TY - RPRT

T1 - Analysis of steady-state ductile crack growth

AU - Niordson, Christian

PY - 1999

Y1 - 1999

N2 - The fracture strength under quasi-static steady-state crack growth
in an elastic-plastic material joined by a laser weld is analyzed.
Laser welding gives high mismatch between the yield stress within
the weld and the yield stress in the base material. This is due to
the fast termic cycle, which the material undergoes in welding.
The elastic properties, on the other hand, are insensitive to the
termic cycle, and are therefore essentially the same in the weld
and in the base material. The material is described by $J_2$-flow
theory, and the analysis is performed by using a numerical
algorithm, in which the finite element mesh remains fixed relative
to the tip of the growing crack. Fracture is modelled using two
different local crack growth criteria. One is a crack opening
displacement criterion, while the other is a model in which a
cohesive zone is imposed in front of the crack tip along the
fracture zone. Both models predict that in general a thinner laser
weld gives higher interface strength. Furthermore, both fracture
criteria show, that the preferred path of the crack is close
outside the weld material; a phenomenon also observed in
experiments.

AB - The fracture strength under quasi-static steady-state crack growth
in an elastic-plastic material joined by a laser weld is analyzed.
Laser welding gives high mismatch between the yield stress within
the weld and the yield stress in the base material. This is due to
the fast termic cycle, which the material undergoes in welding.
The elastic properties, on the other hand, are insensitive to the
termic cycle, and are therefore essentially the same in the weld
and in the base material. The material is described by $J_2$-flow
theory, and the analysis is performed by using a numerical
algorithm, in which the finite element mesh remains fixed relative
to the tip of the growing crack. Fracture is modelled using two
different local crack growth criteria. One is a crack opening
displacement criterion, while the other is a model in which a
cohesive zone is imposed in front of the crack tip along the
fracture zone. Both models predict that in general a thinner laser
weld gives higher interface strength. Furthermore, both fracture
criteria show, that the preferred path of the crack is close
outside the weld material; a phenomenon also observed in
experiments.

M3 - Report

BT - Analysis of steady-state ductile crack growth

ER -