Users:General FEM Analysis/Elements Reference/Shell NURBS KL
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Contents |
General Description
This element is based on Kiendl et al. 2009 [1] and Phd Thesis of J.Kiendl.
Example of a Complete Input Block
EL-PROP 1 : SHELL_NURBS_KL MAT= EL-MAT 1 !material property THICKNESS = 1.0 COUPLING = EL-PROP 6 !BRep coupling element to handle C^0 continuity inside the patch ! STABILIZATION = EL-PROP 7 !Stabilization element for improving condition number (requires some tests, no optimal solution) NEJA = NURBS !DIP or FULL !Method for handling the integration for trimmed elements(use NURBS) INT_TYPE_SHELL_NURBS_KL = USER !or FULL or OPTIMAL !FULL means p+1 and q+1;OPTIML uses in the interior of the patch less quadrature points (some tests required for higher polynomial degrees >3 ! GAUSS_U = 4 !# of quadratur points in u-dir in case of INT_TYPE = USER ! GAUSS_V = 4 !# of quadratur points in u-dir in case of INT_TYPE = USER
Element Type
- The element formulation is well tested for static and dynamic linear and nonlinear analysis.
- Stresses for nonlinear case need to be corrected.
- Can be used for thin shell structures
Degrees of Freedom
The element uses three translatoric degrees of freedom (Disp_X, Disp_Y, Disp_Z) at each control point.
Parameter Description
| Compulsory Parameters | ||
| Parameter | Values, Default(*) | Description |
|---|---|---|
| MAT | EL-MAT int | Linking to a material input block |
| INT_TYPE_SHELL_NURBS_KL | FULL, USER, OPTIMAL | Control of integration type.
|
| THICKNESS | float | Thickness of the shell |
| NEJA | NURBS, DIP, FULL | Integration technique for trimmed elements
|
| Optional Parameters | ||
| Parameter | Values, Default(*) | Description |
| GAUSS_U | GAUSS_U = int | Number of quadrature points in u-direction. Requires INT_TYPE_SHELL_NURBS_KL= USER |
| GAUSS_V | GAUSS_V = int | Number of quadrature points in v-direction. Requires INT_TYPE_SHELL_NURBS_KL= USER |
| COUPLING | EL-PROP= int | BRep coupling element to handle C^0 continuity inside the patch |
| STABILIZATION | EL-PROP= int | Stabilization element for improving condition number (requires some tests, no optimal solution) |
| PRESTRESS_CRV | PRESTRESS_CRV = AUTO | All curvature terms (b_ref) are set to zero in stiff_mat_el_nln(). This is equal to having a flat patch as reference patch |
| PRESTRESS_CL_A1 | PRESTRESS_CL_A1 = AUTO | covariant metric for reference configuration (gab_ref[0] and gab_ref[2]) is set to the one of the center line (v_mid=const) in stiff_mat_el_nln(). This is only valid for special case of pre-bent lamellas. |
| PRESTRESS_CL_A2 | PRESTRESS_CL_A2 = AUTO | covariant metric for reference configuration (gab_ref[1] and gab_ref[2]) is set to the one of the center line (u_mid=const) in stiff_mat_el_nln(). This is only valid for special case of pre-bent lamellas. |
Element Loading
The KL shell element is able to handle the following loads:
- dead load
- snow load
- pressure load
Benchmarks
The main benchmark file in the Carat++-repository is
- '../examples/benchmark_examples/isogeometric/KL_shell_trim_plate_hole/cbm_plate_with_hole.txt'.
It is further used in:
- '../examples/benchmark_examples/isogeometric/isogeometric_trim_non_linear/cbm_PlateHoleLineSupHighAcc.txt.txt'
References
- ↑ J. Kiendl, K.-U. Bletzinger, J. Linhard, and R.Wüchner. “Isogeometric shell analysis with Kirchhoff–Love elements.” In: ComputerMethods in AppliedMechanics and Engineering 198.49-52 (2009), pp. 3902–3914. DOI: 10.1016/j.cma.2009.08.013
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