查看更多>>摘要：The topography errors of micro electrical discharge machining (micro-EDM) surface are mainly composed of surface roughness, surface waveness and profile error. These three errors influence the workpieces functions and performances in varying degrees. Thus, how to pick up these compositions without distortion is very important for surface comprehensive topography evaluation. In this paper, the roughness of micro-EDM surface contour lines is separated by wavelet method. Firstly, it is certified that any curve line could be indicated by different frequency parts with multi-resolution analysis, which is the feasibility study for roughness separation with wavelet method. Then, the mathematical model of roughness separation of contour lines is set up. Finally, the formula of roughness separation times with wavelet theory is given.
查看更多>>摘要：Generating high-melting-point metals droplet is a bottleneck in the area of droplet-based rapid prototyping. In our research, a pneumatic drop-on-demand (DOD) generator was developed which can spray A2024 alloy successfully, and the maximum ejection temperature can reach to 1200℃. Experiments were conducted to examine the influence of the oxygen content on the metal droplet spray. The uniform A2024 droplet was ejected stably under the condition where the oxygen content was less than 25ppm. As the solenoid valve was opened once with different time span, four cases were observed: droplet stream, three droplets, two droplets and one single droplet. A2024 droplets were deposited continuously on top of each other in vertical direction to form vertical columns, which meant the graphite nozzle can be used in experiment. A simple square tube was produced by regulating the droplet generator, which showed the rapid prototyping by high-melting-point droplet deposition is feasible.
查看更多>>摘要：The gas jets from the conical and new designed supersonic nozzles on different working pressure are simulated by a computational fluid dynamics code, FLUENT, using standard k-ε model and unstructured grid finite volume method with compressible axis-symmetry N-S equation. Under the same condition of pressure-inlet, the distribution of symmetry velocity and that of static pressure are compared. The result of the analysis indicates that conical nozzle outlet can reach subsonic or sonic flow. It is fit for low speed and low pressure situation. The gas jet from the new design supersonic nozzle working at design work pressure has better properties than those of other nozzles. So it is better for thick-plate and or high-speed laser cutting. It is obvious that the results of CFD numerical analysis are consistent with the shadowgraph. Thereby it is an effective way to optimize the nozzle according to the performance of flow field.
查看更多>>摘要：Laser cladding rapid manufacturing technology is a kind of new developed advanced manufacturing technology integrating the advantages of rapid prototyping manufacturing and laser cladding surface modification. Due to the complex thermo-physical and metallurgical factors in the deposition process, the cladding layer is liable to crack, which seriously impedes the industrial application of this technology. Experiments of laser cladding rapid manufacturing 316L stainless steel were carried out. The cracking behavior and phenomena has been observed, cracking mechanism of 316L stainless steel was investigated by means of microstructure characterization and phase analysis with optical microscopy (OM), X-Ray diffraction (XRD), scan electronic microscopy (SEM) and phase diagram analysis. Factors influencing the cracking susceptibility has also been studied. Results show that the cracks of 316L stainless steel were hot solidification cracks caused by the high residual stress and separating of the liquid films among dendrites. Through the optimization of process parameters, adding protective atmosphere, etc. cracking sensitivity has been effectively reduced and crack free 316L stainless steel components have been obtained.
查看更多>>摘要：When designing forging manipulators, the bending moments transmitted to the manipulator through the workpiece due to the press motions should be reduced to avoid damage to the manipulator and the workpiece. A resilient system is designed to this purpose. This paper investigates the dynamic behavior of the forging manipulator due to press motions, which focuses on the bending moment transmitted to the manipulator. The Forging manipulator parameters assume primary importance in design, such as the clamp mass, resilient stiffness, resilient damping. A parametric study is committed to provide some helpful solutions for forging manipulator design.
查看更多>>摘要：Multi wire saw is the important basis of integrate circuit, optoelectronic, photovoltaic industry, and it becomes a promising technology for semiconductor wafer production because of its advantage of slicing large ingot into thin wafers with high efficiency and good quality. In the process of moving, the inevitable wiresaw vibration is directly related to the whole process with both benefit and harm. This paper analyses the wire vibration behavior in cutting area, the dynamic model is built by modeling the interaction between the dynamics of wire and hydrodynamic characteristics of slurry flow, available modal analysis provides closed form expressions for the steady state response, obtain the vibration of wire subject to different process parameters on wire saw manufacturing process.
查看更多>>摘要：This paper introduces a method of machining free-form basis-NURBS curve into the field of micromachining. For achieving the optimization of the EMM (Electrochemical MicroMachining) process parameters, sets of experiments have been carried out to investigate the influence of some of the predominant electrochemical process parameters such as machining voltage, pulse on time, feed rate, and electrode peak shape on machining accuracy and quality. A complex shape with structures of several micrometers has been successfully obtained.
查看更多>>摘要：The isothermal precision forging of a screw propeller was studied by means of numerical simulation and experimental forming. The deforming processes of the billet under two different forging patterns were discussed. The distributions of the flow line, the effective strain within the billet and the variation of the forging load during the forming process were analyzed. Results showed that there was a great difference of the effective strain existing between the blades and the wheel hub. The material flow and the distribution of deformation can be improved obviously by adding a core punch on the die. The distribution of deformation and forming load can be changed and controlled by adjusting the process parameters. The forging die was designed and manufactured according to the simulation results and perfect precision forgings have been acquired. Both of the simulation and the forming test showed that the precision forging of screw propellers could be formed with the isothermal precision forging satisfactorily.
查看更多>>摘要：A sequential coupled three-dimensional thermo-mechanical analysis was conducted first to simulate friction stir welding (FSW) of aluminum alloy. In thermal analysis, the model included adaptive heat source, contact heat transfer both between work piece and clamps and between work piece and backing board etc; in the mechanical analysis, the model involved contact interaction both between work piece and clamps and between work piece and backing board, mechanical load of tool etc. The simulation results indicate that the longitudinal residual stress is unsymmetrical about weld centerline; the magnitude of longitudinal residual stress for FSW process is lower than that for fusion welding process. Based on simulated results of FSW process, a three-dimensional elastic-plastic analysis was then carried out to simulate rolling process, the simulation result show that rolling process not only causes a marked reduction in the longitudinal tensile residual but also reverse the sign of the longitudinal residual stress.
查看更多>>摘要：Constraint-based model reconstruction is one of the key research problems in recent reverse engineering. Surfaces of structural parts are mostly quadratic and have mutual constraints. Aiming at this feature, the paper proposes a method for conducting constraint-based synchronous fitting on multiple surfaces. Synchronous fitting is carried out through constraint optimization method, the constraints among surfaces can be maintained and the original design intents incarnated.
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