hexagon logo

How to define two different critical opening displacements for normal and shear directions in cohesive material properties?

Cohes3
marc
I am trying to define bilinear traction-separation properties for interface elements. The first picture above is taken from Marc-Mentat 2021.1.
 
In the first picture Marc prompts to enter cohesive energy, critical opening displacement and max. opening displ. for normal direction (if I am correct). Then shear/normal coefficients are entered to allow Marc to calculate traction-separation properties in shear direction. The thing that I couldn't understand is how Marc calculates the critical opening displacement in shear direction? If I am not wrong, Marc should ask a third coefficient for calculating critical opening disp. in shear direction.