Papers by Keyword: Polishing

Abstract: The objective of this article is to present the effect of fast prototyping means on the fatigue strength of SAE 1075 steel used for planar springs, which are commonly used in different type of machines. Two cutting processes are used for rapid prototyping those components. The first one, with CO2 laser cutting machines and the second, using Electrical Discharge Machines – EDM. It was also evaluated the effect of applying three levels of finishing processes on the work pieces: tumbling, polishing and shot peening. Fatigue tests were performed using a machine specially developed for this purpose, applying fluctuating loads. An analytic formulation and also the use of Finite Element Method – FEM – were applied in order to obtain the stresses present in the work piece during the load application. The characteristics of the work pieces´ surface, mainly at the cutting edge were analyzed, and so was the microstructure of them near the cutting region. It was found that, mainly in the pieces cut by laser, there is a Thermally Affected Zone – TAZ – composed by bainite with retained austenite, which affects the fatigue strength of the material. It was also found that finishing processes improve the fatigue strength of the material by removing defects introduced by the cutting means, and the application of shot peening introduces the better final characteristics.

Abstract: Pt-modified nickel aluminide coatings have been more widely used for protection of jet-engine components against high-temperature oxidation. The coating rumpling of two Pt-content NiPtAl coatings was studied in this paper during high temperature exposure. The results indicated that the NiPtAl coating grains size made a great contribution to the oxide surface morphologies, especially rumpling. Smaller grain size within high-Pt coating indicated a denser rumpling compared to low-Pt coating due to PtAl2 formation in the earlier coating. The failed local alumina at the ridges was also found on the low-Pt coating after cyclic oxidatioin. It was found that polished treatment resulted a comparatively flat and homogeneous oxide layer compared to as-received coatings. The temperature cycling could promote the aluminide coating rumpling, however, the polished treatment could not completely eliminate the roughening.

Abstract: Large diameter (0.4~0.8mm) fiber termination is widely used in the gum related cares. However, cost-effective shaped fiber is not yet developed for high power (~5W) laser application. In this study, we have demonstrated the feasibility of using two stepping motors with a patented axial movement (0.005mm increments) method. The key parameters are investigated using finite element modeling. The results show that larger fiber diameter with less number of feeding increments can damage the fiber during polishing process.

Abstract: In this study, we developed aA novel abrasive-free polishing method called the catalyst-referred etching (CARE) has been developed. CARE can chemically remove SiC chemically with using an etching agent activated by a catalyst. Platinum and hydrofluoric (HF) acid are used for the planarization of SiC substrates as a catalyst and etchant, respectively. CARE can produce an atomically flat surface of 4H–SiC (0001) with a root-mean-square roughness of less than <0.1 nm, regardless of the cut-off angle. However, the mechanism of CARE has hasis not yet been clarified to date. In this study, to clarify the mechanism, KF and NH4F are added to the etchant to clarify the mechanism. The An investigation of removal rate revealeds that the removal rate is proportional to [HF]×([F^- ]+[〖HF_2〗^- ]), and it is shown that both the HF molecule and fluorine ions (F− and HF2−) arethe reactive species of the CARE process are both HF molecule and fluorine ions (F- and HF2-).

Abstract: The wheel of abrasive belt is a special-shaped coated abrasive which has the advantage of good polishing quality, long life, and high efficiency, low cost and so on. Base on the features of the wheel of abrasive belt, through analyzing the basic motion relation of forming polishing spiral surface screw, the wheel of abrasive belt’s profile shape curve could be calculated by establishing the contact line equation of screw spiral surfaces with the wheel of abrasive belt rotating surfaces. Software to verify the correctness of the profile shape calculated, and in accordance with the wheel of abrasive belt profile shape curve to programming NC program. Start with the dressing experiments of the wheel of abrasive belt. Through analysis and research to get the wheel of abrasive belt’s profile shape curve meet the forming polishing standard.

Abstract: This study examined the surface defects and surface roughness of optical glass polished by mechanochemical machining. BK7 optical glass material was polished using cerium oxide (CeO₂) solutions of different concentrations and temperatures. During machining, the optical glass specimen was placed between the ceramic working ring and the polishing pad. The effects of slurry concentration and temperature, polishing time, rotational speed and axial load on the surface roughness were examined. Significant improvement in surface roughness could be attained by polishing with CeO₂ slurry of 95^。°C. Both SEM and AFM images of BK7 polished under conditions: slurry concentration, 15%; slurry temperature, 95^。C; rotational speed, 40 rpm; axial loading, 6 kg; and polishing time, 8 min show that the optical glass specimen surface had high transmittancy and became smooth with all scratches removed. The best mechanical properties in terms of Young’s modulus of elasticity and hardness were obtained by polishing with CeO₂ slurry of 60^。C. Although better surface roughness can be attained with further increase in slurry temperature, the enhanced reaction under high slurry temperature undermined the mechanical properties of the glass specimen.

Abstract: This paper is to design the NC system for the strengthening and polishing machine. First, it designs the overall scheme of the system on the basis of taking all of the factors into account, and focuses on the injection system include its structure and working principle. Then, it combines with the main control flows in the mode of zero-return, manual and automation, and takes HUST H6C series CNC of Taiwan YITU Co., to deeply research the NC system for strengthening and polishing machine.

Abstract: This paper first analyze effect upon the surface roughness on the bearing outer ring from the jet pressure in the strengthening and polishing process theoretically, and then verify the validation of the theory in experiments, finally, it is concluded that the jet pressure should be reduced and about 0.4MPa for better in the strengthening and polishing process, under the circumstance of meeting the roughness requirements and considering the various factors, so as to lay a foundation to further research the relation between the strengthening and polishing technology and the surface roughness on the bearing outer ring.

Abstract: Three kinds of dental zirconia (Cercon, NANOZR, and P-NANOZR) were ground and polished with seven kinds of clinical device and materials. After these grinding and polishing, the surface roughness and the glossiness were analyzed. The crystal phases of the surface were analyzed with a micro X-ray diffractometer. The results demonstrated that all three zirconia showed the smallest roughness and the highest glossiness when they were polished with diamond-containing polishing pastes. Tetragonal to rhombohedral transformation was observed on the ground and polished surfaces of Cercon and ZENOSTAR, whereas monoclinic phase was also detected on the ground and polished surface of P-NANOZR. The polishing with diamond-containing pastes showed the smallest transformation amount of rhombohedral and monoclinic phases. It is concluded that dental zirconia can be well polished with diamond-containing pastes, and the phase transformation are also reduced.

Abstract: In this study, we investigated the possibility of removing and smoothing a single-crystal silicon carbide (SiC) surface under ultraviolet (UV) irradiation in hydrogen peroxide (H₂O₂) solution. In this method, a SiC substrate was excited by UV irradiation that transmitted synthetic quartz, and then an oxide layer on the SiC substrate was formed by photochemical reaction. Simultaneously, hydroxyl radical (OH*) was generated by the decomposition of H₂O₂ solution by UV irradiation. OH* plays an important role of oxidation of SiC surface. With these chemical reactions, oxide layer was effectively formed on the SiC surface. Finally, the oxide layer generated on a SiC substrate was chemically and/or mechanically removed by synthetic quartz and solutions. The polishing characteristics of this method were investigated by controlling the process parameters. Additionally, surface quality and removal depth were measured and evaluated by a phase-shift interference microscopy. Obtained results show that the surface morphology and the removal rate are strongly dependent on the existence of the UV irradiation. Moreover, it is shown that the removal characteristics of the SiC substrate depend on the process parameters such as the process time, reciprocating speed, and contact load. The processed surface has revealed that many scratches on the preprocessed surface was completely removed. The microroughness of the processed surface was improved to 0.15 nm (Rms) and 1.62 nm (p-v), respectively. These results provide useful information for obtaining an atomically smooth SiC surface.