Description: Various algorithmic changes have made the general direct-integration dynamic procedure more broadly applicable. For example, this procedure is now effective for many applications that involve contact, especially if an energy dissipation mechanism such as plastic yielding or viscous damping is present.

You are encouraged to provide a high-level classification of the application type so that appropriate numerical settings are applied. Settings are predefined for the following application types:

• Transient fidelity applications—such as an analysis of satellite systems—use small time increments to accurately resolve the vibrational response of the structure, and numerical energy dissipation is kept at a minimum.

• Moderate dissipation applications—including various insertion, impact, and forming analyses—use some energy dissipation (via plasticity, viscous damping, or numerical effects) to reduce solution noise and improve convergence behavior without significantly degrading solution accuracy.

• Quasi-static applications introduce inertia effects primarily to regularize unstable behavior in analyses whose main focus is a final static response. Large time increments are taken when possible to minimize computational cost, and considerable numerical dissipation may be used to obtain convergence during certain stages of the loading history.

Inertia effects are inherently stabilizing. Some models that have difficulty converging in a static analysis will behave better in a dynamic procedure. For example, unconstrained rigid-body modes (or “zero-energy” modes) are problematic in a static analysis (they cause the stiffness matrix to be singular), but inertia tends to regularize the system of equations considered by Newton iterations for a dynamic analysis. Using the general direct-integration dynamic procedure can be beneficial to solution robustness, even for cases in which the final static response is of primary interest.

In addition to specifying the application type, you can set several new controls and options in a dynamic procedure to tune the time integration scheme.

Most of the new controls for direct-integration dynamic procedures are supported in Abaqus/CAE, including the specification of the application type. Because the application type impacts many other incrementation and integration settings, options to use the analysis product or application default have been added to many of the settings in the dynamic, implicit Edit Step dialog box to simplify the possible combinations of options (see Figure 6–2, Figure 6–3, and Figure 6–4).

Step module
    Create Step: General, Dynamic, Implicit 
     Basic: Application: Transient fidelity, Moderate dissipation, Quasi-static, or Analysis product default
     Incrementation: Maximum increment size: Analysis application default
     Incrementation: Half-increment Residual: Analysis product default or Specify scale factor
     Other: Extrapolation of previous state at start of each increment: Analysis product default
     or Velocity parabolic
     Other: Alpha: Analysis product default
     Other: Initial acceleration calculations at beginning of step: Analysis product default