Citation:
Ngiam, Shi Song; Brennan, Feargal P.; Fatigue Crack Control in Structural Details Using Surface Peening, Journal of Ship Production, Volume 24, Number 3, August 2008 , pp147-151
Abstract:
This paper presents an analytical and experimental
study of crack shape evolution in steel plate specimens
under cyclic loading. It is widely known that the introduction
of compressive residual stresses by cold working
the surface can be highly beneficial in improving the
fatigue performance of structural components. Although
it is recognised that relaxation of surface compressive
residual stress can reduce the potential benefits,
the effects of residual stress on crack shape evolution
are often overlooked. Previous studies have shown that
the intensity of the surface compressive residual stress
has a pronounced effect on fatigue crack initiation. A
recently developed technique termed controlled stitch
cold working, which applies differing intensities of
compressive residual stress at specific regions in a structure,
is shown in the paper to influence fatigue crack
propagation life considerably. The approach can be
used to prevent crack growth in particular directions for
example encouraging a controlled or fail-safe scenario.
The paper describes fatigue crack growth tests on shot
peened specimens tested under uniaxial tension. The
specimens were peened to varying intensities and of
differing coverage areas. Cracks were initiated from
starter notches after peening meaning the approach can
be used for fatigue performance enhancement at the
construction stage or later as part of a maintenance and
repair strategy. Crack growth retardation is apparent in
all tests and this is attributed to the constrained crack
shape. Further work will consider the use of laser and
ultrasonic peening to contain cracks from rapidly
propagating from stress concentrations. This approach
used with careful design of stiffness can significantly
extend the fatigue crack