Multibody Simulation of a Freight Bogie With Friction Dampers

Joint Rail ◽  
2002 ◽  
Author(s):  
N. Bosso ◽  
A. Gugliotta ◽  
A. Soma`
Keyword(s):  
The Other ◽  
Friction Damper ◽  
Multibody Simulation ◽  
Dimensional Model ◽  
Vehicle Model ◽  
Friction Dampers ◽  
Numerical Efficiency ◽  
Friction Element ◽  
Low Performance ◽  
Model Of Friction

Freight bogies are often built using friction element instead of viscous dampers with great advantage regarding cost and manutenibility. On the other hand this technical choice leads to low performance of the vehicle. The aim of this work is to evaluate the behaviour of a Y25 freight bogie that is the most diffuse in Europe where friction dampers are used to reduce vertical and hunting vibrations. The purpose is also to improve a bi-dimensional model of friction damper and to test its numerical efficiency on a whole vehicle model in a multibody code.

Seismic response analysis of frame with friction damper

2019 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Min Zhang ◽  
Dongzhuo Wang
Keyword(s):  
Seismic Response ◽  
Seismic Waves ◽  
State Equation ◽  
The Other ◽  
Frame Structure ◽  
Response Analysis ◽  
Friction Damper ◽  
Content Type ◽  
Friction Dampers ◽  
Damping Effect

Purpose This paper aims to study the seismic response of frame structure with friction dampers. Design/methodology/approach The state equation of the structure subjected to the earthquake is presented and solved, from which the maximum drift and the interlayer drift angle of the floors of the structure subjected to the seismic waves of four types of sites are analyzed. Findings The result indicates that the damping effect is significant on the floors with the friction damper but is almost little influence on the other floor. Originality/value The result indicates that the damping effect is significant on the floors with the friction damper but is almost little influence on the other floor.

Resilient Factors in Students with Disabilities

2018 ◽  
Vol 5 (2) ◽  
pp. 23 ◽  
Author(s):  
Gustavo Rafael Escobar Delgado ◽  
Anicia Katherine Tarazona Meza ◽  
Andy Einstein García García
Keyword(s):  
Academic Performance ◽  
Students With Disabilities ◽  
Latin American ◽  
Descriptive Study ◽  
The Other ◽  
Disabled Students ◽  
Low Performance ◽  
The Relationship ◽  
Latin American Population

The research analyzes the relationship between factors of resilience and academic performance in disabled students studying at the Technical University of Manabí. It is a correlational descriptive study conducted with a population of 88 disabled students, of which two groups were selected, one with high academic performance and the other with low performance. A questionnaire was designed and applied to determine the level of quality of life and risk factors of adolescents. Resilience was measured with the SV-RES scale created for the Latin American population.

scholarly journals Improved Reliability of Bladed Disks due to Friction Dampers

1997 ◽  
Author(s):  
Walter Sextro ◽  
Karl Popp ◽  
Ivo Wolter
Keyword(s):  
Dry Friction ◽  
Three Dimensional ◽  
Line Contact ◽  
Two Dimensional ◽  
Centrifugal Forces ◽  
Friction Damper ◽  
Blade Vibration ◽  
Friction Dampers ◽  
Bladed Disk ◽  
Bladed Disk Assembly

Friction dampers are installed underneath the blade platforms to improve the reliability. Because of centrifugal forces the dampers are pressed onto the platforms. Due to dry friction and the relative motion between blades and dampers, energy is dissipated, which results in a reduction of blade vibration amplitudes. The geometry of the contact is in many cases like a Hertzian line contact. A three-dimensional motion of the blades results in a two-dimensional motion of one contact line of the friction dampers in the contact plane. An experiment with one friction damper between two blades is used to verify the two-dimensional contact model including microslip. By optimizing the friction dampers masses, the best damping effects are obtained. Finally, different methods are shown to calculate the envelope of a three-dimensional response of a detuned bladed disk assembly (V84.3-4th-stage turbine blade) with friction dampers.

scholarly journals Friction Damper Optimisation: Simulation of Rainbow Tests

1999 ◽  
Author(s):  
Kenan Y. Sanliturk ◽  
David J. Ewins ◽  
Robert Elliott ◽  
Jeff S. Green
Keyword(s):  
Harmonic Balance Method ◽  
Lumped Parameter Model ◽  
Friction Damper ◽  
Blade Vibration ◽  
Friction Dampers ◽  
Lumped Parameter ◽  
Engine Order ◽  
Resonance Response ◽  
Theoretical Predictions ◽  
Different Characteristics

Friction dampers have been used to reduce turbine blade vibration levels for a considerable period of time. However, optimal design of these dampers has been quite difficult due both to a lack of adequate theoretical predictions and to difficulties in conducting reliable experiments. One of the difficulties of damper weight optimisation via the experimental route has been the inevitable effects of mistuning. Also, conducting separate experiments for different damper weights involves excessive cost. Therefore, current practice in the turbomachinery industry has been to conduct so-called ‘rainbow tests’ where friction dampers with different weights are placed between blades with a predefined configuration. However, it has been observed that some rainbow test results have been difficult to interpret and have been inconclusive for determining the optimum damper weight for a given bladed-disc assembly. A new method of analysis — a combination of Harmonic Balance Method and structural modification approaches — is presented in this paper for the analysis of structures with friction interfaces and the method is applied to search for qualitative answers about the so-called ‘rainbow tests’ in turbomachinery applications. A simple lumped-parameter model of a bladed-disc model was used and different damper weights were modelled using friction elements with different characteristics. Resonance response levels were obtained for bladed discs with various numbers of blades under various engine-order excitations. It was found that rainbow tests, where friction dampers with different weights are used on the same bladed-disc assembly, can be used to find the optimum damper weight if the mode of vibration concerned has weak blade-to-blade coupling (the case where the disc is almost rigid and blades vibrate almost independently from each other). Otherwise, it is very difficult to draw any reliable conclusion from such expensive experiments.

scholarly journals MODFLOW’s River Package: Part 2: Correction, Combining Analytical and Numerical Approaches

2019 ◽  
pp. 1-23
Author(s):  
Hubert J. Morel-Seytoux
Keyword(s):  
Large Scale ◽  
The Other ◽  
Previous Article ◽  
Regional Studies ◽  
Hydrologic Models ◽  
Numerical Efficiency ◽  
Flow Interaction ◽  
Numerical Approaches

Most widely used integrated hydrologic models still describe the flow interaction between streams and aquifers using primitive early concepts. In the previous article the shortcomings of the methodology were shown in great details. In this second part means are presented by which improvements can be introduced into the procedures.  Accuracy and numerical efficiency will be improved. The article describes in details the proposed alternatives for both the saturated and the unsaturated connections. In the article reference is made specifically to the code MODFLOW.  Most of the other integrated hydrologic models used for large-scale regional studies apply essentially the same methodology to estimate seepage.

Semiactive Seismic Isolation System Using Controllable Friction Damper. 2nd Report. Study of the System with Distributed Controllable Friction Dampers.

1992 ◽  
Vol 58 (551) ◽  
pp. 2012-2016
Author(s):  
Takafumi FUJITA ◽  
Mamoru SHIMAZAKI ◽  
Yutaka HAYAMIZU ◽  
Satoru AIZAWA ◽  
Masahiko HIGASHINO ◽  
...  
Keyword(s):  
Seismic Isolation ◽  
Friction Damper ◽  
Isolation System ◽  
Friction Dampers

A Resonance Tracking Algorithm for the Prediction of Turbine Forced Response With Friction Dampers

2000 ◽  
Author(s):  
C. Bréard ◽  
J. S. Green ◽  
M. Vahdati ◽  
M. Imregun
Keyword(s):  
Rotor Blade ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Forced Response ◽  
Rotor Blades ◽  
Test Case ◽  
Friction Damper ◽  
Blade Vibration ◽  
Frequency Shifts ◽  
Friction Dampers

This paper presents an iterative method for determining the resonant speed shift when non-linear friction dampers are included in turbine blade roots. Such a need arises when conducting response calculations for turbine blades where the unsteady aerodynamic excitation must be computed at the exact resonant speed of interest. The inclusion of friction dampers is known to raise the resonant frequencies by up to 20% from the standard assembly frequencies. The iterative procedure uses a viscous, time-accurate flow representation for determining the aerodynamic forcing, a look-up table for evaluating the aerodynamic boundary conditions at any speed, and a time-domain friction damping module for resonance tracking. The methodology was applied to an HP turbine rotor test case where the resonances of interest were due to the 1T and 2F blade modes under 40 engine-order excitation. The forced response computations were conducted using a multi-stage approach in order to avoid errors associated with “linking” single stage computations since the spacing between the two bladerows was relatively small. Three friction damper elements were used for each rotor blade. To improve the computational efficiency, the number of rotor blades was decreased by 2 to 90 in order to obtain a stator/rotor blade ratio of 4/9. However, the blade geometry was skewed in order to match the capacity (mass flow rate) of the components and the condition being analysed. Frequency shifts of 3.2% and 20.0% were predicted for the 1T/40EO and 2F/40EO resonances in about 3 iterations. The predicted frequency shifts and the dynamic behaviour of the friction dampers were found to be within the expected range. Furthermore, the measured and predicted blade vibration amplitudes showed a good agreement, indicating that the methodology can be applied to industrial problems.

Seismic retrofit of structures using rotational friction dampers with restoring force

2020 ◽  
Vol 23 (16) ◽  
pp. 3525-3540
Author(s):  
Asad Naeem ◽  
Jinkoo Kim
Keyword(s):  
Ground Motions ◽  
Design Procedure ◽  
Steel Structures ◽  
Friction Damper ◽  
Heavy Duty ◽  
Limit States ◽  
Restoring Force ◽  
Friction Dampers ◽  
Torsional Spring ◽  
Capacity Spectrum

In this study, the seismic performance of a rotational friction damper with restoring force is presented. The torsional spring friction damper consists of rotational friction pads with the heavy duty torsional springs attached on both sides of the friction damper. An analytical model and a design procedure for the damper are developed using capacity spectrum method. A parametric study is carried out to investigate the influence of the torsional spring in the response of the structure when subjected to ground motions. The seismic performances of steel structures retrofitted with the torsional spring friction damper and conventional rotational friction dampers are evaluated using fragility analysis, which shows that the structure retrofitted with the torsional spring friction damper has the smallest probability of reaching the specific limit states.

scholarly journals A-31 Trails-X Trail-Level Performance Using the Profile Variability Index

2019 ◽  
Vol 34 (6) ◽  
pp. 890-890
Author(s):  
J Greene ◽  
M Messer ◽  
D Hartman ◽  
C Reynolds
Keyword(s):  
The Other ◽  
Hyperactivity Disorder ◽  
Standardization Sample ◽  
Significant Difference ◽  
Trail Making ◽  
New Type ◽  
Variability Index ◽  
The Mean ◽  
Low Performance ◽  
Level Performance

Abstract Objective The Trails-X is a new type of trail-making test that emphasizes executive function and does not require either literacy or numeracy. The purpose of this study was to examine performance variability across trails. Method Participants were the Trails-X standardization sample and individuals with traumatic brain injury (TBI), learning disabilities (LD), intellectual disabilities (ID), attention-deficit hyperactivity disorder (ADHD), and dementia. Trail-level performance was assessed via the mean Matrix, Connected Circles, and Time to Discontinue scores across trails. The Profile Variability Index (PVI) was calculated (Plake, Reynolds, & Gutkin, 1981) and clinical groups and standardization samples were compared via a one-way ANOVA. Results Across all trails, the mean Matrix score was 6 (possible range = 1-12) for the standardization sample and as low as 3 for the dementia and ID samples. The mean Connected Circles score was 16 (possible range = 0-22) and as low as 12 for the dementia sample. The mean Time to Discontinue score was 39 seconds (possible range = 1-75) and as high as 55 for the dementia sample. There was a statistically significant difference on the PVI score (F(5,845) = 6.921, p = .000). The dementia (M = 4.77) and ID (M = 5.11) samples had significantly lower (p < .05) PVI scores than the other samples, which were not significantly different from each other. Conclusions The dementia and ID samples were characterized by consistently low performance while the other samples were characterized by moderate amounts of variability, indicating that some variability across trails should be expected within less impaired individuals.

scholarly journals Action minimization and macroscopic interface motion under forced displacement

2018 ◽  
Vol 24 (2) ◽  
pp. 765-792 ◽  
Author(s):  
Panagiota Birmpa ◽  
Dimitrios Tsagkarogiannis
Keyword(s):  
Stochastic Process ◽  
Evolution Equation ◽  
Fixed Time ◽  
Companion Paper ◽  
The Other ◽  
Final Position ◽  
Dimensional Model ◽  
Interface Motion ◽  
One Dimensional ◽  
Non Local

We study an one dimensional model where an interface is the stationary solution of a mesoscopic non local evolution equation which has been derived by a microscopic stochastic spin system. Deviations from this evolution equation can be quantified by obtaining the large deviations cost functional from the underlying stochastic process. For such a functional, derived in a companion paper, we investigate the optimal way for a macroscopic interface to move from an initial to a final position distant by R within fixed time T. We find that for small values of R∕T the interface moves with a constant speed, while for larger values there appear nucleations of the other phase ahead of the front.

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