【作者】 郑绵彬；

【导师】 陈国华；

【作者基本信息】 华南理工大学 ， 化工过程机械， 2011， 博士

【摘要】 双层复合壳是指内外层接触介面连接达到冶金结合程度的复合壳体,内外层材料可根据工艺需求和接触介质特性而选定,其材料结构与复合层合板一样,同属于复合材料的范畴。双层复合壳具有许多单层壳无法比拟的优点,在航空、核电和石化等领域具有广泛的应用。由于这些行业工艺、原材料及产品的特殊性,双层复合壳结构一旦发生损伤失效,极有可能造成重大伤亡事故,故对此类结构的损伤模型以及可靠性设计和评估方法进行研究显得十分必要。双层复合壳被广泛地应用在高温和腐蚀环境中,其损伤因素较为复杂,包括流-固耦合和热弹性振动等因素,致使对于该类型壳体的可靠性设计和评估尤其困难。通过文献资料检索,迄今国内外针对高温构件的结构完整性研究较多,而对于多场耦合作用下高温构件的可靠性研究则很少,针对多场耦合作用下双层复合壳高温构件的可靠性研究则更少。本文以多场耦合作用下双层复合壳的损伤模型与可靠性研究为选题,主要开展以下方面的研究:(1)双层复合壳的损伤模型研究通过分析壳体的复合形式和选材原则,明确研究对象性能特点;基于双层复合壳损伤表现形式及内部应力分析,建立双层复合壳热应力损伤模型及温度动态响应函数;推导多场耦合作用下双层复合壳的随机振动疲劳损伤模型。(2)双层复合壳材质损伤特征参量试验研究复杂耦合环境下,双层复合壳的损伤具有明显的局部特征,通过微观的金相、X射线以及宏观的强度、韧度等试验,进行宏观力学性能退化分析和细微观损伤与断裂特性分析,研究壳体材质损伤特征,推断壳体材质损伤的主要原因;选取双层复合壳结构,从壳体不同部位取样进行测试,试验数据作为可靠性分析模型的随机参量,分析壳体的可靠性。(3)热-流-固耦合作用下双层复合壳的动态响应理论研究建立多场耦合作用下复合圆柱壳的动态响应数学模型,模型中的多场耦合偏微分方程包含热载荷和流体冲击载荷,通过求取包含拉普拉斯双算子的多场耦合偏微方程的解,获得壳体动态响应特性随着流体速度、壳体半径和长度以及弹性模量等参量变化的规律及挠度函数。(4)热-流-固耦合作用下双层复合壳的动态响应有限元分析针对典型多场耦合作用下的双层复合壳结构,建立不对称双层复合壳的有限元模型,对双层复合壳在多场耦合作用下的动态响应进行模态、谐响应和多场耦合振动分析,深入研究材料和结构参数改变对结构响应的影响,以及双层复合壳具有的动态响应特性。(5)双层复合壳的可靠性评估方法建立统计三维实体单元节点Von Mises应力的可靠性计算方法,利用ANSYS和MATLAB进行二次开发,实现三维建模、多种载荷作用下的随机有限元求解以及单元节点Von Mises应力的数值统计,应用于实际工程中旋风分离器的动态可靠性评估;在Rice J积分理论的基础上,给出求解双层高温构件JC积分方法,并应用有限元数值算例和工程实例说明JC积分方法的实施效果。JC积分可以作为评估含缺陷双层高温构件可靠性的断裂参量,为传统应力-强度干涉模型提供有益扩充。(6)双层复合壳的可靠性灵敏度分析可靠性灵敏度反映了基本变量分布参数对失效概率的重要性排序,它是结构稳健可靠性优化设计的必要步骤。针对工程应用中存在的随机变量为非正态分布,同时存在相关性的情况,研究相关非正态模型参量可靠性灵敏度分析方法,包括基于正交变换法(OT)、乔列斯基因子分解法(CF)和JC法三种可靠性灵敏度分析方法,分析它们各自的应用优势;应用Visual Basic与MATLAB混合编程技术,编写可靠性灵敏度分析软件系统,并通过数值算例验证所提方法的精度以及可应用计算机解决相关非正态模型参量问题,可作为可靠性灵敏度分析方法的有益扩充。上述研究工作能够为双层复合壳构件的可靠性设计和评估提供理论基础,为保障安全生产和设备维护提供科学依据。更多还原

【Abstract】 Double-layer composite shell is a kind of shell that the bonding interface between inner and outer layer is with metallurgical bond, whose material needs to be selected according to technical requirements. Its material structure is the same as the composite board, which belongs to composite materials. The double-layer composite shell has many incomparable advantages that the single-layer shell does not possess, which has been widely applied in aviation, nuclear power and petrochemical fields etc. Due to the specialty of industries process, raw materials and products, once the damage failure occurs, it is easy to cause significant casualties. Therefore, it is necessary to analyze the damage model as well as the reliability design and evaluation of such equipment.Double-layer composite shell is widely used in high temperature and corrosive environment, so its coupled environment is very complex, including the fluid - solid coupling with thermal elastic vibration and other factors, which makes the reliability design and evaluation extremely difficult. Through the literatures, so far there have been many studies on the structural integrity of high temperature components at home and abroad, but the studies on the reliability evaluation of high temperature components subjected to multi-field coupling are rare, moreover, the studies on the reliability evaluation of double-layer composite shell under high temperature is less. In this paper, the studies on the damage model and reliability of double-layer composite shell subjected to multi-field coupling will be conducted as follows:(1) Damage model of double-layer composite shellThrough analyzing the composite form and selection principles of shell, the performance characteristics of study object is clear. On the basis of analyzing the damage forms and internal stress of double-layer composite shell, the thermal stress damage model of double composite shell was established and the dynamic response was analyzed. Moreover, the fatigue damage model of double-layer composite shell subjected to multi-field coupling was established.(2) Material damage characteristics parametric test of double-layer composite shell Under complex coupling environment, the double-layer composite shell has clear local damage features. The degradation of macro and micro damage characterization were studied through micro-optical, X-ray and macroscopic strength, toughness and so on, which can infer the main damage causes. In addition, through statistical analysis of the experimental data from different parts of the double-layer composite shell structure, random parameters of reliability analysis model was obtained, thus the reliability of the shell can be evaluated.(3) Theory analysis of dynamic response of double-layer composite shell subjected to thermal - liquid - solid multi-field couplingThe mathematical model of dynamic response of composite cylindrical shell subjected to multi-field coupling was established, in which the multi-field coupling partial differential equation contains fluid impact load and thermal load. The solution of partial differential equation, including the double Laplace operator and the dynamic response with the changes of velocity, shell radius and length, and elastic modulus as well as the deflection function were obtained.(4) Finite element analysis of the dynamic response of double-layer composite shell subjected to thermal - liquid - solid couplingAccording to a typical double-layer composite shell structure, the finite element model of asymmetric double-layer composite shell was established, and then a comprehensive analysis on the dynamic response double-layer composite shell subjected to multi-field coupling was conducted, which includes modal, harmonic response and vibration analysis. The impact of material and structural parameters on structural response, as well as the dynamic response of double-layer composite shell was discussed. (5) Reliability assessment method of double-layer composite shell The reliability calculation method with statistical Von Mises stresses of 3D solid element nodes was proposed, and the secondary development technology of ANSYS and MATLAB was used to achieve 3D modeling, solving stochastic finite element and Von Mises stresses statistics. The proposed method was applied to the dynamic reliability assessment of cyclone. Moreover, based on Rice J integral theory, the J C integral approach was applied to solve the reliability of double high temperature components. The numerical and engineering examples were presented to verify the implementation effect of the J Cintegration approach. The J C integral can be used as the fracture parameters to evaluate the reliability of high temperature components with defects, which provides a useful expansion for the traditional stress - strength interference model.(6) Reliability sensitivity analysis of double-layer composite shellReliability sensitivity analysis reflects the importance order of the basic variables with the failure probability, which is the necessary step of robust optimization design of structure reliability. The correlated non-normal distribution random variables do exist in engineering, so the reliability sensitivity analysis model of correlated non-normal was studied. The three reliability sensitivity analysis methods, named orthogonal transformation method (OT), decomposition method (CF) and JC method respectively, were given, and their application advantages were analyzed. In addition, the mixed programming technology of Visual Basic and MATLAB was employed to develop the reliability sensitivity analysis system. The proposed methods were verified by numerical example and the correlated non-normal problem can be solved with computer, which can be used as a useful extension for the reliability sensitivity analysis methods.The study provides a theoretical basis for reliability design and evaluation of double-layer composite shell as well as the scientific basis for the work safety and equipment maintenance.更多还原