| 1. |
|
|
| 2. |
|
|
| 3. |
- Andersson, Lars-Erik, 1942-, et al.
(författare)
-
A Survey of Basic Mathematical Results for Frictional Contact Problems
- 2001
-
Ingår i: From Convexity to Nonconvexity. - Dordrecht/Boston/London : Kluwer. - 0792371445 - 9780792371441 ; , s. -392
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Contains a collection of invited papers dedicated to the memory of two great mathematicians, Gaetano Fichera and Panagis Panagiotopoulos. The book is centered around the seminal research of G Fichera on the Signorini problem, hemivariational inequalities, nonsmooth global optimization, and regularity results for variational inequatities.
|
|
| 4. |
- Andersson, Lars-Erik, 1942-, et al.
(författare)
-
Conditions for use of a non-selfintersection conjecture
- 2006
-
Ingår i: Computer Aided Geometric Design. - : Elsevier BV. - 0167-8396 .- 1879-2332. ; 23:7, s. 599-611
-
Tidskriftsartikel (refereegranskat)abstract
- Volino and Thalmann have published a conjecture proposing sufficient conditions for non-selfintersection of surfaces. Such conditions may be used in solid modeling, computer graphics, and other application areas, as a basis for collision-detection algorithms. In this paper we clarify certain of the hypotheses of the proposed theorem, and give a proof. A brief summary of possible pitfalls related to using the conditions, when the hypotheses of the formal theorem given here are not satisfied, is also given. We also give examples, and show that the theorem can be extended to domains that are not simply connected. © 2006 Elsevier B.V. All rights reserved.
|
|
| 5. |
- Andersson, Lars-Erik, 1942-, et al.
(författare)
-
Equivalence of topological form for curvilinear geometric objects
- 2000
-
Ingår i: International journal of computational geometry and applications. - 0218-1959. ; 10:6, s. 609-622
-
Tidskriftsartikel (refereegranskat)abstract
- Given a curvilinear geometric object in R3, made up of properly-joined parametric patches defined in terms of control points, it is of interest to know under what conditions the object will retain its original topological form when the control points are perturbed. For example, the patches might be triangular BΘzier surface patches, and the geometric object may represent the boundary of a solid in a solid-modeling application. In this paper we give sufficient conditions guaranteeing that topological form is preserved by an ambient isotopy. The main conditions to be satisfied are that the original object should be continuously perturbed in a way that introduces no self-intersections of any patch, and such that the patches remain properly joined. The patches need only have C0 continuity along the boundaries joining adjacent patches. The results apply directly to most surface modeling schemes, and they are of interest in several areas of application.
|
|
| 6. |
- Andersson, Lars-Erik, 1942-, et al.
(författare)
-
Error analysis for operations in solid modeling in the presence of uncertainty
- 2008
-
Ingår i: SIAM Journal on Scientific Computing. - : Society for Industrial & Applied Mathematics (SIAM). - 1064-8275 .- 1095-7197. ; 29:2, s. 811-826
-
Tidskriftsartikel (refereegranskat)abstract
- The problem of maintaining consistent representations of solids in computer-aided design and of giving rigorous proofs of error bounds for operations such as regularized Boolean intersection has been widely studied for at least two decades. One of the major difficulties is that the representations used in practice not only are in error but are fundamentally inconsistent. Such inconsistency is one of the main bottlenecks in downstream applications. This paper provides a framework for error analysis in the context of solid modeling, in the case where the data is represented using the standard representational method, and where the data may be uncertain. Included are discussions of ill-condition, error measurement, stability of algorithms, inconsistency of defining data, and the question of when we should invoke methods outside the scope of numerical analysis. A solution to the inconsistency problem is proposed and supported by theorems: it is based on the use of Whitney extension to define sets, called Quasi-NURBS sets, which are viewed as realizations of the inconsistent data provided to the numerical method. A detailed example illustrating the problem of regularized Boolean intersection is also given.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Andersson, Lars-Erik, 1942-, et al.
(författare)
-
Existence theorems for noncoercive incremental contact problems with Coulomb friction
- 2006
-
Ingår i: Analysis and Simulation of Contact Problems. - Berlin/Heidelberg : Springer Berlin/Heidelberg. - 9783540317609 - 9783540317616 - 3540317600 ; , s. 121-128
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- For static or incremental contact problems with Coulomb friction there are satisfactory and well known existence results for the coercive case, i.e., when the elastic body is anchored so that rigid body motions are not possible, see [3, 1, 6, 7, 2]. The articles by Jaruusek and Cocu, [7, 2] indeed contain results for the noncoercive case, i.e., when rigid body motions are possible. However, the compatibility conditions which are used to ensure the existence of a solution, are the same that guarantee that the corresponding contact problem without friction has a solution. The condition is essentially that the applied force field should push the elastic body towards the obstacle. One of few previous articles containing friction-dependent compatibility conditions is.
|
|
| 10. |
|
|
| 11. |
- Andersson, Lars-Erik, 1942-, et al.
(författare)
-
On the existence and uniqueness of steady state solutions in thermoelastic contact with frictional heating
- 2005
-
Ingår i: Proceedings of the Royal Society of Edinburgh. Section A Mathematics. - : The Royal Society. - 0308-2105 .- 1473-7124. ; 461:2057, s. 1261-1282
-
Tidskriftsartikel (refereegranskat)abstract
- It is well known that contact and friction in thermoelasticity result in mathematical problems which may lack solutions or have multiple solutions. Previously, issues related to thermal contact and issues related to frictional heating have been discussed separately. In this work, the two effects are coupled. Theorems of existence and uniqueness of solutions in two or three space dimensions are obtained - essentially extending, to frictional heating, results due to Duvaut, which were built on Barber's heat exchange conditions. Two qualitatively different existence results are given. The first one requires that the contact thermal resistance goes to zero at least as fast as the inverse of the contact pressure. The second existence theorem requires no such growth condition, but requires instead that the frictional heating, i.e. the sliding velocity times the friction coefficient, is small enough. Finally, it is shown that a solution is unique if the inverse of the contact thermal resistance is Lipschitz continuous and the Lipschitz constant, as well as the frictional heating, is small enough.
|
|
| 12. |
|
|
| 13. |
|
|
| 14. |
- Andersson, Lars-Erik, 1942-2014
(författare)
-
Quasistatic frictional contact problems with finitely many degrees of freedom.
- 1999
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In the present paper results on existence and uniqueness of solutions to discrete frictional quasi-static unilateral contact problems are given under a condition that the coefficients of friction are smaller than a certain upper bound. This upper bound is defined in terms of an influence matrix for the contact nodes. The results of existence and uniqueness may be ordered into two classes depending on whether regularity conditions for the applied forces are imposed or not. For general loading which has a time derivative almost everywhere it is shown that a solution exists which satisfies governing equations for almost all times. Uniqueness of the solution has been shown only when the problem is restricted to two degrees of freedom. For a loading which is right piecewise analytic, additional results can be obtained. For instance, if each contact node has only two degrees of freedom a unique solution which satisfies governing equeations for all times exists. For the constructed solutions a priori estimates of the displacement field and its time derivate in terms of the applied forces are also given.
|
|
| 15. |
|
|
| 16. |
- Andersson, Lars-Erik, 1942-, et al.
(författare)
-
Thermoelastic Contact with Frictional Heating
- 2006
-
Ingår i: Nonsmooth Mechanics and Analysis,2003. - New York : Springer Science+business Media, inc.. ; , s. 61-
-
Konferensbidrag (refereegranskat)
|
|
| 17. |
|
|
| 18. |
- Rietz, Andreas, et al.
(författare)
-
Noncoercive incremental friction problems for discrete systems
- 2006
-
Ingår i: Zeitschrift für angewandte Mathematik und Mechanik. - : Wiley. - 0044-2267 .- 1521-4001. ; 86:12, s. 932-950
-
Tidskriftsartikel (refereegranskat)abstract
- We present a sufficient condition for the existence of solutions to noncoercive incremental friction problems for discrete systems in contact with obstacles. By discrete system we mean that the displacement of the object can be discribed by a finite number of displacement variables, and by noncoercive we mean that the stiffness matrix of the object is semidefinite. We have a noncoercive friction problem when the object is not fixed to a support. This means that the friction forces need to balance the applied forces if the object is to remain stationary. This is manifested in our condition for existence of solutions. This condition is a compatibility condition on the applied force field, and if it is violated there exists a nontrivial solution to a corresponding dynamical problem. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.
|
|
