Abstract: Currently, friction stir welding has had a wide application in connection of aircraft panels. However, researches are rarely carried on in domestic aeronautics field, which involves the differences between FSW panels and traditional riveted panels in aspects of strength and stabilities under various working conditions such as shear and tension and compression. Picture frame fixture was used in this research for comparison test between two types of aircraft panels, which were connected to stringers by riveting and friction stir welding (FSW). Finite element models were established to simulate the panels in the shear tests which proposed a method to simulate the connection types. It is found that the FSW connection performs better than riveted connection in aspects of limiting load and initial buckling load, which proved that panel connected by FSW is better than riveting in mechanical properties. The test result is proved by FEM simulation, and vise versa.
Abstract: Based on the non-equilibrium Green’s function in combination with the density-functional theory, The spin-dependent transport in the short graphene nanoribbon (graphene sheet) asymmetrically coupled to the electrodes of Au chains is investigated. It is found that a fully spin-polarized current (close to 100%) can be produced at the output port. The physics underlying attributes to the spatially separated edge states of the sheet caused by asymmetric contacts. Especially, the current's spin polarized direction can be tuned simply by changing the contact locations of the electrodes to the graphene sheet.
Abstract: In highway pavement engineering, mineral aggregate gradation is a key consideration in mixture design. The max density curve theory is one of the most popularly-used methods to design mineral mixture gradation. The main objective of this research is to present a numerical method for investigating impacts of mineral aggregate properties on model parameters of the max density curve theory. Through this study it was found that the maximum particle size gave an important impact on the model parameters, even though the model parameter n is around 0.45 for popularly-used mineral mixtures.
Abstract: A highly nonlinear, dispersion flattened hybrid nanofiber with a silicon/silica cross-slot-structure nanocore is proposed and analyzed, which is insensitive to polarization for implementing quasi-TE and quasi-TM fundamental modes transmission due to the cross slot effect. Simulation results show that fundamental mode with ultra-small mode effective areas and high nonlinearity at TE and TM polarizations, which are confined in the narrow cross slot by four silicon ribs, can be achieved via this cross-slot-structure core. Moreover, the cladding of four large-air-holes contributes to the tailoring of the group velocity dispersion (GVD) and further enhancment of the nonlinearity. Our results indicate that ultra-small Aeff of 0.098μm2 and flat anomalous GVD with less than 13.5 ps.km-1.nm-1 dispersion ripple at C-band are realizable.
Abstract: The dispersion of CNTs in NR and the interaction of CNTs/NR as well as the influence of CNTs on properties of NR used for tire tread were investigated by SEM, mechanical test and DMA analysis. The modified CNTs were thought to have better interaction with NR and higher dispersion than the unmodified one by the SEM and cure parameter analysis. And the addition of modified CNTs into the NR vulcanizate for tire tread improved the tear strength, modulus and anti-abrasion as well as the heat build-up when the formulation was adjusted.
Abstract: The band structures, density of states, and absorption spectra of pure and Cd doped single-walled (8, 0) ZnO nanotubes are calculated using first-principles based on density functional theory. The calculation results show that the import of Cd leads a remarkable decrease to the forbidden bandwidth of ZnO. Consequently, more electrons in the valence band can be motivated to the conduction band by the visible light, which results in a further enhancement of visible light absorption and a wider absorption range.
Abstract: PET/60HBA-MWNTs Liquid Crystalline Polyester (LCP) composite was synthesis by melting polymerization process with a novel method of reacting in acetic anhydride solution. FTIR, XRD, POM, TGA and mechanical properties tests were applied for the characterization of modification of nanotube, crystallization property, thermal and mechanical properties. The results indicate that thermal and mechanical properties of LCP polyester are all enhanced with 0.3wt% MWNTs addition. The degradation temperature (Td) increased for 8°C and the modules, strength and breaking elongation are increased by 39.0%, 62.3% and 46.4% respectively.
Abstract: ZnO-based ceramic was densified at low temperature by using PSP as binder. The results showed that phenolic resin filled in the ZnO grain boundary layer. The sample has a well hardness of 0.8 GPa and bending strength of 78 MPa. The effect of temperature on the microstructure and mechanical properties was also investigated. It was found that the samples sintered at 300 °C showed higher density and better mechanical properties.
Abstract: The weld overlay technology of high strength low alloy steel (HSLA) and austenitic stainless steel is widely applied in such fields as petroleum, chemical industry and energy, and its service environment is of high temperature and corrosion. As the matching performance is often poor for both austenitic stainless steel and high strength low alloy steel, cavities and crackles occur easily at the joints, which cause brittle fractures with dangerousness to some extent. So in the present study, the metal-inert gas welding (MIG) is used to clad the austenitic stainless steel to HSLA. In the experimental group, 4mm buffer layer (E309L) and 8mm cladding layer (E347L) were successively cladded on the substrate (Q345B), while 12mm cladding layer was directly deposited on the substrate in the control group. The hot corrosion tests were done, and through the scanning electron microscope (SEM), we observed the cross-sectional morphology. By the X-ray diffraction (XRD), we analyzed ingredients of the corrosion products. The corrosion products in the experimental group mainly consist of iron and nickel oxides, while the products are mainly iron complex compound and salt in the control group. The SEM results show the area near the welding seam of the specimens without buffer layer had been corroded severely. However, only a slight corrosion occurs adjacent to the welding seam. This demonstrates that the buffer layer can protect the specimens from being corroded.