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通过间歇疲劳试验和传统疲劳试验的对比,研究了无应力间歇时间对盐岩疲劳特性的影响。经过间歇疲劳试验的盐岩试样与传统疲劳试样差异巨大。表现出的不同点主要有:1在相同的应力加载条件下,盐岩的间歇疲劳寿命与传统疲劳寿命相比缩短了50%以上;2间歇疲劳试验中间歇后的每个循环不可逆变形更大,不可逆变形的累计速率更快;且随着间歇时间的增加,变形越大,累计速率越快;3卸载弹性模量总体上逐渐增大,间歇疲劳试验中,卸载弹性模量随间歇时间的变长而增大。间歇疲劳的机理是:在盐岩内部缺陷发育生长时,缺陷周围由于屈服的时空顺序差异引起了应力应变的不协调响应,导致了残余应力;在残余应力作用下,晶粒内部产生的位错做反向运动,且间歇时间越长,反向运动距离越大;再次加载时,由于包申格效应,导致位错滑移引发的塑性变形更大。
Through the comparison between the intermittent fatigue test and the traditional fatigue test, the effect of non-stress intermittent time on the fatigue property of salt rock was studied. After intermittent fatigue tests of salt rock samples and traditional fatigue specimens vary greatly. The main differences are as follows: 1 The intermittent fatigue life of salt rock is shortened by more than 50% compared with the traditional fatigue life under the same stress loading conditions.2 The irreversible deformation of each cycle after intermittent fatigue test is larger , The cumulative rate of irreversible deformation faster; and with the increase of intermittent time, the greater the deformation, the cumulative rate of faster; 3 unloading elastic modulus generally increased, intermittent fatigue test, unloading elastic modulus with the intermittent time Become longer and increase. The mechanism of intermittent fatigue is that when the internal defects grow and develop in the salt rock, the uncoordinated response of stress and strain due to the difference of the space-time order of the yield around the defect leads to the residual stress. Under the residual stress, the internal dislocations Do reverse movement, and the longer the interval time, the greater the reverse movement distance; when it is reloaded, the plastic deformation due to dislocation slip will be larger due to Bauschinger effect.