Papers by Author: Dai Heng Chen

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Authors: Dai Heng Chen, Kuniharu Ushijima
Authors: K. Ushijima, Dai Heng Chen, Wesley J Cantwell
Abstract: In this paper, the torsional rigidity of micro-lattice plates is investigated using a FE analysis. In particular, the effect of the overall length of the plate and the unit-cell geometry on the torsional rigidity are discussed. Also, a theoretical approach, based on classical beam theory, for predicting the rigidity is proposed, and its effectiveness is verified by comparing with FE results.
Authors: Lu Yang, Shi Min Li, Dai Heng Chen, Zhi Min Wu
Abstract: This paper bases on the prototype of the actual shed tunnel structure, study on contact force, displacement, damage, energy of shed tunnel under impact of rock-fall. By ABAQUS finite element software to simulate the process of roll-fall impact knowable: Rock-fall at different speeds and incident angle shocks on shed tunnel has great influence to concrete protective structure of contact force and displacement; Concrete protective structure damage the worst hit area of occurred with roll-fall contact area, the second is inclined leg column top and in connection with the pillars of the beam damage is also very serious, In practical projects first should pay attention to strengthen the intensity of the pillars with beam joints and prevent damage; From the angle of energy we can see that shed tunnel is mainly through the concrete protective structure to absorb and consumption impact energy, soil cushion absorption and consumption impact energy is very limited, to alleviate the impact of concrete protective layer rolling damage, and suggestions in shed tunnel bearing place additional energy shock absorber to increases protection structure system soft degrees under the condition of minimize the shed tunnel weight, achieve the purpose of decrease shock energy.
Authors: Kuniharu Ushijima, Dai Heng Chen, Wesley J. Cantwell
Abstract: In this study, a theoretical analysis for predicting the mechanical properties of three dimensional lattice structures under compressive loading is proposed, and verified by comparing the analytical predictions with FEM results. This theory for estimating the initial stiffness E* is based on the classical beam theory, and the one for estimating the plastic collapse strength reflects the stress state for each lattice structure. In particular, effects of inner geometry (strand’s diameter-to-length ratio and micro-architecture) on the mechanical behaviour are discussed.
Authors: Dai Heng Chen, Lu Yang
Abstract: In this paper, the crushing behavior of stepped circular tubes under oblique compression is studied by finite element method (FEM) analysis. It is found that the stepped circular tubes exhibit good response to oblique load. The deformation of the tubes can be classified into stable and unstable modes depending on whether break point is observed in the compressive load curve. In the stable mode, the tube stays erect and absorbs compressive energy to the same extent as it absorbs axial load. However, in the unstable mode, the tube does not stay erect and can bear only much lower compressive load than that of axial crushing. The two deformation modes can be controlled by the geometry of the tube. The compressive load of the stepped tube under oblique crushing increases as the difference between the radius of the large tube and small tube decreases and as the total length of the tube increases. For geometries that take values near the boundary between the stable and unstable modes in the mode map, the stepped tubes exhibit maximum absorption efficiency. Moreover, the absorption efficiency of stepped tubes is proportional to thickness to about the 1.8 power.
Authors: Lu Yang, Xin Pu Shen, Hong Zheng, Dai Heng Chen
Abstract: The focuses are to analyze the complicated damage process, and to determine the deformation field of the localized deformation and damage of the double notched concrete beam. Basic principle of the digital-speckle-correlate method (DSCM) was introduced. The displacement field of the beam under four-point- shear loading has been investigated with white-light speckle method, which can determined the speckle field of the surface of the deformation body rapidly and can be used to calculate the phase of deformation. Furthermore, the localized band of the deformation of the concrete can be recorded accurately. This method has shown that the procedure of experiment is convention, and can be used to determine various kind of deformation situation, including finite deformation and small deformation. Numerical calculation has been done to simulation the damage field and the whole damage field. The conclusion indicate that: compared with the localized band of the damage field and the damage process region of the experiment, damage field of the double of the notched beam from the numerical calculation can match it very well
Authors: Lu Yang, Shi Min Li, Dai Heng Chen, Zhi Min Wu
Abstract: With a rolling stone gathers tent hole structure as the prototype, using ABAQUS finite element software to simulate the rolling stones impact process with different impact, research rolling angle and speed impact tent hole structural dynamic mechanical response for rolling stone protection design, provide necessary basis. The results show that the rolling stones in different speed and incident angle of tents hole shocks on concrete protective structure of contact force ,displacement and injuries have great influence and for the rolling stones protection engineering design to provide theoretical reference.
Authors: Kuniharu Ushijima, Wesley J. Cantwell, Dai Heng Chen
Abstract: In this paper, the shear response of three-dimensional micro-lattice structures was investigated based on numerical stress analysis, FEM. The mechanical properties strongly depend on the number of unit cell in three directions x,y,z, and for a flat structure (number of cells in y-direction Ny=1), the deformation pattern observed in the structure can be classified into two types. The shear modulus G*for a flat structure obtained by FEM can be estimated by the elementary beam theory with a good accuracy. Also, for a flat structure with slender struts, the collapse is occurred by elastic buckling, and that with relatively thicker struts, the collapse strength agrees well with the theoretical result. Moreover, for the case of the cubic structure, if the structure has the same number of unit cell in x- and z- directions (numbers of cells in two directions Nx=Nz=M), the shear modulus G* shows a unit curve regardless of the number M, so that the modulus can be estimated by using the curve for various cubic structures.
Authors: Kuniharu Ushijima, Dai Heng Chen, Naoto Kitte
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