“Microsoft Excel is still probably the number-one engineering tool today,” admits Mike Wheeler, vice president and general manager of the Mechanical Business Unit for Ansys, Inc. (Southpointe, PA; www.ansys.com). There are at least two reasons for this. First, once the math is known to create a simulation, entering it into Excel is easy. Second, Excel is a pretty good link between disparate engineering tools.
But in the world of simulation, Excel’s standing is slowly changing. Data connectivity, a.k.a. interoperability, is increasingly becoming broader and deeper within heretofore standalone simulation and analysis tools. Second, unlike Excel, the simulation and analysis tools depict reality. Plus they’re doing an increasingly better job at doing that—both during the simulation and after the results are in.
A key feature of the Ansys simulation software suite version 10 is interoperability—integrating the various simulation tools that Ansys owns and has acquired in recent years. The importance of data integration is that it helps make simulations more realistic, especially the simulations that involve multiple domains, such as mechanical/structural dynamics, computational fluid dynamics (CFD), and material properties. For instance, consider fluid-structure interaction (FSI) problems in internal combustion engines, where the motion of the piston, the pressure in the cylinder, and the combustion of the fuel are all linked together. In Ansys v10, the Ansys Multi-field Solver lets CFX for fluid analysis and Ansys Multiphysics (or Mechanical) for structural analysis run simultaneously on the same or different computers. (In fact, any number of computers can be applied to the fluid part of the simulation.) What results is a simulation of an entire FSI problem, that is, a more realistic simulation of a real-world situation.
Ansys v10 can also account for inertia in rotating structures during modal, transient, and harmonic analysis, in either a stationary or rotating reference frame. Moreover, the suite’s Fatigue Module can now analyze low cycle fatigue, as well as simulate performance under anticipated cyclic loading conditions over a part’s or an assembly’s anticipated life span. Analysis results can generate contour plots of fatigue life, damage, factor of safety, and stress biaxiality, as well as rainflow matrix, damage matrix, fatigue sensitivity, and hysteresis.
All of these simulations, of course, must start with accurate geometry. Ansys DesignModeler can now show where faulty topology exists. Better, it can bidirectionally refresh geometry using parameter values from either the source computer-aided design (CAD) package or from DesignModeler. A mid-surfacing capability can create surfaces midway between pairs of solid body faces of uniform thickness; the thickness is automatically propagated to the resultant surface bodies. Where gaps are not automatically bridged, a “to next” surface extension will automatically extend a surface to all possible surfaces, thereby helping to ensure that no extensions are missed.
Interoperability is also behind Cosmos 2006, the analysis package from SolidWorks Corp. (Concord, MA; www.solidworks.com) that includes finite element analysis (FEA), motion simulation, and CFD software. This software is tightly integrated with the SolidWorks 3D mechanical design software so that users can analyze designs without exporting data or leaving SolidWorks.
This latest version of CosmosWorks, the FEA software, includes enhanced meshing that lets engineers analyze assemblies of thick and thin parts using a combination of solid, shell, and beam meshes, as well as adaptive technology to automatically refine or coarsen mesh, or both. “What’s wrong” indicators display diagnostic messages in SolidWorks if there’s an error in geometry, material, loads, or restraints from an analysis. The visual feedback eliminates poring through model and analysis data. A built-in material editor lets users add or edit linear, nonlinear, thermal, and fatigue material properties in a single step.
CosmosWorks can now simulate spot welds so that engineers can analyze sheet metal assemblies better. Before, such analysis was manually intensive. Also new is the ability to use different fatigue curves for each part in an assembly and to use load history data to define loading events.
For simulating motion, automatic mapping functions give engineers more ready-to-use mechanism setups for analyzing real-life problems. Other new features include flexible joint support that lets multiple hinges share loads equally, yielding more consistent results; nonlinear springs and dampers such as those on automobile shock absorbers; and the ability to compare results between different simulations.
Also, the CosmosFlowWorks software has multiple rotating frames of reference so users can analyze the heat and air flows in complex assemblies (e.g., electrical enclosures with two fans rotating in opposite directions). It can also analyze flows created by assemblies with non-symmetrical enclosures, such as impellers and centrifugal pumps.
MSC.Software (Ann Arbor, MI; www.mscsoftware.com) has also dutifully been integrating its vast universe of analysis products. That said, the natural pace of software revisions have given some of the individual products new features. For instance, the newest release of SimDesigner for Catia V5R14, the solid modeler from Dassault Systèmes (www.3ds.com), has a module called SimDesigner Suspension (SDS). SDS has an automatic load transfer capability so that the dynamic simulation of loads (not just stresses) in Catia can be applied to new designs. This automatic transfer of load histories is said to give rise to more realistic results because the boundary conditions deployed are based on actual simulation results. SimDesigner Fatigue, another new module, can then directly access the transient and load transfer results from SDS—no waiting for test data; no data translations—to run fatigue or “factor of safety” calculations.
Such interoperatibility plays out nicely in Catia or, some might say, “realistically” in the virtual sense. Engineers can do full motion simulations (such as vehicle dynamics and handling) and component stress, durability, and fatigue studies inside Catia rather than having to go outside of it. That’s still possible, of course, but not necessary.
Blue Ridge Numerics, Inc. (Charlottesville, VA; www.cfdesign.com) has launched CFdesign v8.0, a fluid flow and thermal simulation software package that works within the leading 3D mechanical CAD systems. Several new simulation modules come in this version. For starters, the base analysis package can account for the roughness of a wall. Rita Schnipke, chief technology officer for Blue Ridge Numerics, explains that the parts in many physical products have a wide range of relative “smoothness.” (For instance, sand castings on intake manifolds will be “rougher” than a plastic injection molded part.) This roughness influences fluid flow. CFdesign users can specify a local area of roughness, thereby moving a step closer to reality.
Several new motion modules also provide a variety of new visualizations. CFdesign can simulate the orbital motion of a rotating shaft with a whirl component. For example, a slightly imbalanced pump impeller can be calculated and the forces displayed. The software can also simulate the complex motion similar to a coin slowly spinning on a table, which appears in the design of nutating flowmeters and other positive-displacement devices. The CFdesign ability to simulate flows affected by both linear and angular motions becomes useful in, for example, sliding vane positive displacement pump design, where vanes or pistons translate radially as they rotate about a centerline. Another visualization module captures the motion of linear and torsional springs. This, with flow-driven motion, lets analysts simulate flow through, say, spring-loaded valves, enabling them to determine the flow rate required to open a valve from a fully closed position. In all of these visualizations, the engineer or analyst can hide surfaces in the 3D model to see the points of interest of the simulation. Alternatively, particular surfaces can be chosen for study, such as a specific surface on an entire car body.
The key here—where all simulation software is going—is that the portion of a part or product being simulated, analyzed, and manipulated is now a piece of a larger, more complete, more accurate simulation of the real product operating in the real world. Where “seeing is believing,” better virtual products lead to better products in reality.