Advanced Materials Research Vols. 314-316

Abstract: The paper firstly numerically simulates the coupled model of triangle fastening screw threads in the application of ANSYS software. Calculate stress intensity of the screw thread on the axial pressure of 200MPa. The fittest coupled turn number of the screw nut is designed to make sure the strength of coupled teeth and make every turn of the screw thread go on very well and also save material. The maximum equivalent stress of the screw thread changes linearly with the axial pressure. The stress of the thread's root is greater than that of the thread's top so that the root is easily damaged. The paper's research method can apply to the optimal design of the other patterns of screw thread's turn number.

Abstract: A theoretical model of heat transfer for Si3N4 ceramics during micro-detonation of arc strike machining was established. Based on finite element theory, the temperature of Si3N4 ceramics during micro-detonation of arc strike machining was simulated with the aid of COMSOL Multiphysics software, combined with the actual processing, the width and depth of crater impacted by micro-detonation were calculated. The simulation results show that the highest temperature of Si3N4 ceramics is over 12100 °C in a given processing parameters, while the high-temperature zone is quite small; the material removal rate with the increase of pulse width and electricity increases, with the increase of the nozzle radius first increases and then decreases; the diameter to depth ratio with the increase of pulse width and electricity decreases, with the increase of nozzle radius increases. The data gained from the simulation is proved to be accordant with the data gained from experiments.

Abstract: In this paper, we study a simplified single step full discrete scheme for a class of semilinear hyperbolic problems of second order. At first we obtain a system of second ordinary differential equations with initial value by use of spatially discrete finite element approximation with interpolated coefficients. Next in terms of a single step scheme to the time variable for this system we gain a fully discrete scheme with high accuracy. Finally we give the stable and convergence of the full discrete schemes.

Abstract: The stress distribution of the high - pressure grinding roller is an important index of the grinding mill design. A simulation model of high - pressure grinding roller is created by means of finite element method (FEM), utilizing the FEM software ANSYS. At first, the paper calculated the pressure of the high - pressure grinding roller by the grinding materiel mathematical model. Secondly, a physical model is set up material characteristics is defined and the areas are meshed, then the border conditions are established, finally loading and solving are made. The result of the FEM simulation indicated the mathematical model of the grinding materiel is rational.

Abstract: This paper introduces an analysis technology in detecting the alcohol content in human blood after drunken that bases on reflectionof Raman spectroscopy. This is a fast, non-contact, health and safety technology which take advantage of the human skin. The technology has a broad application in rapid detection of alcohol content in human blood.

Abstract: This study describes the results on the performance of one vehicle air conditioning system. The coefficient of performance, evaporator cooling capacity, compressor power consumption, total mass flow rate, vapor mass flow rate, liquid mass flow rate and oil in circulation, pressures and temperatures of refrigerant at every component (inlets and outlets) are measured and analyzed with the variation of the outside temperatures at the evaporator and condenser, the speed of the compressor, refrigerant charge and oil charge. The systematical experimental results obtained from this real-size test system depict the relations between the above parameters in a vehicle air conditioning system, which constitute a useful source for vehicle air conditioning systems design and analysis. The vapor quality (two-phase flow) measurements realized in this work provide an extremely important tool for diagnosing the system performances.

Abstract: For plate steel castings, the foundry technology was designed according to the dynamic directional solidification of proportional solidification theory. Adopting chilling process for the thick and large plane, it may cause the casting basically even cooling. Using self-feeding shrinkage in solidification achieved the dynamic directional feeding of molten steel, and the casting was poured and congealing at the same time. The shrinkage of finally congealing part was fed by small riser. Adopting this foundry technology, the large plane downwards avoided appearing the defects such as sand buckle, slag, pinhole porosity, and pore, etc.; the process yield was greatly increased with this foundry technology, too.

Abstract: The shrinkage cavity defect of the extruded boss is harmful to the quality of fine blanking workpiece and process. To suppress the shrinkage cavity defect, firstly, the boss extrusion is simulated to analyze main features of metal flow and the causes of the shrinkage cavity defects; secondly, some parameters affecting the material flow, such as the size of die and punch, blank holder force, friction coefficient, sheet thickness and counter force, are studied to figure out their influences on the depth of shrinkage cavities respectively; finally, the process parameters of a special workpiece are selected according to research results above, and experiment verified that the selected parameters can suppress the shrinkage cavity defect pertinently. In the paper, the shrinkage cavity defect is systematically studied for the first time, and this provides the base to design and optimize the extruded boss feature in fine blanking process.

Abstract: During the indirect hot stamping process of boron steel, the pre-deformed component undergoes air cooling, one-side-contact cooling and both-side-contact cooling phases successively. The effects of pre-deformation and cooling rate on the phase transformation should be understood before conducting indirect hot stamping experiments of vehicle components. Uniaxial tensile tests of boron steel at RT were carried out to obtain specimens with different pre-strain levels. Then they were heated to 900°C according to the indirect hot stamping process and quenching tests were performed on them at different cooling rates. Metallographic observations were performed on the quenched specimens and their hardness was measured. The results show that the pre-strain at RT has little influence on the phase transformation of boron steel. This is due to the dislocation structure introduced by deformation at RT recovered during the heating process and it is good for the indirect hot stamping. Upper B-pillar parts were first cold pre-formed, and then were heated and hot stamped. The microstructure and hardness results at different locations on the indirect hot stamped components are demonstrated qualified.

Abstract: The Ti3Al/TC11 dual alloy bar joined by electron beam welding was deformed by near isothermal forging and then processed by gradient heat treatment. Afterwards, the mechanism of interface strengthening has been investigated according to the microstructure evolution and properties. The results show the brittle phases formed in the re-solidification can be broken by near isothermal forging; the lattice distortion energy is increased obviously due to deformation, so the nucleation ratio of recrystallization is improved, which method is fine-crystal strengthening. After the dual alloy deformed by near isothermal forging is further processed by gradient heat treatment, the room temperature tensile strength of the joint is higher than that of the Ti3Al alloy; the high temperature tensile strength of the joint is equal to or higher than that of the TC11 alloy. The reason is that the finer and phases are precipitated from the phase transus microstructure in the welding interface, which produces the effects of fine-crystal strengthening and dispersion strengthening.