Advanced Materials Research Vols. 314-316

Abstract: The forming process simulation and springback prediction of an automobile body panel is implemented by using JSTAMP/LS-DYNA. Yoshida-Uemori model is selected to characterize the anisotropic material behavior of sheet metal during forming. Simulation predictions on spingback are compared with experiment measurements along with numerical results from other material models to demonstrate the effectiveness and accuracy of the Yoshida-Uemori model.

Abstract: Abstract: It had been put forward that a new method to establish material constitutive model based on extrusion test, which was that the material constitutive model was determined with the Arrhenius equation according to the extrusion test data. The tube extruding test of supper-alloy Inconel625(IN625) had been done on 16300kN extrusion machine. According to the extrusion test data and the Arrhenius equation, it had been determined that the constitutive model of supper-alloy IN625 based on extrusion test, and the relative errors between calculation results of the model and experiment results are less than 7.8%. The suitable conditions of the constitutive model of supper-alloy IN625 are that the temperature being 1150°C～1200°C, and extrusion speed being 15～60mm/s, and strain-rate being 1.86～7.44.

Abstract: In this paper, the method of “floatation—microwave magnetic roasting—low intensity magnetic separation” which aims to utilize the iron and Nb mineral in the Bayan Obo tailings was investigated. The results show that the method of “floatation—microwave magnetic roasting—magnetic separation” is effective and simple, and the recovery of iron and Nb in the whole process is up to 80% and 68% respectively. The step of microwave magnetic roasting is researched carefully, and the best magnetic roasting result is obtained at 650°C, and the roasting time is 10min.The best result of magnetic separation is obtained at the magnetic intensity of 220KA/m. Iron ore concentrate separated by magnetic separation can be used for iron making directly because the grade can reach about 62~64.4%. And the grade of Nb can reach up to 2.16%.

Abstract: Considering the technical status and existing problems of traditional silicon wafer chemical mechanical polishing (CMP), especially for the diameter of silicon wafer increasing, constantly, the surface quality and efficiency of silicon wafer polishing are becoming an urgent problem to be solved, so the research subject of ultrasonic vibration hybrid polishing new technique was proposed. By means of mechanism theoretical analysis research, firstly, the processing mechanism of hybrid polishing was studied systematically. An investigation of polishing mechanisms based on the micro-contact model between the polishing pad and the polishing surface of silicon wafer was developed. Polishing mechanism theoretical analysis shows that when ultrasonic vibrations combined with mechanical and chemical, the performance of polishing slurry is improved in the process of CMP, therefore to create favorable conditions. To verify the established theory, then, a series of experiments to investigate the traditional CMP are conducted, as well as the polishing tool with the forms of ultrasonic vibration, the polishing pad, the polishing surface quality, velocity at polishing point v, and slurry supplying Q on silicon wafer polishing. Experiment findings showed that, in the same polishing conditions, especially, hybrid polishing by ultrasonic-elliptic-vibration has gained more advantage over the effect of silicon wafer polishing. When ultrasonic-elliptic-vibration is put in polishing tool, the silicon wafer polished surface roughness Ra from the traditional method of polishing 0.077μm going down to the 0.042μm, the no-smooth rate KR which describes the polished surface morphology is significantly improved, and the material removal rate increases by 18%. Experimental research findings of the surface quality and the material removal mechanism are shown to be consistent with the theoretical analysis.

Abstract: Through compassion of relative merits of the existing two control methods of straighten anti-curve line and chord line measure for cold-formed profiles, a three-pivot chord angle control method of non-endpoint measurement was proposed in this paper, and its feasibility was proved by using mathematical deduction. Using mapping method, the forming of profiles can be controlled by the only one set of orderly array chord angles and chord lines obtained by a spline curve of profiles, and meanwhile, the length of automation feedstock in forming process of profiles was explored. The present research achievements can provide a good theoretical basis for the further application on controlling profile forming with the chord angle measurement.

Abstract: The quick plastic forming (QPF) behavior for fine-grained AZ91D magnesium alloy sheet with the thickness of 1.0 mm and the grain size of 6.0 µm was investigated. Free gas bulging tests were conducted under different gas pressure for 300 s in the range of 250-400°C to investigate how the temperature and pressure impact on the formability of QPF. Free gas bulging test results show that the bulge height of semisphere part exist the peak value of 33 mm under the gas pressure of 0.5 MPa at 400°C. QPF tests of cup part were performed based on the free gas bulging test results. A cup part with the height of 20 mm which both of surface quality and fillet radius were satisfactory was formed using a two-stage loading path at 400°C during 300 s. Furthermore the microstructural revolution law during the QPF was discussed. The larger the thinning rate of parts is, the smaller the grain size will be.

Abstract: Using orthogonal test, the influence of variable mixing proportions of recycled coarse aggregate, polypropylene fibre and air entraining and water-reducing admixture on the anti-penetration capability of chloride ion of recycled concrete is analyzed. And the mechanism of resistance to chloride ion permeation concerning different mixing proportions of the materials is figured out. After that, basing on the effects of these materials on the durability life of recycled concrete in chlorate surroundings, the sequence is worked out: first, air entraining and water reducing agent, then recycled coarse aggregate, last one, polypropylene fibre. Employing Fick’s second law, the durability life of recycled concrete applied in chlorate environment is estimated. As a result, evidences for the practical application of recycled concrete are provided for its use in the northern cold areas and the places along the coast.

Abstract: As prosperous in automobile and aerospace industries, the competition in machining industry is getting fierce. The requirements for product lie on not only the improvement of the quality, but also the processing speed. The Nickel based superalloy can maintain a very good strength under highly elevated temperature, so it is wildly applied to the components and parts which need to resist to high temperature, such as blades of aircraft turbine engines, rotors, turbine parts for nuclear power plants, heat exchangers, reciprocating engines, heat-treating equipments, liquid rockets, space vehicles and equipments for chemical and petro chemical industries. Nevertheless, Nickel based superalloy’s high strength, low thermal conductivity and working hardening will lead to a short cutting tool life and low efficiency in machining. At the same time, AISI4340 is also widely applied to processing parts for gears, piston, automobiles and machines.

Abstract: The hardening behaviours of transformation induced plasticity (TRIP) steels depended on the martensite transformation from the retained austenite. As a key factor, pre-strain can influence martensite transformation during sheet metal multi-step processes. In order to learn about the material’s properties after pre-deformation, the effect of pre-strain on mechanical behaviours of TRIP steels has been investigated with the strain-induced martensite transformation in pre-strain condition in this study. The analyzed results show that: Hardening rate, strain hardening exponent and necking strain of TRIP steels are related to martensite transformation in deformation

Abstract: This paper presents a novel hinge mechanism for deployment of spacecraft subsystems such as antennas, solar arrays. By using Axiomatic design theory, the conceptual design of the hinge mechanism is suggested, which has not only high deployed stiffness and low deployment shock but also does not require lubrication and accurate fabrication. That is, optimization of deployment torque and maximization of the deployed stiffness can be possible since this suggested hinge mechanism is decoupled design. And the suggested hinge mechanism is fabricated and tested to evaluate the feasibility. Quasi-static analysis is performed to optimize deployment torque for low deployment shock by using FEM. Also, the bending stiffness is measured by 4 point bending test.