Torsional Deformation Research Articles

FINITE SHEAR STRAIN BASED ON IMAGE ANALYSIS FOR RECTANGULAR SECTION SHAFT WITH LARGE ASPECT RATIO

This paper describes the shearing strain distribution obtained by using image analysis proposed in this study when large torsion is applied to a rectangular cross-section shaft. As is well known, the shearing strain distribution for rectangular cross-section shaft have already been investigated by Saint-Venant. However, since this theory is based on the assumption that torsional angle is relatively small, it is not necessarily rational under large torsion. Therefore, in our previous study, using the image analysis based on the Natural Strain theory, where the commutative law of strain is applicable and the rigid body rotation can be removed accurately from shearing strain component, the shearing strain distributions have been investigated for the rubber shaft having square cross section. In the present paper, these distributions are investigated for a rectangular cross section with a large aspect ratio rather than a square shape. In particular, these distributions on the long side in rectangular cross-section are compared with those on the short sides. Consequently, the difference between the distribution of shearing strain obtained by the image analysis in this study and measurements based on Saint-Venant's theory increases as torsional deformation increases and this tendency is observed particularly on the short side.

Influence of the Temperature of High Pressure Torsion Deformation on the Recrystallization Kinetics of Iron with a Submicrocrystalline Structure

Influence of the Temperature of High Pressure Torsion Deformation on the Recrystallization Kinetics of Iron with a Submicrocrystalline Structure

Torsional Deformity Significantly Impacts Lateral Ankle Radiographic Imaging Parameters.

Background Optimal lateral ankle imaging is important for the diagnosis and treatment of multiple ankle conditions. The effects of limb deformity on lateral ankle imaging are not well described and are clarified in this osteological study. Materials and methods We utilized an osteological collection and imaged all specimens after the first positioning of the talus in the lateral position and positioning the tibia and fibula to match. We then measured the relative positions of the tibia and fibula and their widths to calculate standard ratios. All measurements were evaluated for reliability using intra-class correlation coefficients. Multiple regression analysis determined how patient characteristics, tibial torsion, and medial proximal tibial angle affected various lateral ankle imaging ratios. Results The intra-class correlation coefficient was excellent for all measurements. In the multiple regression analysis, all five imaging ratios had at least one statistically significant outcome. The anterior tibiofibular interval (ATFI)-tibial width (TW) ratio (ATFI:TW) had only one association with sex and had the lowest standard deviation. All other parameters had variation with tibial torsion and/or medial proximal tibia angle (MPTA). The mean ATFI was 1.06 ± 0.21 cm and 1.19 ± 0.23 cm for females and males, respectively. Conclusions Patient sex and tibial torsion impacted the fidelity of lateral imaging parameters. ATFI:TW may pose the greatest utility given its minimal association with deformity parameters and low standard deviation.

Theoretical study on the effect of torsional deformation on WTe2 as a cathode material for calcium ion batteries.

In this study, the electronic structure and diffusion barrier of the Ca-adsorbed WTe2 system under different torsion angles were calculated based on the first-principles method. The results show that the structure and properties of the pure WTe2 system and Ca-adsorbed WTe2 system are affected by torsional deformation. When the torsion angle is 6°, the intrinsic WTe2 changes from a direct band gap to an indirect band gap. The torsional deformation does not change the metallicity of the Ca-adsorbed WTe2 system. The Ca-d state electrons contribute to the electron density of WTe2. The calculation of the diffusion barrier shows that the torsion deformation promotes the diffusion of calcium on the surface of WTe2. This study provides a theoretical basis for the regulation of electrode materials. In this study, Materials Studio 8.0 software was used to construct the WTe2 model and Ca-adsorbed WTe2 model, and CASTEP module was used for first-principles calculation.

Modeling and contact analysis for spur gear pair with modification and localized crack failure

The modified teeth are deliberately manufactured to mitigate the stress concentration generated by offset components, which makes equipment more susceptible to localized failures. Therefore, this paper presents a model aimed at investigating the meshing characteristic of gear pair with modification and crack failure. In this model, the tooth deformation and force transmission are determined based on slice coupling theory. The torsional deformation of teeth produced by eccentric load distribution is considered and complemented to the calculation method. Finally, the approach is proven through the experimental tests and FE model. The result shows that when the equipment is operated in misalignment condition, eccentric load distribution, and stress concentration at tooth edge are generated, the meshing stiffness will be reduced drastically, which can be suppressed by appropriate modification, and the rapid decline of meshing stiffness is weakened by increasing the effective contact length. Although the contact stiffness would be further reduced by the crack failure and the tooth surface deformation is increased, it seems to alleviate the stress concentration and eccentric load effectively.

Hip Joint Stability during and after Femoral Lengthening in Congenital Femoral Deficiency.

Hip stability remains a major preoccupation during femoral lengthening in Congenital Femoral Deficiency (CFD). We aimed to review hip stability in Paley type 1a CFD patients undergoing femoral lengthening. A total of 33 patients with unilateral CFD, who were treated between 2014 and 2023, were retrospectively reviewed. In 20/33 cases (60.6%) the SUPERhip preparatory surgery was performed at a mean age of 4.3 years (range 2.7-8.1). The femoral lengthening using an external fixator was performed at a mean age of 7.8 years (range 4.3-14.3). All patients presented with a stable hip joint after preparatory surgery and during femoral lengthening. Six cases of hip instability at a mean of 637 days after the external fixator removal were observed (range 127 to 1447 days). No significant differences between stable and unstable hips were noted for (1) Center-Edge Angle: 23.7 vs. 26.1 deg; (2) Acetabular Inclination: 12.8 vs. 11.7 deg; and (3) Ex-Fix Index: 35.6 days/cm vs. 42.4 days/cm; p > 0.05. Late hip instability was related to Coxa Vara and decreased femoral antetorsion before lengthening. Late hip joint instability in Paley type 1a CFD patients may occur long after femoral lengthening despite hip morphology appearing to be normal on radiograms before and at the end of femoral lengthening. Coxa Vara, femoral torsional deformity, and posterior acetabular deficiency might be risk factors for hip instability.

Rotational Stiffening Performance of Roof Folded Plates in Torsion Tests and the Stiffening Effect of Roof Folded Plates on the Lateral Buckling of H Beams in Steel Structures

Non-structural members, such as roofs and ceilings, become affixed to main beams that are known as structural members. When such main beams experience bending or compressive forces that lead to lateral buckling, non-structural members may act to restrain the resulting lateral buckling deformation. Nevertheless, neither Japanese nor European guidelines advocate for the utilization of non-structural members as lateral buckling stiffeners for beams. Additionally, local buckling ensues near the bolt apertures in the beam–roof folded plate connection due to the torsional deformation induced by the lateral buckling of the H beam, thereby reducing the rotational stiffness of the roof folded plate to a percentage of its ideal stiffness. This paper conducts torsional experiments on roof folded plates, and with various connection methods between these plates and the beams, to comprehend the deformation mechanism of roof folded plates and the relationship between their rotational stiffness and the torsional moment. Then, the relationship between the demand values against restraining the lateral buckling of the main beam and the experimentally determined bearing capacity of the roof folded plate is elucidated. Results indicate the efficacy of utilizing the roof folded plate as a continuous brace. The lateral buckling design capacity of H beams that are continuously stiffened by roof folded plates is elucidated via application of a connection method that ensures joint stiffness between the roof folded plate and the beam while using Japanese and European design codes.

Mathematical model for mesh analysis of gear pair in gear-shaft-bearing systems with localized failure on raceway

To investigate the influence of bearing failures on the mesh characteristics of gear pairs, this paper presents a mathematical model for gear-shaft-bearing systems. Within this simulation method, the model of defective bearings and the contact analysis methodology of gear pairs are integrated into the system equations. Additionally, the coupling mechanism between system components is determined by addressing the misaligned shafts induced by asynchronous bearing vibrations. Furthermore, the torsional deformation of gear teeth generated by uneven load distribution is considered, and a calculation method for mesh stiffness in complex environments is developed. By employing the comprehensive model, the effect of raceway failures on the mesh behavior is lucidly explained, the real-time distribution of contact stress and load on the tooth surface can be obtained, and the optimal modification strategies for gears are formulated. Finally, the proposed model is confirmed through the finite element (FE) model and experimental observation, which provides a potent tool for the performance optimization of gearboxes.

Modeling of flexible shaft for robotics applications

Reducing moving mass and effective inertia is essential for achieving safe human–robot collaboration. This can be achieved either by employing remote actuation, which moves the mass of actuators away from the moving elements of the robot, or by elastic actuation, which decouples the inertia of the actuator from the inertia of the robot’s link. Flexible shafts, being torsionally compliant slender long shafts, offer a combination of remote and series elastic actuation over an obstacle. Modeling such transmission is complicated due to its three-dimensional deformation in torsion, bending, and helical buckling. This paper proposes an algorithm for estimating the polar moment of inertia and stiffness of the flexible shafts using their physical dimensions of length and diameter. Using an inertia-spring–damper model, the stiffness parameters are estimated experimentally for nine flexible shafts with variable diameters and lengths in straight and bent configurations. The proposed algorithm is validated with experimental stiffness values for variable diameters and lengths in straight configuration. For bent configuration, an empirical formulation is provided to incorporate the bending deformation effect till a bending angle of 45∘.

Исследование усталостных свойств и трибологические испытания стали AISI 316 после кручения под высоким давлением

The effect of high-pressure torsion process in a new die on the fatigue properties of corrosion-resistant steel AISI 316 has been studied. The deformation was carried out at cryogenic and room temperatures. The number of deformation cycles was 8. The initial blank had a ring shape with a diameter of 76 mm, a width of 3.5 mm and a thickness of 3 mm. It is revealed that the fatigue strength of both samples increases due to structure refinement and twinning in austenite during high pressure torsion deformation, partial martensitic transformation and increase of the share of more angular boundaries during cyclic deformation. The main factor of higher fatigue limit of AISI 316 steel after cryogenic deformation in comparison with room temperature is more intensive grinding of microstructure and presence of increased share of large-angle boundaries and more complete martensitic transformation.

A Comprehensive Investigation of Linear and Nonlinear Beam Models on Flexible Wind Turbine Blade Load Calculations

This study was performed to investigate the effects of structural nonlinearity and large deformations on the aeroelastic loads of flexible wind turbine blades. First, a blade structural analysis model was established using the geometrically exact beam (GEB) theory. Subsequently, the blade element momentum (BEM) theory was corrected using the geometrically exact method leading to the development of a geometrically exact blade element momentum (GE-BEM) model. The results from the GE-BEM model indicated that flapwise deformations always reduce blade fatigue loads, while torsional deformations decrease fatigue loads under low wind speeds but increase them under high wind speeds. Finally, the linear Euler–Bernoulli beam and the GEB were compared to explore the influence of geometric nonlinearity on the blade aeroelastic loads, which revealed that the Euler beam model underestimates the blade loads. The simulations that used the GEB model produced torsional root twist fatigue loads that were 57.49% greater than those generated when the Euler beam model was used. Furthermore, the flapwise bending moment fatigue loads at the root were 8.24% greater than those obtained by the Euler beam model. The smallest discrepancy between the results of the two models was 7.26%, and it corresponded to the edgewise fatigue load.

The application of a dual-lead locking screw could enhance the reduction and fixation stability of the proximal humerus fractures: a biomechanical evaluation.

Bicortical screw fixation, which penetrates and fixes the near and far cortex of bone, has been conventionally used to achieve compressive fixation for fracture using screws. Open reduction and internal fixation using the locking plate are widely used for treating proximal humerus fractures. However, minimal contact between the bone and the locking plate can lead to an insufficient reduction. Theoretically, a dual-lead locking screw with different leads for the screw head and body could enhance the reduction and fixation stability of fragments in proximal humeral fractures without bicortical fixation, and achieve additional compression at the bone-plate-screw interface. This study assessed the insertion mechanics of the lead ratio of the dual-lead locking screw and its effect on the fixation stability of the proximal humerus fracture. A Multi-Fix® locking plating system composed of 3.5 mm locking screws and a locking plate was used to make a locked plating for Sawbone bone blocks and fourth-generation composite humeri. Two different types of Sawbone bone blocks were used to simulate the osteoporotic (10 PCF) and normal cancellous (20 PCF) bones. The lead of the screw head thread () was 0.8 mm, and that of the screw body () was 0.8, 1.25, 1.6, 2.0, and 2.4 mm, whose lead ratios () were 1.0, 1.56, 2.0, 2.5, and 3.0, respectively. The dual-lead locking screw elevated the compression between the locking plate and the bone. The elevation in the compression due to the dual-lead thread became weaker for the cancellous bone when the lead of the screw body was more than twice that of the screw head. The plate/humerus compression with strong bone quality withstood higher dual-lead-driven compression. A dual-lead locking screw of () is recommended for maximum rotational stability for the locked humerus plating. The screws with over () have no advantage in terms of the failure torque and maximum torsional deformation. Any locking dual-lead screw with a body thread lead of <1.6 mm () can be used without the risk of bone crush when surgeons require additional compression to the locked cancellous bone plating.

Radiological diagnostics of patellofemoral instability and patellar dislocation

Patellofemoral instability (PFI) describes a(sub)luxation of the patella in the patellofemoral joint. Pathophysiologically, PFI is usually due to a nonphysiological movement of the patella, so-called maltracking, either due to acute trauma with injury to the supporting ligamentous apparatus or due to the presence of anatomical risk factors. Radiologically assessable risk factors for maltracking include trochlear dysplasia, patella alta, patellar tilt, lateralization of the tibial tuberosity, torsional deformity and genu valgum. This article presents the most commonly used and best validated measurement techniques. In addition, the characteristic injury pattern after lateral patellar dislocation is shown.

Analyzing the structural behavior of conducting polymer actuators and its interdependence with the electrochemical phenomenon

This work reports the deformation behavior of a conducting polymer, poly(3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS)/bacterial cellulose (BC) bi-layered cantilever type actuator. Herein, it was found that the type (i.e. bending and torsion) of deformation of (PEDOT:PSS)/BC actuator was non-trivially dependent on its dimensions (width and length). Increasing the actuator’s width resulted in larger torsional deformation along the longitudinal axis against the increased area moment of inertia. The actuator with a width of 7.75 mm rotates ∼90° (i.e. the bottom cross-section) with respect to its top end. It was noticed that torsional motion dominated the deformation when the bending in the lateral direction was restricted. Further, the maximum tip displacement trivially increased with the length from 5.40 mm for an actuator of length 10 mm–12.40 mm for a length of 59.00 mm. However, the curvature of bending, which was proportional to the induced strain, was higher for smaller lengths. The change in the dimension of the actuator involves change in the stress field distribution (i.e. induced through electrochemical process) and simultaneously the resistance to deformation, resulting in a non-trivial relationship between the deformation and the dimensions. This can be advantageous from the design perspective in realizing different types of motions without incorporating additional materials. Structural theory and electrochemical impedance Spectroscopy were used to understand the mechanism of deformation dependence on the dimensions. The electrochemical impedance spectroscopy results indicated that electrolytic ions penetrate deeper into the PEDOT:PSS layer for actuators of smaller lengths. The increase in the curvature of the actuator could be explained based on the constancy of the strain produced due to the volume change per ion. The torsional motion increased because the stresses were being induced further away from the center in wider actuators. These observations and analyses reveal the interdependence of the structural behavior (i.e. dimensions) and the electrochemical phenomenon (i.e. deformation) in a conducting polymer actuator.

Deformation mechanism and hardening behavior of gradient heterostructured magnesium alloys prepared by severe shear deformation

Lightweight equipment in aerospace and other fields urgently requires magnesium (Mg) alloys components with high-strength plasticity. For this reason, in this study, a gradient heterogeneous structure containing nanocrystallines was constructed successfully using a severe shear deformation process that combines severe plastic deformation techniques and torsional deformation characteristics. The evolution of the microstructure and hardness of Mg-12.12Gd-4.2Y-2.28Zn-0.36Zr (wt%) alloys prepared by severe shear deformation with changes in deformation temperature were investigated. The gradient heterogeneous structure of the alloys formed naturally under high hydrostatic pressure and severe shear stress, and its thickness increased with the deformation temperature. With the application of shear stress, a large amount of rotational dynamic recrystallization (RDRX) behavior occurs in the alloys, refining the coarse initial grains (∼126.3 µm) into fine grains (∼2.03 µm) or even ultrafine grains (∼1 µm). During the RDRX process, low angle grain boundaries (LAGBs) began to form at high distorted grain boundaries and unique lamellar structures, followed by a rapid expansion into the interior of the grains, which ultimately results in the grains being completely covered by subgrains. Meanwhile, the continuously broken long-period stacking-ordered (LPSO) phase and the precipitated bright rare earth rich (RE-rich) phase provide a large number of nucleation sites, further promoting the refinement process of the grains. Subsequently, the grains were further refined to nanocrystallines through the formation and rotation of subgrains under continuous loading of stress. The massive formation of nano-precipitated phases (β phases) along grain boundaries were accompanied by the complete disappearance of other types of second phases. The sources of β phases formation include the layer-by-layer decomposition of the cellular phases and the dissolution/re-precipitation of the LPSO phases. In addition, the introduction of shear stress promotes the random orientation of the DRXed grains through the extensive activation of pyramidal <a> and pyramidal <c+a> slip. The hardness of the alloys gradually decreased as the cumulative strain decreased at different deformation temperature conditions. When the deformation temperature was 440°C, the alloys reached a maximum hardness of 127.67 HV, which was nearly 43.5% higher than homogenized alloys. The ultra-high hardness of the alloys prepared by severe shear deformation is mainly attributed to grain boundary hardening, diffusion hardening and hetero-deformation induced (HDI) hardening.

The Test Study on Tension-torsion Coupling Effect of ACSR in Overhead Transmission Lines

In order to analyze the relationship between the tensile and torsional characteristics of the Aluminum Conductor Steel Reinforced (ACSR), test research on the coupling effect of tension and torsion in conductors was carried out. A conductor tension-torsion coupling test device was designed, and selected the JL/G1A-630/45-45/7 ACSR as sample which is commonly used in ultra-high voltage AC engineering. The relationship between conductor tension, torque, and tensile strain, torsional strain was measured. And obtain the stiffness coefficients of conductor tension, torsion, and tension-torsion coupling. The testing results show that the tension and torque of the conductor gradually change from non-linear to linear under the action of tension or torsion deformation; The torsional stiffness Kφφ and tension-torsion coupling stiffness Kεφ when the conductor is turned to the right are greater than the corresponding stiffness when it is turned to the left.

Comparison study of mechanical characteristics between conventional shield tunnel and shield tunnel with mortise-groove cross-section in ground fissure site

ABSTRACT Under the condition of the shield tunnel intersecting the ground fissure section at a right angle, a physical model test was conducted at a geometric scale ratio of 1:30. This test aimed to compare and analyze the force and deformation of the conventional shield tunnel and shield tunnel after adopting measures to mitigate the effects of ground fissure dislocation. Meanwhile, a finite-element numerical simulation of a conventional shield tunnel under the same working conditions was performed. The physical model test results align closely with the outcomes predicted by numerical calculations. The deformation observed in the shield tunnel primarily consisted of vertical shear deformation near the ground fissure, accompanied by a minor torsional deformation. In grade IV ground fissure sites, both the conventional shield tunnel and shield tunnel with mortise-groove cross-section after taking measures exhibit a basic level of safety. However, only the shield tunnel, after taking measures, is safe when the ground fissure develops to grade III. By contrast, the conventional shield tunnel generates significant shear deformation at the first circumferential seam in the footwall of the ground fissure, which easily causes the joints inside the circumferential seam to yield shear. When the ground fissure grade was raised to II, the conventional shield tunnel and shield tunnel with mortise-groove cross-section after taking measures experienced relatively serious damage.

Deformation characteristics of existing tunnels induced by above-crossing quasi-rectangular shield tunnel

Quasi-rectangular shield (QRS) tunneling, a recent development in tunneling technology, offers the advantage of creating double tunnels with a single excavation. This technology causes significantly less secondary damage to the environment than traditional double shield tunneling. However, the deformation characteristics of existing tunnels caused by the QRS tunnel crossing above them are unknown. This study presents the first application of a QRS tunnel crossing above existing tunnels. It provides a comprehensive overview of the vertical displacement, horizontal displacement, segment convergence, and torsional deformation of existing tunnels when the QRS crosses above and runs parallel to the existing tunnels in the Hangzhou Metro Line 4. The measurement results indicate that the existing tunnels exhibit a maximum vertical displacement of 7.2 mm, maximum horizontal displacement of 2.3 mm, maximum segment convergence of 5.8 mm, and rotation index of up to ±10 × 10-4 at the intersection of the QRS and existing tunnels. All of the measurement results fall within the acceptable range, demonstrating the exceptional efficacy of QRS in controlling the deformations of existing tunnels. The effects of the plane position and distance between the tunnels on the deformation of the existing tunnels is also discussed. The deformation of the existing tunnels is negligible when the distance between the QRS and existing tunnels exceeds 16 m. The maximum vertical displacement, horizontal displacement, segment convergence, and zero-values of the rotation index occur at approximately 5 m in the plane position rather than at the intersection between the QRS and existing tunnels. The primary influence zone where the QRS tunnel crosses above existing tunnels is discussed.

Biomechanical stresses in a residually stressed idealized intervertebral disc

Intervertebral discs are soft biological tissues that have an important function in accommodating the movement of the spine during which the discs deform and act as shock absorbers to protect the spine from damage. Therefore, it is important to understand and model their mechanical properties to predict their response under various loading conditions. Towards this end, a simplified geometry of a single intervertebral disc, consisting of the nucleus pulposus within the anulus fibrosus, is modelled as a nonlinearly elastic solid. Pre-existing residual stresses in the unloaded state are taken into account in the radial and circumferential directions. In particular, the nucleus pulposus is considered to be isotropic, which becomes anisotropic with residual stress, while the anulus fibrosus consists of fibre families described by two standard reinforcing anisotropic models. The stress components associated with compressive and torsional deformations are determined analytically and illustrated for a simple constitutive model.

Multi-segment osteotomy with interlocking intramedullary nail fixation in the treatment of lower limb deformity in older children with hypophosphatemic rickets.

Malformations of the lower limbs caused by hypophosphatemic rickets in older children are mostly complex, occurring on multiple planes without a single apex and showing arcuate bending of the diaphysis combined with torsion deformity, and are difficult to correct. This study retrospectively investigated the effect of and indicators for multi-segment osteotomy with interlocking intramedullary nail fixation in the treatment of bony deformity caused by hypophosphatemic rickets. The clinical data of 21 hypophosphatemic rickets patients seen between August 2007 and March 2022 were collected. The age range of the patients at the first surgery was 11 years and 1 month old to 15 years and 3 months old, with an average age of 12 years and 8 months. There were 6 males and 15 females. All patients had abnormal alignment of their lower limbs, with 32 limbs having varus deformity and 10 limbs having valgus deformity. A total of 67 surgeries were performed across the 21 patients, including 24 cases of femoral osteotomy with antegrade intramedullary nail fixation, 6 cases of femoral osteotomy with retrograde intramedullary nail fixation, and 20 cases of tibial osteotomy with interlocking intramedullary nail fixation. A total of 34 limbs eventually underwent interlocking intramedullary nail fixation, 9 with genu valgum and 25 with genu varus. All 21 patients were followed up for a period of 14∼96 months, with an average of 42.6 months. The ends of the osteotomies achieved bony union in 4-9 months (average 6.8 months), after which normal weight-bearing walking could be resumed. No infection, vascular or neurological complications, or nonunion occurred. During postoperative follow-up, the alignment the lower limbs passed through zone 1 in 13 limbs, zone 2 in 12 limbs, and zone 3 in 5 limbs. The overall rate of an excellent effect was 83.3%. For lower limb deformity caused by hypophosphatemic rickets in older children, multi-segment osteotomy and strong fixation with interlocking intramedullary nails can achieve good correction outcomes.