Spin boundary

A spin boundary condition can be applied to a group of nodes via LOAD GROUp definition. Here is a simple example that takes a block. Clamps its lower face $z=0$ and rotates its upper face $z=1$. First set up the basic geometry and boundary codes

feap  ** Example use of the SPIN option in a load group **
 0 0 0 3 3 8

! Solid elastic body
mate
 solid
  elastic isotropic 100e6 0.3


! 5x5x5 block of elements
block
 cart 5 5 5
  1 0 0 0
  2 1 0 0
  3 1 1 0
  4 0 1 0
  5 0 0 1
  6 1 0 1
  7 1 1 1
  8 0 1 1

! Fix the base of the block
! Grab the nodes on the top face of the block
eboun
 3 0  1 1 1
 3 1  1 1 1

Next construct the LOAD GROUp (in this example it is tied to proportional load 1)

! Set up the load group (under prop load curve 1)
load prop 1

 ! Spin about z-axis passing through the point (0,0,1) at a rate of 1 degree/unit time
 spin
  center 0 0 1
  normal 0 0 1
  rate   1

 ! These values are irrelevant but needed (spin imposes the motion)
 edisp
  3 1  1 1 1 

load end

Note that EDISplacement is needed to ensure that the desired nodes will be part of the load group. The given displacement values are not used as the values from SPIN are used. In this case the entire plane is rigidly rotated about the $\mathbf {e} _{z}$ axis with the center of rotation being $(0,0,1)$.

To complete the file and see the motion, add

end


batch
 plot,pers
 plot,hide
 plot,defo,1
end


batch
 prop,,1
 dt,,1
end
1,0,0,100,0,1,0,0  ! type, k, tmin, tmax, a(1:4)


batch
 loop,,10
  time
  loop,,2
   tang,,1
  next
  plot,wipe
  plot,mesh
 next
end

inte
stop