Advanced Materials Research Vols. 291-294

Abstract: Vibration testing and modal experiment under the different speed are carried out to the high speed motorized spindle whose maximum speed is 60 000 rpm. Time domain waveform and spectrum of motorized spindle’s radial vibration acceleration are obtained under the unload state. Through calculating and analyzing, the vibration velocity and the testing point which generates the maximum vibration velocity are found out. Then motorized spindle is validated whether it accords with the requirements of high-precision manufacture. And the correctness of the vibration testing method is also verified. Primary reasons of the motorized spindle’s vibration are put forward. The first five steps natural frequencies of motorized spindle test-bed are gained by appropriate ways to checkout if the test-bed in the resonance region.

Abstract: Four micro-holes were made using micro-EDM on the rake face of the cemented carbide (WC/TiC/Co) tools. CaF₂ solid lubricants were embedded into the microholes to form self-lubricating tool (SLT-1). Dry machining tests on hardened steel were carried out with the SLT-1 self-lubricating tool and conventional tool (SLT-2). The cutting forces, tool wear and friction coefficient were measured and compared. It was shown that the cutting performance of SLT-1 self-lubricating tool was greatly improved compared with that of the SLT-2 conventional tool. Through the analysis of cutting force theory and test results, the mechanism of cutting performance improvement was considered to be the formation of a self-lubricating film on the rake face which decreases the shear stress and the reduction of contact length between chip and tool.

Abstract: Pores are always considered as a kind of defect during manufacturing metal parts via many conventional processes. But porous metals have outstanding physical and mechanical properties which providing them double natures of function and structure, and are applied in many fields of science and technology. Selective laser melting (SLM), developed within current years, has the advantages of producing metal parts with complex structures, and can be used to manufacture complex structures of any kind theoretically. A new method of making porous complicated metal structures via SLM is put forward. Then, the meaning of this method, research advance and future work discussion are presented in this paper, which lays a method foundation for future study and build a new field for both porous metal parts and SLM technology.

Abstract: As an important factor the error of mask pattern is often ignored in the lithography simulation model. To investigate the impact of mask errors on the lithographic pattern, effects of how the wave-front on different mask pattern region affects the field points in resist is first introduced, and based on this analysis a method is proposed to quickly judge the affection of round corner error of mask pattern on the photo-resist pattern. By comparing the actual effect area and the effective wave-front area around the corner on mask pattern, the method can illustrate the quantitative relationship between variation in photo-resist pattern and the related mask error. Finally the simulation results are verified by experiments. The study results may contribute to the fast and accurate judgments of error in the lithography, and provide important theoretical basis for lithography error correction.

Abstract: High-g acceleration sensors are used in high-impact environment, the ability of resisting high-overload is demand higher requirements.In order to determine the Shock-resistibility of the sensors, tests were performed using Hopkinson bar. Analysis of the failure mechanism of the sensor.The results show that the critical load resulting in sensor failure is about 200000g. Main failure mode of the sensor chip is broken.

Abstract: Traditional parallel manipulators suffer from errors due to backlash, hysteresis, and vibration in the mechanical joints. In this paper, a new 3SPS+RPR spatial compliant mechanism which has three degrees of freedom (DOF) and can generate motions in a microscopic scale is proposed. It can be utilized for biomedical engineering and fiber optics industry. The detailed design of the structure is introduced, followed by the performance evaluation. Then, the genetic algorithms and radial basis function networks are implemented to search for the optimal architecture and behavior parameters in terms of global stiffness/compliance, dexterity and manipulability.

Abstract: Graphene, comprising of monolayer of carbon atoms packed into a two-dimensional honeycomb lattice, has a series of peculiar properties such as the anomalously quantized Hall effects, the large charge carrier mobility and so on. Both micromechanical cleavage method and hydrazine reduction process are used to produce graphene sheet. Two kinds of graphene pattern have been placed between the source and the drain electrodes of a new type of combined three dimensional back-gated FET as the channel by location transplantation method. Micromechanical cleavage method can produce graphene which has uniform crystal lattice structure and the same chirality, while chemical reductions produce graphene with different chirality. The IDS-VDS curves of FET properties show that micromechanical cleavage graphene sheet channels have obvious response to the gate voltage.

Abstract: Severe deformation which was induced by internal (residual) stress was observed on the MOEMS focusing device without driving voltage. Based on beam suspended membrane, FEM software COMSOL Multiphysics was used to predict the deformation induced by internal stress, model parameters (beam width and length), boundary condition of the chip. Found the parameters which can make the membrane be relative flat initially. Expanded the model including ring shaped electrode, using COMSOL coupled fields(AC/DC-Electrostatics module, Structural Mechanics-Solid Mechanics module and Mathematics-Deformed Mesh-Moving Mesh module), found the inner radius of ring shaped electrode which can get perfect parabolic shape of membrane with large maximum relative deflection under driving voltage.

Abstract: An experimental investigation has been carried out with clarifying the external mechanical stress effect on GaAs metal-semiconductor field-effect transistor (MESFET) I-V characteristic curve which as the sensitive element of micro-accelerometer in different condition. In this paper, we research different channel directions to explore the output characteristics of the GaAs MESFET which fabricated at the root of the cantilever. We design three channel directions which angled with the cantilever as 0 degree, 45 degree, 90 degree. We find that when the Channel direction parallel to the cantilever direction, ∆U has the maximum value of 12.13mv. The sensitivity of 0 degree is 0.04mv/g higher than the 90 degree. The dynamic result indicates that the channel direction parallel to the cantilever direction is the optimized design structure.

Abstract: A prototype of miniature vapor compression heat pump system was introduced. On the basis of compressor, capillary, condenser and evaporator models, the steady-state model of air-to-water miniature heat pump system is developed with regard to energy and refrigerant inventory conservations among all these components. The results show that the relative error between prediction and experiment values is less than 5%, and the optimal match of condenser and evaporator lengths were obtained by simulation program.