# Sierra/SD parameters for file transfer with Sierra/SM

The parameters typically needed are stress and displacement.

:::{input}
BEGIN RESULTS OUTPUT from_adagio
  Database Name = stage1.e
  Database Type = Exodus
  At Step 0, Increment = 1
  nodal Variables = displacement as displ
  element Variables = stress
END
:::
:::{input}
BEGIN RESULTS OUTPUT from_adagio
  Database Name = stage1.e
  Database Type = exodus
  At Step 0, Increment = 1
  component separator character = ""
  nodal Variables = displacement as displ
  element variables = cord_modulus as fibermod
  element variables = memb_stress as memb_stress
  element Variables = stress
  element Variables = density as fiberdensity
  element Variables = element_thickness as fiberthickness
  element variables = cord_ax as ax
  element variables = cord_ay as ay
  global Variables = timestep as timestep
END RESULTS OUTPUT_ADAGIO
:::

Next, we consider a typical Sierra/SD text input shown below.

:::{input}
SOLUTION
 case one
   receive_sierra_data
     scale=no
     lumped
 case two
   eigen
   nmodes 10
   solver=gdsw
END
 
FILE
    geometry_file   'mesh.g'
END
 
Boundary
    sideset 21
      fixed
    sideset 22
      fixed
    sideset 11
      fixed
    sideset 20
      fixed
end
 
LOADS
END
 
OUTPUTS
    disp 
END

ECHO
  INPUT
END
 
BLOCK 11
  QuadM
    layer 1
      material ply
      thickness = from_transfer
      fiber orientation = from_transfer
END
 
BLOCK 1
        material 2
END
 
BLOCK 2
        material 2
END
 
BLOCK 6
        material 2
END
 
BLOCK 5
        material 2
END
 
MATERIAL 2
  name "steel"
  E 30.0e6
  nu 0.0
  density 2.61e-4
END
 
MATERIAL ply
  name "ply"
  density  = from_transfer
  orthotropic_layer
  E1 = from_transfer
  E2 = from_transfer
  nu12 = from_transfer
  G12 = from_transfer
  percent_continuum 0.005
END
 
Tied Data
  surface 2 1
  search tolerance 0.2
  edge tolerance 1.0e-8
  method = inconsistent
END
:::

There are several sections of interest in this input deck. The syntax
involved in a Sierra/SD input is documented in the Users's Manual. Here,
we assemble an example that collects the inputs in different sections,
and highlight those areas that are different due to the SM coupling.

:::{input}
SOLUTION
  case xfer
    receive_sierra_data
    load 1
      lumped
  case two
    eigen
    nmodes 10
    solver=gdsw
END

LOAD 1
END

BLOCK 11
  QuadM
  layer 1
  material ply
  thickness = from_transfer
  fiber orientation = from_transfer
END

MATERIAL ply
  name "ply"
  density  = from_transfer
  orthotropic_layer
  E1 = from_transfer
  E2 = from_transfer
  nu12 = from_transfer
  G12 = from_transfer
  percent_continuum 0.005
END
:::

The `solution` section contains two cases. Case `one` uses the
`receive_sierra_data` solution procedure to receive the necessary data
from Sierra/SM. All data transfer occurs here, including data such as
stresses, displacements, and analysis time. The second case instructs
Sierra/SD to compute eigenvalues of the linearization of the state
received from Sierra/SM. In this case, 10 modes are requested. Also, the
GDSW solver is requested in this case. This solver is usually needed in
problems with large numbers of constraint equations that are generated
with tied data pairs.

The `boundary` section specifies nodesets and sidesets that are to be
fixed. The four edges of the plate, which are denoted by sidesets 21,
22, 11, and 20, are fixed. These boundary conditions diff from those
used in the Sierra/SM analysis. The boundary conditions in the
Sierra/SD modal analysis may be the same or differ from those used in
the Sierra/SM analysis, depending on the goals of the analysis. Only one
Boundary section is applied in the Sierra/SD input, and it applies to
the entire SD analysis.

An empty `load` section is present to avoid a warning.

In this example, Block 11 is a block of membrane elements. These
elements are currently setup as layered elements in Sierra/SD, even
though there is only one layer. Thus, the `layer 1` specification is
needed. Following this, the material name, layer thickness and fiber
orientation are needed. In this case, the latter two come in as data
from the Sierra transfer, and `from_transfer` is used in lieu of a
numerical value. If this were an uncoupled analysis, numeric values
would be used instead. The remaining four blocks are hex elements, and
thus the only required input syntax is the specification of the material
identifier.

For the 'orthotropic_layer' material many element attributes may be
specified as `from_transfer`. Table {numref}`%s <tbl:fromtransfer>`
summarizes some fields that `read_sierra_data` can input using the
`from_transfer` option for the 'orthotropic_layer' material.

:::{list-table} Orthotropic_layer Quantities Available for FROM_TRANSFER Exchange in Read_Sierra_Data.
:name: tbl:fromtransfer
:header-rows: 1

* - **Quantity**
  - **Descriptor**
* - *element attribute*
  - Nearly any element attribute that can be stored in the Exodus
    file may also be exchanged using `from_transfer`.
* - fiber orientation
  - 2D fiber orientation in a layer
* - thickness
  - 2D shell layer thickness
* - E1
  - material modulus
* - E2
  - material modulus
* - nu12
  - material modulus
* - G12
  - material modulus
* - density
  - material density
:::

Next, the two material blocks are specified. Material 2 is specified to
be an isotropic elastic material, with Young's modulus, Poisson ratio,
and material density. These values can differ from those used in the
Sierra/SM analysis, and in fact they typically are.

For example, if the two-stage approach is employed, then the stiffer
dynamic properties of the rubber would be used here, in place of the
softer properties used in the inflate-deflect analysis in Sierra/SM.

Material 'ply' corresponds to the membranes. Here, there are several
parameters that are required to fully specify the orthotropic material
properties, and density. However, all of these properties are
transferred from Sierra/SM, and thus the `from_transfer` option is used
in lieu of numerical values.

Next, we consider the Tied Data block. As mentioned earlier, the
parameters in this section are documented in the Users's Manual. Here,
we only focus on the special considerations needed for coupled
Sierra/SM-Sierra/SD analysis. In particular, the search tolerance
parameter is used by Sierra/SD to determine which nodes are in contact.
We recommend using a very small search tolerance in Sierra/SD, since at
the end of the Sierra/SM analysis the surfaces will already be in close
contact.

Finally, although the previous example did not involve pressure forces,
we note that when pressure loads are used in the Sierra/SM preload
analysis, a follower stiffness term needs to be activated in Sierra/SD.
For example, if a pressure of $0.2$ was applied to sideset 1 in the
Sierra/SM input deck, then the following block would be needed in the
Sierra/SD input deck

:::{input}
LOAD 1
  sideset 1
    pressure = 0.2
    follower = y
END
:::

Although no error will be reported if this block is left out, the
results may be inaccurate.
