HyperSizer Support Forum

Software Use => Analyzing & Optimizing Stiffened Panels => Topic started by: David Hughes on February 20, 2020, 07:53:31 AM

Title: FEA loads procesing for DSP
Post by: David Hughes on February 20, 2020, 07:53:31 AM
Hi,

I am trying to follow how HyperSizer is calculating the Discrete Stiffened Panel loads for technique 2 so as I can understand the limitations. Apologies for the long message, but I have a few questions:

1) When creating the segments there is an option to create a stringer or frame segment. What’s the difference?

2) After upgrading to v8.0.47 I noticed that there is a new DSM backdoor option:
"Modify technique 2 beam fea moments to account for stiffener height"
What does this mean? Is it something related to bar offsets, or is it the moment correction for Cruciform sections, or is it something else?

3) V8 now incorporates the integral cruciform concept into the native environment, however there is no specific documentation. Is it the same as the method/equations used for the Metal Grid Stiffened Plugin?

4) Within the FEA Loads tab why are the tension and compression tables empty?

5) Within the FEA Loads document, section 4 gives the equations for the N-sigma methods. Do similar equations apply for BAR elements using length instead of area? Also, I cannot match the standard deviation values. Is the equation missing an n term (where n=number of elems) or is it something else?
   SD = (Sum((Ni - Navg)^2*Ai)/(((n-1)/n)*Sum(Ai)))^0.5

6) Within the FEA Loads document for Discretely Stiffened Panels I believe the transformation equations are incorrect (eq. 1 to 3):
   Nxy = -Fx*cos(q)*sin(q) + Fy*cos(q)*sin(q) + Fxy(cos^2(q)-sin^2(q))
   Similar for Mxy
   Qxx = +Vx*cos(q)+Vy*sin(q)
   Qyy = -Vx*sin(q)+Vy*cos(q)

7) For the Discretely Stiffened Panel’s transverse shear summation (eq. 41), I’ve found cases when the skin load relieves the total. I haven’t noticed this for Nx,seg and I’m still working on Mx,seg. I believe the full Qx,seq equation is:
   Qx,seg = (V1 + sign(V1)*(Qxx,L*wL/2+Qxx,R*wR/2)))/(1/2*(wL+wR))
   Where:   V1 = if |V1,t|>|V1,c| then V1,t else V1,c
   Similarly for Qxx,L and Qxx,R
Test case;
   wL/2 = 100   wR/2 = 100
   Qxx,t,L = 0.5   Qxx,t,R = 6.0
   Qxx,c,L = -1.0   Qxx,c,R = -3.0
   V1,t = 200   
   V1,c = -500   
      
   V1 = -500
   Qxx,L = -1.0
   Qxx,R = 6.0

   Qx,seg = (-500 - (-1.0*100 + 6.0*100))/200 = (-500+100-600)/200 = -5N/mm
Note that the LH Skin is relieving the load.

Kind Regards,
David
Title: Re: FEA loads procesing for DSP
Post by: David Hughes on February 21, 2020, 10:34:30 AM
Hello again,

Is there a failure mode that uses Qx,seg? If not, please ignore question 7 in my previous message.

I'm struggling to calculate Mxx,seg with N-sigma method and the tension/compression loops. Could you please explain the calculation process?

Also, the DSP loads document (sect 3.4) states that the smeared ABD method is used to calculated object forces, whereas the grid stiffened plugin had a different set of equations for the reference stresses. What does v8 use now for the integral blade and cruciform concepts? How are the tension/compression loops fed into these calculations?

Regards,
David.
Title: Re: FEA loads procesing for DSP
Post by: Brent on March 11, 2020, 04:19:21 PM
Hi David,

Answers numbered below:


Lastly, can you provide the specific example you are struggling with?

-Brent