Adams
integration step size started off small (HINIT), quickly increased to the maximum step size (HMAX), and stayed at the maximum except for a small drop during the run. For this model the stripchart shows that the integrator is having no issues at all with the model.
By Walter Daniel Sr. Technical Representative MSC.Software
In the Adams/View help there is more information in the topic Debugging Your Model->Using the Simulation Debugger. For a detailed description of what is displayed in the table go to the Adams/ Solver documentation for the DEBUG command.
Adams/Solver C++ the Default with 2010
Patran
With Adams 2010 the default Solver is now the C++ version. The FORTRAN Solver had been the default through Adams 2008r1. Most users won’t notice the change so why is this news? The short answer is that many newer Solver features are in the C++ version only. Two newer integrators in the C++ solver are HHT and Newmark. HHT (Hilber, Hughes, and Taylor) is based on Newmark and these techniques evolved from structural dynamics methods. These two integrators focus on speed. HHT and Newmark work well for models with many parts (e.g., wind turbines) and many contacts (e.g., tracked vehicles). Check the INTEGRATOR statement in the C++ solver documentation for more details. The C++ version of Adams/Solver can run multiple threads. This capability is called Shared Memory Parallel (SMP) processing because all the memory is on one computer. The results are highly model-dependent but can increase solution speed 10% to 50% or more. Use the Search tab in the Adams documentation to search for the term “threads” to find more information about settings and process. Did you know that the C++ Solver has a run-time function for tracking how many seconds of CPU time have been used? The function is simply CPU with no arguments. One simple use would be to create an Adams/View function measure with F(time) = CPU so that you can see how long the run took even if you aren’t watching the screen. In fact, you could use a Design Objective to capture the Last Value of the CPU measure and record it as a Response in an Adams/Insight study! Another simple application is to add a sensor with the CPU function; when the sensor detects that a certain number of CPU seconds have been used the sensor ends the simulation. This technique is useful for automatically skipping failure cases in a multiple-run study.
Adams/View Integrator Debugger Did you know that Adams/View has a built-in integrator debugger that allows you see what is happening inside the Solver? Many experienced users know about the Adams/Solver tool DEBUG/ EPRINT, but the resulting output is a rather large text file. The Adams/View debugger presents similar information in tabular and graphical format. You must be running the Internal Solver with Adams/View to use the debugger. Go to Settings->Solver->Debugging and set the radio button to On. The default is to display the Table of Error in model entities. Checking the More box will present more options. The table shows the model elements that contribute the most error to the approximate solution. If a model fails with a joint causing most of the error, it is likely that the joint is about to “lock up.” Similarly, if a single-component force with a user function causes most of the error before integration failure, it’s possible that the function is coming close to dividing by zero. One of the options exposed by the More box are stripcharts for integration step size, iterations per step, and prediction polynomial order. In this plot the
By Huy Pham Technical Representative, Global Services Post Sales Support Americas, MSC.Software
Common Patran Questions Answered New Features in Patran 2010: MSC Nastran users often call Technical Support saying, “Where does Patran put my .bdf, .f06, and .xdb? How do I control this?” All of these job files go in the working directory. Previously, this was set either with the “Start In” directory of the shortcut for Windows users, or the directory that the p3 or patran command was invoked in Unix/Linux. In Patran 2010, there’s an option that’s on by default that allows the working directory to be set as the same directory as the database directory. Some may prefer the old behavior. If so, uncheck the “Set Working Directory to Database Location” toggle on the New Database Menu. Another new feature added in Patran 2010 is web based help. The online help is a separate download and installation. It’s done this way to keep file sizes down. This means new MSC Patran users often hit the F1 key, only to find it doesn’t do anything since the online help probably wasn’t installed. In previous releases, this meant having to revisit the SDC, and then downloading, (and then waiting), and then installing this download. (More waiting.) In 2010, users can set an environment variable: P3_HELP_ DIRECTORY=http://www.mscsoftware.com/patran/patran_2010/ html_patran/. Once this variable is set, hitting the F1 key will bring up the MSC Patran help pages even if it isn’t installed. MSC Patran will grab the information it needs off the MSC website. This provides a number of advantages: • No waiting for a download and installation, or having to uninstall it later for new releases of MSC Patran. • The user will always have the latest, up to date documentation.
http://www.mscsoftware.com/ patran/patran_2010/html_patran/
Volume 1 - Winter 2011
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