Time-Varying Behavior of a Statically Indeterminate Shafting System in a Hydrodynamic Journal Bearing

1987 ◽  
Vol 109 (1) ◽  
pp. 115-123 ◽  
Author(s):  
Z. H. Karni ◽  
M. G. Parsons ◽  
Z. P. Mourelatos
Keyword(s):  
Control Method ◽  
Optimization Technique ◽  
Three Dimensional ◽  
Integration Time ◽  
Time Varying ◽  
The Finite Element Method ◽  
Time Step ◽  
Hydrodynamic Analysis ◽  
Oil Film ◽  
Hourglass Control

A new direct iterative method for obtaining the time-varying behavior of a statically indeterminate shafting system within one of its hydrodynamic journal bearings is described. A modified Newmark’s method is used to step in time. At each integration time step an optimization technique iterates between the shafting system and the oil film analyses until an equilibrium is achieved. The three-dimensional shafting system structural analysis and the two-dimensional oil film hydrodynamic analysis utilize the finite element method. The “hourglass control” method is employed for the construction of the oil film fluidity matrix. A numerical example illustrates the method.

Comparison of Two Time-Integration Algorithms for an Anisotropic Damage Model Coupled with Plasticity

2015 ◽  
Vol 784 ◽  
pp. 292-299 ◽  
Author(s):  
Stephan Wulfinghoff ◽  
Marek Fassin ◽  
Stefanie Reese
Keyword(s):  
Evolution Equations ◽  
Damage Model ◽  
Time Integration ◽  
Three Dimensional ◽  
Anisotropic Damage ◽  
Euler Scheme ◽  
The Finite Element Method ◽  
Time Step ◽  
Implicit Euler Scheme ◽  
Integration Algorithms

In this work, two time integration algorithms for the anisotropic damage model proposed by Lemaitre et al. (2000) are compared. Specifically, the standard implicit Euler scheme is compared to an algorithm which implicitly solves the elasto-plastic evolution equations and explicitly computes the damage update. To this end, a three dimensional bending example is solved using the finite element method and the results of the two algorithms are compared for different time step sizes.

scholarly journals Effective Method for Analysis of Electrothermally Coupled Fields

1995 ◽  
Vol 2 (3) ◽  
pp. 219-225
Author(s):  
Jacek Korytkowski ◽  
Stanisław Wincenciak
Keyword(s):  
Physical Phenomenon ◽  
Three Dimensional ◽  
Main Idea ◽  
The Finite Element Method ◽  
Temperature Dependent ◽  
Time Step ◽  
Coupled Fields ◽  
Strongly Nonlinear ◽  
Step Selection ◽  
Raphson Method

An effective method is presented for solving a nonlinear system of partial differential equations that describe the time-dependent electrothermally coupled fields for passage of constant electric current in a three-dimensional conductive medium. A numerical model of this physical phenomenon was obtained by the finite element method, which takes into account the temperature-dependent characteristics describing the material parameters and conditions of heat transmission outside of the analyzed objects. These characteristics and conditions make the problem strongly nonlinear. The solution uses the Newton-Raphson method with the appropriate procedure for determining the Jacobian matrix elements. The main idea of the proposed method is the use of an automatic time step selection algorithm to solve heat conduction equations. The influence of the assumed accuracy value on the final result of the nonlinear calculation is discussed. The theoretical results were confirmed by the numerical experiments performed with selected physical objects.

Subcycled Hourglass Control for Explicit Time Integration of Dynamic Relaxation Equations

2002 ◽  
Author(s):  
D. R. Metzger ◽  
S. Gao
Keyword(s):  
Temporal Integration ◽  
Time Integration ◽  
Three Dimensional ◽  
Internal Force ◽  
Time Interval ◽  
Time Step ◽  
Central Difference ◽  
Finite Element Program ◽  
Explicit Finite Element ◽  
Hourglass Control

Explicit methods, such as the central difference operator, rely on the economical evaluation of internal forces at each time step of a transient dynamic problem. One-point quadrature applied to the spatial discretization provides the greatest efficiency, but hourglass control is required to eliminate spurious zero energy modes. Computationally practical hourglass control methods involve considerable approximation in evaluating the internal force. Thus, a small additional approximation due to an alternative temporal integration of the hourglass force may not seriously affect the accuracy of the analysis. In particular, the possibility of evaluating the hourglass terms on a larger time interval than the usual stable time step could provide significant efficiencies. The proposed approach of subcycling the hourglass terms is examined in detail with respect to stability and accuracy. Implementation into an explicit finite element program is demonstrated on a three-dimensional example that involves several hourglass modes, and the new method proves to be beneficial for noninertial problems where artificial damping is used.

A Three-Dimensional oil film Temperature Distribution in Tilting Thrust Bearings

1974 ◽  
Vol 16 (2) ◽  
pp. 121-124 ◽  
Author(s):  
A. K. Tieu
Keyword(s):  
Finite Element Method ◽  
Numerical Scheme ◽  
Three Dimensional ◽  
Finite Width ◽  
The Finite Element Method ◽  
Oil Film ◽  
Thrust Bearings ◽  
Pressure Distributions ◽  
Temperature And Pressure ◽  
Thrust Pad

The oil film temperature and pressure distributions of the finite width Michell tilting thrust pad are determined from a numerical scheme based on the finite element method. These computed results correlate very well with those obtained from the experiment.

Oil-Film Temperature Distribution in an Infinitely wide Slider Bearing: An Application of the Finite-Element Method

1973 ◽  
Vol 15 (4) ◽  
pp. 311-320 ◽  
Author(s):  
A. K. Tieu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Energy Equation ◽  
Three Dimensional ◽  
The Finite Element Method ◽  
Slider Bearing ◽  
Oil Film ◽  
Temperature Distributions ◽  
Oil Films ◽  
Element Method

From the Glansdorff–Prigogine local potential in non-equilibrium thermodynamics (1)† (2), a variational principle for a thin film incompressible flow with viscous dissipation is formulated as the basis of a finite-element method, which is applied to solve the energy equation. Temperature distributions in tapered land and parallel oil films for infinitely wide bearings are obtained by digital computer. The application of the finite-element method in a three-dimensional oil film with side leakage is also discussed.

Attenuation of Gas Pulsation in the Valve Chamber of a Reciprocating Compressor Using the Helmholtz Resonator

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Xiaohan Jia ◽  
Boxiang Liu ◽  
Jianmei Feng ◽  
Xueyuan Peng
Keyword(s):  
Characteristic Frequency ◽  
Control Method ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Helmholtz Resonator ◽  
Resonance Region ◽  
Piping System ◽  
Reciprocating Compressor ◽  
The Finite Element Method ◽  
Attenuation Characteristics

This paper presents testing and analysis results associated with a new control method based on the Helmholtz resonator to suppress the pressure pulsations in the valve chamber and cylinder nozzle of a reciprocating compressor. The characteristic response of the designed Helmholtz resonator was analyzed and its attenuation characteristics on the gas pulsation were investigated. A three-dimensional acoustic model of the gas pulsation was established by means of the finite element method (FEM) for a compressor discharge piping system with and without the resonator. The gas column natural frequencies of the piping system and the pressure wave profiles were predicted using the presented model and validated by comparing the simulated results with the experimental data. The results showed that the pressure pulsating amplitude in the valve chamber was reduced by 40.4% when the resonator was installed. If the resonance frequency of the resonator shifted from the cylinder nozzle characteristic frequency by a range of ±13%, the reduction in the pressure fluctuations within the valve chamber was about 24%. The best attenuation effectiveness on the valve chamber, a reduction of 47%, was obtained when two resonators were installed on the valve covers of both the head and crank ends. Two new frequencies of 40.4 Hz and 66.9 Hz appeared to replace the original cylinder nozzle characteristic frequency of 53.9 Hz with the Helmholtz resonator installation, and the corresponding resonance region was transferred from the valve chamber to the resonator.

Comparison of Conventional and Pontic Fixed Partial Dentures Over Implants Using the Finite Element Method: Three-Dimensional Analysis of Cortical and Medullary Bone Stress

2020 ◽  
Vol 46 (3) ◽  
pp. 175-181
Author(s):  
Marcelo Bighetti Toniollo ◽  
Mikaelly dos Santos Sá ◽  
Fernanda Pereira Silva ◽  
Giselle Rodrigues Reis ◽  
Ana Paula Macedo ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Three Dimensional ◽  
The Finite Element Method ◽  
Medullary Bone ◽  
Principal Stresses ◽  
Bone Stress ◽  
Bone Damage ◽  
Rehabilitation System ◽  
Minimum Requirements

Rehabilitation with implant prostheses in posterior areas requires the maximum number of possible implants due to the greater masticatory load of the region. However, the necessary minimum requirements are not always present in full. This project analyzed the minimum principal stresses (TMiP, representative of the compressive stress) to the friable structures, specifically the vestibular face of the cortical bone and the vestibular and internal/lingual face of the medullary bone. The experimental groups were as follows: the regular splinted group (GR), with a conventional infrastructure on 3 regular-length Morse taper implants (4 × 11 mm); and the regular pontic group (GP), with a pontic infrastructure on 2 regular-length Morse taper implants (4 × 11 mm). The results showed that the TMiP of the cortical and medullary bones were greater for the GP in regions surrounding the implants (especially in the cervical and apical areas of the same region) but they did not reach bone damage levels, at least under the loads applied in this study. It was concluded that greater stress observed in the GP demonstrates greater fragility with this modality of rehabilitation; this should draw the professional's attention to possible biomechanical implications. Whenever possible, professionals should give preference to use of a greater number of implants in the rehabilitation system, with a focus on preserving the supporting tissue with the generation of less intense stresses.

Towards Predicting Relative Belt Edge Endurance With the Finite Element Method

1990 ◽  
Vol 18 (4) ◽  
pp. 216-235 ◽  
Author(s):  
J. De Eskinazi ◽  
K. Ishihara ◽  
H. Volk ◽  
T. C. Warholic
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Three Dimensional ◽  
The Finite Element Method ◽  
Shear Deformations ◽  
Element Analysis ◽  
Vertical Loading ◽  
Predicted Values ◽  
Element Method

Abstract The paper describes the intention of the authors to determine whether it is possible to predict relative belt edge endurance for radial passenger car tires using the finite element method. Three groups of tires with different belt edge configurations were tested on a fleet test in an attempt to validate predictions from the finite element results. A two-dimensional, axisymmetric finite element analysis was first used to determine if the results from such an analysis, with emphasis on the shear deformations between the belts, could be used to predict a relative ranking for belt edge endurance. It is shown that such an analysis can lead to erroneous conclusions. A three-dimensional analysis in which tires are modeled under free rotation and static vertical loading was performed next. This approach resulted in an improvement in the quality of the correlations. The differences in the predicted values of various stress analysis parameters for the three belt edge configurations are studied and their implication on predicting belt edge endurance is discussed.

Disorganization of a hole tone feedback loop by an axisymmetric obstacle on a downstream end plate

2014 ◽  
Vol 757 ◽  
pp. 908-942 ◽  
Author(s):  
K. Matsuura ◽  
M. Nakano
Keyword(s):  
Nozzle Exit ◽  
Passive Control ◽  
Control Method ◽  
Three Dimensional ◽  
Acoustic Power ◽  
Shear Layers ◽  
Mean Velocity ◽  
End Plate ◽  
Air Jet ◽  
Practical Engineering

AbstractThis study investigates the suppression of the sound produced when a jet, issued from a circular nozzle or hole in a plate, goes through a similar hole in a second plate. The sound, known as a hole tone, is encountered in many practical engineering situations. The mean velocity of the air jet $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}u_0$ was $6\text {--}12\ \mathrm{m}\ {\mathrm{s}}^{-1}$. The nozzle and the end plate hole both had a diameter of 51 mm, and the impingement length $L_{im}$ between the nozzle and the end plate was 50–90 mm. We propose a novel passive control method of suppressing the tone with an axisymmetric obstacle on the end plate. We find that the effect of the obstacle is well described by the combination ($W/L_{im}$, $h$) where $W$ is the distance from the edge of the end plate hole to the inner wall of the obstacle, and $h$ is the obstacle height. The tone is suppressed when backflows from the obstacle affect the jet shear layers near the nozzle exit. We do a direct sound computation for a typical case where the tone is successfully suppressed. Axisymmetric uniformity observed in the uncontrolled case is broken almost completely in the controlled case. The destruction is maintained by the process in which three-dimensional vortices in the jet shear layers convect downstream, interact with the obstacle and recursively disturb the jet flow from the nozzle exit. While regions near the edge of the end plate hole are responsible for producing the sound in the controlled case as well as in the uncontrolled case, acoustic power in the controlled case is much lower than in the uncontrolled case because of the disorganized state.

scholarly journals Three-Dimensional Elastodynamic Analysis Employing Partially Discontinuous Boundary Elements

Algorithms ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 129
Author(s):  
Yuan Li ◽  
Ni Zhang ◽  
Yuejiao Gong ◽  
Wentao Mao ◽  
Shiguang Zhang
Keyword(s):  
Side Effect ◽  
Domain Boundary ◽  
Three Dimensional ◽  
Boundary Integral ◽  
Integration Scheme ◽  
Computational Accuracy ◽  
Time Step ◽  
Corner Points ◽  
Discontinuous Elements ◽  
The Time Domain

Compared with continuous elements, discontinuous elements advance in processing the discontinuity of physical variables at corner points and discretized models with complex boundaries. However, the computational accuracy of discontinuous elements is sensitive to the positions of element nodes. To reduce the side effect of the node position on the results, this paper proposes employing partially discontinuous elements to compute the time-domain boundary integral equation of 3D elastodynamics. Using the partially discontinuous element, the nodes located at the corner points will be shrunk into the element, whereas the nodes at the non-corner points remain unchanged. As such, a discrete model that is continuous on surfaces and discontinuous between adjacent surfaces can be generated. First, we present a numerical integration scheme of the partially discontinuous element. For the singular integral, an improved element subdivision method is proposed to reduce the side effect of the time step on the integral accuracy. Then, the effectiveness of the proposed method is verified by two numerical examples. Meanwhile, we study the influence of the positions of the nodes on the stability and accuracy of the computation results by cases. Finally, the recommended value range of the inward shrink ratio of the element nodes is provided.

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