Key Engineering Materials Vols. 523-524

Abstract: A kind of zirconia-coated carbonyl-iron-particles (CIPs), which show long-time stability against aqueous, is installed in magnetic compound fluid (MCF) to polish PMMA. Performance (normal polishing force and surface roughness) of zirconia-coated CIP based MCF slurry with different CIP concentrations is investigated. For comparison, the performances of the conventional non-coated CIP (i.e., HQ) based MCF slurry and MRF slurry in which DI-water is employed instead of MF are also examined. In the presence of Al2O3 abrasive particles, the use of zirconia-coated CIP based MCF slurry can not result in better polishing performances compared with conventional HQ CIP based MCF slurry; In the absence of Al2O3 abrasive particles, higher normal polishing force and smoother work-surface were obtained with the zirconia-coated CIP based MCF slurry rather than the MRF slurry; For the zirconia-coated CIP based MCF slurry without abrasive particles, the concentration of zirconia-coated CIP should be less than a certain value (in the current work, 70 wt. %), otherwise MCF slurry shows bad particle dispersion and is easily dried, resulting in the loss of its polishing ability.

Abstract: Improving machined surface integrity is one of the important issues in the precision machining. This study aims to develop a cutting tool, which enables to generate a local hydrostatic pressure field in the vicinity of the cutting point to suppress the extra plastic flow in the workpiece, because it is known that materials including metals never cause plastic flow and fracture no matter how much greater hydrostatic pressure field is given. In this paper, a simple cutting tool with planer jig is proposed and a molecular dynamics simulation of cutting is performed as the first step. As a result, it is confirmed that the reduction of the plastic deformation, mainly in the burr formation become remarkable with the proposed model due to the suppression of extra side plastic flow, and relatively high-hydrostatic stress field is formed in the vicinity of cutting point. However, it is also observed that relatively many dislocations are generated beneath the cutting groove.

Abstract: We have developed a novel abrasive-free planarization method, which we term catalyst-referred etching (CARE). In SiC CARE, Pt is used as a catalyst and HF solution is used as an etchant. CARE produces a crystallographically undamaged and smooth SiC surface. To understand the removal mechanism at the topmost surface of SiC in the CARE process, we performed first-principles reaction path simulations using the Simulation Tool for Atom Technology (STATE) program package. These calculations are based on the density functional theory within the generalized gradient approximation of Perdew et al. The barrier height is evaluated by the climbing image nudged elastic band method. We present simulation results for the initial stages of the etching process. The reaction barrier heights for the adsorption of HF molecules on the first, second, and third Si–C bonds at the edge of the topmost Si-face are 1.8, 1.9, and 1.2 eV, respectively. These barrier heights are reasonably small for a consideration of effect of the Pt catalyst.

Abstract: The present work deals with the simulation investigation of chip formation in ultrasonically assisted grinding (UAG) of SiC ceramics with single diamond abrasive grain in order to reveal the material removal mechanism in UAG of SiC materials. In simulation, smooth particle hydrodynamic (SPH）method coupling FEM modeling is employed to overcome the large material distortions that occur in the simulation analysis of single point cutting process when only the finite element method (FEM) is used. The abrasive-grain is modeled with finite element while the target workpiece is modeled by SPH particles. The simulation results revealed that normal and tangential forces in UAG are smaller compared to those in conventional grinding (CG) without ultrasonic vibration. The scratch profiles shows that the cutting path appears to be sinusoidal when ultrasonic vibration is introduced in grinding process, which leads to a higher material removal rate than that without ultrasonic vibration.

Abstract: Powder jet deposition (PJD) method is one of the blasting methods to generate surface coatings. The optimization of PJD conditions has been reported in our previous research. However, the deposition mechanism in PJD is still under investigation. Impact phenomena between an alumina particle with the mean particle size of 2 μm and a glass substrate has been successfully simulated by smoothed particle hydrodynamics (SPH) method. From the simulation result, we have deduced that a cubic particle is fractured by an impact, and it is adhered on to the substrate. It has been also deduced that substrate is removed by a spherical particle impact. Furthermore, PJD experiments of alumina particles blasted onto a glass substrate were also conducted. The particle size distribution of rectangular particles before and after impact was measured. It was found that the particle sizes after impact averagely became smaller than those before impact. The substrate was partly removed when spherical particles impact. From the results of the simulation and the experiment, we believe that the rectangular particles are fractured due to the impacts at the moment blasting onto the substrate, and then, firmly deposited on the substrate.

Abstract: A drill processing for the difficult to cut material such as ceramics, hardened steel, glass and heat-resistant steel is widely requested in the industrial world. Furthermore the drilling process becomes more and more difficult in the case of that the requested hole diameter is less than one millimeter. In order to achieve requirements for drilling process, ultrasonically assisted machining is applicable. Ultrasonic vibration assisted machining techniques are suitable to machine difficult-to-cut materials precisely. The ultrasonic vibration assisted sub-millimeter drilling process reduces the cutting forces and prevents severe wear of tools. However, it is difficult to observe directly the effect of vibration action because the process of ultrasonic drilling is dynamic instantaneous and micro cutting process. In this report, high speed camera with appropriately arranged polarized device realized the visualization of process of ultrasonic drilling based on the photoelastic analysis. For the conventional drilling, the stress distribution diagram showed the intensive stress occurred under the chisel and side wall. On the other hand, the ultrasonic drilling produced lower and stable cutting force and decreased the tool temperature.

Abstract: The grinding performance is strongly affected by grain condition. Especially loading directly raises the grinding force, reduces tool life and deteriorates accuracy of machining. In this study, ultrasonic exciter which applies vibration energy on grinding fluid was developed. The resonant frequency of 28kHz. The exciter is set between the fluid supplying nozzle and grinding wheel. The discharging grinding fluid from the nozzle is supplied to grinding wheel between the teeth of comb-shape horn. The performance is verified on surface grinding machine with vitrified WA grinding wheel. It was experimentally demonstrated that the excited grinding fluid prevented the loading and improved the surface roughness even for grinding of aluminum. And also improvement of surface roughness was recognized on alloy tool steel.

Abstract: This publication focuses on the ultra precision manufacturing of hardened steel parts with single crystal diamond tools for optical applications such as injection moulding. Nowadays optical steel moulds are nickel plated, in order to be able to machine the surface with single crystalline diamond tools. One technology that has proven its potential for replacing this procedure is the ultrasonic assisted diamond turning technique. This process allows direct machining of hardened steel with single crystal diamond tools, which is conventionally not possible due to the high tool wear. The ultrasonic assisted diamond turning process is applied in order to machine different steel alloys that are conventionally used for mould manufacturing in injection moulding. The goal is to analyze the influence of the steel alloy and the material microstructure on the machining results. The presented analysis show the capabilities of this new technology and opens the door for it to compete with established manufacturing processes, such as the manufacturing of nickel plated mold inserts.

Abstract: This study investigated phenomena of ultrasonic cutting in case of high speed conditions. Ultrasonically assisted cutting techniques were developed by Kumabe in 1950’s. He found “critical cutting speed” that limits cutting speed to obtain ultrasonically assisted effects and is calculated by frequency and amplitude of oscillation. In general, ultrasonically assisted cutting is not suitable for high speed cutting conditions because the effects of ultrasonically applying are canceled due to tool contacts with workpiece during cutting operation. Present ultrasonically assisted cutting cannot increase cutting speed because cutting speed is limited by above reason. And ultrasonically assisted cutting cannot improve productivity due to long processing time. We conducted high speed ultrasonic cutting, maximum cutting speed of this research was 160m/min which is higher than general critical cutting speed. Workpiece material is JIS SUS304 stainless steed and cemented carbide tool inserts were employed in this research. In ordinary cutting, generate terrible built up edge on to tool rake face. In case of low amplitude ultrasonic cutting, tool rake face hasn’t built up edge and periodically marks by ultrasonic oscillation were remained on the surface. Cutting phenomena of ultrasonic cutting is different compared with ordinary cutting conditions.

Abstract: Burr in drilling plays an important role on product quality, so analysis the burr size is essential at the final production. This paper presents the application of Taguchi method for survey the burr height and burr thickness by adding ultrasonic vibration to the process. In this paper L18 orthogonal array based on Taguchi techniques was used in the design of experiments. Analysis of Variance (ANOVA) was used to determination the effect of drilling parameter on burr formation. Influence of cutting speed, feed rate and percentage of SiC particle was investigated in with and without Ultrasonic assisted drilling. Al/SiCp MMC with 5, 15 and 20 wt% of particulate SiC in dry drilling operation with TiN coated drill tools were investigated.