A Damage Model for Fatigue-creep Interaction Based on Entropy Increase Theory and Its Experimental Verification

Abstract

Abstract: According to the classical theory of thermodynamics, the fatigue-creep interaction damage of the material might be regarded as the accumulation of the entropy increase. When this accumulation reached to the critical point, the failure occured. From this theory, using the change of the entropy increase to describe the material damage, a damage model for fatigue-creep interaction was developed herein based on CDM and the law of energy conservation. To verify this damage model, the fatigue-creep interaction tests of 1.25Cr0.5Mo steel were conducted with the trapezoidal wave loading under stress control at 540℃ and 520℃. According to the tests, the change of the residual strain, which might reflect the accumulation of the entropy increase of the material, was defined as the damage variable. With this definition, the damage curves of different loading conditions were obtained by the above fatigue-creep interaction damage model. Results show that the damage values measured from experiments are in good agreement with these damage curves, which means that the damage model presented herein may describe the fatigue-creep interaction damage evolution well.

Key words: fatigue-creep, entropy increase, continuum damage mechanics(CDM), damage variable, residual strain

摘要： 根据经典热力学理论，材料疲劳-蠕变交互作用下的损伤过程可视为系统熵增的累积，当熵增积累到临界值时，材料发生失效断裂。按此理论，并基于连续损伤力学和能量守恒定律，以系统熵增的变化来描述材料损伤，建立了一种疲劳-蠕变交互作用的损伤模型。为验证该模型，进行了540℃和520℃环境下1.25Cr-0.5Mo钢应力控制的梯形波加载试验，以材料的残余应变反映熵增积累，选取残余应变的变化作为损伤变量，用上述损伤模型进行了材料疲劳-蠕变交互作用的损伤演化描述，结果表明实测损伤点数据与该模型的损伤演化规律符合较好。

关键词: 疲劳-蠕变, 熵增, 连续损伤力学, 损伤变量, 残余应变

CLC Number:

O346.5，TG115.5

Chen Ling, , Zhang Xianming, Liu Fei, Ouyang Ping, Liu Xianbin. A Damage Model for Fatigue-creep Interaction Based on Entropy Increase Theory and Its Experimental Verification[J]. China Mechanical Engineering.

陈凌, 张贤明, 刘飞, 欧阳平, 刘先斌. 一种基于熵增理论的疲劳-蠕变交互作用损伤模型及试验验证[J]. 中国机械工程.

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