“Free-free” indicates that the structure is free of load and free of boundary conditions. So, the structure is free to have rigid movement in 6 degrees of freedom in three-dimensional space. Free – free modal analyses are used to find the natural frequencies of the unconstraint model.
When adding fixed supports to a model, the modes represent the vibration modes of the structure under specific boundary conditions. Thus, the fixed boundary conditions can influence the distribution of mass and stiffness and alter the resulting modes compared to the free modal analysis.
You are navigating away from the AIS Discovery experience