Key Engineering Materials Vol. 667

Abstract: The short electric arc machining technique is a new type of strong current processing method, which has many advantages, especially for difficult-to-machine materials, such as no cutting force, small cutting chips, easy to chip removal, high processing efficiency and so on. In this paper, the electric arc processing cutting performance of two typical difficult-to-machine materials, titanium alloy and high-temperature alloy, was studied by electric machining cutting experiment to analyze the influence of arc processing on the properties of materials. Using the designed electric arc machining system, the effect of electrical processing parameters on processing properties was discussed. Furthermore, the surface layer hardness and materials metallurgical structure were detected to study the change of material internal organization and the effects on material properties change, which provide the corresponding theoretical analysis basis for arc machining of difficult-to-machine materials. Experimental results show that the titanium alloy and high-temperature alloy have small heat affected zone and hardening layer after electric arc processing, which could meet the requirement of subsequent machining to obtain a good surface quality.

Abstract: In order to study the influence of grinding surface quality affected by grinding speed for CBN grinding wheel, the method of simulation and experimentation used to study grinding surface quality of CBN grinding wheel. First, on the basis of grinding wheel topography, the influence of grinding surface quality affected by grinding speed was analyzed by adopting motion simulation method. Then, high-speed grinding experiment was carried out to three kinds of metal materials, and machined surface roughness and surface hardness after processing are measured and researched. Test shows that “speed effect” is remarkable in grinding metal materials. As the grinding speed increases, the grinding surface quality of workpiece is gradually improved. With the speed increasing, surface roughness of workpiecedecreases, and at lower speeds the surface roughness dropped more obvious. With grinding speed increases further, the change of roughness tends to be slow, and the bending point appears at about 100m/s.Surface hardening degree decreases with grinding speed increasing, when grinding speed up to high-speed grinding stage, the degree of hardening of the workpiece is more soothing.

Abstract: The aluminum alloys are widely used to manufacture large mirror of infrared band optical systems because they have many advantages such as low cost, low mass density, well thermal conductivity, well plasticity and easy manufacturing. In order to imporve the machining efficiency and meet the requirements of suface error and suface roughness of large metal mirror, diamond ultra-precision cutting is used as finish machining to manufacture them. But the diamond tool wear is severe which is induce by the cutting heat and the cutting force during the cutting process. In this work, the metal cutting finit element sofeware-AdvantEdge has been used to study the cutting tempreture in diamond ultra-precision cutting of aluminum alloy, the influence rules of cutting parameters and tool geometric parameters are researched. And the diamond ultra-precesion cutting experiments were performed, the cutting temperature were detected by infrared thermal imager. The results show that the cutting speed exerts the most considerable influence on the cutting temperature, and the cutting temperature increases with an increase in the cutting speed. Although the temperature detected by the infrared thermal imager in the diamond ultra-precesion cutting experiments is lower than that obtained from the simulation of finit element method (FEM), the varied trend of the cutting temperature is the same. So the FEM simulation proves to be true.

Abstract: Single crystal silicon has both important application value in the fields of micro-optics and MEMS, and it has been considered as one of the most difficult-to-cut materials because of its hardness and brittleness. Removal mechanism of the silicon was discussed, and the model of undeformed chip thickness was established in this article. According to the data of micro-groove surface roughness from the diamond fly-cutting experiment, the nonlinear relationship curve, between the largest undeformed chip thickness h_max and microgroove surface roughness R_a, were obtained using Gaussian-fitting principle, and the regression equation of the fitting curve was also got. Thus the prediction mathematical model of microgroove surface roughness was derived. The influence laws of the main working parameters on the R_a were obtained based on the result of this experiment and the response surface of the prediction model, and some conclusions were summarized: the surface roughness R_a of microgroove in the single crystal silicon decreases with the decrease of the cutting depth a_p, the feed f and the increase of the spindle speed n under the diamond fly-cutting; the experimental results also showed that feed f affects the value of R_a very much, cutting depth a_p less, and spindle speed n the least.

Abstract: Abstract. How to improve the precision of the stamping forming has been one of the stamping researchers concern in the stamping technology.This paper analysis the material stamping performance of AL5052 aluminum alloy sheet,study the influencing factors of forming precision,and find the the mapping relationship between influence factors and stamping forming to effectively predict the forming error .The first part is to analyze the factors that affect the forming process, then get the main factors that influence the part of stamping forming. And then establish the main influence factors^’ mathematical model of stamping forming error based on BP neural network, and through the training of BP neural network to prove the model^’s practicability.

Abstract: This paper mainly analyzes the cutting mechanism of low temperature air cutting, and makes research and analysis about the brittle characteristics, the lubricate mechanism and the chip breaking mechanisms of metal materials under low temperature cold condition. Meanwhile, the cutting performance of typical difficult-to-machine materials, such as The precipitation stainless steel, super-alloy and titanium alloy, were discussed. Through cutting experiment under normal conditions and low temperature air conditions, the influence on cutting force, tool wear, chip shape and surface processing quality of typical difficult-to-machine materials were analyzed. The experimental results show that the low temperature air has better effects on cutting difficult-to-machine materials. It can reduce temperature distribution and cutting force, improve tool life and suface processing quality, decrease the use of cutting fluid and mitigate environmental pollution. Thus, low temperature air cutting is an efficient and environment friendly way to solve the problem of cutting difficult-to-machine materials.

Abstract: Due to its relatively low mass density, low cost, high strength, the aluminum alloy is an ideal optical material to fabricate the large metal mirror of infrared band optical systems. The diamond ultra-precision cutting can produce ultra smooth machined surfaces without other finishing processes. Consequently, it can be used as a effective method to fabricate the large metal mirror. However, the tool wear is severe during the ultra-precision processes, which will ruduces the surface error of the large metal mirror. In this work, the ultra-precision cutting tests were performed to investigate the tool wear. The tool wear was examined by using a scanning electron microscope (SEM), and the chip was examined by using x-ray energy dispersive spectrdmeter (EDS). The tool wear mechanism and the influence of the chutting parameters on the tool wear were investigated. The results show that the daimond tool occurred abrasive wear and diffusing wear in the diamond ultra-precision cutting of aluminum alloy. The average clearance wear width increases with an increase of the cutting speed and the feed rate. There is a slight rise in the average clearance wear width as the depth of the cut increases in the range of 5μm-15μm. The average clearance wear width obviously increases when the depth of the cut reaches to 20μm.

Abstract: Connection process of welding has many characteristics, such as high efficiency, simple and low cost. The change of welding sequence makes the stress and welding deformation changed, so welding sequence has larger influences for welding deformation. The proper welding sequence is important to reduce the deformation of the workpiece, improve the process quality of the product, reduce the electrode wear, increase the service life of welding machine. This paper according to the zhengzhou Nissan C16 models under the left engine cabin wall welding assembly, by comparison, different welding sequence draws the conclusion: in the welding process of sheet metal, irregular alloy steel workpiece thin will appear in size and shape in the stamping process, especially the two or more than two pieces of sheet metal combined welding to be used welding sequence suitable to reduce the deformation and error in the process of welding. For the sheet metal parts of irregular shape, with the gap bending degree and joint surface big welding area is the first welding object, to fit a small gap region is the second welding object, then from the big regional joint gap to fit clearance small area welded, solder joints of welding can be uniformly distributed, according to the results of the analysis to formulate reasonable welding sequence, can provide a theoretical basis for the formulation of welding technology in actual production. Therefore, welding sequence is particularly important.

Abstract: Due to the unfixed state of the workpiece and the dissimilarity between sections in through-feed centerless grinding, the positions and orientations of the workpiece keep changing in the grinding process, which are coupled with the workpiece roundness generation. In this paper the positions and orientations of the workpiece are described by the dynamic equations obtained from Lagrange equation. And the homogeneous coordinate transformation is applied to present the profiles of the workpiece, grinding wheel and control wheel in the reference frame. Finally the time varying profile of the workpiece is obtained for the investigation of the material removal process in 3D space. The material properties of the workpiece, the wheels and the workrest combined with the geometric relationship of their profiles are utilized to calculate the interaction between them, including the three forces along the axes and the three moments about the axes.

Abstract: Fused deposition modeling (FDM) is one of the most widely used technologies in rapid prototyping. On the principle of layered manufacturing, the melted polymer filament is extruded and formed. In order to achieve transition from nonfunctional prototypes to functional prototypes of FDMed models, using the RepRap Kossel delta 3D printer and 1.75mm diameter polylactic acid (PLA) filament, it was analyzed that the effects of the nozzle moving rate and slice thickness on adhesive strength based on the existing technology research by orthogonal test. The experiment results indicated that adhesive strength of filament increased both with the nozzle moving rate and with its slice thickness. The latter induced increase more significantly. Finally, comprehensive experiments had been performed to quantitatively study the adhesive strength variation with the filling rate, which provides data reference for setting proper filling rate. Reasonable filling rate setting can not only satisfy the strength requirement without debasement of printing quality, but also reduce filament consumption, improve the manufacturing efficiency and provide important instruction significance for actual printing.