Machine Design

Something new in everyday FEA

Cynics might say there is nothing new in linear static-stress analysis (LSSA) — it's a mature technology.

CAD-like sketching tools let users quickly produce FEA models directly within the Algor Fempro single-user interface.

Automatic, unstructured meshing of the 2D leaf-spring assembly is accessed from a right-click menu option.

V15 lets users specify allowable stress values and display factor-ofsafety contours for linear-static-stress analysis. The display for the spring shows where stresses in the model are below and above specifications.

Algor's report wizard automatically generates an organized, professional report about your analysis in standard HyperText Markup Language.

Cynics might say there is nothing new in linear static-stress analysis (LSSA) — it's a mature technology. They'd be wrong, and Algor's Professional Static/LM V15 is an example of why. Recently added software features include improved CAD-like sketching and meshing for quick model creation, calculating factor of safety contours, and more. The trend to add capabilities will continue because LSSA is widely used by design engineers and even nonengineers, such as medical doctors and architects. So it is increasingly important for the user interface to be easy to learn and use.

Dedicated to LSSA, Professional Static/LM includes Fempro, an interface for finite-element modeling, results evaluation, and presentation. V15 has several new features that improve the user interface and analysis tools, making it even easier to use and faster than previous versions.

For example, the software now includes Superdraw sketching tools that let users easily draw model geometry in a modern, CAD-like manner. The tools are intuitively laid out in pull-down menus, icon toolbars, selection-based pop-up menus, and a tree view. The interface guides users along the way with lots of visual feedback, such as text instructions, cursor changes, and mouse-over and selection highlights. An unlimited undo and redo capability makes it easy to correct mistakes.

For sketches, an automatic, unstructured 2D-mesh engine is accessed through a right-click menu option. Generating a mesh preserves sketches while a dialog button allows for toggling between mesh preview and tools for modifying the sketch. With each sketch change, the mesh is automatically updated. Graphical, interactive point-and-click operations make it easy to set up contact between parts, userspecified division values, and mesh-refinement points.

V15's new Superdraw capabilities simplify first-pass or proof-of-concept analyses by letting users sketch and mesh directly within the Fempro interface, making it easy to move from concept to analyzed model. Although I still frequently build models in CAD, V15 now lets me consider the use of only one package for both modeling and analysis. Plus, Fempro makes it easy to modify CAD models and FE meshes by simply adding lines that will represent trusses, beams, springs, and rigid or gap elements in mixed-element models. The CAD-like environment also makes it easier for inexperienced engineers to learn than many other FEA packages because such users are already familiar with a CAD interface.

Specifying data for analysis is easy with Fempro. It has docking toolbars, multiple-view windows, a tree view of model parts and associated data, Windows-native data-input screens with real-time data checking for reasonable inputs and right-click functions that apply, modify, and delete loads, constraints and FEA properties. Defaults are well considered and it's easy to change them.

Professional Static/LM's capabilities include static-stress analysis with linear material models, linear contact, consideration of thermal stress, voltage-induced effects, and calculations for weight, center of gravity and mass moment of inertia. In addition, V15 has a new parallel iterative solver that provides even quicker LSSA solutions on computers with multiple processors.

The software comes with a CD of Accuracy Verification Examples containing more than 150 test problems. I have compared Algor against other widely used FEA programs and found that, with controlled inputs and identical models, the results are well within expected values (generally less than 3% deviation) and can be correlated to hand calculations within a reasonable tolerance (often less than 1% deviation for most models).

Fempro provides many ways to evaluate and present results. A few of these include transparent displays, multiplewindow displays, fast dynamic viewing controls, and customization options including user-defined color palettes and annotations. All analysis results can be displayed as contours and exported in a variety of formats including BMP, JPG, TIF, PNG, PCX and TGA. Results can be animated with AVI tools and presented in text or HTML reports.

V15 includes new capabilities for evaluating results that include realistic visualization of beam and plate elements. Seeing actual beam cross sections makes graphical presentations more meaningful and more-easily understood.

Also new are calculators for factor of safety and strain-energy density contours for linear-static studies. Determining safety factors is extremely useful during the iterative process used to optimize a design. Contours for strain-energy density are especially useful when evaluating composite structures. The purpose for using composites is generally weight-driven, so seeing areas of high-strain energy lets designers place additional material where it is most needed.

The software's report wizard is unmatched by any other FEA package. The reporting capability provides a professional look without significant effort. It is possible to extract a report straight from the software that is presentable to supervisors and clients. Press a button and select a few customizations to generate a completed report. Additional graphics and comments are easily added. At a minimum, the report is worth putting in the appendix of your own write-up.

Finally, the supporting documentation is always up to date, and the technical support staff is friendly and capable. In the Fall, V16 of the software will provide the complete Superdraw suite of modeling tools within Fempro, as well as additional analysis features for CFD, motion, and contact analysis.

Algor V15 comes from Algor Inc., 150 Beta Dr., Pittsburgh, PA 15238, (412) 967-2700,

Garland Borowski is president of Borowski Engineering & Analytical Services Inc., Mobile, Ala., a consulting firm that performs structural, thermal, and fluid analyses as well as originates advanced material designs for commercial or military programs.

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