CSAR Seminar
SPEAKER: Pedro M. Areias, Northwestern University
TITLE:
Cohesive Fracture in Shells Using Set-Valued Traction-Separation Laws
DATE: Wednesday, October 11, 2006
TIME: 12:00 Noon
PLACE: 2240 DCL
1304 W. Springfield Ave., Urbana, IL
ABSTRACT
We present a method to model set-valued traction-separation laws in
plate and shell fracture problems. Making use of recent developments
in Kirchhoff-Love shell analysis and also the extended finite element
method, we introduce a complete algorithm for the cohesive law and, as
a consequence, using the Barenblatt theory, for the crack path. The
application to mixed shell formulations is also illustrated where shear
stress suffers a discontinuity. The cohesive law includes softening
and unloading to origin, adhesion and contact. Pure debonding and pure
contact are obtained as particular (degenerate) cases. This approach
to cohesive crack modeling contrasts with the established
regularization methods and, despite a higher computational cost, allows
the solution of the full nonlinear complementarity problem (NCP).
A smooth root finding algorithm (based on a trust region method) is
used. A step-driven algorithm is described with a smoothed law that
can be made arbitrarily close to the exact law. Results were found to
be step-size insensitive and accurate. In addition, the method
provides the crack advance law, extracted from the cohesive law and the
absence of tip singularity.