Advanced Materials Research Vols. 476-478

Abstract: The effect of Y and Zn substitution on tensile properties of 6H-type ABCBCB LPSO phase in Mg₉₇Zn₁Y₂ alloy has been studied from first principles calculations. From obtained tensile stress-strain relations, at small strains anisotropy of Young’s modulus for Mg₉₅Zn is larger than that for Mg₉₅Y, whereas at lager strains anisotropy of peak tensile stress for Mg₉₅Zn is smaller than that for Mg₉₅Y. The ideal tensile strengths for both Mg₉₅Y and Mg₉₅Zn phases occur in direction, and the ideal tensile strength is increased with single Zn atom substitution. The detailed electronic structure investigations show that the hybridization between Mg and Y (or Zn) atoms is obvious, and the directional bonding between Mg and Y (or Zn) atoms would lead to large anisotropy of tensile stress-strain relations. As the strain increase, the directional bonding between Mg and Y (or Zn) atoms is weakened, the stability would be lowered, and the phases are finally fractured.

Abstract: Abstract. Aluminum high silicon alloys have concerned many researchers due to their high wear resistance, lightness, high corrosion resistance and low thermal expansion. Casting of high silicon Al-Si alloys (i.e. Si content greater than 17 wt.%) will generate large degrees of segregation and coarse microstructures due to the low rates of solidification. The problems associated with ingot casting of hypereutectic Al-Si alloys (i.e. segregation, coarse microstructures and porosity) may be overcome by rapid solidification processing such as spray, weld, and chill methods (e.g. melt spinning). The alloys under consideration here contain Al, Si, Zr, Cu, Mg, Fe and Ni. These alloys were produced by rapid solidification i.e. melt spinning. The aim of this paper is to characterise the hardness of material produced by rapid solidification at various stages of production. Several alloy variants were examined and relate the hardness to the microstructure. Piston A390 made by casting was examined for comparison.

Abstract: The dynamic behaviors of triangular honeycombs cores (THCs) are investigated by using the finite element (FE) simulations under the in-plane dynamic crushing loadings. With the increasing impact velocities, different deformation modes are observed and the kinetic energy of specimen increases rapidly. The in-plane dynamic plateau stress is the sum of the static plateau stress and the dynamic enhancement due to the inertia effect. The static plateau stress has been discussed in Part I. When all configuration parameters are kept constant, the dynamic enhancement stress is proportional to the square of impact velocity. For a given impact velocity, the dynamic enhancement stress is proportional to the density of THCs when the expanding angle is kept constant. The in-plane dynamic plateau stress is expressed empirically in terms of configuration parameters and impact velocity.

Abstract: There is a force peak at the beginning of each stroke during the insect flight, this force peak contributes a lot to the total aerodynamic force. To build a man made insect inspired man-made micro aero vehicle, this force need to be considered in the aero force model, and this model should as simple as possible in order to be used in feedback real-time control. Here we presented a simplified model to take the medium added mass effect of the wing into account. Simulated results show a high force peak at the beginning of each stroke and are quite similar to the measured forces on the physical wing model which were carried out by Dickinson et.al.

Abstract: For scenic area plan, a basic work is to evaluate environmental sensitivity. The evaluation result could provide reliable basis for later planning work. As a tool, GIS is speediness, accurate and objective. In this paper, we will use GIS into environmental sensitivity evaluation of Lushan-Xihai International Art Park planning, and the GIS analysis result could offer high quality information and support planning work of next stage.

Abstract: With Larch timber as the experimental subject, according to the visual grading-related rules in ASTM D245, four-point bending edge-wise in ASTM D4716-05 and axial strength in tension, the regression analysis is conducted; investigate the correlation relationship of Kus, E4s and σw. The result demonstrates that the combination of visual grading, density and four-point bending MOE, the predict of the parallel tensile strength will be more exactly whose correlation coefficient is 0.750.

Abstract: Mechanical behaviors of triangular honeycombs cores (THCs) are investigated by using the finite element (FE) simulations under the in-plane quasi-static crushing loadings. The deformation process is described in the form of response curves and deformation mode diagrams. The force-displacement curves include four deformation regimes with distinct characteristics. The quasi-static plateau stresses are calculated for the THCs with different configuration parameters. The influences of ratio of cell wall thickness to edge length and expanding angle on the quasi-static plateau stress are discussed in detail. The quasi-static plateau stress is proportional to the relative density of THCs and the expanding angle determines the scale coefficient. The empirical formula of quasi-static plateau stress in terms of ratio of cell wall thickness to edge length and expanding angle is given based on the FE simulation results.

Abstract: When crude oil contains wax and hydrate depositions, thermal management is needed to built up to prevent these deposition formation. Thermal insulation pipe is the common measure. Laying thermal insulation pipe is a complex operation due to their multi-layer structure and heavier weight. In this paper, mechanical analysis for thermal insulation pipe laid by S-lay is carried out. Large deformation theory is applied to establish S-lay model. Equivalent stiffness theory is used to solve the complicated structure. Numerical simulation is done to investigate the effect of controlling parameters to the pipe configuration. Numerical results show that the tension is the main controlling parameter during pipelay.

Abstract: A numerical analysis was performed to investigate the thermally-induced residual stress caused by the thermal expansion mismatch between Be and BeO. Models were constructed according to the real situation that the BeO particles embedded in grains or distributed at the grain boundaries, where the temperature-dependent materials properties, particle volume fraction and size and interparticle distance were taken into account. In simulation, it supposes particles inside grain no interacting with others, particles along the grain boundary being a period distribution. Be is modeled as elastic and elastic-plastic material with bilinear kinematic hardening model. BeO is modeled as isotropic and linear elastic. All simulations are performed by using ANSYS finite element code. Results show that the size, location and the volume fraction of particles influence on the residual stress (strain) to different extent during cooling process.

Abstract: Based on the Von Karman large deflection theory of shallow shell, the problem of nonlinear stability of symmetrically FGM shallow conical shells under the action of mechanical and thermal loads is investigated. The nonlinear governing equation under the united action of mechanical and thermal loads of FGM shallow conical shells whose physical parameters change with the power rate is derived and solved by the modified iteration method. The nonlinear characteristic relation of load, deflection and temperature is obtained. The extremum buckling principle is employed to determine the critical buckling load. The influences of gradient constants, geometric parameters and temperature differences on buckling are discussed as well.