Defining Connection Damage

You can define damage behavior as part of a connection definition.

You define connector damage either as uncoupled or coupled. For uncoupled damage, you define the behavior specified separately for individual available components of relative motion. For coupled damage, you define the behavior for some or all available components of relative motion simultaneously in a coupled manner.

You can define multiple behavior definitions. For example, you can define individual behaviors for the different components of relative motion.

For more information on connector damage behavior, see Connector Damage Behavior.

This task shows you how to:

Before you begin:
  • Create a new connection or edit an existing connection. To create a connection, see Defining Connectors.
  • In the connection dialog box, click to open the Behaviors editor.
See Also
About Connectors

Define Uncoupled Damage

You can define independent damage behavior for one or more components of relative motion.

  1. In the left pane of the Behaviors editor, click next to Damage and then click on the new Damage definition.
    The Damage behavior editor appears on the right pane of the Behaviors editor.
  2. From the Coupling options, select Uncoupled.
  3. From the Force/Moment options, select Fx, Fy, Fz, Mx, My, Mz to define damage behavior in one or more degrees of freedom.
  4. Choose the Initiation criterion:
    OptionDescription
    Force Defines the damage initiation criterion in terms of forces/moments in the connection.
    Motion Defines the damage initiation criterion in terms of relative constitutive displacements/rotations in the connection.
    Plastic motion Defines the damage initiation criterion in terms of an equivalent relative plastic motion in the connection.
  5. For Force, for the initiation criterion, specify one or both of the following:
    1. Specify the Lower limit (compression).
    2. Specify the Upper limit (tension).
  6. For Motion, for the initiation criterion, specify one or both of the following:
    1. Specify the Lower limit (compression).
    2. Specify the Upper limit (tension).
  7. For Plastic motion, specify the relative Plastic Motion at which damage begins as a function of the relative Rate.
  8. From the Extrapolation options, select one of the following to define how the app handles any data that falls outside the specified range:
    OptionDescription
    Constant Uses the value equal to the nearest end point of the specified data.
    Linear Uses linear interpolation based on the slope of the curve at each end point.
  9. Optional: Select Specify damage evolution, which defines how the material degrades after one or more damage initiation criteria are met.
    1. From the Evolution type options, select one of the following:

      Option Description
      Motion Determines damage evolution based on effective plastic displacement.
      Energy Determines damage evolution based on fracture energy.

    2. If you selected Motion as the Evolution type, from the Evolution softening type options, select one of the following:

      Option Description
      Linear Defines a linear damage evolution law. Enter the relative motion at ultimate failure in the Motion at failure field.
      Exponential Defines an exponential damage evolution law. Enter the relative motion at ultimate failure in the Motion at failure field. Specify the Exponential parameter.
      Tabular Defines the damage variable directly as a tabular function of the differences between the relative motions at ultimate failure and the relative motions at damage initiation.

  10. Select Specify affected components and select the forces or moments that are consistent with the available components of relative motion affected by the damage evolution law.
  11. Choose one of the following options for the Degradation type, which specifies the contribution of this damage behavior to the overall damage effect if several damage behaviors are defined for the same connection section.
    OptionDescription
    Maximum Compares the damage value associated with this behavior to the damage values from any other damage behaviors defined for this connection section and considers only the maximum value for the overall damage.
    Multiplicative Combines the damage values for all the damage behaviors associated with this connection section in a multiplicative fashion to obtain the overall damage.
  12. If you selected Motion as the Evolution type, specify the Plastic motion at failure, which is the effective plastic displacement at the point of failure (full degradation).
  13. If you selected Energy as the Evolution type, specify the Dissipated energy, which is the fracture energy per unit area dissipated during the damage process.

Defining Coupled Damage

Before you begin: If the associated coupled plasticity definition includes at least two terms in the force potential, the data that you provide for damage evolution might also be a function of the mode-mix ratio. The mode-mix ratio defines the relative weight of the first two terms in their contribution to the potential.

See Mode-Mix Ratio, for information on how this quantity is defined.

  1. In the left pane of the Behaviors editor, click next to Damage. Click on the new Damage definition.
    The Damage behavior editor appears on the right pane of the Behaviors editor.
  2. From the Coupling options, select Coupled.
  3. From the motion Type options, select Displacement or Rotation.
  4. Choose the Initiation criterion:
    OptionDescription
    Force Defines the damage initiation criterion in terms of forces/moments in the connection.
    Motion Defines the damage initiation criterion in terms of relative constitutive displacements/rotations in the connection.
    Plastic motion Defines the damage initiation criterion in terms of an equivalent relative plastic motion in the connection.
  5. For Force, for the initiation criterion, specify one or both of the following:
    1. Specify the Lower limit (compression).
    2. Specify the Upper limit (tension).
  6. For Motion, for the initiation criterion, specify one or both of the following:
    1. Specify the Lower limit (compression).
    2. Specify the Upper limit (tension).
  7. Expand the Initiation potential options, and select the Operator:
    OptionDescription
    Sum Defines the potential as the sum of the contributions.
    Maximum Defines the potential as the contribution that yields the maximum value.
  8. If you selected Sum in the Operator field, enter a positive value in the Exponent field.

    This value is the inverse of the overall exponent in the potential definition, β, that defines a general elliptical form of the potential. The default value of 2 defines a quadratic form of the potential.

  9. To define a potential, click and enter the following data:
    1. Choose an available Component of relative motion to define the potential contribution.
    2. Enter a nonzero Scaling factor.
    3. Enter a value for the positive Exponent α.

      The positive exponent value is ignored if you selected Maximum in the Operator field.

    4. Select the H function to use to generate the contribution:

      Option Description
      ABS Uses the absolute value function to generate the contribution.
      MACAULEY Uses the Macauley bracket to generate the contribution.
      IDENTITY Selects the identity function only if the positive exponent (α) = Exponent (β) = 1.

    5. Enter the shift factor a. The default value is 0.
    6. Set the Sign for the potential contribution to POSITIVE or NEGATIVE.
  10. Optional: Select Specify damage evolution, which defines how the material degrades after one or more damage initiation criteria are met.
    1. From the Evolution type options, select one of the following:

      Option Description
      Motion Determines damage evolution based on effective plastic displacement.
      Energy Determines damage evolution based on fracture energy.

    2. If you selected Motion as the Evolution type, from the Evolution softening type options, select one of the following:

      Option Description
      Linear Defines a linear damage evolution law. Enter the relative motion at ultimate failure in the Motion at failure field.
      Exponential Defines an exponential damage evolution law. Enter the relative motion at ultimate failure in the Motion at failure field. Specify the Exponential parameter.
      Tabular Defines the damage variable directly as a tabular function of the differences between the relative motions at ultimate failure and the relative motions at damage initiation.

    3. If you are entering tabular data for the Evolution softening type, from the Extrapolation options, select one of the following to define how the app handles any data that falls outside the specified range:

      Option Description
      Constant Uses the value equal to the nearest end point of the specified data.
      Linear Uses linear interpolation based on the slope of the curve at each end point.

  11. Select Specify affected components and select the forces or moments that are consistent with the available components of relative motion affected by the damage evolution law.
  12. Choose the Degradation type to specify the contribution of this damage behavior to the overall damage effect if several damage behaviors are defined for the same connection section.
    OptionDescription
    Maximum Compares the damage value associated with this behavior to the damage values from any other damage behaviors defined for this connection section and considers only the maximum value for the overall damage.
    Multiplicative Combines the damage values for all the damage behaviors associated with this connection section in a multiplicative fashion to obtain the overall damage.
  13. Specify the Plastic motion at failure.