Expanded CAD to FEA solid model meshing refinement for greater accuracy

Citation

(1998), "Expanded CAD to FEA solid model meshing refinement for greater accuracy", Aircraft Engineering and Aerospace Technology, Vol. 70 No. 5. https://doi.org/10.1108/aeat.1998.12770eab.016

Expanded CAD to FEA solid model meshing refinement for greater accuracy

Expanded CAD to FEA solid model meshing refinement for greater accuracy

Keywords Algor, CAD, Finite element analysis, Software

Algor, Inc. has extended its CAD to FEA solid model meshing capabilities to promote more efficient surface mesh refinement and more accurate FEA results.

Algor FEA software works directly with both wireframe and solid models from virtually any CAD system. Algor customers use Merlin Meshing Technology (MMT) to create or enhance the surface mesh. Then Algor's solid mesh engines build a 3-D solid mesh from the surface in, consisting of one of three design choices:

1. 1.

   all-brick,

2. 2.

   tetrahedral, or

3. 3.

   hybrid.

which combine bricks on the surface and tetrahedron on the inside.

A high-quality surface mesh is important because the FEA solid mesh is based on the surface. Also, loads and boundary conditions are applied to the surface where stress levels tend to be highest. Thus, MMT's high-quality surface meshes are essential for accurate analysis results.

The following enhancements are thought to make surface mesh optimisation even easier and faster than before:

• •

  MMT now preserves more surface information of a solid model from one mesh refinement iteration to the next. This means MMT users do not need to re-enter model data each time they enhance a model's surface mesh. FEA properties and boundary conditions can also be transferred between MMT iterations without re-entry.

• •

  MMT's ability to handle IGES trimmed-surface file information has been improved so CAD drawings are more easily converted to FEA models, where they are available to Algor's entire suite of FEA processors, including mechanical event simulation for virtual prototyping.

• •

  Feature lines define the surface edges and trimming lines of a CAD model and provide the basis for the surface mesh. MMT now identifies feature lines by assigning them a unique colour, so they will be recognized as feature lines in subsequent surface mesh enhancements. This enables users to preserve more of their CAD file information in Algor FEA software.

• •

  Four-, six- and eight-node meshing has eliminated the use of pentahedral elements, therefore, the overall FEA solid mesh contains fewer, better-shaped elements. This decreases analysis run times and promotes accuracy.

• •

  An auto-shaded rendering feature displays shaded surfaces, concealing internal lines and nodes. This feature enables users to work only on the model surface to more efficiently inspect the model geometry for flaws. Users also can more easily add loads and boundary conditions to shaded surfaces.

Soon Algor users will be able to bring entire CAD solid model assemblies into Algor at one time with Houdini, Algor's CAD solid model to FEA software tool. Thus, the placement and relationship of components to each other will be retained while preserving individual component properties. It will be especially useful when analysing the dynamic interaction of components within an assembly using Algor's Mechanical Event Simulation for Virtual Prototyping.

Algor, Inc. provides finite element analysis, Mechanical Event Simulation for Virtual Prototyping, CAD interfacing and piping analysis products to more than 16,000 engineers located in over 60 countries. In addition, the Algor Publishing Division offers books, videos and multimedia products which help engineers achieve better design, simulation and analysis with virtually any engineering software.

Algor, Inc. has also announced enhancements to its Monitor program that provide even more viewing features during actual analysis processing. Monitor version 1.02 offers a new Fast Fourier Transform feature, reaction force and maximum stress functions and improved display options.

"Until Monitor was developed, engineers could not view and interpret analysis results until they were processed," said Michael L. Bussler, president and CEO of Algor, Inc. "Monitor makes results available as line data as the processor turns them out, so engineers can determine the accuracy of their analysis as it's running."

Monitor is available with Accupak/VE Mechanical Event Simulation software for Virtual Prototyping and can be used with any time-dependent Algor processor since it tracks analysis results over time. In addition to displacement, velocity and acceleration, Monitor users can now view frequency response, reaction forces and maximum stresses as analyses are processed. If undesirable effects are produced, an engineer can stop the analysis and make adjustments to the FEA model without waiting until the processor run is finished. By using Superview, Algor's visualisation program, engineers can view the dynamic event as it is processed on the computer screen.

Monitor's new Fast Fourier Transform (FFT) converts displacement versus time into frequency versus amplitude so design engineers can see the frequency response of a model in a dynamic event. FFT output can be compared to a linear natural frequency analysis to determine if resonance occurs.

"Monitor's FFT feature is invaluable to any engineer in most industries who must design parts to avoid destructive vibration," Mr Bussler said.

A new Monitor option reportedly enables engineers to monitor reaction forces at nodes within a prescribed displacement. By viewing reaction forces versus displacement, an engineer can determine the stiffness behaviour of a system. This is helpful for determining other properties, such as linear natural frequency and geometric or material failure. For example, in the design of a light switch, an engineer knows the displacement that occurs between the on and off positions. The engineer can determine the amount of force needed to displace the switch by viewing the reaction forces.

With the addition of the maximum stress feature, Monitor now automatically plots the maximum stress for the entire model at each time step and indicates the time step during which peak stresses occur. From this information, an engineer can determine at what point in an event maximum stress occurs. For example, if Accupak/VE is used to simulate two rotating gears using contact elements, a mechanical engineer may determine that maximum stress occurs not when two gear teeth first make contact at the top of the rotation, but as the contacting teeth move through the rotation. Once peak stresses are identified, Monitor users can view the complete stress display for that time step in Superview and determine the location of the stresses on the model.

Monitor always displays the latest results on the screen thanks to a new scrolling capability that plots data much like an oscilloscope. Thus, engineers can more easily view graphs of detailed mechanical event simulations, which may exhibit complex patterns of dynamic behaviour. Monitor's added zoom and enclose options enable engineers to enlarge just a portion of a Monitor graph or display the entire graph in one window. Further, Monitor users can now save their individual model and global viewing settings to reflect general viewing preferences.

For further details Tel: +1 412 967 2700; Fax: +1 412 967 2781.