Transient Analysis

Both CABLE and BEAM NLFE components are supported for transient analyses as well. At this time, only the DAE integrator DSTIFF is supported for transient solutions. As with static analysis, you may choose any of the available material models while defining the BEAM or CABLE components for these analyses.

As with the static analysis, there are a few recommendations while running simulations with NLFE components that will ensure a successful simulation.

Specifying Damping

The NLFE components at this time do not support physical damping for the structure. However, MotionSolve does provide a numerical damping parameter that can be used to mimic physical damping in some cases. This damping is specified by multiplying a damping factor (provided by the user) with the stiffness matrix. As with any damping factor, it is recommended to start with a factor of 0 and ramp it up till the desired behavior is achieved.

True physical damping will be implemented for the NLFE structural components in future releases.

Shown in Figure 1 below is a comparison of the end deflection of a cantilever beam under end loading for different damping factor values.

Figure 1. The Displacement for Different Damping Factors

Maximum Order Used for the Simulation

Models containing NLFE components typically are very numerically stiff. This may cause numerical convergence issues if trying to solve the model with a large integration order like 5, for example. It is recommended to use a maximum order of 1 or 2 for solving models that contain NLFE components. The maximum order is specified by the attribute max_order in the Model/Command statement <Param_Transient>.