Advanced Materials Research Vol. 1027

Abstract: Micro-abrasive water jet technology for deburring is a new type of removing burrs technics with advantages of high productivity, high flexibility, no cutter damage and less residual damage etc, which is applied more and more extensively. This paper introduces the difference of premixed micro-abrasive water jet and post-mixed micro-abrasive water jet on jet formation, the difference of system principles and applications. This paper also provides the formula that how to quantitatively calculate the impact force of water jet. The principles and factors which influence on deburring and some application examples are also described in this paper.

Abstract: An attempt is made here to analyze the effect of the process parameter and shoulder of tool on the surface topography of FSJ (friction stir joining) joint. It is found that, it is a linear relationship between the feed speed and arc lines spacing, and the slope decreases as feed speed increasing. As the rotational speed increasing, the arc line spacing reduces. While FSJ processes completed at different parameters contain the same ratio between the feed speed and the rotation speed, the arc line spacing of the joint surfaces is the same. The shoulder of tool can increase the width of joint lines, refine arc lines structure, reduce the flash in the retreating side, but increase the flash in the advancing side.

Abstract: The micro and nano burr removing mechanism of precision surface of the nano-ZrO2 ceramics were investigated. The ultrasonic vibration finishing experiments showed that the critical ductility finishing depth of the ceramics was 3μm by conventional finishing, but the increment of the critical ductility finishing depth was 50 percent by ultrasonic finishing. The critical ductility finishing depth increased to 6μm. Analyzed by means of SEM, it was transgranular cracking during the micro-nano burr removing process. The nano-ZrO2 ceramics have high toughness so the critical ductility finishing depth increased. The shape, length, width and thickness of the finishing differed greatly from that obtained by conventional finishing.

Abstract: Surface modification has become a common method to improve the interface property of electrodes. The existing problems on the interface of implanted electrodes are introduced in biocompatibility, corrosion resistance, electrochemical properties in this article. Iridium oxide is the most widely used material for implanted bio-electrodes because of its good biocompatibility, corrosion resistance, high safety injection charge density and low impedance. And preparation methods of the iridium oxide modifying bio-electrodes are described and discussed for enhancing the long-term implanting stability of the bio-electrodes.

Abstract: The uniform temperature flied of substrates is a key factor to deposit high-quality diamond films on milling tools by the hot filament chemical vapor deposition (HFCVD). In this study, a 3-D computational model is established to simulate the temperature distribution on the substrates. Thereafter, the influence of the rotational speed of worktable n and the water flux of water-cooled worktable Q are investigated. The simulation results show that the increasing of the rotational speed of worktable is suitable to grow homogeneous diamond films and gently decrease the even temperature of seals. What’s more, the deceasing of the water flux will significantly increase the overall temperature of seals.

Abstract: The developing high-power laser systems are requiring higher laser-induced damage threshold (LIDT) and fabrication efficiency of fused silica optical elements. To solve these problems, MRF polishing and HF etching have been combined utilized wiping and passivating structural defects as well as removing impurities. Furthermore, the LIDT improvement is dependent greatly on the corporation of processes. But the LIDT improving mechanism is partly ambiguous yet, that may lead to random or experimental parameter choice and ultimately generate unsatisfied results. Consequently, this paper focuses on the termination mechanism of the process. Atom Force Microscope (AFM) measurement, finite difference time-domain (FDTD) simulation and LIDT test will be utilized to analysis and validate the optimization theoretically and practically. Finally, in one side, the LIDT value of optimized-terminated sample is 16.7J/cm², which is about the same level (even 3.7% higher) as that of the over-etched one. In another side, the etching process time could be shorted by 32% using the optimized method.

Abstract: Aiming at the quality problems of ‘over polishing’ and ‘insufficient polishing’ in the process of traditional extrusion abrasive flow machining,An abrasive flow polishing method at the constantly small pressure difference is developed, the hydraulic proportional control system is designed, and the mathematical modeling of the hydraulic proportional control system for small pressure difference constant extrusion polishing abrasive flow machining is set up. The simulation results show that the polishing pressure can be well controlled and the stability of polishing velocity is improved, which will improve the extrusion abrasive flow polishing quality.

Abstract: In this study, according to physic-chemical characteristic of the SiC crystals, we analyzed and researched the role of pH modifier in SiC crystal substrate chemical mechanical polishing and the surface after polishing. We used different polish agents which was made up with inorganic and organic bases to experiment, and then analyzed the results. The parameters of the polishing specimen, such as the removal rate of material, surface scanning and the roughness, were analyzed and used to determine the different pH modifiers played different roles in the stability of polish agents and surface quality of the specimen.

Abstract: Chemical mechanical polishing (CMP) had been considered as the most practical and effective method of achieving an ultra-smooth and non-damage surface in manufacturing SiC crystal substrate. CMP slurry was one of the key factors of CMP technology. In this paper, through investigating the changes of several core factors to evaluate the performance of CMP, such as the material removal rate (MRR), surface roughness Ra, 3D surface profiler, etc., the influence of various slurry and its content on the polishing efficiency and surface finish quality had been studied. The research results showed that different oxidant had different chemical action mechanism, also affecting the stability of CMP slurry and surface quality of specimen; adding suitable an oxidant to slurry could effectively improve the CMP performance.

Abstract: Cutting-direction burr/fracture is one of the important factors that influence the edge quality and performance of precision parts. The formation of negative shear zone decisions the edge quality of workpiece. A finite element model has been established to investigate the mechanism of negative formation in machining H64 brass. The negative shear zone formation process is simulated with rigid-plastic nonlinear finite element method. The cutting direction burr forms when the stress of principal shear zone great than it in negative, the cutting direction fracture forms when the stress of principal shear zone less than it in negative and there is a crack in the area near the tool tip and grow along the negative shear zone .