Abstract
Summary This paper describes an investigation of improvement of the fatigue strength of non-load-carrying cruciform fillet welded joints through the kinetic energy of an abrasive water jet being applied to the weld toe region at a nozzle travel speed of 30 cm/min. An FEM analysis, measurements of the residual stress and hardness in the toe region, and 0-tension fatigue tests of the fillet welds were performed to analyse fatigue strength improvement. Fatigue failures invariably occurred in the toe region. The results obtained may be summarised as follows: 1. Suitable water jet treatment makes the fatigue limit of the water jet treated joints (W07538, W05010, W10038-3, W07538-3, W10038, W07525 series) some 1.6–2.0 times (180–224 M Pa) better than that of corresponding as-welded joints to give an improvement effect next behind TIG dressing and hammer peening. 2. This fatigue strength improvement is attributable to a decrease in the tensile residual stress, a hardness increase, and a decrease in the stress concentration factor in the toe region depending on the water jet treatment conditions. 3. The single-pass W07538 and W05010 joints have the highest fatigue limit (around twice that of the as-welded joints). The stress concentration factor in the toe region being higher than that of the as-welded joints, however, suggests that the kinetic energy of the water jet was in these cases set too high. The overall improvement of the fatigue limit is due to the fact that water jet treatment increases the hardness and exerts a compressive residual stress effect on the joints. 4. The triple-pass W07538-3 and W10038-3 joints have a fatigue limit around 1.8 times that of the as-welded joints. This is due to the fact that the values of the maximum stress concentration factor Ktmax and maximum hardness HVmax produce more stable fatigue strength improvement conditions. The fatigue strength can also be expected to be improved by the hardness increase and compressive residual stress effect through a maximum three passes being concentrated in the toe region.
Published Version
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