Applied Mechanics and Materials Vols. 423-426

Abstract: Fuel cells heat dissipation and cooling is a vital part of PEMFC heat management. This paper used pure water as the coolant to control the temperature distribution inside fuel cells. Established cooling channels geometrical model and simulated the temperature distribution in the steady state by using software SINDA/FLUINT. Then discusses the effects of cooling channels branch quantity, diameter and coolant velocity on fuel cell internal temperature distribution, concludes that multi-branch, large diameter pipes and low-velocity coolant make PEMFC work at best conditions.

Abstract: With the continuous development of LED(Light-Emitting Diode) manufacturing technology, the high power white LED is gradually applied in the field of all kinds of lighting .But with working time increasing of LED chips, their junctions temperature continue increasing, which lead to decrease light-emitting efficiency and reliability of LED chip, and even be failure. According to the serious heating of LED chip, this paper has been designed a fin-type aluminum radiator panels using Pro/E software. A LED constant current drive circuit is designed by using LTC3783 chip. With the ANSYS software, thermal analysis was carried out on the fin-type aluminum radiator panels, and eventually the mode of high power LED headlamps is determined. The stability of the LED constant current drive circuit is verified through experiments. The LED headlamps of 90W worked for ten hours, and the results of the experiments showed that the LED chip junctions temperature measured are less than 75°Cso we can solve heat dissipation of high power LED headlamps effectively.

Abstract: A qualitative proof of diamagnetic non-zero magnetization based on the electromagnetic induction law is presented in this paper. Modeling diamagnetic phenomena as a result of Larmor precession or effect of the electromagnetic induction’s law in scale of one hydrogen-like atom performed in classical physics contributes to formation of obviously incorrect idea of the diamagnetic magnetization process in students. It is well-known that the average magnetic moment of a diamagnetic calculated with the help of classical statistics laws is zero which can be explained by quantum character of magnetic phenomena. On the contrary, electromagnetic induction’s law is effective both in classical and quantum physics. Applying it to the diamagnetism problem will allow to solve it for the diamagnetic in whole and to avoid averaging which is proved in the present paper.

Abstract: Power supply for micro-system such as wireless sensor network node (WSNN) is an open and interest issue. In this paper, the principle of power self-generation device based on mechanical vibration transformation is introduced, which absorb the energy of mechanical vibration and transform to pressure on piezoelectric materials to produce micro-current, and a mechanical frequency-adjustable vibration absorber based micro electricity self-generation device is designed.

Abstract: Through analyzing the working principle of the technology of maximum power point tracking in the photovoltaic system, the maximum power tracking circuit is designed. In the hybrid energy storage devices of the super capacitor and battery, the super capacitor is a secondary storage device. Through photovoltaic controller is connected with the photovoltaic cells, photovoltaic cells can achieve the status of the maximum power point tracking. Through the bi-directional DC-DC converting circuit connecting with the battery, the battery can effectively decrease the times of the charging and discharging and works stably. It improves the working efficiency and life of the system.

Abstract: Operating characteristics of small and medium tonnage lattice boom crane which withstand fatigue loads was analyzed in this paper. It showed that the lattice boom crane utilization level is in the overlap zone of low cycle fatigue and high cycle fatigue. There may be some plastic deformation in the structure. So the total damage calculated by the Palmgren-Miner rule had a large scatter. Typical operating conditions was analyzed that K-type welded joints of the boom is under axial load and in-plane bending loads. Several critical areas of K-type welded joints were determined by ANSYS finite element calculation software where the stress amplitude was larger on the single side of the lattice boom. A new stress spectrum acquisition method based on the “measured+statistics+compare+simulation” integrated strategy of crane K-type welded joints was proposed. Based on a simplified Huffman non-linear cumulative damage theory, fatigue life of crane K-type welded Joints were calculated based on the strain parameters. They were compared with Palmgren-Miner rule and together with fracture mechanics method. Results showed that although they were all conservative compared with test results, the new method can be applied easily in for engineering applications because it only need amplitude constant amplitude fatigue strain-life data.

Abstract: The doubly fed induction generator (DFIG) can alter speed of the rotor according to change of the wind speed, then contains the maximum tip speed ratio, in order to capture the maximum power from the wind energy. This paper studys the maximum wind energy capturing of DFIG. The fuzzy controller here is used to control the doubly fed induction wind generator in order to improve the robust of the system. We established a fuzzy control rule according to the maximum power capturing. The fuzzy controller captures the maximum power with generator power output error and generator rotor speed error to generate reference speed, which contains the maximum tip speed ratio. The theory analysis and simulation results based on MATLAB / Simulink demonstrate that this control strategy is convenient and efficient.

Abstract: This study was aimed to investigate dynamic characteristics of a milling machine with horizontal spindle tooling system, which was feed through the linear feeding mechanism combined with the sliding guides and linear roller guide modulus. To predict the dynamic characteristics, we created finite element model of the milling machine with the introduction of the contact stiffness defined at the sliding and rolling interface, respectively. The results of the finite element simulations reveal that linear guides with different preloads greatly affect the dynamic responses of the horizontal spindle tool. The maximum dynamic compliance can be increased by 7.4 % in X-axis direction and increased by 12 % in Y-axis direction, respectively when the linear guides are changed from low to high preload. Overall, current results clearly illustrate that the proposed modeling approach of feeding mechanism can quantify the preload effect of the guideway system on the dynamic performance of a milling machine.

Abstract: The mathematical model of sphericity error under the condition of minimum zone is derived. An algorithm based on the differential evolution (DE) is proposed to evaluate the sphericity error. Its principle and realization approach are discussed to solve the minimum zone sphericity error. The proposed method was verified by an example. Compared with other methods, the results show that the proposed method makes the sphericity error evaluation more accurate.

Abstract: A novel method is developed to design the capacity buffer for critical equipments in a production system with unexpected mission arrival, which can assist the staff to control the fluctuation in production schedule. Specifically, the processes of urgent mission arrival and procession are investigated to analyze the regulation and features. A graphic model is established to reflect the transformation between production nodes. An algorithm is designed to calculate the capacity buffer and a case is conducted to verify the feasibility and applicability feasibility of the method.