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.

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.

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.

Numerical Study for Global Detection of Cracks Embedded in Beams

1999 ◽  
Author(s):  
S. A. Lipsey ◽  
Y. W. Kwon
Keyword(s):  
Finite Element ◽  
Dynamic Analysis ◽  
Natural Frequency ◽  
Mode Shape ◽  
Numerical Study ◽  
Element Model ◽  
Mode Shapes ◽  
Linear Effect ◽  
Modes Of Vibration ◽  
Damage Simulation

Abstract Damage reduces the flexural stiffness of a structure, thereby altering its dynamic response, specifically the natural frequency, damping values, and the mode shapes associated with each natural frequency. Considerable effort has been put into obtaining a correlation between the changes in these parameters and the location and amount of the damage in beam structures. Most numerical research employed elements with reduced beam dimensions or material properties such as modulus of elasticity to simulate damage in the beam. This approach to damage simulation neglects the non-linear effect that a crack has on the different modes of vibration and their corresponding natural frequencies. In this paper, finite element modeling techniques are utilized to directly represent an embedded crack. The results of the dynamic analysis are then compared to the results of the dynamic analysis of the reduced modulus finite element model. Different modal parameters including both mode shape displacement and mode shape curvature are investigated to determine the most sensitive indicator of damage and its location.

scholarly journals Frequency spectrum of the human head–neck to mechanical vibrations

2017 ◽  
Vol 37 (3) ◽  
pp. 611-618 ◽  
Author(s):  
Bin Yang ◽  
Zheng Shi ◽  
Qun Wang ◽  
Feng Xiao ◽  
Tong-Tong Gu ◽  
...  
Keyword(s):  
Finite Element ◽  
Frequency Spectrum ◽  
Mechanical Vibration ◽  
Three Dimensional ◽  
Human Head ◽  
Element Model ◽  
Mode Shapes ◽  
Joint Disorder ◽  
Biomechanical Responses ◽  
Head Neck

This study is based on a real finite element human head–neck model and concentrates on its numerical vibration characteristic. Frequency spectrum and mode shapes of the finite element model of human head–neck under mechanical vibration have been calculated. These vibration characteristics are in good agreement with the previous studies. The simulated fundamental frequency of 35.25 Hz is fairly similar to the published documents, and rarely reported modal responses such as “mastication” and flipping of nasal lateral cartilages modes, however, are introduced by our three-dimensional modal analysis. These additional modes may be of interest to surgeons or clinicians who are specialized in temporomandibular or rhinoplasty joint disorder. Modal validation in terms of modal shapes proposes a necessity for elaborate modeling to identify each individual part’s extra frequencies. Furthermore, it also studies the influence of damping on resonant frequencies and biomechanical responses. It is discovered that damping has an inverse proportionality between damping effect on natural frequency and that on biomechanical responses.

scholarly journals Development of a finite element human vibration model for use in spacecraft coupled loads analysis

2018 ◽  
Vol 38 (2) ◽  
pp. 839-851 ◽  
Author(s):  
Nancy J Currie-Gregg ◽  
Kelly Carney
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Joint Stiffness ◽  
Low Frequency ◽  
Nonlinear Dynamic Response ◽  
Vibration Model ◽  
Loads Analysis ◽  
Impact Attenuation ◽  
Coupled Loads Analysis ◽  
Coupled Loads

Finite element human vibration models were developed and implemented for use in human-tended spacecraft-coupled loads analysis, an analytical process used to predict low-frequency spacecraft loads which occur during dynamic phases of flight of such as launch, ascent, or ascent aborts. Human vibration may also affect stress predictions for spacecraft systems which the crew interacts with, such as crew seats and crew impact attenuation systems. These human vibration models are three-dimensional, distributed-mass representations of 1st-percentile female, 50th-percentile male, and 99th-percentile male American crew members and provide a relatively simple linear and low-load representation of the nonlinear dynamic response of a seated human. The most significant features of these finite element models are anthropometrically based geometric human mass distribution, soft tissue vibration attributes, and skeleton and joint stiffness.

Application of Lifting-Surface Theory to the Prediction of Hydroelastic Response of Hydrofoil Boats

1968 ◽  
Vol 12 (04) ◽  
pp. 286-301
Author(s):  
C. J. Henry
Keyword(s):  
Equations Of Motion ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Mode Shapes ◽  
Operator Technique ◽  
Elastic Mode ◽  
Surface Theory ◽  
Lifting Surface ◽  
Modes Of Vibration ◽  
Elastic Modes

In this report a theoretical procedure is developed for the prediction of the dynamic response elastic or rigid body, of a hydrofoil-supported vehicle in the flying condition— to any prescribed transient or periodic disturbance. The procedure also yields the stability indices of the response, so that dynamic instabilities such as flutter can also be predicted. The unsteady hydrodynamic forces are introduced in the equations of motion for the elastic vehicle in terms of the indicia I pressure-response functions, which are de rived herein from lifting-surface theory. Thus, the predicted vehicle-response includes the effects of three-dimensional unsteady flow conditions at specified forward speed. The natural frequencies and elastic modes of vibration of the vehicle and foil system in the absence of hydrodynamic effects are presumed known. A numerical procedure is presented for the solution of the downwash integral equations relating the unknown indicial pressure distributions to the specified elastic-mode shapes. The procedure is based on use of the generalized-lift-operator technique together with the collocation method.

scholarly journals A Novel Highly Accurate Finite-Element Family

2017 ◽  
Vol 2017 ◽  
pp. 1-20
Author(s):  
Giovanni Bernardini ◽  
Fabio Cetta ◽  
Luigi Morino
Keyword(s):  
Finite Element ◽  
Structural Dynamics ◽  
Hermite Interpolation ◽  
Natural Frequencies ◽  
Finite Thickness ◽  
Three Dimensional ◽  
Numerical Results ◽  
Small Thickness ◽  
Modes Of Vibration ◽  
Patch Technique

A novel Nth order finite element for interior acoustics and structural dynamics is presented, with N arbitrarily large. The element is based upon a three-dimensional extension of the Coons patch technique, which combines high-order Lagrange and Hermite interpolation schemes. Numerical applications are presented, which include the evaluation of the natural frequencies and modes of vibration of (1) air inside a cavity (interior acoustics) and (2) finite-thickness beams and plates (structural dynamics). The numerical results presented are assessed through a comparison with analytical and numerical results. They show that the proposed methodology is highly accurate. The main advantages however are (1) its flexibility in obtaining different level of accuracy (p-convergence) simply by increasing the number of nodes, as one would do for h-convergence, (2) the applicability to arbitrarily complex configurations, and (3) the ability to treat beam- and shell-like structures as three-dimensional small-thickness elements.

Modal Analysis Based on Finite Element Jaw Crusher Rotor

2014 ◽  
Vol 599-601 ◽  
pp. 547-550
Author(s):  
Mei Ling Hao ◽  
Guang Juan Cheng
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Natural Frequencies ◽  
Weak Link ◽  
Three Dimensional ◽  
Mode Shapes ◽  
Complex Dynamic ◽  
Three Dimensional Modeling ◽  
Dimensional Modeling ◽  
Analysis Of Results

The vertical shaft impact crusher the material is accelerated , while the rotor bear complex dynamic loads , finite element method for three-dimensional modeling of the rotor body and modal analysis , discussion and analysis of results. Won the first 20 natural frequencies and mode shapes , as well as the weak link parts may exist , making the crusher prone resonance attention away from the source at work , as well as designers kinetic design provides some guidance basis.

Vibration Analysis of a Tire Under Static Loading Using Flexible Ring-Based Model

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Aakash Swami ◽  
Ashok Kumar Pandey
Keyword(s):  
Finite Element ◽  
Static Loading ◽  
Contact Region ◽  
Three Dimensional ◽  
Mode Shapes ◽  
Ring Model ◽  
Dimensional Finite Element ◽  
Bending Modes ◽  
Three Dimensional Finite Element ◽  
Flexible Ring

Abstract To address various tire vibration characteristics such as noise, vibration, and harshness, it is necessary to study the tire dynamic performance. In this paper, we focus on investigating the influence of static loading on radial (in-plane) and bending modes and their frequencies of a tire. To model the effect, we first identify important tire parameters, termed as modal parameters, based on three-dimensional ring model and three-dimensional finite element results under free-free conditions without and with temperature variations. After finding the parameters, we have used three-dimensional flexible ring model in which both in-plane and bending modes are considered under static loading. When load is applied, tire behavior changes and it becomes more stiffer. Thus, it fixes the tire to the road and increases the contact region. In this paper, we define this contact region over θf < θ < 2π and the region 0 < θ < θf can be considered free-free. Subsequently, we assume the expression of radial and bending modes in terms of generalized coordinates satisfying the above boundary conditions and obtain kinetic and potential energy by integrating it over 0 < θ < θf. The unknown coordinate is obtained by satisfying the governing conditions. Finally, corresponding mode shapes and frequencies are obtained. The assumed modes and frequencies are validated with three-dimensional finite element model using abaqus. The same procedure can be extended to compute modes and frequencies as a function of temperature under static loading for a constant tire pressure.

Effect of Low-Frequency Vibration on Human Body in Standing Position Exposed to Railway Vehicle

2018 ◽  
Vol 10 (3) ◽  
Author(s):  
Rajesh Govindan ◽  
Suraj Prakash Harsha
Keyword(s):  
Finite Element ◽  
Natural Frequency ◽  
Human Body ◽  
Low Frequency ◽  
Vertical Direction ◽  
Standing Position ◽  
Mode Shapes ◽  
Railway Vehicle ◽  
Lateral Direction ◽  
Low Frequency Vibration

In this paper, the dynamic characteristics of the human body were investigated by developing a 3-D finite element model based on 50th percentile anthropometric data for a 54 kg Indian male subject in standing position by considering human body segments as an ellipsoid. The finite element modal analysis is carried out to extract several low-frequency vibration modes and its vibration mode shapes were presented in this paper. The results show that the lowest natural frequency of the standing passenger model occurs in the fore-and-aft direction. The second natural frequency occurs in the lateral direction and the first order natural frequency of the standing passenger model in the vertical direction occurs at 5.379 Hz. The model will be helpful to predict the vibration response of human body under various vibration environment encounters in the railway vehicle.

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