Re: A question on laminate rotor

[Wenbin Yu]

Dear Peng,

ABD matrices are defined for a plate theory. The center of aerodynamic forces or gravity should be defined somewhere along the thickness. Thus it is not a point but a surface. Otherwise, it is inconsistent with the plate theory. The transformation can be done by expressing the plate strains of the reference surface in terms of the reference surface you want to move to.

If you are using the beam theory based on VABS, the transformation formulas can be found at our assessment paper on wind turbine blade tools.

Wenbin
At 03:44 AM 2/12/2013, you wrote:

Dear Professor Yu,

My name is Peng Lv, a PhD student in ISAE, France. I am working on composite rotor.

Using classical laminate theory, I got the stifness matrix [A B;B D] for my laminate (rectangular cross section, uniform chord, stacking sequence  [45 45 0 45 45]).

This laminate is clamped at a quarter of chord, corresponding aerodynamic center.

My question is how to calculate the stiffness to aerodynamic center NOT center of gravity? This laminate will twist along aerodynamic centers or centers of gravity?

Your early reply would be highly appreciated.

Happy Spring Festival!

Best regards,

Peng

[Wenbin Yu]

Dear Peng,

I don't know of a correct way to compute GJ from classical lamination theory, let alone to correctly transform it. Why don't you use VABS directly?

Wenbin

At 09:12 AM 2/12/2013, you wrote:

Dear Professor Yu,

Thank you for your kind reply.

Currently, I still have one thing cant understand well.

I plan to calculate effective GJ of laminate from classical lamination theory, and then use this GJ in beam theory to caculate torsion based on Finite Element Analysis.

Do you think this GJ translation is correct?

Best regards,

Peng

Dear Peng,

Wenbin

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[Wenbin Yu]

Yuanhu,

For VABS, node 4-9 can be optional.

Wenbin
At 10:28 AM 2/23/2013, you wrote:

Dear Pro.f Yu,
 
   Thanks for your reply, I'm sorry to tell you that I can not post my question on google group, because an error, which said that An error (#340) occurred while communicating with the server , has happaned. I'm affraid that google's applications can not be well used in China, so can you help me to post this email on google group?
 
   By the way,  I found that the example which use QUAD8 can perform well, however, the document shows that 9 nodes are used for the second order quadrilateral element. Does it mean that the ninth node is an optional node? 
 
   Looking for your reply, thanks.
 
Best regards,
yuanhu
 
From: Wenbin Yu
Date: 2013-02-24 00:18
To: cuiyuanhu2012
Subject: Re: VABS problems
Please try to ask the question through google group so that my answers can benefit others too.

At 08:40 AM 2/23/2013, cuiyuanhu2012 wrote:

Dear Prof. Yu,
 
   I have a problem when I use VABS to do some caculations.
  The examples you provided can go smoothly and the result is clear, but VABS corrupt when the element and node informations are replaced.
  'Vrect1.dat' is the input file I used, and the elements are generated from ANSYS.
   when VABS was excuted, I can only get two result files *.ech and *.opt.
   Comparing Vrect1.dat.ech with isorect.dat.ech, I guess that the node positions and element informations are not got by VABS before VABS exit.
   Is the format of elements I used wrong? or other mistakes I have made?
   I am looking forward to your kindly reply, thanks.
 
   PS: I use win7 64bit OS.
 
Best wishes,
yuanhu 
  

[Wenbin Yu]

Yuanhu,

Your input is not correct.  The three zeros on the fourth line should not be there. Please read the manual very carefully to avoid such mistakes.

Wenbin