FlexBody Library
The FlexBody library enables you to build complete mechanical models combining flexible structures and rigid bodies. Using features of the Finite Element analysis tools Nastran and Genesis, large, complex Finite Element models can be reduced to simpler models consisting of a small number of boundary nodes, or attachment points, and frequency modes. The reduced models still capture the same natural frequencies as the original Finite Element model within the range specified by the user.
The reduced models generated in Nastran or Genesis are then read in to Dymola using the FlexBody library. This then defines a flexible component which can be used as part of a Modelica system model. This approach enables the dynamics of the structure to be coupled to the behaviour of the complete system.
Typical examples include the use of FlexBody components to model chassis and suspension parts and to model the structure of large machines such as excavators and cranes.
Modelling approach
Nastran, Genesis and Abaqus include methods for model reduction known as Component Mode Synthesis or Craig-Bampton reduction. These transform the detailed Finite Element models in to more efficient representations for use in dynamics. This transformation reduces the models from 100,000’s degrees of freedom to a much smaller number of degrees of freedom at defined boundary nodes, or attachment points, and a number of frequency modes of the structure.
The reduced models are defined by the Finite Element tools to represent small displacements of the boundary nodes. To capture the true dynamics of the body the deflections of the structure are super-imposed on the motion of a floating rigid reference frame that captures the large displacements and rigid body modes of the structure.
The FlexBody library is compatible with the Modelica MultiBody library and all other libraries based on this including the Vehicle Dynamics library.
To find out more you can download the brochure.
