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首页> 外文会议>International conference on the importance of understanding the fundamentals of the fatigue process in counteracting its effects in engineering components and structures >Microstructural effects on fracture mechanisms and fatigue life in extremely low cycle fatigue
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Microstructural effects on fracture mechanisms and fatigue life in extremely low cycle fatigue

机译：极低循环疲劳中骨折机制和疲劳寿命的微观结构效应

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This paper is divided into two main parts. In the first part, microstructural effects on fatigue fracture behavior in the Extremely Low Cycle Fatigue (ELCF) regime are investigated using various kinds of materials having different microstructures. In the case of steel with a duplex microstructure such as annealed low carbon steel and ferritic ductile cast iron, two types of fracture mode are observed depending on the level of the plastic strain range △εp. In the conventional low cycle fatigue regime, a crack originating from the surface leads to final fracture of the specimen (surface fracture mode). In the ELCF regime, however, final fracture of the specimen is controlled by the coalescence of microvoids inside the material (internal fracture mode). A method to detect the internally accumulated fatigue damage in ELCF has also been proposed. Secondly, the applicability of Manson-Coffin law to ELCF is discussed in relation to the transition between fracture modes. In materials which exhibit the transition, the fatigue life curve is composed of two straight lines (Manson-Coffin type) with different slopes which correspond to the surface and the internal fracture modes, respectively. A new concept of 'Fatigue Life as Determined by Competition of Two Failure Limit Lines' is proposed to explain this characteristic of fatigue life in the ELCF regime. The effect of repeated annealing on fatigue life in the ELCF regime is also discussed to prove this concept.
机译：本文分为两个主要零件。在第一部分中，使用具有不同微结构的各种材料研究了极低循环疲劳（ELCF）制度中疲劳裂缝行为的微观结构效应。在具有双工微结构的钢的情况下，例如退火的低碳钢和铁素体延性铸铁，根据塑料应变范围的水平观察两种类型的裂缝模式。在传统的低循环疲劳方案中，源自表面的裂缝导致样品（表面骨折模式）的最终断裂。然而，在ELCF制度中，标本的最终断裂由材料内部的微毒性的聚结（内部骨折模式）控制。还提出了一种检测ELCF内累积疲劳损伤的方法。其次，与骨折模式之间的过渡有关迈森 - 棺材对ELCF的适用性。在表现出过渡的材料中，疲劳寿命曲线分别由两条直线（Manson-Coffin型）构成，其具有与表面和内部裂缝模式对应的不同斜率。提出了一种新的疲劳生活概念，由两条失败限制线的竞争决定'解释了ELCF制度疲劳生活的特征。还讨论了反复退火对ELCF制度疲劳寿命的影响，以证明这一概念。

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