Bioinspiration of the vein structure of dragonfly wings on its flight characteristics

Dragonflies have excellent flight characteristics, which are inextricably related to the characteristics of their wings. Their wings not only support a variety of loads during flight but also maintain high-efficiency flight characteristics. In this study, the forewing of a dragonfly (Pantala flavescens (Fabricius)) was used as a research object to explore the microstructure of the surface, cross section, and the vein distribution. Three-dimensional models of three different structures of the forewing vein, including an oval-shaped hollow tube, a circular hollow tube, and a circular solid tube, were established. Fluid dynamics analysis of these three forewing models under different angles of attack during gliding was carried out by FLUENT software, and subsequently, the influence of the dragonfly forewing vein structure on its flight characteristics was analyzed. The numerical simulation results indicated that the vein structure has a considerable influence on the lift, drag, and lift–drag ratio of the P. flavescens forewing. It was indicated that among the tested models, the forewing model with oval-shaped hollow tubular veins has better flight efficiency and aerodynamic characteristics. The results of this study may provide the basis for a novel bionic concept of flapping wing microaircraft design.     

Microstructure and material properties of hind wings of a bamboo weevil Cyrtotrachelus buqueti (Coleoptera: Curculionidae)

Wings of flying insects, as representative biomaterials, are composed of a flexible membrane and a stiff vein structure that are prone to bending and deformation under aerodynamic forces. Therefore, we must investigate the application value of insect wings in the field of engineering design from the perspective of bionics, which is a new challenge. In this study, we measured the mechanical properties of the hind wings of Cyrtotrachelus buqueti including “dried” and “fresh” samples. The wing membrane samples were prepared by carefully cutting the hind wings into 2.0 mm by 8.0 mm rectangular segments using a gauge. As the major wing veins are the main loading units under aerodynamic forces, we also separated them from the wings as a kind of investigative specimen. The wing membranes were adhered to a specially designed paper fixture and the mechanical properties of the wing veins and membranes were evaluated using a tensile testing machine. We observed the microstructure of the samples using a scanning electron microscope and accurately measured the thicknesses of desired the wing membranes and veins. The results show that there is a difference in the mechanical properties of the two samples. The elastic modulus and Poisson's ratios vary over the region in hind wing, so we can conclude that the wing membrane is an anisotropic and non‐uniform material.     

Analysis of color shift on butterfly wings by Fourier transform of images from atomic force microscopy

Butterfly wings have complex structure lending it several interesting properties. Coloration of the wing is one of the first things to encounter and the overall visual effect is in fact influenced by several factors. Chemical pigments set the base color of the wing, topographical structures on the wing scales cause color shift by interference and their arrangement into diffraction grating causes iridescence. The thin film interference can be attributed to microscopic ridges covering wing scales. Observation and calculation of the color shift on wings of Euploea mulciber species using Fourier transform of images obtained by atomic force microscopy is the focus of this article.     

Assembly modes of dragonfly wings

The assembly modes of dragonfly wings are observed through FEG-ESEM. Different from airplane wings, dragonfly wings are found to be assembled through smooth transition mode and global package mode. First, at the vein/membrane conjunctive site, the membrane is divided into upper and lower portions from the center layer and transited smoothly to the vein. Then the two portions pack the vein around and form the outer surface of the vein. Second, at the vein/spike conjunctive site, the vein and spike are connected smoothly into a triplet. Last, at the vein/membrane/spike conjunctive site, the membrane (i.e., the outer layer of the vein) transits smoothly to the spike, packs it around, and forms its outer layer. In short, the membrane looks like a closed coat packing the wing as a whole. The smooth transition mode and the global package mode are universal assembly modes in dragonfly wings. They provide us the references for better understanding of the functions of dragonfly wings and the bionic manufactures of the wings of flights with mini sizes.     

Functional morphology and structural characteristics of wings of the ladybird beetle,Coccinella septempunctata (L.)

In recent years, the surface morphology and microstructure of ladybird (Coccinella septempunctata) wings have been used to help design the flapping‐wing micro air vehicle (FWMAV). In this study, scanning electron microscopy (SEM) was used to verify the functional roles of the ladybird forewing and hindwing. Surface morphology and the cross‐sectional microstructure of the wings are presented. Detailed morphology of ladybird forewings was observed using atomic force microscopy (AFM) and the composition of the wings was characterized using Fourier transformed infrared spectroscopy (FTIR). The ladybird forewing may possess different performance characteristics than the beetle, Allomyrina dichotoma. Additionally, the circular holes in the forewing might be important for decreasing the weight of the forewing and to satisfy requirements of mechanical behavior. Microsc. Res. Tech. 79:550–556, 2016. © 2016 Wiley Periodicals, Inc.     

Microstructure and mechanical properties of sheep horn

The sheep horn presents outstanding mechanical properties of impact resistance and energy absorption, which suits the need of the vehicle bumper design, but the mechanism behind this phenomenon is less investigated. The microstructure and mechanical properties of the sheep horn of Small Tailed Han Sheep (Ovis aries) living in northeast China were investigated in this article. The effect of sampling position and orientation of the sheep horn sheath on mechanical properties were researched by tensile and compression tests. Meanwhile, the surface morphology and microstructure of the sheep horn were observed using scanning electron microscopy (SEM). The formation mechanism of the mechanical properties of the sheep horn was investigated by biological coupling analysis. The analytical results indicated that the outstanding mechanical properties of the sheep horn are determined by configuration, structure, surface morphology and material coupling elements. These biological coupling elements make the sheep horn possess super characteristics of crashworthiness and energy absorption through the internal coupling mechanism. We suppose that these findings would make a difference in vehicle bumper design. Microsc. Res. Tech. 79:664–674, 2016. © 2016 Wiley Periodicals, Inc.     

相似分析在结构仿生设计中的应用研究

指出了仿生相似分析内容和步骤,并对生物骨架与小型梁肋机翼结构进行了模糊相似评价,表明叶脉承力性能与小型梁肌机翼具有高的相似度;针对机翼结构设计要求,借鉴叶脉结构特征,设计了仿生型机翼结构.有限元分析表明,仿生型机翼具有更高的结构效能.     

Computational investigation of variation in wing aerodynamic load under effect of aeroelastic deformations

The evaluation of the variation in aerodynamic load on a wing under the effect of elastic deformations requires solving the problem of wing deformation when wings are subjected to distributed aerodynamic load. This paper presents the calculation of coupling the aeroelastic system for 3D wings. The aerodynamic problem was solved by the doublet–source method for 3D wings, with wing thickness considered. The problem of elastic deformation was solved by the finite element method for hollow 3D wings, with beams arranged inside. Results concerning aerodynamic load on the wing were considered input parameters for the calculation concerning the problem of wing deformation, and those about the deformed wing geometry were deemed input parameters for the calculation regarding the problem of wing aerodynamics for the second calculation. The calculations concerning these problems were repeated until the wing twist angle converged. Analyses and comparisons were performed on the distributions of aerodynamic loads on the rigid and deformed wings to examine the change of the aerodynamic load depending on the structure (aerodynamic loads being functions of the external geometry of the wing, the incidence angle, and the velocity at infinity are solutions of the pure aerodynamic problem). Results regarding wing twists and stress distributions for hollow wings with and without beams inside were presented to assess the cause of changes in aerodynamic load and wing static durability. Aeroelastic calculations were formulated with different velocities at infinity to indicate the need for a suitable structural solution when the aerodynamic load is expected to reach a high value.     

The role of casting porosity in fatigue properties of Al−Si 319 lost foam cast alloy

The tensile, fracture toughness and fatigue properties of Al−Si 319 lost-foam-cast alloy were determined at room temperature. The fatigue properties of this alloy were also determined at 150°C. Fatigue cracks were always initiated at the largest casting pore. Initial pore sizes were measured using a scanning electron microscope. Surface replication showed that majority of the fatigue life was spent in fatigue crack propagation and permitted the estimation of the constants in the Paris power law and the threshold stress intensity factor (ΔK _th ). The role of internal casting porosity was quantified using a linear elastic fracture mechanics (LEFM) model for fatigue crack growth. The predicted lives agreed with the measured values within a factor of two.     

某超临界锅炉吹灰器罩壳内水冷壁管表面裂纹产生原因

某超临界锅炉运行1.2万h后,在其吹灰器罩壳内水冷壁管背火面发现密集横向裂纹.通过资料调研、材料成分检验以及开裂部位显微组织、断口形貌和拉伸性能分析,研究了水冷壁管表面裂纹产生的原因.结果表明:水冷壁管材料正常,其背火面管外壁裂纹为热疲劳裂纹;吹灰器套管外径偏大顶在吹灰孔周边水冷壁管上,温度偏低导致吹灰蒸汽带水,水沿着...     

柴油机曲轴三维有限元可靠性分析

运用有限元软件分析了柴油机曲轴在交变弯曲载荷下的应力分布和疲劳强度。以最大爆发压力工况和最大拉力工况作为计算工况,计算了曲轴的应力分布;对最大爆发压力工况和最大拉力工况下的应力进行等效转化疲劳应力计算;最后采用安全系数判断了曲轴的疲劳强度。     

High-temperature mechanical properties investigation of Al-6.5 % Cu gas tungsten arc welds made with scandium modified 2319 filler

The present study has investigated the influence of scandium additions on the structure and mechanical properties of AA2219 gas tungsten arc (GTA) weldments. Controlled amounts of scandium modified AA2319 fillers were introduced into the molten pool of AA2219 by predeposited cast inserts under different welding conditions in GTA welding. Full penetration GTA welds were prepared using alternating current. It was observed that grain size decreased with increasing amounts of scandium and gradual transformation from columnar to equiaxed grain morphology. The observed grain refinement was shown to result in an appreciable increase in fusion zone hardness, strength, and ductility. Room temperature hardness and tensile properties at different temperatures (room temperature, 100, 150, 200 and 250 °C) of weldments in the as-welded condition were observed and correlated with microstructure. The results show that the welds subjected to post-weld aging treatment have displayed superior hardness and tensile strength.     

压电双晶片驱动的仿生柔性扑翼机构研究

分析了昆虫的翅膀-胸部运动系统,并以此为基础,仿生设计出压电双晶片驱动,柔性双摇杆机构放大位移并带动仿生翅拍动的扑翼系统.分析了压电双晶片的工作原理,讨论了柔性四杆机构的自由度和运动学,并对整个系统的准静力学进行探讨,以确定能否产生足够的力克服空气阻尼.仿真和实验结果表明,通过柔性机构放大压电双晶片位移,能实现仿生翅所需运动,同时进一步的优化设计将有助于改进扑翼机构的运动性能.     

往复式甲烷压缩机曲轴断裂原因

某往复式甲烷压缩机曲轴在运行过程中发生断裂,通过断口宏观和微观形貌观察、化学成分分析、显微组织观察和力学性能测试等方法,研究了曲轴断裂的原因。结果表明:曲轴发生了扭转疲劳断裂;在交变扭转应力的作用下,曲轴主轴颈不规则且粗糙的过渡圆角和油孔附近粗糙的机械加工痕迹处产生应力集中,导致微裂纹萌生;组织中严重的带状回火屈氏体、大小不均匀的晶粒以及非金属夹杂物导致曲轴的力学性能变差,加速了疲劳裂纹的扩展;建议严格控制曲轴的热处理和制造工艺,优化曲轴结构设计,防止类似事故的再次发生。     

基于昆虫翅膀运动机理的仿昆拍式翅研究

仿昆拍式翅是以昆虫翅膀运动机理为基础的仿生设计。对仿昆拍式翅翅膀进行了研究，提出几种控制翅膀空气流动的方法以及升力估算方法，并对翅膀的设计和制造等问题进行详细探讨。简要分析了仿昆拍式翅的运动机构和驱动系统，设计出了一种新颖的小型仿昆拍式翅。     

一种柔性微型扑翼设计及其气动力特性的试验研究

微型扑翼机以其优良的机动性、低噪音、低成本、执行任务的多功能性以及在现代高科技局部战争中的潜在应用价值而得到各科技先进国家的重视,投入了大量精力开展研究工作。在我国也已经初步开展对微型扑翼机研究。但由于与微型扑翼飞行相关的低雷诺数空气动力学研究还处于萌芽阶段,对微型扑翼的设计研究工作尚无可供指导的成熟理论和借鉴的经验,目前微型扑翼的设计研究基本上是以试验为主。本文参照动物的扑翼飞行实例和固定翼飞行器机翼设计的经验,在对扑翼飞行基本原理分析研究的基础上,设计制作了一种微型扑翼及扑翼的驱动机构,采用直流电动机作为动力,通过调节驱动电压来控制扑动的频率。并对该微型扑翼进行了空气动力特性试验,得到了微型扑翼的空气动力特性,并从中得出了影响扑动升力的一些因素。实验结果表明,具有柔性翼面的扑翼,其产生的升力和推力较高而且比较稳定。     

弹簧钩断裂失效分析

弹簧在使用过程中,要承受交变应力的作用,故而对材料疲劳强度有着很高的要求。不当的热处理和加工工艺会严重降低弹簧的疲劳强度,从而使弹簧过早地产生疲劳断裂失效。本文使用扫描电子显微镜对弹簧断口进行观察分析,找出断裂原因,为改进工艺提供依据。     

Effect of particle size, forging and ageing on the mechanical fatigue characteristics of Al6082/SiCp metal matrix composites

Addition of inexpensive silicon carbide particulates (SiC_p) in the aluminium alloy matrix results in materials with properties non-obtainable in monolithic materials. The forging process results in improved properties as well as forms a shape of the final product. The age-hardening processes accelerate the coarse hardening process of the composites and improve strength and ductility. The size, morphology and volume fraction are the key controlling factors that control the plasticity and the thermal residual stresses in the matrix and thereby it’s mechanical and fatigue properties. This research paper focuses on the effect of particle size, forging and ageing on the mechanical and fatigue properties of the cast, forged and age-hardened aluminium 6082 (AI6082) reinforced with SiC_p. Al6082 reinforced with three different particle sizes of SiC_p (average particles size of 22, 12 and 3 µm) in the forged and ageing conditions were studied. The samples were characterised by optical microscopy, hardness, tensile and fatigue tests. The forged microstructure shows a more uniform distribution of SiC_p in the aluminium matrix. The addition of SiC_p results in improved tensile strength, yield strength and elastic constants of the composites with reduction in ductility. It also increases the fatigue strength of the composites by increasing the number of cycles required for fatigue failure of the composites for the given value of stress. The results also show considerable improvements in mechanical fatigue properties due to forging and ageing heat treatment of the metal matrix composites     

Morphology and mechanical properties of the dorsal bony plates in the Chinese sturgeon (Acipenser sinensis)

The morphology, composition, and mechanical properties of the dorsal bony plates in the Chinese sturgeon (Acipenser sinensis) were determined in this study. Scanning electron microscopy images of the bony plates revealed a ridge‐like shape similar to that of traditional Chinese architecture and displayed hierarchical microstructures whose the degree of mineralization decreased from the surface layer to the internal layer. Moreover, the crests in the central part of the bony plates displayed porous characteristics. Composition analysis of the bony plates revealed that they were primarily composed of Ca, P, O, and C, demonstrating that hydroxyapatite was the main constituent. Mechanical experiments including nanoindentation, penetration, and tension tests confirmed that the bony plates have excellent mechanical properties and present high specific tensile strength that is comparable to that of 304 stainless steel. This study may provide a new bionic design template for lightweight and high‐strength body armor.