Inserting a New Explicit Dynamics Step

An explicit, dynamic analysis is computationally efficient for the analysis of large models with relatively short dynamic response times and for the analysis of extremely discontinuous events or processes. This type of analysis allows for the definition of very general contact conditions and uses a consistent, large-deformation theory. See Choosing Between General Static and Explicit Dynamics Steps, and Explicit dynamic analysis in the Abaqus Analysis Guide for more information.

The Explicit Dynamics step is available only in an Explicit Dynamics case, which can contain only Explicit Dynamics steps. See Step Sequence Restrictions for more information. Abaqus for CATIA V5 creates an Explicit Dynamics step by default for a new Explicit Dynamics case.

This task shows you how to insert a new Explicit Dynamics step in an Explicit Dynamics case.

  1. Select Start>Analysis & Simulation>Nonlinear Structural Analysis from the menu bar to enter the Nonlinear Structural Analysis workbench.

  2. From the New Analysis Case dialog box, select Explicit Dynamics Case.

    Abaqus for CATIA V5 creates an Explicit Dynamics step by default for a new Explicit Dynamics case.

  3. To create an additional Explicit Dynamics step, do either of the following:

    • To append a new Explicit Dynamics step to the end of the Simulation History, click the Explicit Dynamics Step icon .

      Tip:  Alternatively, you can select Insert>Explicit Dynamics Step from the menu bar.

    • To insert a new Explicit Dynamics step between two existing steps in the Simulation History, right-click the step object in the specification tree after which you want to create the new step, then select Insert Explicit Dynamics Step Below from the menu that appears.

    The Explicit Dynamics Step dialog box appears, and a new Explicit Dynamics Step objects set appears in the specification tree under the Simulation History objects set for the current Explicit Dynamics case. Abaqus for CATIA V5 also creates a History Output Request object for the new step using the default history output variables.

  4. You can change the step identifier by editing the Step name field. This name will be used in the specification tree.

  5. Enter a description for the step in the Step description field.

  6. If necessary, do the following to modify the Basic Step Data:

    1. Edit the Step time field to specify a value for the total time period of the step.

    2. Specify whether Abaqus should account for nonlinear geometric effects in the step by selecting Off or On for Nonlinear geometry. (The default value is On.) See Accounting for Nonlinear Geometric Effects for more information.

  7. If necessary, do the following to modify the Incrementation Controls:

    1. Choose an Incrementation type option:

      • Choose Automatic to allow Abaqus/Explicit to determine the time incrementation automatically. See Automatic time incrementation in Explicit dynamic analysis in the Abaqus Analysis Guide for more information.

      • Choose Fixed to use a fixed time incrementation scheme. The fixed time increment size is determined either by the initial element stability estimate for the step or by a user-specified time increment. See Fixed time incrementation in Explicit dynamic analysis in the Abaqus Analysis Guide for more information.

    2. If you selected Automatic time incrementation, perform the following steps:


      1. Choose a Stable increment estimator option:

        • Choose Global to allow the global estimator to determine the stability limit as the step proceeds. The adaptive, global estimation algorithm determines the maximum frequency of the entire model using the current dilatational wave speed. This algorithm continuously updates the estimate for the maximum frequency. The global estimator will usually allow time increments that exceed the element-by-element values.

        • Choose Element-by-element to allow Abaqus/Explicit to determine an element-by-element estimate using the current dilatational wave speed in each element.

          The element-by-element estimate is conservative; it will give a smaller stable time increment than the true stability limit that is based upon the maximum frequency of the entire model. In general, constraints such as boundary conditions and kinematic contact have the effect of compressing the eigenvalue spectrum, and the element-by-element estimates do not take this into account.

      2. Choose a Max. time increment option:

        • Choose Unlimited if you do not want to impose an upper limit to time incrementation.

        • Choose Value to enter a value for the maximum time increment allowed. Enter the value in the field provided.

      See Automatic time incrementation in Explicit dynamic analysis in the Abaqus Analysis Guide for more information.

    3. If you selected Fixed time incrementation, choose an option for determining the increment size:

      • Choose User-defined time increment to specify a time increment size directly. Enter that time increment size in the field provided.

      • Choose Element-by-element time increment estimator to use time increments the size of the initial element-by-element stability limit throughout the step. The dilatational wave speed in each element at the beginning of the step is used to compute the fixed time increment size.

    4. If desired, enter a Time scaling factor to adjust the stable time increment computed by Abaqus/Explicit. (This option is unavailable if you have specified a User-defined time increment for the Fixed time incrementation scheme.) See Scaling the time increment in Explicit dynamic analysis in the Abaqus Analysis Guide for more information.

  8. Click OK when you have finished defining the step.

    The Explicit Dynamics Step objects set contains a default Field Output Request object in a Field Output Requests objects set. See Requesting Results for more information.