Inverted S-shaped model for nonlinear fatigue damage of rock
Inverted S-shaped model for nonlinear fatigue damage of rock
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DOI：
10.1016/j.ijrmms.2008.11.002
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发表时间：
2009-04
影响因子：
7.2
通讯作者：
J. Xiao;D. Ding;Gen-ying Xu;F. Jiang
中科院分区：
文献类型：
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作者：
J. Xiao;D. Ding;Gen-ying Xu;F. Jiang
疲劳是导致工程结构和机械失效的主要原因。实验表明，岩石作为一种内部结构复杂的天然材料，在常规的静、动态试验中，其试验数据具有较大的离散性。许多已被证明有效并广泛用于金属的理论不能应用于岩石。例如，疲劳损伤累积理论是疲劳寿命分析的基础。众所周知，采用Miner线性疲劳损伤累积理论估算变幅载荷作用下岩石的疲劳寿命时，SJN曲线是必不可少的。然而，已有文献[1]推导出疲劳寿命N依赖于应力水平S，由于静强度的分散性，用Miner准则预测的疲劳寿命与实际值相差甚远。事实上，Miner线性疲劳累积损伤理论虽然在工程上得到了广泛的应用，但由于其简单、直观、清晰的优点，特别是在两级或多级载荷作用下，由于没有考虑载荷序列效应和载荷交互作用效应，其计算精度有限。为了克服这一缺陷，在过去的几十年里，提出了许多修正的线性疲劳累积损伤理论和非线性疲劳累积损伤理论[2]。其中大多数是为了解决金属材料的某些问题而提出的，不能直接应用于岩石。因此，在进行岩体疲劳分析之前，必须解决两个关键问题。一是合理定义岩石损伤，二是建立岩石疲劳损伤累积模型，研究人员[3-12]对岩石的疲劳破坏和变形进行了大量的研究。从实验获得的结果表明，尽管常规的机械参数如疲劳寿命、疲劳强度等，对于某一岩石，轴向极限变形较为分散，几乎保持不变。因此，在应变空间中可以建立一个适用于岩石的通用疲劳破坏准则。而本研究更侧重于岩石疲劳损伤累积模型的建立。
Fatigue is a primary reason contributing to the failure of engineering structures and machines. Experiments show that rock, as a kind of natural material with a complex internal structure, exhibits a wide dispersion of experimental data in conventional static and dynamic tests. Many theories that have proved efficacious and are used widely for metals cannot be applied to rocks. For example, the fatigue damage cumulative theory is the foundation of fatigue life analysis. And, it is well known that the SJN curve is necessary to estimate the fatigue life of rock subjected to variable amplitude loading by using Miner’s linear fatigue damage cumulative theory. However, it has been deduced [1] that fatigue life N is dependent on the stress level S, and the fatigue life predicted by Miner’s rule is far from the actual value, because of the scatter of static strength. In fact, despite the fact that the Miner’s linear fatigue damage cumulative theory is used comprehensively in engineering, due to its advantage of being simple, visual and distinct, it is limited by finite calculation accuracy, especially under two-level or multilevel loadings, and for not taking loading sequence effect and loads interaction effect into account. To overcome this defect, many modified linear fatigue damage cumulative theories and nonlinear ones [2] have been proposed in the past several decades. Most of them are brought forward to solve some problems of metal materials and cannot be applied to rock directly. Therefore, two key problems must be addressed before undergoing fatigue analysis in rock mass. The first one is reasonable definition of rock damage, and the other is construction of fatigue damage cumulative model for rock.Researchers [3–12] have devoted great efforts to study the fatigue failure and deformation of rock. Results obtained from experiments indicate that in spite of conventional mechanical parameters such as fatigue life, fatigue strength, etc., being more scattered, the axial ultimate deformation stays almost constant for a certain rock. So, a universal fatigue failure criterion can be established appropriately for rocks in strain space. However, this study lays more emphasis on the construction of fatigue damage cumulative model for rock.