Advanced Materials Research Vols. 189-193

Abstract: Application of digital aerial camera was a milestone in the development of Photogrammetry and Remote Sensing. The new digital sensor leads to the changes of remote sensing imaging models. Generally, remote sensing imaging models have two kinds: geometric model and radiative model, in which radiative model mainly focus on the radiative quality of remote sensing images. In this paper, a new kind of airborne camera, namely Twice Imaging Digital Camera (TIDC), is introduced, which integrates the advantages of film airborne camera and digital one. It adopts twice imaging techniques to acquire large format, strict central projection images. The radiative transfer model of TIDC is built on the physical processing of digital imaging. The intermediate imaging device of TIDC influences digital images’ quality badly, such as luminous intensity distribution, decay and noise. For this reason, the approach of light tracing based on Monte Carlo is used to simulate radiative transfer in TIDC and test the performance of the intermediate imaging device. The importance of this work is: The Monte Carlo simulating experiment proposed by this paper can be widely applied in the simulation and modeling of other digital imaging systems, and has great practical value in the evaluation and optimization of image quality, the improvement of remote sending imaging system, as well as the estimate of image acquirement results.

Abstract: Vanadium-Chromium composite layer is formed on the surface of cast steel by the method of V-EPC cast penetration. The dry sliding friction wear properties of composite layer are studied on MM200 friction wear testing machine in this paper. The wear surface feature of samples is also observed by SEM and the wear mechanism of samples is analyzed. The result has shown that comparing with the matrix, the wear resistance of composite layer is advanced evidently. The wear rate of composite layer is only eighth to matrix. With the increase of load and the decrease of Vanadium iron in penetrating regent, the wear rate of composite layer increase. The mechanism of composite layer is mainly oxidation and fatigue flake produced by the initiation and expansion of crack.

Abstract: The ferrohydrostatic pressure is an important magnetization characteristic for the ferro-fluid used as the working medium of shock absorber or as a leak-proof dynamics seal of rotating shaft. To generalize and analyze the experimental results, an analytic formulation of magnetic pressure derived from the Ferrohydrodynamics (FHD) Bernoulli theory is constituted. Meantime, an auxiliary testing mechanism on the magnetic levitation, features as an easy, economical and efficient utility, is then set up in this study and which is quit different from the expensive cost required in precise VSM measurement system. While compared with above results, a good agreement will be accessed within the working interval of magnetic flux 0 ~ 60 mT.

Abstract: The solidification model is vital to the simulation of casting process with mushy zoned involved. The author has built a multicomponent model for solidification which is derived from the principles of fluid dynamics. The model has been realized on the commercial CFD package, in which the solid and liquid of metal are united in one frame. In this model the flow behavior of solid is constrained by increasing the viscosity, the latent heat and the buoyancy are also considered, and the key point is the effect of solid fraction on the flow in the mushy zone. The details of flow can be captured even in the mushy zone by using this model.

Abstract: Based on the first-principle calculations, we present a study for p-type ZnO doping. The calculated results show that (F, Li) codoping can suppress the formation of interstitial Li because the formation energy of F_O-Li_Zn is lower than that of F_O-Li_i under O-rich condition. However, it is also found that F_O-Li_Zn codoping could not realize p-type ZnO because F_O-Li_Zn forms a fully passive complex. Interestingly, we further find F_O-2Li_Zn is a stable acceptor that has lower formation energy and shallower transition level under O-rich condition. We expect this study might be helpful for synthesizing good p-type ZnO by controlling (F, Li) codoping.

Abstract: : The LT-MFS approach is proposed to solve two-dimensional transient heat conduction problem in functionally graded materials (FGMs). First, a Laplace transform approach is used to move the time variable. Then, a fundamental solution in Laplace space for FGMs is constructed. Next, the solution in Laplace space is approximated by the linear combination of fundamental solutions. Further, Stefest’s algorithm is employed to convert the results in Laplace space back into the time–space domain. Finally, the method is tested on several benchmark examples. The results demonstrate well the efficiency and accuracy of the proposed method.

Abstract: Based on the characteristics of PQF deformation process, a thermal-mechanical coupled model of this process is established by the three-dimensional elasto-plastic finite element method. The simulation according to practical rolling process of a certain factory is completed. Some important parameters such as the finished size of the rolled product, the temperature variation curves of the key nodes on the tube, the rolling force and torque of each roller are predicted during this simulation. Comparison between simulation solutions and experiment results shows a good agreement, which means this model is capable of simulating PQF deformation process as well as forecasting product quality.

Abstract: The influence of process conditions on the formability of injection-molded PX0034 (9% talc-filled PP) automobile B column mounting trim applied as a model has been studied in current work. This study has been focused on the interactive influence of melt temperature and mold temperature, the interactive influences of injection time and packing time and the influences of packing pressure. Weighting the effect of optimization is by formability including the values of pressure at V/P switchover, volumetric shrinkage differential at ejection, and maximum warpage. Aforementioned values were obtained by numerical simulation of the whole molding process using commercial dedicated code Moldflow. Results indicate that the combination of mold temperature at 25 °C, melt temperature at 220 °C, injection time at 2.2 s, packing time at 16 s and packing pressure at 90% of the filling pressure is the optimal setting for formability of this trim. The simulation results obtained under the optimized parameters are that the pressure at V/P switchover is 27.29 Mpa, the shrinkage differential at ejection is 6.55 %, and maximum warpage is 3.072 mm. Good correlation is highlighted between the experiments and the simulations by comparing effects of the global optimization in formability, which verifies the validity of the optimal combination.

Abstract: An image-based microscale analysis was conducted by using finite element method (FEM) to simulate the thermal residual stresses in directionally solidified eutectic (DSE) oxide ceramic composites from the thermal expansion and elastic properties and the microstructure features of the constituent phases. This microscale analysis allows a real simulation of morphologies of constituent phases such as size, array and shape. Meanwhile, this model can be applied not only for the calculation of thermal residual stresses, but also for the calculation of mechanical properties. In this work, simulations focus on the distribution of thermal residual stresses in the directionally solidified eutectic (DSE) Al₂O₃/ Y₃Al₅O₁₂ (YAG) ceramic composite. A good agreement between simulated and measured thermal residual stresses was observed.

Abstract: Using the method of physical simulation, the vertical extrusion process of thick-walled seamless steel pipe is studied. According to the study and analysis focusing on the die structure and lubrication condition, optimized die parameter which is used for hot extrusion of ferrous metal and a reasonable die - billet composite lubrication program are achieved. Necessary reference and basis are provided to master not only the extrusion process of large diameter thick-walled long pipe, but also the quality control technology.