Extraneous Stiffness Parameters

Add extraneous stiffness parameters to the input file.

Simulation Composite Analysis uses a *User Material definition instead of a *Elastic definition to define a material in Abaqus. When a *User Material definition is used, Abaqus is unable to compute certain section parameters because the elastic constants necessary to compute these section parameters are not available. You must define these parameters in order for an analysis to run successfully.

Simulation Composite Analysis comes with a command line program called xStiff that reads an Abaqus input file and automatically computes and inserts the extraneous stiffness parameters required by reduced integration elements that utilize Simulation Composite Analysis materials. This auxiliary program significantly improves the speed and accuracy of the model building process.

Typically, xStiff is executed after the model is built and before the model is submitted for analysis. Here, the input file for this analysis is written and xStiff is used to calculate and insert the appropriate extraneous stiffness parameters.

1. To create a job, switch to the Job module.
2. Double click the Jobs icon in the model tree or select Job > Create from the main toolbar. The Create Job dialog box appears.
3. Name the job ASCA_Tutorial_3 and click Continue. The Edit Job dialog box appears.
4. Accept the default job selections and click OK.
5. From the main toolbar, select Job > Write Input > ASCA_Tutorial_3.
6. Open the Simulation Composite Analysis 2015.1 Command Shell and change the directory to the location of the ASCA_Tutorial_3.inp file.

   >>cd <directory containing input file>

7. In the Command Shell, enter:

   >>xstf -i ASCA_Tutorial_3

8. xStiff will write a modified input file and rename it ASCA_Tutorial_3_xs.inp.
9. Open the new file and note the addition of the extraneous stiffness parameters to the section definition. In particular, xStiff added the following section parameters:
   • Poisson
   • Thickness Modulus
   • Transverse Shear Stiffness
   • Hourglass Stiffness
10. Submit the job for analysis from the command line by entering:

    >>abaqus job=ASCA_Tutorial_3_xs