Other input settings#

There are three groups of these settings.

Included files#

This part contains file names for base lines, materials (local) and layups as shown in Input syntax for the included files.. The <material> sub-element is optional. If this is included, PreVABS will read extra materials from this local file, besides the global material database (MaterialDB.xml). If there are materials and laminae with the same names, data in the local material file will overwrite those in the global database.

  • path in the <include> element is the relative path to the main input file;

  • File extensions .xml can be omitted.

Listing 4 Input syntax for the included files.#
1<include>
2  <baseline> path/baseline_file_name </baseline>
3  <material> path/material_file_name </material>
4  <layup> path/layup_file_name </layup>
5</include>

Specification

  • <baseline> - Name of the included base line file.

  • <material> - Name of the included local material file.

  • <layup> - Name of the included layup file. Multiple <layup> elements can be listed to merge several layup files.

Analysis options#

The second part contains settings for the analysis in VABS. <model> can be 0 for classical beam model, or 1 for refined (Timoshenko) model.

Listing 5 A template for the analysis options in a main input file.#
1<analysis>
2  <model> 1 </model>
3</analysis>

Specification

  • <model_dim> - Dimension of the structural model. 1 (default) for beam.

  • <model> - Beam model. Choose one from 0 (classical) and 1 (refined / Timoshenko).

  • <damping>, <thermal>, <trapeze>, <vlasov> - Optional integer flags passed through to the solver. Default 0.

  • <initial_twist>, <initial_curvature_2>, <initial_curvature_3> - Optional initial twist / curvature components. Setting any of them to a non-zero value enables the curvature flag.

  • <oblique_y1>, <oblique_y2> - Optional direction-cosine components enabling the oblique flag when they differ from (1, 0).

  • <physics> - Optional physics setting forwarded to the analysis backend.

Global shape and mesh settings#

The last part contains optional global geometry and meshing settings, which are all stored in a <general> sub-element.

User can set the global transformations of the cross section. The three transformation operations have been discussed in Coordinate systems.

  • The order of transformation operation is: translating, scaling, and rotating;

  • All operations are performed on the cross section, not the frame;

  • The scaling operation will only scale the shape (base lines), and have no effect on the thicknesses of laminae;

  • The rotating angle starts from the positive half of the \(x_2\) axis, and increases positively counter-clockwise (right-hand rule).

There are two basic meshing options, the global mesh size <mesh_size> and the polynomial order <element_type>. In addition, the mesh element shape can be switched between triangles and quadrilaterals via <element_shape>, and a number of optional Gmsh transfinite/recombination controls are available.

  • If not setting, the global meshing size will be the minimum layer thickness by default;

  • Two options for the element type are linear and quadratic.

  • Two options for the element shape are triangle and quadrilateral.

Listing 6 A template for the global shape and mesh settings in a main input file.#
1<general>
2  <translate> e2  e3 </translate>
3  <scale> scaling_factor </scale>
4  <rotate> angle </rotate>
5  <mesh_size> a </mesh_size>
6  <element_type> quadratic </element_type>
7  <element_shape> 3 </element_shape>
8  <tolerance> 1e-12 </tolerance>
9</general>

Specification

  • <translate> - Horizontal and vertical translation of the cross-section. The origin will be moved to (-e2, -e3).

  • <scale> - Scaling factor of the cross-section.

  • <rotate> - Rotation angle of the cross-section.

  • <mesh_size> - Global mesh size.

  • <element_type> - Order of elements. linear (or 1) or quadratic (or 2, default).

  • <element_shape> - Shape of mesh elements. 3, tri, or triangle (default) for triangles; 4, quad, or quadrilateral for quadrilaterals.

  • <tolerance> - Tolerance used in geometric computation. Optional. Default value is 1e-12.

  • <omega> - Optional global scaling factor passed to the solver. Default 1.0.

When <element_shape> selects quadrilaterals, the following Gmsh-driven controls become available:

  • <transfinite_auto> - 1/true to enable Gmsh’s automatic transfinite meshing of structured regions.

  • <transfinite_corner_angle> - Angle threshold (radians) used by the transfinite-auto algorithm to decide which corners to fix.

  • <transfinite_recombine> - 1/true to recombine triangles into quads after transfinite meshing.

  • <recombine> - 1/true to enable Gmsh’s general recombine pass.

  • <recombine_angle> - Angle threshold (degrees) used by the recombine algorithm.

Interface tracking between layers is also configurable here:

  • <track_interface> - Integer flag to write per-interface marker output.

  • <interface_theta1_diff_threshold>, <interface_theta3_diff_threshold> - Angle thresholds (degrees) used to decide whether two adjacent layers share an interface for tracking.