Advanced Materials Research Vols. 123-125

Abstract: A flash butt welding model of a high manganese steel crossing was established using the thermal coupled finite element method (FEM). The model considers comprehensively the physical parameters of materials, which change with temperature, as well as the burning material caused by the splutter during welding process. The temperature field of the flash butt welding joint and the cooling curves of the high manganese steel crossing at various locations near the welding seam were simulated. Comparisons with actual welding specimens of high manganese steel crossing indicated that flash butt welding model of the high manganese steel crossing is reasonable, and the temperature field distribution near the welding seam after flash butt welding can thus be appropriately evaluated by the simulation results.

Abstract: In this study, optimal design of the aluminum electrical railcar under uncertainty of material property is performed. The main structure of the aluminum electrical railcar is composed of aluminum extruded panel. The yield strength and thickness of the aluminum extruded panel are treated as random variables. The loading conditions are based on the standard specification. Stress and resonant frequency are the design constraints and obtained through finite element analysis. The results of reliability-based design optimization considering the uncertainty of material property are compared to those of deterministic optimization.

Abstract: The aim of the present study is evaluation of the element-free Galerkin method (EFGM) in progressive damage analyses of composite laminates. For this purpose, an orthotropic EFGM formulation is employed which is based on the first-order shear deformation theory (FSDT). In progressive damage analysis, the Hashin’s type failure criteria and their degradation rules are used. The obtained damage results from EFGM are compared with the experimental and FEM results.

Abstract: The progress of solid-state phase transformation can be subdivided into three overlapping mechanisms: nucleation, growth, and impingement. On the basis of an analytical phase transformation model, the maximum in the transformation rate of an isothermal solid-state transformation has been evaluated. Then, the mode of nucleation, growth and impingement, and the separate activation energies for nucleation and growth can be determined. Finally, application in the crystallization kinetics of amorphous alloy was described.

Abstract: Thermo-mechanical analysis for W/Cu-alloy joints with different interlayer thickness of OFHC-Cu was carried out by FEM calculation. The result indicated that the compliant OFHC-Cu can significantly reduce the magnitude and concentration of stress and plastic strain, but a weak influence on the temperature distribution. A comparison was made on the residual stress and plastic strain between the fabrication and operation conditions. It was found that the optimum thickness of OFHC-Cu is 1.0 mm in current analysis conditions.

Abstract: In the present work two higher order computational models with 9 and 12 DOF already available in the literature for which analytical formulations and solutions for the stress analysis not yet reported are considered. In addition to these models, few higher order models and the first order model developed by other investigators are also considered for the evaluation. A simply supported plate subjected to sinusoidal transverse load with SS-2 boundary conditions is considered for the analysis. Solutions are obtained using Navier's technique. Transverse stresses are computed by post processing technique and the accuracy of models in predicting the stresses is evaluated.

Abstract: A viscoelastic model is developed to describe the mechanical response of fiber-reinforced elastomeric composites at large deformation. A continuum approach is used to model the macroscopic mechanical behavior of elastomeric materials reinforced with unidirectional fibers, in which the resin and fibers are regarded as a single homogenized anisotropic material. The anisotropic viscoelastic constitutive model is developed considering transient reversible network theory. An efficient computational algorithm based on micromechanical modeling is proposed to relate the material parameters of constitutive model to the mechanical properties of composite constituents at finite strain. The microstructure is identified by a representative volume element (RVE) and it is subjected to large deformation with considering the conformity of opposite boundaries. The material parameters of the viscoelastic constitutive law are determined based on the response of heterogeneous microstructure which is examined under different loading conditions.

Abstract: Two-dimensional ZnO nanostructures with various morphologies were synthesized on aluminum by solution method at 90°C. In our experiment, 0.1M zinc chloride (ZnCl2) was used as a ZnO precursor, and different volume of ammonia solution (25％) was added to the solution. We characterize the morphology and nanostructure of 2-D ZnO nanostructures and study the growth mechanisms of these 2-D structures. It should be noted that the existence of Cl﹣ plays an important role on the formation of 2-D structures.

Abstract: Well-dispersed fluorite Er2Zr2O7 nanocrystals have been successfully prepared by a convenient salt-assistant combustion method. The effects of calcinations temperature and salt category on the characteristics of the products were investigated by XRD and TEM. The thermal treatment temperature has an important effect on crystal size and lattice distortion of the nanocrystals. The experiment showed that the introduction of salt in the combustion synthesis process resulted in the formation of well-dispersed Er2Zr2O7 nanocrystals. The average size was 30 nm and was in agreement with the XRD result, which indicated that the nanocrystals were uniform in particle size distribution. Moreover, the possible formation process in the salt-assisted combustion synthesis was also analyzed.