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Inside Look at a Brand New FEA Release
Engineer/reviewer Paris Altidis cites high points and low points
Paris Altidis -- Design News, April 3, 2005
Can finite element analysis (FEA) software that's fully integrated into a CAD package possibly be as impressive as software totally dedicated to structural analysis? The answer is, "yes," based on a review of COSMOSWorks 2005, which is integrated into SolidWorks.
Like any piece of software, COSMOSWorks 2005 has its strengths and weaknesses. After running the software through its paces, I found that its strength—just as advertised—is the ability it gives engineers to simulate drop tests. The time it takes to solve such a type of analysis is compensated by its benefits in the design stage since you can include all the material nonlinearities built into your models.
Among other settings in defining the drop test, you can define the friction with the surface on which it drops, the drop angle, and the direction of gravity. But there are some limitations: The surface on which the parts are "dropped" is assumed to be infinitely stiff with no damping properties. In effect, the software assumes that all objects drop on a concrete floor (that changes in next release). Also, for assemblies used in a drop test, it is not possible to include any contact or interaction between mating parts.
I was surprised to encounter some problems in defining a response plot as a means to post-process the drop-test results: The selected nodal locations are represented by a node number on the plot with no clear way to edit the location to something more meaningful to the user. Unlike other areas of COSMOSWorks, when you customize and close the plot the software doesn't retain the attributes, and you need to do them again for replotting.
As for other strengths, there is an improved user interface in all the toolbars and a feature called QuickTips. Think of the latter as context-sensitive help. The topics are related directly to the study type and the subtopic (restraints, materials, loads) in the menu structure you are trying to find an answer for.
Also, the benefit of using the software's fast solver technology shows in the quick turnaround for results. The nonlinear models still rely on external solvers, and depending on the complexity of the models it can take a considerable amount of time to converge to a correct solution. The postprocessing that takes place afterwards offers some tools to make the results more meaningful: Without going through the Design Check wizard, use of the yield Indicator will point to the location of failure in the structure. No need to plot your results one at a time since you can open multiple windows with different results.
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| Springs: Preloaded springs of a car's front suspension can now be modeled with spring connectors in COSMOSWorks 2005. Spring connectors introduced in COSMOSWorks 2004 are now enhanced to simulate compressive/tensile preload. Benefit is to solve real-life problems where springs are assembled with initial tension or compression. No other mainstream analysis offers this functionality at this time, COSMOS developers say. |
Lack of friction
Two deficiencies that bothered me: the total lack of friction between parts in contact modeling and the inability to address self-contact in parts like a collapsed seal or a rubber boot. Like in other areas of COSMOSWorks, any contact defined for a specific study becomes part of it and you can build different scenarios (studies) with different contact interfaces and an internal setting from the same core model.
COSMOSWorks can only use solid and shell elements in the modeling of parts in SolidWorks. You can make up for the lack of beam elements by substituting springs and pin connectors along with explicit definition of bolts. From a SolidWorks standpoint, a new analysis study is associated with the active design configuration, thus allowing the user to create as many FE studies as the number of configurations.
The two other interesting tools in the definition stage are the ability to tabulate actual test results or reference data for comparison in the post-processing phase as well as the definition of nonlinear material curves for time and temperature-dependent properties and SN curves for fatigue analysis.
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| Thermal Loads: Users can define thermal loads varying with temperature like convection film coefficient vs. Temp of this electronic enclosure in COSMOSWorks 2005. Thermal load parameters such as convection film coefficient, heat flux, heat power, and emissivity can change with temperature. COSMOSWorks 2005 allows users to simulate this effect. |
The first step in the model definition in COSMOSWorks is typically a material selection, which can be isotropic, orthotropic, including some nonlinear material models for rubber type (Mooney-Rivlin, Blatz-Ko, Ogden) or even Drucker-Prager for modeling plasticity in plastics. The built-in materials database has over 46,000 materials that can be accessed from www.Matweb.com for an inexpensive premium subscription. Overall, the material definition is very complete and detailed. The idea of units is very open: Users can specify whatever units they prefer in all phases of their model building and post-processing. This is especially useful in the material definition, where their sources can be limited to one unit system and conversions can be error-prone at times.
The load and boundary conditions can be defined in a number of ways. The pin, bolt, spring, or elastic supports make up for the lack of special types of elements. This version includes surface-to-surface radiation loads, along with other thermal loading, including specifying a different initial temperature for each component.
Models that have a number of symmetry planes can take advantage of COSMOSWork's symmetry boundary conditions that help reduce the model size and, if done correctly, produce identical results to a full model. For those users with access to the Motion and Floworks modules of COSMOS, just transfer the loads directly into CW with no translation.
Part of the nonlinear features is the extensive use of structural and thermal contact features. The advantage of using nonlinear materials like rubber or metals with plasticity in an analysis with contact is the closest one can get to a realistic representation of the underlying physics of the problem.
For the most part, the solver in COSMOSWorks can be invoked as soon as the meshing is complete. The software has a number of ways to not only set the mesh density but to improve it using a quality report that can be used as a diagnostics tool.
From a hardware standpoint, COSMOSWorks now allows the use of multiprocessor support (if present) for the FFEPlus solver. It can also address up to 2 Gbyte of RAM to support FE models of large assemblies.
As a CAE engineer who deals with FEA on a daily basis, I can say the transition of a new user into its advanced features will be almost transparent.
Borg Warner Automotive. Altidis has extensive experience with ANSYS, ABAQUS, MSC.NASTRAN, MSC.MARC, LS Dyna, and Dytran.
| Web Resources | ||
| COSMOSWorks finite element analysis software from SolidWorks: http://rbi.ims.ca/4389-512 | ||
