Applied Mechanics and Materials Vol. 461

Abstract: This paper summarizes a TEDx Talk that the European physics professor Ille C. Gebeshuber, who has been living in South East Asia for nearly five years now, gave to a live audience of 800 in Kuala Lumpur, Malaysia, in July 2012. A similar talk is also given as an invited lecture at the 4^th International Conference of Bionic Engineering in China in August 2013. The talk highlights the importance of news ways of doing science and of doing engineering that are needed to successfully address the major challenges humankind is currently facing, and how a generalistic approach synergistically combining Eastern and Western thinking might help in this respect. Biomimetics is stressed as an integrated, generalist way of learning from living nature, and as best practice example for developing new approaches that are based on understanding rather than learning by heart, with memory, reason and imagination as pillars, bridging fields of specialization and of education and thereby blending the knowledge of single isolated scientists and specialist scientist networks to a wisdom of the whole, powerful enough to help us successfully address our major problems.

Abstract: In this paper, the methods of bionic flight control system for PAV are researched and a simplified model contained bionic-sensor component is designed. Based on some idealized assumptions, a simulation is accomplished. The results demonstrated that it is feasible to develop a bionic flight control system and the system is able to provide a compact and low-priced design scheme for PAV.

Abstract: nsects in nature have outstanding flight skills, and the research on their flight kinematics and dynamics can provide inspiration for the design of flapping-wing aircraft. An experiment was designed to study the mechanism and reveal the dynamics when Otidognathus Davidis Fair (ODF) flies. In this paper, two flight parameters, including lift and thrust of ODF, were tested using the insect flight test system, while ODF was under constraint on plexiglass. Experimental results showed that frequency of the wing was about, and the maximum of lift and thrust can reach 95mN and 300mN, respectively. With the increase of the weight, both of the peak values of lift and thrust change very little. Furthermore, their tendencies are of the same.

Abstract: The fixed-wing aircrafts rely mainly on thrust generated by engine and lift produced by wings to keep flying, so there are strict requirements on their speeds and attack angles. The flappers can hover freely in the air like insects because they have different flight principles and forms compared with fixed-wing aircrafts. The flapper is consisted of the flapping-wing, the flapping-wing mechanism and the drive. The flapping-wing is used to generate lifts and thrusts while the wing mechanism and the drive provide main power to the flapping wing. Traditionally, flapper uses rigid wing to provide lift and thrust force. The researches of the insect flapping wing process indicate insect wings would produce certain flexibility and umbrella effect in this process. Based on the above research, the compression molding is employed to manufacture the bionic flexible wing in this article. Whats more, in order to imitate the umbrella deformations at the wing tips, IPMC (Ionic Polymer Metal-Composites) are fixed on the flexible wings to achieve umbrella deformations.

Abstract: The structure of corn stubble was complex and closely combined with the soil, so dig location and root-soil separation are the urgent problem of the manufacturing of corn stubble harvesting machinery. This paper mainly focuses on investigating the interaction principles of corn stubble and soil which by the UU triaxial compression tests. Compared the shear strength of three different types of corn root-soil complexes (vertical root, horizontal root, complex root) and pure soil, and analyzed three important factors affecting the root-soil complex shear strength, it was shown that the presence of corn fibrous root can enhance the soil shear strength and different with their layout types. It will provide a theoretical basis for the design of bionic agricultural tillage components for root- soil separation.

Abstract: Different ground environments call for corresponding foot mechanism design. As for unstructured terrain, through the analysis of goat hooves structure, a robot foot mechanism simulating the goat hooves is designed in our research. According to screw theory and generalized Kutzbach-Grübler mobility criterion, degree of freedom of the bionic goat hoof mechanism is calculated. Then forward kinematics is built based on mechanism geometry. Motion simulation is carried out to verify the algorithms of forward kinematics.

Abstract: Flying bird has gradually formed airworthy structures e.g. streamlined shape and hollow shaft of feather to improve flying performance by millions of years natural selection. As typical property of flight feather, herringbone-type riblets can be observed along the shaft of each feather, which caused by perfect alignment of barbs. Why bird feather have such herringbone-type riblets has not been extensively discussed until now. In this paper, microstructures of secondary feathers are investigated through SEM photo of various birds involving adult pigeons, wild goose and magpie. Their structural parameters of herringbone riblets of secondary flight feather are statistically obtained. Based on quantitative analysis of feathers structure, one novel biomimetic herringbone riblets with narrow smooth edge are proposed to reduce surface drag. In comparison with traditional microgroove riblets and other drag reduction structures, the drag reduction rate of the proposed biomimetic herringbone riblets is experimentally clarified up to 15%, much higher than others. Moreover, the drag reduction mechanism of herringbone riblets are also confirmed and exploited by CFD.

Abstract: Caudal fin has fascinated researchers for decades for their great role in fish swimming, and researchers have developed lots of designs of caudal fin to achieve high efficiency and speed propulsion. This paper presents a novel design of variable area caudal fin. A “window” which can rotate freely is designed in the middle of the fin and it can be opened by the fluid force and closed by a simple mechanism. By closing or opening the “window”, the caudal fin can vary its area dynamically in the out-stroke and in-stroke in its motion. Four modes to control the “window” in the pitching motion is then presented, their hydrodynamic forces including thrust force, lateral force and lift force are studied. It is found out that the variable area fin model can indeed improve the propulsion performance compared with the traditional fin, and the mode of closing the “window” in the out-stroke and opening the “window” in the in-stroke can generate the largest thrust force for our model than the other modes. Moreover, experiments about various kinematic parameters with different modes are conducted, it is found out different modes behave quite different with same pitching frequency and amplitude, and its propulsive performance is highly depend on the kinematic parameters. The variable area caudal fin model casts an inspiration for the novel design of underwater propulsive mechanism and the results will be useful for the propulsion study of underwater bio-mimetic vehicles.

Abstract: The ostrich foot toenail plays a crucial role in the process of ostrich foot traveling on sand. 3D laser scanner was used to measure the three-dimensional point clouds of ostrich foot toenail surface morphology, and the three-dimensional model of ostrich foot toenail was reconstructed by using reverse engineering technology. The finite element analysis in the interactions between ostrich foot toenail and sand was implemented by Abaqus and Hypermesh. The quasi-static analytical results of ostrich foot toenail inserting the sands showed that the groove structure of the toenail had a better sand fixation effects, the tiptoe structure was conducive to insert into the sands, and the inverted triangular structure of the toenail had the weak disturbance on the sands which produced the less resistance of the toenail inserting the sands. According to the velocity and the stress fields in the process of the ostrich foot toenail dynamically traveling on sand, ostrich foot toenail tiptoe could help to improve the thrust of traveling on sand, the groove area of the toenail played the effects of sand fixation and flow limitation in the process of ostrich foot toenail traveling on sand. Keywords: ostrich foot toenail, reverse engineering, model reconstruction, finite element simulation, sand fixation and flow limitation.

Abstract: To avoid broadband noise from a slat cove, the deployed slat contour is usually modified by filling cove, but the design is sensitive to aerodynamic performance. In the paper, a bionic slat without a cove is built on the basis of a bionic airfoil (i.e. stowed bionic multi-element airfoil), which is extracted from a long-eared owl wing. The quasi-two-dimensional models with a deployed bionic slat and a stowed bionic slat are manufactured by rapid manufacturing and prototyping system, respectively, and measured in a low-turbulence wind tunnel. The results are used to characterize high-lift effect: the lift coefficients of the model with a stowed slat are larger at less than 4°angle of attack, but the model with a deployed slat has the larger lift coefficients at greater than 4°angle of attack. Furthermore, the deployed bionic slat can increase stall angle and maximum lift coefficient, but also delay the decline of the lift coefficient curve slope meaning that the leading-edge separation is postponed within a certain range of angle of attack. At the same time, the flow field around the models is visualized by smoke wire method. The leading-edge separation of the model with a stowed slat is shown at low Reynolds number and angle of attack. However, the finding does not occur in the flow field of the model with a deployed slat at the same conditions, probably because the gap between the bionic slat and the main wing results in favorable pressure gradient, the deployed bionic slat decreases the peak of adverse pressure gradient by increasing the chord of the bionic multi-element model, and the bionic slat wake excites transition to the boundary layer on upper surface of the main wing. This superiority may be used as reference in the design of the leading-edge slat without a cove.