Abstract: Ultrasonic machining has been proven to be a promising machining method on hard and brittle materials. However, due to the absence of high power ultrasonic machine tools, reported studies on ultrasonic machining were mainly concerned of relatively small hole drilling of the given materials. In the present work, with the development of the higher power Rotary Ultrasonic Machine Tool, two kinds of ultrasonic face machining with free abrasives, namely, Non-rotating Ultrasonic Machining with Free Abrasives (NRUSM) and Rotary Ultrasonic Machining with Free Abrasives (RUSM) are designed and comparatively conducted for the red granite, which is a typical hard-to-machine natural material. The effects of static force, spindle speed and amplitude of ultrasonic vibration on the performance of the machining are evaluated in terms of the material removal rate and surface quality. Experimental results indicate that ultrasonic machining is effective for face milling of the stone material with the designed machine tool. Furthermore, machining performances in RUSM are superior to those in NRUSM.
Abstract: Ultrasonic assisted electrical discharge machining (USEDM) is one of hybrid machining methods based on the EDM process. The effects of ultrasonic waves on EDM process were analyzed and the experimental investigation of productivity of steel induced by USEDM was reported. Results indicated that ultrasonic waves and cavitation played an important role in improving the flushing and machining efficiency during USEDM. And the material removal rate of EDM assisted by ultrasonic waves was improved greatly.
Abstract: The sawing characteristics of a diamond circular blade with grits set in ordered distribution were investigated in comparison with a conventional blade on which grits are of random distribution. The two blades were tested under the same sawing conditions. Forces and power were monitored during sawing. The results indicate that the changing tendency of sawing forces and power versus sawing parameters are basically same for the two blades. However, the setting of grits in ordered distribution leads to lower sawing forces as well as force ratio, and can reduce nearly one third energy consumption.
Abstract: The grinding heat is utilized to induce martensitic phase transformation and strengthen the surface layer of alloy steel by raising surface temperature higher than austenitic temperature and cooling quickly. The surface residual stress is an important factor to evaluate the quality of surface hardening layer effectively. The experimental values of residual stress in the surface hardened layer are achieved by using X-ray diffraction method and corrosion stripping method. The numerical values of residual stress are simulated by using re-meshing and finite element method. The simulation values trend of residual stress in surface hardened layer is consistent with experimental results.
Abstract: Simulation of the dynamic characteristics of micro abrasive water jet (MAWJ) is conducted using computation fluid dynamics (CFD) software Fluent 6.3 flow solver. The velocity distributions and particle behaviors of the free jet and impinging jet in and out of the nozzle are investigated under different input and boundary conditions. In the free jet simulation, a reduction in water pressure corresponds to more rapid decay of the jet velocity along the jet axis, whereas particle mass concentration has no influence on the jet velocity. In the impinging jet simulation, the effect of the impingement surface on the flow field increases with a decrease of the stand-off distance. The simulation results in this study provide the foundation for optimizing the nozzle structure and improving cutting efficiency and cutting performance of MAWJ.
Abstract: The application of the wheel used in super-high speed point (SHSP) grinding is introduced in detail, depicting the applied rang of the wheel, through designing the wheel body and the layer of CBN in the wheel. The designed principle is inferred according to the specific shape, the grinding productivity is analyzed in the course grinding zone and the finished grinding zone, introducing the angle of course grinding zone, which affects the grinding parameters in SHSP grinding, the value of the angle is designed to be suited to the point grinding, and manufacturing the wheel, introducing the changed state of chip flowing grinding used in the new wheel, the micro-surface of the wheel is observed through microscope, whose the ratio of air hole and the layer of CBN are analyzed, simulating the wear trend of the new wheel, the conclusions about super hard abrasives and wearing are drawn at last, the application of SHSP grinding is related to designing and manufacturing of the wheel, which provides the equipment for realizing high precision and productivity processing and offers the referred basis for the theoretical research.
Abstract: Grinding chatter is a hazardous phenomenon that frequently occurred during grinding process. The topic takes radial ultrasonic vibration honing as an example to explore the dynamic changes of grinding force in ultrasonic honing process. By analyzing obtains the following conclusions: (1) The friction coefficient between work-piece and whetstone is a nonlinear time variable; (2) Adding radial ultrasonic is mainly to change the positive pressure between whetstone and work-piece, thereby affects the mutual friction between work-piece and oilstone in honing; (3) Whether ordinary honing or ultrasonic honing, friction dynamic changes along with time, performance of whetstone relative to work-piece is discontinuous sliding —jerking motion.
Abstract: In the manufacturing process of ultra large scale integrated circuits (ULSI), chemical mechanical polishing (CMP) has already become a practical and main planarization technology because of its global and local planarization ability. The non-uniformity of material removal on wafer surface is one of important indicators of surface precision in wafer CMP process. In this paper, According to the σ calculation method, the calculation equation of the non-uniformity of material removal was put forward. Then, the CMP experiments on the non-uniformity of material removal were conducted under different rotational speed on a CMP machine CP-4. The WaferCheck-7200 equipment, with the theory of non-contact capacitive thickness measurement, was used to detect the thickness of each point on silicon wafer surface. After calculation, the non-uniformity of material removal on the silicon surface was obtained under different polishing speed. The test results can provide some theoretical guide for further understanding the form mechanism of the non-uniformity of material removal and the material removal mechanism in wafer CMP.
Abstract: Maths model based on wo-dimensionalhas was built to simulate the velocity and pressure field of the growth of diamond film. Firtstly，the plasma jet flow is supposed as steady state incompressible gas, which meets with Reynolds-averaged Navier–Stokes equations. The model of the growth of convex diamond film considers different convex height of Mo substrate. The velocity and pressure field were simulated by CFD respectively.The simulational results show that, the distributions of velocity and pressure fields were fluctuant in reaction chamber. When convex height of Mo substrate was 9mm, DC plasma jet was smoother than the other heights, thus, we predicts that diamond film easily grows. Meanwhile, we prepared four diamond films in different heights of substrate, by DCPJCVD. Raman spectra were used to investigate the quality of convex diamond film. It was found that, when the height of convex substrate was 9mm, convex diamond film had only diamond characteristic peak. It is obvious that numerical analysis help us predict the distributions of velocity and pressure fields and synthesize high quality convex diamond film.
Abstract: This study was focused on the theoretical modeling and numerical simulation about the unbalanced response of spindle system of ultra-high speed grinder. Based on the rotor dynamics, a theoretical model was established using the transfer matrix method. The moment balance equations, and the transition matrix, the state vector, field matrix of spindle system of ultra-high speed grinder were analyzed and calculated. The results showed that the amplitude of unbalance response increased by the same multiple as that of the amount of unbalance at different locations and at different speeds. Furthermore, the first order amplitude increased first and then decreased, and the maximum unbalance was located at the middle of the rotor; second order amplitude decreased first and then increased, and the maximum unbalance was located at the front end of the spindle; the third order amplitude decreased first and then increased, and the maximum unbalance was located at the back end of the spindle.