FEMAP Freebody Deep-Dive Patrick Kriengsiri, FEMAP Development

Transcription

1 Femap Symposium 2015 Huntsville FEMAP Freebody Deep-Dive Patrick Kriengsiri, FEMAP Development Realize Innovation.

2 FEMAP Freebody Deep Dive Topics What is a Freebody? Recovering Grid Point Forces in NASTRAN Understanding Grid Point Force Output Freebodies in FEMAP Using the FEMAP Freebody Toolbox FEMAP Freebody Options Global / Local Modelling with Freebodies Additional Topics Page 2

3 What is a Freebody? Freebodies provide an insight into nodal forces and moments that are a result of surrounding finite element entities In FEMAP, freebodies can be used to display a balanced set of loads on a structure or calculate the load across an interface Freebodies are commonly used when modeling practices dictate that the resulting FE mesh is a coarse-grid mesh and is suitable as an internal loads model Commonly modelled structures are often too complicated to model in sufficient detail to obtain useable stresses Allows for forces / moments to be extracted for detail stress analysis Freebodes are heavily used (but not limited to) in the aerospace industry Page 3

4 Recovering Grid Point Forces in NASTRAN Enabling GPFORCE Output in NASTRAN Case Control Turning on the NASTRAN GPFORCE case control request is required to take full advantage of the FEMAP Freebody Tool Analysis Manager Master Requests and Conditions Output Requests Force Balance GPFORCE requests can return a large amount of data, so this option is not enabled by default Page 4

5 Recovering Grid Point Forces in NASTRAN Enabling GPFORCE Output in NASTRAN Case Control FEMAP can work with a reduced set of data including applied load (OLOAD), constraint force (SPCFORCE), and constraint equation (MPCFORCE) This is generally not recommended unless only a generic freebody display of the entire structure is all that s required Additionaly, care should be taken when not requesting GPFORCE data for the entire model Page 5

6 Understanding Grid Point Force Output NASTRAN F06 Output When the results destination is set to Print Only or Print and PostProcess GPFORCE data can be viewed in the F06 file Note that it is still recommended to read GPFORCE data into FEMAP from the OP2 file, not the F06 file Search for G R I D P O I N T F O R C E B A L A N C E G R I D P O I N T F O R C E B A L A N C E POINT-ID ELEMENT-ID SOURCE T1 T2 T3 R1 R2 R3 1 F-OF-SPC E E E QUAD E E E E E E QUAD E E E E E E-04 1 *TOTALS* E E E E E QUAD E E E E E E QUAD E E E E E E QUAD E E E E E E QUAD E E E E E E-03 2 *TOTALS* E E E E E E QUAD E E E E E E QUAD E E E E E E QUAD E E E E E E QUAD E E E E E E-02 3 *TOTALS* E E E E E E-17 Page 6

7 Understanding Grid Point Force Output NASTRAN F06 Output GPFORCE results are listed per grid and include Fxyz (T1, T2, T3) and Mxyz (R1, R2, R3) Results are separated into 4 different categories, plus a summation Elemental (discrete; per connecting flexible element) Applied (total forces / moments applied on node; single quantity per node) F-of-SPC (SPC forces on node; single quantity per node) F-of-MPC (MPC forces on node, including both constraint equations and RBE contributions; single quantity per node) *TOTALS* (total summation of all contributions; single quantity per node) For the majority of cases, this value should be near zero, indicating equilibrium at the node Page 7

8 Understanding Grid Point Force Output How GPFO Relates to Structure Freebody output can be very dependent on the nodes and elements included in the summation Determining which nodes and elements are to be used is varies based on how the model was idealized as well as what specific quantity is desired Page 8

9 Freebodies in FEMAP Freebodies in FEMAP exist as creatable objects, like nodes, elements, etc. They persist in the database This is a huge benefit for recreating freebody displays in the future Can help reduce analysis errors and rework Any number of freebodies can be displayed simultaneously Many tools exist to automate freebody-related tasks, such as creating loads and substructure modeling Page 9

10 Freebodies in FEMAP FEMAP Freebody Types There are 3 separate types of freebodes in FEMAP Freebody user selects the elements, FEMAP automatically selects related nodes. Intended to display a balanced set of loads on a discrete piece of structure Page 10

11 Freebodies in FEMAP FEMAP Freebody Types There are 3 separate types of freebodes in FEMAP Interface Load user selects both nodes and elements and FEMAP calculates a summation of loads and forces across the interface and displays as a single vector Page 11

12 Freebodies in FEMAP FEMAP Freebody Types There are 3 separate types of freebodes in FEMAP Section Cut similar to interface load, a summed load across an interface is displayed and calculated, however node and element selection is automated by FEMAP. The user selects a cutting plane, defined by a plane, vector or a curve. The cutting plane can be dynamically located within the model Page 12

13 Freebodies in FEMAP Freebody Contributions Freebody contributions in FEMAP are split into six categories Applied represents applied loads Reaction results of SPC forces MultiPoint Reaction results of MPC forces Peripheral Elements effects of elements surrounding selected elements Freebody Elements effects of elements selected by the user or by FEMAP Nodal Summation nodal summation values from the solver, not FEMAP calculated values Default contributions are Applied, Reaction, MultiPoint Reaction and Peripheral elements This provides forces and moments acting on the selected structure Page 13

14 Freebodies in FEMAP Freebody Result Vectors As previously mentioned, the NASTRAN GPFORCE request is recommended to fully take advantage of the freebody tool, however the result quantities may be obtained from several different quantities Primary Secondary Applied GPFORCE OLOAD SPC GPFORCE SPCFORCE MPC GPFORCE MPCFORCE Elemental GPFORCE None Nodal Summation GPFORCE None The italicized rows above represent default output requests in FEMAP and are sufficient for displaying a balanced freebody on the entire structure Page 14

15 Using the FEMAP Freebody Toolbox Accessing the Freebody Toolbox The Freebody Toolbox is located in the PostProcessing toolbox and can only be accessed when results are present in the model Global Settings These controls affect all freebodies in the model. Control global display of freeboides, select output set (tied to contour and deform) and enable data summation on nodes Freebody Settings These controls are related to individual freebodes, such as selecting nodes and elements View Settings These are global settings that affect freebody visualization (symbol sizes, vector scaling, etc). Same as found in F6 Page 15

16 Using the FEMAP Freebody Toolbox Creating a New Freebody In the Freebody Toolbox, new Freebodies are created within the Freebody Manager The New Freebody dialog allows for setup of basic settings, such as freebody type, vector display, and contribution selection Page 16

17 Using the FEMAP Freebody Toolbox Creating a New Freebody Any of the settings applied in the New Freebody dialog can be changed at any time within the toolbox Page 17

18 Using the FEMAP Freebody Toolbox Accessing Different Freebodies Multiple Freebodies can be displayed at any time however, only a single freebody can be active at any time within the toolbox Use the drop-down menu to change the active freebody and modify settings Display of individual freebodies can be controlled with the Is Visible checkbox as well as with the Visibility Quick View Dialog Page 18

19 Using the FEMAP Freebody Toolbox Freebody Vector Types Depending on the freebody type, there are vector quantities for nodal vectors and a single total summation vector Nodal Vectors Displays the summation at each node, based on the selected freebody contributions Available for all freebody types Total Summation Vector Displays the total summation across all nodes at a pre-defined position. The selected position does not affect summed for calculations, but will affect summed moment calculations to do the difference in moment arms Available for Interface Load and Section Cut freebodies Both force and moment vectors are available and are individually togglable Vectors can be displayed as either components or resultant vectors Individual components can be toggled on and off Page 19

20 Using the FEMAP Freebody Toolbox Freebody Vector Visualization Visibility Quick Toggle Buttons All On / All Off Forces On/Off Moments On/Off Toggle between resultant/component Select summation location (interface load and section cut only) Page 20

21 Using the FEMAP Freebody Toolbox Freebody Vector Visualization Detail Options Additional detailed options for visualization can be found by expanding the Total Summation Vector and Nodal Vector(s) nodes Select components displayed (Fx, Fy, Fz), (Mx, My, Mz) Select components included in calculation (interface load and section cut only) Page 21

22 Using the FEMAP Freebody Toolbox Freebody Coordinate Systems The selected freebody coordinate system controls the coordinate system for both nodal vectors and the total summation vector (if applicable) for the selected freebody Nodal vectors may optionally be displayed in the nodal output coordinate system If no nodal output system was specified on the node, the default coordinate system used is the global rectangular system Page 22

23 Using the FEMAP Freebody Toolbox Freebody Mode When using Freebody Mode, the user selects elements and FEMAP will automatically select related nodes This mode is designed to display a balanced set of loads on a selected set of elements Entities may be selected manually (default) or inferred for a selected group The default contribution selections will display forces/moments acting on the selected elements Select Elements Reset Element Selection Highlight Selected Elements Page 23

24 Using the FEMAP Freebody Toolbox Display of balanced set of loads on wingpost model. All elements in the model were selected for this display Page 24

25 Using the FEMAP Freebody Toolbox Interface Load Mode Interface load freebodies display nodal vectors for selected nodes as well as a total summation vector at a selected location Unlike freebody mode freebodies, interface load freebodies are not likely to be in equillibrium In addition to element selection, nodes must be selected manually FEMAP does not infer them based on the selected elements When selected entities from a group, both the nodes and elements of interest must exist in the group Page 25

26 Using the FEMAP Freebody Toolbox Interface Load Mode Selecting Nodes Locate Summation Vector at Node Centroid Select Free Edge Nodes Select Nodes Reset Node Selection Highlight Selected Nodes When selecting elements, any elements may be selected, however only those connected to the selected nodes will be used Page 26

27 Using the FEMAP Freebody Toolbox Interface Load Selecting Components in Summation Individual force and moment contributions that are included in the total summation vector calculation toggled on and off By default, all force and all moment vectors are included in the calculation Changes made here will affect the total summation calculation Turning on and off certain contributions is dependent on how the model was idealized ; it is up to the analyst to understand how the FE model correlates to real-world structure Page 27

28 Using the FEMAP Freebody Toolbox Interface Load Display, Showing Summed Shear Load at a Rib Page 28

29 Using the FEMAP Freebody Toolbox Section Cut Mode An extension to Interface Load mode The user defines a cutting plane in the model and the contributing freebody nodes and elements are determined automatically Total summation location can be placed at Plane/path intersection Nodal centroid Static location Nodal and total summation vectors can optionally be aligned tangent to the path without having to create additional coordinate systems Page 29

30 Using the FEMAP Freebody Toolbox Freebody Section Cut Modes Plane: Cutting plane is defined via base point and normal vector. Path is defined as the normal vector; cutting plane will always be normal to the path Curve: Cutting plane is normal to the tangent vector at a point along the plane. Cutting plane will always be normal to the tangent vector Plane / Vector: Similar to Plane, however an additional vector is defined for the path. The cutting plane will always remain co-planar to the original plane and does not have to be normal to the path Vector: Cutting plane is normal to the defined vector. Path is the defined vector; cutting plane will always be normal to the path Page 30

31 Using the FEMAP Freebody Toolbox Section cut defined using plane Page 31

32 Using the FEMAP Freebody Toolbox Section cut defined using curve Page 32

33 Using the FEMAP Freebody Toolbox Additional Section Cut options Slider tool can be used to move the cutting plane along the length of the path interactively within the available entities Section cut entities may be limited to a specific group or selected from the entire model, and can be limited to a search distance from the base location of the cutting plane The cutting plane can optionally be given a thickness tolerance that will allow for accurate selection of entities that are slightly out-of-plane Clipped entities can either be included or excluded from the summation calculations Page 33

34 Using the FEMAP Freebody Toolbox Cut plane initial position Cut plane moved along the path Freebody nodes Freebody elements Page 34

35 Freebody Tools List freebody to message window 2 List freebody to data table 3 List freebody summation to message window (interface load / section cut) 4 List freebody summation to data table (interface load / section cut) 5 Freebody validation tool; warns user when freebody results are potentially missing from the model Page 35

36 Global-Local Modeling with Freebodies The freebody Multi-Model Load from Freebody tool automates the creation of global-local models Used to map freebody loads from a coarse grid model to a fine grid model and automatically create connections with RBE3 elements Start with a balanced freebody in a coarse model FEMAP can automatically locate suitable target nodes in the fine grid FEM and will connect with RBE3 elements Once properly constrained, the detail FEM is ready to run with a mapped set of loads The detail FEM must exist in the same space as the part in the coarse grid FEM Page 36

37 Global-Local Modeling with Freebodies Define Target Model Parameters Freebody loads can be applied to target nodes based according to Existing nodes (IDs must match) Closest node in space to source node Existing nodes to be connected with RBE3 elements User can define target nodes or FEMAP can automatically find Search distance can be limited Maximum nodes to map can be limited Page 37

38 Global-Local Modeling with Freebodies Page 38

39 Additional Topics Freebodies with NX Nastran Glue / Contact As of NX Nastran v10.1, the GPFORCE output request does not include contributions from glue or contact in the F06 or OP2 datablock The result is a nodal imbalance that is the summation of all other contributions Nodes that are affected by glue or contact will not be in equillibrium The nodal summation quantity is equal and opposite to the existing summation G R I D P O I N T F O R C E B A L A N C E POINT-ID ELEMENT-ID SOURCE T1 T2 T3 R1 R2 R HEXA E E E HEXA E E E HEXA E E E HEXA E E E HEXA E E E HEXA E E E HEXA E E E HEXA E E E *TOTALS* E E E HEXA E E E *TOTALS* E E E Page 39

40 Additional Topics Freebodies with NX Nastran Glue / Contact In FEMAP 11.2, the ability to reverse the nodal summation value was added, allowing the nodal imbalance to be treated as a separate contribution in the equal-and-opposite direction This option should only be used if the cause of the imbalance is a result of data missing from the GPFO table and not as a result of mechanism at the node Page 40

41 Additional Topics Freebodies with NX Nastran Glue / Contact Default contributions Freebody elements / nodal summation Freebody elements + nodal summation Reversed nodal summation Page 41

42 Additional Topics Load from Freebody Tool Freebody results can be used to create loads within an existing model using the Model->Load->From Freebody tool Works with all freebody modes For interface load and section cut freebodies, total summation load can be created at a new node in the model Loads can be created in an existing load set as well as in a new load set Page 42

43 Additional Topics Load from Freebody Tool Freebody Loads Page 43

44 Additional Topics Load from Freebody Tool Created Loads Page 44

45 Additional Topics Sum Data on Nodes Option By default, freebody vectors at each node are displayed as a summation of the selected components A global setting allows for nodal quantities to be displayed as individual contributions. It affects all displayed freebodies This allows for comparison to F06 data, as well as troubleshooting of models This option is best used with the element shrink view option Page 45

46 Additional Topics Sum Data on Nodes Option ID: 342 Source Fx Fy Fz Mx My Mz ELEM ELEM ELEM Page 46

47 Q and A Page 47