Abstract: Under the loading condition of high stress ratio R=0.5, contrast fatigue tests of tubular T-joints are carried out. Specimens are divided into three groups: as welded, treated by loading ultrasonic peening and unloading ultrasonic peening. Testing results show that: ① Under the loading condition of high stress ratio R＝0.5, the fatigue performance of tubular joints can still be significantly improved by ultrasonic peening when after static loading. ② After treated by loading ultrasonic peening, the fatigue strength (stress ratio R=0.5) of 20 steel tubular T-joints is increased by 66%, and the fatigue life is prolonged by 3.8~4.0 times. ③ The fatigue performance of welded tubular joints can be improved by loading ultrasonic peening not only in low stress, medium-long life range, but also in high stress range. The problem that fatigue performance of welded joints in high stress range declines significantly by loading ultrasonic peening, can be solved by this technique to some extent.

Key words: Fatigue performance, Loading ultrasonic peening, Low carbon steel, Tubular joint