Advanced Materials Research Vols. 915-916

Abstract: To determine the impact of laser parameters on the contrasts of laser direct marked Data Matrix symbols on titanium alloys, a Q-switched Nd:YAG laser was used in the marking process. For this purpose, four laser marking parameters (i.e. electric current, effective vector step, Q-switch frequency, and laser line spacing) were correlated with the symbol contrast (SC). The L25 orthogonal array based on the Taguchi experimental method was adopted to determine the optimal combination levels of laser parameters for the SC, and the experimental data were statistically analyzed by multi-factor analysis of variance (ANOVA). Experimental results showed that the electric current, effectie vector step, laser line spacing have a statistically significant impact on the contrasts of laser marked Data Matrix symbols. Q-switch frequency is statistically insignificant at a 5% level. The optimal combination levels of laser parameters for the SC is where the electric current is at 26A, the effective vector step is at 0.001mm, the laser line spacing is at 0.01mm, and Q-switch frequency is at 5kHz.

Abstract: The main disadvantage of AZ31 magnesium alloy sheets is low corrosion resistance, which can be improved by coating aluminum layer. In this paper, Al/AZ31/Al laminated composites were produced and interface diffusion behavior of Al/AZ31 by hot rolling and annealing was studied. The results show that the optimally rolling temperature is 400 oC, the thickness of the reaction layer for Mg and Al was increased with increasing annealing time at the temperature of 250 oC and 300 oC, respectively. At the mean time, the diffusion kinetic equation of Al/AZ31 interface was given.

Abstract: To identify critical laser marking parameters which have a statistically significant effect on the contrasts of laser marked Data Matrix symbols on titanium alloy substrates, a Q-switched Nd:YAG laser was used in the laser marking process. The influence of six laser marking parameters (i.e. electric current, effective vector step, delay between the effective vector step, Q-switch frequency, Q release time, and laser line spacing) on the contrasts of laser marked Data Matrix symbols were studied. Single-factor analysis of variance(ANOVA) tests with a 95% confidence level were employed to determine whether a laser parameter had a statistically significant impact on the contrasts of laser marked Data Matrix symbols. Experimental results showed that four laser marking parameters (i.e. electric current, effective vector step, Q-switch frequency, and laser line spacing) have a statistically significant effect on the contrasts of laser marked Data Matrix symbols.

Abstract: The goal of this paper is to simulate the bending process of extruded aluminum profile using ABAQUS/CAE software. Bending investigations were conducted using the finite element method. The main contents of research work include simulation software, which give in details the pre-processing steps followed to obtain an accurate model to work on. The computing time is often important, explored some ways to reduce it. The simulation give information about the location of critical areas on the profile after bending; the middle section was targeted since it is the area most deformed. This paper focus on the influence of the die mesh, initial distance, mass scaling factor and time scaling factor on the evolution of the computer time (CT), kinetic energy (KE), stress (SVMises) and strain (peeq) .

Abstract: Coupling the force flow field with the phase field model for the isothermal growth of dendrite multiple grains, Sola algorithm is used to calculate the flow speed and pressure of liquid metal, double grid numerical method was used to reduce the calculation amount of computer simulation, the space factor and time factor were introduced to improve the accuracy of double grid numerical calculation, Taking Al-2%-Cu alloy for example, the dendrite growth process of the binary alloy was simulated under forced convection environment; Simulation results can capture the real dendrite growth and interactions of the liquid metal flow in the process of dendrite growth under forced convection environment: The flow of metal liquid affects the growth morphology of dendrite multi-grain. The flow of liquid metal changes the growth speed of dendrite tip in different directions for each dendrite, the greater of the liquid metal initial flow speed, the worse of dendrite morphology symmetry; different initial flow speeds result in the different distance between each dendrite. The metal liquid forced flow causes the instability of dendrite growth interface, it changes the degree of undercooling, composition, dendrite tip growth rate and the curvature radius of dendrite tip in the dendrite growth forefront interface. For the forefront dendrite growth interface free energy system, the dendrite tip growth speed and curvature radius were adjusted by the competitive growth of dendrite tips, thus reached a new stable state for the interface, which resulted in the emergence of bifurcation in dendrite tips. The liquid metal flow speed between different grains was affected by the relative position and morphology between different grains, and also affected by the initial inflow speed of the liquid metal.

Abstract: Investment casting is one of main precision casting processes to realize near net shape castings. For the castings with thin-walled cross section or complicated shape, it is easy to generate casting stress such as thermal stress, mechanical stress and phase transformation stress, resulting in casting deformation due to the uneven cooling and hindered contraction. Once three-dimensional deformation is formed, it is very hard to correct. In this paper the finite element method (FEM) was used to analyze the stress and deformation of thin-walled lost wax casting. The results show that the temperature and stress distributions are uneven in the casting and the tendency to deform is higher even with insulating shell mold. And based on the results, the technical measures of adding supporting ribs are adopted to restrain deformation. The practice of volume production indicates that no casting was rejected due to deformation defects.

Abstract: Due to the long structure plane size of the super-long concrete structure ,considering the effect of environment temperature on the structure in design. the expansion joint is arranged to solve the problem of temperature stress and shrinkage stress in the past.This paper discusses several new solutions on the temperature problems of super-long structure,and the unbonded prestressed technology in the engineering application of super-long structure under temperature effect to solve problems to do the analysis,provides the design basis for engineering designers to consider the temperature effect.

Abstract: Magnesium salt flame retardant is a new filler flame retardant agent, and can release the water and absorb the latent heat during the thermal decomposition, which can effectively inhibit the polymers decomposition and cool the combustible gas generated in the case of fire. In this paper, the magnesium salt flame retardant is synthesized in different conditions. Then the thermal decomposition features of the magnesium salt flame retardants with the smallest particle diameters are characterized by using thermogravimetric analysis and differential thermal analysis. Finally, on the basis of this analysis, optimization parameters for preparing the magnesium salt flame retardant with good thermal decomposition performance are obtained, which may be helpful for guiding the preparation of high-performance magnesium salt flame retardants and providing a beneficial reference.

Abstract: The rise of wavelet analysis in applied mathematics is due to its applications and the flex- ibility. We introduce vector-valued wave wraps with multi-scale dilation factor for space , which is the generalization of univariate wavelet packets. A method for constructing a sort of orthogo-nal vector-valued wavelet wraps in three-dimensional space is presented and their orthogonality traits are characterized by virtue of iteration method and time-frequency analysis method. The orthog-onality formulas concerning these wave packets are established. Moreover, it is shown how to obtain new Riesz bases of space from these wave wraps. The notion of multiple pseudo fames for subspaces with integer translation is proposed. The construction of a generalized multiresolution structure of Paley-Wiener subspaces of is investigated. The pyramid decomposition scheme is derived based on a generalized multiresolution structure.

Abstract: Axial flow compressor is an important component, so the compressor performance is of crucial. Fouling changes blade geometry and blade surface roughness is increased, thus aerodynamic performance is affected. The flow of gas phase and gas-solid coupling phase are implemented to reveal the effect of inlet condition on particle deposition. Based on Euler-Lagrange model, this paper made numerical simulation of gas-solid two phase flow in the axial flow compressor rotor cascade. Simulation result shows that the increase of inlet temperature can result in the reduction of particle volume fraction. And particle mass concentration is affected by particle mass flow rate.