General Implicit Dynamics Analyses
General implicit dynamic analysis in Abaqus/Standard uses implicit time integration to
calculate the transient dynamic or quasi-static response of a system. The procedure can be
applied to a broad range of applications calling for varying numerical solution strategies,
such as the amount of numerical damping required to obtain convergence and the way in which
the automatic time incrementation algorithm proceeds through the solution. Typical dynamic
applications fall into three categories:
- Transient fidelity applications, such as an analysis of satellite systems, require
minimal energy dissipation. In these applications small time increments are taken to
accurately resolve the vibrational response of the structure, and numerical energy
dissipation is kept at a minimum. These stringent requirements tend to degrade convergence
behavior for simulations involving contact or nonlinearities.
- Moderate dissipation applications encompass a more general range of dynamic events in
which a moderate amount of energy is dissipated by plasticity, viscous damping, or other
effects. Typical applications include various insertion, impact, and forming analyses. The
response of these structures can be either monotonic or nonmonotonic. Accurate resolution
of high-frequency vibrations is usually not of interest in these applications. Some
numerical energy dissipation tends to reduce solution noise and improve convergence
behavior in these applications without significantly degrading solution accuracy.
- Quasi-static applications are primarily interested in determining a final static
response. These problems typically show monotonic behavior, and inertia effects are
introduced primarily to regularize unstable behavior. For example, the statically unstable
behavior may be due to temporarily unconstrained rigid body modes or “snap-through”
phenomena. Large time increments are taken when possible to obtain the final solution at
minimal computational cost. Considerable numerical dissipation may be required to obtain
convergence during certain stages of the loading history.
Specifying the Application Type
Based on the classifications listed above, you should indicate the type of application you
are studying when performing a general dynamic analysis. Abaqus/Standard assigns numerical
settings based on your classification of the application type, and this classification can
significantly affect a simulation. In some cases accurate results can be obtained with more
than one application-type setting, in which case analysis efficiency should be considered. A
general trend is that—among the three classifications—the high-dissipation quasi-static
classification tends to result in the best convergence behavior and the low-dissipation
transient fidelity classification tends to have the highest likelihood of convergence
difficulty.