Materials Science Forum Vols. 575-578

Abstract: This paper analyzes the forming process methods of fin used in CPU chip to emit heat. The whole process is blanking, the first forging forming, the second forging (sizing), and trimming. The chamfer design of CPU fin blank is simulated by finite element analysis. The optimized chamfer 1.6 mm is available. Semi-enclosed cold forging of progressive dies is put forward. The newly designed transfer unit is applied, which unifies the merit of high efficiency of the progressive dies and the high material-using ratio of the project die. Quick disassembly structure is designed and pins are used as quick disassembly pins by means of ball bearing bushing. The unique processing of the shearing scrap structure is adopted when designing the inverted trimming dies. Compared with the traditional die, the mechanization and electrization are realized to increase the production efficiency and get highly precise CPU fin.

Abstract: Based on viscosity hydrodynamics and hydro-finite element theory, flow field of the main-control reversing valve of electrical-hydraulic hammer was simulated. The N-S equations were discretized by the finite volume method. Hydraulic valve’s pressure and velocity distribution were analyzed in the working process. Relationship between the structure of the flow field (velocity, pressure, flow separation and reattachment, appearing and disappearing of vortices) and the energy loss and component performance was proposed. The design of the hydraulic valve structure was optimized which turns out to be high-efficiency and energy-saving

Abstract: The main problem in bending process of sheet metal is that it is difficult to control bending springback accurately. Springback produced from the unloading of bending makes the shape and size incongruent between bending workpiece and working portion of die. Because the final shape of bending workpiece is related with the whole deformation process, the geometric parameter of die, material performance parameter will have great effect on springback. Therefore, the springback problem is very complicated and the prediction and control of springback is the key to improve the accuracy of bending workpiece. Taking the V free bending of wide sheet as an object of study, the neural networks technology and data acquisition system based on LabVIEW are used to establish intelligent control experiment system for V free bending of wide sheet metal. The control accuracy of system is high and it provides the basis for the realization of intelligent control for V-shape free bending of wide sheet metal in practice in future.

Abstract: Forecast of discharge parameters is one of the key problems needed to solve urgently for applications of electromagnetic forming technology (EMF). In this work, the forecast of discharge voltage for electromagnetic tube forming has been investigated through a combination of the sequential coupling numerical simulation of EMF process and the design optimization of tube deformation. The optimum design of tube deformation during EMF process is discussed. The relative error between the experimental value and the forecast one is less than 5.9%, which indicates that the discharge voltage forecast method is feasible. This forecast method will be a favorable way for the optimum design of electromagnetic sheet metal forming and tube forming with die.

Abstract: As one type of the important alternative fuel containers, composite cylinders are widely used in compressed natural gas vehicles (CNGV) all over the world. Compared to traditional metal containers, the performance of composite cylinders is more complicate because it is difficult to analyze the material characteristics and the influence of manufacturing process. With the aid of numerical simulation, the damage tolerance of one type of composite cylinder was investigated in this paper. Firstly, the usual damage modes and sizes that are generated in the serviced composite cylinders are classified to illustrate the dangerous parts in the composite cylinders. According to the manufacturing process of composite cylinders, the fiber material characteristics that account of the effects of heat and resin are evaluated to conduct the numerical simulation. Under the damage modes and sizes such as initial flaw, fiber fracture and delamination that are distributed in the cylinder in terms of the classification, the performance of composite cylinder are carried out. With the convenience of numerical simulation, the map of the dangerous sites under the elaborate damage modes and sizes is given to evaluate the running condition of composite cylinders in practice. The quantitative results are more useful to show the damage tolerance of composite cylinder than the traditionally qualitative check way and guarantee the running of CNGV.

Abstract: Steering knuckle, which has strict requirements with regard to dimensional precision and quality, is a key component in cars. Conventional plastic forming methods are involved with intricate procedures and high energy consumptions. Normally, a 40 MN hot die forging press or a 100 KJ electro-hydraulic hammer is required to produce the steering knuckle. Closed die forging, which is a new precision forming technology developed in recent years, has some virtues, such as good mechanical properties, easy to form and improving of metal plastic deformation. Aiming at Jetta steering knuckle in this paper, the technology of two forging steps in one heat is presented. This technology is mainly composed of precision pre-forging, which is a closed die extrusion with the extrusion belt, and open finish-forging. The pre-forging process and finish-forging process are numerically simulated using the FEM software DEFORM-3D. For the closed die extrusion forming process, which is the key component of the technology, some key problems were researched, such as the flowing and filling regularity, extrusion-belt length, punch size, punch movement, lubrication and the relationship between the clamping pressure and the extrusion pressure. For the finish-forging process, the flowing and filling regularity of the finish-forging part was studied to verify the correct shape and dimension of the pre-forging part. Numerical simulation with regard to the pre-forging process shows that the closed die forging can not only help to form the pre-forging part, but also decrease the extrusion pressure to be less than 8 MN, extend the mould’s service life and increase the utilization ratio of materials to be more than 75%. Numerical simulation of the finish-forging process shows that the pre-forging part design is rational. In addition, the forging experiments were carried out using the dies designed in particular. The experiments show that the technology is feasible and can markedly improve the mechanical property of the forging piece.

Abstract: On the basis of thermo-mechanical coupled FEM model which characterized the composites liquid-solid extrusion process, the constant-velocity and non-constant-velocity extrusion process were simulated by 3D thermo-mechanical FEM. Their influence on forming temperature, forming quality and deforming force was analyzed and compared. In the constant-velocity extrusion process, the results show the over-high and low forming temperature in earlier and terminal extrusion stage were responsible for the surface annular cracks and inner fibers breakage. In the new non-constant-velocity extrusion process, however, the range of forming temperature can be shortened in a reasonable range and the over-high and low forming temperature were thus eliminated. Therefore the forming quality and its consistency can be improved. In addition, the deforming force can also be reduced. The simulation and the mechanisms analysis coincide with the experiment results reported in previous literatures. The study provides the theoretical gist and a new feasible technical scheme to favor the consistency of the extruded product quality in composites liquid-solid extrusion process.

Abstract: A key functional aspect of assembled camshafts is the joining strength between the shaft tube and the cam lobe, which is depended on the assembly or joining method. The assembly process by knurling joining and torque deformation of assembled camshaft were numerically studied and the key influencing factors on the press fit load and joining strength were analyzed. The experiments including to the press fit and torque strength of lobe/tube joining were carried out.The results show that the torque strength of the cam lobe/shaft joining can availably increase by matching cam and tube materials, choosing appropriate knurling form, enlarging magnitude of interference and extending knurling width. The numerical results agree well with the experiments and are significant in the design and manufacture of assembled camshaft.

Abstract: Thermal compression tests of AZ61 magnesium alloy was performed at deformation temperature 150-400°C and strain rates ranged from 0.01s-1 to 10s-1, and the microstructure were observed for deformation specimens. The result shows that dynamic recrystallization (DRX) was happened under the center warm deformation condition for AZ61 alloy. The values of stress peak decrease when the deformation temperature increase, the grain size grows up at the same time. On the other hand, the critical strain increase and the grain size get smaller with the strain ratio increasing. Therefore temperature and strain ratio can make a great effect on the microstructure and mechanical properties of AZ61 alloy, but temperature is a more important factor.

Abstract: Precision forging is an important manufacturing procedure of steel synchronizer gear ring forming. FEM software DEFORM_3D was applied to simulate the forming process and the problems in the forming process were been solved. The important factors those influence on precision forming of steel synchronizer gear ring are studied and the results are verified in practice. The results show that the size of billet, forging temperature, and thickness of web strongly influence the forming quality of steel synchronizer gear ring.