Search results

Finite element (FE) modeling of the human dentate mandible is the method of choice currently used for simulating structural fracture analyses in the mandibular region. A finite element model of a parasymphyseal fracture with an internal rigid fixation plate‐screw system has been developed to compare the effects of including frictionless/frictional contact boundary conditions at the fracture site. It is common practice to ignore contact boundary conditions in FE modeling of mandibular fractures due to the non‐linearities causing increased computational requirements. The stress distributions and displacements of the mandibular fracture region indicate a significant difference resulting from the introduction of realistic contact boundary conditions. These current findings suggest that even though the modeling of extreme situations, i.e. non‐contact modeling of unhealed fractures, may provide insight to non‐union problems, future mandibular fracture models should include frictional contact boundary conditions. This is in order to capture more realistic behavior of the system to be analyzed.

Contact problems are among the most difficult ones in mechanics. Due to its practical importance, the problem has been receiving extensive research work over the years. The finite element method has been widely used to solve contact problems with various grades of complexity. Great progress has been made on both theoretical studies and engineering applications. This paper reviews some of the main developments in contact theories and finite element solution techniques for static contact problems. Classical and variational formulations of the problem are first given and then finite element solution techniques are reviewed. Available constraint methods, friction laws and contact searching algorithms are also briefly described. At the end of the paper, a bibliography is included, listing about seven hundred papers which are related to static contact problems and have been published in various journals and conference proceedings from 1976.

The present paper deals with the problem of large displacement frictionless contact between a rigid obstacle and an elastic body. In Klarbring a formulation of this problem which makes use of a distance function G is given, and in Björkman the related computational scheme is presented. We give in this introduction a summary of these works, which shows the central position in the computational scheme of the function G, its gradient ΔG and its Hessian Δ2G. In the next section we present a particular distance function that is useful when, in the computational realization, the rigid obstacle is a CAD surface with continuous curvature. As an example of such a surface, we briefly present the conceptual ideas of Ferguson bicubic spline surfaces. Then a search algorithm needed for determination of the value of G during iterations is given. Finally, we present some test examples.

This paper aims to describe the application of the virtual element method (VEM) to contact problems between elastic bodies.

Polygonal elements with arbitrary shape allow a stable node-to-node contact enforcement. By adaptively adjusting the polygonal mesh, this methodology is extended to problems undergoing large frictional sliding.

The virtual element is well suited for large deformation contact problems. The issue of element stability for this specific application is discussed, and the capability of the method is demonstrated by means of numerical examples.

This work is completely new as this is the first time, as per the authors’ knowledge, the VEM is applied to large deformation contact.

The purpose of this paper is to present and analyze the iterative rules determining the impulsive behavior of a rigid disk having a single or possibly multiple frictionless impact with two walls forming a corner.

In the first part, two theoretical iterative rules are presented for the cases of ideal impact and Newtonian frictionless impact with global dissipation index. In the second part, a numerical version of both the theoretical algorithms is presented.

The termination analysis of the algorithms differentiates the two cases: in the ideal case, it is shown that the algorithm always terminates and the disk exits from the corner after a finite number of steps independently of the initial impact velocity of the disk and the angle formed by the walls; in the non-idealcase, although is not proved that the disk exits from the corner in a finite number of steps, it is shown that its velocity decreases to zero, so that the termination of the algorithm can be fixed through an “almost at rest” condition. It is shown that the stable version of the algorithm is more robust than the theoretical ones with respect to noisy initial data and floating point arithmetic computation. The outputs of the stable and theoretical versions of the algorithms are compared, showing that they are similar, even if not coincident, outputs. Moreover, the outputs of the stable version of the algorithm in some meaningful cases are graphically presented and discussed.

The paper clarifies the applicability of theoretical methods presented in Pasquero (2018) by analyzing the paradigmatic case of the disk in the corner.

The motion of systems of polygonal objects is characterized by discontinuities due to changes in the set of contacts between polygons. Effective simulations of such a motion requires a simulation scheme that can automatically update the set of contacts during the simulation. This article focuses on a contact updating problem that arises when a penalty based contact model is used. A penalty based model requires a finite overlap of contacting polygons. This overlap results in ambiguities in characterizing corner‐corner contact between polygons. A simple yet effective scheme to overcome such ambiguities is presented.

Pin-loaded hubs with fitted bush are used in industrial connector-type elements. They are subjected to varying radial forces leading to variable stress distribution. The literature provides various pressure distribution expressions adapted essentially for symmetric geometries and fixed load condition (circular hubs, half-infinite geometries, axial load, tangential load, etc.). This study aims to take into account the geometrical conditions of industrial connector-type elements and presents a model for pressure distribution based only on geometric parameters, maximal pressure and contact angle value for the case of fit pin-loaded hub.

The finite element computation for the contact problem shows that the pressure distribution of the pin-loaded hub under various inclined forces (from 0° to 180°) is a parabolic distribution. This distribution can be defined by three parameters which are θ_A, θ_B and P_max. The study assumes that the distribution is symmetric and that P_max can be modeled using force F, hub radius R, hub thickness b and the half contact angle are θ_A.

The new proposal pressure distribution parameters are easy to identify. Even for the non-symmetric pressure distribution, the study denotes that the errors on evaluating θ_A and θ_B keep the analytical model still in good agreement with finite element computations.

Only the neat fit case was studied.

Pin-loaded joints are connector-type elements used in mechanical assemblies to connect any structural components and linkage mechanisms such as connecting rod ends of automotive or shear joints for aircraft structure.

The good correlation between finite element computations and model results shows the validity of the assumptions adopted here. Analytical fatigue models, based on this stress distribution, could be derived in view of a fatigue lifetime calculation on connecting hub. Friction, pin deformation and local plastic effects under pin-loading are the main phenomena to take into account to further enrich this model.

The objective is to develop a flexible robot assembly system capable of economically switching between a wide range of product assemblies. Towards this goal, this paper introduces grasping as a principle issue in designing for flexibility in a robot system. The task, sensing, and certainty about actions are the primary factors in grasp decisions and not where to grasp the part. Identifying finger features, which satisfy a broad range of tasks reduces the likelihood of re‐tooling, and improves certainty about part location and relative orientation. Aided by the ability to address a broad range of tasks, design rules are established which assimilate grasps to part design.

Gives a bibliographical review of the error estimates and adaptive finite element methods from the theoretical as well as the application point of view. The bibliography at the end contains 2,177 references to papers, conference proceedings and theses/dissertations dealing with the subjects that were published in 1990‐2000.

The purpose of this paper is to present a new way to solve numerically a mechanical frictionless contact problem within a context of multiple sampling, frequently used to design robust structures.

This paper proposes to integrate a control-based approach, currently used in automation domain, for the solving of non-linear mechanical problem. More precisely, a fuzzy logic controller is designed to create a link between the normal gaps identified between the bodies and the normal contact pressures applied at the interface.

With this new strategy, the initial non-linear problem can be decomposed into a set of reduced linear problems solved using the finite element method. A projection built from the modal bases of each component in contact is considered to reduce computational time. Moreover, the proposed numerical applications highlight an interesting compromise between computation time and precision of contact data.

Currently, the proposed Fuzzy Logic Controller for Contact method has been developed for a frictionless contact problem in the case of 2D numerical applications. Therefore, as obtained results are very interesting, it will be possible to expand on these works in a future works for more complex problems including friction, 3D model and transient dynamic responses by adding other controllers.

In conclusion, this paper highlights the interest of studying a contact problem by considering automation approaches and defines the basis of future multidisciplinary works.