Torsional Forces Research Articles

Electric torsion effect in a ferroelectric nanodot

Polar topologies with exotic textures and functionalities in low-dimensional ferroelectrics are recently drawing extensive attention. Elucidating the mechanical responses caused by the phase transitions under external excitation, especially the torsional response still unclear, is quite significant for the development of ferroelectric actuators. Here, using phase-field simulation, we propose a scheme to produce local torsional force via electric field excitation, namely, the electric torsion effect in a ferroelectric nanodot. The results indicate that the twisting response originating from the structural phase transitions between vortex and helical states is tunable in magnitude and orientation by manipulating the external electric fields. This work provides further insight into the electromechanical response of polar topologies and could be conducive to facilitating the development of torsion-based device applications in ferroelectric nanoelectronics.

Determination of Shear Capacity for Load Rating of Concrete Bridges to AS 5100.7-2017

According to Modified Compression Field Theory (MCFT), the ultimate shear capacity of a reinforced concrete section depends on load effects (shear, moment, torsion, and axial force) caused by factored design loads. In many design standards, including Australian AS 5100.7, MCFT has been incorporated for bridge assessment, which requires a load rating to be carried out according to the loading of the nominated rating vehicle as prescribed in the standard. Recently, some approaches have been proposed for bridge load rating that have suggested using an iterative-search procedure to determine the shear capacity by proportionally increasing the load effects until the shear capacity and shear are equal. This paper describes several adverse effects of using the proportional load, which is not consistent with the characteristic of the vehicle loading, to determine the shear capacity for load rating. Numerical examples of two bridge beams, one simply supported and the other continuous, are presented to demonstrate that the characteristic of the load effects caused by a moving vehicle is not representable by proportional load effects. Furthermore, the current practice in the bridge load rating does not load rate the longitudinal steel capacity in resisting the axial force induced by the load effects of the rating vehicle. This paper presents a new approach to the load rating that separately accounts for the load effect for axial failure mode of the longitudinal steel. Finally, it is pointed out that locating the critical section where the rating factor is minimum is tedious but can be automated by integrating load rating into the analysis of load effects.

Performance of strengthened RC beams with torsional CFRP wraps in monolithic framed structures: Experimental and numerical investigation

The performance of externally applied wraps to simply supported reinforced concrete (RC) beams under pure torsion has been well-defined in the literature. In most cases, the previous research works utilised carbon fibre reinforced polymers (CFRP) wraps with different configurations to enhance the beams torsional capacities. While the effectiveness of these wraps in monolithic framed beams in RC buildings is less understood. Further, there is still a lack of information regarding the influence of interacted-combined loads on both the wrapped beams and the joined columns. This paper deals with the presence of different wrapping schemes on the response of framed beams that joined to columns, and how different levels of eccentric torsional forces combined with bending and shear forces can alter the damage state. The experimental programme of this study involved a series of beam-column assemblies tested under concentric and eccentric combined loads. Based on the test observations, a nonlinear finite element (FE) procedure is proposed and validated for simulating the full response of RC beam-column assemblies. This validated FE procedure is then used to explore critical parameters which govern the wraps performance and the failure modes. The outcomes of this study provide comprehensive insights into the role of the interacted forces and the wrapping configurations on the developed deformations and the members integrity. In particular, the results confirmed that the torsional force adversely affected the flexural capacities in proportion to the ratio of the torsion applied. Meanwhile, the interacted forces can induce substantial strain and damage levels that can be extended to the joined column. The contribution of CFRP wraps is found to be limited to the concrete strut’s capacity and the extent of torsional shear-flow in consistent with the imposed loads ratios and the developed truss mechanism.

Effect of the anisotropic characteristics of β-Sn on current-induced solder evolution

The miniaturization trend of three-dimensional integrated circuits poses great challenges to solder reliability under high current stressing since anisotropic issues tend to be enhanced in microscale solder bumps. To address these challenges, the solder evolution at the microscale and the corresponding mechanism should be addressed. In this study, by considering the anisotropy of β-Sn in the electrical, thermal, mechanical and diffusional characteristics, the current-induced solder evolution of a typical solder bump was comprehensively explored over time. The results confirmed that the anisotropy of β-Sn aggravated the nonuniform distribution of current-induced stresses, further causing multiple migration modes coupled in the solder bump. The spatial inconsistency between the distribution of β-Sn unit cells and the bump geometry led to accumulation of torsion forces, which became the direct reason for solder rigid rotation. The electron-dislocation interaction promoted dislocation slip, leading to lattice rotation and homogenization of intragranular deformation. In addition, current-induced grain merging via detwinning was observed, and its velocity was faster than imagined. Our study is conducive to thoroughly understanding anisotropic evolution and establishing accurate damage mechanisms for micro solder bump design under current stressing.

Anti-puncture, frigostable, and flexible hydrogel-based composites for soft armor

Cold adaptation is essential to the protective effect of soft armor and other protective materials because of the potential for prolonged exposure to freezing conditions in service, while the properties of flexible matrices are always affected by low temperatures. To integrate the good protection efficiency and excellent anti-freezing properties, polyvinyl alcohol (PVA), sodium alginate (SA), and glycerol (Gly) were selected to prepare a frigostable hydrogel in this study. Afterward, the hydrogel was laminated with aramid fabric to obtain a flexible anti-puncture composite that can be used at low temperatures. At −30 °C, the breaking strength and elongation of PVA/SA/Gly hydrogel reached 1.32 MPa and 330%, which was basically the same as at room temperature, indicating its excellent cold adaptation. Meanwhile, the maximum puncture resistance force and energy dissipation of the aramid/hydrogel composite at −30 °C were 56.88 N and 263.07 mJ, respectively, 289% and 184% higher than that of neat fabric, while the weight gain rate of the composite was only 40%. At room and low temperatures, the flexibility of the composite was only 5% and 8% lower than that of the neat fabric, respectively, and a helix shape of 360° could be formed and maintained under a small torsional force even at −30 °C.

Effect of implant length variations on stress shielding in proximal humeral replacement after tumor excision under torsion: Finite element study.

The proximal humerus is the most common site of occurrence of primary bone tumors in the upper limb. Endoprosthetic replacement is deemed as the preferred reconstructive option following primary resection of bone tumors. However, it has been also associated with complications such as stress shielding and aseptic loosening compromising prosthetic survival. Our objective was to conduct a finite element (FE) study to investigate the effect of varying endoprosthesis length on bone stresses as well as to quantify the extent of stress shielding across the bone length (BL) in a humerus-prosthesis assembly for proximal humeral replacement after tumor excision thereby allowing us to identify the optimal implant length with best biomechanical performance. FE models of the intact humerus and humerus-prosthesis assemblies were established where they were loaded at the elbow joint under torsion with the glenohumeral joint fixed to represent twisting. After dividing the bone into individual slices consisting of 5% BL, the maximum cortical and cancellous principal, von Mises and shear bone stresses were calculated. To measure the level of stress shielding, the percentage stress change from the intact state was evaluated across each slice. Similar stress patterns were observed between the intact state and shorter endoprosthesis compared to the longer endoprostheses. Our findings illustrated the possibility of stress shielding occurring under torsional forces with its effect increasing with implant lengthening. To conclude, we believe that using a shorter prosthesis may substantially diminish the risk of potential implant failure due to stress shielding.

Structural challenges for seismic stability of buildings in hilly areas.

Buildings on hills behave dynamically, very different from buildings on flatlands. Due to irregularity in horizontal and vertical planes, they inhibit non-uniform mass and stiffness distribution and are subjected to torsional forces. Studies in various Indian cities in hilly terrains have highlighted serious concerns about existing construction practices. Lack of adequate planning and design has resulted in haphazard development in hilly regions. This state-of-the-art review investigates the factors that influence the structural performance of buildings on slopes while explaining reasons that have caused enormous damages and even collapse of hill buildings in the recent earthquake events. The work discusses building configurations, comparison of various vital building regulations, the major problems encountered in building stocks and associated structural deficiencies on hill slopes. The significance of intensification of earthquake-related losses due to soil amplification has been well documented in the past. Insights from experimental and numerical studies focusing on impacts of topographical and geological factors on damage amplification of hillside buildings are fetched, the results of which are in good corroboration with the findings of post-earthquake surveys and reviews. This study establishes that a higher slope gradient necessitates more slope cutting than a lower slope gradient to get the same building footprint, and many times, this value exceeds the permissible height of slope cutting given in existing building byelaws. Such excessive slope cutting makes the slope weak and unstable. Recommendations and solutions to help enhance structural resilience, reduce disproportionate damages and mitigate failure of hill buildings have been delineated.

CTOR plates- Revolutionizing treatment of complex malocclusions

Temporary Anchorage Devices have been the only means of providing absolute anchorage but have complications of causing soft and hard tissue damage and requires well-formed cortical bone. Also, they are unable to tolerate torsional forces and moments. For this reason, miniplates had come up with the advantage of providing more surface area but are difficult to place as they require flap surgery and also removal post treatment. CTOR plates have revolutionized the way of harnessing anchorage by ease of placement, removal and patient comfort. They are placed with the help of two implants and come in wide variety of shapes and modifications, increasing the magnitude of orthodontic treatment modality. They are placed at a distance from soft tissues and thus cause no irritation. Intrusion, extrusion, protraction and retraction of teeth are some of the orthodontic movements that can be achieved without any loss of anchorage from the CTOR plates. Thus, CTOR greatly expands the ability of Orthodontists to treat severe skeletal problems non-surgically. (Provide appropriate messages of about 35-50 words to be printed in centre box):

Is "Bite force" a reliable parameter to compare masticatory efficiency restoration following ORIF of anterior mandibular fractures?

ObjectivesMandible is an integral part of masticatory system, and it is expected that it’s fracture will have a significant impact on occlusal forces, range of motion, muscle activity levels, and occlusion. The main objective of this study was to compare the efficacy of 3-dimensional (3D) miniplate and conventional miniplates for fixation of anterior mandibular fractures on the basis of bite force as a main parameter.Methods66 patients having isolated anterior mandibular fractures were randomized into two groups equally: Conventional miniplates and 3D miniplates. The bite force at incisor, canine, and molar regions was measured preoperatively and postoperatively at weekly intervals until the sixth week, and the mean bite force as well as changes in mean bite force were compared between two groups.ResultsAn increase in bite force was noted at each subsequent follow up in both the groups across all sites. Statistically significant difference was found in mean bite force values between both the groups during mid-follow up period. The difference in changes in the mean bite force too was observed to be statistically significant during the mid to late follow up period.Interpretation & conclusionBite force is a reliable parameter to assess restoration of masticatory efficiency following open reduction and internal fixation (ORIF). 3D miniplates when used in anterior mandibular fractures management are efficient enough to withstand masticatory forces throughout the healing process, providing better stability of fractured segments against torsional forces during immediate post-operative period.

Nanotribology and electrical properties of carbon nanotubes hybridized with covalent organic frameworks

Nanomanipulation of molecular materials such as carbon nanotubes (CNTs) or new covalent organic frameworks (COFs) is key not only for the study of their fundamental physicochemical properties, but also for building and probing nanodevices. Therefore, we have investigated the tribological properties of oxidized MWCNTs (ox-MWCNTs) and their hybridization with COF building blocks (ox-MWCNTs@COF) adsorbed on a mica surface. We used the AFM tip to apply torsional forces on individual nanotubes. Depending on the manipulation parameters, the lateral displacements of the AFM tip slide and/or bend nanotubes enabling the direct quantification of the nanotube-mica adhesion. We found striking changes in the behaviour of the lateral force needed to manipulate each carbon nanotube variant which indicates an increased adhesion of ox-MWCNTs@COF with respect to ox-MWCNTs (∼10x). In addition, the use of the AFM tip as a mobile electrode enabled the measurement of electrical transport through individual nanotubes that revealed a rectifying behaviour of the ox-MWCNTs@COF with high resistivity, which was in contrast with the near ohmic performance of ox-MWCNTs.

Numerical simulation and biomechanical analysis of locking screw caps on clavicle locking plates.

Background:The risk of displaced and comminuted midshaft clavicle fractures is increased in high-energy traumas such as sport injuries and traffic accidents. Open reduction and plate fixation have been widely used for midshaft clavicle fractures. Among various plates for clavicle shaft fractures, superior locking compression plates (LCPs) have been mostly used. In plate fixation, nonunion caused by implant failure is the most difficult complication. The most common reasons for metal plate failure are excessive stress and stress concentration caused by cantilever bending. These causes were easily addressed using a locking screw cap (LSC).Methods:The clavicle 3-dimensional image was made from a computed tomography scan, and the clavicle midshaft fracture model was generated with a 10-mm interval. The fracture model was fixed with a superior LCP, and finite element analysis was conducted between the presence (with LSC model) and absence (without LSC model) of an LSC on the site of the fracture. The stresses of screw holes in models with and without LSCs were measured under 3 forces: 100 N cantilever bending force, 100 N axial compression force, and 1 N·m axial torsion force. After the finite element analysis, a validation test was conducted on the cantilever bending force known as the greatest force applied to superior locking plates.Results:The mean greatest stress under the cantilever bending force was significantly greater than other loading forces. The highest stress site was the screw hole edge on the fracture site in both models under the cantilever bending and axial compression forces. Under the axial torsional force, the maximum stress point was the lateral first screw hole edge. The ultimate plate stress of the with LSC model is completely lower than that of the without LSC model. According to the validation test, the stiffness, ultimate load, and yield load of the with LSC model were higher than those of the without LSC model.Conclusions:Therefore, inserting an LSC into an empty screw hole in the fracture area reduces the maximum stress on an LCP and improves biomechanical stability.

Experimental investigation on the mechanical square clinching process for joining Al5052 sheets

Clinching technology has been extensively applied as a green and clean joining method, which has the benefits of less energy consumption, no pollution and no noise. However, a single joint produced by round tools cannot withstand the torsion force. In order to solve this problem, a square clinching technology was proposed and investigated in this paper. The main geometric parameters, failure mode, static strength, and energy absorption of the square clinched joint were studied. The fracture characteristics of square clinched joints under different mechanical experiments were studied by a scanning electron microscope. The strength tests of Al5052 clinched joints under various forming forces were carried out. The results showed that the neck fracture mode was the only failure mode observed during the failure process. The microscopic morphology of the joint fracture shows typical ductile fracture characteristics. It turned out that the square clinching process can effectively join aluminum alloy sheets.

ПРЕДВАРИТЕЛЬНОЕ ОПИСАНИЕ РАБОТЫ ЖЕЛЕЗОБЕТОННЫХ ЭЛЕМЕНТОВ С ВНЕШНИМ АРМИРОВАНИЕМ КОМПОЗИТНЫМИ МАТЕРИАЛАМИ ПРИ ИЗГИБЕ С КРУЧЕНИЕМ

The calculation methods of reinforced external reinforcement elements when working on torsion are considered succinctly in available sources and current regulatory documents. This article discusses a number of existing proven methods for calculating reinforced concrete bendable elements with external composite reinforcement, including when working with torsion. The necessity of introducing into the existing calculation dependences of the prerequisites for substantiating the behavior of reinforced concrete bendable elements, including those with external composite reinforcement, when working in a complex stress-strain state is described. The cases of occurrence of additional torsional forces in the conditions of classical variants of loads and impacts on the element are considered. A description of the work of reinforced concrete elements with external reinforcement with composite materials during bending with torsion is proposed. The main provisions of the work of reinforced concrete structures in bending with torsion are given. The main limiting states are presented. An assumptions are made about the possible presence of additional limiting states of reinforced concrete elements with external reinforcement with composite materials. A variant of the condition of proportionality of longitudinal relative deformations for reinforced concrete elements with external reinforcement with composite materials during bending with torsion is proposed.

Aerodynamic correlation and flow pattern of high-rise building with side ratio of 3:1 under twisted wind profile: A computational study

This study numerically investigates twisted-wind effect on aerodynamic correlation and flow pattern of high-rise building with 3:1 side ratio. Spatial-temporal correlation of aerodynamic forces and flow filed under conventional wind profile (CWP) and twisted wind profile (TWP) are comprehensively compared. Proper orthogonal decomposition (POD) is further employed to extract wake flow pattern and mode correlation. The results show that twisted-wind effect on building with long afterbody is unique. Specifically, compared with CWP, TWP augments mean wind loads in three perpendicular directions (e.g., CMx under TWP30 is increased by 60.56% compared to CWP). The original two vortex structures (i.e., leading-edge vortex shedding (LEVS) and trailing-edge vortex shedding (TEVS)) appearing in CWP transit to relatively weaker alternate-edge vortex shedding (AEVS) in TWP, thus, the fluctuating lateral base moment and torsional force are reduced by 30.60% and 28.24% respectively under TWP30 compared to CWP. Correlation of wind load components and correlation of layer force are significantly magnified because TWP intensifies vertical moment exchange and force coupling effect, this possibly results in stronger wind-induced responses. POD analysis reveals essential mechanism of twisted-wind effect and shows that flow pattern (i.e., energy proportion, dominant frequency, mode shape and mode correlation) is largely changed by TWP.

Theoretical and experimental modeling of deformation of a cylindrical shell made of 45 steel under complex loading

Thin-walled cylindrical shells are used in elements of highly loaded products of mechanical engineering and energy. Along with their frequent use in production, experimental research in laboratories is also carried out constantly. This allows to simulate the behavior of the shell when exposed to external forces. But sometimes conducting an experiment becomes little possible due to the limitation of the power of the experimental apparatus when modeling the corresponding conditions of exposure to the shell in practice, therefore, improving theoretical methods for calculating the limiting states of shells when working in the elastoplastic region is relevant. The purpose of the study is to verify the conformity of the results of the experiment conducted on a thin-walled cylindrical shell made of steel 45 (GOST 1050-2013) when exposed to the sample by stretching, compression and torsion forces with theoretical calculations based on the equations of the theory of elastic-plastic processes by A.A. Ilyushin. The equations of the defining relations of the theory of elastic-plastic processes by A.A. Ilyushin for arbitrary trajectories of complex loading and deformation of materials in the deviatory deformation space Э1-Э3 are presented. All theoretical results are checked for compliance with the experiment, the reliability of the existing theory of stability is assessed. The solution is presented in the form of graphs of the dependence of the vector and scalar properties of the material on the length of the arc of the deformation trajectory and other parameters. Numerical values are selectively presented for different loading stages.

A biomechanical study: Comparison of three different implant options in high Tibial osteotomy

BackgroundMany implant options could be preferable for fixation after osteotomy in varus knee medial compartment arthrosis. Due to usage characteristics, it is important to compare the biomechanical properties of them. For this purpose, we aimed to examine three different implant types biomechanically in our study. MethodsOvine tibiae undergoing medial open-wedge high tibial osteotomy were fixed in vitro with three different implants using an angular wedge plate, a metal block plate and an external fixator system. The fixed ovine tibiae were subjected to axial tensile, axial loading and three-point bending tests in a test machine. All biomechanical tests were repeated five times, the maximum and minimum values were ignored, and the average values of the remaining three test results were taken into account. The test results were interpreted after converted into force-elongation curves in Trapezium-X software. FindingsBiomechanical test results revealed some differences between implant types. While the metal block plate had the highest axial tensile strength value, it was the fixation group showing the lowest strength in axial load tests. The used fixator system was the highest strength in axial load tests and the lowest strength in axial tensile tests. InterpretationConsidering the clinically significant forces related to the biomechanical stability of the three different implants used for high tibial osteotomy, the fixator system would appear to be slightly superior, although it should be noted that torsional forces, as well as parameters that could change in living tissue, might affect the results.

Experimental investigation of semi-interlocking mortarless masonry-infilled frames

Masonry-infilled frames (MIFs) are a common construction form in many parts of the world. The presence of mortared masonry makes structural frames relatively stiff resulting in limited displacement capacity and unintended torsional forces that have been responsible for catastrophic destruction of buildings during several past seismic events. An alternative infill material solution is using semi-interlocking (mortarless) masonry (SIM), which is associated with controlled in-plane sliding. Five small-dimensioned specimens, including one bare frame and four SIM-infilled concrete frames were constructed and subjected to cyclic displacements. The variable parameters included specimen aspect ratio, vertical load on frame members, and grouting of masonry.A detailed description of the construction procedure and the testing of material properties used in the experiments are presented. The damage patterns associated to each of the specimens are explained to investigate their deformation modes and to identify the drift thresholds corresponding to the damage in the MIFs. A modified idealisation model is proposed that is suitable for SIM-infilled reinforced concrete MIFs. Critical structural properties of MIFs that include the yield strength, energy dissipation capacity, initial stiffness and ductility are obtained from the idealisation model and the force-displacement relationship. These properties are compared and contrasted against the specimens and also to the traditional MIFs with the relevant data extracted from literature. From the observed damage and the force-displacement relationship, Performance Levels of the MIFs are established. Compared to traditional MIFs, the SIM-infilled MIFs are shown to have significantly smaller initial stiffness and larger performance level drift thresholds.

Extracellular matrix in intervertebral disc: basic and translational implications.

Intervertebral disc (IVD) degeneration (IVDD) is the most common spinal disorder, which can lead to the symptoms of neck pain or low back pain. In healthy mature IVD tissues, extracellular matrix (ECM) complex possesses favorable biochemical and biomechanical properties, withstanding compression and torsion forces. IVD cells and ECM associate with each other to form a coordinated functional system. IVD cells are the main producers of ECM components, while ECM could modulate the viability and phenotype of IVD cells via direct interactions or indirect regulations. However, with the process of IVDD and ageing, ECM of IVD undergoes content loss and structure degeneration. Moreover, the accumulation of catabolic products may further deteriorate the IVD microenvironment. A better understanding of the physiology and the pathology of ECM within the IVD provides new insight into potential IVD regeneration strategies. Natural ECM components, functional motifs, or mimetic peptides are widely used in IVD repair by not only restoring structural support but also regulating cell fate and tissue microenvironment. Herein, we reviewed recent advances in the involvement of ECM in IVD health and disease, with an emphasis on ECM composition and organization, cell-matrix interactions, pathological ECM degradation, and promising matrix-based biomaterials for IVD regeneration.

Functional outcome of surgical management of fracture of proximal humerus treated with proximal humerus internal locking operative system plating

Purpose: To study the functional outcome of proximal humerus internal locking system plating in displaced proximal humerus fractures.Materials and Methods: Prospective interventional study a total of 30 patients admitted in VIMS, Ballari with displaced proximal humerus fractures between August 2020 and August 2022 were included in the study. Patients were treated with proximal internal locking system plating and followed up at 6 weeks, 12 weeks and 6 months and were evaluated for functional outcome using Constant and Murley shoulder scoring system.Results: Excellent outcome was noted in 20%, Good in 47%, fair in 23% and poor in 10% cases. 90% of patients had clinical and radiological union in 3 months. The range of motion showed gradual improvement in successive follow ups.Conclusion: PHILOS plate provides a high degree of angular and axial stability eliminating screw loosening and backout. PHILOS plate showed significantly less plastic deformation subsequent to torsional and axial forces.

Effect of Tongue Thrust on Implants Integration

The human tongue is a muscular organ with a variety of life-important functions. Mastication and swallowing, taste, and speech are vital functions. From the analysis of the lingual function, clinical considerations during the oral-pharyngeal phase of swallowing, the tongue thrusts anteriorly and laterally, creating enormous pressure. If it applies to freshly inserted dental implants, it could be leading to early implant failure. Different authors have calculated this pressure between 20 and 200 kPa, depending on tongue volume, producing resultant torsion forces on implant abutment. The work aims to understand the importance of the destabilizing action of the tongue in the post-operative period. When the use of implants resting in quiescence for a long time under the gums is not possible, because of anatomical reasons (for example: thin ridge), or: immediate loading is planned, the action of the tongue must be considered. We are proposing some solutions to the problem to improve therapeutic safety: 1)Attach immediate provisional prostheses to existing adjacent teeth. 2)Immediately upon implants insertion, rigidly connect implants. 3)When an immediate loading protocol is implemented, the operator should follow the guideline, taking care to apply correctly balanced axial forces, without any lateral stress. Our professional experience, based on over 10.000 clinical cases performed during 35 years, confirms that, with implants emerging in the oral cavity, handling in proper way the tongue thrust during the healing period makes the difference. All what has been here implemented about this subject, represents the development of the legacy left by Prof. Ugo Pasqualini, an Italian dentist who, since the seventies, has been deepening the topic of the risks tied to the intra-oral stresses acting on the emerging part of the implants.