Advanced Materials Research Vol. 1027

Abstract: Ultrasonic machining is an important part of modern processing technology which is adapt to all kinds of hard brittle materials processing. This paper reviews the latest progress of the material removal mechanism on one-dimensional ultrasonic machining, two-dimensional ultrasonic machining and rotary ultrasonic machining, and expounds the development trend of establishing the material removal model of the ultrasonic machining.

Abstract: The pressure field induced by cavitaion bubble is responsible for the grinding mechanism and the cutting chatter of power ultrasonic honing. Based on the cavitation bubble dynamics model in the grinding area of power ultrasonic honing, the radiation pressure field of cavitation bubble was established. Experimental results show that the bubble is distributed in the grinding area like honeycomb and the size is about 10μm. Numerical simulation of dynamics and pressure field of cavitation bubble was performed. Numerical results show the dynamic behavior of cavitation bubble presents grow, expend and collapse under an acoustic cycle. However the expansion amplitude of bubble can be decreased and the collapse time can be extended and even collapse after several acoustic cycles with increasing ambient bubble radius. The bubble radiation pressure during collapsing bubble increases with increasing ultrasonic amplitude and ultrasonic frequency. And the pressure value of collapsing bubble is about 10Mpa which is more an order of magnitude than atmospheric pressure.

Abstract: High volume fraction SiCp/Al composites were grinded in rotary ultrasonic vibration aided grinding in this experiment, exploring the effects of different grinding parameters (grinding depth, grinding wheel speed, feed rate) on grinding force and the material removal mechanism with ultrasonic grinding. The results showed that grinding force of ultrasonic grinding is lower than the ordinary grinding in the same grinding parameters. Studying on material removal mechanism of ultrasonic vibration grinding is bound to have important theoretical and practical significance for the improvement of grinding processes and the development of mechanical according to the advantages of grinding and ultrasonic machining. Keywords: High volume fraction SiCp/Al composites; ultrasonic grinding; grinding force

Abstract: s: Abrasive jet micromachining is considered as a promising precision processing technology for brittle materials such as silicate glass and silicon nitride that are increasingly used in various applications. In this study, some polishing experiments are conducted for hard-brittle materials by a micro slurry jet. The results show that the morphology and the integrity of the material surface are improved greatly after polishing. The average roughness (Ra) value of the silicate glass decrease from 2.32μm to 0.35μm and the average roughness (Ra) value of the Si₃N₄ decrease from 2.63μm to 0.34μm. The material removal mechanism and the surface formation mechanism are studied. The factors to influence the surface morphology, the surface quality and the surface roughness are analyzed in order to take measures to improve the surface quality and reduce the surface roughness value.

Abstract: Chemical mechanical polishing (CMP) is the most effective technology to achieve ultra-smooth without damage surface in ultra-precision machining of stainless steel substrate. In this paper, according to the slurry ingredients obtained by former research, the influences of the CMP process parameters, such as the rotational velocity of the platen and the carrier, the polishing pressure and the abrasive size on the material removal rate (MRR), have been studied in CMP stainless steel substrate based on the alumina (Al₂O₃) abrasive. The research results show that the material removal rate increases with the increase of the abrasive size, the rotational velocity of the platen and the polishing pressure significantly and the surface roughness increases with the increase of the abrasive size. This study results will provide the reference for optimizing the process parameters and researching the material removal mechanism in CMP stainless steel sheet.

Abstract: There are four kinds of ultra-precision lapping machine bed were developed: with/without reinforcing rib, with/without a pair of closed sides. The finite element analysis was used to find the optimal design of the machine bed. The 3D model of the ultra-precision lapping machine bed was built by SolidWorks, and ANSYS software was used for static analysis and modal analysis. The results suggest that when reinforcing rib and a pair of closed sides were owned, the machine bed had some better static and dynamic characteristics. The mix-deformation of this machine bed was 1.911μm, and the first-order inherent frequency was 101.74Hz.

Abstract: The processing technology of sapphire with a high material removal rate a good surface quality is critical for its applications. The experiment of sapphire lapping and polishing was carried out by using three different fixed abrasive pad (FAP). Their material removal rate (MRR) and surface roughness (Ra) were measured and analyzed. Results indicate that a MRR of 5.6μm/min reaches in rough lapping and a MRR of 0.4μm/min in fine lapping. The average surface roughness Ra of rough lapping and fine lapping is 142nm and 1.2nm respectively. The processing efficiency of sapphire wafer is effectively improved and a good surface quality is obtained when FAP adopted.

Abstract: This paper analyzed the large diameter Fresnel lens mold machining mechanism based on modal test methods .The design and mold machining principle of Fresnel lens were introduced . Explored the cutting speed and feed on chip formation process. The results show that: the material strength and plastic brittle have significant impact on chip morphology in the H62 brass mold processing, an improvement of material strength with the increase of strain rate and the evolution process of the chip can be divided into: ribbon cuttings, serrated chips, cell chips.

Abstract: End milling is conducted on carbon fiber reinforced plastics (CFRP) by using a diamond coated cemented carbide tool. Taguchi design method is employed to investigate the influence of cutting speed, feed rate and depth of cut on surface roughness. In Taguchi method, a three level orthogonal array has been used to determine the S/N ratio. Analysis of variance (ANOVA) and pareto diagram are used to determine the most significant milling parameters affecting the surface roughness. The results indicate that only the depth of cut has great statistical significance on the surface roughness, while the influences of cutting speed and feed are negligible. SEM micrographs shows that with the increase of depth of cut, a great deal epoxy resin will adhere to the finished surface. The greatest S/N ratio (1.46dB) is obtained during the validation experiment with optimum milling parameters.

Abstract: Single crystal diamond is widely used in high-tech fields for its remarkable performance on mechanics, calorifics, optics, acoustics, etc. High-quality diamond surface with small roughness and low scathe are required in these applications. However, the extreme hardness and high chemical inertness of diamond result in severe processing difficulties. Chemical mechanical polishing (CMP) is a promising processing method which can obtain super-smooth and low-damage diamond surface. Oxidant is a key issue for CMP of single crystal diamond. In this study, five different oxidants were used to polish diamond samples. The results indicated that Fenton reagent was an appropriate CMP oxidant and a super-smooth diamond surface of Ra 2.4 nm was achieved by using Fenton reagent in CMP.