Torsional Forces Research Articles

Analysis on corrosion fatigue cracking mechanism of 17-4PH blade of low pressure rotor of steam turbine

The causes of many blade fractures of a steam turbine in a power plant were studied by means of macro analysis, mechanical tests, metallographic examination, SEM and X-ray fluorescence spectrum analysis (XRF). The results show that the blade cracks due to corrosion fatigue. Cl −,K +react with the turbine blades in the steam environment in physical, chemical and electrochemical ways, causing local spot corrosion on the blades, forming corrosion pits. In addition, the steam condensated has an erosion effect on the blades, both of which form a corrosion fatigue source. The autocatalytic process of block cell is formed when Cl −, K + react with the turbine blades. Under the action of combined load, the current density i of activation dissolution of metal can be expressed as a function of complex stress state.Crack growth has an important relationship with stress, depth and width of corrosion pits. The blade cracks are determined by threshold nominal stress range for crack elongationΔσth, which depends on the depth and width of corrosion pit. The combined alternating stress directly promotes the crack propagation until the fracture fail under the external conditions of alternating stress formed by tensile force, bending force, torsion force, and exciting force.

Knowledge and Awareness of Precision Attachments among Dental Students

Significant reconstruction of damaged teeth requires a great deal of new and traditional treatment methods, and the design of attachment retained removable partial dentures is one such therapeutic approach in prosthodontics. Customized semi-precision fittings with partial dentures provide strength and enhanced aesthetics in situations with limited space. The objective of the study was to determine the knowledge and understanding of precision attachments amongst dental students. A descriptive survey was conducted among undergraduate and postgraduate dental students using a structured questionnaire. The questionnaire gathered information on the respondent's knowledge regarding the use of precision attachments among dental practitioners in dentistry. Out of the 100 students,60% of them believed that based on the geometric configuration and design of the attachment precision attachments can be classified as the key lock, 20% believed that they were classified as latch type attachments and the rest 20% believed that they were classified as ball and socket attachment. Out of the 100 students who took the survey, 80% believed that the advantages of using precision attachments were all except increasing the stress to abutment and 20% believed that the advantages were all except decreasing torsional forces. All the students who had taken part in the survey had moderate knowledge about the use of precision attachments in dentistry. More intensive educational and awareness initiatives should be undertaken to increase the awareness levels about precision attachments among dental students.

Voltage-controlled instability transitions and competitions in a finitely deformed dielectric elastomer tube

This work compares the transition and competitive mechanism between three types of instabilities of an incompressible dielectric tube: wrinkling, pull-in instability and electric breakdown. We also see how to select one type of instability mode on demand. First, we investigate the finite response and the wrinkling of a tube subject to a combination of applied radial voltage, torsion and axial force (or stretch). We use the surface impedance matrix method to determine the wrinkling threshold, and obtain the corresponding two-dimensional pattern shape of wrinkled surface. Second, we look at illustrative numerical calculations for ideal Mooney-Rivlin dielectrics and study the effects of actuation methods, electric voltage, torsion and geometrical parameters on the three types of instabilities. Results show that the deformation of the solid will influence the true electric field in the solid, and induce competitive effects between the applied voltage and the mechanical loading. We find that in addition to the expected contractile buckling, buckling may also occur in extension in an electrically actuated dielectric tube, a departure from the purely elastic wrinkling. Moreover, the electro-elastic behavior of the DE elastomer can be enhanced by introducing torsion. We also find that large stable actuation can be achieved and that the wrinkling pattern can be selected on demand in the tube by finely tuning the actuation, voltage, torsion and geometry, without encountering material failure.

Symptomatic Nonunion of the Medial Humeral Epicondyle Fracture: A Case Report and Review of the Literature

Symptomatic nonunion of medial epicondyle fractures of the humerus is a rare entity. The surgical technique can be difficult due to anatomic and biomechanical factors, such as the high tension and the torsional forces applied from the flexor-pronator tendon origin. The most common complications of nonunion of the medial humeral epicondyle fracture are chronic pain, instability in valgus of the elbow, and neuropathy of the ulnar nerve. We described the case of 1 patient with symptomatic medial humeral epicondyle nonunion, who underwent open reduction and internal fixation with excellent clinical evolution after 1 year of follow-up from time of surgery. The purpose of this study was to evaluate the outcome of open reduction and internal fixation of a medial epicondyle nonunion fragment in 1 case and present a review of the literature.

The Evolvement of Mechanical Properties and Microstructure of Commercial Aluminum Alloy 6061 via High-Pressure Torsion

A precipitation-hardened AA6061 alloy is processed by high-pressure torsion (HPT) technique which has demonstrated its success in refining grain structures up to the nanometer-scale. With the aim of upscaling the strengthen lightweight materials for larger applications, this study is essential to analyse the related strengthening mechanisms for further strengthening potential and microstructure alteration on sample with extra diameter size. This severe plastic deformation (SPD) technique simultaneously contributes to an intensification of dislocation density which caused by the grain refinement. This study presents properties enhancement of 30mm diameter of AA6061 alloy after being compressed at 4GPa pressure and subjected to a 0.2 rpm torsional force for 1 and 3 turn(s) at room temperature. For the result testing, Vickers microhardness, tensile test, X-ray diffraction (XRD) and Transmission electron microscopy (TEM) were used as to analyse the mechanical properties as well as the microstructure changes. As a result, grain structures were refined to 200nm, and its mechanical properties, such as tensile strength and hardness is enhanced to ±600MPa and ±172HV, respectively. The homogeneity of hardness is increased with the number of turns or the torsional strain applied. For this particular aluminium alloy, the grain refinement and grain boundary hardening were identified as the main hardening mechanisms by the process of HPT.

Development of Magnetic Torque Stimulation (MTS) Utilizing Rotating Uniform Magnetic Field for Mechanical Activation of Cardiac Cells

Regulation of cell signaling through physical stimulation is an emerging topic in biomedicine. Background: While recent advances in biophysical technologies show capabilities for spatiotemporal stimulation, interfacing those tools with biological systems for intact signal transfer and noncontact stimulation remains challenging. Here, we describe the use of a magnetic torque stimulation (MTS) system combined with engineered magnetic particles to apply forces on the surface of individual cells. MTS utilizes an externally rotating magnetic field to induce a spin on magnetic particles and generate torsional force to stimulate mechanotransduction pathways in two types of human heart cells—cardiomyocytes and cardiac fibroblasts. Methods: The MTS system operates in a noncontact mode with two magnets separated (60 mm) from each other and generates a torque of up to 15 pN µm across the entire area of a 35-mm cell culture dish. The MTS system can mechanically stimulate both types of human heart cells, inducing maturation and hypertrophy. Results: Our findings show that application of the MTS system under hypoxic conditions induces not only nuclear localization of mechanoresponsive YAP proteins in human heart cells but also overexpression of hypertrophy markers, including β-myosin heavy chain (βMHC), cardiotrophin-1 (CT-1), microRNA-21 (miR-21), and transforming growth factor beta-1 (TGFβ-1). Conclusions: These results have important implications for the applicability of the MTS system to diverse in vitro studies that require remote and noninvasive mechanical regulation.

A Study on the Dynamic Problems of Cylindrical Shells under the Coupling of Tensile and Torsional Forces

In this paper, the critical buckling load and dynamic buckling mode are reduced to symplectic eigenvalues and eigensolutions in symplectic space according to the non synchronous propagation of axial stress wave and torsional stress wave in cylindrical shell. Moreover, the eigensolutions are numerically solved by using the bifurcation theory of dynamic buckling. In the numerical computation, the influence factors of critical buckling load and the occurrence and development of buckling modes are discussed.

Multi-floater-mooring coupled time-domain hydro-elastic analysis in regular and irregular waves

In this study, a time-domain hydro-elastic model is developed to solve the floater-connector-mooring coupled system. The frequency-domain model is first devised with the discrete-modulus-based method in which the deformable floating structure is modeled with multiple rigid bodies connected by high-order beam elements. The corresponding multi-body hydrodynamic coefficients and loads are estimated by 3D potential theory with the coupling stiffness matrix based on the theory of the Euler-Bernoulli beam and Saint-Venant torsion. The time-domain hydro-elastic model with mooring dynamics is then subsequently developed with multi-body Cummins equation with high-order rod-FE (Finite Element) mooring elements connected to relevant floaters. The present frequency- and time-domain models are validated through comparisons with published experimental and frequency-domain results for a VLFS (Very Large Floating Structure) without mooring lines. The present method directly solves the hydro-elastic problem with mooring lines without using the conventional modal superposition method, for which wet modes with mooring need to be obtained in a priori through cumbersome iterations. The developed hydro-elasticity model is also very useful when complex inner structure-connection conditions, such as discontinuity by multiple hinged joints, are involved. Such an example is also numerically tested, and reliable results are obtained. Vertical flexible displacements, bending and torsional moments, shear forces, and mooring tensions in regular and irregular wave conditions are systematically analyzed and compared with rigid-body and without-mooring cases.

Macro modeling of slab-column connections in progressive collapse with post-punching effect

In this paper, macro-modeling methods of the slab-column connections were suggested to predict their post-punching behavior. These modeling techniques can be used to evaluate the potential for progressive collapse of flat slab buildings. It is acknowledged that structural damage is primarily focused on the flat slabs at their slab-column connections. In the suggested model, shell elements were used to simulate the plate and beam connector components to simulate punching failure. Six load-deformation curves were implemented with linear and nonlinear behaviors to simulate bending, shear, torsion, and axial force of the beam connector components to model the inner forces transfer between the slab and the column and to study the action of the connections. Two methods of macro modeling for simulating post-punching behavior were presented: rebar-modeling, link element modeling. The rebar or link element is placed vicinity to the connector beam element and activated after the punching failure. A bilinear load-deformation curve for the link element is defined to simulate post-punching behavior. Some of the parameters used to introduce these curves are calibrated with the test results. Test specimens validated the proposed methods. The results show that both post-punching behavior modeling techniques have acceptable accuracy in predicting post-punching strength, post-punching stiffness, and deformation capacity.

Features of the bridge span performance when shifting the axis of the rail-sleeper grid

Engineering structures form an integral part of the railways, both already operated and yet designed. The joint work of the upper structure of the railway track and the supporting structures of the bridge crossing is an important condition for the normal operation of the railway section without various restrictions and additional work on the current maintenance and diagnostics of structural elements. Presented study is devoted to the investigation of the stress-strain state of a small railway bridge with a beam design, when the axis of the rail-sleeper grid relative to the axis of the bridge is shifted by an amount exceeding the limit value determined by regulatory documents. In the analytical calculation of the behavior parameters and the state of the span under the action of the load, a differential equation is used that describes the vertical vibrations of the beam and allows considering them as a combination of forced and free vibrations. In numerical modeling, the finite element method is used as the solution method, the deter mining equations of which contain linear and angular displacements of nodes of the calculation scheme as unknowns. As a result of the calculations, graphical dependences for normal and horizontal displacements, internal forces, principal and equivalent stresses at various points of the span are obtained. Presented values show an increase in bending and torsional forces, as well as principal stresses when the axis of the railway track is displaced relative to the axis of the bridge. It is noted that although the increase in stresses (by about 6 %) can generally be considered insignificant, the presence of defects in the span beams (concrete chips, cracks in the stretched zone, exposure and corrosion of working reinforcement, decrease in the calculated cross section, leaching of cement stone from concrete, decrease in concrete strength over time) can make it a significant enough factor limiting the operational capabilities of bridge crossings.

Arm-wrestling injuries – A systematic review of the medical literature

Background: Arm wrestling is a popular sport due to its simplistic nature and great appeal in popular culture. Unfortunately, it can lead to serious fractures. An understanding of these injuries and its mechanisms is vital to the undertaking of safe practice methods for this sporting modality. Objectives: This study aimed to review articles that demonstrate case reports about arm-wrestling related fractures. Methods: PubMed’s database was searched with the keywords “Arm Wrestling,” Arm-wrestling,” and “Armwrestling.” Ofthe 34 articles found, 11 were fit to compose this review, being grouped into studies that dealt with adults and studies that dealt with adolescents. Results: Of the 63 adult subjects reported, 62 suffered fractures of the distal third of the humerus, occasionally accompanied by butterfly fractures and radial nerve palsy. Of the 22 adolescent subjects reported, 20 suffered fractures of the humerus medial epicondyle, never accompanied by butterfly fractures, and sometimes accompanied by ulnar nerve palsy. All injuries stemmed from unbalanced torsional forces suffered by the humerus from its own musculature. Conclusions: The injury profile presented by both populations is very homogeneous between the two different groups, which leads us to believe that correct technique can be a great ally in arm wrestling injury prevention. Athletes, as well as common practitioners, should be coached as to avoid these unfavorable positions and techniques

Comparing Measured Torsional Stress and Excitation Force under Steady State and Transient Conditions

Comparing Measured Torsional Stress and Excitation Force under Steady State and Transient Conditions

Role of Position of Shear Wall in Reducing Torsion & Storey Displacement in an Irregular Building

The paper elaborates the study of effects of location of shear wall in an irregular shaped building. The main concerned issue is the generation of torsion in a building which is irregular in plan. The paper points out the causes, effects and solution of the torsional forces in an irregular shaped building. The study is done on an ‘L’ shaped building which G+10 storied and is located in Seismic Zone IV exhibiting medium soil conditions and a damping of 5%. The modelling and analysis will be performed by using CSI ETABS ver.16. Dynamic Analysis is conducted in order to study the topic. The paper will finally point out the reasons for choosing a particular test model which exhibits lowest torsion and storey displacement.

Effect of plate configuration on resistance in mandibular angle fractures

Aim: This in-vitro experimental study compared the biomechanical behaviors of three single-miniplate osteosynthesis configurations used in the treatment of mandibular angle fractures.
 Methodology: Twenty-one synthetic polyurethane hemimandible replicas including the medullar and cortical portions were used in this study. The replicas were divided randomly into three groups (n = 5/group). Data from the three groups were compared using analysis of variance and the Tamhane T2 test. P values < 0.05 were considered to indicate significance. The replicas in all groups were fixed with 7-mm-long self-tapping screws and 2.0-mm four-hole miniplates in three different configurations external oblique, lateral angulus superior and lateral angulus inferior configuration.
 Results: The replicas were tested on a servohydraulic apparatus, and the data were transmitted to a computer for analysis of peak displacement and peak force. Peak load and peak displacement did no differ significantly among the three groups..
 Conclusion: This experimental study showed that the torsional forces resulting from the fixation of miniplates for the treatment of mandibular angle fracture did not differ among the three configurations tested.
 
 How to cite this article: Polat ME, Ghahramanzadeh asl H, Yanık S. Effect of plate configuration on resistance in mandibular angle fractures. Int Dent Res 2020;10(1):6-11. https://doi.org/10.5577/intdentres.2020.vol10.no1.2
 
 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Self-Drilling Versus Self-Tapping Screws: A 3D Finite Element Analysis.

Self-tapping and self-drilling screws are two modalities available for plate fixation. When compared to self-drilling, self-tapping screws have a few drawbacks like screw loosening, thermal osteolysis, equipment dependent, and time-consuming. The aim of this study was to compare the efficacy of self-tapping and self-drilling screws with relation to plate retention and stability in internal fixation of mandibular fractures using 3D finite element analysis (FEA). The objective of this study was to determine the influence of screw placement technique on stress concentration and deformation occurring at the screw-bone interface in self-drilling and self-tapping screws. A 3D computer-aided design modeling system was used to build a trilaminate mandibular bone, self-tapping screw and self-drilling screw, and a 2-holed miniplate with gap that were converted into finite element models using Hypermesh 13.0 software. Material properties and boundary conditions were assigned to these models. Pullout, torque, and torsional forces were applied to evaluate the stress concentration and deformation at the screw-bone interface. The comparison of stress concentration and deformation values between the two types of screws was interpreted using ANSYS software version 14.5. Results of torque test, pullout test, and torsional test showed maximum Von Mises stress, and deformation around the screw-bone interface was higher in self-tapping screw than in self-drilling screw. Within the limitations of the 3D FEA, the findings provided significant evidence to suggest that self-tapping screws have a greater incidence of fatigue when compared to self-drilling screws as there was more stress distribution and deformation at their screw-bone interface.

Optimum design of the double roll rotary forging machine frame

Abstract. The equipment to realize the rotary forging technology is called the rotary forging machine. Compared with the common forging equipment, machine frame will bear a large torsion force in the working process, and the load in the forming process will eventually act on the rotary forging machine frame, and cause it to deform, thus affecting the rolling situation of the workpiece. Therefore, good frame performance is the premise to achieve stable rotary forging. The good performance of the frame is closely related to the structural design and structural optimization. However, at present, there are few researches on the overall optimization design of the rotary forging machine, and the lightweight technology has become the current trend. In the early manufacturing of low tonnage rotary forging machine, the lightweight design is not paid enough attention to, even if it meets the use performance, but the machine is bulky, which seriously reduces the utilization rate of materials and increases the manufacturing costs. In this paper, based on the existing rotary forging machine, the topological optimization of the main body of the rotary forging machine is carried out, and then the sensitivity analysis of the thickness of each component of the machine frame to the performance of the frame is studied, which provides the basis for the follow-up size optimization. Finally, the experimental verification is carried out, and it is found that the work pieces of the rotary forging are relatively good, which shows that the optimization scheme is reasonable and can be reduced on the premise of satisfying the performance weight, saving manufacturing cost.

To evaluate the functional and radiological outcome of compound tibia shaft fracture treated with primary interlocking nail

Introduction: The Tibial shaft fracture are most common seen in road traffic accidents, Degree of displacement of fractures, degree of comminution, signs of infection and severity of soft tissue injury are the most important prognosis factors. Nail is a load sharing device with stiffness in both torsional and axial forces. Least damage to soft tissues is done by closed interlocking nailing. Aim: To evaluate the functional and radiological outcome of Compound Tibia shaft fracture treated with primary interlocking nail. Method: The present study was conducted in the department of Orthopaedics of SRMS-IMS, Bareilly from 2017-2020 on 20 patients, Extra articular Open tibia fractures with/without fibula fracture, Age above 18 years, Grade I, II & IIIA (Gustilo Anderson’s classification). Exclusion criteria: Open Tibial fracture treated primarily with external fixation, Non union of tibial fractures, Intra-articular fractures, Closed tibial fractures, Grade IIIB & IIIC fractures (Gustilo Anderson’s classification). standard surgical procedure of intramedullary interlock nailing of tibia was done. regular follow up was done with clinical and radiological assessment and final results made using Modified Ketenjian and Shelton Criteria. Result: 85% of the cases were male, with 55% grade 1, 40% grade 2 and 5% grade 3A. 60% cases were due to RTA. 55% of cases had middle third fracture tibia,70% of cases were operated within 48 hours, the mean union time was 20 weeks by then full weight bearing walker walking was started. 20% of patient showed superficial infection which got resolved by regular dressing, with 1 case of delayed union and 2 cases of stiffness. at the end of 6 months 70% showed excellent, 25% good and 5% satisfactory results. Conclusion: The fractures in our study united in an average of about 20 weeks. This one time procedure of Interlocked intramedullary nailing done which lead to union in almost all the cases. This procedure allows earlier fracture union hence early weight-bearing. Because of the high union rate and low infection rate, we consider closed interlocking nailing as the best mode of treatment for compound diaphyseal tibial fractures upto Gustilo-Anderson grade 3A.

Analysis of Human Bone, Implants and Development of Artificial Bone by Rapid prototyping (3D Printing) Technology

The replacement of damaged bone is done by design of bone then analyzing its properties, In Human body Bone plays important role in body. Which support & protect body parts. Bones comes in a variety of shapes and sizes and has complex internal and external structure. During daily activities, the skeletal system is subjected to a complicated loading exerted by the different loading conditions. Such loading modes for femur bones are include tensile, compressive, bending, and torsional forces applied to the bones of the skeletal system. In this project we have done FEA Analysis with different materials like Stainless steel, Titanium, ABS, PLA and develop artificial bone by 3D printing technology. The aim of this work is analysis & manufacture femur bone which can replace characteristics. Then it is to be printed by 3D Printer as prototype model.

Effect of elbow implant design parameters on loosening: A finite element analysis

Loosening of an implant is the main complication after total elbow arthroplasty. The design parameters of the implant are a factor that contributes to the loosening of the implant. In this study, the correlation of loosening and geometry of the elbow implant component was investigated using the finite element method. Image processing software was used to construct elbow bones. Humeral and ulnar components were modeled with various cross-sections and flanges using modeling computer-aided design software. Modeling of all stems was based on conventional cemented fixation. Axial torsion and Anterior-posterior force were applied to the articular surface. Zero-displacement was applied to the proximal humerus and distal ulna. Bone graft was used between the flange and distal humerus bone. The stress shielding of bones and micro-motion were obtained in cement-implant-bone interfaces. Results showed that humeral and ulnar stems with modified diamond cross-section observed less micro-motion in the cement-bone-implant interfaces and as well as the least stress shielding in the distal humerus and proximal ulna compared to others. Furthermore, the modified flange, concave, transferred the least micro-motion to the bone-cement-implant interface and less stress shielding in distal humerus in comparison with trapezium and rectangular ones. This computational analysis represented a step in quantifying the role of interface micro-motion stress shielding of bone in initiating elbow implant loosening. A reduction of micro-motion and stress shielding through design modifications may improve the clinical outcomes.

Biomechanical Effects of Four Different Configurations In Salter Harris Type 4 Distal Femoral Epiphyseal Fractures

In this study, the biomechanicaleffects of four different configurations (Parallel K wires, Parallel Screw, Upper K wire-Lower Screw, Upper Screw-Lower K wire), which are used for stabilizing Salter-Harris (SH) Type 4 epiphyseal fracture of distal femur after reduction process, on the epiphyseal plate has been investigated under axial, rotational and bendingforces in order to determine the most advantageous configuration. The fourdifferent configurations have been modeled by using SolidWorks and computer-aided numerical analyses were performed by finite element analysis software. The mesh process, boundary conditions and material model have been applied in finite element analysis software for each configuration. In addition, von-Mises stress values on epiphyseal plate, screws and K wires have been calculated. There is a general near trend on stress values in all configurations on physis line under bending (varus-valgus angulation, anterior-posterior angulation) and torsional forces in the frontal, sagittal and transverse plane respectively. Considering the axial forces, the highest stress was found on parallel K- wires configuration in physis while the lowest stress was found in parallel screw configuration. It has been found particularly advantageous to use fixation type in parallel screw configuration. In addition, in SH type 4 epiphyseal fracture, fixation type is found to be disadvantageous in K wire configuration.