INVESTIGADORES
BERTOLINO Graciela Mabel
congresos y reuniones científicas
Título:
Derivation of Effective DKII from measured crack faces Sliding displacements
Autor/es:
GRACIELA BERTOLINO; VÉRONIQUE DOQUET
Lugar:
Tampa, USA
Reunión:
Simposio; Seventh International ASTM/ESIS Symposium on Fatigue and Fracture Mechanics; 2007
Institución organizadora:
ASTM
Resumen:
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When a
crack is submitted to cyclic shear-mode loading, crack faces
interference reduces the effective KII
and often leads to deceleration and bifurcation. The nominal KII
is thus not representative of the real displacement, stress and
strain fields at the crack tip and the effective crack driving force
has to be determined.
The
limitations of the method generally used in the literature to derive
the effective stress
intensity factor in mode II, allowance made for friction effects,
from measured crack faces displacement are discussed, based on
accurate measurements performed in a SEM during in
situ Mode II
fatigue crack growth tests on maraging steel, ferritic-pearlitic
steel and TA6V.
When
crack tip plasticity is moderate (high yield stress, low KII),
crack tip shielding by friction can be evaluated from the comparison
of measured displacements with those predicted by LEFM, but when
plasticity is important, it tends to make
displacements larger than predicted by LEFM and to hide
friction effects.
To
evaluate friction effects, measured displacements have to be compared
with those obtained by elastic-plastic
finite element simulations. Simulations combining friction and
plasticity are performed to separate both effects.
Elastic-plastic
finite element simulations of mode II crack growth through periodic
node release were also performed to check if friction-induced
decrease in effective KII
is the only reason for the deceleration of cracks or if stress/strain
redistributions as the crack propagates through its plastic zone also
play a role.