The Paton Welding Journal, 2014, #11, 42-45 pages
EFFECTIVENESS OF STRENGTHENING BUTT WELDED JOINTS AFTER LONG-TERM SERVICE BY HIGH-FREQUENCY MECHANICAL PEENING
V.V. KNYSH, S.A. SOLOVEJ and A.Z. KUZMENKO
E.O. Paton Electric Welding Institute, NASU. 11 Bozhenko Str., 03680, Kiev, Ukraine. E-mail: email@example.com
Cyclic fatigue life of butt welded joints of low-alloyed steel 09G2S, strengthened by the technology of high-frequency mechanical peening (HFMP) at different stages of fatigue fracture: in as-welded state, after accumulation of 70 % of fatigue damage, at formation of surface fatigue cracks, was studied. The objective of these studies is establishing the effectiveness of application of HFMP treatment of butt welded joints after long-term service at alternating loading. It is shown that strengthening of butt welded joints by HFMP right after welding increases the endurance limit (2 mln cycle base) by 50 % - from 180 up to 270MPa, and cyclic fatigue life - by 5 to 10 times. It is experimentally confirmed that the effectiveness of strengthening welded joints with 70 % accumulated fatigue damage depends on the levels of applied maximum stresses before strengthening. So, residual cyclic fatigue life of samples, tested in the range of maximum 240-260 MPa stresses, falls within the scatter band of experimental data for welded joints in unstrengthened condition, and for those tested in the range of maximum stresses of 280-300MPa it is within the scatter band of experimental data for welded joints strengthened by HFMP technology in as-welded condition. It is established that application of HFMP technology improves the residual cyclic fatigue life of welded joints with surface fatigue cracks (down to 2 mm deep) 2.5 times compared to fatigue life before crack formation. 11 Ref., 5 Figures.
high-frequency mechanical peening, increase of cyclic fatigue life, fatigue, welded joint, accumulated fatigue damage
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