Papers by Author: Xiao Dong He

Abstract: In this paper, we predict the delamination buckling behavior in slender laminated composite with embedded delamination under compressive load by using the finite element method (FEM). For the different delamination size and depth position, we illustrate the various parameters effects on buckling behavior.

Abstract: The response of adhesively bonded lap-joint under transverse impact was investigated by means of DYTRAN software. A finite element model was developed based on cohesive failure in the adhesive layer of the joint. It was found that transverse impact results in shear and peel stress concentration in the adhesive due to the considerable deflection of the joint. The stress distribution in the adhesive layer was asymmetric along the overlap length direction. The peel stress varies from tensile to compressive from one side to the other. Two cracks initiated at two sides of the adhesive layer were observed before the failure of the joint.

Abstract: Joining behavior of long glass fiber reinforced polypropylene (LFT) by three types of adhesive was investigated. Single-lap shear testing was used to evaluate the performance of adhesively bonded structures. The two-part acrylic adhesive DP8005 was determined to be the best among the three adhesive candidates, which was attributed to its low surface energy. The stress distribution in the adhesive layer of the single lap joint was modeled by static elastic analysis using ANSYS software. The shear and peel stresses peaked at the edges of the adhesive layer.

Abstract: By using electron beam physical vapor deposition (EB-PVD) technology, Ti-Al thin sheet with dimension of 450mm×450mm×0.2mm was prepared and the microstructure of Ti-Al deposit was investigated by means of scanning electron microscopy (SEM), atom force microscopy (AFM) and X-ray diffraction (XRD), and then the effect on deposit by re-evaporation of Al was explored by calculating the ratio of re-evaporating capacity with depositing capacity of Al on the substrate. The results indicate that there existed equiaxed crystal and columnar crystal along the cross-sectional may resulted from the transformation latent heats released during the transition course of atoms from gaseous state to solid state, and the variation of target-substrate distance would take effect on the phase composition due to the changing of atoms collision probability and radiant heat quantity absorbed by substrate. The effect on deposit by re-evaporation of Al could be neglected because the re-evaporating capacity of Al was far below that of the depositing capacity.

Abstract: Microarc oxidation (MAO) is a relatively convenient and effective technique to deposit ceramic coatings on the surfaces of Al, Ti, Mg and their alloys. This technique can introduce various desired elements into titania-based coatings and produce various functional coatings with a porous structure. Microarc oxidized (MAO) TiO2-based coatings on titanium alloy were formed in electrolytes containing aluminate and ZrO2 particles. The phase composition of the samples was analyzed by glance-angle X-ray diffraction and the surface morphologies of the samples were observed by a scanning electron microscopy (SEM). In addition, the element concentrations on the surfaces of the samples were measured by an energy dispersive X-ray spectrometer. The experiment results indicated that: MAO coatings, which are porous structures and exhibit good interfacial bonding to the substrate, may possess specific surface structures such as crystal phase, non-equilibrium solid and complex mixed-compounds since complex plasma physical and chemical reactions.

Abstract: Ti3SiC2 is one of the nano-layered ternary ceramics Mn+1AXn, where M is a transition metal, A is an A-group (mostly IIIA or IVA) element, and X is C or N. With the filler of Ag-Cu-Ti, the brazing of Ti3SiC2 has been conducted at 800°C–950°C for 5-10min under 3.5×103Pa in a vacuum. The phase composition and microstructure of the joints were investigated by XRD, SEM AND EPMA. The diffusion of Cu element in fillers through the reaction zone toward Ti3SiC2 is the main controlling step in the bonding process. Joint strengths were evaluated by three point bending test. The maximum flexural strength of joints reaches is 306±11MPa, which is lower than the bending strength of Ti3SiC2, obtained under the same condition.

Abstract: The process of Electron Beam-Physical Vapor Deposition (EB-PVD) preparing SiC coating with liquid evaporation was firstly discussed from a thermodynamic viewpoint. The results showed that the ratio of SiC in the as-deposited coating gradually increases and tends to reach a stable maximum of 0.73 with the evaporation temperature increase from 2500 K to 3400 K. To verify the thermodynamic analysis, amorphous SiC coating was deposited on Si substrate by EB-PVD at 3100 K. SiC concentration across the cross section of coating was calculated from the area of elements spectrum in X-ray photoelectron spectroscopy (XPS) depth profile analysis. The results showed that the average SiC concentration was about 0.7.

Abstract: The buckling deformation of the liner within composite pressure vessel is investigated using acoustic emission (AE) signals. The liner will fail with buckling deformation which is casued by compression stress induced by deformation compatibility beween composite layer and the liner. The experimental results show that these high-amplitude signals higher than 80dB are responsible for the buckling deformation of the liner within composite pressure vessel during unloading process.

Abstract: The process-induced residual stress for laminated composite with metallic plate is investigated by numerical simulation during the curing process. A two-dimensional finite element model is used to compute process-induced residual stress of the laminated composite. Interface formation process between the fiber and the matrix in the longitudinal direction of composites is described by user-defined exponential function and considered in the numerical model. Numerical results show that the prediction is more accurate in the longitudinal direction of composites when the interface formation process between the fiber and the matrix is considered , which has been confirmed in the test.

Abstract: ARMOR TPS panel is above the whole ARMOR TPS, and the metal honeycomb sandwich structure is the surface of the ARMOR TPS panel. So the metal honeycomb sandwich structure plays an important role in the ARMOR TPS, while it bears the flight dynamic pressure and stands against the flight dynamic calefaction. So the active environment of metal honeycomb sandwich structure is very formidable. We have to discuss any extreme situation, for reason of making sure aerial vehicle is safe. And high-frequency vibration is one of active environment. In this paper we have analyzed high-frequency vibration response of metal honeycomb sandwich structure. We processed high-frequency vibration experiment by simulating true aerial environment. Sequentially we operated high-frequency vibration experiment of metal honeycomb sandwich structure with cracks, notches and holes. Then finite-element analysis was performed by way of validating the experiment results. Haynes214 is a good high temperature alloy material of both face sheet and core at present, so we choose it in this paper.