Papers by Author: Zhao Hui Hu

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Authors: Li Ma, Ting Zhang, Xiao Li, Zhao Hui Hu
Abstract: Large-scale Ni-based super-alloy sheet has been prepared by electron beam physical vapor deposition (EB-PVD). Microstructure and the dislocation structures in the γ-γ′ double phase alloy under different temperature after tensile strain are studied with Transmission electron microscopy (TEM). The results show that the dislocation glide in single slip system and shearing mechanics, the dislocation climb with part shearing, absolute dislocation climb and cross slip, dislocation round are a course of the interacting degree between dislocation and γ′ phase gradually weakened under the tensile temperature from room temperature to high temperature, so as to decrease materials strength and increase plasticity.
251
Authors: Qi Zhong Huang, Zhao Hui Hu
Abstract: Water absorption behavior and mechanical properties variation of the carbon fiber reinforced epoxy matrix composites (CFRP) immersed into artificial seawater were investigated by experiments. The rate of water absorption of the composite specimens is gradually reducing as the duality of immersion increasing. Due to the reversible and irreversible changes in the resin matrix and the failure of the fiber/matrix interface, the tensile strength, the flexural strength, and the ILSS of the composite specimens after 70 days immersion decreased 9.3%, 13%, and 17% respectively. And the tensile modulus and the flexural modulus the specimens after desorption were 83% and 70% of the original state, respectively
209
Authors: Li Ma, Xiao Dong He, Zhao Hui Hu, Yue Sun
Abstract: This study concerned with the optimum design, microstructure and mechanical properties analysis of a multi-layered metal/intermetallic materials consisting of Ti and Ti3Al prepared by the electron beam physical vapor deposition (EB-PVD) technology. Based on fracture mechanics and numerical simulation method, the optimized microstructure of Ti-Ti3Al multi-layered materials has been obtained by analyzing the relation curve between structural parameters and work of fracture of materials, then dual-target evaporating method was used to evaporate Ti and Ti-47Al bar alternately to form Ti/Ti3Al thin sheet about 0.12mm thickness. Pattern and phase analysis by SEM and XRD showed that there was homogeneous and continuous interface between layers and the intermetallic layers were made up of α2 phase alloy. The tensile curve of Ti/Ti3Al microlaminates represented the characteristic of multi-layered materials and the maximal extensibility of sample as deposited reached 5.83% and the fracture appearance showed ductile rupture feature.
1575
Authors: Jun Shi, Qing Zeng, Xiao Dong He, Rong Guo Wang, Zhao Hui Hu
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.
333
Authors: Yong Dong Xiao, Zhao Hui Hu, Hong Cheng Gao, Ji Min Li
Abstract: The residual stress and the effect of microstructure prameters on failure performance of Ni/Ni3Al multi-layered sheet were studied by Correlative theory and FE method. The results showed that the fracture work increases gradually with the increasing of layer number or thickness ratio. However, the rising extent reduced gradually and when the two parameters exceeded a certain value, the fracture work would not be changed. The value of residual stress reached its maximum at the centre and reached its minimum at the edge of multi-layered sheet. Residual stress in Ni layers and Ni3Al layers was compressive stress and tension stress respectively. With increasing of layer number or thickness ratio, compressive stress would rise gradually and compressive stress would reduce gradually.
118
Authors: Li Ma, Zhao Hui Hu
Abstract: Large-sized Ti/Ti-Al micro laminated thin sheet with thickness of 0.12mm was prepared by high-power electron beam physical vapor deposition technology, and then tensile tests of specimen after hot-pressing densification were carried out at room and high temperature, and tensile specimen was examined the fractured surfaces by SEM and OM. It was found that the tensile specimen under room temperature presents a compound quasi-cleavage and intergranular fracture, and a certain plastic deformation of Ti toughening layer was detected during fracture process. Tensile fractured surfaces under high temperature present the feature of compound dimple models and quasi-cleavage, furthermore, the size and the quantity of dimple exhibited an enhancing trend with test temperature increased. Results show that the cracks will stagger along the inter-laminar interface or the layer due to which micro-laminate expresses a good characteristic of delayed fracture. The toughening mechanisms are that the crack deflection and micro-bridge connection caused by the toughening layers increases crack propagation resistance.
308
Authors: Li Ma, Hai Bo Wang, Zhao Hui Hu
Abstract: A microlaminate consisting of Ti and α2-Ti3Al+γ-TiAl has been synthesized using electron beam physical vapor deposition technique. The microstructure and various properties have been explored. It is demonstrated that the nano-hardness and elastic modulus of Ti layer and Ti-Al layer are of gradient distribution according to the distance to the interface layer which may be results from the pile-up effect and the stress concentration at interface. The presence of Ti layers will lead to the cracks stagger along the inter-laminar interface or the layer due to which micro laminate expresses a good characteristic of delayed fracture. The toughening mechanisms are that the crack deflection and micro-bridge connection caused by the toughening layers increases crack propagation resistance.
1693
Authors: Zhao Hui Hu, Yi Li, Li Ma, Hong Jun Liu
Abstract: Ti-TiAl multi-layered materials have been prepared by electron beam physical vapor deposition technique. The tensile behavior of samples at room temperature and high temperature was tested, and then the deformation mechanism at different temperature was analyzed according to the fracture surface. The results show that the tensile curves hot-pressed samples have a broad step during the plastic deformation process, and the breaking strain of the sample has been increased for a wide-range. The presence of Ti layers have led to the cracks stagger along the inter-laminar interface or the layer due to which micro laminate expresses a good characteristic of delayed fracture. With the increase of temperature, the bulk modulus and yield strength of multi-layered Ti-TiAl have been increased abnormally due to the anomalous yield strengthening behavior of TiAl intermetallic.
183
Authors: Zhao Hui Hu, Rong Guo Wang, Li Ma, Shan Yi Du
Abstract: The heat convection was considered the main heat exchange type in the autoclave where CFRP pressure vessel was cured in this analysis. To determine the heat convection coefficient, it needed the combination of theoretical calculation and temperature test. In the theoretical calculation, the determination of the heat convection coefficient was considered as an inversion problem of thermal conduction. By adjusting convection coefficient value in the finite element calculation, optimization method was employed to obtain a good agreement between calculated temperature and measured temperature. In the temperature test, the metallic liner of CFRP pressure vessel was used as test component to record temperature data which was compared with the calculated temperature. The calculated results reveal that the maximum value in convection coefficient sequence is 19.87 W/m2/K; the minimum value is 0.16 W/m2/K; the maximum temperature deviation between calculation and test is 1.67 °C. The results present the equivalent thermal boundary condition for the simulation of curing process of CFRP pressure vessel.
1483
Authors: Zhao Hui Hu, Hong Jun Liu, Rong Guo Wang, Xiao Dong He, Li Ma
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.
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