-Circular Orthotropic and Functionally Graded Sections

This paper presents the torsional analysis of isotropic, orthotropic, and functionally graded material (FGM) triangular and rectangular sections. The formulation of the governing equation of the torsion problem is done using the Saint–Venant torsion theory. Classical power law has been considered for the modeling of FGM material. A meshfree technique based on various radial basis functions is used for the solution of the governing differential equation. MATLAB code is developed to solve the discretized partial differential equations. To demonstrate the effectiveness and accuracy of this technique, convergence study and numerical examples are presented by varying the various parameters. The torsional rigidity factors and shear stress factors are obtained for different new conditions. The solution presented here is validated from the analytical and numerical results along with some new results, which shows the satisfactory performance of the present method.

Application of radial basis function-based meshless method for torsional analysis of elliptical and bone shaped-irregular sections

This article presents a torsional analysis of solid elliptical, hollow circular, and actual bone sections of orthotropic and functionally graded material. The formulation of the governing equation is done using the Saint-Venant torsion theory. A classical power law is considered for the modelling of functionally graded material. Five different radial basis functions-based meshless methods are used for the discretization of the governing differential equations. MATLAB code is developed to solve the discretized partial differential equations. A convergence and validation study has been carried out to demonstrate the effectiveness and accuracy of the present method. Numerical examples for torsional rigidity and shear stresses are presented for circular, elliptical, and bone-shaped irregular sections made up of orthotropic and functionally graded materials. Finally, the proposed radial basis function-based meshless method is applied to the modelling and torsional analysis of an actual bone cross-section.

Numerical Study on Vibration Response and Fatigue Damage of Axial Compressor Blade Considering Aerodynamic Excitation

Axial compressor blades with a deformed initial torsion angle caused by aerodynamic excitation resonated at the working speed and changed the rule of fatigue damage accumulation. The fatigue life of a blade has a prediction error, even causing serious flight accidents if the effect of torque causing damage deterioration of the blade fatigue life is neglected. Therefore, in this paper, a uniaxial non-linear fatigue damage model was modified using the equivalent stress with torsional shear stress, and the proposed fatigue model including the torsional moment was used to study the compressor blade fatigue life. Then, the blade numerical simulation model was established to calculate the vibration characteristics under complex loads of airflow excitation and a rotating centrifugal force. Finally, the blade fatigue life under actual working conditions was predicted using the modified fatigue model. The results show that the interaction between centrifugal and aerodynamic loads affects the natural frequency, as the frequencies in modes dominated by bending deformation decreased whereas those dominated by torsional deformation increased. Furthermore, the blade root of the suction surface showed stress concentration, but there is an obvious difference of stress distribution and amplitude between the normal stress and the equivalent stress including torsional shear stress. The additional consideration of the torsional shear stress decreased the predicted fatigue life by 4.5%. The damage accumulation rate changes with the loading cycle, and it accelerates fast for the last 25% of the cycle, when the blade fracture may occur at any time. Thus, the aerodynamic excitation increased the safety factor of blade fatigue life prediction.

Qualification of NSTX-U Inner TF Bundle Using Hi-Fidelity Models

The National Spherical Torus eXperiment Upgrade (NSTX-U) Recovery Project provides a national facility for the study of plasma confinement, heating, and current drive in a low-aspect-ratio, spherical torus configuration. For the NSTX-U Recovery Project, key system capabilities must be achieved in order to meet operational goals. The inner toroidal field (TF) bundle is part of the center stack with 36 pie-shaped wedges (TF inner legs) bonded into a cylindrical bundle. The inner bundle is connected to outer legs via flex straps, and an ohmic heating (OH) coil is wound around the inner TF bundle, with a layer of aquapour in between acting as a winding surface between TF-OH coils. The TF bundle for the Recovery Project underwent two expert reviews to gain an improved understanding of issues identified from the extent of condition and the magnet design verification and validation review; this was to ensure confidence in the ability of the TF-OH center stack assembly to meet physics requirements for operations. A hi-fidelity, finite element model was developed with appropriate detail for multiphysics analysis of the bundle and to provide a baseline model to use as a standard against which the allowable stresses were compared. The model was also used to understand mechanical behavior and to assess implications of hypothetical delamination to the machine operation. Normal tensile stress at the bundle stub was the result of a nonuniform resistive current distribution where a relatively cold region was formed when the TF coil was pulsed. The worst case occurred at the end of the pulse when the maximum temperature gradient was established at the bundle ends. The hot spot was in compression, and the cold region was in tension. The compressive stress, which had a maximum at the bundle stub, enhanced the insulation shear capability. The in-plane torsional shear stress peaked at the end corner of the inner leg outer diameter at end of flat top. The insulation tensile and shear stresses were extracted from the hi-fidelity model using orthotropic material properties derived from first principles, and these theoretical data were verified via material tests. Load path probes were used to quantify the redistribution of torsional loads between the bundle and the external load path for a hypothetical extreme delamination condition. The extent of possible delamination was limited to regions within the radius of the flex straps. There is no significant effect on the bundle inner leg copper stress. The differential movement between the flex straps in the hypothetical extreme delamination condition is far less than the toroidal gaps between them, so there is no risk of closing these electrical gaps between the bundle turns. There is thus no impact on machine operation or even hypothetical delamination to an extreme delamination beyond the simulation-predicted delamination boundary.