2d shell - offset

[dogbural82]

Dear all,

It was observed that by using different offset options, the contact force and strains were varied during dynamic impacting case. when setting referece surface to the top surface (offset=0.5), it gave lower impact force than when setting that to the middle surface by default. I would like to know the reason to have different results.

To set the reference surface to the top surface, i guess, represent more physical testing behaviour.

Any explanations are much appricated.

Regards,
Minki

 

[Nileo2005]

There is probably 2 things changing when you play with the shell offset options. One change could be, if you have acceleration or the like in there, offseting the material to different oreintations can change the distance between the impacting objects, ergo different impacting speeds, for example.
f initial distance wouldn't make a difference, your problem is probably due to the poisition in the shell that you are displaying the stresses of. I think, but don't quote me on this, Abaqus defaultly displays the reference surface's layer in the shell thickness. This meaning you could be putting all the thickness between your measured layer and the contact so stresses can be dissipated throughout it, or your offset to the default middle leads to measuring the stresses only half way through the shell thickness when they're more concentrated.
You can see all the section layers, default of 2 or more if you wrote them to the odb, and their stresses/forces under Results>Field Output>Section Points.