(天津大学 材料科学与工程学院，天津 300072)
摘 要: 利用自行研制的超声冲击实验装置，对提高LF21铝合金焊接接头的疲劳强度进行了研究，进行了TIG焊LF21铝合金非承载十字与T型接头的焊态及冲击处理态对比疲劳试验。结果表明：使用TIG焊获得的LF21铝合金原始焊接接头的疲劳强度与其它焊接方法得到的同样接头的疲劳强度基本相当，试图采用更高强度级别的S-N曲线对其进行设计时应持慎重态度。在应力比 R=0.5时，超声冲击处理使LF21铝合金非承载十字焊接接头(拉伸载荷)的疲劳强度提高了26%，接头寿命延长了2～4倍。在应力比 R=0.1时，超声冲击处理使T型接头(三点弯曲载荷)的疲劳强度提高了37%，接头寿命延长了4～8倍。在应力比 R=-1时，超声冲击处理使T型接头(三点弯曲载荷)疲劳强度提高了44%，接头寿命延长了5～10倍。
关键字: 铝合金； 疲劳强度； 焊接接头； 超声冲击
LF21 aluminum alloy by ultrasonic peening method
（College of Materials Science and Engineering，
Tianjin University， Tianjin 300072， P.R.China）
Abstract:The ultrasonic peening method was used to improve the fatigue strength of welded joints of aluminum. The S-N curves and fatigue limits ofTIG cruciform and T-shape joints of LF21 aluminum were obtained at both as weldedand peening conditions. The results show that it should be more careful to design according to high strength classic S-N curves， for the tests reveal little difference of the fatigue strength between TIG and other welding methods as in the same form of welded joints. The fatigue strength of cruciform joints of LF21 by ultrasonic peening treatment have been increased by 26% (tension) under the stress ratio R =0.5 and the fatigue life is 2～4 times longer than that of the aswelded ones. When the stress ratio R =0.1， the fatigue strength of T-shape joints havebeen improved by 37% and fatigue life is 4～8 times longer. When R =-1， thefatigue strength of T-shape joints have improved by 44% and fatigue life is5～8 times longer.
Key words: aluminum alloy; fatigue strength; welded joints; ultrasonic peening
