残余应力对高速列车A7N01铝合金焊接接头疲劳行为的影响

Effect of residual stress on fatigue behavior of welded joint of A7N01 aluminum alloy for high-speed trcion

研究了残余应力在疲劳加载过程中的应力松弛行为,采用预拉伸、表面喷丸等表面预制残余应力的方法预制了表面残余应力,并研究了焊接接头的疲劳性能.结果表明,在经过1×105周次循环载荷后,各个部位残余应力发生较大松弛,在经过2×105周次后,应力松弛较1×105周次时松弛幅度降低.在2×105周次后,应力松弛不再明显,最终残余应力分布在拉应力20～40 MPa之间.当引入残余应力后,各种条件下的实际应力循环比发生了明显的变化,当应力比R≥0时,随着R的增大,平均应力增大,试样的疲劳周次显著下降.残余压应力会使裂纹萌生的周期缩短,同时加快疲劳裂纹扩展速率.

Residual stress relaxation behaviors of A7N01 aluminum alloy structures of underframes were investigated. The A7N01 aluminum alloy welded joints was treated by pre tension treatment and surface shot peening technology for obtaining the preset residual stress. Then the fatigue behaviors of different welded joints were investigated. The results showed that the residual stress had undergone larger relaxation after 1 × 105 cyclic loading. The residual stress relaxation extent had undergone gently after 2 × 105 cyclic loading and finally became to stable with the value at 20 ~ 40 MPa. The real cyclic stress ratio was changed different preset residual stress treatment. When R ≥0,the fatigue cycles decreased with the increase of stress ration. The residual stress decreased the origin period of cracks and changed the propagation velocity of cracks.