Flexible FEA Solutions for Every Stage of the Design Cycle
By Daniel W. Pangburn, P.E.
Since I first started using ALGOR in the mid- 1980s, finite element analysis (FEA) has gone from a technology available mostly to expert analysts to a commonly used engineering design tool. While FEA is still used by expert analysts today, integration with CAD packages, automatic mesh generators and improved software interfaces have made it possible for more engineers to use FEA and put it to use earlier in the design cycle. The latest release of ALGOR software offers new features to benefit virtually every engineer, including several CAD support options, more mesh generation options, a new FEA interface and new analysis and simulation capabilities.
Full Extensibility within CAD
Until recently, I used universal geometry file imports to interface with CAD. Today, I use ALGORís InCAD technology in my consulting work because it offers several advantages. First, InCAD technology captures the exact assembly or part geometry in coordination with the CAD API, eliminating file translation problems that can arise with universal geometry file formats. In addition, it works with a variety of CAD solid modelers including
Autodesk Inventor, CADKEY, Mechanical Desktop, Pro/ENGINEER, Solid Edge and SolidWorks. Lastly, InCAD has the same interface and operations regardless of the location of CAD and FEA systems; the CAD system used; and the analysis types needed, including linear and nonlinear stress, linear dynamic stress, fluid flow, heat transfer, electrostatic and even more advanced analysis such as FEA-based motion and stress analysis. Making a full range of FEA capabilities available within a number of CAD packages gives engineers maximum flexibility in choosing compatible CAD packages and filling a wide range of analysis needs.
Wide Range of Mesh Generation Options
ALGOR offers a range of automatic finite element meshing and modeling options from automatic one-step assembly to midplane meshing to a wizard for parametrically building pressure vessels and intersecting pipes.
One-step assembly meshing is a time-saving choice for engineers who need to quickly generate unstructured FEA meshes for complex CAD assemblies. This feature creates a hybrid mesh (combines bricks on model surface with mostly bricks and a few tetrahedra inside) with no need for transitional mesh refinement. The one-step meshing can also build meshes consisting of all ďbrickĒ elements or only tetrahedral elements.
Engineers who prefer to exercise greater control over the meshing process still have the option of generating surface and solid meshes in separate processes or modifying the default mesh settings. This allows explicit control of node locations for applying forces or boundary conditions. Furthermore, Superdraw, ALGORís precision finite element model-building tool, allows nodes to be easily moved individually or in groups to achieve desired node locations irrespective of how the mesh is automatically created. In addition, the software provides built-in transitional meshing tools within Superdraw for areas of the model that have greater engineering concern. Within the CAD solid model
environment, premeshes can be viewed and adjusted, making it easier to preview meshes and make adjustments in the mesh size earlier.
Another option for engineers who make thin-walled parts or structures is to use midplane meshing for converting thin solid CAD parts and assemblies into plate/shell elements. This technology is very robust and even automatically heals the inevitable gaps that occur during midplane extraction at the intersecting surfaces.
Having worked with pressure vessel design, I am impressed by PV/Designer, a wizard that parametrically builds piping entities such as pressure vessels and intersecting pipes. This tool is ideal for the generation of FEA models for pressure vessel and piping component analyses. The wizard enables engineers to specify variables such as the dimensions and orientation of intersecting pipes as well as whether to create a plate/shell or solid model.
New Interface with Right-Click Functionality
As a long-time user of ALGOR, one big change I have noticed is the graphical user interface. The new FEA editor environment offers right-click functionality across the entire software line. This interface enables right-click application, modification and removal of loads, constraints and finite element properties for all analysis types. In addition to providing a convenient means for selecting nodes, parts and surfaces, the interface offers more feedback about selections by highlighting selected areas of a model and by listing selected
vertices in the tree view. The tree view of model parts and associated data also graphically indicates which parts have associated data and where data is needed, adding valuable perspective in the design process.
|Shown within ALGORís graphical user interface with right-click functionality is a model of a semi-trailer underride bumper. The ALGOR interface includes a tree view of model parts and associated data (left) and Windows-native functionality like multiple model views (right). Model courtesy of Daniel W. Pangburn, P.E.
The FEA editor is Windows-native and so all input screens for all loads and constraints offer standard functions such as copy and paste support. The docking toolbars can be arranged to a userís preference and multiple views of the same model can be open at the same time. The interface also provides dynamic viewing of FEA models, including automatic zooming using the scroll wheel on the mouse. The models are automatically shaded for realistic visual feedback.
Full Range of Finite Element Analysis Capabilities
Numerous CAD support options and easy-to use interfaces aside, the cornerstone of any FEA package is the range of analysis capabilities. ALGOR offers Mechanical Event Simulation with linear and nonlinear material models, static stress analysis with linear and nonlinear material models, steady and unsteady fluid flow analysis with turbulence, steady-state and transient heat transfer analysis, electrostatic analysis, linear dynamic analysis and multiphysics.
An important consideration for engineers is always processing speed. ALGORís new fast solvers use sparse solver technology to provide significantly faster processing times, especially when analyzing large CAD assemblies. Faster solvers are critical to reducing analysis run times and shortening the entire design process. This is especially important when considering stresses in a large CAD assembly for transient analysis.
Multiphysics capabilities have also been augmented. New capabilities include a forced convection heat transfer capability for considering the effects of fluid flow when solving for temperature distribution and a film convection coefficient calculator to estimate the heat transfer coefficient between a solid and adjoining fluid. These new capabilities make thermal/fluid scenarios easier to perform than ever before.
In addition to adding new multiphysics capabilities, many existing capabilities are more tightly integrated, such as thermal/structural and electrostatic/structural multiphysics capabilities. Now, the results of one analysis can be automatically applied as the input to a second analysis with just a few mouse clicks.
The most notable developments ALGOR has recently introduced focus on Mechanical Event Simulation (MES) capabilities. MES predicts motion and stresses with built-in linear and nonlinear material models. The set-up of an MES uses only physical data, rather than calculated or assumed loads and boundary conditions. Many of the recent MES enhancements enable engineers to simulate a wider range of motion scenarios.
For example, the new actuator element enables engineers to simulate axial extension and retraction in three-dimensional space as well as rotational motion. It can replicate complex, computer-controlled motion over time in any direction and it can simulate the relative axial rotation between the ends of the element. I have previously simulated actuators with solid ďpusherĒ elements and prescribed displacements, but ALGORís actuator element offers far greater control and avoids unwanted direction changes as the result of deformation. In addition, the induced forces of an
actuator can be graphed with the post-processing tool, Monitor, providing graphical results output with hard copy if desired.
||The semi-trailer underride bumper model was analyzed with ALGORís Mechanical Event Simulation (MES) software for predicting motion and stresses with built-in linear and nonlinear material models. An actuator element was used to initiate the displacement of this large deformation plastic simulation. This project required many computerized design iterations to get a cost-effective underride bumper that would pass the government specifications for withstanding forces and absorbing energy during collapse.
Another new MES element is the slider element, which is composed of three nodes where the center node follows the path created by the line between the other two nodes. This element enables engineers to simulate slots or guides within mechanisms.
Other MES utilities include the new KinePak and Timeline tools and an improved mass properties calculator, which now also calculates products of inertia. The KinePak mechanism wizard enables engineers to define links and then dynamically examine the motion of various types of basic mechanisms including, four-bar, toggle, slider/crank and levers. Timeline is a utility for editing and viewing the multiplier data associated with a time-dependent loading event. With the editor, users enter curves into a spreadsheet-style dialog or defined with built-in functions to define individual events or loads. The viewer helps engineers validate event setup by displaying curves and seeing how loads will act on a model during analysis ó activation and deactivation times and how their magnitude changes over time. Products of inertia calculation have been added to the mass properties calculator to determine the dynamic balance in spinning structures. The mass properties calculator also outputs weight, volume and center of gravity for all models.
No matter what type of analysis you choose to perform, report features are valuable for documenting the results. ALGORís Report Wizard automatically generates an HTML report with details about a model and its analysis results. In addition to data from the model files, reports can include user-defined images, animations, models in VRML format and graphical plots, including plots of actuator force vs. position graphs for a large deformation plastic analysis.
Something for Everyone
In surveying the latest release of ALGOR software, what impressed me most is that while many capabilities have been automated and ease-of-use functionality has been added to make FEA accessible to more engineers, the advanced controls upon which FEA experts depend have been maintained. Not to be overlooked is the very high productivity possible with ALGOR as a result of powerful modeling commands, seamless cooperation with CAD programs and fast desktop results.
Daniel W. Pangburn, P.E., holds B.S. and M.S. degrees in mechanical engineering and has over 47 years of experience in engineering and engineering management positions. Besides consulting, he has worked for Aerojet and Northrop Grumman Electronic Systems and holds several patents. He resides in Fullerton, California.