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Abstract: The fatigue strengths of welded joints in welded structures
are much lower than those of the base metal because there are stress
concentrations and tensile residual stresses at weld toes. Ultrasonic
peening (UP) treatment and the use of low transformation temperature
electrodes (LTTE) are new developed methods for improving the fatigue
strengths of welded joints. The fatigue tests of two methods are carried
out on both transverse butt welded joints and longitudinal fillet welded
joints. The fatigue strengths at 2×106 cycles of the two kinds of welded
joints treated by ultrasonic peening are respectively improved by 50%
and 71% compared with those of the as-welded condition. The fatigue
strengths at 2×106 cycles of the two kinds of welded joints welded with
low transformation temperature electrodes are respectively improved by
11% and 41% compared with those of E5015. In addition, their fatigue
lives are also increased by from several times to hundred times at
different stresses. The test results show that the UP and LTTE are
effective methods to improve the fatigue strengths of welded joints. It
is suggested that UP is used to improve the fatigue performance of
transverse butt welded joints, but it is thought that the LTTE may be
particularly suitable for longitudinal welded joints containing high
tensile residual stresses since it is not necessary to add another
process after welding.
Key words: Low transformation temperature electrode Ultrasonic
peening Welded joints Fatigue strengths
CLC No: TG404
国家自然科学基金资助项目(50175079, 59575061). Received
20020112, received in revised form 20020520
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