Advanced Materials Research Vols. 476-478

Abstract: The ideal strengths of several hcp metals (Be, Mg, Ti, Zn, Y, Zr and Ru) have been investigated by first-principles stress–strain calculations. The results reveal that the ideal shear strengths of these hcp metals occur mainly on basal plane or prismatic plane. Particularly, for basal plane the peak shear stress in direction is smaller than that in direction. The calculated tensile strengths and elongations in direction are broadly consistent with the available theoretical results. Furthermore, both the ideal shear and tension strengths become stronger with the decreasing of c/a for these simple metals or transition metals. The calculated electronic structure further reveals the inherent mechanism of hcp metals.

Abstract: Pore defect is a kind of typical non-continuous casting defect. It always brings local stress concentration and fatigue crack. The distribution charactersic of pores has greatly influence on the fatigue life. In this study, distribution characterstic of pore has described by pore to surface distance (S) and pore dispersion coefficient (r). By numerical simulation method, stress and fatigue life distribution law in the test bar have been studied under different and . Under the same load condition and pore volume fraction, the stress concentration factor (Kt) will increase and fatigue life will decrease following pore to surface distance (S) decreasing and dispersion degree (r) increasing within a limitation. The influence of pore to surface distance (S) is more obvious than the pore dispersion coefficient (r) on fatigue life of the casting.

Abstract: This study continued the investigation into the mechanical properties of high strength concrete filled steel tubular columns, (HSCFST). The test results for slender columns show that the load bearing capacities and maximum displacement ratio (the ratio of displacement to the initial length at peak load) of the column decreases as slenderness ratio, determined as the ratio of the length to diameter, increases. The test results for eccentrically loaded columns show that when the slenderness ratio is kept constant, the load bearing capacity and maximum strain decrease as the eccentricity ratio increases, with the eccentricity ratio defined as the ratio as the ratio of eccentricity to radius. The formula for calculating the load bearing capacities of slender columns and the eccentrically loaded columns are presented in the paper. These formulas are designed for inclusion in design code documents.

Abstract: Failure process of laminated composites with the hole under in-plane compressive loading is performed by progressive failure analysis method. A modified form of Hashin’s failure criterion by Shokrieh is used to investigate the failure, where a sudden degradation model is proposed to reduce engineering material constants. The numerical study of laminated composites is implemented in ANSYS Parametric Design Language (APDL). The initiation and propagation of local damage and response of laminated composite structures from initial loading and ultimate failure are predicted. The model has been validated by comparing numerical results with existing experimental results. And then failure analysis of specimen fabricated from M40J/Ag80 on influence of the hole under compressive loading has been performed by the proposed model.

Abstract: In this paper, Representative Volume Element with random distribution pattern has been built and applied to study and analyze the macro mechanical properties of the carbon black filled rubber composites by the micromechanical finite element method. And numerical simulations under uniaxial compression have been made by two-dimensional plane stress model. The periodic boundary conditions are imposed on each Representative Volume Element in order to ensure the compatibility of the deformation field. The dependence of the macroscopic stress-strain behavior and the effective elastic modulus of the composites, on particle distribution pattern, particle volume fraction and particle stiffness has been investigated and discussed. It is shown that the stiffness of the composite is increased considerably with the introduction of carbon black filler particles, and the effective elastic modulus of the composite is increased with the increase of the particle volume fraction.

Abstract: A in-plane stress constraint factor C_i and a out-of-plane stress constraint factor C_o are introduced to study the three-dimensional stress state and the elastic-plastic constraint effect of the crack tip. The deep crack specimens(a/W=0.5) and the shallow crack specimens(a/W=0.1) with different thicknesses are performed in the present study. By using the finite element analysis, the result shows that the thickness effect of the deep crack specimens is more obvious than that of the shallow crack specimens. For the deep crack specimens, the crack constraint enhances with the specimen thickness increase. When the specimen thickness is equal to the specimen width, the constraint levels in the middle 2/3 thickness of the specimen approach to those from the plane strain analyse. For the shallow crack specimens, the crack constraint is almost fixedness when the specimen thickness changes from three times of a crack length to a specimen ligament length. Namely, increased thickness is helpless to enhance the crack constraint effect. Therefore, a shallow crack specimen may be designed by the lesser thickness than the standard deep crack specimen.

Abstract: Creep rupture data plays vital role in life prediction and safety assessment of high temperature components. In order to describe the scattering of the data, a statistical analysis of creep rupture data for 4Cr25Ni35 steel was performed by Z-parameter method. With the application of Z-parameter, reliability design for allowable stress of creep rupture strength was carried out according to design life. It is found that Manson-Haferd method appears better correlation results with experimental data. Statistical analysis shows that the scattering of Z-parameter for 4Cr25Ni35 steel is supported by normal distribution. Compared with safety factor method, the method based on Z-parameter can perform reliability design for allowable stress of creep rupture strength by considering the dispersibility of the rupture data. Reliability design based on Z-parameter is more agree with experimental data.

Abstract: The paper studies strain localization and stability of material by simple harmonic motion by using rate dependent and gradient-dependent models. The laws of Internal Length Scales and stability of material are obtained at two-dimensionals condition for two mixture models. The conditions of wavelengh’s lower limit and stability of material are confirmed. Thus, a formula of strain localization band width about material at the condition of one and two dimensions is obtained.

Abstract: Fractures in Solid system fuel structure pose a huge risk to structural integrity of the system. Ansys APDL scripting language has been used to analyze fractures with different geometry, material and loading. Parameterization of simulations resulted in developing a tool for solid fuel system designers to perform a quick fracture analysis during their design iterations. Numerical simulation results have been compared with the experimental data and a good agreement between the two has been found, ascertaining our numerical approach for the assessment of the problem. Crack length-Temperature superimposition has been performed to obtain master curves for the data, which can be used to predict stress intensity factor at different crack lengths.

Abstract: In the light of growing global competition, organizations around the world today are constantly under pressure to produce high-quality products at an economical price. The integration of design and manufacturing activities into one common engineering effort has been recognized as a key strategy for survival and growth. Design for manufacturability (DFM) requires product designers to simultaneously consider the manufacturing issues of a product along with the geometrical and design aspects. In this paper, part manufacturability was analyzed in detail. An evaluation system of DFM was proposed. Product design can be guided according to feedback information by evaluating the part manufacturability.