Advanced Materials Research Vols. 146-147

Abstract: The micropolar elasticity theory takes into consideration the granular character of the medium, describes deformations by a microrotation and a microdisplacement. A model can be applied to the coupled theory as well as to five generalizations, such as L-S theory, G-L theory, H-I theory, G-N theory of type (II) and C-T theory. And if some parameters in this model are taken as given values, we can easily deduce the known models of Kelvin-Voigt model and other generalized micropolar/magneto/thermo/viscoelastic theory model. Employing the model of micropolar generalized magneto-thermo-elasticity, reflection and refraction of longitudinal displacement wave at interface of two welded micropolar elastic media are studied. The amplitude ratios of reflected and refracted micropolar magneto-thermoelastic longitudinal displacement waves, longitudinal microrotational waves and the coupled transverse and microrotational waves are studied for incident longitudinal displacement wave. The numerical results show that the effects of thermal relaxation times are very significant on the amplitude ratios.

Abstract: Damping of foamed Al composite filled epoxy resin in the holes is researched by experimental and theoretical analysis. The results are showed that foamed Al damping can be improved by Filling epoxy resin in the holes, and with porosity increasing or diameter decreasing, the composite’s Damping is increased, but the change of damping with frequency is non- monotone function. The results can provide reference for optimization and application of the composite.

Abstract: Elongational rheology of LLDPE was studied by melt spinning technique. It was observed that the melt strength of LLDPE decreased with the rise of temperature, and the melts with lower elongational viscosities often broke at higher draw ratio. The melt strength activation energy was calculated by the slope of Arrhennius plots. The curves of elongational stress and viscosity under different conditions were drawn and compared, the results showed that with the increase of strain rate, the elongational stress rose and the viscosity decreased, both stress and viscosity dropped with the rise of temperature, and higher extrusion velocity caused lower elongational stress and viscosity.

Abstract: To improve the corrosion resistance and wear resistance of AZ31B magnesium alloy, in this dissertation, we use the method making AZ31B magnesium alloy as the matrix to make coating on the way of electroless plating nickel-phosphor directly. In this study, we make experiments on the influence of concentration of complexing agent in electroplating to electroless plating on the surface of magnesium alloy. We utilize the scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and the detection of corrosion resistance etc. To analyze the morphology, composition and corrosion resistance of coating. We come to a conclusion that the reaction is at the soonest when we adopt sodium citrate as buffering agent and its density is10ml/L., meanwhile, the coating particle is tiny and is well-knit with matrix. What’s more, phosphorus contents are maximum and the corrosion resistance is greatest.

Abstract: Rotating fluids experiments were carried out by CAP2000+ cone viscometer, to examine the drag reduction properties of dimples arranged in quasicrystal structure. The dimples were fabricated on the surface of duralunmin (LY12) plates. Compared with the periodic arrays, the dimples arranged in quasicrystal structure, especially the 12-fold quasicrystal structure, could significantly reduce the wall shear stress. And the relative drag reduction efficiency changes periodically with the depth of dimple. Flow-visualization experiment verified that the coherent effect of dimples arranged in quasicrystal structure and the fluids could efficiently inhibit the extending intensity of radial secondary flow, which strengthens the drag reduction effect.

Abstract: In this paper, the author successfully fabricated Mg-Sr and Mg-Sr-Y alloys by melting-leaching reduction method using SF6 and N2 as protected gas. The micro-structures of the alloys were investigated in details，and the results showed that dendrite α-Mg and eutectic α-Mg and Mg17Sr2 were the main phases in the Mg-Sr alloy, while Mg -Sr-Y alloys were composed of dendrite α-Mg and small eutectic α-Mg and Mg17Sr2 and tiny Mg24Y5. More eutectics were distributed around dendrite crystals in the Mg-Sr alloy, the Mg17Sr2 with aspect ratio of 6 : 1 were aligned and discontinuous lamellae, a Mg17Sr2 was irregular particles. The microstructures of Mg-Sr-Y alloy refined, Mg17Sr2 and tiny Mg24Y5 particles with size of 2-3μm distributed in the α-Mg dendrites and boundaries. The fomation and growth of both Mg24Y5 and Mg17Sr2 in the alloys were stated. It is obvious that the role of improving the heat-resistant Mg alloy of Mg24Y5 is more than Mg17Sr2.

Abstract: In order to study the effect of pre-deforming on the wearability of austenitic high manganese steel, domestic and foreign scholars did many pre-deforming tests. While the study of rolling pre-deformation is almost blank. By taking the cold asynchronous rolling technique, simulated roll test was carried out on austenitic high manganese steel. The microstructure and the performance after rolling showed that a great deal of high density twin crystals merged , the capability of work hardening and impact abrasion resistance enhanced greatly, wear-resisting performance improved with the increase of deformation.

Abstract: This study was conducted to evaluate the groutability and interfacial bond strength of polymer modified cement grouts (PMCG) for repair and rehabilitation of concrete pavement with different polymer/cement ratio. The groutability of grouts was studied through the cone-shaped gap test and the grouted minimum gap width was determined. The interfacial bond strength, such as flexural and shear bond strength were measured. The experimental results indicate that the groutability of grouts modified by vinyl acetate/ethylene copolymer (EVA) improves obviously and the grouted minimum gap width decreases. The flexural and shear bond strength increase 32.41% and 122.92% when the polymer/cement ratio is 10%, at the ages of 28 days respectively. The microstructure of repair interface was observed and analyzed by using scanning electron microscope, and the modification mechanism of EVA latex was discussed.

Abstract: A new technique using slope vibration casting process during heating and isothermal holding period to prepare Al-7Si-2RE alloy has been studied. The small, near-spherical and non-dendritic microstructure with the semi-solid processing requirements has been obtained. Experiments show that the cooling method, pouring process and the convection of melt caused by slope vibration had significant effects on the formation of near-spherical primary gains. The water-cooled copper mold casting with slope vibration at the temperature near liquidus can obtain Al-7Si-2RE alloy with small homogeneous equiaxed grains, the average grain diameter is 48.3μm, and the average grain roundness is 1.92.

Abstract: We present an approach that combines Computer Tomography (CT), reverse engineering (RE) and rapid prototyping (RP) for individual implant production in maxillofacial surgery. 3D acquisition of the patient’s skull is performed, after acquisition of data; an individual computer-based 3D model of the bony defect is generated. These data are transferred into RE software to create the implant using a computer-aided design (CAD) model, which is directed into the RP machine for the production of the physical model. The implant is then directly used in investment casting such as “Quick Cast” pattern to produce the titanium model. In the clinical reports presented here, reconstructions of one patient with mandible bone defects were performed using this method. The custom prostheses perfectly fit the defects during the operations, and surgery time was reduced.