Abstract: Through the incorporation of nano sized Titanium Carbonitride powders into the Al2O3 matrix, an advanced Al2O3/Ti(C7N3) nanocomposite ceramic die material was fabricated by vacuum hot pressing technique. Effects of the content of nano Ti(C7N3) on the microstructure and mechanical properties of the nanocomposite ceramic die material were investigated. It indicates that both flexural strength and fracture toughness were increased noticeably compared with the pure micrometer sized alumina ceramic. Toughening mechanisms of the ceramic composite were also analyzed. It reveals that the intragranular/intergranular microstructures and the resulted transgranular/intergranular fracture modes are the main causes for the reinforcing and toughening of the nanocomposite ceramic die material.
Abstract: A simple and economical powder metallurgy forming process known as warm compaction was employed to fabricate a Cu-Ti3SiC2 particulate reinforced copper matrix composite for electro-friction purpose. Copper matrix composites reinforced with 5, 10, 15 mass% Cu coated Ti3SiC2 particulate were prepared by compacting the powder mixture with a pressure of 700 MPa at 145°C, and then sintered at 1000°C under cracked ammonia atmosphere for 60 minutes. Their density, hardness, tensile strength, elongation and electrical resistivity were studied. Result showed that within a reasonable limit, the addition of Ti3SiC2 particulate can increase the hardness of the composite without losing much of electrical conductivity. Sintered composite with 5 mass% Ti3SiC2 has an ultimate tensile strength of 182 MPa with an elongation of 10%, a hardness of HB 68 and a resistivity of 8.0×10-8Ωm. Compared with the samples using uncoated Ti3SiC2 particulate, the resistivity of the samples prepared by using the Cu coated Ti3SiC2 particulate have a better conductivity, but have a slightly lower mechanical property.
Abstract: Rheoforming is becoming the choice of the casting industry which relies on the semi-solid slurry for high integrity structural parts. The potential of rheoforming with LSPSF (Low superheat pouring with a shear field) for aluminum alloys was investigated in the present work. High quality semi-solid slurries of a series of aluminum alloys were manufactured by LSPSF process, such as casting alloy A356, high strength alloy 201, secondary die casting alloy A380 and wrought alloy 2024, 6082 and 7075, in which the primary α-Al presented spherical, small and homogeneous distribution, especially with zero-entrapped liquid. Applications of LSPSF in high pressure die casting process and squeeze casting process were presented. Results showed that LSPSF rheoforming could improve microstructures and increase mechanical properties.
Abstract: This study aimed to create a multi-cavity and non-uniform thickness die casting for flowing balance. The die casting processes involved a hot-chamber die casting experiment and computer aided simulation to explore the flowing condition of the molten metal in the metal molding process. Computer-aided mould flow analysis software FLOW 3D V9.2 was applied to simulate the filling stage of zinc alloy in the mould cavities. The design parameters of the mould included four variables relating to the gate: width, position, shape, and thickness of cross-section.
Analysis results shows that the primary goals of balance design include two things: (1) the flowing path of molten metal was shortest; (2) the mould cavity was easiest to fill with molten metal. The flowing balance design used analysis software to simulate the flowing condition of the air, which produced an air trap. The melting metal motive force pushed air into the slug well in order to reduce the production of pores. The experiment confirms the actual flowing situation of zinc alloy with a nearly 95% accuracy.
Abstract: The objective of this study is to construct the forming rule for hourglass-like tube with magnesium alloy during hydro-forming and offer the analysis results as a guideline for magnesium alloy forming in industry. AZ31 magnesium alloy circular tube is used as the billet material for hydro-forming with hydraulic pressure as the main forming power combined with the mechanical auxiliary force from the punch to fabricate the hourglass-like tubing products. A finite element based code is utilized to investigate the forming characteristics of hourglass-like tube forming, by changing process parameters such as punch velocity, hydraulic pressure gradient and tool-workpiece interface friction etc. to investigate the material flow of tube filling, wall thickness variations, and stress and strain distributions. And the abductive network is in turn applied to synthesize the data sets obtained from the numerical simulations. Consequently, a quantitative prediction model is developed for the relationships among the process variables, corner radius and minimum tube thickness in the process of hourglass-like tube hydro-forming with magnesium alloy. The results show that proper mechanical force can help material flow, prevent large strain deformation from falling into the area of negative strain hardening rate, enhance the magnesium alloy to become easy in forming and make tube fitting may to be formed successfully.
Abstract: Hot bending and die quenching for U-shaped parts with ultra-high strength boron steel were experimented and simulated to study its quenching effect and accuracy. The results indicate that through the hot contact bending and die quenching, bending parts with higher strength and forming precision than that of cold stamping can be achieved. And the hot contact bending improves the quenching effect at the bottom of the bending part. The springback of hot contact bending decreases gradually when the blank holder force (BHF) increases, which is mainly negative for the impact of the thermal shrinkage moments. The numerical simulation results are consistent with the experiments’. Therefore, it verifies the reliability of finite element model and lays the foundation for the numerical simulation of the hot stamping process applied in complicated shape parts’ production.
Abstract: The influences of four parameters such as young’s modulus, yield ratio, punch radius and blank thickness on the springback of diaphragm of automotive horn are analyzed by combining experiment with FEM (finite element method), and the springback laws of the parameters’ interaction are revealed. The results show that the springback of diaphragm is influenced by the yield ratio of material evidently, but is influenced by punch radius slightly when the parameters interact. However, the influence of punch radius increases greatly when the young’s modulus is very low. Therefore, the influence of the parameters’ interaction must be considered so as to control the springback effectively when the forming scheme of diaphragm is designed.
Abstract: The impact line is a remarkable disadvantage in the auto body panels forming. It is difficult to study because of the complexity shape of automotive panels. The finite element models of hyperboloid shallow shells that can represent automotive panels are established, and suitability of finite element analysis to induce the impact line of automotive panel is carried out. The experiment test method for determining impact line is presented also. The criterion and research technique of auto body panels impact line are introduced. The consistency of results of simulation and experiment shows that the numerical simulation on research of impact line is accurate and feasible. Finally, research works of simulation and experiment on controlling impact line measures are carried out: effects of blank holding force (BHF), sheet thickness and lubricating modes on the impact line are obtained.
Abstract: Multi-point positioning tooling is a flexible fixture used in assembly of contoured panels in aircraft manufacturing. It uses many numerical controlled punch elements to configure a flexible tooling system which shape contour can be adjusted according CAD data. The paper is focused on analysis of the operations to be done on the formed panel when they are clamped and supported on the MPPT. From the results of finite element analysis, it can be concluded that the interval between punches is the key factor which affects accuracy of MPPT. And also sheet thickness, material and geometric shape have influence on performance of MPPT.
Abstract: The sheet forming simulation of rectangular box was conducted by finite element method (FEM), the forming process experiment, further, was investigated, so as to understand the effect of the form of blank holder and the manner of blank holder force (BHF) on the complicated parts forming. In my study, a kind of low carbon steel was investigated, and its mechanical properties were obtained by simple tension tests. The outermost contour of the blank shape was determined by “one step method”. Furthermore, the finite element model was constructed by ANSYS parametric design language (APDL), which has characteristic of grid meshing by Belytschko-Tsay (BT) shell element, applying anisotropic constitutive equation of Barlat yield criterion, dealing contact by penalty function method and using adaptive mesh algorithm in the simulation process. Then the forming process simulation of rectangular box with segmented variable BHF was conducted. On the basis of analyzing the work principle and technical parameters of XP3CEF-100 hydraulic press, the rectangular box drawing system of segmented VBHF was established, which was made of hydraulic press, rectangular box drawing die of segmented blank holder, hydraulic part of blank holder and control part. Finally the low carbon steel forming tests were fulfilled by the rectangular box drawing system on the basis of the simulation result.