1,721,218 research outputs found
On contact between three-dimensional beams undergoing large deflections
No full textContact between three-dimensional beams which undergo large motions is considered. To formulate the associated constraint conditions the point of contact has to be detected within the beam. Once this is known the contact constraint has to be formulated for a given beam discretization and the associated contribution to the weak form has to be developed. Also, consistent linearization of the contact contribution is derived, which is needed within Newton's metho
Application of augmented lagrangian techniques for nonlinear constitutive laws in contact interfaces
No full textThe use of micromechanically based constitutive equations for contact interfaces leads to technically relevant parameters to ill-conditioned finite-element equations. In the paper an augmented Lagrangian technique is employed to overcome this difficulty and to provide a good converging algorithm
A segment-to-segment contact strategy
No full textthis paper, a method is proposed to define the geometrical contact constraints. Within this treatment one has the possibility to define locally the contact parameters for an accurate treatment of contact constraints. Local values of the geometrical variables can be determined at the integration points, hence the method permits to integrate contact constitutive laws along contact segments.
The weak form for this new formulation is developed. Furthermore, also the consistent linearization is carried out. Finally a technique is proposed to reduce the large number of terms involved. In this case, an almost consistent tangent stiffness is determined. @ 1998 Elsevier Science Ltd. All rights reserved
Thermomechanical contact - a rigorous but simple numerical approach
No full textA contact element which deals with mechanical and thermal fields is presented. The geometrically linear formulation leads to an algorithm which is on one hand very simple to code, but on the other hand very efficient and yields deep insight into the real physical behaviour of contact conductance. The presented formulation permits to add the contact algorithm to any finite element code
A method for solving contact problems
No full textIn this paper a further method is presented to solve problems involving contact mechanics. The basic idea is related to a special modification of the unconstrained functional to include inequality constraints. The modification is constructed in such a way that minimal point of the unconstrained potential can be exactly shifted to the constraint limit. Moreover, the functional remains smooth and the admissible range of the solution is not restricted. The solution search process with iterative techniques takes advantage from these features. In fact, due to a better control of gap status changes, a more stable solution path with respect to other methods is usually obtained.
The characteristics of the method are evidenced and compared to other classical techniques, like penalty and barrier methods. The finite element discretization of the proposed method is included and some numerical applications are shown
Trends in Computational Contact Mechanics
No full textContact mechanics is a science that has a great impact on everyday life and is present in many different fields. These include civil, mechanical and environmental engin- eering, but also medicine since locomotion as well as functional joints do not work without friction. In one application friction is needed – like traction of car tyres – and in another application friction produces wear and costs – like in bearings. Thus it is of the utmost interest to have reliable and efficient methods and associated ana- lysis tools that can be applied to a vast range of contact problems.
Using the power of today’s computers many complex contact problems can be solved with numerical simulation tools. Despite the progress that has been reached with respect to the implementation of contact algorithms in commercial codes, vivid research is still going on in the area of contact mechanics. Thus, within the last years, computational contact mechanics has been a topic of intense research. The aim of the development is to devise robust solution schemes and new discretization techniques, which can be applied to different problem classes in engineering and science.
These are wide-ranging and include computational aspects of discretization tech- niques using finite and boundary element methods. Special solution algorithms for single- and multi-processor computing environments are of great interest for efficient solutions. Furthermore, multi-scale approaches have been applied suc- cessfully to contact problems and multi-field formulations were used for thermo- mechanical or electro-thermo-mechanical applications involving contact. Discrete element models include always contact and pose a challenge for the numerical treat- ment due to the high number of particles. Finally, problems like rolling wheels and tyres need special contact formulations and special algorithmic approaches.
Technical applications incorporate different interface problems. Examples are failure processes in heterogeneous materials, textile and laminated composites, in- teraction between road and tyres, hip implants or artificial knee joints as well as spraying of particles on surfaces and impact analysis of cars.
The present book summarizes work in the area of computational contact mechanics that was presented at the 1st International Conference on Computational Contact Mechanics in Lecce, Italy. The authors discuss different theoretical methodologies, algorithms for the solution of contact problems and apply these to different engineering problems
Effective elastic properties of heterogeneous materials with imperfect finite thickness interfaces
No full textFinite strain response of crimped fibers under uniaxial traction: An analytical approach applied to collagen
No full textComposite materials reinforced by crimped fibers intervene in a number of advanced structural applications. Accordingly, constitutive equations describing their anisotropic behavior and explicitly accounting for fiber properties are needed for modeling and design purposes. To this aim, the finite strain response of crimped beams under uniaxial traction is herein addressed by obtaining analytical relationships based on the Principle of Virtual Works. The model is applied to collagen fibers in soft biological tissues, coupling geometric nonlinearities related to fiber crimp with material nonlinearities due to nanoscale mechanisms.Several numerical applications are presented, addressing the influence of geometric and material features. Available experimental data for tendons are reproduced, integrating the proposed approach within an optimization procedure for data fitting. The obtained results highlight the effectiveness of the proposed approach in correlating fibers structure with composite material mechanics
On augmented lagrangian algorithms for thermomechanical contact problems with friction
No full textThe detailed discretization of contact zones with contact stiffness based on real physical characteristics of contact surfaces can produce stiffness terms which induce ill-conditioning of the global stiffness matrix. Moreover the consistent treatment of frictional behaviour generates non-symmetric tangent stiffness matrices due to the non-associativity of the slip phase. Other non-symmetries are due to the coupling terms and to the dependencies on various parameters that can be involved. To overcome these difficulties almost consistent techniques based on two-step algorithms have been proposed in the past. Here an augmentation technique is proposed which takes into account micro-mechanical effects, and permits the symmetrization of the tangent stiffness during frictional slip phase
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