ssc-367 - Ship Structure Committee

improve the fatigue strength. The methods available to improve
fatigue strength can be-grouped into two:
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Modification of weld toe profile
Modification of residual stress distribution
Some of the methods in each category are identified on Figure 9-1
and discussed in this section.
Modification of Weld Profile
Both contour grinding of the weld profile and the local grinding of
the weld toe area are recommendedto improve fatigue strength. The
two key objectives in the modification of weld toe profile are:
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Remove defects at the weld toe.
Develop a smooth transition between weld material and parent
plate.
By applying either local grinding or remelting techniques to remove
defects and discontinuities, the fatigue life is increased as a
function of time required for crack initiation. Some applicable
methods are as follows:
● ✍
Grindinq
Full-profile burr grinding, toe burr grinding or localized
disc grinding can be carried out. Considering the time
required for grinding, local-weldtoe grinding has become one
of the most frequently used grinding methods. Careful and
controlledlocal grindingof the weld toe improvesthe fatigue
strength of a specimen in air by at least 30%, equivalent to
an increase in fatigue life by a factor greater than 2.
However, to obtain such a benefit the grinding must extend
about 0.04 inch (1 nun)beneath the plate surface. Typical
defects and correctivemeasures are shown on Figure 9-2.
9-9