Linear Static Analysis

1. Bolt Stress Analysis

The linear deformations and the stresses of a bolt under external mechanical loading are computed. The example case FE model is a 3-dimensional (solid) model consisting of quadratic isoparametric elements, i.e. HE20 hexahedral, TE10 tetrahedral, and PY15 prismatic elements. The model originates from a study performed at the NLR.

The model had been generated with the Patran® mesher and converted to B2000 MDL input format. The model exhibits about 150000 degrees of freedom and a global factored matrix of about 400'000'000 non-zero elements. The figure below displays the external surface mesh:

Linear stress analysis of a bolt: Mesh

Figure 1. Linear stress analysis of a bolt: Mesh


The analysis with B2000++ is controlled with the MDL commands adir and case :

adir
  case 1
end

case 1
  analysis  linear
  nbc       1
  ebc       0
  gradients 1
end

The case option of adir specifies which case B2000++ should process (here: process case 1 and the case 1 description in the case command specifies the analysis type and other options related to that particular type of analysis:

The analysis option of case indicates the type of analysis to be performed. linear will launch the B2000++ linear analysis solver.
The nbc option activates the natural boundary condition set 1 (here: 'forces') to be applied to the current case. In this context the set pertains to forces applied.
The ebc option specifies the essential boundary condition set 0 to be applied to the current case. In this context the set pertains to 'zero displacement constraints'.
The gradients 1 option requires the gradients (strains, stresses) to be computed and stored on the database.

Solid model viewing capabilities of baspl++ are demonstrated in the figures below. The plots can be obtained either with the GUI of baspl++ or with the scripts found in the directory: deformed.py will produce the deformation plot and stress.py the rendering of the von Mises comparison stress on a cut through the semi-transparent solid.

Linear stress analysis of a bolt: Deformed structure.

Figure 2. Linear stress analysis of a bolt: Deformed structure.


Linear stress analysis of a bolt: Von Mises stresses on cut.

Figure 3. Linear stress analysis of a bolt: Von Mises stresses on cut.