为了研究平均应变对7050-T7451铝合金低周疲劳力学行为的影响,开展了不同应变比(R=-1、-0.06、0.06和0.5)下的室温恒幅低周疲劳试验.结果表明:在对称循环应变下,材料总体表现为循环软化特征；而在非对称循环应变下,材料表现为初始硬化后的循环稳定行为.非对称循环应变导致了材料出现与应变幅相关的平均应力松弛现象.采用Landgraf模型和非线性Maxwell模型分别研究了7050-T7451铝合金的平均应力松弛规律.结果表明:Maxwell模型能够较准确地描述材料的平均应力循环松弛特征,而Landgraf模型更适用于低应变幅下的平均应力松弛描述.%In order to investigate the effect of the mean strain on low-cycle fatigue behavior of 7050-T7451 aluminum alloy,a series of uniaxial low-cycle fatigue tests with different strain ratios (R=-1,-0.06,0.06 and 0.5) were performed at room temperature in an ambient air.Under symmetric cyclic straining,the alloy exhibits cyclic softening characteristics,as a whole,while under asymmetric cyclic straining,the material presents initial hardening followed by cyclic stabilization.It is shown that the asymmetric cyclic straining causes the relaxation of the mean stress dependent on the applied strain amplitudes,which was further described by using Landgraf model and non-linear Maxwell model.It is pointed out that the relaxation behavior of the mean stress during asymmetric cyclic straining of the alloy can be well described by nonlinear Maxwell model at all strain amplitudes investigated,while it can only be described accurately at relatively lower strain amplitudes by Landgraf model.
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