Applied Mechanics and Materials Vols. 52-54

Abstract: This paper presents a design approach for the conceptual design of a novel 16-speed bicycle drive hub. First, a distributed-flow type planetary gear train, which consists of two parallel- connected transmission units and one differential unit, for the power transmission mechanism of a bicycle drive hub is proposed. Based on the kinematic analysis of the presented gear mechanism, a feasible clutching sequence is synthesized to provide 16 forward speeds. Then, the numbers of teeth of all gears are determined according to the desired velocity ratio of each speed. As a result, a schematic diagram of the embodiment of the proposed 16-speed drive hub is presented.

Abstract: The prediction of the magnetic field is a prerequisite to investigate the motor performance. This paper focuses on the magnetic field estimation of surface-mounted permanent-magnet (SMPM) motors based on two approximations, i.e., the magnetic circuit analysis and the finite-element analysis (FEA). An equivalent magnetic circuit model is applied to analytically evaluate the magnetic field of a SMPM motor with exterior-rotor configuration. The two-dimensional FEA is then applied to numerically calculate the magnetic field and to verify the validity of the magnetic circuit model. The results show that the errors between the analytical predictions and FEA results are less than 6%. It is of benefit to further design purposes and optimization of SMPM motors.

Abstract: With the consideration of compressibility flow and the redefined load flow and load pressure, the mathematical model of long-stroke valve-controlled asymmetrical cylinder system is presented. The equivalent volume functions, the functions of equivalent volume functions of cylinder's two chambers are introduced, which reflects the influence of piston's positions in its long stroke on the dynamic performance of valve-controlled cylinder. Simulation results show that there exists obvious differences between forward and backward directions of long-stroke valve-controlled asymmetrical cylinder system, and its dynamic performance varies along the whole stroke, where the middle-stroke position may not always be the so-called most dangerous position.

Abstract: Among the infrared spectrum, the range of 4-14 μm belonging to far-infrared (FIR) spectrum is named as “growth rays” due to many beneficial effects represented on organisms. Recently, many biomedical materials have been provided and manufactured based on the growth rays for health care as well as complimentary and alternative therapies. In this study, we probed the effect of FIR hot compress on antioxidation ability in human by determining the concentration of superoxide anions in blood. The results revealed that the level of superoxide anions in sympathetic, parasympathetic, and sympathetic plus parasympathetic group was decreased, rather than control group. This suggested that FIR exposure can significantly eliminate superoxide anions and provide protective effect against oxidative damage in human.

Abstract: The dynamic model of two-span rotor-bearing system with three-coupling faults of rub-impact, crack and pedestal looseness faults was set up, and the influences of faults to nonlinear dynamic characteristics of the system were studied by mapping and continuation comprehensive method. There are many harmonic elements of 1/3, 1/2, 2/3, 1, 3/2 and 2 et al within the sub-critical rotate speed range. But the 3/2 and 2-harmonic elements decrease within the super-critical rotate speed range. It may the main characteristics of the system with three-coupling faults of rub-impact, crack and pedestal looseness. It should notice to diagnosis the three-coupling faults of the system when running within the super-critical rotate speed range.

Abstract: An aircraft with morphing or adaptive wings can achieve its flight control through structural flexibility. In order to carry out such aircraft control, the wing structure is actuated by an external force. This leads to a change in aircraft aeroelastic and mechanical characteristics during flight such as lift, control effectiveness, divergence, flutter, buckling, and stress. The objective of this research is to demonstrate the aeroelastic and mechanical behaviors of a wing being actuated by external forces. Static and dynamic aeroelastic models of a wing structure subject to external loads are derived. An un-swept rectangular wing box, using a twisting morphing concept, is used for the demonstration. By applying various values of an actuator moment to the wing, aircraft design parameters e.g. flutter, divergence, lift effectiveness, buckling factor, and stress are computed. The investigation shows that the actuating force has an impact on the aeroelastic and mechanical characteristics. This effect should be taken into account during the design/optimization process of a morphing aircraft structure.

Abstract: According to the design requests of certain heavy truck, this paper introduces a design scheme of pneumatic AMT automatic shift system, which focuses on the structure characteristics and working principles of the three-position cylinder controlled by two solenoid valves. And the mathematical model of the three-position cylinder controlled by two solenoid valves is established based on pneumatic principle. The dynamic model of this mechanism was built by AMEsim software. The variety of pressure and stroke of intake/exhaust chamber was simulated under different air pressures. The theoretical basis is provided to design the AMT election-shift actuator.

Abstract: This study presented the application of Taguchi designed experiments to optimize the tungsten carbide/cobalt (WC-Co) deposited quality properties of the high-velocity oxygen-fuel (HVOF) process. The eight control factors were designed in a L18 factorial orthogonal array experiment, and the effects of control parameters on the surface properties were critically evaluated in the experiments. The surface anti-wear properties by optimal design have been studied comparatively. By optimization from Taguchi S/N ratios and analysis of variance, the surface wear volume values are decreased by 37%. It was clear that anti-wear performance estimations of HVOF sprayed WC-Co coatings are greatly improved by way of the optimal experiment, and these findings achieved the desired values in the WC-CO coatings. The experimental results indicated that the proposal method offers an effective and efficient approach for developing a robust and highly quality HVOF sprayed WC-Co coating.

Abstract: This paper presents the optimal chromium nitride (CrN) deposited performance by tuning magnetic systems on die steel in PVD. The strength of magnetic fields was controlled by adjusting the gap distance between magnet sets and target surfaces of the unbalanced magnetic field of sputtering systems. In L18 orthogonal experiments, the effect of control factors were explored such as gap distance between magnet set and target surface (GDMT), target current, argon and nitrogen flow rate, DC pulse frequency, and work distance. Hardness and wear behavior of the CrN films were analyzed using a statistical method. The wear rate was estimated by Pappus’s theorem. Among the results, the Cr2N phase with the mixture crystallographic orientations of (111) and (002) exhibited better wear resistance than CrN(200) with a single preferential orientation. In addition, variance analysis exhibited the largest percentage contribution to friction coefficient in comparison with the other two properties of friction coefficient and GDMT, which showed that GDMT is extremely sensitive to friction coefficient.

Abstract: To evaluate the efficiency of drilled cooling in the valve bridge of cylinder head, theoretical analysis for the drilled cooling is carried out, and a mathematical model for the enhanced cooling is presented based on a simplified 3D model. The mathematical model is validated by numerical study on the heat transfer with and without drilled cooling, which is carried out through fluid-solid coupling. The correlation between the velocity in the drilled passage and heat transfer coefficient was also analyzed. The results can be used to solve the heat transfer in enhanced diesel engine.