« Page 1 | 2 Acknowledging that a nonlinear simulation can be complex, ALGOR has focused on the user-interface aspect of MES software, making it comparable to setting up a static simulation, and including automated aspects to ensure convergence for faster solutions and accurate results as well as the ability to view results in real time. Motion simulation results from SolidWorks Motion provide data such as joint reactions and inertial forces; just the inputs needed for structural analysis that can be completed in SolidWorks Premium. FEA is also available as a standalone add-in to other products. Images courtesy SolidWorks
| Dennis Sieminski, director of marketing at NEi Software, echoes the thought that although you want an analysis to be close to reality, you are always making assumptions. He says, “You can do the kinematics [rigid] analysis to determine velocities and accelerations, then get forces to use as inputs with an FE [deformable] analysis. You need enough DOFs to accurately portray the model, but you also want it to mesh efficiently.” 
Motion simulation of a flat-bed scanner mechanism, evaluated with Siemens NX Motion Simulation. Image courtesy Siemens PLM Software | NEi Motion addresses these tradeoffs using a dynamics solution from Fedem Technology. In order to simulate real-world dynamic events with long time histories, an automatic super-element method within NEi Motion reduces the number of DOFs to a minimum. A simulation can be made with an assembly containing both rigid and element models, and for rigid-body analysis, simulations are based on simpler geometry rather than elements. Siemens PLM’s product family offers a full range of motion-simulation products from the kinematic capabilities within Velocity SolidEdge CAD software to the wide range of analysis capabilities in NX6. The company believes that the availability of a broad simulation portfolio within an environment saves an enormous amount of time because design changes can immediately update the motion simulation with no third-party interaction required. The integrated NX system also saves time by leveraging design conditions to define the joints in the motion analysis. Siemens is now extending the capability to include integrated motion control through a real-time analysis connection to Simulink. Richard Bush, Siemens PLM Product Manager for Simulation, says that at the start of a project you should consider the best place to work and positively impact product performance. Modern design systems like NX provide a very scalable capability that supports complex problems in a dynamically changing environment; not just simple motion but perhaps with a control-loop system involved. He cites the customer application where a German automotive OEM designed a complicated 3-section roof mechanism, saying, “They used NX Motion Simulation to drive each joint by the hydraulic motor, and check for tolerance and positioning. If there was any change in the length of a part, then the motion would update. Mass properties also translated automatically. In a changing environment, that really pays off.” | This NEi Motion analysis of a lifeboat for an offshore oil rig first examines the CAD model (left) as a rigid body to determine the velocities and angle of hitting the sea (dependent on drop height, launch-skid length, etc.). Results are then used for CFD analysis of boat/water impact. Images courtesy NEi Software | Pay Now, Pay Later?
As ALGOR’s Williams says, “The design process is always a tradeoff: how much are you going to rely on experience from the past versus physical testing versus virtual testing?” As with all aspects of modern manufacturing, spending time and money earlier in the process to determine you’re on the best design path can save you major time and money down the road. Stay tuned next month for more in-depth looks at the spectrum of motion simulation and analysis options. When Flexible Bodies help Richard Bush, Siemens PLM Software’s product manager for Simulation, explains that adding flexible bodies to a motion analysis is important when the assembly is subject to dynamic effects like sudden impacts or vibration. In addition, where there are multiple connection paths between the different parts of the assembly, flexible bodies enable correct joint forces and load paths to be identified. — PJW | | Rigid bodies & constraints | Flexible bodies & constraints | | Motion | Smooth | Sharp Impacts
Sudden Motion Vibration | | Load paths | Single | Multiple | | More Info:
ALGOR
Pittsburgh, PA AR-CAD
Los Alamos, NM The MathWorks
Natick, MA NEi Software, Inc.
Westminster, CA PTC
Waltham, MA Siemens PLM Software
Plano, TX SolidWorks Corp.
Concord, MA
Contributing Editor Pamela J. Waterman is an electrical engineer and freelance technical writer based in Arizona. You can contact her about this article via e-mail sent to DE-Editors@deskeng.com. « Page 1 | 2
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