Users:General FEM Analysis/Elements Reference/Membrane NURBS

From Carat++ Public Wiki
< Users:General FEM Analysis | Elements Reference(Difference between revisions)
Jump to: navigation, search
(General Description)
(Parameter Description)
 
(4 intermediate revisions by one user not shown)
Line 32: Line 32:
 
|-
 
|-
 
!THICKNESS  
 
!THICKNESS  
|
+
|''real''
 
|Thickness of the membrane
 
|Thickness of the membrane
 +
|-
 +
!INT_TYPE_MEMBRANE_NURBS
 +
|FULL or USER
 +
|Type of numerical integration. With FULL the integration rule is automatically chosen, with USER it can manually be defined. For USER also the parameters GAUSS_U and GAUSS_V have to be defined.
 +
|-
 +
!GAUSS_U, GAUSS_V
 +
|''int''
 +
|Number of integration points in u and v-direction, respectively. In case of INT_TYPE_MEMBRANE_NURBS = FULL this specification is not required.
 
|-
 
|-
 
!A_X, A_Y, A_Z  
 
!A_X, A_Y, A_Z  
 
B_X, B_Y, B_Z  
 
B_X, B_Y, B_Z  
 
|
 
|
|Definition of the principal directions of the surface to define the prestress directions. (see description below)
+
|Definition of the principal directions of the surface to define the prestress directions, only applied with anisotropic prestress conditions. (see description of Membrane1-element)
 
|-
 
|-
 
!SIG11
 
!SIG11
 
SIG22
 
SIG22
 
SIG12
 
SIG12
|
+
|''reals''
|Prestress state of the membrane. (see description below)
+
|Prestress state of the membrane. (see description of Membrane1-element)
|-
+
|colspan="3" style="background:#efefef;"| Optional Parameters
+
|-
+
!Parameter
+
!Values, Default(*)
+
!Description
+
|-
+
!LAGRANGE
+
|''TOTAL, UPDATED''
+
|Definition of lagrange type. UPDATED for form finding and TOTAL for statics or dynamics. (e.g. LAGRANGE=UPDATED)
+
 
|-
 
|-
 
|}
 
|}
 
  
 
=== Example of a Complete Input Block ===
 
=== Example of a Complete Input Block ===

Latest revision as of 09:01, 13 January 2017

Contents

General Description

Element Type

  • This membrane element is an isotropic plane stress element accounting for prestress
  • The membrane element neglects bending stiffness
  • The ratio of the thickness and the lengths in the other two directions is much smaller than one ( t/Lx << 1 and t/Ly << 1), the membrane is reduced to its mid-surface
  • The thickness is constant over the element

An extensive description of the element can be found in [1]


Input Parameters

Parameter Description

Compulsory Parameters
Parameter Values, Default(*) Description
MAT EL-MAT int Number for the used Material

e.g. MAT=EL-MAT 1

THICKNESS real Thickness of the membrane
INT_TYPE_MEMBRANE_NURBS FULL or USER Type of numerical integration. With FULL the integration rule is automatically chosen, with USER it can manually be defined. For USER also the parameters GAUSS_U and GAUSS_V have to be defined.
GAUSS_U, GAUSS_V int Number of integration points in u and v-direction, respectively. In case of INT_TYPE_MEMBRANE_NURBS = FULL this specification is not required.
A_X, A_Y, A_Z

B_X, B_Y, B_Z

Definition of the principal directions of the surface to define the prestress directions, only applied with anisotropic prestress conditions. (see description of Membrane1-element)
SIG11

SIG22 SIG12

reals Prestress state of the membrane. (see description of Membrane1-element)

Example of a Complete Input Block

EL-PROP 1 : MEMBRANE_NURBS
  MAT= EL-MAT 1
  THICKNESS= 1.0
  INT_TYPE_MEMBRANE_NURBS = FULL !or USER
  PROJECTED_PRESTRESS=1 SIG11=400.0     SIG22=400.0      SIG12=0.0
  A_X=1.0     A_Y=0.0    A_Z=0.0   !AREA FOR THE DEFINITION OF THE PRESTRESS
  B_X=0.0     B_Y=1.0    B_Z=0.0   !VECTOR A AND VECTOR B DEFINE THE AREA

The possibility for oriented anisotropic prestress fields is foreseen, yet no distortion control as for the classical FEM Membrane1-element is implemented.

Tests and Benchmarks

The element Membrane_NURBS has successfully been applied in 3D in various geometrically non-linear static applications, as well as in form-finding.

Benchmark examples

  • form-finding of a four-point sail with with B-Rep edge cables and elastic columns as supports: ..\examples\benchmark_examples\isogeometric\iga_formfinding_4point_with_trusses\cbm_4PointSailwTrusses.txt
  • static geometrically non-linear analysis of a prestressed single-patch membrane with fixed boundaries: ..\examples\benchmark_examples\isogeometric\iga_membrane_nln_1\cbm_iga_membrane_nln_1.txt

References

  1. B. Philipp, M. Breitenberger, I. D’Auria, R.Wüchner, and K.-U. Bletzinger. "Integrated design and analysis of structural membranes using the Isogeometric B-Rep Analysis." In: Computer Methods in AppliedMechanics and Engineering 303 (May 2016), pp. 312–340. DOI: 10.1016/j.cma.2016.02.003.




Whos here now:   Members 0   Guests 0   Bots & Crawlers 1
 
Personal tools
Content for Developers