Advanced Materials Research Vols. 472-475

Abstract: Varied values of moisture diffusivity estimated using Crank’s equation with different initial moisture content, equilibrium moisture content and sample thickness are often reported. However, a theoretical explanation to this phenomenon is not available to date. To explore the possible reason of this phenomenon, a Fick’s second law diffusion equation for drying samples assumed uniform initial moisture distribution and negligible external resistance is solved numerically and the solutions as drying data is used to estimate the moisture diffusion coefficient of the sample through the equation reported by Crank. The result shows the Crank’s equation used to estimate moisture diffusion coefficient could not be theoretical solution of the Fick’s second law diffusion equation and the estimated value of moisture diffusion changing with initial moisture content, equilibrium moisture content and sample thickness perhaps caused by the Crank’s equation itself.

Abstract: A rolling-horizon approach was proposed, which aims at the problem of sidings allocation for automated container yard stacking system designed and invented by ZPMC. The dynamic allocation model using objective programming was initially developed for sidings allocation. The model objective function was subject to the minimization of the total job waiting time. Furthermore A* search algorithm was employed for solving the model, which can return optimal solutions. Finally an actual case was firstly studied to illustrate the proposed approach for sidings allocation strategy, and then verified the validity and usefulness of this model and algorithm.

Abstract: A selective reduced integration 8-node hexahedral element for coining simulation is developed in this paper. The element is free of volume locking by assumed strain method. The standard velocity gradient matrix is derived in which the shear items are ignored to avoid shear locking. Hourglass modes are successfully suppressed without user-input parameters. The element is successfully employed in the coining simulation package - COINFORM. Numerical tests and experiments of a typical coin are carried out to show the good performances of the element.

Abstract: The internal flow and level fluctuation of liquid metal exposed to linear electromagnetic stirring are mainly induced by the electromagnetic force. As a result, it is necessary to estimate the electromagnetic force amplitude generated by electromagnetic stirrers. The Maxwell's equations were simplified on some reasonable assumption so as to estimate the electromagnetic force amplitude in this study. During the electromagnetic force analysis, the characters of the electromagnetic force in liquid metal exposed to a linear electromagnetic stirrer were determined at the same time.

Abstract: Based on experimental results and theoretical analysis at different temperatures and time of unit diffusion quantity，the mixing entropy in the reaction process between iron and molten tin, is investigated within the range of 260～350°C. The mixing entropy is plotted versus the dimensional time, which showed that the difference value of it at different time was an upward trend. At different temperatures, the mixing entropy of the system increased with the temperature, tin atoms diffusing into the matrix gradually becaming greater, so as to there has been a appreciable increase in the values of mixing entropy. In addition, the mixing entropy’s increase trend becomes smoothly with the temperature increasing, and the entropy change of the system is decreasing more obvious with the temperature increasing.

Abstract: Uniaxial tension tests for galvanized steel sheets are performed. Fractured surfaces of the specimens are observed by means of the scanning electron microscope (SEM). It is confirmed that the specimens experience ductile fracture. Based on the Gurson meso-damage theory, Hill’48-GTN anisotropic damage model is presented, and used to analyze the uniaxial tension test. The true stress-strain curves are fitted by three kinds of main flow stress models. After comparing the fitting precisions, the Voce model is selected as the flow stress model for the simulation analysis. The simulation results show that the Hill’48-GTN model can be used to accurately predict the whole process of damage occurrence, evolution and fracture in tension, and void volume fraction can be taken as a forming limit parameter of sheet metal forming.

Abstract: To evaluate the profile error of manufacture mainly caused by geometric error of machine tool, this paper proposes a geometric error identification and profile error simulation method. The identify method measures each axis of machine tool based on laser tracker, then using the least square method to fit the axis, as a result the coordinate system of each axis can be built. The geometric error of machine tool can be gained by analysis of the coordinate system. Building the kinematics model of large-scale multi-axis NC machine tool considered the geometric error, then using MATLAB and UG second development to achieve simulation of profile error.

Abstract: This paper reported the study of the photocatalytic activity of immobilized Fe³⁺ doped TiO₂ on glass fibre yarn. A dip-coating technique fixing catalyst onto the support surface was applied to get the TiO₂/Fe³⁺ coated filler. A photo reactor consists of a cylindrical quartz tube and filler with the immobilized catalyst was applied in the study. The photocatalytic activity was determined by the degradation of phenol in water (10 mg L^-1). Results suggested that the fibre glass coated TiO₂/Fe³⁺ photocatalysis filler has very excellent performances in repeat using and the supported TiO₂ was very stable in photocatalysis reaction.

Abstract: In order to improve the crack resistance of pumping concrete, effect of shrinkage reducing admixture on the performance of pumping concrete was stuied, the results showed that dry shrinkage decreased obviously when shrinkage reducing admixture was added into pump concrete , and 28d shrinkage can be reduced by over 40% when the dosage of shrinkage reducing admixture was 1.5% , while the shrinkage reducing admixture can significantly improve the fresh pumping concrete workability, improve compressive strength of 28d, but the flexura strength decreases slightly.

Abstract: Based on an optimal formula in previous study, the geopolymer composites reinforced by fibers, including carbon fibers, polyacrylonitrile (PAN) fibers and cellulose fibers were prepared to investigate the effects of fiber content on their compressive strength. Results show that fibers can improve the compressive strength of fiber-geopolymers in general and the optimal addition proportion of each fiber is 0.2 % - 0.3 %. Microstructures on the polished surfaces of fiber-geopolymers were observed by scanning electron microscopy (SEM), and the reinforcement of fiber-geopolymer is contributed to the moisture content and surface characteristics of fibers.