7075铝合金残余应力松弛影响因素的实验研究

Experimental study of influencing factors on residual stress relaxation of 7075 aluminum alloy

分别采用淬火和退火态喷砂两种强化工艺引入结构和表层集中残余应力,研究了在循环应力下具有不同残余应力状态的7075铝合金表层残余应力松弛现象,并基于应力松弛机理讨论了两种不同强化工艺下残余应力松弛规律的异同.分析结果表明,加载应力的状态与大小、残余应力的初始分布和冷作是影响两种强化工艺下残余应力松弛异同的主要因素.淬火强化引入的是梯度较小、非均匀分布的结构残余应力,而喷砂强化引入的是梯度大、均匀分布的表层残余应力.由于应力分布梯度与表层冷作程度的不同,在相同的加载条件下,喷砂样较淬火样有更大的应力松弛趋势.

Structural residual stress and surface residual stress were introduced by two strengthening processes-- quenching and shot peening on 7075 aluminum alloy to analyze the residual stress relaxation under cyclic loading with different initial residual stress states. The similarities and differences of residual stress relaxation under the two different strengthening processes were discussed based on stress relaxation mechanism. The results showed that state and magnitude of the applied stress, initial distribution of the residual stress and cold working had great influence on the stress relaxation. Structural residual stress introduced by quenching relaxed a little under cyclic loading while the stress induced by shot peening relaxed a lot on the same cyclic stress scale because of different stress gradient and cold working. Great stress relaxation occured in the uniform surface residual stress introduced by shot-peening with a great stress gradient, while stress re-distribution occured in the non-uniform structural stress introduced by quenching with a relatively lower stress gradient.