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通过一系列单轴应力循环实验对T2 2 5NG钛合金进行了长次循环棘轮行为研究。研究表明 ,在一定峰值应力范围内经数万次应力循环后材料具有棘轮安定性 ;棘轮疲劳损伤与幅值应力和峰值应力相关 ,当幅值应力为峰值应力的一半时 ,棘轮变形达到安定后产生疲劳破坏 ,疲劳寿命与峰值应力或SR应变 (饱和棘轮应变 )之间满足幂律关系 ;在幅值应力仅为峰值应力的 1%～2 5 %时 ,材料依然可以产生棘轮塑性应变累积并经过数十万次循环后达到安定 ,且蠕变附加效应不显著 ;当峰值应力取为屈服强度 85 %～ 10 0 %时 ,初始棘轮塑性应变率为零 ,但经过数万次循环后仍可以产生 1 4 %～ 2 5 %塑性应变累积。基于峰值应力与T2 2 5NG合金单轴棘轮塑性累积之间所具有的单调特性以及棘轮演化的门槛特性 ,本文重点发展了SRM抛物律本构模型 ,该模型可较好预测T2 2 5NG合金单轴SR应变 ,也可用于估算蠕变的安定塑性累积。论文还讨论了关于棘轮演化的分类问题
A series of uniaxial stress cycling experiments were carried out to study the long-term circulation ratcheting behavior of T2 2 5NG titanium alloy. The results show that the material has ratchet stability after tens of thousands of stress cycles within a certain peak stress range. The ratcheting fatigue damage is related to the amplitude stress and peak stress. When the amplitude stress is half of the peak stress, the deformation of the ratchet reaches stability Fatigue failure, fatigue life and peak stress or SR strain (saturated ratchet strain) satisfy the power law relationship; in the amplitude stress is only 1% ~ 25% of the peak stress, the material can still produce ratcheting plastic strain accumulation and after After hundreds of thousands of cycles to reach stability, and the additional effect of creep is insignificant; when the peak stress is taken as the yield strength 85% ~ 100%, the initial ratcheting plastic strain rate is zero, but after tens of thousands of cycles can still produce 1 4% ~ 25% plastic strain accumulation. Based on the monotonic characteristics between the peak stress and the plastic accumulation of uniaxial ratchet of T2 2 5NG alloy and the threshold characteristic of ratchet evolution, this paper focuses on the development of SRM parabolic constitutive model, which can predict the deformation of T2 2 5NG alloy uniaxially SR strain, can also be used to estimate the cumulative plastic creep strain. The paper also discusses the classification of ratchet evolution