【作者】 崔瑞乾；

【导师】 戴振羽；

【作者基本信息】 西南交通大学 ， 固体力学， 2011， 硕士

【摘要】 在工业生产中,许多机械和设备的构件都是在高温条件下工作的,这些构件往往既承受着高温蠕变作用,同时还承受着循环荷载作用,这两种作用不只单独对材料构成损伤,其交互作用也会对材料的寿命产生影响。而这些构件一旦破坏,会造成重大的财产损失和人员伤亡,其安全性特别需要人们重视。因此,对该类材料在高温循环蠕变作用下寿命估算方法的研究具有重要的意义。本文通过对P91钢循环蠕变试验结果的分析研究以及对不同材料循环蠕变破坏断口的微观观察,从宏微观两个角度揭示了该损伤演化过程,即循环蠕变材料承受着蠕变损伤、疲劳损伤及其交互作用损伤的共同作用。根据材料循环蠕变的微观变化机理,在线性累积损伤法的基础上,提出新的“损伤”概念,弥补了应用现行“损伤”概念求解循环蠕变问题时边界条件与工程实际不相符合的缺陷,实现了三种损伤作用的叠加；利用“应变回复理论”和“金相学理论”对材料交互损伤的微观解释,定义了交互损伤项,赋予了交互损伤项新的内涵及求解方法,提出了一种循环蠕变寿命估算模型：发挥了灰色数学理论在处理“行为信息不完全、运行机制不清楚这类系统”的优越性,将其应用到寿命预测当中,在循环蠕变作用机制复杂且试验数据较少的情况下,保证了模型预测的精度。应用该模型估算了P91钢、12CrlMoV钢及316L不锈钢在循环蠕变作用下的寿命,并与试验值及其他模型的计算值进行了对比,结果显示应用本方法预测不同保载时间下构件的循环蠕变寿命精度较高,模型形式简单、计算所需参数较少、便于工程应用。更多还原

【Abstract】 In industry, many of the engineering components are working at high temperature conditions, which suffered both high temperature creep and the cyclic loading, and both of two factors will affect the lifetime of the engineering components. It should be noted that the two mechanisms do not damage on the material individually, the interaction of two mechanisms should be taken into account in the calculation of damage and life-estimation. As we know, once these components sudden breaks or failure, it will cause severe property loss and casualties. Therefore, the study of the life-estimation of those materials which suffered cyclic loading at high temperature is urgently conducted.Through analysis of P91 steel cyclic creep test results and the microscopic observation of the fracture of several kinds of materials, the evolution of damage is revealed in this paper, that is the material suffers creep damage、fatigue damage and interaction damage under cyclic loading at high temperature. According to the micro mechanism and the linear cumulative damage law, a new "damage" concept is proposed, which replenish the defect of boundary conditions inconsistent with engineering when applying the existing "damage" concept solving the cyclic creep problem, superposition of the three damage mechanisms is constructed by this model. Taking advantage of "Strain Recovery Theory" and "Metallography Theory" microscopic explanation for interaction damage, the interaction damage items is defined, a cyclic creep life prediction model is proposed:It was used to life prediction that Gray mathematical theory’s superiority in dealing with systems which has incomplete information and unclear operating mechanism, achieving fully guaranteed of model prediction accuracy in the case of complex cyclic creep mechanism and less test data.The lifetime of the P91 steel,12Cr1MoV steel and 316L stainless steel were calculated by this model, and then the results were compared with the experimental results, also the calculated results were also compared with some other models proposed by other researchers. The comparison shows that this model has high accuracy in predicting cyclic creep life under different loading conditions (i.e. different amplitude holding time). Meanwhile, this model is simple in form, and requires less parameter than other models in simulation. On the whole, the lifetime of material under cyclic creep at high temperature can be precisely calculated by this model; also this model is convenient for the engineering application.更多还原