Advanced Materials Research Vols. 160-162

Abstract: Characteristics of in flight particle and splat fabricated by arc spraying of three different types of cored-wire including WC-Cr-Ni, WC-Cr-Fe and W-Cr-Fe nano-composite were revealed. In-flight particles and splats were deeply characterized in order to correlate their characteristics that forming coating and affecting coating structure and properties. Starting cored-wires were also characterized prior to being sprayed. Particle size, morphology microstructure, chemical composition and phase identification were investigated through various techniques. The results showed that the size of the in-flight particle did not depend mainly on the size of filler particles as expected, but was instead strongly related to the whole content of metallic phase composed the cored-wire, as the more metal composition the larger size of the in-flight obtained. Splat shapes and characteristics were also found to depend on the metal content; a flower shape splat with a high degree of splashing was predominant for cored-wire having more metal composition. The W-Cr-Fe nano-composite cored wire had the highest content of metallic binder phase, which resulted in the largest in-flight particles produced, and well melted of the metallic phase led to the highest degree of splashing observed.

Abstract: In foregoing study, a new phenomenon of the local dent of upper face sheet occurs in the simulation of dynamic response of sandwich plate subjected to blast loading. The reason and the effect of local dent on energy absorption are not ascertained. In this paper, two kind of square honeycomb plate with the cell wall thickness of 1mm and 0.5mm and with the same mass are modeled. And the dynamic response of both plates subjected to blast loading is simulated using LS-DYNA. For the thicker cell wall (1mm), the local dent is obvious while for the thinner cell wall (0.5mm), the local dent is not obvious and can be ignored. In addition, curves of the ratio of the maximum deflection of lower face sheet of sandwich plate to monolithic solid plate vs the mass of TNT charge as well as the ratio of internal energy are obtained. The results indicate that the local dent has the contribution to the energy absorption of sandwich plate especially in early time and the sandwich plate with the core of thinner cell wall has more effective capacity in blast-resistance than that with the core of thicker cell wall.

Abstract: Parameter optimization in multi-pass cutting operations involves optimal selection of cutting speed, feed rate, depth of cut, and the number of passes, duo to significant influence of these parameters on the quality of machined parts and machining economics. In this paper, a non-linear mathematical model based on minimum production cost for multi-pass milling operations is presented. The unwanted material is removed by one finishing pass and one or multiple roughing passes depending on the total depth of cut. Various realistic constraints are considered when developing the model. Optimal values of machining parameters are found by Genetic Algorithms. An example is presented to illustrate the optimization model and solution approach. The method yields lower unit production costs compared with the results from the literature and machining data handbook.

Abstract: Based on changing the braid angle and geometrical sizes, the compressive experiment of 3D braided four-directional Carbon/Epoxy braided composites is researched. It is found that failure of the braided composites exhibits compressive and shear failure mode. The failure crack propagates mainly in one or two 45º shear direction. Epoxy matrix among braid yarns of the braided composites is squeezed out to form epoxy band. The stress-strain relations of the braided composites with 45º and 30º braid angles all appear nonlinear apparently. Meanwhile the correlation of failure modes and constitutive relation with geometrical sizes of the braided composites is obtained. The compressive stress-strain relations of the braided composites are not great affected by the geometrical sizes. The compressive strengths with great discrete behaviors do not have obvious rules with height of the braided composites.

Abstract: To predict and control feed batch fermentations of Corynebacterium glutamicun TQ2226 which can produce L-histidine , in this paper , we use a recurrent neural network model(RNNM).The control variables are the limiting substrate and the feeding conditions. The multi-input and multi-output RNNM proposed has seven outputs, nineteen neurons, twelve inputs, in the hidden layer, and global and local feedbacks. The weight update learning algorithm designed is a version of the well known backpropagation through time algorithm directed to the RNNM learning. The RNNM generalization was carried out reproducing a C. glutamicum fermentation not included in the learning process. It attains an error approximation of 1.8%.

Abstract: This paper describes the method of Fiber Bragg Grating(FBG)embedded in the three-dimensional(3D) braded composite materials and provides the method of health monitor for 3D braided composite materials condition. The paper analyses the relations of FBG change and the inner straining under the stretching on materials. It is provided that the way of signal collection and processing. In the process of load-supporting, the internal local strain of 3D braided composites is much more, and local strain has certain interference on embedded near FBG output. The experimental results proved that FBG sensors have exceptional sense characteristic. The braided angle of composites has a little influence on FBG signal. FBG embedded in the 3D braided composite materials has not more effect mechanical property of materials. This research provides basis for the study and application of advanced intelligent composites.

Abstract: the oxidation resistance of glass-based coating on molybdenum substrate was studied in the paper. The Mo substrates with glass based coating modified by the different concentration of ZrO2 in the coating were prepared and characterized; results showed the oxidation resistance of samples increased firstly and decreased subsequently with increase in ZrO2 concentrations. The influence of different heat treatment temperature was also discussed in the paper. After the sampes were pretreated at the high temperature for 20 minutes, the oxidation resistance properties were improved five times than un-pretreated ones. SEM showed the glass powders in the coating changed into viscous liquid which adhere to the substrate tightly after the samples had been pretreated. Resulting showed the sample exhibited the best oxidation resistance when pretreated at 1300°C.

Abstract: Al-(4-5)%Cu alloy was served as experiment material，the effect of pulsed currents on the solidification structure was investigated. During the solidification process of Al-Cu alloys, pulsed currents was added into the melted alloy in the crucible .The change of temperature curve and microstructure about the alloy was investigated in such conditions by temperature-recording instrument and optical microscope.The results showed that pulsed currents can shorten the temperature region of crystallization and refine the grains of the alloy,which crush the dendrite and make the solidification structure non-dendrite, presenting columnar and equiaxed grains which are distributed evenly and whose space between crystals are reduced. This investigation firstly started to study the relations between the temperature region of crystallization and organization structure of solidification. Finally, the mechanism of metal solidification affected by square wave pulsed currents was discussed.

Abstract: Mullite–zirconia composites were synthesized through reaction sintering Algerian kaolin, α-Al2O3, and ZrO2. Phases present and their transformations were characterized using x-ray diffraction. Quantitative phase analysis was performed following the Rietveld method. Hardness and fracture toughness were measured by Vickers indentation. The flexural strength was measured using a Universal Testing Machine. It was found that the microstructure of samples sintered for 2 hours at 1600°C was composed of mullite grains which have whiskers’ shape and ZrO2 particles. In the composite containing 16 wt.% ZrO2, the ratio of tetragonal zirconia transformed to monoclinic zirconia was relatively small and did not exceed 18%. However, in the composite containing 32 wt.% ZrO2 around 75% of the tetragonal structure changed to monoclinic structure. Also, it was found that the increase of ZrO2 content from 0 to 32 wt.% decreased the microhardness of the composites from 14 to 10.8 GPa. However, the increase of ZrO2 content from 0 to 24wt.% increased the flexural strength of the composites from 142 to 390 MPa then decreased it with further increase of ZrO2 content. The fracture toughness increased from 1.8 to 2.9 MPa.m1/2 with the increase of ZrO2 content from 0 to 32 wt.%; and the rate of the increase decreased at higher fractions of ZrO2 content. The average linear coefficient of thermal expansion (within the range 50 to 1450°C) for samples containing 0 and 16 wt.% ZrO2 sintered at 1600°C for 2 hours was 4.7 x10-6 K-1 and 5.2 x 10-6 K-1 respectively.

Abstract: By analyzing fluid dynamics of blood in an artificial blood pump and simulating the flow field structure and the flow performance of blood, the blood flow and the damages in the designed blood pump would be better understood. This paper describes computational fluid dynamic (CFD) used in predicting numerically the hemolysis of blade in micro-axial blood pumps. A numerical hydrodynamical model, based on the Navier-Stokes equation, was used to obtain the flow in a micro-axial blood pump. A time-dependent stress acting on blood particle is solved in this paper to explore the blood flow and damages in the micro-axial blood pump. An initial attempt is also made to predict the blood damage from these simulations.