Papers by Keyword: Ultrasonic Vibration

Abstract: In the present research work, a new precision sawing technique is proposed, by which the ceramic workpiece is ultrasonically vibrated along the blade radial direction during the sawing operation using a diamond blade. In this study, experiments are conducted to study the sawing force characters of ultrasonic vibration-assisted sawing (UVAS) and conventional sawing (CS). The influences of the sawing parameters on the sawing force and force ratio are investigated. The results show that the sawing force in UVAS is smaller than those in CS. It was found that applying ultrasonic vibration to the sawing operation decreased the normal sawing force 18%-38% and tangential sawing force by 10%-25%. The force ratio in UVAS is lower than that in CS, which reveals that diamonds are easier to cut into the ceramic workpiece and the material machinability is improved.

Abstract: In order to achieve a high efficient and high quality EDM of PCD, the authors have developed a new PCD having superior electrical conductivity by using boron diamond as a source material. On the other hand they applied a method to give ultrasonic vibrations to the electrode, and have made it clear that even the standard PCD could be machined at the similar level of efficiency to the cases of EDMing die steels and cemented carbides. With a purpose to obtain a good surface roughness on the PCD at high efficiency, various EDM conditions and methods were compared in this paper. Firstly, influence of discharge duration time was examined, and it was found that a shorter pulse duration time as t_e=0.5μs showed high efficiency and smaller electrode wear rate. Secondary, influence of bipolar pulse current method was examined, and it was found that the method effected higher efficiency but rather large amount of electrode wear resulted. Thirdly, ultrasonic assisted EDM was conducted, and it was found that the method showed superior result regarding efficiency and wear rate on both standard PCD and EC-PCD. A combination use of ultrasonic assisted and bipolar pulse current EDM methods was also attempted in this research. On the contrary to the expectation, efficiency and electrode wear rate became worse in EDM of standard and EC-PCD in comparison with other methods tested before.

Abstract: Hypereutectic Al-Si-Cu alloys which are typical light-weight wear-resistant materials, are required to improve the ductility as well as the strength and wear-resistance for the wider applications. Increase in amounts of primary silicon particles causes the modified wear-resistance of hypereutectic Al-Si-Cu alloys, however, it leads to the poor strength and ductility. It is known that dual phase steels composed of hetero-structure have succeeded to bring contradictory mechanical properties of high strength and ductility concurrently. In order to apply the idea of hetero-structure to hypereutectic Al-Si-Cu alloys for the achievement of high strength and ductility along with wear resistance, ultrasonic irradiation to molten metal during the solidification, which is named sono-solidification, was carried out from its molten state to just above the eutectic temperature. The sono-solidified Al-17Si-4Cu alloy is composed of hetero-structure, that is, hard primary silicon particles, soft non-equilibrium α-Al phase and eutectic region. Rheocasting was performed at just above the eutectic temperature with sono-solidified slurry to shape a disk specimen. After the rheocasting with modified sono-solidified slurry held for 45s at 570^oC, the quantitative optical microscope observation exhibits that the microstructure is composed of 18area% of hard primary silicon particles and 57area% of soft α-Al phase, in contrast there exist only 5area% of primary silicon particles and no α-Al phase rheocast with normally solidified slurry. Hence the tensile tests of T6 treated rheocast specimens with modified sono-solidified slurry exhibit the improved strength and 5% of elongation, regardless of more than 3 times higher amounts of primary silicon particles compared to that rheocast with normally solidified slurry.

Abstract: This paper presents experimental and numerical investigations on the effect of ultrasonic vibration on cylindrical cup drawing processes of a cold rolled steel sheet (SPCC). An experimental apparatus to superimpose high frequency oscillation on deep drawing processes was constructed by installing ultrasonic vibration generators consist of piezoelectric transducer and resonator to the die. Conventional and vibration-assisted cylindrical deep drawing tests were carried out for various drawing ratios, and the limiting drawing ratio (LDR) was compared. In order to evaluate the contribution of ultrasonic vibration to the reduction of friction between tools and a material quantitatively, finite element analyses were carried out. Through a series of parametric analyses, friction coefficients which minimize the differences of punch load histories between the experiment and simulation were determined. The results showed that the application of ultrasonic vibration make for improving LDR by reducing the friction between tools and the material, effectively.

Abstract: The Fe-rich Al-Si alloys have the potential to be used to make wear-resistant parts. However, there has been few work devoted to study the wear behavior of the hypereutectic Al-Si alloys with about 2% Fe (mass %). In this work, the semi-solid slurry of the alloy was prepared by an ultrasonic vibration (USV) process. The effect of Fe content on dry sliding wear properties of the alloys rheo-casted after USV treatment was investigated. The wear tests were carried out using a pin-on-disc wear tester at four different loads of 50N, 100N, 150N and 200N at a constant sliding speed of 0.75m/s. The results show that the wear rate of USV treated alloy increases almost linearly as the applied load increases from 50 N to 200N. The alloys made with semi-solid process exhibited improved wear resistance at the entire applied load range in comparison to the conventional casting alloys. At the applied load of 50N, oxidative wear is the dominant mechanism for the alloys with USV treatment. At 200N, a combination of delamination and oxidation wear is the main wear mechanism. The wear resistance of Al-17Si alloys containing 2% to 3% Fe is closely related to the morphology, size and volume fraction of Fe-bearing compounds, which can be changed by USV semi-solid process.

Abstract: In this study, drilling for nickel alloy was carried out with ultrasonic vibrating carbide drill. Micro drilling is not an easy machining process due to remarkable tool wear, lower stiffness of the tool, difficulty of chip and heat removal from cutting point. Ultrasonic vibration assisted machining has effects of decrease of cutting force, generation of fragmented small chip, extension of tool life and improvement of surface integrity. In this study, ultrasonic vibration drilling for nickel super alloy was investigated to improve the tool life and productivity. The drilling for heat-resisting nickel super alloy was performed with the drill of 0.3mm in diameter. As a result, ultrasonic vibration drilling performed 302 holes with thickness of 2.0mm by applying minimum quantity lubrication to blow off the chips on the flutes. Ultrasonic vibration improved deviation of position of drilled hole because the hammering motion of the chisel edge results in good bite of tool on work surface. The productivity is directly depends on feed rate. The increasing feed rate from 6mm/min to 60mm/min dramatically reduced the tool life one thirtieth under conventional drilling condition. On the other hand, the ultrasonic vibration drilling reduced the tool life only one half.

Abstract: Chemical mechanical polishing (CMP) is often employed to obtain a super smooth work-surface of a silicon wafer. However, as a conventional CMP is a loose abrasive process, it is hard to achieve the high profile accuracy and lots of slurry must be supplied during CMP operations. As an alternate solution, a fixed abrasive CMP process can offer better geometrical accuracy and discharges less waste disposal. In this paper, in order to enhance the polishing efficiency and improve the work-surface quality, a novel ultrasonic assisted fixed abrasive CMP (UF-CMP) is proposed and the fundamental machining characteristics of the UF-CMP of a silicon wafer is investigated experimentally. The results show that with the ultrasonic assistance, the material removal rate (MRR) is increased, and the surface quality is improved.

Abstract: Based on the regularities of motion of the rigid polyurethane rubber ultrasonic vibration assisted grinding, combined with the kinematic analysis of the general theory and experiments. This paper analyses the variation in position, velocity and acceleration during the manufacture of single abrasive grinding with and without ultrasonic vibration. The impact of rigid polyurethane rubber micro V - groove process introduced by the ultrasonic vibration is explored to verify the feasibility of the ultrasonic vibration assisted grinding of micro-precision machining of hard polyurethane rubber material.

Abstract: The hypereutectic Al-17Si-2Cu-1Ni-0.8Mn alloys with 2% or 3%Fe were fabricated out assisted with ultrasonic vibration (USV) treatment. The coarse plate-like δ-Al4(Fe,Mn)Si2 phase was transformed into fine particles with average diameter of about 17μm~20μm after USV treatment, and the volume fraction of particle-like Fe-bearing compounds is about 3.6%~5%. The polygonal primary Si crystals were also refined into particles with average diameter of about 15μm~23μm, and the volume fraction of primary Si declined to about 5.4%~6.5% after USV treatment. The matrixes of the castings were reinforced with fine Fe-bearing compounds and Si particles. The ultimate tensile strength of the alloys, which were produced by gravity casting process assisted with USV, increases with the increase of Fe content at 350 °C. It is considered the increase of the elevated temperature strength of the samples are mainly attributed to the refinement of δ-Al4(Fe,Mn)Si2 phase by USV and the increase of the volume fraction of the Fe-bearing compounds. The die casting process assisted with USV can further improve the mechanical properties of Al-17Si-2Fe-2Cu-1Ni-0.8Mn alloy.

Abstract: The combined effects of the Co addition and Ultrasonic Vibration (USV) on microstructure and properties of Al–20Si–2Cu–1Ni–0.6Mg alloy were studied in this paper. The volume fraction of Co-bearing intermetallic compounds was increased with the increasing of Co content when various levels of Co (from 0% to 1.5%) added respectively into the alloys whether they formed in traditional casting or with USV treatment. The Co-bearing compounds presented as Chinese script or granular when Co was equal or less than 0.7% and turned into dendritic or fish-bone shape when Co was more than 0.7%. USV treatment applied around liquidus temperature of the melt could lead to a refinement of Co-containing compounds by promoting nucleus formation, hindering preferential growth on certain direction, and enlarging solute diffusion coefficient. The addition of equal or less than 0.7% Co, as well as application of USV is very effective in promotion of tensile strength of the hypereutectic Al–Si alloys.