Learning Forum

[clicker22]

Good morning,

I am working on having a ski making contact with snow, which in this case the snow is just a plate for now. I have set up a frictional contact between the ski and the plate. I have set a fixed support to the plate. The ski has a downward force acting on it, as well as a displacement restraint so it can only move in the z axis. I have watched many videos on contact surfaces and I have followed them, to the best of ability, to solve the issues. Below are the two error messages and the warning message I receive when trying to solve. Any help would be greatly appreciated, thank you. 

An internal solution magnitude limit was exceeded. Please check your Environment for inappropriate load values or insufficient supports.  Please see the Troubleshooting section of the Help System for more information.

An internal solution magnitude limit was exceeded. (Node Number 3168, Body ski, DOF UZ) Please check your Environment for inappropriate load values or insufficient supports.  You may select the offending object and/or geometry via RMB on this warning in the Messages window.  Please see the Troubleshooting section of the Help System for more information.

Solver pivot warnings or errors have been encountered during the solution.  This is usually a result of an ill conditioned matrix possibly due to unreasonable material properties, an under constrained model, or contact related issues.  Check results carefully.

[peteroznewman]

RMB on Connections folder and Insert a Contact Tool.

RMB on the Contact Tool and Generate Initial Contact Status

Reply with a screen shot of that table.  Note: screen shots are compressed to 690 pixels wide, so try to minimize the width of the table.

If the table shows the Frictional Contact is Open, that is the reason for the solver errors.

Click on the Frictional contact and show the details.  I assume the two surfaces are the top of the snow and the bottom of the ski.  Make sure the snow is the target. There is a Flip selection if the RMB on the Contact.

Finally, click on Analysis Settings and show the details. You want Auto Time Stepping On, Initial Substeps 10, and Large Deflection On.

[clicker22]

[clicker22]

The ski is the contact body and the snow is the target. I have selected the whole geometry for each. Do they need to be the contact surfaces only?

I have changed what you mentioned in the analysis settings. There is still errors and the sky disappears from the screen, which would make sense I guess if it is not contacting the snow. 

Is the issue with how the sky is constrained?

 

I really appreciate the help, thank you. 

 

[peteroznewman]

For Static Structural, you must have the contact status as Closed for the solution to complete, your is showing a gap of 1e-2m, or 10 mm.

Is the ski geometrically touching the snow?  You can move one toward the other until they touch, then check the Contact Status again.

You get a model that runs faster if you only put the faces in the contact definition that will touch during the simulation.

 

[clicker22]

Good morning,

This is as close as I can get it without making the geometry import as one body. It is my understanding I need two separate bodies imoirted. I still get the same error codes. 

 

[clicker22]

Would it be easier if I sent you the WB file?

[clicker22]

Ok, I have made progress  by changing the pinball radius to matac the gap. If I change the formulation method to other than program controlled the orange line goes back to yellow.

How do I deal with the "snow" being inactive? 

 

 

 

 

 

Thank you!

[peteroznewman]

Glad you found the pinball radius to close the gap.  There is also a setting in the contact defintion down at the bottom. Geometry modification or something where you can say Adjust to Touch. That is perfect when the CAD has a 2e-6 gap. However, you should figure out how to create separate solids that don't get united.

Don't worry about the Inactive state, that is normal. There are two sides and it creates two contacts and decides to keep one, and make the other inactive.

Is the ski now not passing through the snow?

[clicker22]

Yes, I have interface treatment set to adjust to touch. The board seems to bounce on and off the plate. When on true scale the board is not visible in the deformation result. When the result is set to 4.2e-007 (0.5x Auto), that is when I can see the board going up and down. I check the applied force direction and it is the appropriate direction. So the ski is no longer going through the snow but is not bouncing off, for lack of a better term. 

I have both geometries set to structural steel with a 0.2 friction coefficient. This is not the end state goal but I figured it would be good for making the scenario work first. 

I have a fixed support on the snow surface. I have put the fixed surface on the top and bottom off the snow and it does not make a difference. The displacement is set so where the foot is placed and has a zero displacement in the x and y axis, it is free in the z. My goal is to limit the ski from moving but allowing the rest of the ski to experience pressures and displacement.  It appears I can not place a fixed rotation constraint with my version. 

I guess my issue is with the constraints if the system is now closed? 

 

[peteroznewman]

I don't think the contact is working if you can't see the ski with the Result set to 1.0 True...

Are Weak Springs turned on in the Analysis Setting?  That is what the ski is pushing against, not the snow.

You have to change the Analysis Settings and turn on Auto Time Stepping. Then change the Initial Substeps to 100 and the Maximum Substeps to 1000.

Also, you must have Large Deflection On.

[clicker22]

Weak springs are off. Auto time stepping is on. 

Success! 

 

 

I have large deflection on. I only tried it off because one of the error codes mentioned it. 

 

[peteroznewman]

Great, you can close this discussion my marking the post that best answered your question with Is Solution and start a New Discussion for your next question.

[clicker22]

Thank you for your help!