Advanced Materials Research Vols. 228-229

Abstract: Among all the influential factors, the service quality of machine tools is the most important one for workers to decide their machine tools selection in process planning. This paper proposes an evaluation model for service quality of machine tools, aiming to help workers select machine tools on a reasonable basis. An evaluation indicator system of machine tools’ service quality is established based upon a thorough investigation into how the service quality of machine tools manifest themselves. The evaluation indicator system includes the following five aspects: processing cost, processing time, machining precision, green attributes and reliability. The least square method is used to establish an optimization model that determines the weight of indicators based on subjective weight-giving and objective Weight-giving. Finally, a grey relational analysis is conducted to evaluate the service quality of machine tools. Thus we provided an effective decision method for workers to decide their machine tools selection in process planning.

Abstract: Aiming at the difficulty in quality problem character information classification, the ODC (orthogonal defects classification) method is introduced. Abide by the discipline of ODC; the quality problem character information is classified into four orthogonal groups. And the character information of each group is analyzed.

Abstract: In this paper, the stability analysis of switched uncertain neutral systems with mode-dependent delays under arbitrary switching rules is presented. Based on common Lyapunov functional, and combined with the analysis of matrix inequalities, the delay dependent stability conditions are obtained in the form of linear matrix inequalities(LMIs)which can be easily solved by LMI toolbox in Matlab. Finally, a numerical example illustrate that the proposed criteria are effective.

Abstract: High pressure jet nozzle is the key technical equipment to determine the cutting performance of coal cutting jet, experimenting of conical convergent nozzles as the research object, based on the orthogonal principle of Taguchi method, to the quality characteristics of nozzle outflow velocity, based on jet factors of cutting performance to select parameters and established nine nozzle models to design orthogonal experiment; by ANSYS finite element analysis software to simulate fluid flowing inside the nozzle and calculate the curves of fluid velocity, and calculated according to the analysis of variance table, determined reduction angle  and nozzle outlet diameter d as two factors of significantly affected outflow velocity, obtained the optimal designed parameters of nozzle; finally, by ANSYS finite element analysis software to verify the results of optimization, the experiment results the same with Taguchi method, the conclusion is great significance for the high-pressure jet cutting coal technology and systems to improve and optimize.

Abstract: The effect of an external magnetic field on the hydration behavior of nanoscopic n-octane plates has been extensively investigated using molecular dynamics simulation in an isothermal-isobaric ensemble. The solute plates with different intermolecular spacing have also been considered to examine the effect of the topology of hydrophobic plates on the adsorption behavior of confined water in the presence of an external magnetic field with an intensity ranging from 0.1T to 1 T. The results demonstrate that magnetic exposure decreases the density of water for the plates with intermolecular spacing of a0 = 4 and 5 Å. This suggests that the free energy barrier for evaporation can be lowered by the applied field, and the hydrophobic solutes consisting of condensed n-octane molecules are apt to aggregate in the aqueous solution. In contrast, the magnetic field improves the dissolution or wetting of solutes comprised of loosely packed n-octane plates of a0=7Å. A magnetic-field-induced adsorption-to-desorption translation, which is in agreement with the experimental results provided by Ozeki, has also been observed for the plates with intermolecular spacing of a0 = 6 Å.

Abstract: Strip casting process is a kind of promising near net shape technology for producing magnesium alloys strip. The microstructure and mechanical properties of CO2 laser welded as-cast AZ31 magnesium alloy sheet were investigated. The microstructure of base material (BS) was typical columnar dendritic structure. A significant grain refinement occurred in the fusion zone (FZ) due to the rapid cooling, while an obvious grain coarsening occurred in the heat affected zone (HAZ). The tensile strength and elongation at fracture of weld joints were reduced due to the weld depression caused by high heat input. The hardness in the FZ was the highest due to fine grains, while there was a decrease in hardness of the HAZ, but little variation compared with the hardness of the BS.

Abstract: Effects of laser modification welding (LMW) on formation of full-penetration weld were studied, which were based on the laser beam welding (LBW) process of 5A02 aluminum alloy. The results indicated that the welding defects (such as undercut, surface depression and so on) could be improved obviously, and the microstructure of joint by LMW could be finer than that of joint only by LBW. Besides, the strength and toughness of joint would also be increased to some extent by LMW after full-penetration LBW. Therefore, the LMW is an effective method in order to strengthen joint of LBW.

Abstract: To obtain the influence law of laying combination and lay pitch multiple on mechanical strength of steel wire product, we took 6×19IWS right lang lay and right regular lay wire ropes as examples, combining with the strength theory, nonlinear finite element analysis were carried out with ANSYS software. The simulation results show the mechanical strength of the lang lay wire rope is better than that of the regular lay at the same lay pitch multiple; the lay pitch multiple of rope has a great impact on mechanical strength of steel wire product, however, the impact trend is similar among difference laying combinations, meanwhile the effect of the lay pitch multiple of strand is relatively small. Finally, finite element model for wire rope was verified reasonable through tensile experiment. Research results have important applications value for structural design and rational use of wire rope.

Abstract: As a key component of proton exchange membrane fuel cell (PEMFC), the bipolar plate’s performance will directly affect the power output and battery life of the fuel cell. The conventional metallic bipolar plate is prone to warp, and has large flatness error with residual stress induced by forming process. This will result in contacting incompletely with membrane electrode assemblies (MEA) and lower fuel cell efficiency. A cylindrical structure of the PEMFC metallic polar plate is proposed to improve its stiffness and to reduce assembling error of the fuel cell. The polar plate features, which were originally designed on a flat surface, are projected onto the cylindrical surface with a certain curvature. Two cylindrical polar plates are welded together to become a bipolar plate. The finite element method is applied to compare the stiffness of the conventional and cylindrical polar & bipolar plates. The cylindrical bipolar plate has better stiffness and anti-warping than the conventional bipolar plate. The feasibility of the cylindrical structure is verified by experiment and provides a new idea for the improvement of the bipolar plate and fuel cell stack.

Abstract: Using finite element analysis software ANSYS/ LS-DYNA, establishing the plow cutting coal seam 3D simulation model, simulating plow bit cutting coal seam dynamic process. under study, obtaining plow bit the cutting resistance, plow speed of time process curve, analyzing the influence on cutting energy consumption of the different cutting depth, separation distance and width, reaching the rule of cutting energy consumption changing with plow bits’ structure parameter and design parameters, in order to reduce the energy consumption and resistance, cutting depth and plow bits spacing ought to be selected by the real coal seam face conditions.