PSHELL – Shell Element Property
Defines the membrane, bending, transverse shear, and membrane-bending coupling of shell elements.
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(1) |
(2) |
(3) |
(4) |
(5) |
(6) |
(7) |
(8) |
(9) |
(10) |
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PSHELL |
PID |
MID1 |
T |
MID2 |
12I/T3 |
MID3 |
TS/T |
NSM |
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Z1 |
Z2 |
MID4 |
T0 |
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(1) |
(2) |
(3) |
(4) |
(5) |
(6) |
(7) |
(8) |
(9) |
(10) |
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PSHELL |
203 |
204 |
1.90 |
205 |
1.2 |
206 |
0.8 |
6.32 |
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+.95 |
-.95 |
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0.1 |
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Field |
Contents |
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PID |
Unique shell element property identification number. (Integer > 0) |
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MID1 |
Material identification number for membrane. Please see comment 3. (Integer > 0) |
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T |
Default value for the membrane thickness (Real > 0.0). If T0 is defined for topology optimization, T is the total thickness. |
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MID2 |
Material identification number for bending. Please see comment 3. (Integer > -1 or blank) |
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12I/T3 |
Bending stiffness parameter. (Real >0.0 or blank, default = 1.0) |
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MID3 |
Material identification number for transverse shear. Please see comment 3. (Integer > 0 or blank, must be blank unless MID2 > 0) |
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TS/T |
Transverse shear thickness divided by the membrane thickness. (Real >0.0 or blank, default = .833333) |
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NSM |
Nonstructural mass per unit area. (Real) |
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Z1,Z2 |
Fiber distances for stress computation. The positive direction is determined by the right hand rule and the order in which the grid points are listed on the connection entry. (Real or blank, see comment 7 for defaults) |
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MID4 |
Material identification number for membrane-bending coupling. (Integer > 0 or blank, must be blank unless MID1>0 and MID2>0, may not be equal to MID1 or MID2). See comments 10 and 11. |
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T0 |
The base thickness of the elements in topology optimization. Only for MAT1, T0 can be >0.0. If T0 is blank, then the elements are not included in the topology design volume or space. (Real > 0.0 or blank for MAT1, Real = 0.0 or blank for MAT2, MAT8) |
All shell element property entries must have unique identification numbers.
The structural mass is computed from the density using the membrane thickness and membrane material properties.
MID1 cannot be left blank. The
results of leaving an MID2 or MID3 field blank are:
MID2 No bending, coupling, or transverse shear stiffness
MID3 MID2 is used
Leave MID2 and MID3 blank for solving 2-D elasticity problems.
MID2 = -1 Plane strain. See comment 13.
The continuation is not required.
This entry is used in connection with the CTRIA3 and CQUAD4 entries.
PSHELL entries may reference MAT1, MAT2 and MAT8 material property entries.
The default for Z1 is -T/2, and for Z2 it is +T/2. T is the local plate thickness, defined by T on this entry. For free-sizing optimization, Z1 and Z2 definitions are ignored and the defaults of –T/2 and +T/2 are used for each element.
If MID3 references a MAT2 material, then G33 on the MAT2 data must be blank.
If MID3 references a MAT8 material, then G1Z and G2Z must not be blank.
MID4 provides a way to represent shells with offset (shell element centerline being offset from the plane of the grid points) or shells with material properties that are not symmetric with respect to the middle surface of the shell. However, whenever possible, the preferred method of representing such shells is through the use of element offset ZOFFS or the composite property PCOMP. This is because MID4 does not provide sufficient information about the shell structure to correctly calculate all respective results, specifically:
- The shell stresses calculated in the presence of MID4 are generally incorrect, as they do not reflect the actual shell offset or the non-uniform material structure.
- The effects of MID4 are not considered in the calculation of differential stiffness. Hence, it is recommended that MID4 be left blank in buckling analysis.
If MID4 points to a MAT2 card with a material ID greater than 400,000,000, then the thermal membrane-bending coefficients A1, A2, and A12 have a modified interpretation, and represent [G]*[alpha] rather then [alpha]. Here, [G] is a matrix composed of G11,G22…G33. This is to maintain consistency with respective terms generated internally by the PCOMP card.
Thermal expansion coefficients provided for materials referenced as MID2 or MID3 are ignored in shell analysis - only the thermal expansion terms for materials referenced as MID1 (membrane) and MID4 (coupling) are considered. Furthermore, the reference temperature (TREF) for the shell property is taken from the material referenced as MID1 - TREF's provided for other MID's are ignored.
In plane strain computations, in-plane loads are interpreted as line loads with a value equal to the load, divided by the thickness. Thus, if a thickness of "1.0" is used, the value of the line-load equals the load value. Pressure can be approximated with multiple line loads where the pressure value equals the line-load, divided by the length between the loads.
Go To
Guidelines for Bulk Data Entries
Alphabetical List of Bulk Data Entries