Formation mechanism and criterion of linear segregation in ZL205A alloy

The experiments and numerical simulation were conducted for ZL205A aluminum alloy cylindrical shell casting. The formation mechanism of the linear segregation produced by the low pressure die casting (LPDC) process was investigated. And the heat transfer of the casting during solidification process was analyzed by simulation technique, resulting from the information of linear segregation obtained by plenty of experiments. The new linear segregation criterion was proposed through the simulation and experimental results. It was found that the melting metal with high Cu contents was feeding the crack shrinkage formed by the tearing under the effect of feeding pressure during the later solidification, which led to the formation of linear segregation. The control methods for the linear segregation were suggested based on the proposed mechanism. Finally, the criterion of linear segregation was confirmed by the production of the actual castings.

工程图学中引入“立体造型”概念的探讨

论述了工程图学中引入计算机“立体造型”概念的必要性，以实例说明了引入操作的可能性以及引入的实际意义。

Fractal character of lenticles and its influence on sediment state in tailings dam

The distribution of tailings lenticles reflects the sediment state of tailing dam, and has a great influence on the stability of the dam. In order to disclose the distribution law of tailings lenticles in theory, 12 geological cross-sections, including 7 cross-sections of tailings dam constructed by the upstream method and 5 cross-sections by the middle line method, were analyzed with box dimension method. The results show that the distribution of tailings lenticles has better fractal character with box dimension from 1.290 7 to 1.513 6. The box dimension of the tailings dam constructed by upstream method is nearly 1.50 and that by middle line method is 1.30. Thereby the values of lenticles dimension have obvious relation to the method of constructing dam, and reflect the sediment state of tailings dam with the rule that smaller value means better state.

A New Arrangement with Nonlinear Sidewalls for Tanker Ship Storage Panels

Sloshing phenomenon in a moving container is a complicated free surface flow problem. It has a wide range of engineering applications, especially in tanker ships and Liquefied Natural Gas (LNG) carriers. When the tank in these vehicles is partially filled, it is essential to be able to evaluate the fluid dynamic loads on tank perimeter. Different geometric shapes such as rectangular, cylindrical, elliptical, spherical and circular conical have been suggested for ship storage tanks by previous researchers. In this paper a numerical model is developed based on incompressible and inviscid fluid motion for the liquid sloshing phenomenon. The coupled BEM-FEM is used to solve the governing equations and nonlinear free surface boundary conditions. The results are validated for rectangular container using data obtained for a horizontal periodic sway motion. Using the results of this model a new arrangement of trapezoidal shapes with quadratic sidewalls is suggested for tanker ship storage panels. The suggested geometric shape not only has a maximum surrounded tank volume to the constant available volume, but also reduces the sloshing effects more efficiently than the existing geometric shapes.

Process of back pressure deep drawing with solid granule medium on sheet metal

The experimental die apparatus of the solid granules medium forming on sheet metal was designed and manufactured.Typical parts,such as conical,parabolic,cylindrical and square-box-shaped components,were successfully trial-produced as well.According to the analysis of the changing trends of the cross-section shape and the wall thickness during the process,it can be found that the shape of the free deformation zone of the sheet metal,which is the most critical thinning area,can be described as an approximately spherical cap.According to this forming feature,back pressure deep drawing technology with solid granules medium on sheet metal was proposed to restrain drastic thinning at the bottom of the part through the joint friction effect of solid granules medium,the back pressure tringle and the sheet metal.Therefore,the deep drawing limit of the sheet metal is significantly improved.In order to fabricate thin-walled rotary parts with great drawing ratio and complex cross-sections,a finite element model based on the material property test of the solid granules medium was established to optimize the scheme of the back pressure deep drawing.The effects on the forming performance of sheet metal from back pressure load and the approach of blank holding control were analyzed through this model.

Shape-controlled growth of SrTiOz polyhedral submicro/ nanocrystals

A series of SrTiO3 polyhedral submicro/nanocrystals with systematic morphology evolution from cubic to edge-truncated cubic and truncated rhombic dodecahedra have been synthesized by using a series of alcohol molecules with different acidities as surfactants. The concentration and pKa value of the alcohols both play important roles in determining the size and shape of the SrTiO3 polyhedral submicro]nanocrystals. The adsorption energy of alcohol molecules on SrTiO3 [110] facets depends on their pKa values, which are therefore critical for morphology control. Using the same strategy, a series of BaTiO3 polyhedral submicro/nanocrystals with systematic morphology evolution have also been successfully prepared.

Effect of orifice geometry on bubble formation in melt gas injection to prepare aluminum foams

The bubble formation process at submerged orifices with different geometry is investigated in the preparation of aluminum foams by gas injection method.The bubble profile on a horizontal plate is calculated by quasi-static analysis through Laplace equation.The bubble formation process is then distinguished into three stages:nucleation stage,growth stage and detachment stage in wetting and less wetting conditions based on the force balance analysis.In addition,the bubble size at high Reynolds number is obtained by considering the contribution of buoyancy,pressure force,inertial force,drag force and surface tension based on the three stages of bubble formation.The bubble size is confirmed to be sensitive to the equivalent contact angle,which consists of two terms including the contact angle and the wedge angle.Therefore,the wedge angle is introduced in the design of gas outlet orifices for the purpose of decreasing bubble size generated.The experimental study is conducted at three different types of stainless steel orifices under constant gas flow rates(0.05–2 L/min).It is clarified that the orifice geometry and the orifice size are both responsible for the cell size of aluminum foams.The experimental results for three different types of orifices show a consistent trend with the theoretical predictions at various gas flow rates.In the design of orifices to generate small bubbles in the melt,the wedge angle that coordinates with the contact angle is thus suggested.

Propagation characteristics of six-core photonic liquid crystal fibers

We demonstrate a new kind of multi-core photonic liquid crystal fibers (PLCFs) which have six liquid crystal cores arrayed in the ring-type geometry and separated by the air holes. Through analyzing the structure of this kind of PLCFs, it can be found that they have the ability to resist the structure deformation. Due to the effective index of the liquid crystal can be adjusted by temperature and wavelength, the energy in the six liquid crystal cores is increased with the temperature increasing and wavelength decreasing. The effective index of the PLCFs is decreased, the effective fundamental mode area is increased and the dispersion properties are gently affected with the wavelength increasing and temperature decreasing.