Abstract: Recently, the key obstacle of proton exchange membrane fuel cell (PEMFC) development is the higher manufacturing cost. In a PEMFC stack, bipolar plate is a main and multifunctional component, which accounts for the 60%-80% of total weight and 30%-45% of stack cost. So the forming cost of bipolar plate will influence the entire PEMFC manufacturing costs. Metal bipolar plate, which can satisfy the requirement, can be used for mass production to reduce the cost. Finite element analysis (FEA) of stamping and springback for metal bipolar plate is studied by ANSYS/LS-DYNA to be feasible.
Abstract: The ZK60 magnesium alloy sheet butt-welded in gas tungsten arc welding with different heat input are analyzed and simulated. A double-ellipsoid heat source and the temperature-dependent thermo-physical properties of ZK60 magnesium alloy sheet are employed for performing a non-linear transient thermal analysis by a finite element method. The effect of heat input on welding seam geometry has been studied. As a calculated result, the welding voltage, welding speed and the welding current are the main factors to determine the welding seam geometry. The different welding temperature fields between the general gas tungsten arc welding (GTAW) and GTAW hybrid a longitudinal electromagnetic field (LMF-GTAW) have been achieved.
Abstract: Helical milling is used to generate holes, in which a tool attached to the rotating spindle traverses a helical trajectory, and the diameter of holes will be larger than that of the tool. Based on the principle of helical milling, this paper establishes analytical model of cutting forces. As the cutter travels on the helical path, intersection between the tool and the workpiece changes continuously, in which chip thickness and direction of the cutting forces will vary simultaneously. The cutting forces are not only direct proportional to the axial depth of cut, but also related to the rotational speed and orbital speed of the tool. Cutting experiment is conducted for the titanium alloy. The result shows that the simulated cutting force can be used to predict the change of cutting force under different conditions.
Abstract: Carbon fiber reinforced plastics (CFRP) has been widely used in airplanes, spaceships and automobiles. The cutting performance of CFRP with a fiber orientation of 0/45°/90°/135° has been studied at different cutting parameters by using PCD tools. Experiences subjected to orthogonal cutting were performed to investigate the effects of cutting parameters on cutting force, surface finish criteria (delamination) and roughness. Results show that CFRP can be milled by high speed and can get good surface quality with low delamination by using PCD tool. The cutting force decreases under the condition of decreasing the cutting width as well as the feed per tooth and raising the cutting velocity. The cutting force is a key point to control delamination that it should below 200N to get comfortable result. As for roughness, when the cutting force below 250N, the more cutting force, the higher surface roughness, and the trend changes when cutting force over 250N. The relation between cutting force and delamination, cutting force and roughness are obtained respectively through multiple regression analysis.
Abstract: This paper proposes a novel bipolar plate flow field of PEMFC with the intersectant microstructure. Numerical simulation about both the flow velocity distribution and the pressure distribution for the reactive gas were accomplished according to the model building by Pro/E, grid meshing and boundary condition specifying by Fluent. Compared to traditional serpentine flow fields, the gas pressure difference between the inlet and the outlet of this novel flow field is appropriate to promptly discharge the water produced during the operation of the PEMFC, and the flow velocity of the reactive gas among all the flow field is well-distributed, which assures reactions occurring uniformly in the flow field under the bipolar plate. All the properties of this novel flow field make a great sense to improve the integrated performance of the PEMFC.
Abstract: The effect of quenching temperature on the microstructure and mechanical properties of 40Cr steel by zero time holding quenching were studied. The results showed that the strength and hardness of 40Cr steel increased with the increase of quenching temperature in the range of 860~940°C, the strength and hardness reach the maximum at 920°C and then decrease. The metallographic analysis shows austenite grains of the samples by “Zero Time Holding” Quenching have been refined compared with the traditional heat treatment technology. Fine lath martensite was obtained by the “zero time holding” quenching due to the smaller austenitic crystal grain and the uneven distribution of the carbon concentration in austenitic crystal grain.
Abstract: In view of the problems that Security personnel who faced with an emergency response can not be timely in the process of duty, we propose and establish a monitoring system based on active RFID technology. The system uses active RFID Reader and the communication protocol between Reader and the host computer to monitor the status of security personnel. Tag’s configuration allows more flexible application of the tag and we can use the configuration to change the parameters of the tag. The tag's size is small and it has flexible applicability and strong adaptability. Test results showed that the tag’s test frequency can be controlled to 10HZ and 400HZ, and monitoring can also set their own threshold. The rate of Reader is 100%, and the tag can launch to about 100 meter. The system not only solves security system faced with an emergency problem, but also for long distance transmission of RFID provides a theoretical basis.
Abstract: For solving the problem of drill breakage and increasing productivity, a built-in adaptive drilling control scheme has been proposed. The torque of the spindle detected using a floating torque measuring mechanism has been regulated by controlling the feed rate of the spindle using PID control algorithm. The adaptive control algorithm has been integrated into a numerical controller. Motor control functions are performed in a timer interrupt subroutine to realize real-time parallel processing. An experimental system has been established. Experiments have demonstrated that the system is applicable in preventing drill breakage and increasing productivity.
Abstract: Numerical control milling machine with a special transformation can be achieved the involute path processing functions. By using Fan method to process a way to synthesize involute track requirements and involute contour processing. This method is particularly suitable for gear modulus m ≥ 12 ~ 40 of the big modulus gear machining, and omit the big modulus gear-specific complex tool manufacturing. Another advantage is that as the basic parameters of the coordinates programming trajectory calculation as a way to carry out involute trajectories run control, gears accuracy can be effective control and assurance. Furthermore, it can be revised and the edge of the involute tooth surface in the tangential connection.