Stress analysis and experiment on a split-type ultra-high-pressure die for synthesizing diamond.

In order to obtain a higher pressure-bearing capacity and a larger sample volume and prolong the life of the high-pressure die, a novel high-pressure die for synthesizing gem-grade diamond is investigated with the finite element method. This device is the split-type die, and the cylinder is a combined type. Furthermore, this paper studies the stress distribution of the split-type cylinder and compares it with that of the traditional belt-type die. According to the simulation results, the split-type cylinder has much smaller stress than that of the belt-type cylinder, and it can bear much higher pressure. Meanwhile, the experimental tests also show that the high-pressure die with a split cylinder has a stronger pressure-bearing capacity than the belt-type die. Apart from that, the split-type cylinder has a better performance in easy manufacturing, strong pressure-bearing capacity, and replaceable performance.

Investigation on Bidirectional Pulse Electrochemical Micromachining of Micro Dimples.

Through-mask electrochemical micromachining (TMEMM) is a promising method to prepare micro dimples on the surface of metallic parts. However, the workpiece is machined one by one in traditional TMEMM. This paper introduced bidirectional pulse to TMEMM to improve the machining efficiency. Two masked workpieces were placed face to face, and connected to the ends of the bidirectional pulse power supply. Along with the change of the pulse direction, the polarities of the two workpieces were interchanged periodically, and micro dimples could be prepared on both workpieces at one time. The simulation and experiment results indicated that with bidirectional pulse mode, micro dimples with same the profile can be prepared on two workpieces at one time, and the dimension of micro dimple was smaller than that with unidirectional pulse mode. In bidirectional pulse current, the pulse frequency and pulse duty cycle played an important role on the preparation of micro dimple. With high pulse frequency and low pulse duty cycle, it is useful to reduce the undercut of micro dimple and improve the machining localization. With the pulse duty cycle of 20% and pulse frequency of 10 kHz, micro dimples with etch factor (EF) of 3 were well prepared on both workpieces surface.