Papers by Keyword: Nonlinear Finite Element Method

Abstract: In wall-column structural system of electrostatic precipitator casing, wall will share the load with column and provide lateral bracing support when the load is applied on the column .Then the wall panel exert the stressed skin effect, which will influence its load bearing capacity. By nonlinear finite element method, when wall panel exerts stressed skin effect, whether the effect will influence the wall bearing capacity is investigated as well as the failure mode. The relationship is analyzed between the loading level onto column, panel thickness, loading form onto wall and the affecting degree on the bearing capacity of wall panel. The computation results indicate that the bearing capacity of wall panel is lower when it exerts the stressed skin effect. When the wall is thin, the weakening degree of panel bearing capacity resulting from stressed skin effect is slightly affected by loading level onto column. When the wall is thicker, the weakening degree of panel bearing capacity increases apparently as the loading level onto column increases. For a certain loading level onto column, compared with the locally loaded wall panel, the impact on load bearing capacity is greater for the globally loaded wall panel. Research work has reference value for the calculation and design of enclosure structures of electrostatic precipitator casing.

Abstract: Air spring is used for the suspension system and it affects the vehicle stability and riding comfort by improving the impact-relief, braking, and cornering performance. Air Spring is comprised of the upper plate, lower plate, and rubber sleeve. Rubber sleeve is the composite material, which is made up of combination of rubber and Nylon, and the characteristics are changed according to the shape of rubber-sleeve, the angle of reinforcement cord. In this study, the distribution of internal stresses and the deformation of rubber composite material are analyzed through the nonlinear finite element method. The result showed that the internal maximum stresses and deformations about the changes of cord angle caused the more the Young's modulus decrease, the more maximum stress reduced.

Abstract: The conventional solution strategy for nonlinear FEM of structural analysis is usually based on Newton-Raphson iteration under an additional constraint equation. So far a lot of nonlinear finite element solution procedures have been devised to provide the basis for most nonlinear finite element computer programs. In order to produce effective, robust solution algorithms, additional constraint equations for nonlinear FEM calculations in the load-displacement space of has been extensively investigated for the last a few decades. However, it is widely believed that due to the additional computations in the controlling of steps and directions of the iteration procedure, there will be more round-off errors accumulated to influence the convergence of solution. In this work, a more simplified solution procedure is presented, which is featured to be with neither iterations nor constraints. A Fortran computer program of the algorithm presented has been implemented in combining with a space truss element of co-rotational procedure. Verification of the procedure has been done by numerical example and a good result achieved.

Abstract: The brace at the mid-span of beam of portal frame provides lateral constraint and improves its overall stability. By the nonlinear finite element method, the influences of structural parameters on the required bracing force for the beam bearing ultimate load were investigated when only one brace acting on the upper flange of beam at mid-span. The bracing force is correlated to the failure mode and configuration of beam of portal frame. The failure of beam trends to be controlled by the strength and the required bracing force increases when the stiffness of column increases. The required bracing force corresponding to the beam subjected to the ultimate load increases when the span of beam or the width of beam flange increases. The research work can be used as reference for the brace design for beam of portal frame.

Abstract: The submarine geology characteristic for Qingdao submarine tunnel is fracture and fragmentation with smash rock mass and unevenly distributed rock mass strength. The submarine tunnel is excavated in a weathered rock mass containing water. Before the tunnel lining is constructed, it is important to assure the stability and safety for the rock tunnel and tunnel lining structure during construction and operational periods. As the submarine tunnel is under severe condition, the rock mass stabilization is to a large extent to be determined by the underwater seepage effect. It is fundamental to investigate how the seawater interacts with the tunnel rock mass stress field. To investigate the interaction between the rock mass seepage field and the secondary stress field, the nonlinear finite element software ABAQUS is used to analyze the interaction behavior between the rock mass seepage effect and the tunnel secondary stress field. The rock mass seepage field, stress field are analyzed in detail using the numerical simulation method. Also, the distribution of the tunnel rock mass plastic region is obtained. The numerical analysis results provide guidance for the submarine tunnel construction.

Abstract: Three-dimensional dynamic fracture process of rock under action of disc cutter is simulated by using nonlinear finite element method. Rock constitutive relationship is characterized by Drucker-Prager model. The influences of disc angular velocity and vertical force on the penetration depth and the specific energy are systematically investigated. The simulation results show that the rock fracturing process obviously presents properties of step crushing under action of disc cutter. The proposed numerical simulation presents an improvement on existing ones in terms of providing three-dimensional visual description of rock fracturing process.

Abstract: A rubber isolator which is used to connect two plates is designed. Based on the Mooney-Rivlin model, the static characteristics of the rubber are studied experimetally to obtain the model's parameters.According to operational requirements,the basic parameters and the basic dimensions are designed ,and then an optimization algorithm is adopted for the detailing of the rubber isolator, in which the dimensions of the isolator,the preload,the distance between the two plates and the maximum stress are considered as the design variables, and the stiffness is considered as the objective function.In the condition of satisfying the vibration-isolation effect, the numerical calculation is made by the nonlinear finite element method, and the rubber isolator is designed successfully.

Abstract: The method combining the construction survey and the numerical simulation is proposed in the paper to accurately obtain the deformation of the slurry shield construction under across and parallel existing tunnel. The surface settlements of the engineering construction initial position are surveyed. The reliability of the three dimensional finite element models is verified by comparing with the survey results. The deformation variation of the existing tunnel and ground surface are obtained by the elastoplasticity nonlinear calculations, showing the feasibility and effectiveness of the proposed method and the credibility and accuracy of the calculated results. Meanwhile, the measures of control deformation are presented. The surveyed settlements after the construction process of implementing measures are smaller than those calculated, indicating the effect obviously of the measures which has practical significance.

Abstract: The design and analysis of the large span steel latticed shell structure in site of Yuyao TianLuoshan is introduced, and some key problems are dwelled on in this paper. By the geometrical nonlinear finite element method, the nonlinear stability analysis is carried out. The buckling modal and the whole course of instability are shown by two analysis method, the eigen-buckling analysis and the geometrical nonlinear finite element method. The influence of spring support to the stability of the structure is analyzed. It is shown that the structure has good wind-resisting capacity, which is fit to the circumstance near sea with lots of typhoon. Large compressive membrane stresses arise in the structure under the condition of temperature rise, leading to a significant reduction in the stability load-carrying capacity of the structure.

Abstract: The theories of rock and soil mechanics and nonlinear finite element method were introduced to casing damage analysis, the physical models of casing damage were established, the relation between the water injection pressure and strata dislocation was investigated, also the influence of fault was considered. The results based on the nonlinear finite element method show that the water injection pressure is the direct cause of strata dislocation. The fault has significant influence to strata dislocation. When the fault exists, even the natural pressure of water injection may cause considerable local strata dislocation. The high pressure of water injection will not produce strata dislocation at the absence of faults. The casing damage near the fault is probably caused by strata dislocation, but the casing damage far from the fault may be considered causing by other factors. The present method offers theoretical reference for taking measures scientifically to prevent and control casing damage, and also offers a new idea for casing damage analysis.