Advanced Materials Research Vols. 291-294

Abstract: Uni-axial hot tensile tests were used to investigate the transverse superplastic deformation of laser welded Ti-6Al-4V sheet. Microstructures of the weld bead before and after superplastic deformation were observed by optical microscope. The maximal deformation of 46% was obtained on weld joint at strain rate of 10−2s−1 and temperature of 1173K. A coefficient K was introduced to evaluate the non-uniform deformation of weld joint. After superplastic deformation the microstructure of weld bead transformed into lamellas from original acicular structure.

Abstract: The influence of Silica fume/Nanosilica on the Performance of phosphoaluminate cement was studied in the paper. The microstructure and morphology was determined by X-ray diffraction and scanning electron microscopy. The experimental results show that the phosphoaluminate cement with 4% of added Silica fume/Nanosilica(1:1) by weight of cement has an optimum splitting strength, in which the increase of splitting strength are about 15.1%,11.8% and 24.6% at 3days,7days and 28 days. The reason for causing the above results are the hydration rate and the amount of the hydrates of PALC with 4% Silica fume/Nanosilica have been increased significantly at different hydration time because of the role played by Silica fume and Nanosilica together.

Abstract: In order to measure the friction force between skin and varied wet knitted fabrics, it was proposed that the complete wetting fabrics could be hung on the line for different time to get the testing fabrics with different water content (wet state). The relative hanging time was innovatively used to characterize the water content in the knitted fabric. Then the friction curves between knitted fabrics and skin could be measured on the new lab developed fabric-skin friction tester in 6 different wet states. It was found that there were other three kinds of friction-sliding displacement curves except normal friction curve. According to the characteristic of various friction curves, 4 kinds of friction indexes were added to characterize the friction properties between knitted fabric and skin in different wet state.

Abstract: Water lubricated rubber bearing is one of the most appropriate bearings widely used in submerged pump for drainage. The apparatus for studying the tribological behaviors of the water lubricated rubber bearings has been devised and established in the paper. The experimental studies on the tribological properties of the rubber bearings have been conducted under different load and velocity using the apparatus. Effects of load and velocity on friction coefficient of the rubber bearings have been estimated. The experimental results show that the friction coefficient decreases with increasing velocity; the friction coefficient increases at first and then decreases with increasing load; the friction coefficient increases sharply with the rising temperature. The experimental results also indicate that there is an appropriate bearing clearance which the friction coefficient is minimum.

Abstract: In this paper, nickel coatings (on phosphor bronze substrates) were prepared using pulse electrodeposition method. The friction and wear behaviors of nanocrystalline nickel coating compared with coarse-grained nickel coating against AISI 52100 steel were investigated using l-butyl-3-octylimidazolium tetrafluoroborate ionic liquid and perfluoropolyether as a reference lubricant on reciprocating ball-on-flat UMT-2MT sliding tester. The morphologies of the worn surfaces were observed using a scanning electron microscope. The chemical states of several typical elements on the worn surfaces were examined by means of X-ray photoelectron spectroscopy. The results indicated that NC nickel coatings have better tribological properties than that of coarse-grained nickel coatings under lubricated conditions. This was partly attributed to the high hardness of the NC nickel coating and L-B408 ionic liquid formed tribochemical reaction films under NC nickel coatings.

Abstract: A new method of numerical differentiation and time domain integral was proposed in this paper, its idea was originated from the analysis of the time domain vibration response. As to numerical differentiation, the discrete sequence could be considered as the displacement response of an one degree-of-freedom system, and the velocity and acceleration response corresponding to the first and second order numerical differentiation. As to time domain integral, the discrete sequence could be considered as the acceleration response of an one degree-of-freedom system, and the velocity and displacement response corresponding to the first and second order time domain integral. All these work were established based on the discretization analysis of Duhamel integral. Numerical simulation result indicates the effective and better accuracy of this new method.

Abstract: Vibration signal of rolling-element bearing is random cyclostationarity when a fault develops, the proper analysis of which can be used for condition monitor. Cyclic spectrum is a common cyclostationary analysis method and has a great many algorithms which have distinct efficiency in different application circumstance, two common algorithms (SSCA and FAM) are compared in the paper. The FAM is recommended to be used in diagnosing rolling-element bearing fault via calculation of simulation signal in different signal to noise ratio. The cyclic spectrum of practice signal of rolling-element bearing with inner-race point defect is analyzed and a new characteristic extraction method is put forward. The preferable result is acquired verify the correctness of the analysis and indicate that the cyclic spectrum is a robust method in diagnosing rolling-element bearing fault.

Abstract: This study investigates the effect of rail material on their wear behavior of rail-wheel system by using MMS-2A twin-disc abrasion tester. When one type of wheel matches with different types of steel rail, the worn lose of the steel rail decreases with the increasing hardness, and the abrade wear of wheel increases. The trend showed by the SEM micrograph of the wear scar was consistent with the results of the worn lose.

Abstract: A detailed investigation has been carried out to determine the inhibition behavior of a mixed additive gelatin+thiourea+cresol (GTC) on zinc electrowinning from sulphate solutions containing germanium. The results indicate that zinc redissolution is inhibited because of germanium in existence, current efficiency is increased and surface morphology of cathode zinc is improved using proper GTC in the electrolyte. Cathode polarization curves were traced and analyzed to indicate that additive GTC may inhibit the depolarization and stimulating hydrogen evolution effects of germanium on zinc deposition.

Abstract: Radar graph fractal method is an effective description for the contour of wear debris. In this paper the principle that radar graph fractal dimension analyzed by computer was researched. In analysis, how to extract contour of wear debris from surrounding is looked as an important process, and three methods was introduced to deal with it: manual method is simple to do, but the result is not accurate for the process could be affected by human mistake; automatic method can deal with the case that multi-wear debris being in an graph, and do the statistic for the result, but it is not good for the graph that wear debris’ gray is similar to surrounding’s, the wear debris contour gotten by this method is often distortional, so the concepts that edge dot extracted ratio and the optimizing threshold method can be introduced to improve it; Semi-automatic method is easy to modify the gotten wear debris contour by change the contrast of graph and the gray of edge dot extracted artificially, improve the definition of wear debris contour. The method radar graph fractal dimension analyzed by computer is more simple and convenient than by hand, its result is also more accurate, better for the using of radar graph fractal description.