含局部减薄水电站压力钢管塑性失效机理和极限承载力研究

发布时间：2018-06-16 13:26

本文选题：局部减薄 + 光面管　；参考：《广西大学》2017年硕士论文

【摘要】：在水、泥沙长期侵蚀和冲刷下,水电站压力钢管表面常会出现局部减薄缺陷,导致压力钢管极限承载力降低,发生塑性失效问题,影响压力钢管的安全。本文在课题组以往无缺陷压力钢管极限承载力研究成果基础上,针对含局部减薄水电站光面管和加劲管,开展了管道结构的塑性失效机理和极限承载力研究,主要内容为:(1)从含局部减薄模型建立、增量迭代方法、收敛准则、失效准则等方面,结合已有试验数据,研究并验证了适用于含局部减薄水电站压力钢管极限承载力分析的弹塑性增量有限元(EPIA)数值模拟方法,同时建议:考虑材料应变硬化进行管道极限承载力分析;采用真实应力应变曲线进行管道极限承载力分析;低强度和中高强度钢材压力钢管失效参考应力分别取为0.9σu'和σu'(σu'为钢材真实抗拉强度)。(2)揭示了含局部减薄水电站光面管的塑性失效机理,确定了其极限承载力的主要影响因素,建立了分别适用于低强度和中高强度钢材的极限承载力简化计算公式。研究表明:不同强度钢材含局部减薄光面管失效过程基本相同,但失效模式可分为三类,与材料参数和局部减薄尺寸有关;无量纲化极限承载力主要影响因素为局部减薄深度c、轴向长度a和环向宽度b,其影响程度依次降低。基于以上影响因素研究拟合得到了以不含局部减薄光面管极限承载力P0、a、b和c为变量的极限承载力简化计算公式。(3)揭示了含局部减薄水电站加劲管的塑性失效机理,确定了其极限承载力的主要影响因素,建立了相应的极限承载力简化计算公式。研究表明:含局部减薄加劲管失效模式和光面管基本相同;靠近局部减薄区域的加劲环对极限承载力有显著影响;局部减薄尺寸较大时加劲管pL明显大于光面管,但极限承载力影响因素相同,基于含局部减薄光面管的极限承载力计算公式提出了加劲管的极限承载力简化计算公式。
[Abstract]:Under the condition of water and sediment erosion and erosion for a long time, local thinning defects often occur on the surface of penstock in hydropower station, which leads to the reduction of ultimate bearing capacity of penstock and the occurrence of plastic failure, which affects the safety of penstock. Based on the previous research results of the ultimate bearing capacity of the penstock without defects, the plastic failure mechanism and ultimate bearing capacity of the pipeline structure are studied for the smooth and stiffened pipes of the hydropower station with local thinning. The main contents are as follows: (1) from the aspects of building model with local thinning, incremental iteration method, convergence criterion, failure criterion and so on, combined with the existing experimental data, The numerical simulation method of elastic-plastic incremental finite element method (EPIA) which is suitable for the ultimate bearing capacity analysis of penstock with local thinning is studied and verified. It is also suggested that the ultimate bearing capacity of pipeline should be analyzed with the consideration of material strain hardening. The ultimate bearing capacity of pipeline is analyzed by using the true stress-strain curve. The failure reference stress of low strength steel pipe and medium and high strength steel pipe are taken as 0.9 蟽 u 'and 蟽 u' (蟽 u'is the real tensile strength of steel) respectively. The plastic failure mechanism of smooth surface pipe with local thinning is revealed, and the main influencing factors of ultimate bearing capacity are determined. A simplified formula for calculating the ultimate bearing capacity of low strength steel and medium strength steel is established. The results show that the failure process of steel with different strength is basically the same, but the failure modes can be divided into three types, which are related to material parameters and local thinning size. The main influencing factors of dimensionless ultimate bearing capacity are local thinning depth (c), axial length (a) and circumferential width (b), which decrease in turn. Based on the above factors, a simplified formula for calculating the ultimate bearing capacity of smooth surface tubes without local thinning is obtained, which takes P0 and c as variables), which reveals the plastic failure mechanism of stiffened pipes in hydropower stations with local thinning. The main influencing factors of ultimate bearing capacity are determined and the corresponding simplified formula of ultimate bearing capacity is established. The results show that the failure mode of the stiffening tube with local thinning is basically the same as the smooth tube, the stiffening ring near the local thinning area has a significant effect on the ultimate bearing capacity, and the pL of the stiffening tube is obviously larger than that of the smooth tube when the local thinning size is larger. However, the influence factors of ultimate bearing capacity are the same. A simplified formula for calculating ultimate bearing capacity of stiffened pipe is proposed based on the formula of ultimate bearing capacity of tube with local thinning and smooth surface.
【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】：TV732.41

【相似文献】