yeah the first mode seems irrelevant, too high with respect the 9 Hz you're getting. Is there any possibility that the max payload is generating a gap anywhere in your structure? I highly doubt it but do you see any buckling behavior in your structure or are you near buckling when you have max...
Checking your model I noticed 2 things, that will make your pivot ratio error to go away:
1. Your CBUSH and gap stiffness are way too high. Use 1E6-1E9 but not 1E20, that will give you an ill-conditioned matrix, it's very difficult for nastran to manage and invert a matrix without numerical...
A very simple way of modeling a fuselage in an aircraft is to model it as a pressurized cylinder, then you have two principal in-plane stresses:
-Axial=PR/2t
-Hoop=PR/t
Check wikipedia for cylinder stresses. As hoop is higher I took hoop as a reference stress in a portion of the skin.
Then you...
Good observation, you're right! Thanks for the correction.
@bykncn maybe download the DTA Handbook from afgrow webpage (I think it's for free), it explains a lot on DTA for metallic structures
Hi, you get it from the ratio, thickness is constant so it cancels out, and then you have the whole width/(width that carries load at the crack position), and of course crack and hole cannot carry tension load.
I've always seen structural substantiation in aerospace for failure in terms of ultimate loads (which include a safety factor), and limit load mostly for yield deflections and special considerations.
It's double crack according to the picture. No clue why they replace KIc with Ka, never heard of it.
But yeah it looks like 2024 t3 except the KIc which is around 40 ksi sqrt(in) if I'm not wrong
But I think it was done as an illustrative example for net tension yielding...
Hi,
For the example, the Ka is very high for normal aerospace grade aluminum, therefore, probably is net tension failure due to yielding.
So you need to calculate how much stress you have in the section next to the cracks (assume width of a pitch so you don't have interaction with secondary...
Hi,
I don't see the relation between fixed support and statically indeterminate. As you could have statically determinate structures that use rigid supports...
Also is this a FE model are you trying to build? Could you provide a bit more info in the furnishing and attachment points?
I will try...
Maybe post this in the FEA simulation forum (you could get more and better answers), or in the respective software forum as the problem is not really related to composites...
I haven't used Dytran so I can't help you, but good luck!!
Yes, for 2D and 3D honeycomb it would be a good. E3 does not have a meaning in 2D shell elements. And yes, you don't put 0, just a very small value compared to the other values. If you're running a linear analysis it will be fine. For non linear you could start getting convergence issues...
