应用修正正交有限内存拟牛顿算法的全波形反演

全波形反演(FWI)通过最小化观测数据与计算数据之间的误差,得到高分辨率的地下模型参数。正则化技术常用来克服FWI的不适定性。复杂地质模型可能同时具有平滑特征及锐利边界,单一的正则化方法往往不能得到令人满意的反演结果。为此,针对带有混合正则化的目标泛函不可微性,提出一种修正正交有限内存拟牛顿方法,求解相应的正则化目标泛函。在具有复杂构造的修正Marmousi模型以及BG Compass模型上进行数值模拟试验,且与不带有正则化的全波形反演及邻近有限内存拟牛顿方法进行比较,结果表明所提修正正交有限内存拟牛顿算法在计算效率及定量分析上具有明显的优越性。     

Fatigue life prediction and experiment research for composite laminates with circular hole

Based on the fatigue prediction model of exponential function and Whitney-Nuismer(WN) criterion of static strength for the composite material laminate with a circular hole, the stress correct factor (β) was put forward and a new fatigue prediction model for composite material laminate was set up. T300/KH304, which is recently studied and is a high capability composite material, was used as the raw material. In order to gain the factor β, the fatigue experiments of the laminates with holes in different diameters and the same ratio of width to diameter were conducted. The fatigue analysis and tests of the laminates with a hole 5 mm in diameter are carried out at different stress levels, and the results meet the engineering requirement. The simple, prompt and practical method is provided for the prediction of S-N curve of composite laminate with a circular hole.     

先进纤维增强复合材料疲劳寿命的预测

本文综述了纤维增强复合材料疲劳理论近年来的研究成果,对各种疲劳模型的建立、参数含义以及特点进行了详细的阐述分析,并展望了今后的发展趋势。     

弯曲载荷下机织复合材料T型接头渐进失效分析

根据树脂传递模塑(RTM)成型的缎纹机织复合材料T型接头的结构特征和纤维布局特点, 基于ANSYS有限元数值分析平台, 建立符合其真实结构的几何模型和有限元分析模型。基于渐进失效强度预测方法的基本思想, 使用有限元计算软件ANSYS的参数化设计语言(APDL)开发相应的程序, 实现改进形式的Hashin失效准则。采用合适的最终失效评价方法, 建立二维机织结构复合材料T型接头受弯曲载荷时的渐进失效预测方法, 能够有效地模拟从初始加载到最终失效过程中机织复合材料T型接头结构的力学响应及损伤的萌生与发展, 并预测结构的静强度。      

基于粘塑性的单晶镍基合金晶体学本构模型

单晶镍基合金在涡轮叶片上得到越来越广泛地应用,对单晶材料本构模型的研究也在不断地深入。本文运用晶体学理论,结合现象学的统一本构模型的优点,进行了单晶镍基合金的本构建模,模型基于晶体学滑移理论,在单晶八面体12个滑移系和立方体6个滑移系的微观水平上建立粘塑性流动方程和硬化方程,该方程采用粘塑性统一本构方程的一般形式。建模过程表明晶体模型物理意义更明确,计算结果则表明模型是准确的。     

等离子热障涂层构件高温热疲劳寿命预测研究

针对等离子热障涂层构件的变形特点,在总结热障涂层热疲劳寿命相关文献研究成果的基础上,合理设计了平板和圆管试样的高温氧化与热疲劳试验。根据菲克定律,结合高温氧化实验数据建立粘接层Al贫化的数学模型。把粘接层Al浓度作为耦合氧化损伤的控制参量引入寿命预测模型,建立氧化损伤和热疲劳损伤耦合作用的等离子热障涂层寿命预测模型。寿命预测结果表明该寿命预测模型合理、方法可行。     

航空发动机复合材料机匣在轴向压力和内压耦合作用下屈曲特性的有限元分析

复合材料是60年代出现的一种性能优异的新型材料,目前在航空航天结构领域里已得到了一些应用.本文利用线性板壳理论和线性屈曲模型,对航空发动机树脂基复合材料外涵道机匣构件的特点进行结构有限元建模和在轴向和径向载荷单独和耦合作用下屈曲特性进行有限元分析,可供航空发动机的复合材料机匣的结构设计参考.     

Evaluation of properties and thermal stress field for thermal barrier coatings

In order to get thermal stress field of the hot section with thermal barrier coating (TBCs), the thermal conductivity and elastic modulus of top-coat are the physical key properties. The porosity of top-coat was tested and evaluated under different high temperatures. The relationship between the microstructure (porosity of top-coat) and properties of TBCs were analyzed to predict the thermal properties of ceramic top-coat, such as thermal conductivity and elastic modulus. The temperature and stress field of the vane with TBCs were simulated using two sets of thermal conductivity data and elastic modulus, which are from literatures and this work, respectively. The results show that the temperature and stress distributions change with thermal conductivity and elastic modulus. The differences of maximum temperatures and stress are 6.5% and 8.0%, respectively.     

In-situ measurement of elastic modulus for ceramic top-coat at high temperature

The ceramic thermal barrier coatings (TBCs) play an increasingly important in advanced gas turbine engines because of their ability to further increase the engine operating temperature and reduce the cooling, thus help achieve future engine low emission, high efficiency and improve the reliability goals. Currently, there are two different processes such as the plasma spraying (PS) and the electron beam-physical vapor deposition (EB-PVD) techniques. The PS coating was selected to test the elastic modulus. Using the nanoindentation and resonant frequency method, the mechanical properties of ceramic top-coat were measured in-situ. According to the theory of the resonant frequency and composite beam, the testing system was set up including the hardware and software. The results show that the accurate characterization of the elastic properties of TBCs is important for stress-strain analysis and failure prediction. The TBCs systems are multi-layer material system. It is difficult to measure the elastic modulus of top-coat by tensile method. The testing data is scatter by nanoindentation method because of the microstructure of the ceramic top-coat. The elastic modulus of the top-coat between 20?1 150 ℃ is obtained. The elastic modulus is from 2 to 70 GPa at room temperature. The elastic modulus changes from 62.5 GPa to 18.6 GPa when the temperature increases from 20 ℃ to 1 150 ℃.     

基于数字图像相关方法的气凝胶复合材料各向异性热变形测量

在热防护材料及结构高温力学性能研究中,测量其在热载荷与机械载荷作用下产生的变形是重要且基础的工作。基于数字图像相关方法,建立了可实现800℃变形测量的非接触式测量系统。针对陶瓷纤维增强SiO_2气凝胶复合材料,从面外和面内两个材料方向,以25℃为参考温度,试验测量了材料加热至300~800℃范围内不同温度时产生的热变形。研究结果表明,在此试验系统基础上的变形测量方法可用来测量此类热防护材料的高温变形。陶瓷纤维增强SiO2气凝胶复合材料的高温热变形具有明显的各向异性,面外方向上表现为"收缩",面内方向上表现为"膨胀"。SiO_2气凝胶基体中的颗粒团聚以及增强纤维在面内方向上的铺层分布是导致热变形各向异性的主要原因。