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Fracture analysis of rock mass based on 3-D nonlinear finite element method

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Science China(Technological Sciences) 2011年第3期54卷 556-564页

作者： LIU YaoRu CHANG Qiang YANG Qiang WANG ChuanQi GUAN FuHai State Key Laboratory of Hydroscience and Hydraulic Engineering Tsinghua University Beijing 100084 China

Traditional fracture analysis is based on fracture mechanics and damage mechanics. They focus on the propagation of the fracture. However, their propagation criterions are not easily applied in practice and the current analysis is limited in planar problem. This paper presents a new theory that the occurrence of the unbalanced force (derived from the Deformation Reinforcement Theory) could be the criterion of the initiation of the fracture, and the distribution area and propagation of the unbalanced force could be the indication of the fracture propagation direction. By aggregate analysis with Stress Intensity Factor (SIF) criterion, the unbalanced force actually is the opposite external load that is the SIF difference incurred between the external loads and permitted by the structure. Numerical simulation and physical experiments on pre-fracture cuboid rock specimens proved that the occurrence of the unbalanced force could be the initiation of the fracture. Mesh size dependence was also considered by analysis of different mesh size finite element gravity dam models. Furthermore, the theory was applied to the feasibility analysis of the Baihetan arch dam together with physical experiments in order to evaluate the fracture propagation of dam heel. The results show that it is an effective way to use unbalanced force to analyze the fracture initiation and propagation when performing 3-dimensional nonlinear FEM calculation.

关键词： fracture analysis rock mass unbalanced force plastic complementary energy norm nonlinear finite element method

裂纹加筋和缺口加筋对钢加筋板极限强度的影响

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哈尔滨工程大学学报（英文版） 2024年第2期23卷 460-469页

作者： Musa Bahmani Fattaneh Morshedsolouk Mohammad Reza Khedmati Babol Noshirvani University of Technology Mechanical Engineering FacultyBabolIran Amirkabir University of Technology Department of Maritime EngineeringTehranIran

This paper numerically evaluates the effect of the crack position on the ultimate strength of stiffened *** such as notches and cracks in aged marine stiffened panels can reduce their ultimate *** investigate the effect of crack length and position,a series of nonlinear finite element analyses were carried out and two cases were considered,i.e.,case 1 with thin stiffeners and case 2 with thick *** both cases,the stiffeners have the same cross-section *** have a basis for comparison,the intact panels were modeled as *** cracks and notches were in the longitudinal and transverse direction and were assumed to be in the middle part of the *** cracks and notches were assumed to be through the thickness and there is neither crack propagation nor contact between crack *** on the numerical results,longitudinal cracks affect the behavior of the stiffened panels in the postbuckling *** the stiffeners are thinner,they buckle first and provide no reserved strength after plate ***,cracks in the stiffeners do not affect the ultimate strength in the case of the thinner ***,when stiffeners are thicker,they affect the postbuckling behavior *** that case,cracks in the stiffeners affect the buckling and failure modes of the stiffened *** effect of notch was also *** contrast to the longitudinal crack in stiffeners,a notch in the stiffeners reduces the ultimate strength of the stiffened panel for both slender and thick stiffeners.

关键词： Stiffened panels Crack Notch Ultimate strength Buckling nonlinear finite element method

Characteristic Verification and Parameter Optimization of Airbags Cushion System for Airborne Vehicle

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Chinese Journal of Mechanical Engineering 2014年第1期27卷 50-57页

作者： WANG Hongyan HONG Huangjie HAO Guixiang DENG Huaxia RUI Qiang LI Jianyang Department of Mechanical Engineering Academy of Armored Force Engineering School of Instrument Science and Opto-electronics Engineering Hefei University of Technology

Abstract： The major methods to investigate the airbags cushion system are experimental method, thermodynamic method and finite element method （FEM）. Airbags cushion systems are very complicated and very difficult to be investigated thoroughly by such methods For experimental method, it is nearly impossible to completely analyze and optimize the cushion characteristics of airbags of airborne vehicle because of charge issue, safety concern and time constraint. Thermodynamic method fails to take the non-linear effects of large airbag deformation and varied contact conditions into consideration. For finite element method, the FE model is usually complicated and the calculation takes tens of hours of CPU time. As a result, the optimization of the design based on a nonlinear model is very difficult by traditional iterative approach method. In this paper, a model based on FEM and control volume method is proposed to simulate landing cushion process of airborne vehicle with airbags cushion system in order to analyze and optimize the parameters in airbags cushion system. At first, the performance of airbags cushion system model is verified experimentally. In airdrop test, accelerometers are fixed in 4 test points distributed over engine mount, top, bottom and side armor plate of hull to obtain acceleration curves with time. The simulation results are obtained under the same conditions of the airdrop test and the simulation results agree very well with the experimental results, which indicate the established model is valid for further optimization. To optimize the parameters of airbags, equivalent response model based on Latin Hypercube DOE and radial basis function is employed instead of the complex finite element model. Then the optimal results based on equivalent response model are obtained using simulated annealing algorithm. After optimization, the maximal acceleration of airborne vehicle landing reduces 19.83%, while the energy absorption by airbags increases 7.85%. The

关键词： airborne vehicle airbag nonlinear finite element method verification equivalent response model

Performance index limits of high reinforced concrete shear wall components

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Journal of Central South University 2011年第4期18卷 1248-1255页

作者：劳晓春韩小雷 School of Civil Engineering and Transportation South China University of Technology State Key Laboratory of Subtropical Architecture Science South China University of Technology

The deformation performance index limits of high reinforced concrete （RC） shear wall components based on Chinese codes were discussed by the nonlinear finite element method. Two typical RC shear wall specimens in the previous work were first used to verify the correctness of the nonlinear finite element method. Then, the nonlinear finite element method was applied to study the deformability of a set of high RC shear wall components designed according to current Chinese codes and with shear span ratio λ≥2.0. Parametric studies were made on the influence of shear span ratio, axial compression ratio, ratio of flexural capacity to shear capacity and main flexural reinforcement ratio of confined botmdary members. Finally, the deformation performance index and its limits of high RC shear wall components under severe earthquakes were proposed by the finite element model results, which offers a reference in determining the performance status of RC shear wall components designed based on Chinese codes.

关键词： reinforced concrete shear wall components performance index limits nonlinear finite element method Chinese codes

nonlinear static response of piezoelectric plates considering electro-mechanical coupling

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Journal of Central South University 2012年第5期19卷 1182-1188页

作者： B.Behjat M.R.Khoshravan Mechanical Engineering Department Tabriz UniversityTabrizIran

nonlinear static analysis of piezoelectric plates has been carried out using nonlinear finite element method considering electro-mechanical coupling,The geometrical nonlinearity has been taken into account and electric potential is assumed to be quadratic across the plate thickness,The governing equations are obtained using potential energy and Hamilton's principle that includes elastic and piezoelectric *** finite element model is derived based on constitutive equation of piezoelectric material accounting for coupling between elasticity and electric effect using higher order plate elements,Results are presented for piezoelectric plate under different mechanical boundary conditions,Numerical results for the plate are given in dimensionless graphical *** of boundary conditions on linear and nonlinear response of the plate are also *** numerical results obtained by the present model are in good agreement with the available solutions reported in the literature.

关键词： piezoelectric plate nonlinear finite element method static analysis of plate geometrical nonlinearity

ANALYSIS OF DAMAGE NEAR A CONDUCTING CRACK IN A PIEZOELECTRIC CERAMIC

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Acta Mechanica Solida Sinica 2003年第2期16卷 147-154页

作者： YangXinhua ChenChuanyao HuYuantai DepartmentofMechanics HuazhongUniversityofScienceandTechnologyWuhan430074China StateKeyLaboratoryofStructuralAnalysisofIndustrialEquipment DalianUniversityofTechnologyDalian116023China

The finite element formulation for analyzing static damage near a conducting crack in a thin piezoelectric plate is established from the virtual work principle of *** damage fields under various mechanical and electrical loads are calculated carefully by using an effective iterative *** numerical results show that all the damage fields around a crack tip are fan-shaped and the electric field applied has great influence on the mechanical damage, which is related to the piezoelectric properties.

关键词： piezoelectric ceramic nonlinear finite element method conducting crack mechanical and electrical damage

finite element Analysis on Plane Stress Crack Growth in a Power-Law Hardening Material

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Journal of Beijing Institute of Technology 1998年第3期7卷 247-251页

作者：吴祥法范天佑北京理工大学材料科学研究中心北京100081

Aim To determine numerically the field characteristics in the vied at the tip of a place crack growing steadily in a power-law hardening material. Meteods. methods on the Euler mode and small-scale yield assumption, the numerical results were given by nonlinear finite element analysis. Results The numerical results of the shape of the active plastic sone, the angular distribution of stresseses and Clack tip opening displacement (CTOD) in the vicinity at the hp of the steadily groWing CraCk are determined. Conclusion The comparison between the numerical results given by the present wort and those given by analytic asymptotic analysis shows that the present work reached a very high accuracy.

关键词： plane stress crack growth steadily power-law hardening material asymptotic fields nonlinear finite element method

finite element analyses of Wanjiazhai water transmission tunnel excavation and service

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Journal of Southeast University(English Edition) 2003年第4期19卷 387-391页

作者：王协群王钊黄杰王俊奇武汉理工大学土木工程与建筑学院武汉430070 武汉大学土木建筑工程学院武汉430072

This paper is devoted to the nonlinear stress and strain analysis oftunneling and working conditions of Wanjiazhai Division Project No.7 Tunnel in Shanxi province ofChina. The initial geological stress of loess was simulated by grading fill; the theory of unloadingproposed by Duncan and boundary stress of elasticity were used to calculate the excavation of thetunnel; Goodman joint elements were applied to simulate the joints of the liners; both loading andunloading tests have been performed to determine the parameters of Duncan-Chang's model and thecalculated results were compared; Terzaghi' s theory on loosening earth pressure was applied. Manyworking conditions were analyzed and some reasonable results were obtained. Based on the analyses,reparative measures were proposed and completed. The tunnel has functioned well since October, 2001.

关键词： tunnel loess nonlinear finite element method loading and unloading test loosening earth pressure stress strain