Design and preparation of high permeability porous mullite support for membranes by in-situ reaction

The natural mineral kaolin combined with alumina additives Al(OH)₃,α-Al₂O₃ and AlF₃ was used to prepare porous mullite ceramic membrane supports using an in-situ reaction. The effects of composition and sintering temperature on the sintering behavior, pore structure, permeability and microstructure of the resulting porous mullite supports were extensively investigated. The experimental results showed that excess SiO₂ in kaolin can be consumed by adding alumina precursors, which resulted in a stiff skeleton of interlinked needle-like mullite crystals in-situ during the sintering. The needle-like mullite crystals touched each other and formed a short network, which acted as a porous skeletal network structure. This network resulted in a highly permeable porous structure. The resulting support is suitable for the preparation of asymmetric ceramic membranes. The densification and pore structure of the support can be effectively adjusted by control of the quantity of alumina precursors in the composition and the sintering temperature. Sintering the subject mullite compositions at 1500 °C for two hours resulted in support structures with an average porosity of 45.9%, an average pore size of 1.3 µm and a penetrating porosity of 35.9%.     

Fatigue life prediction of a stainless steel plate-fin structure using equivalent-homogeneous-solid method

Stainless steel plate-fin heat exchangers are key components in nuclear power stations and hydrogen production systems using High Temperature Gas-cooled Reactors (HTGR). Fatigue is the most failure mode for plate-fin structures because they operate under cyclic high pressures and high temperatures. This paper establishes a life prediction method of fatigue based on equivalent-homogeneous-solid method for a 304 stainless steel plate-fin structure. A finite element analysis (FEA) program of fatigue life has been developed, which has been verified by fatigue experiments. By using this method, both the local stress concentration and the fatigue life for the whole plate-fin structure can be predicted. The results show that the fatigue cracks initiate at the fillet and then propagate to the interface and eventually the base metal of fin. The fatigue fracture in the filler metal shows brittle character, while typical dimple and striation are shown in the base metal.     

P91钢蠕变-疲劳交互作用应变特征与寿命预测

对电厂用关键材料P91钢在546℃下进行应力控制的蠕变疲劳交互作用研究,分别对滞回线,全应变范围,平均应变和非弹性应变进行分析和讨论。基于应力控制蠕变-疲劳交互实验特点,考虑了上下保载时间对寿命的影响,采用改进型的频率修正法对P91钢进行寿命预测。研究结果表明:应力控制下的蠕变-疲劳交互作用,使P91钢呈现兼有循环蠕变与静蠕变的失效形式,随着循环数的增加,滞回线向右移动:非弹性应变影响了蠕变-疲劳交互寿命,其增长速率随着材料寿命的减小而增大。寿命预测结果与试验结果吻合较好,95%的数据点落于2倍误差带范围之内。研究结果为P91钢蠕变疲劳寿命预测提供了理论和实验基础。     

基于碳化物相分析法的12Cr1MoV过热器管寿命无损评价

采用时效试验、持久试验、电解萃取试验以及碳化物相X射线衍射分析,建立了12Cr1MoV高温过热器管中碳化物相比值（M23C6/M3C）R与Larson-Miller参数P的关系方程,并同时利用该方程和传统的L-M方法对一根已服役140000 h的12Cr1MoV高温过热器管进行剩余寿命预测,结果表明,两者剩余寿命预测结果差值占总寿命的16%～19%,且碳化物相分析法的预测结果偏安全。     

基于UG/Grip的斜齿轮盘铣刀齿廓截形计算与参数化建模研究

针对在数控成型铣齿加工中斜齿轮盘铣刀轴截面设计和参数化建模所遇到的问题,提出了基于UG/Open Grip模块解决问题的简洁、高效、集成方法.利用Grip的较强的逻辑分析和计算能力,已知齿轮参数根据空间接触线法计算斜齿轮盘铣刀轴截形;利用Grip的人机交互和三维建模功能,用户输入不同模数、齿数、螺旋角等基本参数来设计盘铣刀三维模型.开发出来的模块对提高斜齿轮盘铣刀的设计效率和精度有重要的指导意义与实用价值.     

基于OpenGL的数控成形铣齿加工过程仿真的研究

对某数控科技有限公司生产的SKXC-3000/20型高速数控铣齿机展开研究,深入分析成形法铣齿加工过程,以OpenGL和Visual C++为开发工具,开发一个数控铣齿加工虚拟仿真系统。在虚拟加工仿真系统界面中输入齿轮参数、刀具参数,经处理得到对应数控加工代码,并对代码进行检验和翻译得到加工运动数据和状态数据,由运动数据驱动虚拟机床部件的运动。通过刀具扫描体模型与离散工件模型进行布尔运算实现材料切除过程,发现铣齿加工过程中部件间的干涉碰撞等现象,有效的检验NC程序的正确性。     

数控成形磨齿机砂轮截形计算

砂轮加工斜齿轮时,斜齿轮齿面法线与砂轮轴线相交。利用这一原理,首先根据斜齿轮方程,计算斜齿轮与砂轮的接触线,求得加工斜齿轮时的砂轮廓形;其次,考虑到实际加工砂轮时金刚轮半径的存在,对砂轮刃形部分和过渡曲线部分分别进行了半径补偿;最后,利用B样条曲线和de boor算法,根据插补步长要求,运用时间分割插补算法,得到金刚轮加工砂轮时的插补点,给出了计算实例,并对砂轮廓形进行了拟合。     

对多起乙烯裂解炉HP型炉管失效原因的分析总结

裂解炉炉管是乙烯生产装置关键设备乙烯裂解炉的核心部件,承受高温复杂环境所引起的各种损伤。某大型石化企业在近年连续发生数起因HP型（Cr25Ni35和Cr35Ni45）炉管失效引起的裂解炉故障,影响了乙烯装置的安全、长周期运行。采用金相分析、扫描电镜、能谱分析等多种手段,对这几起故障的表现特点和失效原因进行了分析。分析结果表明,炉管在高温下长期运行造成的渗碳、蠕变等损伤以及高温硫腐蚀是造成这几起HP型炉管失效的主要原因。     

回转支承的故障监测诊断技术研究

回转支承的故障监测诊断技术的研究对于提高设备的运行效率、减少经济损失具有重要的意义.有针对性地概述了基于振动信号、温度信号、摩擦力矩、声发射、应力波的回转支承监测诊断技术,以及针对上述信号的分析处理方法,其中包括针对回转支承局部缺陷信号诊断的HHT、EEMD-MSPCA等方法.最后,对各监测诊断方法进行比较,并提出基于...     

盘形成形铣刀的刀具磨损故障诊断方法研究

通过分析高速铣齿机的盘形成形铣刀及其铣削过程的特殊性、刀具磨损的信号采集和处理方法.选用电流法监测数控铣齿机的主轴电动机电流,采用BP神经网络方法对信号进行处理,最后实现对盘形成形铣刀的刀具磨损诊断.经实验证明,该铣刀的电流监测和基于BP神经网络数据处理的方法具有良好的诊断性能.