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ANSYS Fatigue Software

The strength assessment performed by the software LIMIT® incorporates a static and fatigue module to evaluate your structure. Base material as well as weld analysis can be accomplished using the commercial finite element code ANSYS (ANSYS, Inc.).

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Required import files for ANSYS weld analysis

To allow a fatigue assessment of your structure using Ansys, you have to have the .inp or .dat to access the finite element model and the .rst with all relevant result data.

Important Information for Dealing with ANSYS SHELLS

  • For a correct weld analysis the stresses on the top and bottom side of the shells must be imported into LIMIT® in the right order.
  • The default shell elements in ANSYS Workbench are SHELL181 and SHELL281. These shells have different modes of stress output to the RST-File, defined by KEYOPTION(8).
    LIMIT® supports only KEYOPTION(8)=0: „Store data for bottom of bottom layer and top of top layer”. This is the default mode of Workbench.
  • If you use these elements in APDL (ANSYS Classic) make sure the stresses are stored to the RST-file in the right order.
  • All other elements have a fixed order of writing the stresses to the RST-file and no additional settings are necessary.
  • The easiest way to check the stress data imported into LIMIT® is shown in document:
    “LIMIT-Checking-Stress-Import.pdf”.
  • In case the stresses for top and bottom are inverted, the user can switch the values.

Switching Top and Bottom Stresses During Import

Using the JobManager/KeywordEditor the following command is needed:

*SWITCH_TOP_BOTTOM_STRESS_ANSYS_SHELL, OPTION

Valid Options are:

ALL … Will switch top/bottom stresses for all shell elements or

ALL_SHELL181 …             will switch top/bottom stresses for all SHELL181 elements or

ALL_SHELL281 …             will switch top/bottom stresses for all SHELL281 elements or

ALL_SHELL43  …              will switch top/bottom stresses for all SHELL43 elements or

ALL_SHELL63  …              will switch top/bottom stresses for all SHELL63 elements or

ALL_SHELL93  …              will switch top/bottom stresses for all SHELL93 elements or

ALL_SHELL150 …             will switch top/bottom stresses for all SHELL150 elements or

ETYP#                  …            ELEMENT-TYPE-NUMBER: first integer in ET command:  ET, 7,181 => here 7

With ETYP# individual regions can be switched

Examples:

  • Example 1, two lines are defined in KeywordEditor:

*SWITCH_TOP_BOTTOM_STRESS_ANSYS_SHELL, ALL

*SWITCH_TOP_BOTTOM_STRESS_ANSYS_SHELL, ALL_SHELL181

Result: All shells are being switched, all SHELL181 are being switched a second time, so they remain in their original order.

  • Example 2, two lines are defined in KeywordEditor:

*SWITCH_TOP_BOTTOM_STRESS_ANSYS_SHELL, 7

*SWITCH_TOP_BOTTOM_STRESS_ANSYS_SHELL, 8

Result: All shells with ELEMENT-TYPE-NUMBER 8 or 11 are being switchee.

The ELEMENT-TYPE-NUMBER is defined with the Ansys-ET-command.

ET, 7,181    ….                  Element Type Number 7 uses SHELL181

ET, 8,281    ….                  Element Type Number 8 uses SHELL281

Supported ANSYS Versions in Release Package

  • 2021r1 (version 211)
  • 2020r2 (version 202)
  • 2020r1 (version 201)
  • 2019r3 (version 195)
  • 2019r2 (version 194)
  • 2019r1 (version 193)
  • 170, 171, 172
  • 160, 161, 162
  • 19x (version 190 can import data from all 19x sub releases)
  • 18x (version 180 can import data from all 18x sub releases)
  • 150
  • 145

If you need a different version please contact our LIMIT® support.

Following elements can be analyzed

Solids:

  • SOLID185 (lin. Hex-elements) (less suitable for stress assessment)
  • SOLID285 (lin. Tet-elements) (not suitable for stress assessment)
  • SOLID186 (quadr. Hex-elements) => stress gradient available
  • SOLID187 (quadr. Tet-elements) => stress gradient available
  • SOLID164 (lin. Hex-elements) (no gradients available)
  • SOLID45** (8 node Hex-element) (less suitable for stress assessment)
  • SOLID72** (4 node Tet-element) (less suitable for stress assessment)
  • SOLID73** (8 node Hex-element) (less suitable for stress assessment)
  • SOLID92** (10 node Tet-element) => stress gradient available
  • SOLID95** (20 node Hex-element) => stress gradient available

Note: ** Not available in Workbench. Can be used via geometry extraction from RST-file.

Shells:

  • SHELL93, SHELL150, SHELL281 (8 nodes)
  • SHELL43, SHELL63, SHELL181 (4 nodes)

Membranes:

  • SHELL41 (4 nodes)

 

For detailed information please refer to the Ansys interface document (.pdf) or contact our LIMIT® support.