Appendix B.5 - Arguments #7-9: Damage Initiation

To predict damage initiation in a Helius PFA cohesive material, you must supply valid "strength" properties of the material. These strengths are the maximum traction in each direction the material can sustain before damage initiates and stiffness of the material begins to reduce. The strengths in the local three, one, and two directions are provided via arguments 7, 8, and 9, respectively. The criterion used to predict the point in the loading history where damage begins is selected using argument 3 (see Appendix B.3). The two options are Maximum Traction and Quadratic Traction.

Maximum Traction

The maximum traction criterion initiates damages when the following condition is met:

where Sn, Ss, and St are the maximum tractions in their respective directions the material can sustain before damage initiates.

Quadratic Traction

The quadratic based criterion initiates damages when the following condition is met:

These criteria only predict when damage begins. They do not predict how damage evolves or how the material response changes after initiation. This is controlled by the damage evolution criterion selected. See Appendix B.6 for more information.