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121.
针对热障涂层在热循环载荷下陶瓷层表面和氧化层/黏结层界面形成裂纹而导致涂层失效的问题,采用扩展有限元和内聚力单元建立陶瓷层表面裂纹与氧化层/黏结层界面裂纹相互作用的有限元模型,得到不同裂纹附近应力分布和开裂程度,分析了这2种裂纹之间的相互影响,结果表明:表面裂纹对界面裂纹影响较大,而界面裂纹对表面裂纹影响较小;氧化层几何参数以及材料参数对2种裂纹演变的影响研究结果表明:氧化层正弦幅值和厚度主要影响界面裂纹,在热载荷下,氧化层越粗糙,界面裂纹扩展速度越快。黏结层弹性模量主要影响界面裂纹扩展程度,而陶瓷层弹性模量主要影响表面裂纹扩展程度,对界面裂纹间接地产生较大影响。 相似文献
122.
《中国航空学报》2021,34(6):188-198
Micro-forging (MF) is a novel surface modification technology which is capable of smoothening and strengthening the workpiece surface simultaneously. Based on analysis of the mechanism and energy conversion of micro-forging process, an electromagnetically driven micro-forging system is developed. To further grasp the kinetic characteristic of the equipment, a simulation model is established and its accuracy is verified. With the help of simulation and experimental results, we propose an input voltage optimization method, which drives the micro-forging head moving in a uniform and stable way. In this study, the influence of MF on surface integrity of Ti-6Al-4V (TC4) is firstly reported. Experimental results show that MF treatment reduces surface roughness (Ra) and increases micro-hardness by 48% and 11.8% at most, respectively. Besides, a compressive stress layer with an amplitude of −1000 MPa and a depth of 0.8 mm is observed. This study analyzes the performance and reveals the potential of micro-forging technology, which lays a solid foundation for expanding its application in TC4 surface modification. 相似文献
123.
飞机发动机叶片缺陷的差激励涡流传感器检测 总被引:1,自引:0,他引:1
针对某型号飞机发动机涡轮叶片上预制的微裂纹缺陷进行了检测研究.基于涡流检测技术设计并研制了一种尺寸小、灵敏度高的差激励探头,应用有限元分析软件开展了叶片微裂纹缺陷仿真分析.为了实现叶片的自动高效检测,设计并采用数控多自由度扫查台来控制采集过程,实现了对叶片表面裂纹缺陷的快速扫查检测.采集信号经过信号调理电路,A/D转换后输入计算机,完成信号的保存、处理和输出.通过对比实验结果与仿真结果发现,研制的差激励式涡流传感器可以有效地实现对叶片类零件表面微裂纹位置的判定,对涡轮叶片类零件微缺陷早期诊断评估具有一定的现实和借鉴意义. 相似文献
124.
《中国航空学报》2021,34(2):576-585
Creep feed profile grinding of the fir-tree blade root forms of single crystal nickel-based superalloy was conducted using microcrystalline alumina abrasive wheels in the present study. The grinding force and the surface quality in terms of surface topography, subsurface microstructure, microhardness and residual stress obtained under different grinding conditions were evaluated comparatively. Experimental results indicated that the grinding force was influenced significantly by the competing predominance between the grinding parameters and the cross-sectional root workpiece profile. In addition, the root workpiece surface, including the root peak and valley regions, was produced with the large difference in surface quality due to the nonuniform grinding loads along the root workpiece profile in normal section. Detailed results showed that the surface roughness, subsurface plastic deformation and work hardening level of the root valley region were higher by up to 25%, 20% and 7% in average than those obtained in the root peak region, respectively, in the current investigation. Finally, the superior parameters were recommended in the creep feed profile grinding of the fir-tree blade root forms. This study is helpful to provide industry guidance to optimize the machining process for the high-valued parts with complicated profiles. 相似文献
125.
Influence of lunar topography on simulated surface temperature 总被引:2,自引:0,他引:2
Meng Zhiguo Xu Yi Cai Zhanchuan Chen Shengbo Lian Yi Huang Hang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
The surface temperature of the Moon is one of the essential parameters for the lunar exploration, especially to evaluate the Moon thermophysical features. The distribution of the temperature is heavily influenced by the Moon topography, which, however, is rarely studied in the state-of-art surface temperature models. Therefore, this paper takes the Moon topography into account to improve the surface temperature model, Racca model. The main parameters, such as slopes along the longitude and latitude directions, are estimated with the topography data from Chang’E-1 satellite and the Horn algorithm. Then the effective solar illumination model is then constructed with the slopes and the relative position to the subsolar point. Finally, the temperature distribution over the Moon surface is obtained with the effective illumination model and the improved Racca model. The results indicate that the distribution of the temperature is very sensitive to the fluctuation of the Moon surface. The change of the surface temperature is up to 150 K in some places compared to the result without considering the topography. In addition, the variation of the surface temperature increases with the distance from the subsolar point and the elevation, along both latitude and longitude directions. Furthermore, the simulated surface temperature coincides well with the brightness temperature in 37 GHz observed by the microwave sounder onboard Chang’E-2 satellite. The corresponded emissivity map not only eliminates the influence of the topography, but also hints the inherent properties of the lunar regolith just below the surface. Last but not the least, the distribution of the permanently shadowed regions (PSRs) in the lunar pole area is also evaluated with the simulated surface temperature result. 相似文献
126.
低轨道航天器的表面充电模拟 总被引:1,自引:0,他引:1
为研究航天器表面材料在空间环境中的充电现象, 利用SPIS (Spacecraft Plasma Interaction System)模拟了航天器在低轨道等离子体环境中的表面充电情况, 通过对模拟结果进行分析并与实际观测进行比较, 可以看出模拟结果基本能够反映出不同性质材料之间的充电差别, 特别是导电材料与非导电材料之间的充电差别. 模拟得到的充电电位及充电时间与充电的一般理论计算结果符合较好, 且能够清晰反映出航天器运动中产生的冲击流及尾流的结构特征. 根据SPIS低轨道航天器表面充电模拟的特点, 认为SPIS的模拟结果是合理的. 相似文献
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130.
文章通过讨论n沟道CCD的物理结构以及两种CCD饱和弥散(弥散型饱和状态和表面型饱和状态)的差异,介绍了面阵CCD抗弥散技术,它通过改变垂直转移时序使普通CCD具有抗弥散功能。对采用该技术前后相机抗弥散的实际效果进行了对比,进一步研究了面阵CCD时序抗弥散所必需的表面型饱和高电平偏置电压测定方法、低电平电压偏置测定方法以及时序工作频率标定方法,给出了工程实现的具体途径。总结了时序抗弥散技术的优缺点,列出了该技术的使用范围和限制条件。 相似文献