Papers by Author: Qing Hua Qin

Abstract: Metallic sandwich plates have been widely used in blast-resistance structures due to the excellent capacity of energy absorption. In this work, dynamic response of square honeycomb sandwich plates is investigated using LS-DYNA. The effect of mass of TNT charge on the deformation and on internal energy of square honeycomb sandwich plate is numerically analyzed. The relationship of deflection, as well as internal energy and the mass of TNT charge is obtained. The performance of square honeycomb sandwich plate is compared with monolithic solid plate with the same mass and blast loading. During the response of sandwich plate, the deformation includes local dent of upper face sheet, overall bending and stretching of both face sheets and buckling of square honeycomb core while the deformation of monolithic solid plate is involved in overall bending and stretching. It denotes that square honeycomb sandwich plate has better capacity of resistance-deformation and energy absorption than that of monolithic solid plate with the same mass and the same blast loading.

Abstract: Structural response of pin-supported metallic foam core sandwich beam is theoretically investigated. Effects of local denting and core strength and interaction of bending and axial stretching are considered in analysis. A rigid-plastic beam-on-foundation is employed to consider local denting deformation. The local denting continues during the overall deformation of sandwich beam. It is shown that upon neglecting the effect of local denting, the load-carrying capacity and energy absorption of sandwich beam may be overestimated, and the normal axial (membrane) force associated with plastic stretching substantially stiffens the sandwich beams.

Abstract: The resistance of metallic sandwich plates to blast loading is studied in this work. Two typical cores, i.e. trapezoidal plate core and metallic foam core are considered in the analysis. The normal and longitudinal compressive stresses of the trapezoidal plate core are analytically and numerically obtained. Large deflection and resistance of metallic sandwich plates to blast loading are numerically analyzed. The results are compared with that of monolithic solid plates made of the same material and having equivalent weight. It is shown that the well-designed sandwich plates possess higher resistance to blast loading than monolithic solid plates.

Abstract: A unified yield criterion is proposed in this paper, which is valid for the metallic sandwich sections with various core strength and geometrical dimensions and can reduce to the classical yield criteria for solid monolithic section and sandwich section with weak core, respectively. Then, the unified yield criterion is used to derive the analytical solution for the large deflection of fully clamped metallic sandwich beam subject to a transversely concentrated load, in which the interaction of bending and stretching is considered. Comparisons of the present solutions with experimental results are carried out and good agreements are found. It is seen that the axial stretching induced by large deflection has a significant effect on the deflection of sandwich structure in the post-yield regime, and the load carrying capacity of metallic foam core sandwich beam may be underestimated as the core strength is neglected in analysis.

Abstract: Interference-fit fasteners are used in large numbers throughout aircraft structures. Conventional installation methods are driving fasteners into aperture using pneumatic or hydraulic tooling, installation damage always occurs using these methods. This paper introduces a new method of driving interference-fit fastener using stress wave, reports on a comparison of driving quality between stress wave driving and hydraulic force driving. The experiments completed by authors indicate that stress-wave method can drive the fasteners with larger interference which conventional installation method can not implement; stress wave driving method provides high installation quality and repeatable results compared with the conventional driving method; and stress wave driving method is convenient to be used. The experiments prove that the protuberant material produced by stress wave method is less than that of conventional installation methods, this is advantaged to improve the fatigue strength of joint.

Abstract: Homogenization is an important analysis approach of composite materials with structural hierarchy and can give the prediction of macroscopic properties of the composites. There are many homogenization theories and methods. The present paper discusses applications of some homogenization approaches including both direct and mathematical homogenizations for the analysis of anisotropic composites with periodic microstructures. The macroscopic properties of the composite are predicted by the direct homogenization and the mathematical homogenisation method. The periodic boundary conditions of a representative volume element are implemented by a transformation method of the degrees of freedom. The numerical results are demonstrated for two model composites. The study shows that these two homogenization methods gave the same results for the macroscopic elastic stiffness of the composites although they are of different mathematical forms and different operation procedures.