Cohesive modeling in ABAQUS

1. n through-thickness stress [K] relates stress to separation t transverse shear membrane shear s Cohesive modeling in ABAQUS . 3D Cohesive Element = {dn, ds, dt }/T0

2. Cohesive modeling in ABAQUS Viscous Regularization • - represents the relaxation time • D - stiffness degradation variable of the inviscid system • Dv - stiffness degradation variable of the viscous system • Important Assumption - the viscous system relaxes to the inviscid system as t/m ∞ • Advantage - tangent stiffness matrix, during the softening regime, is positive for small time increments

3. Linking FRANC3DNG and ABAQUS for interface fracture • For all elements in mesh: • For all faces on element: • Store the element pair sharing the face and the face nodes • For all element pairs stored: • If element material id #s are different • Store bimaterial interface nodes and elements • For all interface nodes stored: • Create 2 duplicates of the node • For all interface elements stored: • Reconnect elements with duplicate nodes • Create interface elements

4. Verification and realistic models tested Applied displacement = 0.015 inch Traction, psi/inch 100 Material #1 1e7 Material #2 0.015 d, inch

5. Model results – compare with previous slide d x 0.015 inch

6. Viscous regularization for reduced computation time

7. Viscous regularization for reduced computation time

8. Additional items Investigation of viscous regularization solver technique to speed calculations has been completed. Currently working on code for the insertion of a distribution of particles (locations and sizes) into a matrix on the topological level.

9. Wish List • From MD simulation, when does the crack grow along the boundary and when does it nucleate? 20 m