Applied Mechanics and Materials Vols. 268-270

Abstract: To reduce energy consumption, numerical simulations of combustion and decomposition processes in a precalciner were carried out with two different heights of raw meal inlets. In Euler coordinate system the gas phase is expressed with k-ε two-equation model, in Lagrange coordinate system the solid phase is expressed with discrete phase model (DPM), the chemical reaction is expressed with species transport model, and the radiation is expressed with P1 radiation model. The results show that when the raw meal inlets are near the jetting coal pipes, there is much better dispersing condition of CaCO3 but a much poorer coal combustion condition, resulting in a much higher CaCO3 decomposition rate but a lower coal burn-off rate than that when the raw meal inlets are far away from the jetting coal pipes. It is advised to install both the two heights of raw meal inlets in order to obtain not only high CaCO3 decomposition rate but also high coal burn-off rate.

Abstract: The carbon fiber has excellent properties; however, the high cost limited its wide application. Here we report a novel process to reduce the heat emission during stabilization by in situ modification of spinning melt. In this paper, the effect of extruding temperature on the structures of PAN in the PAN/ILs melt was investigated by twin-screw extruder. FTIR and UV-vis absorption spectra of modified samples showed the formation of C=C and C=N group, which indicated the occurrence of cyclization and dehydrogenation reactions of PAN during extrusion process. The degree of cyclization was calculated from DSC test and the degree of cyclization can be up to 24.5% with the residence time of 14 min at 210 oC, which could decrease the heat release in the subsequent stabilization process during carbon fiber production. Therefore, this method should be benefit to improve the processing efficiency during stabilization process.

Abstract: Femtosecond laser with the features of ultrashort pulse duration and ultrahigh peak power can achieve “cold” machining. The recast layer and micro-cracks of the hole wall can be ruduced effectively by applying femtosecond laser in processing air-film holes on turbine blades, and the machining accuracy and consistency of the hole shape will increase. In this paper, the high-speed rotating femtosecond laser beam is adopted in several currently used turbine blade materials for air-film holes machining, and high quality air-film holes without hole wall recast layer and micro-cracks are processed through a large number of experiments to optimize machining technology and technological parameter.

Abstract: Extrusion of magnesium billets is associated with large deformations, high strain rates and high temperatures, which results in computationally challenging problems in process simulation. A simulation was carried out using the finite element software ABAQUS. The computed model was rotational symmetric and built up by meshing. Computed parameters including material characteristics and process conditions (billet temperature. reduction ratio, and ram speed) were taken into consideration. The distributions of temperature were different comparing the transient-state extrusion with the steady-state extrusion. The extrusion simulation was the reliable predictions of strain rate, effective strains, effective stresses and metal flow velocity in an AZ31 billet during direct extrusion.

Abstract: The cutting principle of high speed machining is analyzed, and the key technology of building high speed cutting finite element simulation model is systemic explained. By simplifying high speed cutting process, using the fastest solution of nonlinear finite element software ADINA which is development in recent years to establish the three dimensional finite element model of high speed metal cutting, and to predict the cutting force of different cutting tool geometry parameter combination of high speed cutting process, the high speed cutting processing cutting tool analysis and processing parameter optimization analysis method are put forwarded, so as to provide a new tool for the research of high speed machining process and provide basis for the cutting tool choice during high-speed nc cutting process.

Abstract: 2-(2-Nitroethenly)thiophene can be obtained from 2-thiophenecarboxaldehyde and nitromethane under Knoevenagel condensation conditions. We used beta-alanine as a catalyst and microwave irradiation as the energy source. Different reaction condition, such as beta-alanine consumption and reaction time were studied. The results indicate that the application of microwave irradiation increases the yield of desired compound. beta-Alanine-catalyzed activation of 2-thiophenecarboxaldehyde provides an efficient access to 2-(2-nitroethenly)thiophene with reusability of the catalyst.

Abstract: According to the technical problems such as low stiffness vibration and dimension error in milling Ti6Al4V thin-walled component, the manufacturing with paraffin reinforcement is studied. Firstly, paraffin formula for milling thin-walled component is researched. Secondly, applying the finite element method (FEM) to predict the deformation of machining with paraffin reinforcement and the corresponding milling experiments is done to check the the validity of the model. Finally, the influences of machining accuracy about different paraffin formulas for the same component are obtained. This study supplies support for the research of paraffin formula which are based on reducing the distortion of workpiece.

Abstract: In this study, low pressure Ar plasma is used to improve the surface hydrophilicity of the polyethersulfone (PES) membrane. The low pressure Ar plasma generated by radio frequency (RF) glow discharge was acted on the PES membrane surface to observe the change of the hydrophilic nature. This paper discusses the different plasma power, treatment time and plasma fluxes conditions on PES membrane modified influence. Experimental results show that with the plasma power and plasma fluxes increase and treatment time prolonged, the surface hydrophilicity of the PES membrane continues to increase and no more changes were observed when it reached to a certain value. The best condition was carried out at 60W, 120s, 20sccm, in this condition, the hydrophilic nature of the PES membrane is remarkably improved.

Abstract: Perforating parameters, such as charge density, charge quantity and shooting density, are the important factors that affect the strength security of perforation string. Finding out the relationship between this two and understanding the regularity has the guiding significance to avoid the perforating accidents. Based on the research about the strength security of perforation string at the moment of perforating, taking a perforated completion gas well as an example, by changing the perforating parameters and conducting the contrastive analysis and research, then gets the regularity understanding about the influence of the perforating parameters on the strength security of perforation string:When the charge density is more than 1.9g/m3, the amplification of peak pressure will slow down ,and the influence of charge density will decrease; When the charge quantity is more than 40 gram, the amplification of the peak pressure on the packer and the peak stress of tubing will slow down ,and the influence of charge quantity will decrease; When the shooting density is more than 20 hole/m, the amplification of peak will slow down, and the influence of shooting density will decrease.

Abstract: The casting process design and simulation of the impellor of 65KZL slurry pump were presented in this paper. Three kinds of casting processes were designed and simulated using ProCAST. Practical production test of those casting processes was also carried out. The simulation results were consistent with the practical production test. The optimized cast process was selected, and the quality of the impellor was improved.