Applied Mechanics and Materials Vols. 152-154

Abstract: Based on standard k-ε turbulent, PISO algorithm and the dynamic mesh model, numerical simulation of the 3D, viscous, unsteady compressible gas synthetic jet model was proposed. Two kinds of diaphragm boundary conditions， Helmholtz frequency characteristics and other factors affecting the performance of the 3D synthetic jet were discussed. Simulation results show that the dynamic mesh diaphragm boundary condition is more consistent with the experimental results and the theoretical results, which demonstrates the rationality of the dynamic mesh 3D compressible gas model.

Abstract: Abstract：Our theoretical study aims to analyze ionization and dissociation mechanism of cyclopentanone in the excited states and gives out a result with proved and directed significance for the corresponding experiments. Using the CIS（Configuration Interaction with Single Substitute） method, and 6-31+G (d, p) basis set, we calculated the frequency of excited state of cyclopentanone ion molecule. We have investigated the different vibration patterns of C-C bond and C-H bond under different excited states with imaginary frequency. Five dissociation channels have been obtained. Generally, the possible dissociation fragments in the excited state。

Abstract: The double-threshold binarization and morphological transform were applied to process the metallographical image. They could classify the grain and the grain boundary from gray metallographical image. Also, the eight-direction tracking techniques about Freeman chain encoding for metal metallographical compression had been discussed, and a grain boundary tracking algorithm was given. The experimental result shows that the proposed image processing method can segment grains and their boundaries efficiently. Freeman chain encoding can compress the stored data of metallographical image greatly. Compared with another compression method RLE, it has much higher compression effect.

Abstract: Sonic crystals are periodic structures made of sound hard scatterers which attenuate sound in a range of frequencies. For an infinite periodic structure, this range of frequencies is known as band gap, and is determined by the geometric arrangement of the scatterers. In this paper, a parametric study on rectangular sonic crystal is presented. It is found that geometric spacing between the scatterers in the direction of sound propagation affects the center frequency of the band gap. Reducing the geometric spacing between the scatterers in the direction perpendicular to the sound propagation helps in better sound attenuation. Such rectangular arrangement of scatterers gives better sound attenuation than the regular square arrangement of scatterers. The model for parametric study is also supported by some experimental results.

Abstract: The kinetic energy of lift car will be consumed by the friction between the safety gear and guide rail in emergent braking process. This will lead to remarkable temperate increase of frictional surface. Due to the explosive atmospheres in which the explosive-proof lift servers, the high temperature may result in severe explosion accident. In this paper, an finite element model is developed to analysis this progress. The transient heat flux density is derived from energy transformation progress in safety gear action, and applied as boundary condition to the finite element model. Experiments are carried out to measure the temperature increase of safety gear frictional surface, and the results show good coincidence of temperature increase tendency between experiments and simulations.

Abstract: The process of fatigue crack growth is generally random nature, due to many sources of variability, such as external loading, material properties and geometry conditions. Therefore is is important to investigate the statistical variability of fatigue crack growth in order to development the methodology for probabilistic fatigue crack growth life prediction. This paper is concerned with the randomness investigation of fatigue crack growth for the FSWed 7075-T651 aluminum alloys. In this investigation, the fatigue crack growth tests were conducted for five compact tension (CT) specimens of the FSWed 7075-T651 aluminum alloys, base metal (BM), heat affected zones (HAZ) and weld metal (WM), especially three different constant stress intensity factor range (SIFR) controls.

Abstract: According to characteristics of adjusting width by vertical roll at a certain steel corporation, unsteady deformation of head and tail of slab during edge rolling was analyzed by FEM simulation on base of a commercial software. The effect of several process conditions on the cross-section deformation and width loss of slab were also analyzed.

Abstract: In order to improve the service life of extrusion dies with long cantilever structure, a design scheme of porthole die for half-hollow profiles with long cantilever was introduced. Using numerical simulation method, compared with conventional method for the half-hollow porthole design method of a typical profile die model, the equilibrium of the material flow at the outlet, the stress and deformation of the die were analyzed in detail. With selection of the cantilever thickness shrinkage as the objective function, experiment was done to verify the result of simulating analysis. The results indicated that there was only little difference for the equilibrium of material flow between the two design schemes, but the stress load and deformation of the design scheme were greatly improved.

Abstract: 2-acetoxy-6-naphthoic acid (ANA) was synthesized in the presence of 2-hydroxy -6-naphthoic acid (HNA) and acetic anhydride (CH₃CO)₂O with toluenesulfonic acid (PTSA) as catalyst. The effects of reactant ratio, temperature, time were investigated in the acetylation process. ¹H-NMR、¹³C-NMR、FT-IR、HPLC measurements indicate the optimal acetylation reaction condition when the ratio of HNA: (CH₃CO)₂O : PTSA are 1: 2.3:0.025 under the temperature at 90~95°C for 40min.

Abstract: In this paper, a new Rockwell hardness model with volumetric parameter by least square method was suggested. Also, its result was compared and investigated with real measured hardness. The volume measurement of indented volume was performed by CLSM(confocal laser scanning microscope) and the captured HEI(height encoded image) was used as a original data for the calculation of indented volume. Using this volume as a parameter, this independent variable was used for experimental modeling of least square algorithm and it can be used for the prediction of Rockwell hardness.