Papers by Author: Zheng Zhong

Abstract: A new differential quadrature element model is presented for the second-order elasto-plastic analysis of frames in this study. The new model is based on the differential quadrature method (DQM) and the finite-cut technique. Firstly the basic equilibrium differential equations of members, the compatibility conditions of joints and the equilibrium equations of joints for the second-order analysis of frames are established. The differential quadrature method is used to discretize the basic equations and then the stiffness equations of the whole structure can be derived. While the corresponding boundary conditions are considered, the mechanical behavior of frames can be obtained. The yielding development along the axis of the member can be taken into consideration by selecting several discrete points and simultaneously the yielding development across the section can be considered using the layered approach. The full historical second-order elasto-plastic analysis is achieved by the incremental iterative algorithm. According to the new model derived in this paper, the interrelated structural calculating program is worked out. The results of numerical examples demonstrate the validity of the differential quadrature element model (DQEM). The new model can be used in the second-order elasto-plastic analysis of arbitrary frames.

Abstract: Recent uniaxial tension tests have shown that stress-induced phase transformation in NiTi SMAs tubes can lead to helical-type localized deformation and propagation phenomena. Based on detailed experimental observation and possible deformation mechanism, a trilinear stress-strain relationship with intrinsic strain softening is employed to represent the material constitutive behavior in this paper, and a 3-D finite deformation simulation is performed to model the tube under tension by using nonlinear FEM. The simulations successfully reproduce the nucleation and evolution of the helical-type martensite band during stress-induced transformation observed in the experiments.

Abstract: A new elasto-plastic and geometrically nonlinear finite element model of space beam considering restraint torsion and the coupling effect of deformations is presented in this paper. The warping restraint torsion and the coupling effect of deformation are considered in the displacement formulation of arbitrary point on the space beam. The geometrical relationship of arbitrary point is derived according to the definition of Green strain. The elasto-plastic and geometrically nonlinear finite element model of space beam is derived using Updated Lagrange description. The effect of axial force, shearing force, biaxial bending moment, moment of torsion and bimoment is involved in the geometrical stiffness matrix of element. The yielding developments both across the section and along the axis of the member are taken into consideration by selecting Gauss points. The full historical nonlinear analysis is achieved using the method of load increment and modified Newton-Raphson method. The validity of the new model derived in this paper is proved by numerical example. This new model can be used in the elasto-plastic and geometrically nonlinear analysis of space beam structures constructed by the members of arbitrary cross section.