Papers by Keyword: Nonlinear Finite Element Method

Abstract: By using beam element to model rail, spring element to model fastener, solid element to model different components of ballastless track, contact element to model the connection between each component of ballastless track, a statics three-dimensional nonlinear finite element mechanical model for calculating the forces transmission among rail, fastening and different component of ballastless slab track on subgrade was established. Experimental data of Suining-Chongqing railway line was given to validate the calculation model. Force of ballastless slab track on subgrade under gravity load, train load, uneven settlement load, temperature gradient load as well as combined load was analyzed. Results show that: spatial forces characteristic of ballastless slab track is very notable under train load; uneven settlement load as well as temperature gradient load has significant influence on the mechanical characteristic of ballastless slab track; force of ballastless slab track increases significantly under combined load than that of under any single load.

Abstract: An efficient 3D incompatible element for the simulation of Flexible Multibody System (FMBS) is derived based on the principle of virtual work and the theory of continuum mechanics. The presented incompatible element uses absolute coordinates and internal parameters for the degrees of freedom and fixed the locking problem under the state of pure bending. Considering the geometric nonlinearities and using the Total Lagrangian Formulation, system dynamic equations are derived and then solved by the Backward Difference Formula (BDF) in conjunction with Newton-Raphson algorithm. Eigenvalue analysis and dynamic analysis of several numerical examples are presented to show the convergence of the 3D incompatible element and excellent performance in terms of accuracy and time efficiency comparing with standard linear and quadratic hexahedral elements.

Abstract: Nonlinear finite element model is established for the square interior constrained concrete filled steel tube column based on the research of the element type and material constitutive relation with finite element software ANSYS to find out the influence of the thickness of the steel tube, location of studs and geometry of the stirrups on the compression capacity of the short column, The results show that the compression capacity of the short column has something to do with the thickness of the steel tube and the studs, but the stirrups can eventually enhance a lot for the compression capacity as the validity is confirmed for the coherence of the results stepped from the finite element model and in test.

Abstract: The deep anti-sliding stability of dam foundation has been an important issue in the study of dam field. Rigid body limit equilibrium method and nonlinear finite element method have been adopted on the analysis of sliding stability. In the current paper, the joint element is used to simulate faults, interlayer shear zone and slight inclined fissure zone in complicated geological conditions of Wudu dam. Stress integral method, overload method and strength reduction method are utilized for analysis on deep anti-sliding of Wudu RCC gravity dam, moreover, after being compared with the results by Sarma method, finite element direct force method and geomechanical model test method etc., the consistent conclusion is obtained.

Abstract: The rub-impact fault of Jeffcott rotor system which is generally made of an elastic shaft with supported by two bearings at ends and a lumped mass at the mid-span of shaft is the main research subject of this paper. The mechanical model and finite element model of a lump mass at the mid-span of shaft is set up. The dynamics of it are studied by nonlinear finite element method under the rub-impact conditions, and by investigating the effects of stiffness of stator and the clearance between rotor-stator. From the study results, use finite element method to study the rotor system failure problem is intuitive and convenient, high accuracy, high reliability, can be widely applied.

Abstract: Understanding the mechanism of the forming of the welded pipe may help the engineer to design the shape of forming rollers and forming technology. It is hard to study the forming process of the welded pipe by both the method of experiment and numerical modeling because of too much nonlinear factors included in the forming process such as elastic-plastic large deformation and non linear contact. Although many research works have been conducted in this field by the method of experiment or numerical modeling, but few of the works deal with the whole forming process of the welded pipe. The main difficulties in the numerical modeling are of huge computational labor time, witch has been over the ability of the hardware and software of the computer. The whole process of roll forming of welded pipe has been simulated by nonlinear finite element method with ANSYS and LS-DYNA solver, the distribution of both stresses and strains have been got successfully. Mapping meshes and the rigid models for rollers have been used in the analysis in order to decrease the number of the elements. Numerical results and parameter study have shown that the forming rollers of both the level and vertical are the key factors to the forming process. It is believe that the method used in the paper can also be used to study the forming process of both cage roll forming and flexible forming.

Abstract: Based on numerical simulation of the seepage field of earth rockfill cofferdam using nonlinear Finite Element Method under the action of flood during construction period, the stability of the cofferdam slope with nonlinear shear strength is studied. The effectiveness and applicability of the method introduced in the paper is certified through computation in the study on the practical project. The paper provides an effective analysis method for the study on the stability of dam slope of earth rockfill cofferdam.

Abstract: In combination with the practice of a pumped storage hydropower station, a 3-D nonlinear finite element method on the preloading filling spiral case is carried out to compare and analyze stresses of the steel spiral case and hoop reinforcement, the stress and bearing ratio of the surrounding concrete, the contact state between the spiral case and concrete in different precast water head. The results indicate that the stress of the surrounding concrete will get better with the increasing of precast water head. But there is a distance between the spiral case and the surrounding concrete when the water head is excessive, which is unhelpful for operating of the unit. When the precast water head of the spiral case is 439m or so, it can play a greater degree of mechanical characteristics of steel and concrete under the premise of operating stably of the unit.

Abstract: Concrete casting effect and the hooping effect of concrete filled tubular members is considered in the study of this paper. Firstly, standard stress-strain relationship of concrete and steel is chosen to simulate others’ test, and meanwhile the calculation results by nonlinear finite element analysis are compared with the results of the test. Then the bearing capacity of horizontally casted concrete filled steel tubular members under axial compression is contrasted among different construction processes. Finally, the effect of slenderness ratio of concrete filled tubular members is studied so as to reveal the relationship between the bearing capacity and slenderness ratio.

Abstract: The pile ground heat exchanger is devised to overcome the shortcomings in configuration of existing ground heat exchangers. In view of its engineering applications of the spiral tubes ground heat exchanger inside foundation piles, the effects of them on the loading capacity features of the pile are studied. Firstly, a spiral tube model is proposed for the energy pile system and the model is proved correctly compared with engineering practice of the piles.Then，in the FEM software the model is applied in the comparasion between the piles with and without buried tubes .As a result, the effects of buried tubes on the loading capacity features of the piles are found.