Applied Mechanics and Materials Vols. 198-199

Abstract: In this study, layer structured porous chitosan scaffold was successfully fabricated using thermal induced phase separation method. The scaffold had a layer structure with interconnective pores (50- 300 μm) and high porosity (>90%) using citric or acetic acid as the solvent. However, the results of compressive modulus of the scaffold showed that acetic acid was a better choice, and the compressive modulus of scaffold increased with chitosan concentration in acetic acid. The scaffold is very promising for tissue engineering.

Abstract: In recent years, finite element analysis technology has been applied in Aircraft sheet metal manufacturing and digital manufacture field. It has become an effective way to solute Aircraft sheet metal precise manufacturing and received extensive attention. Chengdu Aircraft Company used finite element analysis in Rubber bladder forming for the development of aircraft. Parts rough lumber, forming way, tooling structure, forming pressure and springback compensation has been pre-determined. Finite element analysis of Rubber bladder forming shortened the process preparation cycle, and improved the part forming quality and the ability of the development and production.

Abstract: On the basis of analyzing the topological structure of an original mechanism, it leads to the generalized kinematic chain meeting the same topological structure characteristics of the original mechanism in accordance with the generalized principle of mechanism, number synthesis of kinematic chain and compound hings. Allocation of ground links and performing links in the kinematic chain can get all feasible specialized kinematic chains while considering practical design constraints. In the final step, concrete schematic diagram of mechanism being restored from specialized kinematic chains leads to a series of new mechanism different from the original one. Designers ascertain appropriate new mechanism after selection and analysis.

Abstract: Based on dimensional analysis, finite element numerical calculation is undertaken on elastic–plastic solids to investigate the relationship between instrumented indentation nominal hardness H_n and reduced elastic modulus E_r for three different apex angle indenters. The half-included angles of axisymetric conical indenter models are 62.9°, 70.3°and 85.566° which are corresponding to the real indenters of cube corner indenter with 60° face angle, Berkovich indenter with 65.27° face angle and cube corner indenter with 85° face angle, respectively. The relationship between a nominal hardness/reduced elastic modulus (H_n/E_r) and elastic work/total indentation work (W_e/W_t) is established with a sixth-order polynomial form for each apex angle indenter. For rigid indenter of instrumented indentation model, reduced elastic modulus E_r=1/[(1+v²)/E], where E and v are elastic modulus and Poisson’s ratio of the indented material. Therefore, H_n/E_r–W_e/W_t relationship can be used to give estimates of E. Accuracy estimation for the each relationship of each half-included angle indenter shows that the large half-included angle of 85.566° gives better E_r measurement error of +11.56% for a low yield strength material(e.g., materials for which σ_y=100MPa, n=0 and E=200GPa), while for the smaller half-included angle of 62.9° or 70.3° indenter, the measurement error is > ±12.74%. The research in this paper confirms that H_n/E_r–W_e/W_t relationship of large apex angle indenter such as 85.566° half-included angle is recommended to be used for estimating the elastic modulus E of indented material.

Abstract: Mechanical damage and aging are the main mechanisms of nonlinear characteristics of solid propellant.A comprehensive big strain visco-elastic constitutive model with damage mechanics and aging was established, by using the visco-elastic constitutive equations form expressed by the generalized variable, introducing damage variables, and taking the relaxation modules after aging to characterize the aging. The correctness of the model was verified through experiments. the parameters need by modeling are easy to be got, and converted into the finite element code to do the simulation computation, then the model is suitable for the engineering application.

Abstract: By analyzing the processing principle of honeycomb ring with electrical discharge grinding (EDG), using method of orthogonal design to conduct the test and establishing mathematical model of regression equation with surface roughness through EDG. Comprehensive consideration of the various factors exist during processing process, derived out the more accurate experience formula of surface roughness on superalloy GH536 by EDG and obtained the higher significant level of regression equation by regression analysis. Results of test provide theoretical basis for the practical production in processing superalloy thin-walled parts by EDG and have a better guiding significance to solve the actual technical problems of process.

Abstract: During the flight of the hypersonic Vehicle, the angle of attack will change with the flight attitude. At the same time, the aerodynamic forces from the surface of aircraft will also be changing. The pressure and friction force are the main causes of the aerodynamic heating, so the surface aerodynamic heating will change. By used the method of numerical calculation, the passage studied the influence the change the pressure and friction force on the distribution of heat flux in different angle of attack and the relationship between the change of the force of lift-drag and aerodynamic heating. The research suggested that the distribution of the heat flux had very good consistency with that of pressure and friction. The lift change was the dominant factors influence of pneumatic thermal change; the change of drag force affected only the speed of heat flux change.

Abstract: In this paper, the axisymmetric deformation of one cylinder with transversely isotropic is researched. According to the general solution of deformation body with transversely isotropic and the Lur’e method, the exact deformation field and exact stress field are represented by unknown functions with single independent variables. Based on boundary conditions of radial direction surface loading, the unknown functions can be ascertained. By dropping terms of high order, the approximate solution is derived, and the department field and the stress field for a circular cylinder under radial direction surface loading can be obtained. After simplifying, the states with isotropic can be obtained.

Abstract: The microstructure and mechanical properties of aged Mg-5.5Al-1.2Y magnesium alloy with Ca addition are investigated. The results show that with 1.0wt.% Ca addition, the phase of Al₂Y is refined obviously and the phase of Mg₁₇Al₁₂ has a dramatic decrease in number. And, high melting point intermetallic compounds Al₂Ca and Al₄Ca are formed. Meanwhile, the β-Mg₁₇Al₁₂ phase become more dispersed. After 1.0wt.% Ca addition, the mechanical properties of the alloy at room and elevated temperature are improved.

Abstract: The contrast of remote sensing images is very low, which include various noises. In order to make full used of remote sensing image information extraction and processing, the original image should have to be enhanced. In this paper the enhancement algorithm based on the biothogonal wavelet transform is proposed. Firstly, we have to eliminate the beforehand noise, and then take advantage of the non-linear wavelet transform to enhanced low-frequency and high- frequency coefficient respectively. Finally, the new picture is reconstruct by the transformed low-frequency and high-frequency coefficient. The efficiency of the proposed algorithm was proved by the theoretical analysis and computer simulations.