Advanced Materials Research Vols. 53-54

Abstract: A new finishing technology of the swirling air flow compounded with magnetic-field is advanced. Force acting on abrasive is analyzed by the action of airstream and magnetic-field coupling according to gas-solid particles two-phase flow. Finishing mechanism on the swirling air flow compounded with magnetic-field is illustrated, namely, burrs and microcosmic peak on the surface of workpiece are broken, grinded and cut via a great deal of abrasive particle impacting, microchipping and rolling machined surface. Unthreaded hole is experimented on the condition of changing magnetic induction intensity B and machining time t. Changing curve of surface roughness Ra along with time t is shown. Research indicates that machining time of the swirling air flow compounded with magnetic-field is short and machining efficiency is high. The longer machining time is, the smaller surface roughness Ra is and the better machining effect is.

Abstract: This paper proposed a viewpoint to explain why vibration assistance may increase material removal rate (MRR) in vibration-assisted magnetic abrasive finishing process. A series of experiments on vibration-assisted finishing have been carried out. On the basis of these experiments, the finishing characteristics are represented summarily. It was shown that the increase in material rate is mainly due to an increase in material removal per unit working distance.

Abstract: To internal magnetic abrasive particles surface finishing, the motion of magnetic abrasive particles was influenced not only by the intensity of magnetic induction, but also by the internal diameter, and the magnetic inductive capacity was also an important factor that influences finishing quality. In this paper, under the same experimental conditions, electromagnetic field and permanent magnetic field were respectively used to magnetic abrasive particles surface finishing on thin stainless steel bush and 45 steel bush, new thoughts on inserted permanent magnetic pole and butted permanent magnetic pole were pointed out. The finishing quality of two kinds of work pieces under three different magnetic poles was compared. The results have shown that permanent magnetic pole could decrease the surface roughness Ra of work piece from 1.6μm to 0.2μm, which could solve the puzzles encountered in internal magnetic abrasive particles surface finishing on magnetic inductive work piece and had good promising application value.

Abstract: A coupled thermo-mechanical model of plane-strain orthogonal metal cutting including burr formation is presented using the commercial finite element code. A simulation procedure based on Normalized Cockroft-Latham damage criterion is proposed for the purpose of better understanding the burr formation mechanism and obtaining a quantitative analysis of burrs at exit. The cutting process is simulated from the transient initial chip formation state to the steady-state of cutting, and then to tool exit transient chip flow, by incrementally advancing the cutting tool. The effects of cutting condition on the non-steady-state chip flow while tool exit can be investigated using the developed finite element model.

Abstract: The two-side burr is one of the important factors that influence the edge quality and performance of precision parts. The two side-direction burr formation process is simulated with DeformTH3D. The mechanism of two-side burr formation is analyzed in terms of the results of the simulation. Enlarging the tool orthogonal rake and minimizing the depth of cut can reduce the burr size.

Abstract: Due to the properties such as high strength and high toughness, burr was commonly produced in the machining of stainless steel 1Cr18Ni9Ti, especially when a chamfered cutting tool was used. This study investigated the effects of chamfering geometry of cutting edge and machining parameters on burr formation and presented active control methods to minimize burr size on the exit end based on the experimental research in milling of 1Cr18Ni9Ti. Experiments of face milling with various cutting edge geometric features were conducted. Maximum height and thickness of exit burr and exit side burr were measured. As a result, a proper chamfering geometry that combined the advantages of enhancing the cutting edge strength and obtaining favorable burr types was presented. The experimental results also showed that a relatively high cutting speed was helpful in reducing burr formation; proper medium feed rate and axial depth were favorable for the minimization of burr size. This research is beneficial for precise machining of stainless steel.

Abstract: In most machining operations undersirable burr or negative burr is created at workpiece edges. The burr/negative burr formation mechanism is analyzed based on shear strain which is obtained from simulation results of the finite element model of burr/negative burr forming process. To varify the simulation results, experiments are conducted. We observered that there exists a critical value of shear strain for burr/negative burr transformation. Burr or negative burr, which to be formed at workpiece edges can be controlled by adjusting the cutting conditions or tool geometric parameters. Edge quality of workpiece can be controlled by converting burr or negative burr forming.

Abstract: Numerical simulation of the blanking process of a sheet metal, i.e. the formation of roll-over and a burnished surface, and crack initiation and propagation, is done using an elastic plastic finite element model. The Normalized Cockcroft and Latham’s expression is used as a ductile fracture criterion. Numerical study was conducted to investigate how the tool-wear affects the burr height by varying the punch nose radius. The simulation results obtained under the effect of the same process variables are in good agreement with the experimental results. Six punches with various nose edges, 0.00mm, 0.05mm, 0.10mm, 0.20mm, 0.30mm and 0.40mm were used for blanking simulations. The results indicate that the burr height is directly proportional to the punch nose radius.

Abstract: The metal cutting burr is one of the factors that influence the edge quality and performance of precision parts.A finite element model has been established to investigate the mechanism of burr formation and limit transformation in high-speed machining 2024Aluminum alloy .The burr/fracture formation process is simulated with elastic-plastic nonlinear element method based on ABAQUS.This paper has investigated the mechanism of burr /fracture formation and the limit transformation condition of cutting-direction burrs and fractures in high-speed machining and the limit transformation condition change with the cutting condition,which lay scientific basis of further research on cutting burrs formation and its minimization and deburring technology.

Abstract: Although various diamond polishing techniques have been studied for many years, no individual method can polish free-standing CVD diamond film with high efficiency and high polishing quality. This paper investigates polishing CVD diamond film by the combination of electro-discharge machining (EDM) and chemical mechanical polishing (CMP). Scanning electro microscopy, Optical microscopy, Energy dispersive X-ray analysis, Talysurf surface profiler and Raman spectroscopy were used to evaluate the surface integrity and quality of diamond film before and after polishing. Based on the experimental results, the material removal during EDM process can be a chemo-mechanical process, including gasification, melting, sputtering, oxidation and graphitization. While in CMP process, diamond was removed under the mechanical and tribochemical interaction. The combination of EDM and CMP has advantages of high efficiency, high polishing quality and low damage. It is suitable to polish large area free-standing CVD diamond film.