A Mechanism-Based Approach From Low Cycle Fatigue to Thermomechanical Fatigue Life Prediction
A Mechanism-Based Approach From Low Cycle Fatigue to Thermomechanical Fatigue Life Prediction
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DOI：
10.1115/1.4031908
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发表时间：
2015-06
影响因子：
1.5
通讯作者：
Xijia Wu;Zhong-ping Zhang
中科院分区：
文献类型：
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作者：
Xijia Wu;Zhong-ping Zhang
变形和损伤积累是通过基本的位错和扩散机制发生的。基于物理应变分解规律，认识到每种变形机制的作用，从而将损伤累积与其潜在的物理机制联系起来，建立了蠕变-疲劳综合理论(S)。ICFT将整体损伤累积描述为一个整体损伤过程，该过程由表面/次表面裂纹在内部分布的损伤/不连续性的结合中成核和扩展组成。这些指导原则贯穿于一般条件下的等温低周疲劳(LCF)和热机械疲劳(TMF)。本文提出了一种基于机理的本构方程来描述循环应力-应变曲线和非线性损伤累积方程的方法，其中包含(I)率无关塑性疲劳、(II)晶间脆性(IE)、(III)蠕变和(IV)氧化的非线性损伤累积方程来预测球墨铸铁(DCI)的低周疲劳寿命和TMF寿命。该材料中复杂的机理及其相互作用为该模型提供了一个很好的示范案例，该模型与实验观测结果符合得很好。
Deformation and damage accumulation occur by fundamental dislocation and diffusion mechanisms. An integrated creep–fatigue theory (ICFT) has been developed, based on the physical strain decomposition rule that recognizes the role of each deformation mechanism, and thus relate damage accumulation to its underlying physical mechanism(s). The ICFT formulates the overall damage accumulation as a holistic damage process consisting of nucleation and propagation of surface/subsurface cracks in coalescence with internally distributed damage/discontinuities. These guiding principles run through both isothermal low cycle fatigue (LCF) and thermomechanical fatigue (TMF) under general conditions. This paper presents a methodology using mechanism-based constitutive equations to describe the cyclic stress–strain curve and the nonlinear damage accumulation equation incorporating (i) rate-independent plasticity-induced fatigue, (ii) intergranular embrittlement (IE), (iii) creep, and (iv) oxidation to predict LCF and TMF lives of ductile cast iron (DCI). The complication of the mechanisms and their interactions in this material provide a good demonstration case for the model, which is in good agreement with the experimental observations.