Analysis of tape spring hinges

In this paper, the performance of four different tape spring hinges are studied. The tape spring hinges consist of pairs of short-length hardened-steel tape springs side by side but mounted in different ways, and can be used to fold and deploy structural elements on spacecraft. Behaviour of a tape spring subject to two- and three-dimensional folds is investigated by both analytical and non-linear finite element methods. The moment–rotation profiles of the hinges are obtained experimentally. It is observed that two hinge configurations yield negative moments in their moment–rotation profiles during deployment. The results of finite element analysis are compared with the experimental measurements, and are in good agreement.     

Calculative and experimental study of the CFRP tape spring

A tape spring is a thin-walled, straight strip of material with curved cross-section, and the current trend is towards tape springs made of carbon fibre reinforced plastic (CFRP). In this paper, performance of the CFRP tape spring was studied and its bending moment’s calculative formula during opposite-sense bending process was derivated, also, the theoretical formula’s accuracy was assessed by means of detailed, non-linear finite-element analysis. Subsequently, a CFRP tape spring was practical designed and manufactured through twiningmoulding workmanship, and some experiments were conducted to study its bending characters, verifying the validity of the theoretical analysis and finite element simulation perfectly.     

某带罩反射面天线刚强度性能试验设计与验证

文中以某带罩反射面天线为研究对象,设计了模拟复杂环境载荷的曲面天线刚强度性能试验,通过风洞试验验证了设计试验的可行性,为电子装备的安全服役提供保障.文中重点讨论了复杂曲面天线模拟风载的近似加载方式和刚强度性能试验分析方法.最后,对比了模拟风载和风洞试验形变测试结果,发现两种试验方法的最大误差在6％以下,证明了实验室模拟...     

Vibration analysis of multi-supported curved panel using the periodic structure approach

This papers deals with the radial vibration of a row of cylindrical panels of finite length using the concept of wave propagation in periodic structures. For this study, the structure is considered as an assemblage of a number of identical cylindrically curved panels each of which will be referred to as a periodic element. For a given geometry dispersion curves of the propagation constant versus (non-dimensional) natural frequency have been drawn corresponding to the circumferential wave propagation. New conclusions that have emerged from this study are as follows. It is shown that by a proper choice of the periodic element the bounding frequencies and the corresponding modes in all the propagation bands can be determined. These have been shown to correspond to a single curved panel with all its edges simply supported. It is noted that there are no attenuation gaps in the entire frequency spectrum beyond the lowest bounding frequency. This is a unique feature of circumferential wave propagation around circular cylindrical shells and panels, as opposed to the wave propagation of periodically supported beams and rectangular panels without curvature. The natural frequency corresponding to every circumferential mode of the complete shell has been identified on the propagation constant curve. It has been observed that the natural frequencies of a cylindrically curved panel of a given curvature and length but of different circumferential arc length (corresponding to different angles subtended at the centre of any circular cross-section) may also be identified on the same propagation constant curve. Finally, it is shown that the same propagation constant curve may also be used to determine all the natural frequencies of a finite row of curved panels with the extreme edges simply supported. Wherever possible the numerical results have been compared with those obtained independently from finite element analysis and/or results available in the literature. Flutter analysis of multi-span curved panels using a wave approach is the ultimate objective of this work.     

高精度反射器面板精密成形若干关键技术研究

高精度反射器是现代通讯和_军事技术中的重要装备，反射器面板型面精度要求在10^-2mm量级，非常规工艺所能达到。基于点阵钉模、真空负压、蜂窝夹层原理的精密成形技术是制造高精度反射面板的一项新技术，介绍了其原理和方法。采用开缝和开槽应力松弛技术实现了双曲度不可展曲面面板的精密成形，满足了大型高精度反射器精度指标要求。工程应用表明，采用该工艺方法制造的反射面板重量轻、精度高、型面稳定可靠。     

变截面螺旋曲面的解析几何建模与CAD绘图

扫描变换法和路径拉伸法通常用于螺旋弹簧的近似造型,通过分析比较,指出了两种方法的不足之处.运用解析几何方法,研究了圆截面螺旋曲面的建模方法,并建立了各种截面形状的螺旋曲面通用解析表达式.同时,进一步研究了变截面螺旋曲面的形成与建模方法,并在AutoCAD中给出了基于VisualLISP的各种截面形状螺旋面的CAD绘图技巧.结果表明,此建模方法能大大提高螺旋曲面造型的精确度.     

Analysis of label position stabilization methods on automatic packaging machines

The features of different methods for the automatic assembly of components on two tape devices have been considered. The solution of this problems makes it possible to align the label on the cover tape with a molded container made of a carrier tape on automatic form–fill–seal packaging machines. It has been shown that the adjustable tape electric drive that tracks positions of marks on the cover material using a photosensor that makes it possible to ensure the steady positioning of the label on the molded container under changing properties of the cover material and technological process parameters.     

一种用于曲面快速测量的激光片光源的研究

与快速成形技术有关的自由曲面快速反求工程中,测绘曲面所用的被称为光刀或片光的细长光条的质量是至关重要的。介绍一种应用柱面反射镜单向扩展光束形成激光片光的方法,并根据常用Ｈｅ－Ｎｅ激光为高斯光束的特性,应用长焦距透镜压缩其发散角,使激光片光具有很大焦深。激光光强的高斯分布使光刀宽度的中心具有极大值,使得片光的质量具有优良的特性,非常容易实现,并有利于摄像机采集。介绍了这种片光源的工作原理、片光的性能     

某星载反射面天线结构设计

反射面天线结构是天线电气性能实现的载体和保障。文中详细阐述了某星载反射面天线的结构设计要点,重点论述了碳纤维复合材料反射面的具体结构形式和反射面及背筋的详细结构设计。建立了天线的有限元模型,进行了模态分析、正弦振动仿真分析、热变形分析。仿真分析和振动试验结果表明：该天线有足够的刚强度,满足设计要求。研究结果可以为星载反射面天线结构设计提供工程参考。     

Failure Mechanisms of Advanced Metal Evaporated Tape in an Advanced Linear Tape Drive

Demand for increased data storage has resulted in the development of various types of magnetic tape. To achieve higher recording density, tape manufacturers are developing thin-film tapes, such as advanced metal evaporated (AME) tape, for use in linear tape drives. The structure of AME tape is fundamentally different from metal particulate (MP) tape. The goal of this study was to determine the methods and mechanisms associated with failure of AME tapes as well as to investigate the effect of tape cupping and initial edge quality on tape durability in an advanced linear tape drive. It is shown that AME tape exhibits a slightly lower coefficient of friction than the MP. The negatively cupped AME tape demonstrated a greater value of lateral tape motion peak-to-peak amplitude than both of the positively cupped AME samples as well as the MP tape sample. It was found that poor initial tape edge condition plays a large role in debris generation. For these reasons, positively cupped AME tapes with good initial relative edge contour are recommended for use in linear tape drives. The dominant mechanism of failure for the AME samples is adhesive wear resulting in removal of the DLC overcoats and sublayers.

     

Determination of the reflector type from an image reconstructed using echo signals measured with ultrasonic antenna arrays

The application of the digital image focusing (DFA) method to the determination of the types of detected reflectors is considered. For this purpose two antenna arrays (AAs) are used, which are placed on opposite sides of the reflector and using which echo signals are recorded in three acoustic channels in the double-scanning mode. The first and second acoustic channels transmit and receive echo signals using the first and second AA, respectively, and the third channel is tuned so that the first AA transmits pulses and the second AA receives echo signals. Using signals in each channel, many partial images can be reconstructed in a common coordinate system according to different acoustic schemes with allowance for both multiple reflections from irregular boundaries of a tested object and effects of transformation of the wave types. Combining partial images makes it possible to obtain a high-quality image, in which the entire boundary of the reflector is seen and using which an attempt to automate the procedure of evaluating the reflector size and determining its type was made. Such an approach allows one to reduce the subjective influence of an operator on the testing results. It is shown that in order to increase the image resolution, the spectrum of echo signals can be extrapolated by the spectrum splitting method jointly with the construction of an AR model of their spectrum. The results of model experiments that confirm the possibility of determining the reflector type are presented.     

Measurement and Origin of Tape Edge Damage in a Linear Tape Drive

Integrity of the magnetic tape edge is the key to maintaining high performance of modern tape drives. Damage to the tape edge under normal drive operation results in the change in tape dimensions and debris generation, both leading to degradation in the reproduction of the recorded signal. The objective of the present study is to develop a methodology for evaluation of tape edge quality and to apply the methodology to monitor tape edge degradation under normal drive operation. Optical microscopy, atomic force microscopy and scanning electron microscopy are employed to study and quantify the quality of the tape edge. AFM measure-ments were made on both individual tape layers and the tape reel. An edge quality measurement technique is used to quantify the damage to tape edge. A technique for the tape lateral motion measurement is used to study the effect of continuous sliding on tape guiding. A lateral force measurement technique is developed to measure the force exerted by the tape edge on the guide flange. The effect of normal drive operation on tape edge quality and on tape guiding in a linear tape drive is studied. It is shown that two edges of a factory-slit tape are imperfect and different, with cracking of the magnetic coating occurring at one edge. Under normal drive operation, one edge experiences more wear with larger amount of debris produced. This larger debris generation occurs on the edge with cracks developed during manufacturing. A possible mechanism of tape edge wear under normal drive operation is proposed.     

重型车车架组合结构的有限元分析

运用组合结构的有限元方法,建立了某重型载重车车架的双层主副梁、横檗、支架、板簧及螺栓等联接特征的仿真模型,进行了车架组合结构在静载条件下的位移场、应力场及动力学特性的模拟计算。计算和试验表明,利用组合结构的有限元方法可以作为结构设计的有效判据。     

多交叉曲梁簧片柔性铰链的力学建模与性能分析

针对直梁型多交叉簧片柔性铰链难以兼顾大转角、低刚度的问题,设计了一种多交叉曲梁簧片柔性铰链。采用圆弧曲梁簧片减小变形应力和转动刚度,在纯转矩驱动条件下具有高转动精度和大转角行程。推导了圆弧曲梁簧片的变形应力计算方程,建立了柔性铰链的大变形力学分析模型,并通过转动刚度实验和变形应力仿真计算验证了理论模型的准确性。进一步分析了半径系数、簧片曲率和位形角等设计变量对柔性铰链驱动转矩和变形应力的影响关系,提出了同时减小转动刚度和变形应力的设计方案,确定了使柔性铰链获得零刚度特性和负刚度特性的设计变量组合。所设计的柔性铰链结构及其性能分析结果可为新型大行程柔性铰链的设计提供参考。     

Some features of echo signals of longitudinal waves from flat-bottom reflectors in the far-field zone of a normal transceiver

Features of reflection of longitudinal elastic waves from flat rectangular, elliptic, and segmental reflectors (flaws) placed in the far-field zone of a normal transceiver are investigated for continuous (quasi-monochromatic) and pulsed transmission-reception modes. It is shown that, as the dimensions of the reflector increase, the echo-signal amplitude oscillates and approaches a value determined by the limiting shape of this type of reflector. It has been established that, for the reflector models considered, the character of an echo signal is determined by the value of the generalized parameter depending on the distance to the reflectors, their characteristic dimensions, and the wave number of the acoustic wave.     

基于MSC软件的11米天线结构分析

阐述了天线进行结构力学分析的必要性,给出了基于MSC软件,天线结构分析的一般步骤,以及在分析中出现奇异点时的解决方法。最后,得出了天线在不同姿态时变形的主要数据,并经过实际测试,满足使用要求,验证了分析结果的正确性。     

Selection of a conventional point of acoustic-wave reflection from a flat compact flaw in the far-field zone of a normal transceiver

The influence of the selection of a conventional point on a flat flaw of circular segmental shape on its directivity characteristic as a reflector is studied. The independence of the numerical value of this characteristic at a constant azimuthal angle of direction to the reflection point is shown. Examples of calculations of the directivity characteristic for a segmental reflector are presented. Recommendations for selecting the conventional reflection point and the points of emission and reception for transducers with piezoelectric plates whose shapes differ from typical ones are given.     

Trajectory generation and dynamic control of planar biped robots with curved soles

This paper proposes a locomotion pattern and a control method for biped robots with curved soles. First, since the contact point of a supporting leg may arbitrarily move back and forth on the ground, we derived the desired trajectory from a model called the Moving Inverted Pendulum Model (MIPM) where the Zero Moment Point (ZMP) exists at the supporting point and can be moved intentionally. Secondly, a biped robot with curved soles is an under-actuated system since the supporting point contacting with a point on the ground has no actuator during the single supporting phase. Therefore, this paper proposes a computed-torque control for this under-actuated system using decoupled dynamic equations. A series of computer simulations with a 7-DOF biped robot with curved soles shows that the proposed walking pattern and control method are effective and allow the biped robot to walk fast and stably, and move more like human beings. Also, it is shown that the curved sole shape has superior energy consumption compared to flat soles, and greater efficiency in ascending and descending the stairs.     

Investigation of roller interactions with flexible tape medium

Lateral tape displacement and roller axial runout are measured on an experimental tape transport. The effect of roller axial runout on lateral displacement of tape is investigated. Tape lateral displacement is found to be generated at the roller surface, and is observed to be correlated to roller axial runout. A number of typical roller types are investigated to determine the mechanism causing lateral tape displacement. Edge contact and friction are each shown to play a role in the creation of lateral tape displacement in the tape path.     

Application of 3D coherent processing in ultrasonic testing

A 3D variant of the coherent method of projection in the spectral space (PSS) for obtaining images of reflectors on the basis of measured echo signals is considered. Its application allows recon-struction of reflector images with a high frontal resolution in both the main plane of an ultrasonic transducer and an additional plane. The application of the PSS method is especially efficient when a reflector is far from the receiving aperture. In this case, it is possible to increase the signal-to-noise ratio by more than 12 dB and a tenfold increase in the frontal resolution can sometimes be attained as compared to the 2D layer-by-layer variant of the PSS method. Examples of the application of this method during reconstruction of reflector images in a specimen of the wall of a chemical reactor, in the case of multiple reflections from the walls of a welded T-branch with an overlaid plate (WTP), and when testing large-diameter studs and supports of the divertor, which is manufactured as part of the work on the thermonuclear reactor (ITER) project, are presented. The efficiency of applying the 3D variant of the PSS method for testing at large depths is shown.