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Guo X.,State Key Laboratory of Structural Analysis for Industrial Equipment
Applied Mechanics and Materials | Year: 2012

Based on modern ideas of thermomechanics, small strain dynamic dissipation function of Hardin-Drnevich model for soils is formulated using the assumptions of the beeline and the skeleton curve shift laws. Fundamentally, for cohesionless soils, two types of cyclic strain thresholds are identified: first threshold strain and second threshold strain represent boundaries between fundamentally different dynamic characteristics of cyclic soil behavior. Comparison between the two threshold shear strain values and dynamic degradation curves obtained on exactly the same soils, the results showed that the ratio of secant modulus and maximum dynamic shear modulus for the first threshold strain are almost 1.0, and the damping ratio is almost constant. When dynamic strain level exceeds the second threshold strain, the soil behavior is considerably at nonlinear, and the primary deformation mechanism is related to fabric changes during cyclic loading. The first and the second threshold strains are therefore essential for the understanding and solving soil dynamic problems. © (2012) Trans Tech Publications.

Guo T.,Shenyang Blower Works | Wang Y.-F.,Shenyang Blower Works | Wang Y.-F.,Dalian University of Technology | Wang Y.-F.,State Key Laboratory of Structural Analysis for Industrial Equipment
Gongcheng Lixue/Engineering Mechanics | Year: 2011

Beetles cuticles have delicate and complicated body structures. In this paper several models are developed based on the observation of microstructures of beetle cuticles. The analysis for capability of energy-absorbing of beetle cuticles are presented with the nonlinear finite element software ANSYS/LS-DYNA. The discussions on effects of structures and materials are provided. The structures of original models are improved to make them resemble the trabecular structure of beetle cuticles for larger energy absorptions. A comparison is carried out between the improved model and cylindrical tube in terms of static and dynamic axial impact responses. The results show that the improved model absorbs more energy and performs in more stability way than the tube. This makes it an excellent structure for the device of structural crashworthy and energy absorption.

Xue Q.-W.,Dalian Jiaotong University | Xue Q.-W.,State Key Laboratory of Structural Analysis for Industrial Equipment | Wei W.,Dalian Jiaotong University
Gongcheng Lixue/Engineering Mechanics | Year: 2010

Tikhonov's regularization approach has been used to solve non-linear inverse heat conduction problems, using weighted Bregman distances in the construction of regularization terms for the Tikhonov's function. Combined identifications can be achieved for non-linear inverse heat conduction with source term, thermal diffusivity and boundary conditions etc, facilitating the sensitivity analysis. Satisfactory numerical validation is performed including a preliminary investigation on the effect of noise data and the computational efficiency of different regularization terms. Results show that the proposed method can identify combined thermal parameters and boundary conditions for non-linear inverse heat conduction problems with high computational precision and anti-noisy capability. Moreover, the computational efficiency is improved with the weighted Bregman distances function as regularization terms.

Zhang H.W.,State Key Laboratory of Structural Analysis for Industrial Equipment | Fu Z.D.,State Key Laboratory of Structural Analysis for Industrial Equipment
Advances in Water Resources | Year: 2010

The coupling upscaling finite element method is developed for solving the coupling problems of deformation and consolidation of heterogeneous saturated porous media under external loading conditions. The method couples two kinds of fully developed methodologies together, i.e., the numerical techniques developed for calculating the apparent and effective physical properties of the heterogeneous media and the upscaling techniques developed for simulating the fluid flow and mass transport properties in heterogeneous porous media. Equivalent permeability tensors and equivalent elastic modulus tensors are calculated for every coarse grid block in the coarse-scale model of the heterogeneous saturated porous media. Moreover, an oversampling technique is introduced to improve the calculation accuracy of the equivalent elastic modulus tensors. A numerical integration process is performed over the fine mesh within every coarse grid element to capture the small scale information induced by non-uniform scalar field properties such as density, compressibility, etc. Numerical experiments are carried out to examine the accuracy of the developed method. It shows that the numerical results obtained by the coupling upscaling finite element method on the coarse-scale models fit fairly well with the reference solutions obtained by traditional finite element method on the fine-scale models. Moreover, this method gets more accurate coarse-scale results than the previously developed coupling multiscale finite element method for solving this kind of coupling problems though it cannot recover the fine-scale solutions. At the same time, the method developed reduces dramatically the computing effort in both CPU time and memory for solving the transient problems, and therefore more large and computational-demanding coupling problems can be solved by computers. © 2009 Elsevier Ltd. All rights reserved.

Wang Y.-F.,Dalian University of Technology | Wang Y.-F.,State Key Laboratory of Structural Analysis for Industrial Equipment | Zhao G.-X.,Dalian University of Technology | Zhao G.-X.,State Key Laboratory of Structural Analysis for Industrial Equipment
Gongcheng Lixue/Engineering Mechanics | Year: 2012

The dynamic behavior of an ice-covered cable is complicated because of the eccentricity over the cable's cross-section, which makes the in-plane and out-of-plane vibrations coupled with the torsion vibration. A three-dimensional coupling model of a suspension cable loaded by wind excitation is developed, with the wind force expressed as a nonlinear function of the angle of attack. The governing partial differential equation of motion is derived through the Hamilton's principle and discretized using the Galerkin approach. The stability region in the parametric space of the cable's equilibrium configuration is obtained using Routh-Hurwitz criterion. The critical wind speed of the Hopf bifurcation is determined and later verified numerically. The boundary shape of the stability region is obtained through an approximately analytical method in the vicinity of a given Hopf bifurcation point, by which a fair amount of computational cost is saved.

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