Advanced Materials Research Vols. 314-316

Abstract: The viscous behavior of feedstocks plays the crucial role in Micro MIM. It affects directly injectability of the components and finally quality of the sintered component, because of the possible segregation induced by injection. The studies on viscosity of the feedstocks are realized by a series of the tests, in which a torque rheometer and a capillary rheometer are employed. The effects of binder composition, powder size, temperature and powder loading in volume on viscosity of the feedstocks are investigated. The mixtures of three kinds of binder composition, mixed with 5µm or 16µm 316L stainless steel powders, are evaluated. The best binder composition is determined by comparison of the viscous behaviors among the self-mixed feedstocks and the commercial one. It results in the suitable ranges of heating temperature and powder loading in volume for the feedstocks. The critical powder loading in volume is determined by a series of the capillary tests with the gradual increase of powder loading. These works provide the valuable reference for the research on binder composition and the process of micro metal injection molding.

Abstract: This article analyses the characters of piercing process inside of automobile cover parts. It introduces the designing structure, its advantages and disadvantages in piercing process inside of automobile cover parts by a traditional process and by a new process. The traditional process is using cams across a bridge, but the new process is a creative way that is using PAD built-in standard cams. By comparing two processes, the new creative process is convenient for operations and ensures the combining moulds in one time. This mould has a tight structure and the dimensions are reduced significantly, which is benefit for shortening the moulds’ manufacturing cycle. The new process has some guiding significance for the parts by similar piecing inside process. It has been spread and applied in a cooperative company.

Abstract: New hydraulic bulge method and estimated conjoint results were explored. The equipment’s overall water pressure test is developed to get lining bulge and plastic deformation, to eliminate the gap between lining and shell. Integrated effect was estimated by measured layer gap, stress and strain through hydraulic bulge and pressure increase test. Test results show that: although the preliminary gap is not uniform, even 14~16 mm at some points, but the remnant is only 0.6~0.9mm after hydraulic bulge; cylinder always keeps elastic during the pressure increase test, and the linearity between cylinder strain and initial pressure is more than 0.99 after hydraulic pressure expanding treated; Lower temperature annealing of sheath did not have negatively affect on conjoint effect. It is a new technology with simplicity, safety, low production cost, and no pollution, which will create a new way of metal compound forming.

Abstract: A mathematical model was established to describe the electromagnetic, heat flow and fluid flow phenomena within a combined plasma arc. In the development of the model allowance was made for the conservation of mass, momentum, energy and the Maxwell equations. With the ANSYS finite analysis software, specific calculations were presented for a pure argon system, operating in a laminar mode. The distributions of the current density and velocity of combined plasma arc were gotten. In addition, the influences of process parameters, including arc current, argon gas flow rate and the distance from the nozzle outlet to the anode workpiece, on the velocity along the axial direction and current density distribution along radial direction were evaluated, respectively. The results shows that the velocity and current density of combined plasma arc are much dependent on the working current, while are less sensitive to the argon flow rate and the distance from the nozzle outlet to the workpiece anode.

Abstract: Forming limit curve (FLC) is an important tool for assessing formability of steel metal. It is commonly obtained from experiment, theoretical calculation and finite element method (FEM) simulation. In this study, the FLC of a seamed tube hydroforming is established by combining the failure criterion of strain increment ratio and FEM simulation. The numerical method is verified by tube bulge tests. Then the sensitivity studies are carried out to evaluate the effect of the geometrical features of seamed tube on its formability by numerical approach. Results show that the changes of the formability with the geometrical features of a seamed tube.

Abstract: Sintering temperature influences on sintering process essentially. Laser power and scanning speed determined sintering temperature. Preheat to powder is beneficial to improve the surface temperature uniformity. Stress concentration of part is various in different layer depth. Therefore, the influence of laser power, scanning speed, thickness of spreading layer and preheat temperature on part quality in selective laser sintering(SLS) are main factors. Based on laser energy in Gaussian distribution and mechanism of SLS, with manufactured specimen pieces by molding machine AFS-450, orthogonal experimental design and analysis of variance are adopted to post-treatment. The prototyping sintering parameters are optimized. The result and solution of the experiment are the preheat temperature of 100°C, the scanning speed of 2000 mm/s, the laser power of 24W, the thickness of single layer of 0.2mm for ABS resin. This work can provide optimized parameters in SLS for ABS resin. It will be of benefit to improve the part dimensional precision and strength.

Abstract: Investment casting technique presents more advantages in the production of accuracy and versatility components. The mechanical performance of the ceramic shell is crucial to the quality of the castings. The slurry parameters can affect the properties of the ceramic shell. The purpose of this paper is to investigate the physical properties of primary slurry for titanium and titanium alloy investment casting. Three different slurries (ZrO2, Y2O3 and Al2O3) were evaluated respectively by comparing the parameters: viscosity, bulk density, particle size distribution, thixotropy and suspension percentage of slurries. The results show that the physical properties of primary slurry were mostly determined by the type and content of refractory materials. Refractory particle morphology and the particle size distribution affect slurry rheology and viscosity.

Abstract: This paper describes the research status of the warm stamping at home and abroad. The status of aluminum alloy and magnesium alloy is introduced in warm stamping respectively, using the tensile test, the drawing test, and bending experiments to prove the temperature and other factors have effect on the formability of materials. It also presents the status that using warm forming to solve the spring-back problem of the high strength steels. In addition, the mold and lubrication are also the key problems in warm stamping; they have a corresponding development with the development of warm forming though there are a few scholars specializing in the content.

Abstract: As a contact of vibrational rotary forging is highly nonlinear, the contact area and boundary between rotary toolhead and workpiece had more accurate calculation, made the contact boundary more tally with the actual situation. For a surface effect is of complexity for vibrational rotary forging, a vibrational rotary forging visco-elasticity plasticity model was built, and the visco-elasticity spatial matrix and the visco-plasticity spatial matrix were derived by the generalized Hooke's law in elasticity theory and the increase theory in mechanics of plasticity, then by the finite element founction of MATLAB for the surface effect analyzed during the vibrational rotary forging deformation, it is shown as blow: the surface effect should be appeared with high frequency vibration or low frequency vibration, but there are some conditions for surface effect produced during plastic process, and then the hypothesis that the friction vector is reversal of deformation load, and it is benefit to deformation process during the part of time in vibration period is validated.

Abstract: Multi-way tube on air conditioning header is considered as the research objective .Finite element simulation method is utilized to simulate and analyze the influence of process parameters on branch height such as branch diameter、branches distance、branch numbers、tube thickness and die fillet radius. The result shows that with the increase of branch diameter, die fillet radius and tube thickness, the branch height increases. It also shows that with the increase of branch numbers and branches distance, the branch height decreases generally.