单面激光冲击孔壁残余应力与疲劳失效

Residual stress and fatigue failure in hole specimen by one side laser shock processing

孔结构往往会造成零件上的应力集中,降低零件的疲劳寿命,激光冲击强化能够有效地缓解这一问题。在试验研究中发现采用高峰值压力对试件进行激光冲击强化后,试件的疲劳寿命反而降低,同时断口上的疲劳源也随之发生内移,这很可能是因为高峰值压力在孔壁内产生较大的残余拉应力而降低了小孔件的疲劳寿命。为此采用ABAQUS软件,针对不同峰值压力、载荷脉宽对7050-T7451小孔件孔壁上应力分布的影响进行研究。研究结果表明:峰值压力的提高在增大压应力层深度的同时也会增大带孔件孔壁上的拉应力,同时残余拉应力所在位置也随之发生内移;当峰值压力不同时,载荷脉宽对孔壁上应力分布的影响也会随之改变。

Pore structure tends to cause the stress concentration on the parts and reduce the fatigue life of the parts,but laser shock processing（ LSP） can be used to remit residual stress in the material surface. In experimental studies,when peak pressure is too high,the fatigue life of the parts will decrease after laser shock processing for the parts,which maybe cause the result of tensile stress introduced by large energy laser shock processing. ABAQUS is used to analysis the residual stress field of 7050- T7451 aluminum alloy with different peak pressure and pulse width of laser. Results show that the peak pressure is closely relative with the residual stress field. The tensile stress will increase with the increase of peak pressure. Different peak pressures will change the connection between pulse width and tensile stress. That may be the reason why the fatigue life decreases when large energy laser is used to impact the specimen and the fatigue source at the center of the hole.