Advanced Materials Research Vols. 97-101

Abstract: Based on the nonlinear finite element analysis method, FEA models which describe the viscoelastic friction contact state of the polyurethane foam preloaded structures are created. In the simulations, the general Maxwell viscoelastic constitutive relation is introduced and a seven-parameter general Maxwell viscoelastic model is used to fit the experimental stress relaxation curve of polyurethane foam. During the nonlinear contact analysis, coulomb friction law is adopted, and the effects of the coulomb friction coefficient on the reaction force in the axial direction are analyzed. The FE results show that the change tendencies of relation curves of the structures are similar to which of the polyurethane foams. In the end, the influences of stiffness ratio of polyurethane foam to the outer component on the structural relaxed force are discussed, and the FE results indicate that the stiffness ratios affect the stress (force) relaxation degree remarkably. That is to say a good structure design could optimize the mechanical performance of the complicated structures greatly.

Abstract: Magnetorheological (MR) fluids are materials that respond to an applied magnetic field with the change of their yield and rheological behaviors. In this paper, the yield and rheological behaviors of MR fluids are discussed. Based on the microstructure of magnetic chain a theoretical model is developed to analyze the effect of an applied magnetic field on the yield stress of MR fluids. Bingham model is used to describe the rheological behaviors of MR fluids subject to an applied magnetic field. The results show that altering the strength of an applied field can control the yield stress of MR fluids. The shear stress increases as the strength of an applied magnetic field increases, and it hardly changes with the increase of shear strain rate. MR fluids exhibit Bingham plastic model.

Abstract: Fused quartz ceramic was prepared in reducing atmosphere at 1300°C, 1400°C and 1500°C for 1h with fused quartz powder as raw materials (size<0.2mm). The effect of La2O3, Nd2O3, Er2O3 and Yb2O3 on crystallization and sintering of the materials were researched by measurements of apparent porosity, bending strength and thermal expansion rate (RT~1200°C), and analyses of XRD and SEM. The results showed that La2O3 and Nd2O3 have a few facilitating effect on sintering, Er2O3 and Yb2O3 have better facilitating effect on sintering of fused quartz ceramic samples, samples ER and YB have lower apparent porosity and higher bending strength and more compact microstructure. So additives La2O3, Nd2O3 and Er2O3 have a few effect of inhibiting on crystallization, Yb2O3 has better effect of inhibiting on crystallization of fused quartz. Sample YB has least thermal expansion rate.

Abstract: Usually model parameters from uniaxial experiments are not suitable for dielectric elastomer under biaxial loading condition. To characterize the mechanical behavior of dielectric elastomer, a biaxial tensile bench is established, on which uniaxial tests can be performed too. On the basis of the analysis of viscous effect of elastomer, experimental condition for data acquirement is determined. Then equi-biaxial and uniaxial experimental data are obtained to fit three constitutive models, i.e. Mooney-Rivlin, Yeoh and Ogden model. Also, least square minimization method is used to obtained model parameters, which are applicable to both uniaxial and equi-biaxial experimental data.

Abstract: The isothermal transformation of pearlite in an Fe-0.27%C-3.15%Mo (weight percent) alloy applying large compressive deformation was investigated by means of thermal simulation, optical and scanning electron microscopy. The pearlite transformation was promoted by large compressive deforming on austenite, which is attributed to the effect of large compressive deformation on nucleation of pearlite transformation.

Abstract: SiC powders doped with aluminum in the method of thermal diffusion were prepared at 1800°C, 1900°C, and 2000°C respectively, and the permittivity and structure of SiC powders before and after thermal diffusion were investigated. There is no obvious change in the morphology and phase structure before and after the doping processes. Both the real and the imaginary parts of the permittivities of the Al-doped SiC powders are improved much more than those of the original SiC powders, and increase with the doping temperatures. It is believed that, the high values of both the real and the imaginary parts of the permittivity are due to electric relaxation and conductivity losses as result of aluminum atoms doped in silicon carbide lattice.

Abstract: In this paper, the texture and micro-orientation of FSS (Ferritic Stainless Steel) during hot rolling, cold rolling and annealing were studied by using x-rays and EBSD technology. The results shown that as cast ingot of FSS was compose of random orientations equiaxed grains and <001>∥ND columnar grains; after hot rolling, the preferred orientation of <001>∥ND columnar grains of as cast ingot obtained inherits, the fiber texture was obvious stronger than that of equiaxed grains; during cold rolling, the initial <001>∥ND columnar grains turn to  fiber texture,  fiber texture can not be found.

Abstract: Early-age deterioration of concrete due to cracking and higher maintenance cost for poor durability cause serious troubles to concrete structures. Steel slag is a solid waste discharged in large quantities by the iron and steel industry. Steel slag includes a certain scale mineral such as C2S and C3S, and can be applied in cement and concrete as mineral admixtures. When mineral admixtures with steel slag powder and blast-furnace slag powder are mixed into concrete, the performance of concrete can be improved further. Mineral admixtures with steel slag powder as partial replacement for Portland cement in mortar is an effective means for enhancing abrasion resistance. Steel slag powder can be used to reduce cracking in concrete at early age, so that it will improve the durability of concrete structures.

Abstract: Firstly, according to the theory of dual variable, a procedure of the calculating fracture probability of the pressure vessel is presented. Secondly, according to the results of calculating the random numbers of the parameters in the fracture probability model, the dual variable method for the fracture probability of pressure vessel is proved to be a good technical to reduce variance. Finally, the results between the simple sampling and the dual variable method showed that dual variable method is very simple and can be widely used in engineering.

Abstract: In reliability design and maintenance plan, determining statistical distribution type of interrelated structure is a very important job, and it is always determined through reliability test, which are time-consuming and needs a large number of tests. In this paper, a method determining statistical distribution function was proposed through the experimental data of the Creep Behavior. This method uses the test data; the results of Larson-Miller Method obtained from the data from experiments, and use the least-squares linear regression to get the parameter of common probability distribution function, such as Weibull Distribution, Lognormal Distribution and Normal Distribution. Statistical function of structural failure data was derived through discussion and comparison of results from various methods. The examples proved the validity and usability of this method.