Create the Cohesive User Material

Define the complete material response for the Helius PFA cohesive material.

The MCOHE and MATUDS entries are used collectively to define a cohesive user material in a bulk data file.

1. Open the bulk data file and locate the GENUDS entry.
2. Enter the following lines below the GENUDS entry:

   MCOHE, 9002, -1, 0
   MATUDS, 9002, MCOHE, hpfa, UCOHES,
   , REAL, 12, 1.0E+7, 1.0E+7, 1.0E+7, 1.0E+3, 3.0E+3, 3.0E+3,
   ,     , 0.01

The MCOHE entry above informs MSC Nastran that material 9002 will be defined with a user subroutine.

The MATUDS entry identifies the user material subroutine and determines the damage response for material 9002.

Cohesive User Material Constants

The cohesive user material constants (UMCs) immediately follow the REAL field in the MATUDS entry. For a detailed description of each cohesive UMC, refer to Appendix B of the User's Guide.

• UMC#1 - The first constant identifies the damage criteria to use for the cohesive model. Set UMC#1 = 12 to use the Maximum Traction initiation criterion and the Energy Based evolution criterion.
• UMC#2-4 - Constants 2-4 specify the material stiffness in each principal direction.
• UMC#5-7 - Constants 5-7 specify the maximum tractions in the three principal directions.
• UMC#8 - The eighth constant specifies the total fracture energy of the cohesive material to use for energy based damage evolution. Set UMC#8 = 0.01.