INISTRS
Bulk Data Entry Defines initial stress values and settings for elements in nonlinear analysis.
Format
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
INISTRS | ID | ETYPE | CIDA |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
SECT | NSEC | SEC1 | SEC2 | SEC3 | etc. |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
EORS | EID/ESETID | CIDB | |||||||
VALUE | STRS1 | STRS2 | STRS3 | etc. |
When ETYPE = SHELL and the SECT line is given, each VALUE line defines initial stress for a shell section; and so, for any shell element (with EID) or shell element set (with ESETID), the number of VALUE lines must be NSEC.
Alternate Format (Initial Stress from H3D file)
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
INISTRS | ID | ASSIGN | SUBID | ||||||
EORS | EID1/ ESETID1 | EID2/ ESETID2 | EID3/ ESETID3 | EID4/ ESETID4 | EID5/ ESETID5 | EID6/ ESETID6 | EID7/ ESETID7 | ||
EID8/ ESETID | etc. | etc. |
Example 1
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
INISTRS | 7 | ||||||||
ELEM | 1001 | ||||||||
VALUE | 3.5e4 | -1.5e3 | 0.0 | 3.0e3 | 0.0 | 2.0e3 | |||
ESET | 200 | ||||||||
VALUE | 3.0e4 | -1.5e3 | 0.0 | 3.0e3 | 0.0 | 2.0e3 |
Example 2
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
INISTRS | 8 | SHELL | -1 | ||||||
SECT | 2 | ||||||||
ELEM | 101 | ||||||||
VALUE | 3.5e4 | 0.0 | 0.0 | ||||||
VALUE | -3.5e4 | 0.0 | 0.0 | ||||||
ELEM | 102 | ||||||||
VALUE | 3.0e4 | 0.0 | 0.0 | ||||||
VALUE | -3.0e4 | 0.0 | 0.0 |
Example 3 (Alternate Format – Stress from H3D file)
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
INISTRS | 7 | 19 | 3 | ||||||
ELEM | 1001 | 2002 | 3003 |
Example 4 (Alternate Format – Stress from H3D file)
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
INISTRS | 8 | 29 | 6 | ||||||
ESET | 2 | 5 | 9 | ||||||
ESET | 9 | 19 | 29 |
Definitions
Field | Contents | SI Unit Example |
---|---|---|
ID | Unique identification
number. No default (Integer > 0) |
|
ETYPE | Element type which
initial stress is applied.
|
|
CIDA | Coordinate system
identification number, or stress components flag.
Integer > 0: user-defined (prescribed) coordinate system. |
|
SECT | Keyword indicating the start of continuation line(s) for the shell sections. | |
NSEC | Number of shell
sections where initial stress is applied for shell elements.
No default (1 ≤ Integer ≤ 6) |
|
SEC(i) | Through-thickness
position for the shell sections. SEC(i) must
be either all blank or all non-blank, i.e., the number of
SEC(i) must be either
NSEC or zero; and
SEC(i) must be given in ascending order
if all non-blank. Blank implies that the sections are located uniformly through the shell thickness, starting at the bottom surface and ending at the top surface. A Real value is the multiplier to shell thickness to get the location. -0.5 means the bottom surface of the shell element and 0.5 means the top surface. The through-thickness positive direction, pointing from the bottom surface to the top surface, is determined by the right-hand rule and the order in which the grid points are listed on the connection entry. It is same as the convention for Z1/Z2 of PSHELL. <Blank, or -0.5 ≤ Real ≤ 0.5> Default = Blank |
|
EORS | Flag indicating an
element, or element SET is selected in the
following field.
|
|
EID/ESETID | Identification number
of the element or element SET to which the
stress values apply. No default (Integer > 0) |
|
CIDB | Coordinate system
identification number or stress components flag.
Integer > 0: user-defined (prescribed) coordinate system. |
|
VALUE | Keyword indicating the start of a continuation line for the stress components. | |
STRS(i) | Stress components
4 No default (Real) |
|
Alternate Format Definitions (Stress from H3D file): 5 - 7 | ||
ASSIGN | Identification number
of ASSIGN, H3DRES. When
ASSIGN is specified,
SUBID should be specified as well, and
“VALUE” continuation line is not
allowed. This field is mandatory for Alternate Format (Stress from H3D file). No default (Integer > 0) |
|
SUBID | Subcase identification
number where initial stress is applied from a H3D file. This field is mandatory for Alternate Format (Stress from H3D file). No default (Integer > 0) |
|
EORS | Flag indicating an
element, or element SET is selected in the
following field.
|
|
EID#/ESETID# | Identification number
of the element or the element SET to which
the stress values apply. No default (Integer > 0) |
Comments
- INISTRS and ISTSADD should not have the same ID.
- The INISTRS Bulk Data Entry is selected by the Subcase Information command INISTRS.
- Initial stress is supported for solid
elements (CHEXA, CPENTA,
CPYRA and CTETRA) and shell elements
(CQUAD4, CTRIA3, CQUAD8
and CTRIA6), only.Initial stress is currently not supported for:
- solid elements with hyperelastic material in LGDISP analysis
- solid elements with user-defined material in LGDISP analysis
- For initial stress of solid elements, 6 stress
components are needed for each VALUE line and they are:
- STRS1
- xx
- STRS2
- yy
- STRS3
- zz
- STRS4
- xy
- STRS5
- yz
- STRS6
- zx
For initial stress in element or material coordinate system of shell elements, 3 stress components are needed for each VALUE line and they are:- STRS1
- STRS2
- STRS3
For initial stress in the basic or a prescribed coordinate system of shell elements, 6 stress components are needed for each VALUE line and they are:- STRS1
- xx
- STRS2
- yy
- STRS3
- zz
- STRS4
- xy
- STRS5
- yz
- STRS6
- zx
Alternate Format (Stress from H3D file):
- VALUE continuation line is not allowed for the Alternate Format when Stress is sourced from a H3D file.
- For Shell elements, currently only the equivalent of NSEC=2 is supported (Z1 and Z2 layers) to apply the initial stress, as the number of layers where stress data is available can be identified from the H3D file.
- Currently only H3D files output from OptiStruct and HyperForm are supported.