Applied Mechanics and Materials Vols. 80-81

Abstract: In this paper, ABAQUS was used to simulate the stamping process for electrodeposited nickel coating. In the simulation, a built-in cohesive zone model of ABAQUS was used to present electrodeposited nickel coating steel‘s interface performance. The computational results shows that, at the interface, the normal stress was between -113.765～3MPa，and the maximum tangential stress is 50 MPa. The maximum interface stress is at the die fillet during the process of stamping，and we analyze the case of delaminating and is used to assess the influence of the blank holder force，the clearance between the punch and the die and the tool radii. This method can be used as guidance for battery shell’s forming manufacture.

Abstract: This paper present Acoustic Emission (AE) generated during fatigue mechanism of API5LX70 steel which was widely use as gas pipeline materials. Fully reverse (R=-1) constant amplitude fatigue test were done with four different stress amplitudes which were 437.5MPa, 406.25Mpa, 390.6MPa and 359.4MPa respectively. An observation from those tests shows that AE Count gives a significant value during cyclic softening and bauschinger effect. Crack initiation indicated by rapid increase of AE count values at positive peak stress and followed by high AE count values around zero stress which indicate crack closure phenomena. Among all four tests, it was show that AE activity from fatigue test with amplitude of 359.4MPa can be significantly divided into 3 region which correspond to crack incubation stage, microplastic and slip plane formation stage and crack initiation and propagation stage. Further analysis was done by separating AE signals from those 3 regions into 6 different groups. Ten AE signatures from each group were selected to calculate AE RMS and AE kurtosis. Analyses on AE RMS which correspond to overall energy of the signal were useful to indicate the microplastic and slip plane formation stage and crack initiation and propagation stage while AE kurtosis was useful in indicating crack stage including initiation, propagation and closure stage.

Abstract: Effect of calcination temperature on spinel LiMn₂O₄ by molten-salt flameless combustion synthesis using the lithium acetate (lithium nitrate), manganese acetate (manganese nitrate) as raw materials was studied. The structural characterization and morphology of the powder were measured by X-ray diffraction and Scanning electron microscopy. The results indicated that the main phase was LiMn₂O₄, which could be obtained at 400-700 °C. The product crystallinity and particle size increased with increasing calcination temperature, but the capacity and cyclic stability decreased. When LiMn₂O₄ was calcinated at 400 °C and 500°C, the initial specific capacity at 0.1C rate was 104.2 and 101.5 mAh·g^-1, respectively. After 30 cycles, the discharge capacity retention rate was 80.4 % and 83.5 %, respectively. The performance was the worst when LiMn₂O₄ was calcinated at 700°C, when the initial specific capacity was only 81.9 mAh·g^-1.

Abstract: Zn-Al-Si cast alloys with different content Al and Si such as ZA11Si1, ZA24Si3 and ZA40Si5 were fabricated by metal mould. Zn-Al-Si alloys were composed of α+η or α+η and Si phase. The dendritic particles in ZA11Si1 were smaller than ZA24Si3 and ZA40Si5 and Si phase did not appear in it. The microstructures of ZA24Si3 and ZA40Si5 alloy were larger dendrites and more lump, strip Si phases were dispersed unevenly. ZA24Si3 had the highest mircoharness compare with ZA11Si1 and ZA40Si5, which had the almost same microhardness. ZA11Si11 wear volume was the lowest than those of the pure Zn and the other two Zn-Al-Si alloys and its wear resistance was the best. 11 wt% Al and 1 wt% Si content in the Zn-Al-Si alloy favored the microhardness and wear resistance improvement.

Abstract: In this work, CrN/NbN nanometer multi-layers were deposited on the metal substrates by a dual-target DC reactive magnetron sputtering system. X-ray diffraction, Scanning Electron Microscope and Energy Dispersive Spectrometer were used to analysis the phase composition, crystal structure, surface morphology, fracture morphology and elemental composition of thin films. Micro Hardness Tester and wear-resistant experiments were used to test the hardness and wear properties of the films.

Abstract: Phase transition cooling (PTC), using the absorbed latent heat during the melting of phase transition cooling medium to cool and solidify alloys in the process of casting, is a new casting technology. Specimens of pure Al were prepared by this method in the paper. The temperature field of the casting was simulated with Ansys software. Parameters which affect the process of solidification were simulated too. The results showed that the pouring temperature of melt and the amount of phase transition medium have great effect on the process of solidification.

Abstract: Fatigue test was carried out on E36 steel no reinforcement welding joint under the same constant amplitude load with ultrasound fatigue tester independent designed by Tianjin University. Test results showed that the specimen would enter infinite life area after 1 x 10⁹ cycle times; All broken specimens fractured in the welding seam. We observed fracture surface using SEM and found all the crack initiation from defects. This paper further analysed the influence of nature, size, position, and distribution of defects on fatigue life.

Abstract: A serial of experiment studies on the friction and wear behaviors of the carbon strip/copper contact wire under the electric current were carried on the pin-on-disc tester. The results indicated that the tribology performances were remarkably affected by the electric current. The friction coefficient decreases with an increase of electric current. However, the were volume increases with increasing of electric current, and the worn surface of carbon strip become severer and severer with the increasing electric current. Therefore, the electric current play roles of lubrication and accelerating wear in the process of electrical sliding friction. By the analysis of EDX, it is seen that the oxide wear exists in electrical sliding friction process. Observing the worn surfaces of copper pan sample, it is found that the electric current increases the material transfer of carbon strip.

Abstract: Superplasticizers with various of length of side chains, density of the carboxylic (-COO-) and sulfonic groups (-SO3-) have been synthesized based on different monomers and ratios. The effects of these structural factors on the properties of cement pastes were investigated though measurements of paste fluidity, adsorption amount and Zeta potential (ζ-potential). The results indicated that the higher density of -COO^- and -SO₃^- and the longer of polyoxyethylene (PEO) side chains contributed to the dispersion and adsorption amount of cement pastes in the presence of the same dosage of polycarbosylate superplasticizer. The results indicate that -COO^- and -SO₃^- mainly provide electrostatic repulsion effects and PEO side chains contribute to the steric hindrance repulsion during the process of hydration of cement.

Abstract: In this testing research, a series of High Performance Recycled Aggregate Concrete (HPRAC) with recycled aggregate were prepared and their mechanical behaviors were tested, especially uniaxial compressive stress-strain behavior. The influence of the recycled aggregate replacement on mechanical behaviors of HPRAC was studied by changing replacement ratio of recycled aggregate. Testing results show that the strength of HPRAC decrease a little with the increase of the content of recycled aggregate; the uniaxial compressive stress-strain curve of HPRAC is similar to that of ordinary concrete, and the ductibility of HPRAC improve with the increase of the content of recycled aggregate; the fitted regression curves (especially numerical model) approach to measured curves and can be used in constitutive relations analysis for concrete structure.