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Chris Coker

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Chris Coker last won the day on April 22

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  1. Please check out our examples library at: https://altairhyperworks.com/motionsolve-models/ Example MV08 is something pretty close to what you are trying to do, I think. This is a non-trivial problem, especially for a new user, so hopefully the example model will provide you with the right guidance.
  2. 1. verify that Motionview is exporting an .xml file. 2. verify that you have actually installed the solvers when you installed Hyperworks <- This is probably the #1 issue when new users say "nothing happens when they click run"
  3. to get a 50 mm total travel with that sine function, you need to divide 50/2. Amplitude of the sine function is not the peak to peak amplitude, it's half.
  4. There is no image loading. You will have to repost the image, or find a different way to communicate the issue you are having. Chris
  5. As long as you are using geometry imported through the "Import CAD/FE using Hypermesh" workflow, I think it should work. If you are importing CAD through File -> Import Geometry, this brings in CAD (typically parasolids), this may not work.
  6. Ok, after speaking with our developers, there is a relatively new feature/function you may want to consider: MotionSolve entity Sensor_Proximity and PROXIMITY function "The Sensor_Proximity element defines a sensor between two bodies which monitors their minimum separation. The sensor tracks the state of interference of the two bodies, the minimum distance between them, and the coordinates of the pair of closest points. These quantities can be accessed using the PROXIMITY function for use in defining expressions or for plotting." The documentation for it is here: https://altairhyperworks.com/hwhelp/Altair/2019/help/ms/topics/solvers/ms/sensor_proximity.htm Some caveats from the docs: Doesn't work with flexible bodies Works with basic graphic primitives, and geometry that's been imported as .h3d (tria mesh).
  7. If you are using contacts in your model, the .cof file stores the max penetration between contacts. You can also review this graphically by loading in an automated report template, under Analysis -> View reports. Tutorial MV-1010 provides some step by step instructions on this. If your model does not have contacts, there are some techniques for doing this with the interference checking feature in HyperView. Tutorial "MV-5010 Rigid Body Animation - Advanced" provides you the necessary details
  8. Did you create this model in inspire, and then export the .mdl and load the .mdl into MotionView? It appears that you did not. If so, you can use the CAD feature recognition option (under Tools -> Options -> Build model, make sure that box is checked). Then when you create a joint, etc. you can hover the mouse over your different CAD parts, and pick faces, centers of holes, etc to create points. FYI, you can do this with any CAD that has been brought into MotionView via the File -> Import Geometry workflow. From the appearance of your model it appears you used the import CAD from FE/Hypermesh. This converts the CAD into h3d and meshes it. You should be able to access nodes from that, but it isn't as efficient as using the File -> Import Geometry workflow. It seems like you are very new to the tools. We have some very good tutorials built into our help, if you search for MV-100 that will take you to the very first MotionView tutorial.
  9. I would suggest investigating the integrator settings you are using. If you are using the default parameters, those are usually not sufficient when using contacts. Under simulation settings You also need to be careful about the contact parameters. There is an entire section on best practices for contacts in our help. If you have even a slight initial penetration of the cylinder with the ramp, there will be an initial spike in forces. FYI, there is an online class for MotionView being offered next week. I would highly recommend you sign up for it, if space is still available.
  10. One possible suggestion: Make sure you are applying not only an initial rotational velocity to the cylinder, but the equivalent translational velocity as an initial condition. If you are only applying an initial rotational velocity, the cylinder is just spinning, and not translating at t=0. Therefore some energy is lost as the cylinder starts to accelerate. Edit: This is exactly the issue. I was able to reproduce your problem quickly on my end with a simple model. You need to specify the translational and rotational initial conditions. If you set the problem up correctly like this, you will find that you will not even need friction to solve the problem. Friction really isn't needed in the analytical solution either. Friction in contacts (or joints) should only be used when absolutely necessary to solve for the physics of a particular problem. Using friction requires knowlege of the correct friction to use, and how to apply it correctly. You will find that in most MBS problems, friction really isn't needed. Often we will add viscous damping to a model, as an approximation for friction, as it's numerically much more efficient.
  11. Can you also provide the model? There are many possible things to consider here, not just mesh refinement on the contacts. While the textbook problem is relatively trivial, using a multibody dynamics code to reproduce these results is not as easy as it appears to be at first. Contacts + friction always add a lot of numerical complexity to the solution.
  12. Tutorial MV-1035 Analysis of a retractable landing gear takes you through the basics of adding outputs. Note that the most typical use case is to output Forces on the Body, as this is what is commonly used to calculate loads for FEA. A joint is really just a constraint between two bodies. The forces are still acting on the two bodies. Therefore the force on the joint is just the reaction force on the body. when you create an output, you first select the type (Displacement, velocity, acceleration, Force, etc), and then you are given options about which entity you want to select for the output (Joint, Spring, Force, Body, etc) based on your selection. Note that outputs are by default reported in a global reference frame. If you need to output data in a different reference frame, you should create a marker, or use one of the implicit markers. It sounds like you should also take advantage of our online training classes as well. You can signup for those on the main altair hyperworks website.
  13. Update from our developers: The Hyperelastic material model used by MotionSolve for NLFE assumes a straight relaxed configuration. We'll work on improving the software to remove this assumption.
  14. The displacements are essentially zero. .0004 mm. With performing a thorough convergence study on integrator parameters (as recommended previously) I was able to get this model to run with minimal transients for .1 seconds. I agree that the trends are a little strange, so I've reached out to our developers to see if they have any suggestions. I'll follow up here when I learn something new. But it's very likely that what we are seeing here are numerical artifacts of such a small part, with small mass, inertia, stiffness, etc. Note, this is a rather strange usage of NLFE. For typically applications (belts, cables, coil springs, torsion bars), using NLFE within the context of a complete model produces resonable, reliable results.
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