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#1 2019-07-07 09:58:11

Anirudh
Member
Registered: 2017-09-11
Posts: 245

Change orientation of Local Coordinate System of 1D spring/beam

Hello all,
I am currently doing a beam analysis. Its a long beam to be supported by vertical springs to be modeled by K_T_D_L. The beam gets curved along its path and I want to put spring along -Z axis at certain locations along it with variable stiffness along its axes. Since spring stiffness KX, KY, Kz depend upon X,Y,Z(global) directions, I want to use local spring element coordinate system directions to assign the values. (using keyword REPERE ='LOCAL' in AFFE_CARA_ELEM/DISCRETE)
I have printed the  local coordinate system direction using the prescribed method of IMPR_RESU/CONCEPT  into a med file and I am able to visualise the direction of X,Y, Z axis on each element.
The issue is that the LOCAL CSYS on spring element is always aligned with global CSYS. Thus, I cannot enter values parallel to beam axis in Local CSYS. If such happens to be the case, I would have to manually create vectors on curve where springs emanate downward and then calculate the angle(let it be theta) between the vector and X axis, then change Kx = Kx/cos(theta) so that I get Kx along the curve. Similarly for Ky.
I don't want to do the calculation again and again since the geometry itself can vary. Is there a method to assign orientation to local CSYS of a 1D element so that its point in a desired direction( like X being normal to a curve).
I tried using ORIE_LIGNE under MODI_MAILLAGE but so for no success. Please see attached image below for more explanation.
It has two closeup views(a 3d view on the left and Top view on the right)
Any help is really appreciated.
R4qur1N.png

Thanks and regards
Anirudh

Last edited by Anirudh (2019-07-07 10:33:29)


Attachments:
spring_orientation.png, Size: 44.73 KiB, Downloads: 31

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#2 2019-07-07 10:44:32

Anirudh
Member
Registered: 2017-09-11
Posts: 245

Re: Change orientation of Local Coordinate System of 1D spring/beam

Hi,
The same issue persists if I use nodes compounded with the curve and meshed with 0D elements so as to simulate spring with K_T_D_N. The 0D's CSYS do not follow the curve. Please see attached image.
How can I make them align with curve binormals?

Thanks
Anirudh


Attachments:
beam4_nodes.png, Size: 24.8 KiB, Downloads: 30

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#3 2019-07-08 06:55:27

jeanpierreaubry
Guru
From: nantes (france)
Registered: 2009-03-12
Posts: 3,606

Re: Change orientation of Local Coordinate System of 1D spring/beam

hello

i do not really understand where is the problem

keyword ORIENTATION in U4.42.01 can be applied to discrete elements

in chapter 6 of my book there are some hints about how to orient element
some of this could be used to apply  some offset at the root of the discrete element at mesh time in your case

jean pierre aubry

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#4 2019-07-08 08:28:40

Anirudh
Member
Registered: 2017-09-11
Posts: 245

Re: Change orientation of Local Coordinate System of 1D spring/beam

Hello,
Thank you for the response. This should surely help.

Regards
Anirudh

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