Correlation between experimentaion and patran

[IdeaEngineer]

Hi Everybody,

I am trying to model a sandwich coupon that is under four point bending in Patran. I have done this experiment in a Lab and used strain gages to determine the strains.

My problem is my strains in experiment are not correlating with my strains from patran, however if I ask patran for the strain in the ply directly under the ply where my strain gage is located i get the same result. To clarify, my strain gage is located on the 8th ply, but in patran the strain that corelates to my strain gage is the 7th ply.


I am using 2-d elements to model my facesheets and 3-d for my core.

Does anyone have any idea what I am doing wrong? I would realy appreciate it. Thanks.

 

[40818]

More info may help.

You have a constant bending moment so whats the handcalc strain?? and how does it compare to the real & FEM?

Have you modelled the sandwich correctly and ensured that your comparing apples with apples, i.e. that the strain your looking at the FEM really is the same distance from the sandwich neutral axis as your gauge.
Not sure by how much your out, but remember that everything is an approximation.
Give more detail and you may get better answers.