Define a Helius PFA Cohesive Material

Use the HELIUSCZ command to define a cohesive material.

In an ANSYS input file, there is one command that collectively defines a Helius PFA user-defined cohesive material. This command is HELIUSCZ. Consider the following line from an ANSYS input file that completely specifies a user-defined cohesive material.

HELIUSCZ, MATID, NSTATV, CRIT, KNN, KTT, KSS, SN, ST, SS, CRIT PARAM 1, CRIT PARAM 2, CRIT PARAM 3, CRIT PARAM 4

An example of the HELIUSCZ command looks like:

HELIUSCZ, 101, 9, 23, 1.0E+10, 1.0E+10, 1.0E+10, 1.0E+6, 1.0E+6, 1.0E+6, 100, 200, 200, 1.25

The HELIUSCZ command calls the Helius PFA macro. The arguments provided as part of the HELIUSCZ command are passed to the macro to define the cohesive material. For any given Helius PFA cohesive material, the number of HELIUSCZ arguments must be between 10 and 13. Each of the arguments for the HELIUSCZ command is briefly described below. Refer to Appendix B for a detailed description of each argument.

1. Material ID - The first argument provides the ID of your cohesive material.
2. Number of State Variables - The second argument identifies the number of state variables (SVARs) to track for the cohesive material. This number must be at least 9.
3. Damage Criteria - The third argument 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 third argument is 12, the maximum traction damage initiation criterion will be used with the energy based softening law.
4. Stiffnesses - Arguments 4-6 specify the material stiffness in the normal, first shear, and second shear directions respectively.
5. Strengths - Arguments 7-9 specify the maximum tractions the material can sustain before damage initiates in the normal, first shear, and second shear directions respectively.
6. Displacement Based Damage Evolution - The following argument must be defined if the displacement based damage evolution is chosen.
   • Effective Displacement at Failure - Argument 10 is a positive number which defines the difference in effective displacement at complete failure and at damage initiation.
7. Energy Based Damage Evolution - The following argument must be defined if the energy based damage evolution is chosen.
   • Total Fracture Energy - Argument 10 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.
8. Energy Based Damage Evolution (Mixed Mode Power Law) - The following arguments must be defined if energy based damage evolution with a mixed mode power law is chosen.
   • Normal Mode Fracture Energy - Argument 10 is a positive number which defines the total energy dissipated due to a pure normal mode failure.
   • First Shear Mode Fracture Energy - Argument 11 is a positive number which defines the total energy dissipated due to a pure first shear mode failure.
   • Second Shear Mode Fracture Energy - Argument 12 is a positive number which defines the total energy dissipated due to a pure second shear mode failure.
   • Power Law Exponent (Alpha) - Argument 13 is a positive exponent used in the mixed mode power law function used to determine the rate of softening in the damaged cohesive material.