Define a Simulation Composite Analysis Cohesive Material

Use the appropriate entries to define the user-defined cohesive material.

The entries that collectively define a Simulation Composite Analysis user-defined cohesive material are CONNECT SERVICE, GENUDS, MCOHE, and MATUDS. Consider the entries below from an MSC Nastran bulk data file that specify a Simulation Composite Analysis user-defined cohesive material. 

CONNECT SERVICE asca 'autodesk.asca'

GENUDS, asca

MCOHE, 3002, -1, 0
MATUDS, 3002, MCOHE, asca, UCOHES
, REAL, 22, 8.0e+06, 8.0e+06, 8.0e+06, 4000., 3000., 3000.,
,     , 2.0

The CONNECT SERVICE entry defines the service identifier and service name of the user-defined service. This entry must be defined as shown above in order to connect to the Simulation Composite Analysis User-Material Subroutine library. The GENUDS and MATUDS entries will reference the service identifier defined in the CONNECT SERVICE entry.

The GENUDS entry tells MSC Nastran to pass the material data to the user subroutine at the start of a load case, start of an increment, end of an increment, and end of a load case.

The MCOHE entry specifies the cohesive material properties for a nonlinear element used to simulate delamination. 3002 is the material identification number of the cohesive material. -1 specifies that the user-defined subroutine is to be used. 0 is the default table identifier for cohesive energy vs. temperature.

The MATUDS entry defines the enhanced material model for use with Simulation Composite Analysis. 3002 represents the material identification number for the cohesive material. The MCOHE field tells MSC Nastran the name of the material entry. The asca field tells MSC Nastran the group name used for the CONNECT SERVICE statement. UCOHES tells MSC Nastran the name of the user subroutine associated with the entry. The REAL keyword indicates that the data to follow has a character type of real. The fields that follow represent the user material constants for the cohesive material specified.

Note: A separate MCOHE and MATUDS entry are required for each Simulation Composite Analysis cohesive material used in your analysis.

User Material Constants

For any given Simulation Composite Analysis cohesive material, the number of user material constants must be between 8 and 11. Appendix B provides a detailed description of each user material constant, including the range of allowable values for each constant and the impact that each constant has on the constitutive relations used to represent the material. Each of the user material constants typically defined in an analysis incorporating a Simulation Composite Analysis cohesive material are listed below along with a brief description. For a more detailed description of any particular user material constant, refer to the appropriate section of Appendix B.

  1. Damage Criteria - The first user material constant selects the damage initiation and damage evolution criteria. It is a two digit integer where the tens place holds the damage initiation criterion selection and the ones place holds the damage evolution type selection. The damage initiation flag can be 1 for maximum traction or 2 for a quadratic based criterion. The damage evolution flag can be 1 for displacement based softening, 2 for energy based, or 3 for energy based using a mixed mode power law. For example, if the first user material constant is 12, the maximum traction damage initiation criterion will be used with the energy based softening law.
  2. Stiffnesses - User material constants 2-4 specify the material stiffness in the normal, first shear, and second shear directions respectively.
  3. Strengths - User material constants 5-7 specify the maximum tractions the material can sustain before damage initiates in the normal, first shear, and second shear directions respectively.
  4. Displacement Based Damage Evolution - The following user material constant must be defined if the displacement based damage evolution is chosen.
    • Effective Displacement at Failure - User material constant 8 is a positive number which defines the difference in effective displacement at complete failure and at damage initiation.
  5. Energy Based Damage Evolution - The following user material constant must be defined if the energy based damage evolution is chosen.
    • Total Fracture Energy - User material constant 8 is a positive number which defines the total energy dissipated due to a failure. In mathematical terms, this is the area under the traction - separation curve.
  6. Energy Based Damage Evolution (Mixed Mode Power Law) - The following user material constants must be defined if energy based damage evolution with a mixed mode power law is chosen.
    • Normal Mode Fracture Energy - User material constant 8 is a positive number which defines the total energy dissipated due to a pure normal mode failure.
    • First Shear Mode Fracture Energy - User material constant 9 is a positive number which defines the total energy dissipated due to a pure first shear mode failure.
    • Second Shear Mode Fracture Energy - User material constant 10 is a positive number which defines the total energy dissipated due to a pure second shear mode failure.
    • Power Law Exponent (Alpha) - User material constant 11 is a positive exponent used in the mixed mode power law function used to determine the rate of softening in the damaged cohesive material.
Parent topic: Use a Text Editor to Convert Pre-Existing Bulk Data Files for Use with Simulation Composite Analysis