Sierra/SD parameters for file transfer with Sierra/SM

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

The parameters typically needed are stress and displacement.

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

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.

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.

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 2.1 summarizes some fields that read_sierra_data can input using the from_transfer option for the ‘orthotropic_layer’ material.

Table 2.1 Orthotropic_layer Quantities Available for FROM_TRANSFER Exchange in Read_Sierra_Data.#
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

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.