Advanced Materials Research Vols. 472-475

Abstract: Aiming at the mechanical property abnormality of a certain cylinder test piece for aerospace application, scanning electron microscope and metallographic microscope were used to observe and analyze the fracture and weld structure of test pieces under tensile test, and the reason of property abnormality was determined. On the fracture of welding test pieces under tensile test formed two evident characteristic zones, one of which was the initial zone looking like arc ribbons alternating with each other. More obvious texture structure formed in the welding heat affected zone, with the direction consistent with that of the fracture in the up arc zonal fracture region. The reason of the abnormality was that relatively significant texture structure formed in the welding heat affected zone, while its formation was related to the temperature field and stress during the process of welding.

Abstract: Dissolving action of Ag and P during weld brazing of thick copper plates without preheating was investigated and the mechanical performance of the weld of copper was analyzed. The difference of dissolving action between Ag and P is that Ag-Cu binary alloys dissolve base metals in form of body dissolution, while P diffuse into grain boundary first and reach the limit solid solubility gradually then the surface layer of base metal begins to dissolving. The stirring function of arc is important for dissolving action of P but has little effect on dissolving action of Ag. P in form of rigid and brittle Cu3P increases the micro-hardness of welds.

Abstract: Considering that the distributings of sensors will affect the fault diagnosis results directly, how to distribute vibration sensors for fault diagnosis in axial piston pump are researched. The corresponding feature frequency bands of various faults are analyzed, effects of collecting signals are compared in differrent fixings of vibration sensors, placements scheme of the sensors is proposed. Combined with the experimental data, the best distributings of vibration sensors is obtained. Research result provide a strong support in the pump monitoring and fault diagnosis field and reference in other complex mechanical vibration fault diagnosis field.

Abstract: Aiming at the problem of non-stationary noise is difficult to eliminate, the audio signal is analyzed by the means of time series analysis. The auto regressive Integrated Moving Average (ARIMA ) model is established. The recursive extended least squares (RELS ) algorithm is adopted to realize the real-time estimation of parameter. The kalman filter is used for compensating the model error of the audio test system. It is concluded from the simulated results that the proposed methods achieve better smoothing effects and more effective inhibitions of the audio signal random noise, and improve the signal-to-noise ratio of the audio signal.

Abstract: The whole mode of technological innovation in Tangshan should rely mainly on the imitating innovation or the followed innovation, partly on the primitive innovation. It should be carried on according to enterprise's detailed conditions to employ specifically. The paper analyzed the Silicon Valley of American, Gulf of Tonkin of Japan and the Chinese Yangzi Delta area, and found they had different innovation pattern and respective superiority. These provided some experience of scientific and technological innovation for Tangshan bay. The essay planned the strategy from three aspects, including the strategic mentality, the strategic choice and the strategic measure. It pointed out the Tangshan bay should fully use nearly alliances, highlight the superiority outward, play jointly with other cities and insist opening-up independently.

Abstract: Efficient two-steps method for the synthesis of octa(aminopropylsilsesquioxane)(OAPS) was described in this paper. The chloride salt of OAPS was prepared by the hydrolytic condensation of γ-aminopropyltriethoxysilane in methanol, with hydrochloric as a catalyst. The influence of several processing on the synthesis has been ascertained. The chloride salt of OAPS can be obtained in 42.1% yield after a reaction time of 18h, which is a much shorter than that required for traditional method. Neutralization of the chloride salt of OAPS to OAPS was accomplished by eluting solutions of this hydrochloride in methanol through a column of Amberlite 717 ion-exchange resin. The structure of products was determined by FTIR, MS, Elemental analysis, 1H, 13C, and 29Si NMR. TG curve of OAPS shows that the compound has high decomposition temperature and higher char residue yield.

Abstract: Simulated heat affected zone continuous cooling transformation curve was measured by means of Gleeble 3500 thermal simulator. According to the results of microstructure observation and hardness measurement, influence of cooling rates on the microstructure and hardness in coarse grain zone of high-strain pipeline steel X80 was studied. The results illustrated that softening in coarse grain zone was ubiquitous problem for high-strain pipeline steel X80. There were mainly four types of phase transformation in coarse grain zone of high-strain pipeline steel X80. Polygonal ferrite(PF) and a small quantity of pearlite, granular bainite, bath bainite and bath martensite were obtained after different cooling time.

Abstract: The SHCCT (simulated heat affected zone continuous cooling transformation) of 9Ni cryogenic steel were investigated. The microstructures observed in simulated heat affected zone (HAZ) continuous cooled specimens are composed of bainite (B) and martensite (M) depending on the cooling rates. The dimension of prior austensite grain, M-A constituent content, M-A dimension, M-A area density increase with increased the time of t8/5.

Abstract: In this study, the fabrication of the desired SPR joints was investigated as a function of the preheat temperature and strain rate. To determine the optimum preheat temperature, Gleeble thermal analogue testing of 2mm thick magnesium AZ31 was used to assess the combined influence of preheat temperature and strain rate on the strength and total elongation of magnesium AZ31. Magnesium alloy AZ31 with a thickness of 2mm was preheated with various temperatures prior to self-piercing riveting. The appearances, cross-sections and mechanical tests of the SPR magnesium AZ31 joints were investigated. It was found that a preheat temperature of 180 to 200oC largely eliminated the cracking in magnesium AZ31 joints. The joint strength increases with increasing preheat temperature from ambient to 200oC. The strength increase is attributed to the reduction in joint cracking and an increase in mechanical interlock between the rivet and work pieces.

Abstract: It gave a better strength that taking lap laser welding (llw) instead of resistant spot welding (rsw) to assemble the framework and the flankwall of stainless steel car body structure, and the fracture situations of fatigue test were different in the two welding methods. That was chiefly connected to the stress distribution and concentration of welding joint. The analyses on stress distributions and concentration factors of the two joints in different external loadings were made in this paper. The results indicate that the stress concentration factor of llw joint on the flankwall is 73.4% lower than that of rsw and the value on the framework is 81.6%. The crack initiation site of fatigue test appears at the place with the highest stress concentration, which is agreed well with the theoretical analysis.