Papers by Author: Hui Jian Li

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Authors: Bai Feng Gao, Hui Jian Li, Li Xin Zhang
Abstract: We describe the design and construction about the Ultrasonic method to determine the defects in concrete structure. The wave velocity and its energy are different when it transfers in the concrete material with various defects. The defects can then be detected according to the relative wave velocity and energy variations in concrete material. In the present paper, two methods contain both the wavelet analysis and the nerve network used to determine the relative wave energy change in concrete, and then we will evaluate the defects in material by energy change. The result shows that the present method can give an accurate measurement for the defects in concrete structure.
297
Authors: Han Zhao, I. Elnasri, Hui Jian Li
Abstract: This paper presents a study of the strength enhancement under impact loading of metallic cellular materials as well as sandwich panels with cellular core. It begins with a review of likely causes responsible for the strength enhancement of cellular materials. A testing method using 60mm diameter Nylon Hopkinson pressure bars is used to investigate the rate sensitivity of various metallic cellular materials. In order to identify the factor responsible for the strength enhancement of those materials, an experimental analysis is performed on a model structure which is a square tube made of rate insensitive materials. Significant enhancement is experimentally observed under impact loading, whereas the crushing mode is nearly the same under both static and impact loading. Finally, an inversed perforation test on sandwich panels with an instrumented pressure bar is also presented. Such a new testing setup provides piercing force time history measurement, generally inaccessible. Testing results show a notable enhancement of piercing forces, even though the skin aluminum plates and the foam cores are nearly rate insensitive.
1880
Authors: Chang Jun He, Hui Jian Li, Wei Yu, Xi Liang, Hai Yan Peng
Abstract: . The Young’s modulus of syntactic foams were studied both the experiment and the theory. The compressive test and dynamic mechanical analysis were progressed for a few of specimens, which were made of the syntactic foams with the epoxy resin and hollow glass microspheres (HGMs). the equations for Young’s modulus of concentrated particulate composites were derived using a differential scheme of an infinitely dilute system, and were employed to prediction the Young’s modulus of syntactic foams. The computed effective Young’s moduli were compared with the experimental results, the prediction values were between the lower and upper bounds of the experimental data, and the prediction model was acceptable and can estimate the Young’s modulus of syntactic foams.
607
Authors: Wei Yu, Hui Jian Li, Chang Jun He, Xi Liang
Abstract: . Metallic hollow sphere (MHS) material is a new type of cellular material characterized by super-light, high specific stiffness and strength, the ability to absorb noise and energy, thermal insulation. It had been widely used in engineering, i.e. automobile, aircraft, civil and military. The basic unit of MHS cellular material was small metallic hollow sphere in macro, and the instability of sphere shell is always the most difficult problem in mechanical field. In this paper, we explored the internal factors and the principle of this phenomenon though the methods of theoretical and experimental. The equation of deformation of MHS was derived. It had shown that the nominal strain was related to the radius of the shell and loads, and the nominal stress was connected with the radius, load and the thickness of shell wall. A series of quasi-static uniaxial compression tests were progressed for a group of single MHSs, which radii were 4mm, 5mm and 7mm. It was found that the deformation planes are circle and symmetry both top and bottom, and the curves of nominal stress-strain were similar to a half parabola. There was a perfectly uniformity of the theoretical model and the experimental results.
613
Authors: Han Zhao, I. Nasri, Hui Jian Li
Abstract: This paper presents a experimental study of the strength enhancement under impact loading of metallic cellular materials as well as sandwich panels with cellular core. A testing method using 60mm diameter Nylon Hopkinson pressure bars is used to investigate the rate sensitivity of various metallic cellular materials as honeycombs, foams. Finally, an inversed perforation test on sandwich panels with an instrumented pressure bar is also presented. Such a new testing setup provides piercing force time history measurement, generally inaccessible. Testing results show a notable enhancement of piercing forces, even though the skin aluminum plates and the foam cores are nearly rate insensitive.
1137
Authors: Xiao Man Liu, Chang Jun He, Hui Jian Li, Hai Yan Peng
Abstract: The durability is very important in the research and application of polymers and their composites under different environmental conditions. The study of durability of patical filled epoxy resins had absorpted more attension in recently years, and the study of moisture absorption or water diffusion was almost along with the material manufacture. In the present work, the water sorption behavior in a series of different content hollow particle filled syntactic foams was studied by gravimetric measurements. The fashion factors on water sorption were discussed, and the change of density of syntactic foams on the subject was put forward.
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