Contact Pressure on Primary surface
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Osama Abdelaleim
Jul 19, 2020, 5:07:42 PM7/19/20
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Hi all,
I was wondering how to view the contact pressure on the primary/master contact surface.
Setting up the contact block only postprocesses the contact pressure on the slave/secondary surface. I tried example 6a and can only visualize the contact pressure on the smaller block (slave surface) but not on the larger block (master surface).
Thanks,
Osama
Christopher Wong
Sep 30, 2020, 5:33:50 PM9/30/20
to mastodon-users
Don't use postprocessors for this. Set up all of the auxiliary variables and kernels, and their contours should show up in the exodus viewer. It's been awhile since I've ran a contact model, but I think I remember that the contact forces only show up on the primary boundary (in MOOSE contact, you have boundaries and paired boundaires, i.e., slaves and masters). But, if you think about it, this isn't such a huge deal - as long as you know the contact pressure at one surface, just remember Newton's Third Law!
Set up all your variables something like this:
```
[AuxVariables]
[slip_mag]
order = FIRST
family = LAGRANGE
[]
[slip_x]
order = FIRST
family = LAGRANGE
[]
[slip_y]
order = FIRST
family = LAGRANGE
[]
[slip_z]
order = FIRST
family = LAGRANGE
[]
[slip_accum]
order = FIRST
family = LAGRANGE
[]
[force_x]
order = FIRST
family = LAGRANGE
[]
[force_y]
order = FIRST
family = LAGRANGE
[]
[force_z]
order = FIRST
family = LAGRANGE
[]
[norm_force_mag]
order = FIRST
family = LAGRANGE
[]
[norm_force_x]
order = FIRST
family = LAGRANGE
[]
[norm_force_y]
order = FIRST
family = LAGRANGE
[]
[norm_force_z]
order = FIRST
family = LAGRANGE
[]
[tang_force_mag]
order = FIRST
family = LAGRANGE
[]
[tang_force_x]
order = FIRST
family = LAGRANGE
[]
[tang_force_y]
order = FIRST
family = LAGRANGE
[]
[tang_force_z]
order = FIRST
family = LAGRANGE
[]
[friction_energy]
order = FIRST
family = LAGRANGE
[]
[stress_xy]
order = CONSTANT
family = MONOMIAL
[]
[stress_yz]
order = CONSTANT
family = MONOMIAL
[]
[stress_zx]
order = CONSTANT
family = MONOMIAL
[]
[strain_xy]
order = CONSTANT
family = MONOMIAL
[]
[strain_yz]
order = CONSTANT
family = MONOMIAL
[]
[strain_zx]
order = CONSTANT
family = MONOMIAL
[]
[stress_xx]
order = CONSTANT
family = MONOMIAL
[]
[stress_yy]
order = CONSTANT
family = MONOMIAL
[]
[stress_zz]
order = CONSTANT
family = MONOMIAL
[]
[strain_xx]
order = CONSTANT
family = MONOMIAL
[]
[strain_yy]
order = CONSTANT
family = MONOMIAL
[]
[strain_zz]
order = CONSTANT
family = MONOMIAL
[]
[]
[AuxKernels]
# set up auxillary kernels for contact variables
[slip_mag]
type = PenetrationAux
variable = slip_mag
quantity = incremental_slip_magnitude
boundary = reactor_contact
paired_boundary = soil_contact
[]
[slip_x]
type = PenetrationAux
variable = slip_x
quantity = incremental_slip_x
boundary = reactor_contact
paired_boundary = soil_contact
[]
[slip_y]
type = PenetrationAux
variable = slip_y
quantity = incremental_slip_y
boundary = reactor_contact
paired_boundary = soil_contact
[]
[slip_z]
type = PenetrationAux
variable = slip_z
quantity = incremental_slip_z
boundary = reactor_contact
paired_boundary = soil_contact
[]
[slip_accum]
type = PenetrationAux
variable = slip_accum
quantity = accumulated_slip
boundary = reactor_contact
paired_boundary = soil_contact
[]
[force_x]
type = PenetrationAux
variable = force_x
quantity = force_x
boundary = reactor_contact
paired_boundary = soil_contact
[]
[force_y]
type = PenetrationAux
variable = force_y
quantity = force_y
boundary = reactor_contact
paired_boundary = soil_contact
[]
[force_z]
type = PenetrationAux
variable = force_z
quantity = force_z
boundary = reactor_contact
paired_boundary = soil_contact
[]
[norm_force_mag]
type = PenetrationAux
variable = norm_force_mag
quantity = normal_force_magnitude
boundary = reactor_contact
paired_boundary = soil_contact
[]
[norm_force_x]
type = PenetrationAux
variable = norm_force_x
quantity = normal_force_x
boundary = reactor_contact
paired_boundary = soil_contact
[]
[norm_force_y]
type = PenetrationAux
variable = norm_force_y
quantity = normal_force_y
boundary = reactor_contact
paired_boundary = soil_contact
[]
[norm_force_z]
type = PenetrationAux
variable = norm_force_z
quantity = normal_force_z
boundary = reactor_contact
paired_boundary = soil_contact
[]
[tang_force_mag]
type = PenetrationAux
variable = tang_force_mag
quantity = tangential_force_magnitude
boundary = reactor_contact
paired_boundary = soil_contact
[]
[tang_force_x]
type = PenetrationAux
variable = tang_force_x
quantity = tangential_force_x
boundary = reactor_contact
paired_boundary = soil_contact
[]
[tang_force_y]
type = PenetrationAux
variable = tang_force_y
quantity = tangential_force_y
boundary = reactor_contact
paired_boundary = soil_contact
[]
[tang_force_z]
type = PenetrationAux
variable = tang_force_z
quantity = tangential_force_z
boundary = reactor_contact
paired_boundary = soil_contact
[]
[friction_energy]
type = PenetrationAux
variable = friction_energy
quantity = frictional_energy
boundary = reactor_contact
paired_boundary = soil_contact
[]
# Set up auxillary kernels for stress-strain tensors
[stress_xy]
type = RankTwoAux
rank_two_tensor = stress
variable = stress_xy
index_i = 1
index_j = 0
[]
[stress_yz]
type = RankTwoAux
rank_two_tensor = stress
variable = stress_yz
index_i = 2
index_j = 1
[]
[stress_zx]
type = RankTwoAux
rank_two_tensor = stress
variable = stress_zx
index_i = 0
index_j = 2
[]
[strain_xy]
type = RankTwoAux
rank_two_tensor = total_strain
variable = stress_xy
index_i = 1
index_j = 0
[]
[strain_yz]
type = RankTwoAux
rank_two_tensor = total_strain
variable = strain_yz
index_i = 2
index_j = 1
[]
[strain_zx]
type = RankTwoAux
rank_two_tensor = total_strain
variable = strain_zx
index_i = 0
index_j = 2
[]
[stress_xx]
type = RankTwoAux
rank_two_tensor = stress
variable = stress_xx
index_i = 0
index_j = 0
[]
[stress_yy]
type = RankTwoAux
rank_two_tensor = stress
variable = stress_yy
index_i = 1
index_j = 1
[]
[stress_zz]
type = RankTwoAux
rank_two_tensor = stress
variable = stress_zz
index_i = 2
index_j = 2
[]
[strain_xx]
type = RankTwoAux
rank_two_tensor = total_strain
variable = strain_xx
index_i = 0
index_j = 0
[]
[strain_yy]
type = RankTwoAux
rank_two_tensor =total_strain
variable = strain_yy
index_i = 1
index_j = 1
[]
[strain_zz]
type = RankTwoAux
rank_two_tensor = total_strain
variable = strain_zz
index_i = 2
index_j = 2
[]
[]
```
And don't forget your contact constraint object, of course:
```
[Contact]
[ssi_contact]
slave = reactor_contact
master = soil_contact # make coarser mesh the master
model = coulomb
friction_coefficient = 0.5
formulation = penalty
penalty = 1.0e8
normalize_penalty = true
[]
[]
```
Then, just set up your outputs to write an ExodusII file and open in it up in ParaView or something. This alone should give you a lot of information.
When it comes to post-processing a field variable's solution, don't even bother with PostProcessor objects. Just be sure to set up it's variable object so that it gets written to the exo file.
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