A quasi-static simulation is a sequence of static simulation steps applied to a model over a given duration at specified intervals. A quasi-static simulation is employed when you have time-dependent forces or motions in the model and you want a static equilibrium configuration at every time step. The system must have at least one degree of freedom to undergo a quasi-static simulation and you must specify the initial configuration.

For the first time step, the user-specified initial configuration is used as a starting point, whereas for all other time-steps, a configuration from the previous time step is used as the starting point for equilibrium simulation at that time step. A final configuration is arrived at iteration-by-iteration, such that there are no unbalanced forces or torques on any of the bodies in the system and all of the kinematic constraints are satisfied at that time step. For every step, all velocities and accelerations are set to zero.

A multi-body subcase needs to be defined in the input deck. Only one such subcase can be used in a model. The simulation type "quasi-static" is defined on an MBSIM bulk data entry which must be referenced through a subcase statement MBSIM. The MBSIM bulk data entity also defines the integrator, end time, and time step. A sequence of several simulations of different types can be defined by referring to a MBSEQ bulk data statement instead. Loads and motions are referenced on MLOAD and MOTION subcase entries, respectively. Initial velocities do not apply here. SPC type constraints in Multi-body Dynamics analysis are allowed only for MBD-ESL optimization of a flexible body if displacements are used as constraints. Further information on loads and boundary conditions can be obtained from the sections Applied Forces and Motions and Initial Velocity.

The unit system for the simulation can be defined using a DTI, UNITS bulk data entry.

See Also:

Multi-body Dynamics Simulation