Crack Orientation and Residual Stress on Stress Intensity Factors of
Welded Steel Joints
Abstract
Assessing the structural integrity of a cracked weldment is significant
in engineering. When cracks are detected during welding inspection, they
must fit the mechanical resistance of the structure. Generally, fracture
mechanics supplies the essential tools to examine cracked structures in
order to determine a fracture criterion for loading conditions. This
study explores the effect of residual stress (RS) and crack orientation
on determining the stress intensity factor (K_I) in mode I for a welded
joint using the extended finite element method (XFEM). This research
consists of two parts. The first part is a 3D thermo-mechanical finite
element (FE) analysis that is established to study the temperature
history and the residual stress distribution of a welded joint. The
second part is a 3D FE crack model that establishes two cases of cracks,
longitudinal and transverse cracks, in order to calculate K_I and
J-integral values at the middle surface of a thin butt joint. K_I is
calculated for cracks under applied external stress and residual stress.
The results demonstrate that the effect of the welding residual stress
on K_I is either beneficial or detrimental, depending on the stress
distribution and sign. Moreover, the results indicate the significance
of RS and crack orientation on K_I. From the simulation performed
during the analysis, we show that the longitudinal crack in case (I) has
higher K_I values than those in case (II) for the transverse crack.
Finally, the finite element results are in good agreement with the
analytical results.