Ultrasonic impact peening was applied on welded joints manufactured from Strenx 700 MC high strength low alloy steel with the aim to improve the fatigue properties. Three different surface treatment parameters were tested, which resulted in transformation of the near-surface tensile residual stresses in the weld metal and heat affected zone to compressive residual stress field, while maximal values from −400 MPa up to −800 MPa were reached. The highest fatigue life improvement was reached by the double peening with the 85 N contact force, where the fatigue limit for N = 108 cycles increased from 370 MPa to 410 MPa.
This work deals with the fatigue resistance of welded joints manufactured from EN S355 J2 structural steel and the possibility of improving fatigue characteristics by the severe shot peening (SSP) surface treatment. Fatigue testing was carried out by the rotating bending test on specimens manufactured from the base material (BM), welded material and welded material treated by SSP. Results have shown big scatter in obtained results from as-welded material and overall reduction of fatigue endurance when compared to the BM. SSP applied on the welded joints has reduced the scatter of experimental data and increased the fatigue strength. Obtained results of fatigue tests are compared, discussed and supported by correlation with results of additional experiments, e.g. metallographic analyses, microhardness tests, residual stresses measurements and surface roughness measurement.
This work deals with fatigue testing of the EN S355 structural steel welded joint. The weld was manufactured by the MIG welding technology and as the filler material was used the G3Si1 wire. The fatigue tests were carried out in the rotating bending mode on the specimens manufactured from the welded joint of the S355 steel. The main aim was to evaluate the fatigue endurance of the weld material and for this reason were used machined axis symmetrical specimens to remove the notch effect of the weld shape. In order to increase the fatigue endurance of the weld, the Nd-YAG laser was used for laser shock peening (LSP) of specimens surfaces, which lead to removing of the weld defects but in overall caused that LSP has behaved as the notch and lead to decreasing of the fatigue endurance. Obtained results of fatigue tests are compared, discussed and supported by correlation with results of additional experiments, e.g. identification of incurred structures after the laser shock peening by the metallographic observations and micro-hardness tests.
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