Linearized Flexible Multibody Dynamics Including Geometric Stiffening Effects

In multibody system simulation for vehicle dynamics applications, it is often sufficient to consider a set of system equations in which the kinematics are linearized. On the other hand, care must be taken to model the flexibility of the system bodies correctly and to be able to introduce the highly nonlinear force laws appearing in multibody vehicle models into the simulation. A formalism meeting these objectives is presented here. Special care has been taken to incorporate geometric stiffing terms that result from nominal loads on the system. This formalism is the core of the vehicle dynamic simulation code MEDYNA

Simulation flexibler Mehrkörpersysteme bei Verwendung von FEM-Daten-Interface zwischen Ansys und Mehrkörperprogrammen

Zur Simulation der Dynamik von flexiblen mechanischen Systemen werden heute Finite-Elemente-Programme und Mehrkörperprogramme eingesetzt. Finite-Elemente-Programme kommen dann zur Anwendung, wenn die lokalen Verformungen und die Spannungen der Bauteile, d. h., Fragen der Kontinuumsmechanik von Bedeutung sind. Mehrkörperprogramme dienen zur Analyse der Bewegungsabläufe von Mechanismen, deren Bauteile zumeist aus starren Körpern, Gelenken und Kraftelementen (Feder, Dämpfer usw.) bestehen. Große Bewegungen der Körper und nichtlineare Kraftgesetze sind dabei zu erfassen

Rotating Beams - Two Examples for Geometric Stiffening

The aim of this report is to analyze and compare two rotating beam examples, for which the incorporation of the so called geometric stiffening effects is essential for getting a correct solution. ANSYS; examples are simulated with the finite element code ANSYS and with the multibody system code SIMPACK

Geometric Stiffness Influence in Linearized Flexible Multibody Systems.

For simulations of flexible multibody systems (MBS) the theory of elasticity and the Rayleigh-Ritz assumption are used. In case of vehicle system dynamics the total body motion can be subdivided into a known large reference motion and a small deviation. The deviation will be described by a linearized rigid body motiuon and a linearized elastic deformation. For a correct development of the equations of motion the nominal state of the MBS must be in equilibrium. Nominal forces, torques and stresses result in geometric stiffness terms of the system equations. The paper discusses various alternatives for incorporating these terms; it is suggested to derive the geometric stiffness terms by using the equilibrium of the forces and stresses of the deflected and deformed bodies. The method is demonstrated by a flexible beam example