Applied Mechanics and Materials Vols. 217-219

Abstract: Rapid prototyping techniques are ideally suited to the manufacture of aerodynamics research models as these items usually consist of highly complex 3 Dimensional (3D) forms. The fabrication of complex curvatures on traditional Computer Numerical Control (CNC) machines often requires the production of additional tooling supports to allow for full machining of all surfaces. Such a necessity often results in extra cost and fabrication time, as well as a potential loss in accuracy due to any repositioning required to allow machining of internal and external features. It is often necessary to divide the model into additional sections to allow for the machining of internal features which can cause issues with mismatching of adjacent surfaces. The inclusion of small or complex internal features and hollow sections may be problematic if not impossible. In contrast, many rapid prototyping techniques eliminate most of these manufacturing issues due to the additive nature of modern 3D printing processes. Popular techniques for the rapid prototyping of polymers include Selective Laser Sintering (SLS), Fused Deposition Modeling (FDM) and stereolithography. The basic technique reduces a 3D object into a series of thin 2D slices. The 2D slices are then “printed” vertically in succession to produce the final 3D item The “slicing” technique is readily compatible with the formation of complex 3D curvatures as well as internal and hollow features. In addition, any required tooling supports are produced simultaneously with the desired item, which greatly reduces processing time and loss of accuracy due to part repositioning. The necessity to produce a model from multiple sections to allow access for machining of internal features can in many cases be reduced significantly. The characteristics intrinsic to many modern 3D printing techniques are greatly beneficial for the production of complex wind tunnel models made from polymer. The current work describes the design process and features of a wind tunnel model used for research into a novel aerodynamic flow control technique. An additive manufacturing technique was chosen as the most suitable for the rapid, accurate and simplest fabrication process for the model.

Abstract: Using the finite element simulation software Deform-3D , the forming characteristics of pressing, cupping and shell ironing of the thick-walled cannonball body semiproduct were analyzed, and the parameters of shell ironing was optimized. The results show that the load increases sharply at the end of the pressing, while the bottom corner of the billet and the boss are not well formed, which can be finished at the end of cupping; Due to friction, the metal closed to the end face of the punch dose not deform during the cupping process, but rigidly moves with the punch. This part without deformation of the billet is called deformation viscous zone. As the cylinder wall of the billet bears axial tensile stress during the shell ironing, deformation at the bottom and necking would occur easily undercondition of bad lubrication and large deformation. When die-entrance taper is 15º, the workpiece have homogeneous deformation, low axial tension stress and forming load. The forming load of shell ironing can be effectively reduced by good lubrication for die.

Abstract: For premixed abrasive jet，abrasives loaded onto hermetic tank cannot enter the mixing chamber by use of negative pressure and weight and mix with water. A supply abrasive system of premixed abrasive jet was designed and the local flowing tributary was added. The test of supply abrasive and derust were carried. The test of supply abrasive shows the bigger the rate of water flow of the local flowing tributary, the bigger the rate of abrasive flow, and there is linear relation between with them. Regulate the rate of water flow of the tributary, abrasive flow may be controlled. The test of derust examined actual application of the supply abrasive system, and effects of the parameters of abrasive jet on derust performance. The results show the abrasive weight consistency and the flow rate are good. The parameters of abrasive jet are determined, the work pressure is 10MPa, the abrasive weight consistency is 30%, the rate of water flow is 30L/min.

Abstract: The powder metallurgy (PM) nickel-base superalloy GH720 was extruded at 1100°C and the as-extruded samples were treated at 1110°C during 10min, 20min and 30min apart. The microstructure and recrystallization behavior of as-extruded alloy GH720 were discussed. The results indicate that there are two different types of γ' phases: primary γ' phase is mainly distributed on the grain boundary with an average size ranging from 0.3 to 0.5μm and dissolves partially at 1110°C during 30min, whereas the secondary γ' phase is distributed inside the grains with an average size of 50nm and dissolves largely at 1110°C during 30min. Recrystallization mechanism is subgrain nucleation when as-extruded GH720 is treated at 1110°C at which a lot of γ' phase exist. γ' phase inhibits growth of recrystallized grain availably and the uniform, fine and equiaxed grains in GH720 were formed during the extrusion and following heat treatment process.

Abstract: In order to improve the atomization quality of spray forming, the cylindrical hollow jet technology was applied in the atomization process of spray forming, and a numerical simulation for the structure of hollow flow field in front of jet outlet was carried out, the distribution of hollow jet flow field was simulated under different inlet velocities and outflow technologies, and then the experimental verification was performed. The simulation results of single-phase flow field show that with increasing the liquid inlet velocity, the back flow are a can get enlarged, and the lower negative pressure can be generated, which is beneficial for the out flow of liquid metal. The simulation results of two-phase flow field show that the hollow jet can be produced a hollow part. The conclusion basically accords with the experimental result of water flow.

Abstract: In order to obtain the natural frequency, vibration mode and the curves of amplitude-frequency under two supporting ways, dynamic analysis was carried out on the large plane steel gate structures of a hydraulic projects. According to the Chinese machinery industry standard of vibration stress relief, technological parameters and effective range of vibratory stress relief were determined under two supporting ways. Some valuable references of determining technological parameters of vibratory stress relief for the plane steel gate structures and other momentous welding structures were provided through the research results and the conclusions.

Abstract: In the process of cam grinding, the fluctuation of grinding force can lead to the abnormal wear of the grinding wheel, the decrease of the grinding surface quality and even the damage of the grinding process system. The paper took the grinding process of numerical control cam grinding machine as research subject, the grinding force mathematical model was built, the indirect test and control measures were researched and an adaptive control method based on neural network was proposed and applied to the grinding force control of the cam grinding process. At last, the controller was designed and the grinding simulation was performed with MATLAB, which proved that the system could solve the fluctuation of grinding force during the process of cam grinding and the controller was equipped with good dynamic characteristic. The results indicate that the method can realize the purpose of optimal metal removal rate and enhance the grinding quality of cams.

Abstract: This article deals with milling possibilities of nickel superalloy - Inconel 718. The different cemented carbides were applied for cutting process. These inserts were produced by Pramet Tools Ltd. company. This paper discusses durability of cutting inserts, the different intensity of tool wear at various cutting parameters. The most suitable cutting conditions are chosen in the scope of applied tools.

Abstract: Work hardening reserches in metal cutting has an important significance in improving surface quality of the workpiece and the service performance of parts. The paper introduces current researches of the work hardening in metal cutting process, analyses the forming mechanism and influencing factors of the work hardening and discusses the effects of the work hardening on workpiece service performance. At last, the new trends of work hardening researches in metal cutting process are conclusively predicted.

Abstract: Based on experimental method of factorial design, numerical simulation of injection molding using Moldflow software has been done. The effects of the gate number-distribution, melt temperature, packing pressure, packing time, injection time, etc. on volumetric shrinkage and the two-way interactions among factors in injection molding of plastic part have been researched. The regression model for volumetric shrinkage of plastic part has been obtained through multiple linear regression analysis of the experimental data. The optimization model has been established to optimize processing parameters setting leading factors which effect volumetric shrinkage as design variables and regression model of volumetric shrinkage as objective function. The volumetric shrinkage value of plastic part is less than the minimum volumetric shrinkage value of the main experiment, which indicates that the method has a good practical value in engineering.