how to apply a shear load?

[jessecarterMOOSE]

Hi all, looking for an example or guidance on how to apply a shear load to a face. I've got an input file that contains the following:

[BCs]
  [load]
    type = Pressure
    boundary = top
    function = load_ramp
    variable = disp_x
  []
  [fix_x]
    type = DirichletBC
    boundary = bottom
    value = 0
    variable = disp_x
  []
  [fix_y]
    type = DirichletBC
    boundary = bottom
    value = 0
    variable = disp_y
  []      
[]

But no displacements occur. If I instead apply the Pressure to disp_y instead of disp_x, or alternatively take out the Pressure block and add a Pressure Action using the same function and boundary, I get the expected behavior, albeit a normal load rather than one applied tangent to the surface.

[GiudGiud]

Hello

Could that been it.
Did you set displacements = 'disp_x disp_y disp_z' ?
The other problem I could see is the Qp residual of return computeFactor() * (_normals[_qp](_component) * _test[_i][_qp]);
which I think here means 0 for _normal(x). So maybe try using a NeumannBC instead?

[jessecarterMOOSE]

Neumann BC seems to have the right effect. Does the magnitude of the value get interpreted the same way as Pressure BC?

[GiudGiud]

yes. the big difference is that when using the displaced mesh , the contribution to the Jacobian is the face stiffness for Pressure.
that and the normal factor I just mentioned