Key Engineering Materials Vols. 375-376

Abstract: Experiment of hard cutting GCr15 with PCBN cutting tools, the influence of tool’s inclination angle and cutting parameters (cutting speed and feed speed) on cutting forces and cutting temperature are studied. A three-dimensional finite elements model using the commercial software Deform 3D 5.03 is developed. The friction between the tool and the chip is assumed to follow a modified Coulomb friction law and the adaptive remeshing technique is using for the formation of chip. The workpiece material property is a function of temperature, strain, and strain rate in the primary and secondary shear zones. Finite element method is used to simulate three-dimensional precision cutting, including orthogonal cutting and oblique cutting. The cutting forces and back forces are slightly changed by tool’s inclination angle. However, in high cutting speed, the cutting force decrease as the tool’s inclination angle increase, while the cutting temperature increase as the tool’s inclination angle increase. The simulation results are compared with experimentally measured data and found to be in good agreement to some extent.

Abstract: Air cooling is a near dry machining method, which cools cutting area and evacuates chips using low temperature cold wind instead of cutting liquid. It can decrease tool wear, increase tool life, reduce machining cost and bring no chemical pollution. In this paper, air cooling test was carried on, in which vortex tube was used for cooling and high hardness bear steel GCr15 was machined by PCBN tool. Experiment results indicated that cold air from vortex tube has a significant effect on cutting force, cutting temperature and chip formation process. This paper’s conclusions will have a great reference value for the practical application of air cooling technology.

Abstract: Revolving curved surface of mould should have low roughness as well as high accuracy of geometry profile. And it is an essential method to meet the accuracy request with grinding process. In order to solve the problem of grinding such revolving curved surface, an Arc Envelope Grinding Method (AEGM) is presented in this paper, which uses a wheel with arc section. By analyzing the movement of the grinding point, the relationship between the length of trajectory that the grinding point moves along and radius of the arc, curvature of workpiece is explained. Meanwhile, the relationship between the radius of arc, the curvature and the grinding area is studied.

Abstract: This paper deals with chip breaking behaviour of 3-D complex groove inserts in machining carbon constructional steel-45 steel at high cutting speeds .Cutting experiments were performed at eleven different cutting speeds. Firstly, the results showed that by increasing cutting speeds, the changes of the critical feedrate and chip breaking scopes at high cutting speeds machining with 3-D complex groove inserts were nonlinear and not monotonous function relations. Then, mathematic models were built. Secondly, the results showed that the critical depth of cut was a constant value at various cutting speeds. And, the curves of the critical depth of cut were perpendicular lines. For this purpose, the critical depth of cut mathematic model has been built. The study above lays a theory and basis for future investigation of the mechanism of chip breaking with 3-D groove insert in high speed machining.

Abstract: Optical glass is one of the most difficult-to-cut brittle materials due to its high brittleness and high hardness. In this work, an experimental study was conducted to diamond-cut glass SF6 in ductile mode. Nano-indentation analysis was performed for understanding the material deformation behavior in practical cutting process. The effect of process conditions, i.e. conventional turning and ultrasonic vibration assisted cutting, on the tool wear and surface quality was discussed based on the observations of the tool wear zone microstructure and the machined surface topography. The investigation presents the feasibility of achieving optical quality surfaces on glass with the application of ultrasonic vibration cutting technology. The tool life and surface finish were improved significantly by applying ultrasonic vibration to the cutting tool.

Abstract: Diamond spherical shell thick film was prepared by high power DC-plasma jet CVD. Atom force microscopy, scanning electron microscopy, Raman spectroscopy and roughness-profile-meter were used to characterize microstructure, morphology, impurities and orientation evolution of diamond spherical shell thick film. The results show that, when nucleation begins, grains grow random orientation. The grain size of spherical diamond film prepared is compact, clear, uniform, continuous and no remarkable bigger grain over the whole surface of film. On the growth surface, (100) facets were dominant, and the cross-section SEM indicated that film columnar spreading grew from the substrate surface to the diamond film surface. The roughness of the growth surface was much more than that of the nucleation surface. To adjust some important parameters as methane concentrate, depositing time, and matrix temperature, and high quality diamond spherical shell thick film was deposited.

Abstract: Based on the theoretical principle of tapping formation and simulation with modified-tooth tap, the relationship among the different geometric parameters of the tap was further analyzed. A series of modified-tooth taps and standard ones with a cutting cone angle of 7°30´and a outer diameter of M6, which were made from high-speed steel W9, were taken to do the comparative tapping test on nickel-based high-temperature alloy GH4169, titanium alloy TC4 and 45 steel. The test results indicated that the leading cause of difficult tapping in GH4169 and TC4 was the largeness of their friction torques which were about 35 % and 62 % of tapping torque respectively, where the frictional wear was a fundamental reason for tough tapping GH4169 and the spring back of machined surface for TC4.The obvious decreases of friction torque with the modified-tooth tap approximately 70% and 50% respectively for GH4169 and TC4 were attributed to its unique tapping formation principle of generating broaching but no remarkable effects on 45 steel in comparison with standard tap.

Abstract: Using plated CBN hard honing wheels with standard involute tooth profiles, there will be the middle concave error around pitch circle on the machined gear tooth surfaces. Therefore, standard involute tooth profiles of honing wheels have to be modified properly before electroplating CBN. In the paper, aiming at the tooth profile modification of honing wheels, the standard involute curve was converted into a spline curve, and control points of the spline curve were parameterized in solid modeling of honing wheels. By the Pro/E and ANSYS Workbench software, the engaging situation between honing wheel and gear was analyzed. Based on the analysis results, assuming the control points around pitch circle were set as variable parameter, and basically equal contact pressures were set as response variable parameter, the tooth surfaces of hard honing wheels were properly corrected, it was proved useful to reduce or eliminate middle concave error in practice.

Abstract: This paper introduced the machinability and the state-of-art of Ti6Al4V machining. Turning test with thee different tungsten carbide tool have be done at cutting speed 40, 80, 120, 160 m/min, the relationship between cutting force and cutting speed, cutting distance was analyzed, the influence of working cutting edge angle on the tool wear and cutting force was investigated as well. Finally, the tool wear and wear mechanics was analyzed.

Abstract: Twist drill is widely used in hole-making process in industries, due their low production cost and ease of regrinding after wear. However, drilling of fiber reinforced plastics with twist drill often results in defects and damages, such as delamination, debonding, spalling and fiber pullout. The chisel edge of twist drill is the mainly influence for the thrust force and the hole quality in drilling carbon fiber reinforced plastic (CFRP) laminates. Pre-drilled pilot hole or reduce chisel edge can eliminate the threat for twist drill in drilling induced-delamination. Drilling-induced thrust force was selected as quality character factors to optimize the drilling parameters (drill type, feed rate and spindle speed) to get the smaller the better machining characteristics by Taguchi method. The results show that the feed rate and drill type are the most significant factor affecting the induced-thrust in drilling CFRP laminates.