考虑材料应变硬化的水电站压力钢管极限承载力分析方法

发布时间：2018-06-09 03:20

本文选题：压力钢管 + 材料应变硬化　；参考：《广西大学》2017年硕士论文

【摘要】：结构极限承载力是水电站压力钢管强度设计和安全评估的重要指标,目前水电站压力钢管结构极限承载力分析大多偏于安全地将材料简化为理想弹塑性材料,不考虑材料应变硬化对极限承载力的影响。然而,材料应变硬化对水电站压力钢管极限承载力有显著的提高,为充分利用钢材有必要考虑材料应变硬化的影响。基于此,本文在课题组以往研究成果基础上,开展了考虑材料应变硬化的水电站压力钢管极限承载力分析方法研究,主要内容包括:(1)结合理论分析和实验资料,拟合得到了压力钢管钢材常用的双线性、幂强化、Ramberg-Osgood和ASME本构关系,并开展了这四种本构关系对压力钢管极限承载力和失效演化的影响规律研究。基于双线性、幂强化、Ramberg-Osgood和ASME本构模型的函数形式,采用试验数据拟合得到考虑材料应变硬化的的四种本构关系,拟合优度分析表明各本构关系均能良好反映压力钢管材料应变硬化性能。研究表明,考虑材料应变硬化的结构极限承载力分析结果较不考虑可提高20%以上,前述四种硬化本构关系对管道失效演化与极限承载力分析结果影响不大,极限承载力结果的差别在8%以内。(2)提出了基于等效理想弹塑性模型的压力钢管极限承载力分析方法。基于应变能守恒原则提出了等效屈服强度的两种计算方法:根据全应力-应变曲线求解等效屈服强度;根据屈服强度与抗拉强度双关键点数据求解等效屈服强度。研究表明,基于等效理想弹塑性模型的分析方法能便捷地评估管道结构极限承载力,计算误差在10%以内。(3)考虑材料应变硬化,提出了压力钢管极限承载力分析的弹性模量缩减法(EMRM)。基于等效理想弹塑性模型,定义了考虑材料应变硬化效应的单元承载比,给出了动态判别高承载单元的基准承载比,利用变形能守恒原则确定高承载单元弹性模量缩减策略,进而建立了考虑材料应变硬化下结构极限承载力分析的EMRM。为高效求解管道结构极限承载力提供了新途径。
[Abstract]:Structural ultimate bearing capacity is an important index for strength design and safety assessment of penstock in hydropower stations. At present, the analysis of ultimate bearing capacity of penstock structures of hydropower stations is mostly focused on safely simplifying the material to ideal elastic-plastic material. The effect of strain hardening on ultimate bearing capacity is not considered. However, the material strain hardening has a significant increase on the ultimate bearing capacity of the penstock in hydropower stations. In order to make full use of steel, it is necessary to consider the effect of material strain hardening. Based on the previous research results of the research group, this paper studies the ultimate bearing capacity analysis method of penstock in hydropower station considering material strain hardening, the main content of which includes theoretical analysis and experimental data. The bilinear, power-reinforced Ramberg-Osgood and ASME constitutive relations of steel tube are obtained by fitting. The influence of these four constitutive relations on ultimate bearing capacity and failure evolution of penstock is studied. Based on the function form of the bilinear, power-enhanced Ramberg-Osgood and ASME constitutive models, four constitutive relations considering strain hardening of materials are obtained by fitting the experimental data. The analysis of goodness of fit shows that each constitutive relation can well reflect the strain hardening property of steel tube material. The results show that the analysis results of ultimate bearing capacity of structures considering strain hardening of materials can be increased by more than 20%, and the above four kinds of hardening constitutive relations have little influence on the failure evolution and ultimate bearing capacity analysis results of pipelines. The difference of ultimate bearing capacity results is less than 8%.) an analysis method of ultimate bearing capacity of penstock based on equivalent ideal elastoplastic model is proposed. Based on the principle of conservation of strain energy, two calculation methods of equivalent yield strength are proposed: the equivalent yield strength is calculated according to the full stress-strain curve, and the equivalent yield strength is calculated according to the data of the two key points of yield strength and tensile strength. The results show that the analysis method based on the equivalent ideal elastoplastic model can be used to evaluate the ultimate bearing capacity of pipeline structure conveniently, and the calculation error is less than 10%. In this paper, the elastic modulus reduction method for ultimate bearing capacity analysis of penstock is presented. Based on the equivalent ideal elastic-plastic model, the load-bearing ratio of the element considering the strain hardening effect of the material is defined, the reference load ratio of the high-bearing element is dynamically distinguished, and the reduction strategy of the elastic modulus of the high-bearing element is determined by the principle of conservation of deformation energy. Furthermore, an EMRM is established to analyze the ultimate bearing capacity of structures under strain hardening. It provides a new way to solve the ultimate bearing capacity of pipeline structure efficiently.
【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV732.4

【参考文献】