Simple tipping analysis

[Anonymous]

Hello all,

Trying to run (what I would think) is a simple tipping analysis in MES with nonlinear material models. Scaffolding sitting on a slab, using a prescribed displacement to lift one side up so two feet will come off the ground while pivoting on the opposite two feet. At one point I was able to pull up on the one side but it acted as if the feet were bonded to the slab. All contacts are surface contacts with friction. I've tried both low & high speed contact. I've tried automatic, surface surface, point surface, point point contact types. Now everytime I try to run an analysis it won't even start & gives me a bright red "analysis failed" at the top of the design scenario tree. Whenever this happens I have to import the model from Inventor again & start over. Eventually the red failure note will appear again. It's like the file gets corrupted after so many times changing settings & rerunning the analysis. This should be a simple analysis correct? What am I missing? See attached.

I appreciate any/all help!

[AstroJohnPE]

Here is my example. I suggest:

1. Saving the archive file.
2. Removing the ".TXT" extension, leaving just "DrPalo sliding example.ach".
3. Retrieving the archive with Simulation Mechanical. The results are included.
4. Copying my model to a new design scenario.
5. Running the new design scenario with your version. This will let you compare my results (created with Sim Mech 2014) and which ever version is being used.

[Anonymous]

Retreiving the archive file using Simulation Machanical 2016, I get what seems to be thousands of error messages saying...

please insert disk #2 of the set

central header offset was incorrect

please insert disk #8227 of the set

extra header size is invalid

please insert disk #8229 of the set

Over & over again.

[Anonymous]

There's an option to repair an archive file. I ran it on your file & it said it was successful. But when I try to retreive it again it says there are no files to open. After "repairing" the archive file, it shows 0 bytes. Previously it was 800+.

[Anonymous]

Hello,

I've followed the exact steps in John's post and I didn't find any problem. I'm running ASM 2016. Are you working locally on your machine?
I've attached an image of John's file in a copied scenario that ran without any problem in 2016

Have a nice day

[Anonymous]

Yes, I'm working locally on my machine. When I save John's archive file to my machine & try to open it, it's not finding any files.

[Anonymous]

I'll try to send an archive file of my test model. I would guess it's small enough. Maybe you can tell me what I'm doing wrong?

[Anonymous]

I discovered something interesting & scary all rolled into one.

I took my simplified three block model & picked the surfaces for the surface to surface contact using three different methods.

Picking two parts & choosing "surface contact" = a block with a tumbling movement down the slope.

Picking two parts & choosing "create contacts between parts" = a tumbling movement which seems different from above.

Picking a specific surface from each contacting part = a block that slides down & off the slope.

John & Sebastion, I'm assuming you guys specifically chose surfaces from each part that were going to be in contact?

All this time I thought it didn't matter how you chose your contact surfaces. Can this be confirmed?

Thanks.

[Anonymous]

Now that I think the sliding problem has been solved, it's time to include the incline of the structure that initiates the sliding. Again, it makes no sense what's happening. Gravity is on. It looks like it starts to slide like it should, but then the upward trajectory. See attached.

[AstroJohnPE · Accepted solution]

I think the load curve for the gravity load does not extend for the entire duration. My guess is that it stops at 1 second. Beyond that, the multiplier is 0.

[Anonymous]

Thanks John. The gravity load curve was the issue. The beams are sliding off & falling as they should.

I still can't get it to run using a prescribed displacement to lift the one side of the structure. It keeps aborting the analysis. Is there a reason for this? Using a force to lift it will run without issue.

[Andrew.Sartorelli]

Hi DrPalo,

Can you upload your most recent version of the file?

Thanks,
Andrew

[Andrew.Sartorelli]

Hi DrPalo,

I've had a chance to review your most recent file, the issue the analysis won't run is that there is a fixed constraint on the same degree of freedom that has a prescribed displacement on a kinematic part. This is not something that is allowed by the solver, AstroJohn did a good job explaining this in a previous discusssion:

A PD is applied to a part defined as kinematic elements, and the kinematic element part has some constraints. Although the constraints may allow some motion, such as rotating about a point, the combination of the constraint and infinitely rigid part does not allow the PD to move entirely at freedom. The software doesn't check if the PD motion is within the range of motion of the kinematic element part; it just says that it is not allowed. For example, imagine a 50 mm lever that is constrained so that it can only rotate, and a PD is applied to the other end. A PD with a motion of 25 mm may be theoretically acceptable because the lever can rotate that much. A PD with a motion of 125 mm is not possible because a 50 mm lever can only displace 100 mm as it rotates 180 degrees. Since the elements are kinematic, there is no way to get the extra 25 mm of travel, so the software stops the analysis. On the other hand, an elastic lever can move 100 mm as the lever rotates 180 degrees as a rigid body, and then (hypothetically) stretch 25 mm to complete the PD of 125 mm. Therefore, the analysis will run.