共查询到20条相似文献,搜索用时 62 毫秒
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针对KDP晶体材料在离子束加工时晶体表面粗糙度变化情况进行了研究,研究了束电压和束电流的大小对KDP晶体表面粗糙度的影响,采用PSD功率谱分析方法探究了KDP晶体在离子束加工前后表面粗糙度频域分布及其演变情况,研究结果表明KDP晶体表面粗糙度的变化不仅与加工工艺参数有关还与材料本身性质有关,在采用较大入射角时可以使晶体表面的高频段误差得到改善. 相似文献
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为了获得不同气氛对紫外激光加工非晶合金盲孔的质量和效率的影响,采用波长355nm的纳秒激光对Zr–Cu非晶合金进行同心圆式旋切法盲孔加工试验,利用光学显微镜、扫描电镜、激光共聚焦显微镜等仪器对盲孔的显微形貌、粗糙度和加工效率进行了测试。结果表明,气氛的压力和种类影响着盲孔的底面形貌、加工质量和效率。气氛压力越小,盲孔底面粗糙度越低,材料的去除效率越高;相对于氮气、空气中的加工,氧气中表面粗糙度最小,且材料去除率最高。另外,加工表面未出现晶化现象,说明在一定激光参数下紫外纳秒激光可以实现非晶态合金的无晶化加工。 相似文献
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通过对TC21钛合金进行高速铣削加工试验,测量不同切削参数下的表面粗糙度.采用正交方法来安排试验和极差分析法对实验数据处理,分析了不同切削参数对粗糙度的影响.其中对TC21钛合金表面粗糙度影响最为显著的因素是每齿进给量,其次为切削深度和切削速率,最后为切削宽度.通过对粗糙度影响机理分析在加工中宜采用较小的进给量和切削深度、较大的切削速率和切削宽度. 相似文献
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为了改善高体积比铝基SiC复合材料的可加工性,提高加工效率,本文对高体积比铝基SiC复合材料进行了平面铣磨加工试验研究.试验结果表明,高体积比铝基SiC复合材料在铣磨加工中主要表现为脆性材料的特性,电镀金刚石砂轮在磨削过程中不会出现磨屑粘附现象.SiC颗粒的破损程度是影响表面粗糙度的主要因素,并且在相同磨削参数和条件的情况下随着颗粒的破损程度、砂轮粒度的增大和进给速度vf的降低,磨削表面的粗糙度值会逐渐减小.在给定其他试验参数的情况下,120#的φ8mm电镀砂轮适合进行粗磨,并且磨削的材料去除率能够达到2400mm3/min,同时进给抗力Fz小于25N,磨宽抗力Fx和磨深抗力Fy小于15N.使用230#的φ8mm电镀砂轮进行精磨能够保证表面形成率达到6400mm2/min,并使表面粗糙度优于Ra0.4μm. 相似文献
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《航空精密制造技术》2018,(6)
基于硬脆性材料加工机理分析了其微结构磨削表面精度与磨削工艺的关系,利用压痕法研究硬脆性材料加工的脆塑转变临界条件,在此基础上结合最大切屑厚度h模型及表面粗糙度Ra模型初步确定了磨削加工工艺参数范围。分析了切削速度与工件进给速度对表面粗糙度的影响机制和规律,并针对石英玻璃进行了磨削实验。研究结果表明,在延性域磨削条件下可获得磨削后表面粗糙度为55nm的高质量表面,为硬脆性材料微结构延性域临界磨削条件研究提供了理论参考与试验依据。 相似文献
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有翼高超声速再入飞行器气动设计难点问题 总被引:2,自引:1,他引:2
有翼高超声速再入飞行器是近年来的研究热点,气动设计是飞行器设计的关键。为了更清楚地认识有翼高超声速再入飞行器气动设计的难点问题,对有翼高超声速再入飞行器的发展、优势及总体任务剖面进行了介绍,从5个方面详细介绍了该类飞行器气动设计的难点问题,包括多约束复杂面对称气动布局设计、高温真实气体效应对气动特性影响、天地差异与天地换算方法、反作用控制系统(RCS)喷流干扰对气动特性的影响以及气动数据不确定度等,简要阐明了这些难点问题对总体设计的重要性以及初步的解决思路,为有翼高超声速再入飞行器气动设计提供了一些参考。 相似文献
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LUO Cheng LIU Hua YANG Jia-ling LIU Kai-xin 《中国航空学报》2007,20(3):230-235
Crashworthiness requirement of fuel tanks is one of the important requirements in helicopter designs. The relations among the protection frame, textile layer and rubber layer of the fuel tank are introduced. Two appropriate FE models are established, one is for an uncovered helicopter fuel tank without protection frame, and the other is for fuel tank with protection frame. The dynamic responses of the two types of fuel tanks impinging on the ground with velocities of 17.3 m/s are numerically simulated for the purpose of analyzing energy-absorbing capabilities of the textile layer and protection frame. The feasibility of the current crashworthiness design of the fuel tank is examined though comparing the dynamic response behaviors of the two fuel tanks. 相似文献
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The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow 总被引:1,自引:0,他引:1
This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig.Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine.Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air.Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows(Re up to 5×106 and Rez up to 2×105).Two different builds have been tested.The most significant difference between these two build configurations is the size of the annular gap between the(non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method.The velocity measurements were made using a two component,LDA system.The heat transfer results from the discs show differences between the two builds.This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity.There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig.For the narrow annular gap,there is an increase of non-dimensional tangential velocity V/Ωr with radial location to solid body rotation V/Ωr=1.For the wider annular gap,the non-dimensional velocities show a decrease with radial location to solid body rotation. 相似文献
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波音公司面临着来自空客公司的巨大挑战,企业战略性创新才是公司成功的关键。为此波音公司的全部战略性研究集中在扩大产品的差异性上,体现在3个方面:电子化(e-Enabled)运营环境、整体复合材料机身部件的制造技术和支持波音787客机的全球协同环境(GCE)。 相似文献
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临近空间飞行器测控与信息传输系统频段选择 总被引:7,自引:0,他引:7
临近空间飞行器是高性能信息化武器平台,测控(TT&;C)与信息传输系统是其信息保障的核心,而选择合理、可行的频段是展开系统设计的前提和基础。频段选择影响到整个技术方案的制定,是一个需综合考虑、影响深远并具有战略意义的关键问题,从国际电联(ITU)国际标准、高速数传、接收信噪比(SNR)、“三抗”、超视距中继、黑障、雨衰以及设备研制成熟度8个方面全面、细致论证了近空间平台测控系统的频段选择问题,最终得出在视距链路中以Ka频段为宜,在超视距链路中以Ku/Ka双频段为宜的结论。 相似文献
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基于弯曲激波压缩系统的高超声速进气道反设计研究进展 总被引:3,自引:0,他引:3
总结了近十年来弯曲激波压缩研究的主要成果。提出了弯曲激波压缩系统的新概念,即利用特殊设计的楔形弯曲压缩面或空间弯曲压缩面,产生一系列与前缘弱激波相互交汇或叠加的压缩波系,从而使前缘激波弯曲,形成特殊的弯曲激波,它与波后的等熵压缩波来共同完成对气流的压缩。在此基础上,实现了由给定出口气动参数的超声速内流道反设计,实现了由给定压缩面压力分布和给定压缩面马赫数分布要求的型面反设计,实现了由给定激波波面的压缩型面反设计。研究证明,弯曲压缩面-弯曲激波压缩系统具有良好的综合气动性能,为高性能高超声速进气系统的气动设计提供了一种全新的设计方法。 相似文献
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Wu Xianyu Li Xiaoshan Ding Meng Liu Weidong Wang Zhenguo 《中国航空学报》2007,20(6):488-494
In order to investigate the effects of fuel injection distribution on the scramjet combustor performance, there are conducted three sets of test on a hydrocarbon fueled direct-connect scramjet test facility. The results of Test A, whose fuel injection is carried out with injectors located on the top-wall and the bottom-wall, show that the fuel injection with an appropriate close-front and centralized distribution would be of much help to optimize combustor performances. The results of Test B, whose fuel injection is performed at the optimal injection locations found in Test A, with a given equivalence ratio and different injection proportions for each injector, show that this injection mode is of little benefit to improve combustor performances. The results of Test C with a circumferential fuel injection distribution displaies the possibility of ameliorating combustor performance. By analyzing the effects of injection location parameters on combustor performances on the base of the data of Test C, it is clear that the injector location has strong coupled influences on combus- tor performances. In addition, an inner-force synthesis specific impulse is used to reduce the errors caused by the disturbance of fuel supply and working state of air heater while assessing combustor performances. 相似文献
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(高)超声速流动试验技术及研究进展 总被引:1,自引:1,他引:1
近年来,与高速飞行器相关的(高)超声速流动受到了极大的关注。这类流动所具有的非定常性、强梯度和可压缩性对试验方法和风洞设计技术提出了挑战。超声速纳米示踪平面激光散射(NPLS)技术是由作者所在团队研发的非接触光学测试技术。它能够以较高的空间分辨率来揭示超声速三维流场的一个瞬态剖面的时间解析的流动结构。介绍了NPLS技术以及基于NPLS开发的密度场测量、雷诺应力测量和气动光学波前测量等方法,并回顾了这些技术在超声速边界层、超声速混合层、超声速压缩拐角、激波/边界层相互作用和光学头罩绕流等流动中的应用,清晰地再现了边界层、混合层、激波等典型流场结构及其时空演化特性。另外,为了模拟和研究高空大气条件下边界层自然转捩和超声速混合层的转捩特性,介绍了高超声速静风洞、超-超混合层风洞的设计技术以及层流化喷管的设计方法。 相似文献
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Research on Auto-detection for Remainder Particles of Aerospace Relay Based on Wavelet Analysis 总被引:2,自引:0,他引:2
GAO Hong-liang ZHANG Hui WANG Shu-juan 《中国航空学报》2007,20(1):75-80
Aerospace relay is one kind of electronic components which is used widely in national defense system and aerospace system. The existence of remainder particles induces the reliability declining, which has become a severe problem in the development of aerospace relay. Traditional particle impact noise detection (PIND) method for remainder detection is ineffective for small particles, due to its low precision and involvement of subjective factors. An auto-detection method for PIND output signals is proposed in this paper, which is based on direct wavelet de-noising (DWD), cross-correlation analysis (CCA) and homo-filtering (HF), the method enhances the affectiv-ity of PIND test about the small particles. In the end, some practical PIND output signals are analysed, and the validity of this new method is proved. 相似文献