Key Engineering Materials Vol. 625

Abstract: The maximum speed of KTX is 305 km/h for commercial service and it is designed to reach 330 km/h. The design fatigue life of KTX running gear systems is 20 years. The mileage per year of KTX train is 600,000 km/year. In other words, the design life of the KTX running gear systems is 12,000,000km. KTX train is designed to be dedicated to driving the high-speed railway. But the KTX train routes that connect with the conventional line and high-speed line service. South Korea’s high-speed railway design maximum speed is 350km/h. Comparison, speed KTX train existing line of service is set to 150km/h, 180km/h and 220km/h, depending on the section. Thus, the value of the maximum torque, torsional stress and bending moments acting on the KTX running gear systems may appear differently from the high-speed line design criteria. Furthermore, the maximum stress/strain acting on the suspension of parts of the running gear system is different. In this study, the actual KTX train to set running gear system design life compared to the actual life, according to the characteristics of the actual service routes were compared and analyzed.

Abstract: We proposed a simple and low cost dielectrophoretic device to trap and isolate single target cells. The device consisted of a metal coated chemically etched fiber and an AC signal generator. It did not require microfabrication technologies or sophisticated electronics. Using this system, we could easily trap and isolate yeast cells at will. Furthermore, our dielectrophoretic manipulator also could discriminate between live and dead cells by tuning of the applied signal frequency. From these experimental investigations, it was found that our proposed dielectrophoresis tweezers using metal coated chemically etched fiber was a promising tool for the single cell manipulation and isolation.

Abstract: Knowledge about dynamic performance is very important for a control system. When carrying out static performance of a mobile robot, the sensing distance of various materials is established. However, based solely on this factor for controlling the mobile is not exact. Because in fact, many factors will influence to mobile robot controlling, they are determined by the relationship between the physical quantity in the measurement. Through a detailed study of theoretical knowledge and by some empirical methods of the conveyor system, we can determine the relationship of the dynamic parameters, such as: velocity, sensing distance, dimension of material, thickness of material, and so on. Experimental results demonstrate that the shape as the output signal depends on the type of sensor being used. To research the scope of the mobile robot, an analog proximity sensor is optimal, and to identify the output signal ON or OFF, the selection of digital sensor is better than an analog sensor. This is as a basis to improve the theoretical knowledge of mobile robot controller through the proximity sensor. Simultaneously, with these results, mobile robot is able to sense its world and change its behaviour on that basis.

Abstract: The lexical meaning of derailment shall be the wheels of trains going off the track and it is an important factor for the running safety of railway vehicles. For the measurement of interaction forces between the wheel and the rail, wheel set is used with normal method and the vibration accelerometer is used with simplified method to assess the safety of a railway vehicle in the derailment process. The result has been recorded by measuring vibration acceleration.

Abstract: In this paper, chemically etched axicon fiber was investigated for laser trapping of micro-object dispersed in liquid. We fabricated axicon micro lenses on a single-mode bare optical fiber by selective chemical etching technique. The laser beam from fiber axicon microlens was strongly focused and optical forces were sufficient to move a microorganisms and biological cells without physical contact. In our experiments, several different lasers with various wavelengths were used as light sources. From these experimental results, it was found that laser wavelength was very important parameter for cell trapping and laser wavelength should be selected to avoid absorption by cells in order to prevent thermal degradation and damage to the cells.

Abstract: Along with the miniaturization of products and the precision of micro-assembly, the ultra-micro dispensing is an important guarantee to realize precision assembly. In this paper, we analyze the dynamic process of an ultra-micro (fL class) dispensing based on the micro-droplet surface tension. According to the analysis, the micro-fluid dynamics model is built in the CFD (Computational Fluid Dynamics) software Fluent14.0 program, and the working process is dynamically simulated based on the model. Furthermore, the experiment platform is established and actual dispensing process similar to the simulation is successfully acquired under the same conditions. Finally, the diameters of actual dispensing dots are compared with simulation values respectively under the same three sets of different dispensing parameters, and results show that actual values keep high consistency with the simulations, which verifies the correctness and feasibility of the proposed micro-fluid dynamics model.

Abstract: Machine vision systems have been used in the automatic inspection of screw threads using backlight illumination for the inspection of the screw thread profiles. In this study, an alternative inspection system based on front light illumination is developed to directly obtain thread images so that surface defects can be measured. To realize such an inspection system, an omnidirectional optical measurement device is proposed to obtain 360^o images of screws for inspection of whole thread regions. Optical simulation based on ray tracing is then performed to analyze optical paths and to optimize the image quality of the designed optical system.

Abstract: Electro wedge brake (EWB) have been suggested and improved for enhancing the braking efficiency and reducing the weight and power of actuating motor than electro mechanical brake (EMB). This is due to self-reinforcement features of the wedge mechanism. On the other hand, the conventional hydraulic brake system has the passive wear adjustment without any sensors and actuators. This is because of the sealing rubber which is disposed between the hydraulic cylinder and piston, and supply the piston’s same restoring strokes regardless of pad’s wear amounts. This feature leads to the uniform distance between the disc and the pad. In comparison, electronic brake systems such as EMB and EWB don’t have the hydraulic piston and cylinder with the sealing rubber. Therefore the electronic brake systems cannot use the function of this passive wear adjustment. However, if the electronic brake system has gap sensors for detecting distances between the pad and the disc, and actuators for keeping the uniform distances between the pad and the disc, then the brake system can have the function of wear adjustments. One of our research goals is the embodiment of cost-effective and feasible wear adjustment mechanism which is proper to EWB. In this paper, as a chain of EWB’s development, we describe the proposed mechanism for wear adjustment with EWB. Further we describe the feasibility of this mechanism with the simulation study.

Abstract: The adjustment of cell position and orientation is important in cell micromanipulation of bioengineering, which directly affects the efficiency and success ratio of the micromanipulation. Cell orientation can be adjusted by swirl, which comes from a pair of parallel opposite micro-fluids from two tiny tubes, and the cell in swirl center will rotate. Quantitative control of rotation angle and velocity of the cell can be achieved by adjusting the velocity and frequency of micro-fluid. This control method of cell orientation has prospective applications for its non-contact characteristics. However, cell will not be right in the swirl center in practical operations. And if the eccentric cell can rotate steadily, swirl method will be more reliable. So numerical simulation was conducted to study the movement trajectory of cells with eccentricity, and the influences of eccentric directions and eccentric distances were discussed. The simulation results indicate the feasibility of orientation control of cells with eccentricity by swirl.

Abstract: Torsional buckling of single-walled carbon nanotubes filled with light weight molecular via molecular dynamics is reported. The model accounts for the deformation of CNTs, and interactions among gas molecules; between gas and carbon atoms. The effect of particle loading is predicted to significantly change CNT’s critical torsional moment and stiffness. This is therefore an approach by which the torsional mechanical properties and oscillation frequencies of carbon nanotubes may be tuned. Importantly, the predicted changes in torsional siffness are unique relative to conventional linear elastic materials and are indicative of nonlinear oscillations due to nonlinear mechanical effects. CNTs subjects to large deformations reversibly switch into different morphological patterns. Each shape change corresponds to an abrupt release of energy and a singularity in the stress-strain curve. At higher torsional angle, van der Waals (VDW: He, Ar, H₂) molecules reveal a stability effect on carbon nanotubes.