【作者】 刘长海；

【导师】 唐立强；

【作者基本信息】 哈尔滨工程大学 ， 固体力学， 2003， 博士

【摘要】 超高压管式反应器(以下简称反应器)是聚乙烯生产装置中关键设备之一，其运行是否安全可靠直接关系到企业的产值、利润，甚至人的生命。反应器安全工程中的损伤问题研究是工程界和理论界急需解决的现实问题。对这一问题进行探索性的研究，将为反应器安全研究和工程中制定合理检维修计划，提供可依赖性的理论依据。 针对实际工程提出的问题，论文试图在损伤力学的层面上揭示反应器的损伤机理。从损伤力学理论的角度，结合试验，对反应器的自增强损伤机理、反应器疲劳损伤寿命、热冲击下反应器残余应力的衰减等问题展开研究工作。 由反应器工作的现场提取试样，依据反应器实际运行条件(温度、压力等)和服役史(运行记录)，进行了一系列反应器材料30CrNiMo8钢的常规力学试验和疲劳损伤试验。反应器的疲劳试验结果充分反映了反应器材料在不同应力应变水平下的疲劳寿命。这对该反应器进行检验与评定提供了可靠的数据。由于该钢材为引进材料，国内对这种型号的钢材料还没有进行系统的研究，因此，本试验结果将为国内该材料反应器的设计及维护提供可靠的数据基础。 在阐述热力学内变量理论与损伤本构方程、各向同性材料耦合损伤理论的基础上，建立了非线性损伤本构方程等损伤理论模型。研究了反应器自增强损伤的机理。采用细观力学的方法，建立并给出了损伤区和判定初始损伤区的条件；指出用损伤技术使反应器圆筒产生自增强的原因，是由于其材料内部细观结构的变化。从残余应力计算中可知，采用损伤力学原理，使厚壁圆筒产生自增强的效果，从理论上是可行的。 反应器裂纹萌生寿命是衡量反应器安全等级的重要参量，进行反应器的疲劳试验和疲劳损伤分析是反应器安全损伤研究的必须环节。由疲劳循环和损伤间存在耦合关系出发，从唯象的角度，基于低周疲劳试验和高低循环复合疲劳试验，建立并确定了裂纹萌生寿命的疲劳损伤模型。进一步给出弹、塑性光滑试件疲劳裂纹萌生寿命弹性解、塑性解和弹塑性通解的公式。该公式具有一个反映结构形状与边界条件约束的影响函数f(ξ)，其中ξ与即时周期的应力、应变分布相关，因而它不仅考虑了材料本身的疲劳特性，同时还考虑具体结构特性和环境载荷的作用情况。与Manson-coffin公式相比，公式具有的准确性和适用性，不仅为工程实际问题的解决提供了方便，而且在理论上具有创新性。 应用损伤理论和实验进行了反应器实际工况的疲劳损伤分析，确定了反应器实际裂纹萌生寿命，得出反应器的有效损伤半径和影响参数及影响参数的函数值，从而给出裂纹萌生寿命的设计曲线及计算公式。这些为反应器的安全评估提供了理论和实验的参考依据。哈尔滨工程大学博士学位论文 提出了疲劳寿命的减少系数凡的概念，给出了计算凡预测结构的疲劳寿命的具体过程，这一问题的研究使以平滑材料控制应变疲劳试验得出的S一N曲线图为基础来预测有损伤材料的疲劳寿命成为可能。 反应器既要承受上千度异常高温，又要承受温度、压力急剧增加和急剧下降的过程，造成了反应器的热冲击损伤。论文研究了反应器承受热冲击作用的应力响应，给出了热弹性力学基本方程及方程解，探讨了热应力随时间的变化及当量应力与半径的关系，从而为研究反应器减小热冲击损伤提供了理论参考。 对反应器自增强损伤机理和疲劳损伤等问题的研究为超高压容器取材、安全性设计以及确保高压容器长期、稳定和安全运行有着建设和指导意义。更多还原

【Abstract】 Super-high pressure tubular reactor is one of the most important equipments in the productive process of polyethylene. Its safety and reliability are vital to the production, profit and workers’ life. Study on the damage problem of reactor safety engineering in theory and practice is necessary and urgent. The exploratory study in the field will provide a reliable theoretical basis for the safety study of reactor and reasonable project of overhaul.To the practical engineering issues, the author tries to show the damage mechanism of the reactor in view of damage mechanics. Combined with the tests, the author uses the damage mechanics theory to study the self-reinforced damage mechanism, reactor life of fatigue damage, and the decay of residual stress under thermal impact action.According to the practical working condition and operating record, a series of normal mechanics and fatigue damage tests are carried out with the reactor materials (30CrNiMo8), the test materials are obtained from the practical field. The results of fatigue test of reactor manifest the fatigue life of the reactor materials under different strain and stress condition. This provides the reliable data for examination and assessment of the reactor. Because the materials of the reactor are imported, there is no systematic study on the materials. Thus, the experimental results given in the paper will provide reliable data for reactor design and repair with the materials.On the basis of expounding the theory of the thermal inner variables, the constitutive equation of fatigue damage, and the coupling damage theory of the homogeneous isotropic materials, the author set up the theory model of constitutive equation of non-linear damage and so on. The self-reinforced damage mechanism was also studied. By the microscopic mechanics, the damage zone and the initial damage condition are given. The cause of self-reinforcement by using the damage technology was point out. that is due to the changes of inner microstructure of the materials. From the calculation results, it is feasible in theory to produce self-reinforced effect of reactor by adopting the damage mechanical principle.The producing time of crackle is very important parameter to judge the safe grade of the reactor. Fatigue tests and fatigue damage analysis are very important for study of the reactor safe and damage. Begin with the coupling relationship between the fatigue cycle and damage, based on low cycle fatigue test and combined fatigue test with high and low cycles, the model of fatigue damage fordetermined the crackle producing time was established in view of the macroscopic aspect, and the general formula with elastic solution, plastic solution and elastic-plastic solution for the reactor crackle life of elastic and plastic smooth work pieces are also given in the paper. The formula is a function /( ξ), effected by the structure shape and the boundary condition restriction, there ξ is related to the distribution of the instant cycle’s strain and stress, and it considered not only the fatigue characteristic, but also, the real structure characteristic and the effect of the loading. Compared with Manson-Coffin equation, the formula is more accurate and applicable. It is not only providing a convenience to solve the practical problem, but also innovating in theory.By damage theory and test, and analysis the fatigue damage of the reactor in working state, the reactor life of crackle producing was determined. And the effective radium, influence factors and their function values were obtained. Therefore, the designed curve and calculative equation for reactor life of crackle were given in the paper. These are references of theory and test for safety assess of reactors.The paper put forward the concept of decrease coefficient (KD), and the actual calculation process of KD for forecasting the fatigue life of the structure. The research made it possible to forecast the fatigue life of damaged materials, and the prediction was based on the S-N curve from the fatigue test of th更多还原