Papers by Author: Huai Wen Wang

Abstract: Copper matrix was simultaneously reinforced with nano- and micro-sized Al2O3 particles via high-energy milling of the mixture of inert gas-atomized prealloyed Cu-1 wt.% Al powder and 0.6 wt.% commercial Al2O3 powder. At the maximum of microhardness (2400 MPa) the grain size reaches the smallest value as a result of the synergetic effect of nano- and micro-sized Al2O3 particles. The relatively low decrease in microhardness during HTE may be explained by grain growth which is retarded by Al2O3 nano-sized particles precipitated at the grain boundaries.

Abstract: A technique for non-contact optical measurement of in-plane displacements based on correlation analysis is presented. This approach can be used to identify the position of a marker before and after deformation of a specimen or plane test-object. Some mechanical parameters of materials and strains can be calculated using information from several markers’ displacements. The method is simpler than other optical techniques in experimental processing and can efficiently used to measure large deformations. The precision of marker identification method is analyzed. And some discussion on this method is also given.

Abstract: In order to explore the effect of fiber orientation angle on the Young’s modulus of fiber reinforcement polymer (FRP) composites, from the basic theory of elastic mechanics, a procedure which can be applied to evaluate the elastic stiffness matrix of FRP composite as an analytical function of fiber orientation angle (0-90^o), is developed in Mathematica environment. Results indicate that Young’s modulus of the composites strongly depends on the fiber orientation angles. A U-shaped dependency of the Young’s modulus of composites on the inclined angle of fiber is found, which agree well with the experimental results and numerical simulation. The shear modulus was found to have significant effect on the Young’s modulus.

Abstract: Young’s Modulus of glass fiber reinforced composites for wind energy applications are studied using numerical method. The effect of volume content of glass fiber on the Young’s modulus of composites is investigated. Results indicate the relation between them is nearly linear. In order to explore the effect of inclined angle of fiber on the Young’s modulus of composites, different finite element models with inclined glass fiber are developed via the ABAQUS Scripting Interface. Results indicate that Young’s modulus of the composites strongly depends on the inclined angle of fiber. A U-shaped dependency of the Young’s modulus of composites on the inclined angle of fiber is found, which agree with the experimental results. The results of the investigation are expected to provide some design guideline for the microstructural optimization of the glass fiber reinforced composites.

Abstract: As a universal finite element method commercial software, ABAQUS has been widely used in scientific research and engineering applications. However, convergence difficulties are familiar issues while carrying out damage and fracture analysis. Several methods, which are helpful to avoid these convergence problems, are presented in this paper. Baseline simulations about damage initiation and propagation in composites indicate that a larger value of viscous regularization causes the peak of the reaction force to be higher. A smaller viscosity parameter is better than bigger one. Other advanced techniques, include using automatic stabilization and customized general solution controls, are adoptable to improve convergence in ABAQUS/Standard analysis. The results of the paper are expected to provide guidance for the new user of ABAQUS.

Abstract: The mechanical behaviors of Nylon6 polymer film material are investigated experimentally. A technique, marker identification method, for non-contact optical measurement of in-plane displacements based on correlation analysis is employed to measure the deformation of the film specimens. Based on the uniaxial tension experimental results, the stress-strain relationship is obtained, which result in Young’s modulus and the Poisson’s ratio. In the creep experiment, the time-depending response of polymer film material is studied. The strain state is determined by measuring the deformations over time. Based on the obtained data about the material’s response, the bulk-modulus K(t) is calculated based on BOLTZMANN’s superposition principle.

Abstract: Short span compressive experiments of molded pulp specimens were carried out on the SHIMADZU material test machine, resulting in the stress-strain curves. The analytic results indicate that the material density and the loading rate are the two major factors that influence the stress-strain relationships of the molded pulp materials. With the increase of material’s density, elastic modulus and ultimate strength both increase. With the increase of loading rate, elastic modulus decreases whereas ultimate strength increases. By analyzing the test results and the existing models, an improved stress-strain model for molded pulp material, with the two factors taken into consideration, has been proposed. The model coefficients are obtained by fitting against the short span compressive experimental data for the materials with different densities under different loading rate. Comparison made between the experimental results and calculated results indicates that the proposed model can well fit the stress-strain curves of molded pulp.

Abstract: Damage initiation and propagation in unidirectional glass fibre reinforced epoxy matrix composites under tension load were simulated in this study. Cell models with either single fibre or multiple fibres were modelled by extended finite element method (XFEM). The damage progress in the cells was investigated and then the nominal stress-strain curves as well as stress distributions in the fibre and matrix were obtained. Results presented here indicate that the extended finite element method is an effective modelling technique to study the initiation and propagation of a crack along an arbitrary, mesh-independent, solution-dependent path.

Abstract: In this paper, the size effect of thickness on fracture toughness in the fracture behavior of a kind of copper foils was studied experimentally and analytically. Copper foil specimens with thicknesses ranging from 0.02mm to 1mm were adopted. The fracture toughness defined as the value of the critical J integral at cracking initiation was shown to depend on foils’ thickness within a certain range of thickness. For elucidating the relationship between fracture toughness and thickness, microscopic experimental analysis was carried out. Metalloscope results also showed that microscopic structure of different specimens with different thicknesses is also a factor affecting the fracture toughness. In order to explore the effect of pure thickness on fracture, specimens with the same microscopic structure were also investigated.