Papers by Author: Bao Xian Jia

Abstract: SMPC (shape memory polymer composites) has many advantages as a hinge of spacedeployable antenna. The structure of the SMPC hinge is designed and tested in this paper. The basicmechanical properties of composites are calculated. Through finite element simulation, the bendingmoment of the positive and reverse of the lamella with the bending angle as the lamella with the fiberdifferent content, the bending of the lamella with different bending distances was simulated, and thecurves of bending moment with bending angle in different bending distances were obtained. Hingebending process simulation shows when the hinge begins to bend, the stress of the inner positivebending lamella is larger. The stress of the outside bending lamella increases with the increase of thebending angle. As for the relationship of moment-angle, the process of unfolding of the hinge isbasically the same as that of the lamellae. However, the hinge bending moment is much greater thanthe single layer lamella bending moment. The hinge with the structure of back-to-back can increasethe structure stiffness and the bending resilience ability. The tested moment of the hinge is similar tothe simulation result.

Abstract: The SMPC (Shape Memory Polymer Composite) is used for space deployable structuredue to their excellent properties. In this paper, the space deployable antenna was designed, whichincludes the design of the basic configuration, the antenna substrate, the SMPC hinge and its location.The modal of the hinge was studied with finite element software ABAQUS. The hinges with differentthickness were analyzed and compared. The modal of single piece antenna was calculated. Thevibration types and natural frequencies of the single piece antenna in connection are obtained. Theeffects of different hinge structures on the overall mode and the natural frequencies of the hinge werestudied. The influence of hinge location on the natural frequencies of deployable antenna was alsostudied. The mode of four pieces antenna in unfolding was calculated, the main vibration types wereobtained, and the natural frequencies were analyzed and compared with that of the single pieceantenna. In unfolding, the natural frequencies of the four pieces antenna are lower than that of thesingle piece one.

Abstract: It is widely believed that large composite materials are difficult to build a ship which is longer than 40 meters because of lack of structural stiffness. Up to now, the ships, 72-meter in length, made of glass fiber reinforced composite have been in serve abroad, while 35 meters in China. Therefore, it’s absolutely necessary to study the problem about the stiffness of the 70-metre composite materials hulls. Start from integration design and finite element analysis of composite materials and structure, the influences of material component, laminated angle and laminated sequences of composite materials’ hull on the dynamic stiffness and static stiffness of the ship are studied to explore the method of improving stiffness. The result show that, in the conditions of having the same molded surface, ship's weight and applied stress, it can improve the ship’s longitudinal stiffness to reach standard requirements by using the part of the high modulus fiber as well as the high modulus fiber laying on the outboard of the hull.

Abstract: This paper works on the vibration control of the space truss structure. The damper made of viscoelastic composite was designed according to the configuration parameters of the truss structure. The parameters of damper were obtained by using the method of modal strain energy. The optimal position configuration of the damper was determined. The truss in the time domain and frequency domain was analyzed. The dynamic characteristics of three structures which are without damper, with damper in the random position configuration and with damper in the optimal position configuration were compared in the sweep excitation and pulse excitation. The result shows that the structure with damper in the optimal position configuration has a great improvement in the amplitude of vibration in the first resonance region and the amplitude attenuation of the truss. The space truss structure with viscoelastic composite damper has excellent vibration control effect.

Abstract: In order to get the deployable antenna with light weight but large size and high stiffness, this study investigated SMPC self-deployable driver mechanism based on the deformation mechanism of SMPC, and designed the SMPC space deployable antenna. The laminated shell structure with two pieces of back-to-back configuration was analyzed. Finite element analysis revealed that the reasonable central angle of the laminated shell cross-section was 90°. The ends fixing structure of the SMPC hinge was given. The function and structure of the hoop truss deployable antenna were designed to meet the functional and accuracy requirements.

Abstract: In order to obtain micro holes with high aspect ratio, a new technique of machining deep micro holes by combining EDM (Electrical Discharge Machining) with USM (Ultrasonic Machining) in inversion installing is researched. The workpiece is over the electrode. The ultrasonic vibration is affixed to the electrode. The workpiece and electrode are all immersed in working liquid. The debris generated by EDM is dropped out the hole from the gap between the electrode and the hole wall by the gravity and the pumping effect of ultrasonic vibration, so as to increasing the machining velocity and machined depth. The structural features of the machining device are described, and the exploratory experiment is carried out. The corresponding process relations are found out, which can provide references for further study of this technique. The micro holes with larger than 25 in aspect ratio are machined.

Abstract: Developed with micro technology, the microelectrode is the key manufacture technique. The micro electrical machining, mainly including micro electrical discharge machining (EDM) and electrochemical machining (ECM), is one of the important technologies of microelectrode fabrication. Firstly, the microelectrode was fabricated with a counter block of EDM while the cylindrical tungsten electrode fed along radius and its axis. Then the fabrication technology of ECM was also introduced. The pulses power supply and the non-passivation electrolyte were used. The cylindrical tungsten electrode also can be served as the probe of the scanning probe microscopy, which fabricated by ECM. Through comparisons, the surface roughness, machining efficiency, and machining capability of the microelectrode fabricated by ECM are better than those of the microelectrode fabricated by EDM, but the shape and the microhardness are worse than those of the microelectrode fabricated by EDM. Both of them can fabricate the cylindrical tungsten microelectrodes with several micrometers diameter.

Abstract: Experiments of combining micro EDM with USM are carried out to enhance the machining ability and flexibility of the micro EDM, improve the machining state, and increase the productivity and aspect ratio of the micro holes. Basing on RC pulse power supply and workpiece vibration, the micro holes are drilled. The results of comparing experiments indicate that in the processes of both micro EDM without USM and micro EDM with USM, the machining velocity and the wear of the electrode increase with the increase of open voltage and loop capacitance. The experiment results of amplitude influencing on the machining process indicate that with the increase of ultrasonic amplitude, the machining velocity heightens and the aspect ratio of the micro holes augments; at the same time, however, the wear of the electrode and the extensive magnitude of the holes increase. Micro holes with some cross-section and accurate profile are drilled steadily.

Abstract: Considering the key technologies to enhance the accuracy of micro-EDM, a micro-EDM system and some techniques are researched. In this system, a micro-energy pulse power supply whose open voltage and capacitance can be adjusted is developed. The detection and control subsystem of the machining process is designed and applied. A simple method of machining high precision microelectrodes is adopted. The forming mechanism of the gap in EDM process is analyzed theoretically. The processing experiments are carried out on the system, and the results basically coincide with the theoretical analysis. The experimental results of machining microelectrodes and micro holes show that the Ø4.5±0.5μm microelectrodes can be ground, and the Ø6±2.0μm micro holes can be drilled.

Abstract: It is necessary to drill micro holes in some hard brittle materials. Comparing with electro discharge machining, electrochemical machining and laser machining, the ultrasonic machining (USM) has unique advantages in hard brittle materials machining. The aim of this paper is to present experimental work that has been done in micro holes machining by micro USM. The main machining mechanisms of USM are discussed. It is pointed out that the contributions of each mechanism to material removal rate are different in different cases. By using micro USM with workpiece vibration and tool feeding in constant rate, the experiments of micro holes machining are carried out and the process laws of tool wear are studied. Some phenomena are found and the causation of causing these phenomena is analyzed. A Ø13μm micro hole is obtained.