u2.01.02 Instructions for the use of boundary conditions treated by elimination

Summary

The treatment of boundary conditions of the Dirichlet type by elimination (AFFE_CHAR_CINE) does not offer the same generality as by dualization (AFFE_CHAR_MECA for example).

This treatment is to be used when one seeks to improve the execution times of a calculation or if one wishes to work with positive definite matrices.

Note that the boundary conditions available in AFFE_CHAR_ ( = MECA/THER/ACOU) cannot all be eliminated and treated by AFFE_CHAR_CINE.

This document shows how to use « kinematic loads » in Aster command sets.

There are 3 scenarios (from the simplest to the most complicated):

• We use a « global » calculation command (THER_LINEAIRE, STAT_NON_LINE,…). In this case, kinematic loads are used like other loads.

• We want to do a natural mode calculation. You must then add an argument to the ASSE_MATRICE command.

• We want to do a « step-by-step » calculation and solve linear systems with commands FACTORISER and RESOUDRE. In this case, you must use the CALC_CHAR_CINE command.

• 1. Principle of elimination
• 2. Treatment in Aster
  • 2.1. Kinematic loads
  • 2.2. Kinematic vectors
  • 2.3. Calculation of K”
  • 2.4. Calculation of f”
• 3. Sample command files
  • 3.1. Mechanical calculation with a global control (STAT_NON_LINE):
  • 3.2. Kinematic loads for a natural mode calculation:
  • 3.3. « Step by step » calculation using commands FACTORISER and RESOUDRE: