Applied Mechanics and Materials Vol. 461

Abstract: Engineers often use nature as an inspiration for generating designs. Plants have optimised their structures over millions of years of evolution. A lotus root, rhizome of Nelumbo Nucifera Gaertn having gas canals was studied in the paper. The lotus root cross section subjected to an external water pressure was analysed and compared with other cross sections including a circular hollow cross section. It was found that the lotus root cross section has more areas containing higher triaxiality factors due to the holes. The hydrostatic stress in the lotus root cross section varies from zero to several times that of the external water pressure. However, the hydrostatic stress in a circular hollow cross section has a constant ratio to the external pressure. The research results show that engineering components with designed multi-holes can affect its failure behaviour. The structure of lotus root may be adopted in the design of engineering materials and structures.

Abstract: Adhesion of insects on murals is one of key factors leading to the biological diseases of wall paintings in cave temples. Murals in Mogao Grottoes, Dunhuang is art treasures. It is very important to study insects damage on murals for Mogao Grottoes preservation. We recorded locomotion and adhesive behavior of Apopestes spectrum on murals in Mogao Grottoes and simulated murals. The insects can creep steadily on inclined mural surfaces which angle of slopes are 90°, 135° and 180°, respectively. Its gait parameters were adjusted with the change of angle of slope. Apopestes spectrum adjust their locomotive and adhesive patterns on vertical murals with the change of roughness of the murals surface. The insects cant adhere on two kinds of simulated mural surfaces in ultramarine and realgar color whose roughness are 1.154~1.156 μm. And they can adhere on seven kinds of simulated surfaces in iron yellow, indigo, white lead, red lead, orpiment, vermilion and yellow lead color whose roughness are 1.319~2.714 μm depending on the mechanism of mechanical interlocking between claws and substrates. With the help of wing flapping, the insects can creep on these simulated murals. Apopestes spectrum can freely move and stably adhere by claws on other seven kinds of simulated surfaces in atacamite, ink, talc, gypsum, natural red soil, azurite and malachite color whose roughness are 3.129~6.662 μm. When insects climb on murals, their claw tips flip on the substrates and damage the surface the murals. Keywords: insect, locomotion, adhesion, mural, claw

Abstract: The biomaterials with excellent properties such as high strength-weights ratio and so on will inspire inspirations about bionic composite materials to satisfy the scalding hypercriticisms for aerial materials. The investigations of biomaterial mechanical performances are of great advantages in bionic designs and bionic manufactures. The mechanical performances of Bamboo Beetles Otidognathus Davidis Fairs abdominal shells were tested with a nanoindenter in this paper. The experiments results demonstrated that the harnesses and modulus are different at different test areas. The mechanical performances resemble much at the same latitude but decrease along longitude from the forehead to the rearward, indicating that the mechanical performances of the abdominal shells distribute topologically. Whats more, the topological distributions of mechanical performances illustrate a kind of unlearned structure optimizations of insects which will provide edifications to designs of light and strong materials.

Abstract: The study on the locomotion mechanism in laboratory has defined performance limits for animals presently. But it is more significant for investigating mechanics of animals in their free state. In order to study the locomotion properties of Chinese mitten crabs Eriocheir sinensis Milne-Edwards on one flat terrain and four kinds of rough terrains, a high speed 3-D video recording system was used to record motion video images of crabs. The gait pattern, average speeds, the mechanical energy of the mass center and percentage energy recovery were investigated with motion analysis system. The results showed that Chinese mitten crabs used alternating tetrapod gait on flat terrain and with increasing of terrain roughness, the regularity of gait tend to be less conspicuous. Crabs used two fundamental models of energy exchanging patterns: the inverted pendulum gait and the bouncing gait and the bouncing gait was the main energy saving and conserving pattern. Keywords-biomechanics, Chinese mitten crab, rough terrain, gait, mechanical energy, percentage energy recovery

Abstract: Kinematic models, which contain flapping and deformations, of a bat flapping wing when it flies at medium speeds are presented in the study. The deformations include cambering - morphing in the chordwise direction, bending - morphing in the spanwise direction and twisting respecting angles of attack (AOA) varying along the length of the wing. In the study, we assumed a circular-arc-shaped deformation when cambering or bending occurs, and introduced controlling parameters for each morphing. Then we showed the expressions of the controlling parameters varying with time at the bat flight speed of 3m/s according to the data provided by a literature, and verified the reasonability of the assumptions at last.

Abstract: This paper presents an invertebrate leg-like mechanism, which is biologically inspired from invertebrate creatures such as crabs and insects. For the purpose that the leg mechanism could imitate the behavior of the invertebrate animal on rough terrain, it should have the same degree of freedom as the crabs or insects have. The novel leg mechanism consists of 3 joints which linkage has 5 degrees of freedom (DOFS), and mainly depends on a coxa joint driven by a parallel mechanism for the biomimetic motions. The parallel mechanism with 3 DOF is well designed and implemented with the excellent kinematical performances as invertebrate creatures. The mathematical model of the leg mechanism and the kinematical analysis are described, and static force performance characteristics are also discussed. The kinematical performances of the leg mechanism are analyzed by the numerical simulation conducted in biomimetic robots application. The simulation results show the performance of the proposed leg-like mechanism and verify that the leg can be used in the biomimetic robot which could exactly imitate limb motions.

Abstract: Fluid-structure interaction (FSI), which solves the coupling between solid and fluid, has more and more been adopted by researchers to better study interaction between the hydrodynamic and structural flexibility. In this paper we adopt FSI and study a model simplified from the pectoral fin of Koi Carp. Flexibility is a comprehensive assessment of soft structures, it not only relates to the material constitutive parameter, but also relates to the apparent morphology parameter. The Young’s modulus and moment of inertia are two typical parameters. In this paper we first investigate the Young’s modulus’ effect on the propulsive performance, the fluid structures are analyzed and the motions are presented, then we discuss the moment of inertia, their thrust forces are compared. Results show that proper flexibility can greatly increase the thrust forces while too flexible fin’s behavior is worse. Moreover, the bending stiffness, a uniform parameter combines the material property and morphology parameter, is explored. It is found out that even for the same bending stiffness, different couples of Young’s modulus and moment of inertia will lead to different propulsive performance. These findings will provide a useful guidance for the design and manufacture of novel flexible underwater bio-mimetic vehicles.

Abstract: Due to the space constraints and obstacles, the traditional industrial manipulator is too difficult to achieve some tasks, such as the gluing for the wing bulkhead of the aircraft and the maintenance for cooling pipes of the nuclear power plant, etc. Continuum manipulator, inspired by the trunk and the tentacle, proves to be very effective for above-mentioned tasks. A novel octopus-like biomimetic robots, is proposed in this paper, which is consisting of continuum joints and discrete joints, and provide a host of benefits, such as the large space of movement, the high flexibility and the heavy load. A novel analytical approach for solving kinematics of the octopus-like arm manipulator with mixed joints is presented in this paper. Based on the bionic mechanism of the continuum manipulator constructed from mixed joints, the robot configuration is established. In this paper, we present a detailed formulation and explanation of a novel kinematic model for the continuum robots with mixed joints. The modeling method based on the Denavit–Hartenberg parameters(also called DH parameters) is used to depict the motion of robot. The robot is comprised of the continuum joint and the rotated joint, so the kinematic model of continuum joint is crucial for constructing that of the whole robot. The continuum joint is equivalent to a section of elastic body, whose D-H parametors can be obtain from the constant-curvature method. Then the forward kinematics of the whole robot can be builded in a D-H frame. Research results will create a new modeling method for the octopus-like continuum manipulators with mixed joints, which can give a new approach for the design on the biomimetic manipulators operating in the unstructured envirement.

Abstract: The fine-level structure of toes contributes to the extraordinary climbing ability of G. gecko. Research on the morphology specificity of gecko feet at different scales provides anatomical information for revealing geckos motor ability and provides theoretical basis and data which can support the development of the robot gecko feet. During the research, we used KEYENCE (VHX-600E) digital microscope system to observe and photograph the forefoot and hindfoot of G. gecko at different scales. The image processing as well as calculation of foot area and toe area was done using image processing software after the number of toe setae lamella was counted. Results: there was no significant difference between the numbers of setae lamellae on the first toes in both forefoot and hindfoot (p>0.3). The same situation also appeared in the second and forth toes. Significant difference between the numbers of the third toe setae lamella in forefoot and hindfoot was observed, the same situation also happened in the fifth toes of the forefoot and hindfoot (p<0.01), the difference between the whole area of the forefoot and hindfoot was extremely significant (p<0.005). The area of the first toe in forefoot was different from the corresponding one in hindfoot (p<0.05), while the areas of the other four toes were extremely significant from the corresponding ones in hindfoot (p<0.005). The results of the research suggest that specific designs should be adopted in the devisal of forefoot and hindfoot as well as the corresponding toes.

Abstract: Removed at authors request