考虑高温蠕变损伤的含体积型缺陷承压结构的塑性承载能力分析

发布时间：2018-11-26 07:16

【摘要】：在电力、石化、核能及航空航天等工业领域中,广泛采用高温工艺。在高温下长期服役的结构部件中,不可避免地产生蠕变损伤。加之在制造和服役过程中常常产生夹渣、凹坑、减薄等体积型缺陷,削弱了结构的极限承载力。传统的安全评定规范不考虑结构中蠕变损伤的累积对结构极限承载力的影响,可能导致不合理的评定结果。本文针对这一问题,考虑蠕变损伤对极限载荷的影响,基于“合乎使用”的原则,通过理论计算与数值模拟相结合的方法,构建了耦合材料蠕变损伤的弹塑性本构模型,系统地研究了含体积型缺陷高温结构的极限载荷,提出了考虑结构中蠕变损伤累积的安全评定方法。论文的主要研究工作及结论如下： (1)基于幂律强化材料本构模型,推导了无缺陷厚壁及薄壁圆筒的内压极限载荷的解析解。用有限元计算了结构尺寸及材料参数对无缺陷圆筒的内压极限载荷的影响规律,并验证了解析解。 (2)通过实验观察,分析了2.25Cr1Mo钢蠕变损伤的物理机制和影响因素,并将这些因素耦合到弹塑性本构方程中；构建了基于Ramberg-Osgood方程的耦合蠕变损伤的弹塑性本构模型,可以预测含蠕变损伤的高温结构的弹塑性响应,为计算含蠕变损伤高温结构的极限载荷奠定基础。 (3)基于该弹塑性本构模型,运用有限元计算分析了各种形状尺寸的凹坑及局部减薄缺陷的圆筒形容器在内压或弯矩的作用下,塑性区域的扩展过程和失效模式。着重分析了缺陷尺寸和蠕变损伤累积对结构塑性极限载荷的影响规律。 (4)考虑了结构中的蠕变损伤累积,建立了基于归一化的蠕变时间和归一化的缺陷尺寸为参量的安全评定方法。可以简便地进行含体积型缺陷高温结构的安全评定。
[Abstract]:High-temperature technology is widely used in the fields of electric power, petrochemical, nuclear energy, aerospace and so on. Creep damage is inevitable in structural components in long service at high temperature. In addition, volume defects such as slag, pits and thinning are often produced in the process of manufacture and service, which weaken the ultimate bearing capacity of the structure. Traditional safety assessment codes do not consider the effect of creep damage accumulation on the ultimate bearing capacity of structures, which may lead to unreasonable assessment results. In this paper, considering the effect of creep damage on the limit load, an elastic-plastic constitutive model of coupled material creep damage is established by combining theoretical calculation with numerical simulation based on the principle of "fit for use". The limit loads of high-temperature structures with volumetric defects are systematically studied, and a safety assessment method considering creep damage accumulation in structures is proposed. The main research work and conclusions are as follows: (1) based on the constitutive model of power-law strengthened materials, the analytical solution of the internal pressure limit load of the thin-walled and non-defective thick wall is derived. The influence of the structure size and material parameters on the internal pressure limit load of the non-defective cylinder is calculated by finite element method, and the analytical solution is verified. (2) through experimental observation, the physical mechanism and influencing factors of creep damage of 2.25Cr1Mo steel are analyzed, and these factors are coupled to the elastoplastic constitutive equation; The elastoplastic constitutive model of coupled creep damage based on Ramberg-Osgood equation is constructed, which can predict the elastoplastic response of high temperature structures with creep damage, which lays a foundation for calculating the ultimate loads of high temperature structures with creep damage. (3) based on the elastoplastic constitutive model, the expansion process and failure mode of plastic region under the action of internal pressure or bending moment of various shapes and sizes of pits and cylindrical vessels with local thinning defects are calculated and analyzed by using the elastoplastic constitutive model. The influence of defect size and creep damage accumulation on the plastic limit load of the structure is analyzed. (4) considering creep damage accumulation in structure, a safety assessment method based on normalized creep time and normalized defect size is established. It is easy to evaluate the safety of high temperature structures with volume defects.
【学位授予单位】：华东理工大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TB302.3;TH49

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