Flexible Body Degrees of Freedom (DOF)
The number of DOF (Degrees of Freedom) in a flexible body built with ViewFlex cannot be entered directly. It is a function of different input values. According to assumed modal flexibility theory, the total DOF number is a function of the natural modes and of the number of DOF constrained by the attachment points.
The DOF number for a single flexible body can be evaluated based on the number of Eigen values resulting from the mode shape orthonormalization, which is equal to the sum of the natural modes number extracted plus 6 residual vectors based on the inertia relief due to rigid body motion, and the number of constrained DOF of the attachment points. Therefore, the release of one or more DOF in attachment point's definition causes an equal decrease in the total number of flexible body DOF.
Example
If 10 normal nodes are requested in a ViewFlex model with 25 attachment points, a total of 166 modes are going to be calculated in Adams View. Here are the calculation details:
Constraint modes: 6 DOF * 25 attachment points = 150 modes
10 normal modes + 6 rigid body modes
+ 150 constraints Orthonormalization + 154 modes
166 modes 166 modes
The release of an attachment point DOF excludes it from either the static analysis, as applied force, or from the modal analysis, as restraint. The flexible body cannot evaluate the effects of an external force or reaction on the released DOF.