Torsional Forces Research Articles

Biomechanical analysis of intramedullary vs. superior plate fixation of transverse midshaft clavicle fractures

Middle-third clavicle fractures represent 2% to 4% of all skeletal trauma in the United States. Treatment options include intramedullary (IM) as well as plate and screw (PS) constructs. The purpose of this study was to analyze the biomechanical stability of a specific IM system compared with nonlocking PS fixation under low-threshold physiologic load. Twenty fourth-generation Sawbones (Pacific Research Laboratories, Vashon, WA, USA) with a simulated middle-third fracture pattern were repaired with either an IM device (n = 10) or superiorly positioned nonlocking PS construct (n = 10). Loads were modeled to simulate physiologic load. Combined axial compression and torsion forces were sequentially increased until failure. Data were analyzed on the basis of loss of rotational stability using 3 criteria: early (10°), clinical (30°), and terminal (120°). No significant difference was noted between constructs in early loss of rotational stability (P > .05). The PS group was significantly more rotationally stable than the IM group on the basis of clinical and terminal criteria (P < .05 for both). All test constructs failed in rotational stability. When tested under physiologic load, fixation failure occurred from loss of rotational stability. No statistical difference was seen between groups under early physiologic loads. However, during load to failure, the PS group was statistically more rotationally stable than the IM group. Given the clavicle's function as a bony strut for the upper extremity and the biomechanical results demonstrated, rotational stability should be carefully considered during surgical planning and postoperative advancement of activity in patients undergoing operative fixation of middle-third clavicle fractures. Basic Science Study; Biomechanics.

Intra-operative fatigue failure of hexagonal screwdriver tip - case report of a potential complication in trauma surgery.

Intra-operative instrument breakage is a potential complication that not only leads to increased surgical time and agony to the patient but also is a source of frustration to the surgeon. The retrieval of the broken hardware may pose another challenge and sub optimal outcome in certain cases. There are numerous reports describing breakage of different sorts of medical devices and instruments and improvised methods of their successful retrieval. Orthopedic surgery requires use of manual force with instrumentation and thus the risk for important hardware failure remains omnipresent. The hexagonal screw-driver is widely used to fasten bone screws and is subjected to higher torque leading to rotation and torsion forces that may lead to excessive stress on it that at times goes past its yield point. The present case report describes an untoward event of breakage of screwdriver tip during surgery and its management. The presented report underlines importance of anticipation of this underreported complication of a common procedure.

Augmented beam elements using unit deflection shapes of the cross section

Wave behavior of line-shaped structures can be analyzed with the help of beam theories if the structures have a simple cross section (beams, rods, etc.), and if the frequency or wavelength is within a range where the theories are still applicable. If the frequencies and wavelengths exceed these limits, the modeling of line- or beam-shaped structures requires volume elements, which results in considerably higher computation time and modeling effort. The goal of this work is to keep the beam-like modeling of structures, but enhance the solution space such that arbitrary deflection shapes of the cross section can be covered. New degrees of freedom are introduced which correspond to the contribution of a unit deflection shape at each node. The unit deflection shapes are defined and computed on the basis of a 2D finite element mesh of the cross section: warp shapes for primary and secondary torsion and shear forces, eigenmodes for the problem of a plate in membrane and a plate in bending action, derived warp shapes for in-plane shapes, shapes which cover the lateral strains and—most importantly—eigenmodes of the infinite waveguide structure. By this transformation of unknowns, the number of system degrees of freedom can be reduced considerably. Different sets of unit deflection shapes are compared according to their efficiency.

Evaluation of Different Bracket's Resistance to Torsional Forces from Archwire

The present study was aimed to evaluate the resistance to deformation or fracture of brackets of various materials (ceramic, ceramic reinforced with metal slot, and stainless steel brackets) with archwires during application of torque. The sample size included 30 brackets of maxillary right central incisor with slot dimension of 0.022 × 0.028" and made of three materials (10 of each type): (1) Ceramic brackets (cer), (2) ceramic brackets reinforced with stainless steel slot (cer/ss), and (3) stainless steel brackets (metal). Thirty stainless steel archwire segments of 0.019 × 0.025" SS 5 cm in length were used. Elastomeric ties were also used in this study. Highest to lowest deformation or fracture torque found is as follows: Stainless steel brackets (5713.2 gfmm), metal ceramic reinforced with metal slot brackets (4080.8 gfmm), and ceramic brackets (3476 gfmm). Stainless steel brackets showed significantly higher values of torsional load than ceramic brackets reinforced with metal slot and ceramic brackets. Clinically orthodontic treatment is based on specific force applications to the dentition, the maxilla and the mandible. In order to obtain these forces, orthodontic brackets are attached to the teeth. Most commonly used brackets are metal (stainless steel), ceramic, and combination of metal reinforced ceramic brackets. For successful orthodontic treatment, it is necessary to maintain proper torque and avoid torque loss. Torque loss leads to deepening of bite. Torque loss occurs due to many reasons, one of them being bracket failure to withstand applied torque.

Love waves excited by a moving source

The study analyzes the characteristics of surface Love waves excited by the moment of an oscillating torsional force with a point of action that moves uniformly and rectilinearly along the free flat boundary of a medium having the structure of a “layer on a half-space.” The azimuthal–angular distribution of the amplitude and Doppler shift in frequency of the wave modes is studied as a function of the motion velocity of a vibrating source and the parameters of the medium.

Aerodynamics of closely spaced buildings: With application to linked buildings

This paper investigates inter-building and intra-building aerodynamic correlations of linked buildings (LBs, i.e., adjacent tall buildings structurally connected by links such as skybridges, skypools and skygardens). Spatiotemporal wind pressure data on a typical LB setup with different gap distances are used to examine inter-building aerodynamic correlation, which is presented in terms of the correlation coefficients between local wind force components and between generalized force components of the two LBs. The along-wind inter-building correlation coefficient is found to decrease for wind direction α=0° and increase for α=90° with increasing gap distance, whereas variation of cross-wind inter-building correlation is complicated. In addition, it is illustrated that the wind-induced response of the LBs usually relates positively to the correlation coefficient between the generalized force components of the two buildings in the associated unlinked case. Intra-building aerodynamic correlation of the LBs is examined using correlation coefficients and trajectories, and then compared with those of an isolated building. Results show that intra-building aerodynamic correlations differ considerably, especially between along-wind and torsional force components. However, although intra-building aerodynamic correlation is significant, its effect on the wind-induced responses of LBs is found to be relatively small. It may even be overshadowed by the effects of link-induced structural coupling.

Polypyrrole coating on poly-(lactide/glycolide)-β-tricalcium phosphate screws enhances new bone formation in rabbits

Polypyrrole (PPy) has gained interest as an implant material due to its multifunctional properties and its high compatibility with several cell and tissue types. For the first time, the biocompatibility and osteointegration of PPy coating, incorporated with chondroitin sulfate (CS), were studied in vivo by implanting PPy-coated bioabsorbable bone fixation composite screws of poly-(lactide/glycolide) copolymer (PLGA) and β-tricalcium phosphate (TCP) into New Zealand white rabbits. Uncoated bioabsorbable polymer composite screws and commercially available stainless steel cortical screws were used as reference implants. The rabbits were euthanized 12 and 26 weeks after the implantation. The systemic effects were evaluated from food and water consumption, body weight, body temperature, clinical signs, blood samples, internal organ weights, and histological examination. Local effects were studied from bone tissue and surrounding soft tissue histology. New bone formation was evaluated by micro-computed tomography, tetracycline labeling and torsion tests. Torsion tests were performed in order to capture the peak value of the torsion force during the course of the screw’s loosening.The coated screws induced significantly more bone formation than the uncoated screws. In addition, none of the implants induced any systemic or local toxicity. The results suggest that PPy is biocompatible with bone tissue and is a potential coating for enhancing osteointegration in orthopedic implants.

A reduced dimensionality model of torsional vibrations in star molecules

The torsional vibrations of star molecules are studied with a reduced dimensionality model. In this model, the molecule is described by two equivalent sets of lumped inertial cylinders and vibrational frequencies are predicted by solution of the coupled equations of motion. Force constants are determined by including them as free parameters in the model and fitting the computed frequencies to their analogs as determined using full normal coordinate analysis at the HFSCF level of theory. Best agreement between the methods occurs when torsional force constants are included for the first two layers of the molecule. This reveals that non-bonded torsional interactions are important in the vibrational dynamics of these systems. Further insight is afforded by an analysis of why simple harmonic oscillator models are sufficient for modeling some related systems but fail to reproduce the trend in global mode frequencies for saturated aliphatic star molecules. The analysis reveals that the origin of this failure lies in backbone flexibility in these branched polymeric systems.

The bone screw fracture in torsion test with an extended finite element method

Finite element method is used to simulate a torsion force of a bone screw made of the 316L stainless steel biomaterial during implanting process. However, the calculated breaking angle and fracture location by the conventional finite element method are not consistent with the experiment results. Therefore, this study applies an extended finite element method from a nonlinear commercial software-ABAQUS, to simulate the bone screw torsion test. By calibrating the initial and accumulative fracture parameters and simulating the torsion process with these parameters, the results of fracture location, crack direction and the relation between torque and angle are consistent with the experiment results.

Insertion angle of orthodontic mini-implants and their biomechanical performance: finite element analysis

AbstractObjectiveThe aim of this study was to assess the stresses and strains generated after the application of two types of forces (traction of 200 gf and torsion of 20 N.cm) in two types of orthodontic mini-implants inserted at different (45° and 90° to the cortical bone) angles.Material and methodthree-dimensional models of two brands of mini-implant (SIN – Sao Paulo, Brazil, and RMO – South Korea) were exported and analyzed by finite element analysis (FEA). Analyses were performed on simulations of cortical bone, cancellous bone and the screw.ResultFEA analysis showed that RMO mini-implants had greater elastic deformation when subjected to tensile and torsional forces when compared with SIN mini-implants. For both trademarks and insertion angles tested, there was greater cortical bone deformation, but with the greatest strain located on the mini-implant. Tension on the mini-implant was located in its transmucosal profile region.ConclusionWhen comparing the two brands of mini-implants by FEA, it is fair to conclude that that the larger number of threads and their greater angle of inclination resulted in less resistance to deformation and induced a higher level of tension in the mini-implant and cortical bone when subjected to forces, especially when inserted at an angle of 45º to the cortical bone.

A Comparison of Torque Forces Used to Apply Intermaxillary Fixation Screws

When establishing intermaxillary fixation (IMF) using bone screws, fracture of a screw is a potential complication. This study was conducted to investigate the forces that arise at bone screw insertion and to determine safety margins between torque for manually tightened insertion and torque until breakage for 3 different IMF screw systems, which could ultimately favor the use of 1 IMF screw system based on decreased risk of complications. IMF screws were placed into porcine mandibles by 3 oral and maxillofacial surgeons. The porcine mandibles were evaluated for cortical thickness and suitable insertion sites by cone-beam computed tomography. Measurements of torque until failure were performed on predrilled aluminum plates by the primary author. A digital torque screwdriver measured 180 data points per second as continuous data and recorded the measurements. Measurements indicated clear differences in torsion forces between manually tightened insertions and torque until breakage for all 3 IMF screw systems. No statistical difference in safety margins was found among the IMF screw systems. Because no statistical differences in safety margins were found among the IMF screw systems, this study indicates that IMF screw selection should be based on other clinical factors, such as ease of use or economic factors. Future prospective studies are necessary to fully determine evidence-based criteria for IMF screw selection.

Vertical removal force and torsional resistance of a screwless Morse taper implant connection

Aims: The aim of this study was to measure the removal force and vertical tensile strength of a screwless Morse taper connection and compare it with screw retained connections. Methods: n order to measure the vertical tensile and torsional strength of the connection, a total of 12 Octo Implants (Tasarimmed, Istanbul, Turkey) 4 mm wide and 10 mm in length were used with a screwless Morse taper connection. Six repeated shots were applied to abutments for each standardized force: 300 grF, 500 grF, 800 grF, 1000 grF, 1400 grF, and 2500 grF. Measurements of vertical tensile strength and torsional strength were obtained four times for each group with a dynamometer and torque meter. Results: The results were analyzed using a 1-way ANOVA test. The intercept was found to be significantly different among the various strike forces for both vertical tensile strength and torsional strength (p lessthan .0001). A greater increase in the torsional and vertical strength was seen for 1400 grF strikes and was consequently entitled as a break point. Conclusion: Screwless Morse taper connection is predicted to be an adequate resistant to vertical removal and torsional forces.

Cognitive–motor dysfunction after severe traumatic brain injury: A cerebral interhemispheric disconnection syndrome

Background/Objectives: In most right-handed people, the left hemisphere is dominant for programming the temporal and spatial “how” (praxis) aspects of purposeful skilled movements, and the right hemisphere is dominant for control of the intentional “when” aspects of actions that mediate initiation, persistence, termination, and inhibition. Since the interhemispheric axons of the corpus callosum are especially susceptible to shearing from torsional forces during traumatic brain injury (TBI), the goal of this study was to learn whether participants with a history of severe traumatic brain injury demonstrate three types of cognitive–motor impairments that may result from callosal injury: ideomotor apraxia of the left hand, limb kinetic apraxia of the left hand, and hypokinesia of the right hand in response to left hemispatial stimuli. Method: Nine participants with severe TBI and nine healthy control participants were studied for the presence of ideomotor apraxia, limb kinetic apraxia, and hypokinesia. Results: When compared to the control participants, the participants with TBI revealed ideomotor apraxia and limb kinetic apraxia of the left hand and hypokinesia in response to left-sided visual stimuli when tested with the right hand. Conclusions: TBI appears to cause unilateral disorders of cognitive–motor functions. Future research is needed to understand how these cognitive–motor disorders are related to interhemispheric disconnection most likely induced by injury to the corpus callosum.

Mesh-adaptive LES for wind load estimation of a high-rise building in a city

This paper discusses the applicability of large eddy simulation (LES) to the wind-resistant design of buildings in cities. In order to accurately predict wind pressures and forces on actual buildings with complicated shapes, we partially introduce the unstructured grid system, which is formulated on the open-source CFD code. Applying the LES method for modeling the urban flow, where a specified high-rise building focuses on safety under wind loading, the combined model is employed to investigate aerodynamic characteristics. This model uses overset grids, consisting of the Cartesian grid and the unstructured-grids. According to previous studies, the Cartesian grid method can accurately generate the turbulent structures in the urban canopy, whereas the unstructured grid method can reproduce detailed patterns of the near-wake flows around a specified building inside a densely built-up area. In this study, we have applied the combined model consisting of the Cartesian grid and unstructured grid for wind load estimation of a high-rise building in a city. Particularly, at inclined wind direction to the main streets, there is a presumption of different effects of wind impact at each vertical level of a high-rise building along the street. Accordingly, relatively a large torsional force tends to be present. On the basis of the results obtained, their accuracy is checked in comparison with the previous data by wind tunnel experiment, and wind pressure distributions on the surfaces as well as wind force coefficients of a high-rise building are estimated and discussed in view of structural safety.

Influence of earthquake input angle on seismic response of curved girder bridge

The maximum seismic response of curved bridge is significantly related to the input angle of designated earthquake. Owing to structure irregularities, bridge reactions result from the interaction between the moment and torsion forces. Based on the solving of the seismic response of structure excited by a one-way earthquake input, a uniform expression of the unfavorable angle of the earthquake input was derived, and the corresponding maximum response of structure was determined. Considering the orthotropic and skewed dual-directional earthquake input manners, the most unfavorable angles for the two cases were also derived, respectively. Furthermore, a series finite element models were built to analyze the multi-component seismic responses by examining an example of curved girder bridge considering the variation of curvature radius and the bearings arrangement. The seismic responses of the case bridges, were excited by earthquakes at different input angles, and were calculated and analyzed using a response spectrum method. The input angles of earthquake excitation were progressively increased. From the analysis and comparison based on the calculation results mentioned above, the most unfavorable angle of earthquake excitation corresponding to the maximum seismic response of the curved bridge could be determined. It was shown that the most unfavorable angles of earthquake input resulted from the different response combination methods were essentially coherent.

Wave propagation in reconfigurable magneto-elastic kagome lattice structures

The paper discusses the wave propagation characteristics of two-dimensional magneto-elastic kagome lattices. Mechanical instabilities caused by magnetic interactions are exploited in combination with particle contact to bring about changes in the topology and stiffness of the lattices. The analysis uses a lumped mass system of particles, which interact through axial and torsional elastic forces as well as magnetic forces. The propagation of in-plane waves is predicted by applying Bloch theorem to lattice unit cells with linearized interactions. Elastic wave dispersion in these lattices before and after topological changes is compared, and large differences are highlighted.

Probing fibronectin-antibody interactions using AFM force spectroscopy and lateral force microscopy.

The first experiment showing the effects of specific interaction forces using lateral force microscopy (LFM) was demonstrated for lectin–carbohydrate interactions some years ago. Such measurements are possible under the assumption that specific forces strongly dominate over the non-specific ones. However, obtaining quantitative results requires the complex and tedious calibration of a torsional force. Here, a new and relatively simple method for the calibration of the torsional force is presented. The proposed calibration method is validated through the measurement of the interaction forces between human fibronectin and its monoclonal antibody. The results obtained using LFM and AFM-based classical force spectroscopies showed similar unbinding forces recorded at similar loading rates. Our studies verify that the proposed lateral force calibration method can be applied to study single molecule interactions.

Defect-induced carbon nanoscroll formation

Carbon nanoscrolls (CNSs), a graphitic structure formed by rolling of a graphene plane, must overcome an energy barrier in order to form. This energy barrier is the result of competing interactions between the van der Waals force, which wants to cause overlap of the graphene, and the torsional or bending force, which resists bending of the graphene plane. In this study we used molecular dynamics simulation to examine the effect of vacancies on the CNS formation dynamics. We found that the energy barrier, which must be overcome to obtain a stable scroll structure, can be lowered or completely eliminated by introducing vacancies. Individual vacancy and divacancy configurations are studied and found to reduce the torsional bending energy by allowing local stress relaxation around the defect site. A structural transition diagram is created in which we show the energy barrier height for a range of vacancy concentrations and CNS rolling widths. These results provide the theoretical backing for a new method of fabricating CNSs using a focused ion beam and shed new light on the self-rolling phenomenon in graphene.

Power Control of Wind Turbine Based on Fuzzy Sliding-Mode Control

This paper presents the study of a variable speed wind energy conversion system (WECS) using a Wound Field Synchronous Generator (WFSG) based on a Fuzzy sliding mode control (FSMC) applied to achieve control of active and reactive powers exchanged between the stator of the WFSG and the grid to ensure a Maximum Power Point Tracking (MPPT) of a wind energy conversion system. However the principal drawback of the sliding mode, is the chattering effect which characterized by torque ripple, this phenomena is undesirable and harmful for the machines, it generates noises and additional forces of torsion on the machine shaft. A direct fuzzy logic controller is designed and the sliding mode controller is added to compensate the fuzzy approximation errors. The simulation results clearly indicate the effectiveness and validity of the proposed method, in terms of convergence, time and precision.

Synthesis of lever-blade dampers with enhanced mechanical structure

Introduction. The torsion suspensions are in wide use at contemporary automotive engineering. Such suspension operating elements are torsions: elastic bars, loaded with torsion force. The torsion bars are traditionally used as suspension structure of armored vehicles and cars. Moreover, torsion bars in automobile suspensions can be used both as the elastic element, and as an auxiliary device, i.e. a stabilizing bar, purposed to create the vehicle’s anti-roll resistance. Given that the torsion bar represents only an elastic element, the question of energy dissipation in suspensions including such bar is quite relevant. Firstly the problem of improving the torsion bar suspensions’ energy dissipation has been solved in the UK, when for the first time in parallel with the torsion bars the hydraulic piston shock absorbers have been installed. Due to this the suspension’s tendency to body longitudinal vibrations has been eliminated with greatly improved smoothness of suspension’s course. Currently, in addition to said hydraulic piston or gas shock absorbers, characterized by the movable member’s translational motion respectively to the housing in wide use at torsion suspension structure are lever shock absorbers (piston and vane types), characterized by the movable member’s rotational movement respectively to the housing. So on each side of the T-72 tank (USSR), the first, second and sixth suspensions are equipped with three lever-blade dampers (lever rotation angle of 87°) [1]. The existing hydraulic shock absorbers are usually implementing a performance, consisting of digression and regression areas, that is due to the throttle and the throttle-valve modes of operation. However, increasing demands to the suspension of the vehicle require the implementation of other performance characteristics not implementable when the existing shock absorbers’ passive constructions using due to their functionality limitations. An alternative in the form of active damping systems’ application with respect to their high cost and additional energy consumed is selective being welljustified only for original unique or cost-expensive equipment [2]. Therefore, the synthesis of passive