Advanced Materials Research Vols. 69-70

Abstract: Air bearings had been widely used in ultra-precision machine tools. In order to suppress the micro-vibration caused by air bearing, an effective way is keeping the air flow in laminar state. Porous bearing to control the micro-vibration was proposed in this paper, and the related experiments show that it can meet the requirement of decreasing the micro-vibration to less than 1nm, and the surface of diamond surface can be improved.

Abstract: This paper aims to investigate the performance of narrow beam machined by MWEDM. The narrow beam machining experiments are carried out on self-development Micro-WEDM with Φ30μm electrode wire. Narrow beams with the width around 10μm are machined on E52100 steel under different machine conditions (discharge energy, servo reference voltage). Based on the analysis of the experiments results, the coupled temperature and stress analysis using ANSYS finite element analysis software is performed to investigate causes of the failures on process.

Abstract: The interaction between the tungsten steel surface and the polishing fluid & abrasive were discussed by AFM, SEM and XRD test in order to compare the chemical performances and mechanical action of the tungsten steel polishing in the paper. The chemical mechanical polishing (CMP) and the mechanical polishing (MP) was employed, respectively. The experiments results indicated that the CMP with a higher the materials removal ratio than by MP. Because a chemical corrosion effect implies that slurries with the highest removal rate have high dissolution rate, and have a lower the residual stress, however the surface took on wrinkling.

Abstract: This paper presents a finite element (FE) modeling of the nanoindentation test of sapphire, in which the finite element method was employed to study the mechanical characteristic of sapphire under the nanoindentation process. The results demonstrated that the nanoindentation FE models were able to simulate the indentation loading-unloading curves of the sapphire. The load and unload displacement curves of the simulation and experiment results can match with each other well, and then the properties used in the simulation should be the actual properties of the sapphire. The Mises stress field distribution of the sapphire sample was calculated to reveal the alteration from elastic region to plastic region, which are useful for indentifying the ductile to brittle change in the sapphire abrasive process.

Abstract: The most typical example of hard and brittle material is advanced ceramics, for its ultra-precision machining difficulty and wide applications, now it becomes a focus of attention. Semi-fixed abrasive plate (SFAP) is newly developed tool for machining advanced ceramics; As a result of SFAP abrasion, a gradual change takes place in the SFAP topography to influence on machining results and productivity. The paper shows experiment procedures to evaluate SFAP abrasion rate and workpiece material removal. The results of experiments are discussed and analyzed, it indicates that wet status of SFAP have great influences on the removal rate and SFAP abrasion. Compared with dry status of SFAP, wet status of SFAP can achieve higher processing efficiency.

Abstract: To obtain high surface quality and high finishing efficiency in machining SUS440 stainless steel, a novel machining technology employing a semi-fixed abrasive plate (SFAP) is adopted. The SFAP is developed for preventing lapped surface from damage caused by larger particles (from grain size dispersion or from outside of processing area, larger particles could bring uneven load distribution on processing region). The effects of different parameters on the surface quality and the material removal rate (MRR) of SUS440 stainless steel which is lapped by SFAP are investigated in this paper. The control parameters of the lapping process include the lapping time, the load, the rotating speed of the lapping plate, and etc. SFAP of 800# SiC abrasive used, Experimental results indicate that SFAP can avoid the large scratch effectively and the surface roughness (Ra) of the workpiece could be improved from 250 nm to 50 nm in 12 Min. A nearly mirror-like surface can be obtained.

Abstract: Owing to the large photo energy, 157nm laser is considered as one of promising micro-fabrication tools. In this paper, a micromachining system based on the 157nm laser is introduced. 2D laser direct-writing and 3D micro-structuring experiments are carried out for silica glasses, fibers and diamond. For natural diamond, the ablation threshold by 157nm laser is about 2.0J/cm2. Material removal is dominantly due to photon-chemical effect for 157nm laser ablation. Effectiveness of using 157nm laser for 3D micromachining is clearly demonstrated.

Abstract: An experiment, which is based on a self-developed pure tungsten high aspect ratio scanning probe, was conducted to measure the topography of a micro channel and a complex microstructure respectively. Comparison and analysis of both results by the tungsten probe and a single-crystal diamond probe were carried out. It indicates that the newly developed pure tungsten scanning probe has the capability in topography measurement, particularly fit for the high aspect ratio surface measurement.

Abstract: The orthogonal test of surface roughness in ultrasonic polishing nano-ZrO2 ceramics was carried out in the present paper. Through the test, the influence of machining parameters on the surface roughness was investigated. The test results showed that the influence of abrasive size on surface roughness is the most remarkable, and the other important factors are the depth of cut, on/off work situation of ultrasonic generator, axial feed speed, and working table speed in turns. Furthermore, through the regressive analysis of test data, an empirical formula of surface roughness was established to select reasonable polishing parameters.

Abstract: Precision machining, named ‘elliptical vibration cutting’, and its application to ultraprecision / micro machining of some hard / brittle materials are introduced in the present paper. The elliptical vibration cutting has a superior cutting performance in terms of low cutting force, low cutting energy, low heat generation, long tool life for steels, sintered tungsten alloy, etc., and large critical depth of cut for ductile machining of brittle materials such as glasses and single crystal calcium fluoride, etc. Based on these basic advantages, practical ultraprecision / micro machining of the hard / brittle materials is successfully realized by employing the ultrasonic elliptical vibration tools, which have been developed for ultraprecision machining.