Reduce Stiffness 1

[cirokos]

Hello everyone,

I am running a nonlinear analysis with imperfections included by an eigenvalue buckling analysis with a factor of 0.1-0.5 ( the max dmx from buckling analysis is 1 , units are N/mm ) but the stiffness is much higher than the experimental results. How can I reduce the stiffness in order to match the experimental?

Any tips would be really helpful.

 

[rb1957]

are you modelling the metal? jaws supporting the test specimen which is, I think, included in your measured displacements ?

If this is a standard test then "surely" people have figured out how to model the test ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[GregLocock]

First thing I'd do is put a block of steel in the rig.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[petb]

@GregLocock, very good idea. I worked a whole summer testing glass fiber beams stiffness and trying to replicate in a Fe-model. It was until the experienced lab technician telling me to do exactly this and "subtract" the rig compliance that I could match my FE-simulations to the test results. And this was a simple 4-point bending testing, not even close to the testing of sandwich core with anistropic stiffness a geometric imperfections.

 

[rb1957]

experienced lab techs (or anyone really) are worth their salt !

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[cirokos]

Hey everyone,

I am back. First of all, I would like to thank you all for helping me with this project, your tips were truly remarkable.
My project is long completed now, but the research hasn't stopped. Many of you were correct in pointing out that the data was not collected properly, we did in fact measure displacement from the testing machine and not directly from the specimen (lack of an LVDT instrument). As I was informed by another colleague the results we were getting from our measurements made the specimen look a lot more flexible than it really was.
As of now, I don't have the correct data to compare to, but this will happen in the short future and I will try to update you once again.

Thanks a lot for your contribution.