Safe structural design for fatigue and creep using cyclic yield strength
Safe structural design for fatigue and creep using cyclic yield strength
复制标题
使用循环屈服强度进行疲劳和蠕变的安全结构设计
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
D. Mackenzie
中科院分区：
文献类型：
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作者：
Y. Gorash;D. Mackenzie
本研究提出循环屈服强度（CYS，σ_cy）作为疲劳和蠕变条件下运行的结构的安全设计的潜在特征。CYS定义在循环应力-应变曲线（SSC）上，而单调屈服强度（MYS，σ_my）定义在单调SSC上。采用Ramberg-Osgood和Chaboche材料模型对实验SSC进行两步拟合，确定了σ_cy和σ_my的值。应力-寿命法疲劳分析中典型的S-N曲线有一个独特的最小应力下限，即疲劳极限（FEL，σ f-lim）。σ_cy和σ_f-lim的比较表明它们近似相等。因此，在由σ_cy定义的纯弹性域中保证了安全的疲劳设计。蠕变失效时间法中的长期强度（LTS）曲线有两个拐点，分别对应于σ cy和σ my。这些拐点在LTS曲线上分为3个部分，其特征在于不同的蠕变断裂模式和蠕变变形机制。因此，在σ_cy定义的脆性破坏模式的线性蠕变域中，保证了安全蠕变设计。使用3种用于正常和高温应用的结构钢证实了这些假设。使用σ_cy表征疲劳和蠕变强度的优点是相对快速的实验识别。循环SSC识别的循环试验的总持续时间远小于在σ_cy附近的应力水平下的疲劳和蠕变断裂试验的典型持续时间。
This study proposes cyclic yield strength (CYS, σ_cy) as a potential characteristic of safe design for structures operating under fatigue and creep conditions. CYS is defined on a cyclic stress-strain curve (SSC), while monotonic yield strength (MYS, σ_my) is defined on a monotonic SSC. Both values of σ_cy and σ_my are identified using a 2-step fitting procedure of the experimental SSCs using Ramberg-Osgood and Chaboche material models. A typical S-N curve in stress-life approach for fatigue analysis has a distinctive minimum stress lower bound, the fatigue endurance limit (FEL, σ_f-lim). Comparison of σ_cy and σ_f-lim reveals that they are approximately equal. Thus, safe fatigue design is guaranteed in the purely elastic domain defined by the σ_cy. A typical long-term strength (LTS) curve in time-to-failure approach for creep analysis has 2 inflections corresponding to the σ_cy and σ_my. These inflections separate 3 sections on a LTS curve, which are characterised by different creep fracture modes and creep deformation mechanisms. Thus, safe creep design is guaranteed in the linear creep domain with brittle failure mode defined by the σ_cy. These assumptions are confirmed using 3 structural steels for normal and high-temperature applications. The advantage of using σ_cy for characterisation of fatigue and creep strength is a relatively quick experimental identification. The total duration of cyclic tests for a cyclic SSC identification is much less than the typical durations of fatigue and creep rupture tests at the stress levels around the σ_cy.