Struts are specialized dampers designed to take bending and damping loads in the suspension. The same two damping definition options are available for a strut that are available for a shock. Struts are modeled with data stored in strut property files. Strut property files are stored in the dampers.tbl subdirectory of a vehicle database. The strut poperty files include three options for modeling the bending stiffness:
In the simple bending model, a bushing is attached to the upper strut piece, and is connected to the lower strut by a VFORCE statement. The VFORCE allows the reaction force on the lower strut to move with the upper strut. A second bushing moves with the lower strut, and is also modeled using a VFORCE statemtent.
As the wheel moves into jounce, the two bushings get further apart, making the strut conically stiff to bending.
When the wheel moves into rebound, the two bushings coming together decreases the conical stiffness, therefore increasing the strut bending.
The complex strut model in ADAMS/Chassis includes structural compliance. The model contains 12 parts (six each left and right). The six parts are:
To provide the radial compliance of each part, the beam stiffness properties are programmed into a FORTRAN subroutine linked in to the MSC.ADAMS model. The radial compliance of the outer tube, inner tube, and piston are linked from the MSC.ADAMS data set to the FORTRAN code through several GFORCE statements. The axial stiffness of the strut is provided by an MSC.ADAMS BEAM statement that connects the inner tube base with the rod guide. The rod guide lash and piston lash are modeled as piecewise linear bushings, and the base cup is modeled as a linear bushing.
