Condition Of Traction Research Articles

Thickness-extensible higher order plate theory with enforced C1 continuity for the analysis of PEEK medical implants

Plate-like structures had been thoroughly studied in literature over years to reduce the computational space from 3D to 2D. Many of these theories suffer either from satisfying the free traction condition or thickness extensibility in addition to the consistency of transverse shear strain energy. This work presents a higher order shear deformation thickness-extensible plate theory (eHSDT) for the analysis of plates. The proposed eHSDT satisfies the condition of free traction as other theories do but it also satisfies the condition of consistency of transverse shear strain energy which is neglected by many theories in the area of plates and shells. The implementation of the proposed theory in displacement-based finite element procedure requires continuity of derivatives across elements. This necessary condition was achieved using the penalty enforcement method for derivative-based nodal degrees of freedom across the standard 9-nodes Lagrange element. The theory was tested for elastic bending deformation of Polyether-ether-ketone (PEEK) which is one of the basic materials for medical implants. The theory showed good accuracy compared to experimental data of the three-points bending test. The present eHSDT was also tested for different conditions with a wide range of aspects ratios (thin to thick plates) and different boundary conditions. The accuracy of the proposed eHSDT was verified against exact solutions for these conditions which showed the advantage over other approaches and commercial finite element packages.

Simulation of passenger movement dynamics in a vehicle

A feature of the braking dynamics of a road train is the occurrence of shock loads between its links, which under certain conditions can significantly impair its stability. At the same time, there is a significant increase in dynamic loads on the support-coupling device, the destruction of which can lead to an emergency situation. It is suggested to use computer modeling in addition to bench tests to diagnose the condition of traction and coupling devices. It makes it possible not only to duplicate field tests, but also to reduce their costs, to apply methods of theoretical forecasting and determination of the strength of units of traction and coupling devices of trailers and towed vehicles. In the case of a semi-trailer, the impact of the tractor is modeled taking into account the initial lateral stiffness of the pivot pin, which indicates the elasticity of the suspension, tires, chassis and support-coupling device of the tractor-trailer on the level of the ground surface. The load on the finger of the hinged-coupling device during computer modeling was estimated by the amount of stress concentration on the surface of the finger. The greatest local stresses were observed in the area of the finger's phalanx, and the maximum deformation of the finger did not exceed 0.061 mm. Bench tests with the same tensile test force as in the calculation method showed that the difference in the values obtained by these two methods was 10-3 mm, which is included in the permissible measurement error (± 1.6•10-3 mm). The combination of bench tests and computer modeling is also relevant at the design and testing stages of agricultural, forestry and special purpose vehicles and machines.

The effects of aligner anchorage preparation on mandibular first molars during premolar-extraction space closure with clear aligners: A finite element study

This study aimed to determine the effectiveness of different aligner anchorage preparations on mandibular first molars during premolar-extraction space closure with clear aligners and to assess the effects of different modes of Class II elastics on mandibular first molars. Finite element models were constructed on the basis of cone-beam computed tomography data from an orthodontic patient. The models comprised maxilla, mandible, maxillary and mandibular teeth without first premolars, periodontal ligaments, attachments and aligners. Tooth displacement tendencies were calculated using different aligner anchorage preparations and Class II elastics on the models from the same patient. Three group sets were designed on the basis of the positions of aligner cutouts and buttons (mesiobuccal, distobuccal and lingual). Four groups were established in each of the 3 group sets. Four groups were created: (1) no elastic traction+ no anchorage preparation, (2) anchorage preparation only, (3) elastic traction only, and (4) elastic traction+ anchorage preparation. Different aligner anchorage preparations (0°, 1°, 2°, 3°) were applied on mandibular second premolars and molars. The Class II traction force was set to 100 g. With clear aligners, mandibular first molars were subject to mesial tipping, lingual tipping and intrusion. In the condition of no elastic traction, aligner anchorage preparation resulted in distal tipping, buccal tipping, and extrusion effect on mandibular first molars. Aligner anchorage preparation was more effective in the distal and lingual cutout groups than in the mesial cutout group. In the condition of Class II elastic traction, the bodily movement of mandibular first molars was achieved with a 3° anchorage preparation for the mesial cutout group and a 1.7° anchorage preparation for distal and lingual cutout groups. Absolute maximal anchorage was achieved with a 2° anchorage preparation for distal and lingual cutout groups. Clear aligner therapy caused mesial tipping, lingual tipping and intrusion of mandibular first molars during premolar-extraction space closure. Aligner anchorage preparation effectively prevented mesial and lingual tipping of mandibular molars. Distal and lingual cutout modes were more effective than mesial cutout modes in aligner anchorage preparation. For each aligner stage (0.25 mm), 1.7° aligner anchorage preparation and Class II elastics with distal or lingual cutouts led to the bodily movement of mandibular first molars, whereas 2° anchorage preparation reached absolute maximal anchorage.

ANALYSIS OF TACTION TRANSMISSION OF RAILWAY VEHICLES AND THEIR DYNAMIC CHARACTERISTICS

In the article, traction transmissions of railway vehicles, which are an important component of the transport industry, are studied. Dynamic events in the functional chain, as the main factors that ensure the structural condition of the main parts of the mechanical system, the longevity of the system, effective measures to improve the operation of the service, effective measures to improve the performance of the structures, the operation of improved structures, the in-depth determination of maintenance and repair technologies, as well as the service outstanding features. The relevance of technical quality assessment is justified by the development of an innovative model. The condition, construction and operation of modern traction drives are explained. Experimental studies are underway and have strong implications for transmission control. With the device that checks the possibilities of using defectoscopic methods, the cases that caused rejections were determined.

Evaluating the energy storage capabilities of forklift actuator

Energy saving in construction and logistics is a topical and open issue today. Forklifts are one of the main self-propelled means of mechanization of warehouses, in which the effect of energy recovery can be applied. This is due to the peculiarity of such systems that operate in overclocking and braking modes. The purpose of this work is to study the energy consumption in the drive system of the loader based on the analysis of the sequence diagram of its operation for given sections of movement. Methodology. The equation of traction balance of a wheeled machine is used to estimate energy consumption at given sections of the load movement. Determination of the kinematic parameters of the loader system with the load is determined from the condition of maximum traction. Results. The mass characteristics of the system, speed of movement, characteristics of the road surface contribute to the formation of the energy return by the system of the loader in the process of its braking. Increasing operating speeds will have a positive effect on energy savings in energy storage systems. Analysis of energy consumption during the operation of the loader shows that in the process of its operation you can effectively store from 30 to 70% of energy. Originality. This study uses an engineering assessment approach that will be useful for practical applications in the design of such systems. Practical value. In this study, the sequence diagram of the energy consumption of a forklift when working with loads of 2000 kg, 1000 kg and 500 kg is essential. The sequence diagram method is simple and can therefore be easily implemented in forklift control systems to enable energy recovery systems.

Design of a DSP-Based Real-Time Control Device for Railway Vehicle Simulation

A real-time control device for railway vehicle simulation is designed in this study according to the experimental requirements of a railway vehicle electric traction and electric braking system. The device uses the high-speed processing characteristic of DSP and runs on the basis of both DSP and the corresponding experimental platform. The simulation experiment for a different power grade traction system is achieved through control of the device. Full static and dynamic simulation of the operating condition of the train electric traction and braking system is attained in the case of no commissioning.

Classification and surgical treatment of basilar invagination

Objective To present a new classification of basilar invagination (BI) and evaluate guiding use and effect of the classification for the treatment of BI. Methods Consecutive 34 patients with BI were surgically treated in our department from July 2000 to June 2013. There were 17 males and 17 females, aged from 7 to 59 years (mean, 34.5 years). The clinical symptoms and signs were recorded, and preoperative imaging examination including anteroposterior, lateral, dynamic X-rays, MRI, CT and 3-dimensional reconstruction views of cervical spine were performed to identify the series. 34 patients with BI were associated with anomalies including atlantooccipital assimilation in 21 cases, C2-3 fusion in 16 cases, and atlantoaxial dislocation in 24 cases. According to with or without atlantoaxial dislocation, BI was classified into Type I with dislocation in 24 cases and Type II without dislocation in 10 cases. Type I was divided into reducible subtype A in 6 cases and irreducible subtype B in 15 cases under the condition of skull traction. Type I was performed with reduction by traction or release between C1-2 through anterior or posterior approach, while Type II with decompression by resection abnormal structures through anterior or anteroposterior approach. All patients were underwent posterior instrumentation and fusion. The postoperative X-rays, MRI or CT was taken to observed the results of decompression, fixation and fusion. Neurological function was assessed by JOA scale and Ranawat's score. Results The average operation time was 210 min, and blood loss was 240 ml. Except for 2 death cases, 32 cases were followed up, and the followed-up was ranged from 11 to 37 months (mean, 17.4 months). JOA scores increased from 8.4 to 14.6 with 71.1% of recovery. The excellent and good rate was 72.4%. According to Ranawat's score, preoperative score was class II in 11 cases,class IIIA in 17 cases and class IIIB in 6 cases, while postoperative score was class I in 20 cases, class II in 11 cases and class IIIA in 1 case. The perioperative complications was present in 9 cases, including infection in 3 cases, cerebrospinal fluid (CSF) leakage in 2 cases, respiratory dysfunction in 2 cases, vertebral artery injury and cleft palate in 1 case. Conclusion The new classification of BI can effectively guide and schedule the treatment. Careful evaluation,operation and prevention of perioperative complications are important to ensure the success of surgery. Key words: Skull base; Atlanto-occipital joint; Atlanto-axial joint; Dislocations; Spinal fusion

A nonlinear elastic deformable template for soft structure segmentation: application to the heart segmentation in MRI

This paper proposes a nonlinear 3D deformable model for the image segmentation of soft structures. The template is modelled as an elastic body which is deformed by forces derived from the image. It relies on a template, which is a topological, geometrical and material model of the structure to segment. This model is based on the nonlinear three-dimensional elasticity problem with a boundary condition of pure traction. In addition, the applied forces are successive, as they depend on the displacements. For computations, an incremental algorithm is proposed to minimize the global energy of template deformation. Sufficient conditions of the convergence for the incremental algorithm are given. Finally, a discrete algorithm using the finite element method is presented and evaluated on synthetic images and actual MR images of mouse hearts.

The effect of an elastic triangular inclusion on a crack

The interaction between an elastic triangular inclusion and a crack is investigated. The problem is formulated using the boundary integral equations for traction boundary value problems derived by Chau and Wang as basic equations. By using the continuity condition of traction and displacement on interface as supplement equations, a set of equations for solving the interaction problem between an inclusion and a crack are obtained, which are solved by using a new boundary element method. The results in terms of stress intensity factors (SIFs) are calculated for a variety of crack-inclusion arrangements and the elastic constants of the matrix and the inclusion. The results are valuable for studying new composite materials.

Control System of Permanent Magnet Synchronous Motor for Railway Vehicle Traction.

The application of a permanent magnet synchronous motor (PMSM) has been studied for railway vehicle traction in order to reduce the weight and size of direct drive traction motors. As a part of this study, it is required to establish a current control system of PMSM suitable for railway vehicle traction. This article discusses the current control system mentioned above and suggests a method which is available under the condition of railway vehicle traction. Next, an investigation is conducted on how to decide the current response time constant. The article will also show that the suggested traction control system is sufficient in practical use through an analysis of operating status under the condition of actual railway vehicle traction.

On interface dislocations between dissimilar materials with non-linear stress–strain laws (Plane strain)

A plane analysis of a dislocation on the interface of dissimilar materials is considered where one material is linear and the other deforms according to a power law hardening (N<1) or softening (N>1) stress–strain relation. N>1 and 0<N<1 are considered separately as two distinct cases. For case N<1, the modulus tends to zero near the dislocation core in the non-linear medium and thus, to leading order, the linear medium appears to be rigid and vice versa for N>1. This gives the leading order solution of the local field. The higher order terms are derived for both media by imposing the continuity condition of traction across the interface and that of the displacement ahead of the dislocation core. The displacements near the dislocation core are found to be of different orders in different regions. Results are presented for various values of the hardening and softening parameter. The methods developed should apply to the case when both materials have non-linear stress–strain laws.

Initial‐boundary value problems for non‐linear equations of generalized thermoelasticity and elasticity

AbstractWe formulate a local existence theorem for the initial‐boundary value problems of generalized thermoelasticity and classical elasticity. We present a unified approach to such boundary conditions as, for example, the boundary condition of traction, pressure or place combined with the boundary condition of heat flux or temperature.

The role of ellipticity and normality assumptions in formulating live-boundary conditions in elasticity

Abstract : It is shown that those interactions of an elastic body B with an elastic environment E manifested by local surfacial loadings should be modelled by boundary operators featuring a live system of surfacial forces, i.e., a vector field s, defined over the boundary partial derivative of B and representing the surfacial force per unit area exerted by E over B, which depends functionally in a non-trivial way on the deformation u of B. In addition to the analytical difficulties to be expected, when normality does not hold the mechanical interpretation of boundary conditions fails to be unique. That this is indeed the case is demonstrated by producing an explicit example in linearized elastostatics of a boundary operator condition of traction or as a dead-boundary condition of frictionless contact. Keywords: ellipticity, normality, live-boundary condition of traction.

An equilibrium method for prediction of transverse shear stresses in a thick laminated plate

First two equations of equilibrium are utilized to compute the transverse shear stress variation through thickness of a thick laminated plate after in-plane stresses have been computed using an assumed quadratic displacement triangular element based on transverse inextensibility and layerwise constant shear angle theory (LCST). Centroid of the triangle is the point of exceptional accuracy for transverse shear stresses. Numerical results indicate close agreement with elasticity theory. An interesting comparison between the present theory and that based on assumed stress hybrid finite element approach suggests that the latter does not satisfy the condition of free normal traction at the edge. Comparison with numerical results obtained by using constant shear angle theory suggests that LCST is close to the elasticity solution while the CST is closer to classical (CLT) solution. It is also demonstrated that the reduced integration gives faster convergence when the present theory is applied to a thin plate.

A note on superposition in Mindlin's problem

The problem of a half-space subjected to an interior concentrated force is posed as a superposition problem. For a free plane boundary it is shown that the boundary condition of traction may be expressed directly through the normal derivative of a harmonic Green's function by means of a linear operator. These circumstances at once generate the classical result. For a clamped boundary such a procedure becomes cumbersome and direct integration, in a manner proposed by Sanders, is performed.