Modelling of Three-Dimensional Contacts by Coupled Multibody- and Boundary-Element-Systems

Beschreibung

Ongoing research work on the development of contact models in multibody systems shows large interest for fast, reliable and robust algorithms. Most algorithms are developed for special applications while they focus on fast calculation of global reactions. A possibility to model local mechanical contacts in multibody systems is the coupling of multibody systems and finite element or boundary element systems. The advantage of this method is that all possibilities of the finite element or boundary element systems, respectively, are integrated into the multibody simulation. The contact stresses can be obtained, but the computation time is very high. Compared to finite element methods the boundary element method is much younger for practical applications. Boundary element models need about 10 % of the degrees of freedom compared to finite element models due to the fact that surface discretisation is needed only. Due to the mixed formulation of boundary elements, in which the surface displacements and tractions are interpolated, a boundary element mesh typically provides results with a higher accuracy than an assimilable finite element mesh. To the authors knowledge this thesis presents for the first time the coupling of multibody and boundary element systems for elastic contact calculations. Compared to elastic multibody systems based on component mode synthesis this approach provides results with higher accuracy. This results from the use of local interpolation functions for displacement and traction fields instead of global RITZ approaches.
Ongoing research work on the development of contact models in multibody systems shows large interest for fast, reliable and robust algorithms. Most algorithms are developed for special applications while they focus on fast calculation of global reactions. A possibility to model local mechanical contacts in multibody systems is the coupling of multibody systems and finite element or boundary element systems. The advantage of this method is that all possibilities of the finite element or boundary element systems, respectively, are integrated into the multibody simulation. The contact stresses can be obtained, but the computation time is very high. Compared to finite element methods the boundary element method is much younger for practical applications. Boundary element models need about 10 % of the degrees of freedom compared to finite element models due to the fact that surface discretisation is needed only. Due to the mixed formulation of boundary elements, in which the surface displacements and tractions are interpolated, a boundary element mesh typically provides results with a higher accuracy than an assimilable finite element mesh. To the authors knowledge this thesis presents for the first time the coupling of multibody and boundary element systems for elastic contact calculations. Compared to elastic multibody systems based on component mode synthesis this approach provides results with higher accuracy. This results from the use of local interpolation functions for displacement and traction fields instead of global RITZ approaches.

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János Zierath

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