Bushing Property Files

This topic includes information about:

The Model Identification Tool is a utility in HyperGraph that you use to fit experimental data to various bushing models. The MIT generates a General Bushing System file, .gbs file, which defines the bushing properties. To learn more, see Model Identification Tool.

The table below describes the stiffness and damping formulations that are available in a .gbs file. You employ different methods for force and torque directions, but must specify for each direction only one stiffness and one damping method. An ACTIVITY TABLE in the .gbs file tells MotionView which bushing models are active.

Component	Method	Description
Stiffness	Constant Stiffness	F=-K*x; used when the bushing’s stiffness behavior is linear. The value x is the deformation in the direction of interest.
	Spline Stiffness	F=-g(x); where g(x) is a cubic spline interpolation of static Force vs. Displacement data in the .gbs file. Linear extrapolation is used when the data is outside the range of specified data.
	Cubic Stiffness	F=-h(x); where h(x) is defined by a pair of cubic polynomials whose coefficients are derived from the measured Force vs. Displacement data in the .gbs file.
Damping	Constant Damping	F=-c*v; used when the bushing’s damping behavior is linear. The value v is the deformation velocity in the direction of interest.
	Rubber Damping	An amplitude and frequency-dependent bushing model, whose coefficients are fit to measured data using a tool such as the Altair Model Identification Tool.
	Hydromount Damping	An amplitude and frequency dependent model for hydrodynamic mounts, whose coefficients are fit to measured data using a tool such as the Altair MIT.

The remainder of topics on Bushings assumes that a .gbs file is already available. For more information on how to create a .gbs file from experimental data, see: Model Identification Tool.

You can add or modify bushings in a MotionView model directly from the MotionView GUI. To do so, you need to specify a bushing property file and installation details such as connectivity, mount limits and preload. For more information, see Altair Bushing Model.