DLR FlexibleBodies LIBRARY

The commercial DLR FlexibleBodies Library enables the object-oriented and mathematically efficient modelling of flexible bodies as components of multibody and of arbitrary physical systems. It provides Modelica model classes to model beams, annular plates, anti-roll bars  and general flexible bodies exported from finite element programs. The motion of a flexible structure is defined by superposition of a in general large, non-linear motion of a reference frame with small elastic deformations. The library is commercially available at LTX and Dassault Systems


  • Considers bending deformation in two planes, St-Venant torsion and lengthening displacements.
  • Analytical eigenmodes are used to discretize the elastic deformation field.
  • The beam is assumed to be straight with a constant cross section along its longitudinal axis.
  • Only homogeneous and isotropic elastic material properties are considered.

  • Geometric stiffening (or softening) effects such as the influence of large longitudinal forces on the bending behavior are taken into account
  • Describes the mechanical behaviour of an annular plate, presented as a homogeneous Kirchhoff plate with transverse deformations.
  • Eigenmodes are used to discretize the deformation field.
  • With respect to the rotations around the angular plate axis, loads may be applied to structure-fixed Lagrange nodes that follow this rotation and therefore may also be called rotate-with-plate nodes. .
  • Alternatively, space-fixed Arbitrary-Lagrangian-Eulerian (ALE) or slide-on-plate nodes are available.

  • A ModalBody instance is capable to represent bodies with an arbitrary geometrical shape that originate from finite element data.
  • The library exploits the so-called SID format or file, respectively, in order to represent the mechanical properties of the structure under consideration and uses a wavefront file for visualization and animation purposes.
  • These files have to be generated in a preprocessing step from finite element data of the body. We recommend to use interfaces from Abaqus or Simpack.

  • The AntiRollBar model allows for the modeling of automotive anti-roll bars (also called stabilizer or anti-sway bar) with an (almost) arbitrary geometrical shape in a user-friendly way.
  • Considers attachments to the vehicle body and the suspensions.
  • Tailored to be used for vehicle driving maneuvers or to be employed for NVH analysis as well.