局部配置法求解TBC界面裂纹应力强度因子研究

主要探讨了应用局部配置法求解拉伸载荷下和热载荷下陶瓷隔热涂层界面裂纹的应力强度因子的方法.对于陶瓷隔热涂层,其陶瓷层与粘结层之间的界面裂纹的应力强度因子是复型的,它包括应力强度因子的模和相位角.其求解与传统均质材料的应力强度因子是不同的.     

双向梯度复合材料裂纹尖端应力强度因子研究

为了进一步改善梯度复合材料力学分析及设计水平,推导了一种适用于双向梯度复合材料断裂特性分析的梯度扩展单元法(XFEM).采用细观力学方法描述材料沿梯度方向变化的力学属性,通过线性插值位移场给出了4节点梯度扩展单元随空间位置变化的刚度矩阵,建立了结构的连续梯度有限元模型,并采用交互能量积分计算得到了裂纹尖端的应力强度因子(SIF).通过与已有文献结果对比验证了梯度扩展单元的优越性,并讨论了双向梯度结构中相关参数对SIF的影响规律,得到结论:梯度扩展单元能够提高梯度材料中裂纹尖端SIF的计算精度,其计算结果随着网格密度的增加迅速收敛于精确解;双向梯度结构的组份分布形式和属性梯度能够明显影响裂纹尖端的SIF;对于多裂纹双向梯度结构,裂纹间的相互作用增大了裂纹尖端的SIF,弹性模量大的一侧SIF较大.     

Numerical investigation on jet interaction with a compression ramp

A numerical investigation on jet interaction in supersonic laminar flow with a compres- sion ramp is performed utilizing the AUSMDV scheme and a parallel solver. Several parameters dominating the interference flowfield are studied after defining the relative increment of normal force and the jet amplification factor as the evaluation criterion of jet control performance. The computational results show that most features of the interaction flowfield between the transverse jet and the ramp are similar to those between a jet and a flat plate, except that the flow structures are more complicated and the low-pressure region behind the jet is less extensive. The relative force increment and the jet amplification factor both increase with the distance between the jet and the ramp shortening till quintuple jet diameters. Inconspicuous difference is observed between the jet-before-ramp and jet-on-ramp cases. The variation of the injection angle changes the extent of the separation region, the plateau pressure, and the peak pressure near the jet. In the present computational conditions, 120 is indicated relatively optimal among all the injection angles studied. For cold gas simulations, although little influence of the jet temperature on the pressure distribution near the jet is observed under the computation model and the flow parameters studied, reducing jet temperature somehow benefits the improvement of the normal force and the jet efficiency. When the pressure ratio of jet to freestream is fixed, the relative force increment varies little when increasing the freestream Mach number, while the jet amplification factor increases.     

橡胶密封材料加速系数研究

根据6种橡胶密封材料的加速老化试验数据和自然贮存数据,分别计算出加速系数,并对加速温度之间的加速系数进行了研究.结果表明:除氟橡胶外,橡胶密封材料的加速系数符合范德霍夫规则,即加速系数在2～4内.在无自然贮存数据的情况下,整机加速试验采用加速温度之间的加速系数作为橡胶密封材料的加速系数更接近于实际情况.     

工科院校开展“双语文化”素质教育的必要性

语言是一扇窗户。通过这扇窗户,能够进一步了解创作者的思想。多学一个语言,就是为自己多打开一扇窗户。英语是世界通用语,各国政治、经贸、文化、体育等交流都离不开它。中文是世界人口使用最多的语言。中国在崛起,华语文化也在世界各地蓬勃开展。要想知己知彼,让中华文化在全球立于不败,必须加强高校人文素质教育,使学生具备双语文化素质。我国工科院校学生理工科专业知识扎实,但对母语文化重视不够,甚至缺失,对外来文化更是理解认识不够。这就是本文探讨的重点。     

高精度星相机光学系统像质评价及实现

摘要： 高精度星相机光学系统是实现高性能星相机的关键技术.从工程实际出发，梳理星相机光学系统像质评价的指标，重点论述星点质心位置指标分解、光学系统评价指标分解过程.分析认为星相机光学系统设计过程中需关注质心位置偏差和质心位置与理想像高的偏差、温度分析需兼顾均匀温升及梯度温度变化.给出一个继承于双高斯结构形式的设计实例，结合像差理论进行消热设计和畸变控制，分析不同温度条件下不同类别恒星的质心位置一致性.设计结果表明该光学系统可满足高精度星相机指标要求.     

负载对超声加工声学系统特性的影响

以一维超声振动系统为研究对象,以点、线、面三种不同的加载方式对工件进行加载,研究了负载对超声加工声学系统特性的影响。实验表明,当以点、线的加载方式对工件进行加载时,载荷的变化对声学系统特性各参数的影响不大;而当加载方式为面接触时,机械品质因数Qm、谐振频率fs和动态电阻R随着载荷F的增大有明显的增大趋势,动态电容C和最大电导Gmax却随着载荷F的增大而减小。     

计入导线故障的民机安全性定量分析方法研究

将导线故障引入安全性定量分析方法中，介绍了安全性分析的现状、存在的问题以及计入导线故障的必要性。通过将导线故障和安全性分析相结合，提出一种计人导线故障的安全性定量分析方法。对影响导线故障的机理进行探究与分析，提出“导线故障率影响因子”概念，阐述了影响导线故障率的主要因素及其类型，建立了一种民用飞机实际导线故障率计算方法与模型，以及在单一状态和多种状态下导线故障率计算方法，并对方法进行案例分析，使安全性定量分析更准确、有效和完善，大大减少了导线故障所引起的不安全事件，为民用飞机安全性和合格审定工作提供了有力的支持。     

地基应力对土基剪切波速的影响建模

地基剪切波速与土基密实程度直接相关,广泛应用于场道地基压实质量评估。现有剪切波速测试模型主要考虑干密度、含水率等因素,忽略了土基应力对剪切波速的影响,导致利用剪切波速测定高深度及大应力状态土层力学性能时存在较大误差。本文设计了土基应力与剪切波速试验装置,开展了变应力条件下粘土和砂土两种土样的剪切波速试验,研究了土颗粒应力传播及应力损失条件下剪切波速变化特性,建立了基于应力扩散的地基土剪切波速与土中应力相关性模型,并对模型计算结果与现场实测数据进行对比分析,以验证模型的有效性。结果表明:土基剪切波速随应力的增大总体呈增大趋势;应力相等条件下,土体剪切波速随测试土层厚度的增大而下降,地基应力对土基剪切波速影响显著。     

Software defect prevention based on human error theories

Software defect prevention is an important way to reduce the defect introduction rate.As the primary cause of software defects,human error can be the key to understanding and preventing software defects.This paper proposes a defect prevention approach based on human error mechanisms:DPeHE.The approach includes both knowledge and regulation training in human error prevention.Knowledge training provides programmers with explicit knowledge on why programmers commit errors,what kinds of errors tend to be committed under different circumstances,and how these errors can be prevented.Regulation training further helps programmers to promote the awareness and ability to prevent human errors through practice.The practice is facilitated by a problem solving checklist and a root cause identification checklist.This paper provides a systematic framework that integrates knowledge across disciplines,e.g.,cognitive science,software psychology and software engineering to defend against human errors in software development.Furthermore,we applied this approach in an international company at CMM Level 5 and a software development institution at CMM Level 1 in the Chinese Aviation Industry.The application cases show that the approach is feasible and effective in promoting developers' ability to prevent software defects,inde pendent of process maturity levels.