Papers by Keyword: Frictional Contact

Abstract: Displacement can occur for a variety of reasons, including pedicle screw detachment from the spine, damaged pedicle screws, the supporting rod detaching from the pedicle screw, and broken supporting rods. The relationship between displacement and screw threads indicates that the displacement of the screw is a measure of thread movement, and the smaller the pitch (the space between the two screw threads), the lower the displacement of the screw. Results from a normal bone simulation using MSC-Marc show that variations in pedicle screws under tensile load result in a displacement of 5.53x10-5 mm for single-threaded conical pedicle implants, with no greater coefficient of friction than single-threaded cylindrical implants, which have a displacement of 1.62x10-6 mm. When a tensile load is applied to an osteopenia bone, a single-threaded conical implant with no coefficient of friction results in a displacement of 3.45x10-5 mm as opposed to a cylindrical implant. The higher contact force reinforces the pedicle screw's interface with the bone, making it less likely to detach due to the pedicle screw's tensile force. When applying tensile forces and bending moments to a single-threaded conical implant with a single-threaded cylindrical implant, the displacement increases as the friction coefficient rises

Abstract: Piezoelectric materials exhibit an electromechanical coupling which allows for their use assensors or energy harvesting devices (direct piezoelectric effect) or actuators and shape control de-vices (inverse piezoelectric effect). They are applied in many technological sectors of current interestsuch as the aerospace and automotive industries, and they are generally constructed in block form orin a thin laminated composite. The study of the integrity of such materials in their various forms andsmall sizes is still a challenge nowadays. To gain a better understanding of these systems, this workpresents a crack surface contact formulation which makes it possible to study the integrity of theseadvanced materials under more realistic crack surface multifield operational conditions. The formu-lation uses the BEM for computing the elastic influence coefficients and contact operators over theaugmented Lagrangian to enforce contact constraints on the crack surface, in the presence of electricfields. The capabilities of this methodology are illustrated solving a benchmark problem.

Abstract: The results of vibration signals control the processing of conductive ceramics EDM machines. It has been shown that the processing of ceramics has a number of features, which was successfully controlled with the help of additional monitoring of high-frequency vibrations.

Abstract: The contact problem with Coulomb friction together with a simple Kelvin-Voigt viscoelastic model is studied. The numerical solution is obtained using a time discretization by a semi-implicit formula, the visco-elastic solids in contact being discretized by Symmetric Galerkin Boundary Element Method (SGBEM). The resulting minimization problem with a nonsmooth cost functional is suitably transformed in several ways. Firstly, a transformation is performed to apply SGBEM without any viscoelastic fundamental solution. Secondly, a transformation of contact quantities leads to a minimimization with a quadratic programming structure. Numerical examples show the applicability of the proposed approach to solve rather intricate frictional contact problems.

Abstract: According to a recent development of environmental geotechnical engineering, geotechnical engineering environment connotation , characteristics, and related disciplines aspects of the relationship are summarized and explained. The definition proposed environmental geotechnology views, a brief analysis of urban construction in common environmental geotechnical problems and propose appropriate countermeasures . Finally, emphasize the potential environmental geotechnology great, to be able to further develop and improve in theory and in practice.

Abstract: Relations between different solutions of an interface crack in a neighborhood of the crack tip given by the open model, frictionless and frictional contact models of interface cracks are analyzed numerically for a penny-shaped interface crack subjected to remote tension. A new analytic expression for the size of the near-tip contact zone in presence of Coulomb friction between crack faces is proposed in the so-called case of the contact zone field embedded in the oscillatory field.

Abstract: This paper is devoted to the analysis of frictional contact problems with large deformations and displacements between hyper-elastic body and rigid body. The material nonlinearity and contact nonlinearity are separated and, the geometrically nonlinear behavior is described by the total Lagrange formulation. The Coulomb friction law is employed to simulate the friction between rigid vessel and rubber by the use of augmented Lagrange approach with node-to-segment formulation. A formulation of finite element is taken in this paper to describe the frictional contact problem, which is solved by the Newton-Raphson iterative procedure. It is shown that the augmented Lagrange technique significantly avoids locking and over-constraining and provides optimal convergence rate. Finally, the numerical results show that the accuracy and efficiency of augmented Lagrange approach in modeling large deformation frictional contact problem.

Abstract: This contribution proposes to model thixoforming processes using the eXtended Finite Element Method (X-FEM). The X-FEM is very suitable for modeling forming processes with complex tool geometries as the mesh does not need to conform with the boundary of the structure. Even if the use of the X-FEM helps to describe the boundary position, the mesh still deforms when the structure is stressed. To avoid mesh distortions that appear in large deformation analysis, an Arbitrary Lagrangian Eulerian formulation is used (ALE) [3].

Abstract: In this paper the servo drive with friction wheels is presented. The servo drive is designed to move the automatic laparoscope tool or laparoscope camera (thereinafter laparoscope sleeve or sleeve) in two Degrees of Freedom (DOF). The description of the drive mechanism, operating principle and mathematical model of this drive is presented. Based on this model, the Control System (CS) has been created, and used to the construction of a simulation model. The simulation illustrates the proper functionality of the mathematical model of the servo drive with the described CS. This paper also presents the servo drive test stand and the most important examination results from the point of view of using them in the cardiac surgery Robin Heart robot.

Abstract: The main objective of this paper is to present a theoretical and numerical analysis of frictional contact problems for large deformation elasto-plastic based on the finite element method (FEM) and the mathematical programming. The study is done on an elasto-plastic material obeying to the von Mises criterion. The Coulomb’s friction contact is used to implement the frictional boundary conditions and is formulated by the bipotential concept leading us to minimize only one variational principle of minimum in displacement. In order to follow up the sequences of large deformations, we have used the sequential analysis procedure; it consists in the updating of material properties and geometrical configuration after each sequence.