An analytical method that can be generally applied to structural analysis of a pontoon-separated floating bridge connected by elastic hinges is proposed based on elastic foundation beam theory and ...Euler beam theory. This method can solve the displacement, rotation angle, bending moment and shearing force of a pontoon-separated floating bridge under vertical static loads. Validation of the method is established through comparing with the numerical results of AQWA software and FEM. Simultaneously, the main response characteristics of a pontoon-separated floating bridge and a floating pier are further investigated. The results reveal that the rotation stiffness of elastic hinges has a significant influence on the responses of the pontoon-separated floating bridge. Besides, the elastic deformation of the floating bridge can be ignored when the rotation stiffness of hinge is relatively small, while it needs to be considered seriously when the rotation stiffness of hinges reaches a certain value.
Because of the limited space of the launch rockets, deployable mechanisms are always used to solve the phenomenon. One dimensional deployable mast can deploy and support antenna, solar sail and space ...optical camera. Tape-spring hyperelastic hinges can be folded and extended into a rod like configuration. It utilizes the strain energy to realize self-deploying and drive the other structures. One kind of triangular prism mast with tape-spring hyperelastic hinges is proposed and developed. Stretching and compression stiffness theoretical model are established with considering the tape-spring hyperelastic hinges based on static theory. The finite element model of ten-module triangular prism mast is set up by ABAQUS with the tape-spring hyperelastic hinge and parameter study is performed to investigate the influence of thickness, section angle and radius. Two-module TPM is processed and tested the compression stiffness by the laser displacement sensor, deploying repeat accuracy by the high speed camera, modal shape and fundamental frequency at cantilever position by LMS multi-channel vibration test and analysis system, which are used to verify precision of the theoretical and finite element models of ten-module triangular prism mast with the tape-spring hyperelastic hinges. This research proposes an innovative one dimensional triangular prism with tape-spring hyperelastic hinge which has great application value to the space deployable mechanisms.
The purpose of the work is to study the influence of the control of the elastic and damping characteristics of the cushioning system based on the use of magnetorheological elastomers on the ...smoothness of the course of wheeled transport vehicles. The technique. The research used the methods of: magnetic field theory, the theory of vehicle suspension, experiment theory planning, and the FEMM code for studying magnetic field characteristics and mathematical modeling of wheeled vehicle movement along roughness in the Delphi environment. Results. Designed, researched and patented designs of elastic hinges of the suspension arms with magnetorheological elastomers. The relative boundaries of changes in the elastic modules and losses of these hinges are determined when controlling the characteristics of the suspension in order to improve the smoothness of the wheeled vehicle. Scientific novelty. For the first time, the feasibility of using magnetorheological elastomers to control the elastic and damping characteristics of the cushioning system of wheeled vehicles has been investigated, and the requirements for control laws have been determined, which make it possible to increase smoothness by more than 40%; it is established that the control of the loss modulus has a greater effect on the improvement of smoothness of motion than the control of the elastic modulus. Practical value. The design has been developed and the relative boundaries of changes in the modules of elasticity and loss of hinges with magnetorheological elastomers during their control have been determined, which will make it possible to formulate requirements for elastomers when developing promising hinge designs for vehicle suspension systems. References 21, figures 18.
In this paper, we have developed a process for multistep sequential batch assembly of complex three-dimensional (3-D) ferromagnetic microstructures. The process uses the magnetic torque generated by ...an external magnetic field perpendicular to the substrate to lift hinged structures. We found that a dimensionless factor that depends on the volume of the magnetic material and the stiffness of the hinges determines the sensitivity of the hinged microstructures to a magnetic field. This factor was used as a criterion in designing a process for sequential batch assembly, i.e., for setting appropriate differences in sensitivity. Using a dimensionless factor in the design of the sequential assembly simplified the assembly process, which requires only placing the structures on a permanent magnet, and which can be used to carry out multistep sequential batch assembly. We fabricated hinged microstructures, which consist of 4.5-/spl mu/m-thick electroplated Permalloy plates and 200-nm-thick nickel elastic hinges of various sizes. In an experiment, four plates (600 /spl mu/m/spl times/800 /spl mu/m) were lifted sequentially and out-of-plane microstructures were assembled in a four-step process. Assembly of more complex out-of-plane microstructures (e.g., regular tetrahedrons, 800 /spl mu/m long on one side) was also shown to be feasible using this method of sequential batch assembly. 1351.
There are two drawbacks in the performance of the resonant vibration cutting tools currently available. One is that the vibration frequency cannot be changed arbitrarily and the other is that the ...cutting force is low. It is impossible to turn mirror plates with many kinds of materials using these resonant vibration cutting tools because they cannot match the desirable turning speeds that correspond to the machined materials and the vibration frequency needs to be increased or decreased to obtain the desired surface roughness. Resonant vibration cutting tools do not allow the vibration frequency to be set arbitrarily. The small cutting force of these tools also causes some difficulties in diamond turning of metals other than soft metals such as aluminum and copper. In this research, we developed a vibration cutting tool that can generate two-dimensional vibration shapes without distortion by placing two piezoelectric actuators at right angles. This tool can machine the many kinds of mirror plates with different materials to the desired surface roughness. It is also possible to machine hard materials such as mold steels because the amplitudes of the vibrations do not decrease, even when large cutting forces are required. In this paper, we describe the design of the nonresonant vibration cutting tool, and show by the diamond turning of oxygen-free copper and aluminum that our nonresonant vibration cutting tool can machine desired shapes. Finally, it is verified by actual machining experiments that the proposed vibration cutting tool can machine hardened mold steels such as STAVAX with HRC 54.
Development of UB Hand 3: Early Results Lotti, F.; Tiezzi, P.; Vassura, G. ...
Proceedings of the 2005 IEEE International Conference on Robotics and Automation,
2005
Conference Proceeding
The first part of this paper describes the development of a humanoid robot hand based on an endoskeleton made of rigid links connected with elastic hinges, actuated by sheath routed tendons and ...covered by continuous compliant pulps. The project is called UB Hand 3 (University of Bologna Hand, 3rd version) and aims to reduce the mechanical complexity of robotic end effectors yet maintaining full anthropomorphic aspect and a good level of dexterity. In the second part this paper focuses on the early experiences of the UB Hand 3 in performing manipulation tasks.
This paper describes three-dimensional (3-D) microstructure assembly using an external magnetic field. An external magnetic field perpendicular to a substrate lifts a hinged structure by the torque ...due to the shape magnetic anisotropy. We made micro flap structures (4.5 µm-thick electroplated Permalloy) which have 0.2 µm-thick nickel elastic hinges in various size, and made lift the structures in a magnetic field up to 50 kA/m. We demonstrated that the non-dimensional factor depending on the volume of magnetic material and the stiffness of the hinges determine the sensitivity to the magnetic field. As a result, we realized sequential batch assembly using the difference of the sensitivity. The each two plates 600 µm × 600 µm in size were lifted sequentially, and out-of-plane microstructures were assembled. And the complex out-of-plan microstructures, the regular tetrahedrons 800 µm on a side with a closed linkage were able to assemble by our method.
Shape Optimization for Flexure Hinges OIWA, Takaaki; SUGIMOTO, Toshihiko
Journal of the Japan Society for Precision Engineering,
1997, 1997-00-00, Letnik:
63, Številka:
10
Journal Article
Odprti dostop
The purpose of this study is to design an optimum profile of the flexure hinge with high axial stiffness and high bending flexibility. The conventional circular notched and rectangular notched ...profiles are not optimum because of low flexibility and high stress concentration. In this paper, the optimum profile with uniform stress distribution was generated using the finite element method under constraint conditions which unify the axial stiffness and minimum thickness of the notched profiles. Moreover, the flexibility of the optimum profile was compared with the flexibility of ellipse profiles, round rectangular profiles and profiles described by higher degree functions. As a result, the optimum profile had flatter stress distribution and the highest flexibility under a maximum stress constraint condition. The optimum hinge has 19% higher bending compliance than the conventional circular notched hinge, and produces 67% higher deflection angle than the rectangular notched hinge.
To machine a complex precision product, several tools are needed. These tools are placed on a tool turret. A tool must return several times to its original position. To attain a very high ...repeatability between the upper part and the base of the tool turret mounted on a precision lathe, it is preferable that the parts of the tool turret are statically determined in their contacts. This is attained by using a kinematic coupling. To attain the required stiffness this coupling is provided with a preload of 1.5 · 10
3 N. The machining forces are typically less than 1 Newton. A special kinematic coupling, consisting of grooves and balls, was designed, made, and tested. By providing the grooves with self-adjusting surfaces, hysteresis is reduced to less than one-tenth of a micrometer. Maximum stiffness is aimed at by using cemented carbide, a material with a high admissible stress, at the contact points. Experiments show that this kinematic coupling, under a preload of 1.5 · 10
3 N, has a static stiffness of more than 1 · 10
8 N/m in every direction and a repeatability better than one-tenth of a micrometer.
This paper describes the float characteristics of an aerodynamic sliding table which can realize non-contact linear motion guide systems using squeeze-gas film effect. This sliding table uses ...piezoelectric actuators and elastic hinges in order to vibrate the slider surface and generate squeeze-gas film pressure. In the theoretical analysis, a simple dynamic model of the proposed sliding table is presented. The influences of displacement and vibration frequency of piezoelectric actuators on the float characteristics are investigated theoretically and experimentally. In addition, load capacity at vibration frequency of 2200 Hz is experimentally measured. It was consequently found that the proposed sliding table can realize a non-contact linear motion guide and the dynamic model presented in this paper can predict well the float characteristics of the proposed sliding table.
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