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Functions
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Purpose
Element property function for shells
Syntax
il = p_shell('default');
il = p_shell('database ProId name');
il = p_shell('dbval ProId name');
il = p_shell('dbval -unit TM ProId name');
il = p_shell('SetDrill 0',il);
Description
This help starts by describing the main commands : p_shell Database and Dbval. Supported p_shell subtypes and their formats are then described.
p_shell contains a number of defaults obtained with the database and dbval commands which respectively return a structure or a element property row. You can select a particular entry of the database with using a name matching the database entries.
You can also automatically compute the properties of standard shells with
| kirchhoff e | Kirchhoff shell of thickness e |
| mindlin e | Mindlin shell of thickness e |
| laminate MatIdi Ti Thetai | Specification of a laminate property by giving the different ply MatId, thickness and angle. |
You can append a string of the form -f i to select the appropriate shell formulation. For example, you will obtain the element property row with EltId 100 associated with a .1 thick Kirchhoff shell (with formulation 5) or the corresponding Mindlin plate use
il = p_shell('database 100 MindLin .1')
il = p_shell('dbval 100 kirchhoff .1 -f5')
il = p_shell('dbval 100 laminate 110 3e-3 30 110 3e-3 -30')
il = fe_mat('convert SITM',il);
il = p_shell(il,'dbval -unit TM 2 MindLin .1')
For laminates, you specify for each ply the MatId, thickness and angle.
Element properties are described by the row of an element property matrix or a data structure with an .il field containing this row (see section 7.4). Element property functions such as p_shell support graphical editing of properties and a database of standard properties.
For a tutorial on material/element property handling see section 4.2.1. For a programmers reference on formats used to describe element properties see section 7.4.
p_shell currently only supports two subtypes
[ProID type f d 0 h k MID2 12I/T3 MID3 NSM Z1 Z2 MID4]
| type | identifier obtained with fe_mat('p_shell','SI',1) | |
| f | 0 | default, for other formulations the specific help for each element (quad4, ...) |
| d | -1 | no drilling stiffness. The element DOFs are the standard translations and rotations at all nodes (DOFs .01 to .06). The drill DOF (rotation .06 for a plate in the xy plane) has no stiffness and is thus eliminated by fe_mk if it corresponds to a global DOF direction. The default is d=1 (d is set to 1 for a declared value of zero). |
| d | arbitrary drilling stiffness with value proportional to d is added. This stiffness is often needed in shell problems but may lead to numerical conditioning problems if the stiffness value is very different from other physical stiffness values. Start with a value of 1. Use il=p_shell('SetDrill d',il) to set to d the drilling stiffness of all p_shell subtype 1 rows of the property matrix il. | |
| h | plate thickness | |
| k | k | shear correction factor (default 5/6, default used if k is zero). This correction is not used for formulations based on triangles since tria3 is a thin plate element. |
| 12I/T3 | Ratio of bending moment of inertia to nominal T3/12 (default 1). | |
| NSM | Non structural mass per unit area. | |
| MID2 | unused | |
| MID3 | unused | |
| z1,z2 | (unused) offset for fiber computations | |
| MID4 | unused |
Shell strain is defined by the membrane, curvature and transverse shear (display with p_shell('ConstShell')).
| { |
| }=[ |
| ] { |
| } (8.16) |
[ProID type Z0 NSM SB FT TREF GE LAM MatId1 T1 Theta1 SOUT1 ...]
| ProID | section property identification number |
| type | identifier obtained with fe_mat('p_shell','SI',2) |
| Z0 | distance from reference plate to bottom surface. |
| NSM | non structural mass per unit area |
| SB | allowable shear stress of the bonding material |
| FT | Failure theory |
| TREF | Reference temperature |
| GE | Hysteretic loss factor |
| LAM | Laminate type |
| MatIdi | MatId for ply i |
| Ti | Thickness of ply i |
| Thetai | Orientation of ply i |
| SOUTi | Stress output request for ply i |
Note that this subtype is based on the format used by NASTRAN for PCOMP but not currently implemented in any element. You can use the DbvalLaminate commands to generate standard entries.
| { |
| } = [ |
| ] { |
| } (8.17) |
See also
Section 4.2.1, section 7.4, fe_mat
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