Victoria Harris, Project Engineer, ATA Engineering, Inc Using the Femap API to Streamline Geometry Preparation and Meshing for the Shipbuilding Industry Femap Symposium 2014 May 14-16, Atlanta, GA, USA Unrestricted Siemens AG 2014 FEMAP SYMPOSIUM 2014 Discover New Insights
ATA Used Femap s API to Create New Tools for Industry-Specific Workflows Our shipbuilding customers were looking to develop Femap tools that would make common shipbuilding-industry processes more efficient. Femap s Application Program Interface (API) allows users to customize existing Femap tools for their specific needs. In collaboration with Huntington Ingalls Industries, we used the API to combine and extend existing Femap tools in new ways in order to streamline the model-building process for shipbuilders. The project was funded by NSRP. Insert Presentation Title Here (View --> Header/Footer) 2
Shipbuilders Were Looking to Make Geometry Preparation More Efficient Reduce the time it takes to go from this: to this: 3
Efficiency Improvements in Modeling Result in Large Time Savings The design and manufacturing of a ship requires the creation of thousands of analysis models of everything from the ship as a whole down to individual equipment racks For each of these models, the analyst must create meshable geometry for the object to be analyzed, from the CAD provided by the designer Tens of thousands of man-hours are spent creating meshable geometry models for many thousands of objects on each ship hull Even a modest reduction in the number of hours required to create a single analysis model results in a large reduction in the total number of man-hours per hull when the individual savings are multiplied by the thousands of analysis models that are created 4
Typical Shipbuilding Workflow Analyst receives CAD geometry from designer Unneeded features are removed from 3D CAD (fillets, etc.) 2D Geometry is prepared for meshing (holes removed, surfaces partitioned, etc.) 2D midsurface model is created from 3D model 2D Geometry is meshed Loads and boundary conditions are applied Analyst delivers report Model is solved and results are postprocessed
API Provides Ability to Combine Existing Femap Tools in New Ways Femap Application Program Interface (API) Can automate any manual process in Femap Codes are written in programming languages such as Visual Basic or C++ Can interact with other software such as Excel or Matlab This toolbox was written for Femap 10.2.1 Toolbox needed to be accessible for multiple shipbuilders API code is usually forward-compatible Program 6
Use the API Within Femap or Through Visual Studio API can be accessed as a window within Femap great for writing programs quickly You can also write programs in Visual Studio lots of debugging tools and easy GUI construction Insert Presentation Title Here (View --> Header/Footer) 7
Femap Help Has Full Documentation of Objects and Functions Insert Presentation Title Here (View --> Header/Footer) 8
Shipbuilding Toolbox Focused on Preparing Geometry for Analysis In the toolbox: Mid-surface tools Mold-line surfaces Washer boundaries Extending surfaces Surface healing Hole removal Defeaturing selection Snipe creation Model checks Loads/constraints on un-meshed surfaces Sliver surfaces List associated entities Expanded coincident element check Meshing Get nodes attached to mesh points Add mesh to group Orient beams to shell normals Miscellaneous NEI Nastran log file parsing Gravity load combinations 9
Shipbuilders Like Mold-Line Surfaces When shipbuilders create 2D surfaces from 3D geometry, they like to use a mix of mid-surfaces and mold-line surfaces. Ship models have a lot of adjacent panels with varying thicknesses. Typically the faces on one side of the panels are coplanar this is the mold-line surface. Using a mid-surfacing tool on these panels creates sheet bodies that are no longer coplanar. Mold-line Mid-surface 10
Moldline Combines Mid-surfacing Benefits with Mold-line Concept Shipbuilding analysts wanted a tool that uses the mold-line instead of the mid-surface for some solids while still mid-surfacing other solids It was also desired that the mold-line surfaces would have a thickness property assigned to them (much like a mid-surface would) The Moldline tool uses: Copy Surface command to grab mold-line surfaces some vector math to get the solid thickness the built-in Mid-Surface command for midsurfaceable solids Group tools to collect everything in one place Insert Presentation Title Here (View --> Header/Footer) 11
Problem Surfaces Needed to Be Identified Before Meshing The Meshing Toolbox can identify surfaces with an area smaller than the specified tolerance so that those surfaces can be suppressed before meshing The analysts at HII reported that because of the nature of their models, they often get sliver surfaces that are fairly large in area, but still need to be eliminated before meshing can commence Sliver surfaces 12
CheckSlivers Provides Additional Methods for Finding Problem Surfaces The CheckSlivers tool needed to have several different options for identifying and grouping surfaces The tool uses several properties and methods associated with the point, edge, and surface objects in the API. For example to check the aspect ratio of a surface, the program collects all of the edges associated with the surface, then compares the length of each edge to all the other edges. If any ratio is greater than the user-selected tolerance, the surface is added to an output group. 13
Element Warnings in NEI Nastran Can Be Imported Directly The API can be used to interact with files outside of Femap, too Analysts wanted to quickly parse the element errors and warnings that are listed in an NEI Nastran log file The API was used to read the entire log file into a Visual Basic program, hunt for keywords related to element issues, and put element IDs into a Femap group 14
Snipe Is An Example of Automated Geometry Editing It can be useful to write a program from scratch to address a repetitive task specific to your needs Shipbuilding analysts frequently cut snipe corners into their geometry; the existing methodology involved either drawing a line on the geometry or orienting a plane to make the cut The Snipe program automates the process by asking the user to define the snipe dimensions The GUI options available in Visual Studio allow for an instructional pop-up that appears when the program runs
BeamsNormaltoShells Builds From the Beams Normal to Surface Example Program The Femap installation comes with several example programs, which are useful for learning how to use the API BeamsNormalToShells expands the concept of the example Beams Normal to Surface program The program reads in the normals of any 2D elements attached to a beam element and aligns the cross-section with the average of the normal vectors
Final Thoughts About the API The easiest way to get started is to pick a simple task and figure out the steps needed to recreate it in the API Everything you need is in the documentation External editors can provide extra debugging options Once your code is up and running, ask for examples from other people to test it Enjoy!