Papers by Author: Dong Hui Wen

Abstract: Thin-walled spatial bending tube can not only provide engineering design with higher flexibility and lighter structure, but also enhance the construction of space saving and aerodynamics improvement. Based on rotary draw bending technique, a new method for spatial consecutive bending with no straight line for thin-walled tube was put forward. Firstly, a new bionic elastic mandrel was developed by analyzing the structural characteristics of the squilla. It mainly consisted of bowl-shaped mandrel balls, an elastomer and a mandrel shank. The bowl-shaped mandrel balls, nested matching one another, generated a non-smooth surface which can provide continuous support for internal surface of the tube wall. It could also achieve small bending radius. The elastomer featured of certain bending stiffness and enough tensile strength. Secondly, a curved clamping die was advanced to clamp the spatial consecutive bending tube with no straight line effectively. Based on the shape of the bending tube after the former bending forming process, the curved clamping dies which can match the shape of the former bending tube were designed for the later bending. Lastly, bending experiments was performed. A thin-walled tube made of Q235 with two passes, one bending angle 90° and the other 180° was taken for example and the spatial consecutive bending tube with no straight line was successfully obtained. It is of significant importance in enriching the spatial bending tube technique and achieving the small bending radius.

Abstract: This paper summarizes the performance of PEMFC catalyst layer. The main materials used as catalyst in PEMFC are presented as well as the typical structure of MEA. Functions of catalyst during the operation of PEMFC are discussed in detail. Catalyst plays a key role in accelerating the rate of electrochemical reaction, especially that of reduction with oxygen in cathode. But its high cost and low tolerance for has resulted in a severe fact that essentially all the longevity of PEMFC which adopts precious metal-platinum or platinum alloys as catalysts is relatively short. A sputter deposited method is presented to enhance the efficiency of catalyst in PEMFC, while whether this method would bring about a striking effect or not remains worth further researches.

Abstract: This keynote paper aims at introducing applications of ultrasonic radiation force in industry. The chosen focus is to understand how to use it. Since the phenomenon of acoustic levitation can reflect the exciting of ultrasonic radiation force directly. The paper starts with an analysis on the tungsten ball floating on a sound field and ultrasonic micro-manipulation study in micro Electronic Mechanical System (MEMS). And ultrasound has been successfully used to degrade wastewater as its cavitation. At the same time, different kinds of micro-ultrasonic machining were used to show how exciting machining and ultrasonic radiation combined. A view from the authors and the final Conclusions show future applications of ultrasonic radiation force.

Abstract: Cutting forces generated in broaching have a direct influence on the generation of heat, tool wear or failure, quality of machined surface and accuracy of the work piece. In this paper not only a cutting forces test scheme has been proposed but also a cutting forces measurement equipment has been designed with PCB 740B02 dynamical strain sensor and LMS SCADA III test system, respectively. Dynamical strain sensor was pasted on the cylinder type sensitive elements with which table and workpiece was connected. Experimental investigation on the dynamic cutting forces in the broaching direction of a hydraulic broaching machine had been carried out. Cutting forces measurement tests on Q235 steel workpiece material during broaching had been performed. Broaching in a variety of velocities, namely, 3.3m/min, 5m/min and 8m/min and in a variety of cutting depth, namely, 0.03mm, 0.04mm, 0.05mm and 0.07mm, were investigated. Output signal was analyzed both in time and frequency domains and the key characteristics of the cutting forces signal was obtained. Correlation between the frequency of broaching forces and the broaching velocity was also studied.