Key Engineering Materials Vol. 693

Abstract: Vibration of cutting process is an important factor to influence the surface roughness. By Orthogonal design, take hard cutting surface roughness test for bearing steel GCr15 with 62~64HRC, analyzing the law of the variation of cutting parameters effect the amount of vibration and the surface roughness value. And it establishes the formula about vibration and surface roughness. The amount of vibration and the surface roughness increases first and then decreases while the cutting speed increases in a specific area, meanwhile its vibration will reduce and its surface roughness will enlarge while the feed increases. The cutting depth has a little influence to surface roughness and vibration, and the cutting depth is first decreased and then increased accompanied by the tool nose radius increases with the increase of vibration and the surface roughness. The research can provide reference for improving the surface quality.

Abstract: In the cryogenic treatments process, the temperature distribution in a work-piece of high speed steel (HSS) is crucial to the effectiveness of the treatment. However, determination of temperature field during the cryogenic process is difficult. In this study, the temperature distribution in W9Mo3Cr4V HSS bars with a diameter of 24mm during cryogenic treatment was investigated using thermocouples so that obtained the optimization of process parameters and improve the high speed steel tool life. Temperatures at different nodes and their variations with time were measured and numerically studied using Pro/E, Workbench and Fluent software. Results from both the simulation study and experimental measurement are in good agreement, indicating that the temperature distribution inside a work-piece during cryogenic treatment can be determined using a combination of simple tests and numerical simulation, and finally provided a theoretical guidance for making the reasonable cryogenic treatment procedure.

Abstract: In this paper, the real surface topography was measured at first to provide the theoretical bases for developing a novel quick numerical simulation method. The result showed that the protrude height of abrasive belt surface appeared to be non-Gaussian distributed. And its auto-correlation function was found to be in exponential form and anisotropic. By using given skewness, kurtosis and auto-correlation function, the novel simulation method is provided, which is based on Johnson translator system and 2D-linear filter technique. This method overcomes the shortcomings of the experimental method to achieve the required topography of abrasive belt with certain statistic characteristics by using given skewness and kurtosis and auto-correlation function. The comparison between simulated surface and measured topography revealed that they share the same probabilistic characteristics.

Abstract: In this paper, the effect of the cutting heat on the workpiece in the processing was studied. Its essence is to study relationship between the workpiece temperature variation and internal residual stress distribution. In the specific problem-solving process, the metal cutting theory, finite element related knowledge and metal elastoplastic deformation theory were combined, and established a mathematical model which was suitable for the model of the milling temperature and residual stress in the milling process. It would provide theoretical support for future study on milling deformation mechanism.

Abstract: Micro milling is most flexible to create 3D features for application. However, how to design and fabrication of high precision micro milling tools are one of big challenges for mechanical micro milling. Commercially available micro milling tools are usually simply made from downsizing of macro milling tools, which have negative impact on milling performance. Therefore, in this paper, firstly, various structural of micro milling tools were optimized with abaqus that investigated stress and strain under certain static load on the cutting edges. Then, results showed the minimum stress and strain was a micro hexagonal end mill. Finally, a Ti (C₇N₃) cermet micro hexagonal end mill with a radius of 0.5mm was fabricated by wire electrical discharge machining, and the evaluation experiments for the hexagonal mill have been processed on a micro milling centre.

Abstract: Si₃N₄ is difficult to be machined due to its hard and brittle nature. In order to improve its machining quality, a new method of ultrasonic-assisted laser machining is proposed. The machining device is established including Nd: YAG pulsed laser, ultrasonic vibration stage and water flow system. Etching experiments of laser machining with and without sample vibration in anhydrous conditions and in water conditions are studied respectively. A VM-3030E two-dimensional image measuring instrument is applied to detect shape and measure dimension of the sample. Microstructure morphology of the sample is observed by a JSM-7500F scanning electron microscope. Experimental results show that there are fewer slags on inner surfaces of V-shaped grooves when laser machining with water flow. The surface quality and depth-to-width ratio of grooves machined by laser with vibration on sample are improved significantly in comparison with those without vibration. The depth-to-width ratio of groove machined by laser with 90.1W vibration power is near twice than that without vibration.

Abstract: 17-4PH stainless steel is a widely used martensitic precipitation hardening stainless steel, and it is a typical difficult-to-cut material. Residual stress is an important part of the surface integrity. In this paper, superficial residual stress tests of face-milling the 17-4PH stainless steel were carried out at 0.1~0.3 mm/tooth with TiAlN coated carbide inserts. The effects of feed rate on the superficial residual stresses at various cutting speeds were studied. It was found that the residual stresses on the machined surface were very sensitive to the feed rate. The superficial residual stresses at the directions of parallel to and normal to the feed direction both remained compressive and changed obviously in higher compressive direction along with the feed rate. The burnishing effect determined by the cutting force was found to be the primary reason of the residual compressive stresses on the machined surface. The suitable cutting parameters were recommended according to the superficial residual stresses.

Abstract: Titanium alloy is finding increased application in aeronautical, automobile and structural applications. During post processing of titanium alloy, milling is one of the mostly used machining processes. In this study, the relationship between temperature and milling parameters was developed by response surface methodology (RSM), and a temperature model for milling titanium alloy is proposed. The model is found to be adequate through ANOVA. The result indicates that the increase in cutting speed and feed rate increases the temperature. The radial depth of cut and depth of cut do not show a general trend on temperature in milling of titanium alloy.

Abstract: Targeted at numerical control machining process of mass customization vehicle wheel rim revolving body parts and its fixture planning problem, using the dot product method between the unit normal vector of the feature facet, it was provide to distinguish the main direction of machining surface, machining position of workpiece was determined, and NC machining process of integrated procedure was designed. The loaded and taken out of the wheel rim workpiece were analyzed according to the two-dimensional plane clamping method, the clamping point position of wheel rim workpiece can be determined. Using the principle of planar mechanism kinematic to analyze one’s claw of turn-mill fixture kinematics trace, so that a quick clamping structure can reduce the cylinder stroke was designed. This fixture device was convenient and reliable.

Abstract: In this study High-speed steel taps are taken as the research object. Electrolysis technology was used to deal with the taps in various count time (7s 14s 21s 28s 35s) and then obtain the corresponding radii of the cutting edge (11.38μm 15.05μm 20.35μm 23.00μm 25.55μm). The experimental results exhibit quantitatively the effect of tool radius on the performance of tapping. A radius on the cutting edge prevents fast and unpredictable wear. Moreover, the existence of an optimum value of the radius has been revealed experimentally. Tapping test is used to prove the optimal cutting edge radius is 15.05μm and the taps life increase about 2.5 times than usual taps. It can provide an important theoretical basis for the modifications of the cutting edge radius and give a method to improve tap life.