Key Engineering Materials Vols. 373-374

Abstract: Ultrasonic vibration cutting experiments have been carried out for the machining of the plasma-sprayed Al2O3 coatings. The optimized value of V/Vc for the vibration cutting was obtained by a series of tests. The comparing experiments of the ultrasonic vibration cutting and the traditional cutting for the machining of the plasma-sprayed Al2O3 coatings by the cube nitride boride (CBN) and YC09 (hard alloy) lathe tools have been executed. The results indicate that the valid cutting time for the vibration cutting is 3-4 times longer than that for the traditional cutting, at the same time, the surface roughness values of the coatings machined by the vibration cutting are less than that machined by the traditional cutting. CBN and YC09 have been optimized as the candidates to machine the Al2O3 coatings through a series of vibration cutting tests carried out on the lathe tools of CBN and three hard alloys of YC09, YH3 and YGHT. The cutting parameters, such as V, aP and f, for the vibration cutting of the Al2O3 coatings by CBN and YC09 were obtained through the orthogonal tests and regression analysis. The obtained parameters have been utilized to machine the plasma-sprayed Al2O3 coatings for validation, and the results indicate that the ultrasonic vibration cutting is a competitive method to machine the plasma-sprayed Al2O3 coatings.

Abstract: By using SnSO4 water solution to activate global granular Zn powders of 325 screen mesh, Zn-Sn composite coverage is formed under the action of mechanical impact of the tiny glass beads and work pieces. During and after the formation of coating, acid water liquor will react with metal basal body, and hydrogen gas is bound to emit from the pathway and form micro pores. In addition, there are bond areas between the new and the primary coverage, which may lead to the emergence of micro crack on the coating owing to such causes as too big or uneven impact during plating process, little distortion of global granular zinc dust inside the plating coat, less tight coalescent of the zinc dust flecks. These problems can be confirmed by SEM scanning coating surface and cross section pictures of plating coat. In our study, methyl hydrogen silicone fluid, titanium isopropoxide and benzinum are used as the basal components. This compound has such features as better osmosis for micro pores and cracks formed in the process of dual coverage, strong adhesive force, anti-contraction, high transparence and water proof property. The impact of titanium isopropoxide dosage on the solidifying speed of methyl hydrogen silicone fluid, and that of mechanical plating zinc coating on corrosion proof are studied. Through tests, the proper compound ratio is determined as 11:10:79 of methyl hydrogen silicone fluid to titanium isopropoxide to benzinum(90-120 Centigrade degree). Experiments indicate that when the coating thickness is 0.2 micron, the emergence time of white corrosion on the plating coat doubles, accordingly, that of red rust prolongs, this shows that the anticorrosion of the coverage can be significantly improved through superficial pore sealing in zinc plating coat.

Abstract: Water cavitation peening (WCP) with aeration is a novel surface enhancement method. A new ventilation nozzle with aeration is adopted to improve the process capability of WCP by increasing the impact pressure induced by the bubble collapse on the surface of components. In this study, in order to investigate the process capability of the WCP with aeration, a standard N-type almen strips of spring steel SAE 1070 was treated by WCP with various process conditions, and the arc height value and the residual stress in the superficial layers were measured by X-ray diffraction method. The optimal fluxes of aeration and the optimal standoff distances were achieved.

Abstract: Grind-hardening machining is not only a complex process coupling mechanical, dynamical and thermal effects, but a process containing distinct changes of microstructure and properties of the workpiece grinded surface layer. Under the defined experimental conditions, an empirical formula was constituted to describe the relation between hardened layer depth and grinding parameter of grind-hardening layer, and the multi-parametric optimization was conducted. A commercial FEM software package was used to simulate the grind-hardening process. The distribution and variation characteristics of the temperature and microstructure in the grinded surface layer of workpiece were obtained and the forming mechanism of the grind-hardened layer is revealed.

Abstract: To investigate the effect of micro-topography on the wear properties of the cold roller, rough surface was characterized with fractal geometry, and the profile of laser-textured surface was measured based on the analysis of surface profile self-similarity, feasibility of fractal characterization of the surface was studied with power law method. Results show that Isotropic surfaces tend to be fractal and surfaces processed under definite technological conditions can be characterized with fractal geometry. On this basis, effects of surface fractal parameters on the wear rate of the roller were analyzed with fractal geometry model for wear prediction. Condition of achieving optimal fractal dimension was presented and the expression of the optimal fractal dimension was derived for the minimum normalized wear rate. It shows that normalized wear rate is mainly determined by fractal dimension besides the material properties and an optimal fractal dimension existed for the engineering surface is affected by the plastic index, normalized true contact area and scale coefficient. The results will provide bases for the studies of friction and lubrication of the textured steel sheet and guidance for the actual processing.

Abstract: A Reynolds equation is presented for the hydrodynamic pressure components between the two faces of a partially or fully laser surface textured mechanical seal (LST-MS) by considering the hydrostatic and hydrodynamic characteristics and cavitation within the sealing fluid film. Galerkin’s method is used to set up the finite element model for the Reynolds equation. The effects of geometric parameters of the spherical dimple on seal performance of a LST-MS are studied. The texturing parameters are numerically optimized to obtain the maximum opening force and/or the maximum ratio of fluid film stiffness to leakage rate. It is shown that a full LST-MS has stronger hydrodynamic effect and lower frictional torque between the two faces than that of a partial LST-MS, but the latter works at a less leakage and a more stable working state. Thus a partial LST-MS is recommended for practical application for its better comprehensive seal performance.

Abstract: In the rapid spray metal tooling, metal film is spray-formed on the substrate and supported under the back, which will act as the working surface of the rapid metal tool finally. So the finishing process for the sprayed metal film is important to the quality and the lifecycle of the rapid metal tool. The finishing of the metal mould is frequently carried out manually, these kinds of operations are iterative, time consuming and require experience. Automation can introduce cost reduction minimizing production times on such manual finishing operations. This paper presents a robotic polishing system with free abrasive for the finishing of the rapid spray metal tool, which is consisted of a six-degree-of-freedom industrial robot manipulator, a high speed electrical polishing spindle and a numerical swivel table. Soft polishing pad and free abrasive are also selected for the robotic polishing system. The path planning is so important to the robotic polishing system that a partition & flexible path mapping method basing on UG CAM is developed to generate the uniform robotic polishing path on the complex mould surface. UG/Open GRIP programming module is used to generate the driving paths with different path intervals on the predesigned plane for each partitioned part. When the driving paths are projected to the mould curved surface, the uniform polishing paths with NC code can be generated by the multi-axis CAM module of the UG. And the path with NC code can then be transformed to the robotic polishing path. According to the elastic deformation and the abrasion of the soft polishing tool, the robotic polishing path should be adjusted to keep the smooth polishing process by offsetting the pre-compressed value and the abrasive compensation value along the polishing axis direction. Technical parameters of the robotic polishing process are also optimized through the experiments. Finally, the rapid metal punch mould is finished to test the robotic polishing system.

Abstract: At present, adhesive coating is by far the most widely used technique in the space panel manufacturing. The automatic process level is essential for improving the quality and efficiency of the space solar cell array assembly. In this study, the surface coating model for adhesive dispensing on the space solar cells is obtained, which describes the relationship between the thickness of the adhesive layer on the solar cell, the moving speed of the syringe and the differential pressure. Then the structure of the surface coating robot is presented for the space solar cell arrays assembly. The experimental results have showed that the surface coating robot can greatly improve the efficiency and quality of the space solar cells array assembly. The adhesive no longer outflows and stains the solar cells and the panel. This robot is useful to protect the environment and keep workers away from the poisonous chemicals. Instead of the manual work in space solar cell arrays assembly, the application of the surface coating robot will enhance the development of space industry.

Abstract: With the change of the relation between the Bond numbers and 1/3, the different control equations with different dispersion item for the surface wave was obtained. The equation under tension and bottom was reduced from the potential flow theory with the little parameter perturbation technique, and then was solved by using the pseudo-spectral method. The waterfall of the surface wave was simulated with software. The results show, that different surface tension has significant effect on the film surface and there are some solitary-like wave.

Abstract: A new finish method uses an effective electrode connecting with a nonconductive grinding tool to execute the design of compound processes of electrochemical finishing and grinding following turning is investigated. The submitted processes can be used for various turning operations. Through simple equipment attachment, electrochemical finishing and grinding can follow to execute the finishing process on the same machine. Among the factors affecting electrochemical finishing the performance of grinding combined with electrochemical finishing is primarily discussed. In the experiment, the electrode is used with continuous and pulsed direct current. The grinding tool moves following the electrode and grinds the workpiece surface. The experimental parameters are electrical current rating, feed rate of electrode and grinding tool, rotational speed of workpiecel, pulsed period, and geometry of finish-tool. The results show that pulsed direct current with longer off-time can slightly improve the finish effect for its dregs discharge mobility. Using an adequate rotational speed of workpiece with high rotational speed is advantageous to the finish effect. A thinner plate-form electrode with a smaller end radius is associated with larger discharge space and produces higher current density and provides faster feed rate and a better finish effect. The grinding can effectively increase the finish effect. An effective and a low-cost finish process through the design electrode and using the grinding assistance in the electrochemical finishing after turning process make the surface of workpiece smooth and bright.