Use of Finite Element and Finite Segment Methods in Modeling Rail Flexibility: A Comparative Study

2012 ◽  
Vol 7 (4) ◽  
Author(s):  
Martin B. Hamper ◽  
Antonio M. Recuero ◽  
José L. Escalona ◽  
Ahmed A. Shabana
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Element Mesh ◽  
Finite Segment ◽  
Safety Requirements ◽  
Contact Points ◽  
Rigid Finite Element Method ◽  
Contact Formulation ◽  
Finite Segment Method ◽  
Railroad Vehicle

Safety requirements and optimal performance of railroad vehicle systems require the use of multibody system (MBS) dynamics formulations that allow for modeling flexible bodies. This investigation will present three methods suited for the study of flexible track models while conclusions about their implementations and features are made. The first method is based on the floating frame of reference (FFR) formulation which allows for the use of a detailed finite element mesh with the component mode synthesis technique in order to obtain a reduced order model. In the second method, the flexible body is modeled as a finite number of rigid elements that are connected by springs and dampers. This method, called finite segment method (FSM) or rigid finite element method, requires the use of rigid MBS formulations only. In the third method, the FFR formulation is used to obtain a model that is equivalent to the FSM model by assuming that the rail segments are very stiff, thereby allowing the exclusion of the high frequency modes associated with the rail deformations. This FFR/FS model demonstrates that some rail movement scenarios such as gauge widening can be captured using the finite element FFR formulation. The three procedures FFR, FSM, and FFR/FS will be compared in order to establish differences among them and analyze the specific application of the FSM to modeling track flexibility. Convergence of the methods is analyzed. The three methods proposed in this investigation for modeling the movement of three-dimensional tracks are used with a three-dimensional elastic wheel/rail contact formulation that predicts contact points online and allows for updating the creepages to account for the rail deformations. Several conclusions will be drawn in view of the results obtained in this investigation.

Modeling Rail Flexibility Using Finite Element and Finite Segment Methods

2011 ◽  
Author(s):  
Martin B. Hamper ◽  
Antonio M. Recuero ◽  
Jose´ L. Escalona ◽  
Ahmed A. Shabana
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Low Frequency ◽  
Mode Shapes ◽  
Finite Segment ◽  
Safety Requirements ◽  
Contact Points ◽  
Contact Formulation ◽  
Modes Of Vibration ◽  
Floating Frame

Safety requirements and optimal performance of railroad systems require the utilization of multibody System (MBS) formulations that allow for modeling flexible bodies. This investigation will present three methods suited for the study of flexible track models while conclusions about their implementations and features are made. A validated method combining Floating Frame of Reference (FFR) and Finite Element (FE) to model flexible rails is utilized for comparison. In this procedure, component mode synthesis is used to extract a number of low-frequency modes of vibration which describe the deformation of the rail. Likewise, a method that discretizes the flexible body as a finite number of rigid elements that are linked by springs and dampers is applied for railroad simulations. This method, called Finite Segment or Rigid Finite Element (FS), can in turn be combined with FFR through the extraction of mode shapes of the FS model. Convergence of the methods is analyzed. A comparison will be made between these three procedures establishing differences among them and analyzing the specific application of FS to modeling track flexibility. The three aforementioned procedures may be applied to three-dimensional track models and will be used together with three-dimensional wheel/rail contact formulation that predicts contact points online and allows for updating the creepages to account for the rail movements and deformations. Several comparisons and conclusions will be drawn in view of the results obtained in this investigation.

Analysis of Tank Car Deformations Using Multibody Systems and Finite Element Algorithms

2015 ◽  
Author(s):  
Liang Wang ◽  
Huailong Shi ◽  
Ahmed A. Shabana
Keyword(s):  
Finite Element ◽  
Plate Thickness ◽  
Three Dimensional ◽  
Shell Element ◽  
Element Model ◽  
Railroad Vehicles ◽  
Contact Formulation ◽  
Triangular Shell Element ◽  
Railroad Vehicle ◽  
Strong Dynamic

This investigation demonstrates the effect of the tank flexibility and plate thickness on the wheel/rail contact and the nonlinear dynamic behavior of railroad vehicles. To this end, a flexible tank is modeled using the finite element (FE) floating frame of reference formulation (FFR). The tank car finite element model is integrated with a three-dimensional railroad vehicle using computational non-linear multibody system (MBS) framework in which the wheel/rail interaction is formulated using a three-dimensional elastic contact formulation that allows for the wheel/rail separation. A triangular shell element is used to build the tank car and describe its deformation, The effect of the coupling between different modes of displacements is demonstrated by comparing the results of the simulations of the flexible and rigid tank car models. It is shown that there is a strong dynamic coupling between different modes of displacements of the tank car, the plate thickness, and the wheel/rail contact parameters. The effect of the flexibility and plate thickness of the tank car on the vehicle critical speed and dynamic characteristics are also examined.

Effects of occlusal scheme on All-on-Four abutments, screws and prostheses: A three-dimensional finite element study

2020 ◽  
Author(s):  
Nurullah Türker ◽  
Hümeyra Tercanlı Alkış ◽  
Steven J Sadowsky ◽  
Ulviye Şebnem Büyükkaplan
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Good Prognosis ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Group Function ◽  
Occlusal Contact ◽  
Maximum Deformation ◽  
Contact Points ◽  
Von Mises

An ideal occlusal scheme plays an important role in a good prognosis of All-on-Four applications, as it does for other implant therapies, due to the potential impact of occlusal loads on implant prosthetic components. The aim of the present three-dimensional (3D) finite element analysis (FEA) study was to investigate the stresses on abutments, screws and prostheses that are generated by occlusal loads via different occlusal schemes in the All-on-Four concept. Three-dimensional models of the maxilla, mandible, implants, implant substructures and prostheses were designed according to the All-on-Four concept. Forces were applied from the occlusal contact points formed in maximum intercuspation and eccentric movements in canine guidance occlusion (CGO), group function occlusion (GFO) and lingualized occlusion (LO). The von Mises stress values for abutment and screws and deformation values for prostheses were obtained and results were evaluated comparatively. It was observed that the stresses on screws and abutments were more evenly distributed in GFO. Maximum deformation values for prosthesis were observed in the CFO model for lateral movement both in the maxilla and mandible. Within the limits of the present study, GFO may be suggested to reduce stresses on screws, abutments and prostheses in the All-on-Four concept.

Quasi-Static Modelling and Computer Simulation of Hanging Cables on Robots

1994 ◽  
Author(s):  
Li-Ping Yang ◽  
Shin-Min Song
Keyword(s):  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Finite Segment ◽  
Revolute Joints ◽  
Highly Nonlinear ◽  
Finite Segment Method ◽  
Newton Raphson ◽  
Static Modelling ◽  
Parameter Perturbation Method ◽  
Raphson Method

Abstract This paper presents a computer method to simulate the quasi-static motion of hanging cables on robots. The shape of the flexible cable is changing during motion and the finite segment method is applied to determine its configuration. The cable is modeled as a series of rigid segments segments connected together through revolute joints in 2-D case and spherical joints in 3-D case. The elasticity of cable is represented by torsional springs at the joints. In both cases, a set of highly nonlinear equations are derived based on force equilibrium and the Newton-Raphson method is applied to calculate the solution. In order to assure convergence and improve computational efficiency, the parameter perturbation method is applied together with the Newton-Raphson method. Also, some computational strategies are developed to simplify the three dimensional problem. Finally, the developed methods are demonstrated in displaying the motion of a hanging cable which is attached to a revolute joint, a prismatic joint and a three degrees of freedom robot.

Automated Fracture Mechanics and Fatigue Analyses Based on Three-Dimensional Finite Elements

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Hitoshi Nakamura ◽  
Wenwei Gu ◽  
Seiichi Tajima ◽  
Osamu Hazama
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Three Dimensional ◽  
3D Fem ◽  
Element Mesh ◽  
Fem Model ◽  
Steel Pipes ◽  
Fatigue Initiation ◽  
Propagation Analysis ◽  
History Of

This paper describes the structure and application of a software system that automates the fatigue initiation and crack propagation analysis based on finite element method (FEM). The system automatically performs necessary procedures to track propagation history of cracks: insertion of a crack and updating of three-dimensional (3D) finite element mesh in accordance with the crack propagation. The system is equipped with a function to automatically perform fatigue analyses using the stress–strain histories at nodes of a 3D FEM model. Some analyses for several examples were carried out for validation. The important example is the surface crack propagation in steel pipes with residual stress.

scholarly journals Technology and equipment for friction stir preweld edge preparation

2021 ◽  
Vol 21 (2) ◽  
pp. 163-170
Author(s):  
Y. G. Lyudmirsky ◽  
А. N. Soloviev ◽  
М. V. Soltovets ◽  
R. R. Kotlyshev ◽  
I. V. Mironov ◽  
...  
Keyword(s):  
Finite Element ◽  
Theoretical Model ◽  
Friction Stir Welding ◽  
Geometric Model ◽  
Three Dimensional ◽  
Welding Process ◽  
Element Model ◽  
Element Mesh ◽  
Laboratory Equipment ◽  
Friction Stir

Introduction. Friction stir welding is widely used due to certain advantages of this method. Factors that reduce the strength of joints made of high-strength aluminum alloys are considered. When welding flat sheets, an effective way to increase the strength of the weld is edge thickening. The paper proposes a method for such thickening. A device is developed, calculations and experiments are carried out. Materials and Methods. Laboratory equipment has been developed to provide simultaneous thickening of two edges to be welded. The main component of this equipment is a steel roller, which is rolled along the edges of two blanks and thickens them due to plastic deformation. The same setup can be used for the friction stir welding process. To calculate the geometry of the thickened edges and the parameters of the deforming roller depending on the value of the edge settlement, a mathematical model based on the contact problem for elastic (roller) and elastoplastic (blank) bodies with a bilinear hardening law has been developed. A three-dimensional simplified geometric model of the facility with account of its symmetry has been constructed. On the contact surfaces, special contact finite elements were selected and the finite element mesh was refined. The numerical implementation of the model was carried out in the ANSYS package. Results. The theoretical model provides assessing the stress-strain state of interacting elements. On the basis of the developed finite element model, the parameters of the thickened edges are calculated, and the geometry of the thickened edges is defined. Using the developed laboratory equipment, full-scale experiments on thickening the edges of the blanks were carried out. The experimental results confirm the adequacy of the developed theoretical model and calculations based on it. The possibility of adjusting the size of the thickened edges is shown.Discussion and Conclusion. A technology for obtaining thickened edges in places of welds is proposed. It will reduce the metal consumption of structures and ensure the bearing capacity of welded joints not lower than similar characteristics of the base metal. A theoretical model of the process is developed, and a numerical experiment providing the selection of the process parameters is carried out. 

2-D Finite Element Analysis of Engineering Components

1995 ◽  
Author(s):  
Ajay Garg
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Finite Elements ◽  
Boundary Conditions ◽  
Three Dimensional ◽  
Radius Of Curvature ◽  
Element Analysis ◽  
Element Mesh ◽  
Require Time ◽  
Simple Boundary

Abstract Design and analysis of engineering components can be categorized under the theory of continuum mechanics, plates/shells or beams. Closed form solutions for determining deformations and stresses are available for simple structures with simple boundary conditions. In the cases of complex structures, boundary conditions and loads, analytical solutions are not readily available. Finite element analysis (FEA) can be performed to resolve the simulation barrier of these analytically indeterminate structures. Similar to analytical approach, FEA can simulate the components through solid, plate/shell or beam elements. Finite element analysis through 3-D solid elements is costly and may require time in weeks, which may not be at the disposal of an analyst. Axi-symmetric components and components with an infinite radius of curvature (flat surfaces), but with complex cross sections can be modeled by 2-D axi-symmetric and plate elements, respectively. Two dimensional finite elements require less time and hardware support than three-dimensional elements. Two development cases of successful application of 2-D finite elements instead of 3-D finite elements are discussed. Experimental and analytical verification of FEA results, and guidelines for checking finite element mesh discretization error are presented.

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