Copy command

@COPY_COMMAND {
@COPY_COMMAND_NAME {CopyCommandName} {
@BASE_FRAME {BaseFrameName}
@COPY_FRAME {CopyFrameName}
@BASE_EXTENSION {BaseExtension}
@COPY_EXTENSION {CopyExtension}
@BASE_INTERFACE {BaseInterfaceExt}
@COPY_INTERFACE {CopyInterfaceExt}
@PHASE {φ}
@COMMENTS {CommentText}
}
}

Introduction

In many practical situations, multibody systems present an number of identical elements that appear at different locations, but whose physical properties are identical. Consider the following examples.

  1. A helicopter rotor consists of four identical blades, denoted Blade1, Blade2, Blade3, and Blade4, placed at 90 degree angles: when the blades are defined in a local coordinate system, they become indistinguishable.
  2. A periodic structure consists of four identical unit cells, denoted Cell1, Cell2, Cell3, and Cell4, connected together at interfaces: when the unit cells are defined in a local coordinate system, they become indistinguishable. Note that two consecutive unit cells share a common interface.

The copy command allows the automatic copying of structural elements that are identical when defined in a local coordinate system. For the first example, Blade1 is defined in detail in the input file; Blade2, Blade3, and Blade4 are then generated automatically through the copy command. For the second example, Cell1 is defined in detail in the input file; Cell2, Cell3, and Cell4 are then generated automatically through the copy command.

Notes

  1. The copy command CopyCommandName copies specific elements defined in the fixed frame BaseFrameName to elements with identical physical properties but defined in the fixed frame CopyFrameName. The elements to be copied are identified by their names, which contains the extension BaseExtension. In the name of the copied element, extension BaseExtension will be replaced by extension CopyExtension.
    If the copy command specifies
    @BASE_FRAME {frameHub1}
    @COPY_FRAME {frameHub2}
    @BASE_EXTENSION {Q1Q}
    @COPY_EXTENSION {Q2Q}
    a beam element called bladeQ1Q would be copied into a new beam element called bladeQ2Q. When referred to the fixed frames frameHub1 and frameHub2, respectively, beam elements bladeQ1Q and bladeQ2Q will be identical. It is important to note that many of the components used to define bladeQ1Q must also be copied. For instance, the name of the curve defining the geometry of bladeQ1Q should end with the extension Q1Q, say curveQ1Q, so it can be copied into a curve curveQ2Q used for the definition of bladeQ2Q. All geometric components affected by the frame change must be copied whereas physical property components, such as the beam properties, are identical for both elements and should not be copied.
  2. When copying geometric entities, i.e. curves, fixed frame, points, surfaces, or triads, such entities must be defined with respect to a fixed frame. This fixed frame should be the fixed frame BaseFrameName of the copy command, or a fixed frame recursively defined with respect to the fixed frame BaseFrameName.
  3. When dealing with periodic structures, the interface entities between the repeating units should not be copied because the neighboring unit cells share these common entities. To perform this task, the interface entities are identified by extension BaseInterfaceExt. In the name of the copied interface entity, extension BaseInterfaceExt will be replaced by extension CopyInterfaceExt.
  4. When copying elements, it is common to encounter time functions. For instance, when copying a prescribed displacement element, the associated time functions must be copied as well. The copy command will copy the time function associated with the prescribed displacement element. If the time function is harmonic, the phasing angle φ will be added to the phase of each harmonic, unless the period of this harmonic Ti = 0.0.
  5. It is possible to attach comments to the definition of the object; these comments have no effect on its definition.

Example 1

Consider the following copy command.

@COPY_COMMAND {
@COPY_COMMAND_NAME {copy2} {
@BASE_FRAME {frameHub1}
@COPY_FRAME {frameHub2}
@BASE_EXTENSION {Q1Q}
@COPY_EXTENSION {Q2Q}
}
}

Next, the following fixed frame, denoted frameBladeQ1Q, is defined recursively with respect to fixed frame frameHub1.

@FIXED_FRAME_DEFINITION {
@FIXED_FRAME_NAME {frameBladeQ1Q} {
@ORIGIN { 0.0, 0.0, 2.174}
@ORIENTATION_E2 { 0.0, 1.0, 0.0}
@ORIENTATION_E3 { -0.122, 0.0, 0.993}
@IS_DEFINED_IN_FRAME {frameHub1}
}
}

Because fixed frame frameBladeQ1Q presents extension “Q1Q,” the above copy command will generate a new fixed frame, denoted frameBladeQ2Q. Fixed frames frameBladeQ1Q and frameBladeQ2Q have identical relative origin and orientations, but with respect to frames frameHub1 and frameHub2, respectively.

Next, the following point, denoted pointTQ1Q, is defined with respect to fixed frame frameHub1.

@POINT_DEFINITION {
@POINT_NAME {pointTQ1Q} {
@COORDINATES { 13.06, 0.0, 0.0}
@IS_DEFINED_IN_FRAME {frameBladeQ1Q}
}
}

Because point pointTQ1Q presents extension “Q1Q,” the above copy command will generate a new point, denoted pointTQ2Q. Points frameBladeQ1Q and frameBladeQ2Q have identical relative coordinates, but with respect to fixed frames frameBladeQ1Q and frameBladeQ2Q, respectively.

Example 2

Consider the following copy command.

@COPY_COMMAND {
@COPY_COMMAND_NAME {copy2} {
@BASE_FRAME {frameHub1}
@COPY_FRAME {frameHub2}
@BASE_EXTENSION {B1B}
@COPY_EXTENSION {B2B}
@BASE_INTERFACE {B0B}
@COPY_INTERFACE {B1B}
}
}

Next, the following edge, denoted EdgeB1B, is defined.

@EDGE_DEFINITION {
@EDGE_NAME {EdgeB1B} {
@CONNECTED_TO_VERTICES {VertexB0B, VertexB1B}
@CURVE_NAME {CurveB1B}
}
}

Because edge EdgeB1B presents extension “B1B,” the above copy command will generate an edge, denoted EdgeB2B, which will be pointing to vertices VertexB1B and VertexB2B. Note that vertex VertexB0B will not be copied because it does not present extension “B1B.”