Time Stepping

[BillDog103]

I am trying to stretch an oring over a rod and then compress the oring. I figured out how I could stretch the oring by tapering the begining of the rod but now I want to compress the oring and I am having a lot of problems (mostly the fact that I don't know what I am doing). Is there a way to have Cosmosworks 2005 solve restraints in a given order. I need the Oring stretch to complete before the compression. Thanks in advance.

 

[gfbotha]

I am not 100% sure about what precisely you want to achieve.

If you say compress - do you mean compress in a radial direction (i.e. flattening)? or, do you mean self-retracting into an o-ring groove?

Anyway, if like Cosmos DesignStar, I guess you might want to use different timecurves associated to different restraints. E.g.: One timecurve could already reach its peak value of 1 at time=0.5 and then stay high untill time=1. The other timecurve could first stay low and only start rising from time=0.5 onwards to reach its peak at time=1.

Gert

 

[BillDog103]

Thanks for the reply Gert,
I have been trying to adjust the time curve but it seems to have no effect on the model. I want one thing to reach a destination before the second thing comes into contact with it and I just cant make it happen. It is a non-linear study of an oring that requires a preload. I want to stretch the oring to fit over a rod and seat onto a surface perpendicular to the rod face... Then I want another face that is perpendicular to the rod to come into contact with the oring and compress it to a given %. The Oring never seems to get into place before the second perpendicular surface gets to it. Any suggestions???

 

[gfbotha]

All I can say is that I successfully used the different timecurve method to apply loads (not restraints, but still) one after the other in a nonlinear analysis. And, I could clearly observe the effect thereof.

I do not know how familiar you are with your software and this type of analysis. So, forgive me if I am mentioning stuff you already checked...
If a component has to stay at a certain position, you need to keep the timecurve high till the end of the analysis time. The analysis end time needs to correspond to the max time on your timecurves. I assume you did actually assign the relevant timecurve to each restraint, and you are using a 1 to 1 scale factor to view the results.

 

[BillDog103]

WOOOOOHOOOOOOO!!!! That was the ticket... I was using restraints, and all though I was presented with a time curve, it had no effect on the simulation. I applied a force to the oring which jumped into place in the first step and then I was able to bring the second part in under the liner time curve of its restraint. Thanks Gert, I owe you one.

 

[gfbotha]

A real pleasure, especially if things come together!
Thanks for the feedback, now we all know.