scholarly journals Testing and Modelling of Elastomeric Element for an Embedded Rail System

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6968
Author(s):  
Qianqian Li ◽  
Roberto Corradi ◽  
Egidio Di Gialleonardo ◽  
Stefano Bionda ◽  
Andrea Collina
Keyword(s):  
Dynamic Properties ◽  
Reaction Force ◽  
Time History ◽  
Wide Frequency Range ◽  
Equivalent Stiffness ◽  
Zener Model ◽  
Elastomeric Material ◽  
Rail System ◽  
Non Linear ◽  
Stiffness And Damping

Modelling of elastomeric elements of railway components, able to represent stiffness and damping characteristics in a wide frequency range, is fundamental for simulating the train–track dynamic interaction, covering issues such as rail deflection as well as transmitted forces and higher frequency phenomena such as short pitch corrugation. In this paper, a modified non-linear Zener model is adopted to represent the dependences of stiffness and damping of the rail fastening, made of elastomeric material, of a reference Embedded Rail System (ERS) on the static preload and frequency of its deformation. In order to obtain a reliable model, a proper laboratory test set-up is built, considering sensitivity and frequency response issues. The equivalent stiffness and damping of the elastomeric element are experimentally characterised with force-controlled mono-harmonic tests at different frequencies and under various static preloads. The parameters of the non-linear Zener model are identified by the experimental equivalent stiffness and damping. The identified model correctly reproduces the frequency- and preload-dependent dynamic properties of the elastomeric material. The model is verified to be able to predict the dynamic behaviour of the elastomeric element through the comparison between the numerically simulated and the experimentally measured reaction force to a given deformation time history. Time domain simulations with the model of the reference ERS demonstrate that the modelled frequency- and preload-dependent stiffness and damping of the elastomeric material make a clear difference in the transient and steady-state response of the system when distant frequency contributions are involved.

A Test Rig for Air Bearings Dynamic Characterization

2005 ◽  
Author(s):  
E. Bellabarba ◽  
R. Ruiz ◽  
S. Di´az ◽  
V. Rastelli
Keyword(s):  
Dynamic Properties ◽  
Excitation Frequency ◽  
External Diameter ◽  
Air Bearings ◽  
Equivalent Stiffness ◽  
Dynamic Characterization ◽  
Dynamic Forces ◽  
Present Design ◽  
Rotation Plane ◽  
Stiffness And Damping

This paper describes the design and operation of an experimental facility for measurement of equivalent stiffness and damping of air bearings. The rig uses two magnetic bearings to impose any given orbit to the journal, including displacement in two perpendicular directions on the rotation plane and tilting on the conical mode. Dynamic forces are measured directly on the test bearing housing. Data is gathered and processed using PC based data acquisition boards and software. Only the stiffness and damping coefficients of the fluid film are calculated as a function of the excitation frequency, being it synchronous or not. The present design allows testing air bearings up to 44 mm in external diameter and at frequencies up to 1 KHz. Preliminary testing was performed on this research that demonstrates the capability of the apparatus to measure the dynamic properties with ease and accuracy.

Experimental study on the dynamic properties of the dual-chamber solid and liquid mixture vibration isolator

2018 ◽  
Vol 24 (22) ◽  
pp. 5302-5311 ◽  
Author(s):  
FS Li ◽  
Q Chen ◽  
JH Zhou
Keyword(s):  
Liquid Mixture ◽  
Dynamic Properties ◽  
Liquid Column ◽  
Test Results ◽  
Equivalent Stiffness ◽  
Dual Chamber ◽  
Equivalent Damping ◽  
Fluid Damping ◽  
Equivalent Mass ◽  
Stiffness And Damping

The dual-chamber solid and liquid mixture (SALiM) isolator exhibits multiple stiffness and damping properties with various parameters. As a passive isolation device, the dual-chamber SALiM isolator can also obtain a variable stiffness property by substituting the valve with an active throttle device. Before that, the dynamic properties of the isolator need to be further investigated. Sine sweep tests under different valve openings were implemented to analyze the frequency response characteristics of the system. Two hydro pressure sensors were added into the two chambers to record the pressure signals, with which the equivalent stiffness, equivalent damping, fluid damping, and equivalent mass of the liquid column were identified. Based on the test results, numerical and theoretical analysis, the dynamic properties of the isolator including the influence of the fluid damping and inertia mass on the equivalent stiffness, the relation between the isolator's equivalent damping and the fluid damping, the fluid capacity of the linking tube, and the equivalent mass of the liquid column were analyzed in depth. Conclusions about stiffness and damping obtained from the test results correspond well with those from the theoretical analysis, but the identification results of the equivalent mass, which show that the negative correlation of equivalent mass of the liquid column with its response amplitude seems controversial. An assumption is proposed to explain the abnormal characteristics of the liquid column. However, the exact model of the inertia track needs further exploration and verification.

Influence of Machine Tool Covers on Feed Drives

2011 ◽  
Author(s):  
Petr Kolar ◽  
Jan Masek ◽  
Jiri Sveda ◽  
Jan Hudec
Keyword(s):  
Machine Tool ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Reaction Force ◽  
Point Of View ◽  
Feed Drive ◽  
Feed Drives ◽  
Maximum Reaction ◽  
Stiffness And Damping ◽  
Multi Body

Machine tool covers are important parts of the machine. From the point of view of feed drives, a cover is an additional multi-body system that influences the dynamic properties of the feed drive and the positioning accuracy of the machine. The advantages of covers connected to the machine table with flexible elements are shown on simulation and experimental results. A mathematical model of the cover and its connection to the machine table is described. Optimization of the stiffness and damping ratio for the connection, using a model of the cover, is suggested. The optimal connection parameters cause decreasing of maximum reaction force acting from the cover to the feed drive. This phenomenon is presented on simulation example and also on the experiment results.

scholarly journals Modeling and Dynamic Properties of a Four-Parameter Zener Model Vibration Isolator

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
Wen-ku Shi ◽  
Chen Qian ◽  
Zhi-yong Chen ◽  
Yang Cao ◽  
Heng-hai Zhang
Keyword(s):  
High Performance ◽  
Dynamic Properties ◽  
Structural Parameters ◽  
Dynamic Stiffness ◽  
Installation Space ◽  
Structural Parameter ◽  
Channel Diameter ◽  
Zener Model ◽  
Isolation System ◽  
Stiffness And Damping

To install high-performance isolators in a limited installation space, a novel passive isolator based on the four-parameter Zener model is proposed. The proposed isolator consists of three major parts, namely, connecting structure, sealing construction, and upper and lower cavities, all of which are enclosed by four segments of metal bellows with the same diameter. The equivalent stiffness and damping model of the isolator are derived from the dynamic stiffness of the isolation system. Experiments are conducted, and the experiment error is analyzed. Test results verify the validity of the model. Theoretical analysis and numerical simulation reveal that the stiffness and damping of the isolator have multiple properties with different exciting amplitudes and structural parameters. In consideration of the design of the structural parameter, the effects of exciting amplitude, damp channel diameter, equivalent cylinder diameter of cavities, sum of the stiffness of the bellows at the end of the isolator, and length of damp channel on the dynamic properties of the isolator are discussed comprehensively. A design method based on the parameter sensitivity of the isolator’s design parameter is proposed. Thus, the novel isolator can be practically applied to engineering and provide a significant contribution in the field.

scholarly journals COMPARISON OF METHODS USED FOR SEISMIC ANALYSIS OF STRUCTURES

2017 ◽  
Vol 13 ◽  
pp. 20 ◽  
Author(s):  
Petr Čada ◽  
Jiří Máca
Keyword(s):  
Seismic Analysis ◽  
Linear Time ◽  
Dynamic Properties ◽  
Response Spectrum ◽  
Time History ◽  
Time History Analysis ◽  
Seismic Load ◽  
Eurocode 8 ◽  
History Analysis ◽  
Non Linear

This paper investigates effects of the seismic load to a structure. The article describes main methods of the definition and practical application of the seismic load based on the Standard Eurocode 8. There was made a comparison of all methods using the same structure. A simple two-storeyed concrete 2D-frame with fixed joints was chosen. A one another model with rigid beams for some calculations was defined. The second model can be used for hand-calculations as a cantilever with two masses. The paper describes main dynamic properties of the chosen structure. Seismic load was defined by lateral force method, modal response spectrum, non-linear time-history analysis and pushover analysis. The time-history analysis is represented by accelerograms. There were made linear and non-linear calculations.

An Energy Approach to Linearizing Squeeze-Film Damper Forces

1985 ◽  
Vol 199 (1) ◽  
pp. 57-63
Author(s):  
E J Hahn
Keyword(s):  
Parametric Design ◽  
Squeeze Film ◽  
Transient Solution ◽  
Equivalent Stiffness ◽  
Design Studies ◽  
Damping Coefficients ◽  
Squeeze Film Dampers ◽  
Non Linear ◽  
Linear Elements ◽  
Stiffness And Damping

Analyses of multi-degree of freedom rotor-bearing systems incorporating non-linear elements, such as squeeze-film dampers, generally necessitate time consuming transient solution. Consequently, it is often too expensive to carry out parametric design studies on such systems. This paper presents a general technique for linearizing the non-linear element forces using equivalent stiffness and damping coefficients with energy dissipation and energy storage-release concepts. The approach is illustrated and tested for both centrally preloaded squeeze-film dampers and for squeeze-film dampers without centralizing springs under a combination of unidirectional and unbalance loading. The results predicted by using such equivalent stiffness and damping coefficients agree quite well with those obtained from the full transient solution, even where the unidirectional load exceeds the dynamic load and the damper is operating at high eccentricity. An iterative procedure is proposed which, with the aid of such stiffness and damping coefficients, should significantly reduce the computation time presently needed to carry out parametric design studies on general multi-degree of freedom systems incorporating non-linear elements such as squeeze-film dampers.

PERILAKU STRUKTUR BAJA TIPE MRF DENGAN BEBAN LATERAL BERDASARKAN SNI 1726-2012 DAN METODE PERFORMANCE BASED PLASTIC DESIGN (PBPD)

2014 ◽  
Vol 13 (1) ◽  
Author(s):  
Nidiasari Jati Sunaryati Eem Ikhsan
Keyword(s):  
Pushover Analysis ◽  
Time History ◽  
Time History Analysis ◽  
Plastic Design ◽  
History Analysis ◽  
Non Linear ◽  
Static Pushover Analysis

Struktur rangka baja pemikul momen merupakan jenis struktur baja tahan gempa yang populer digunakan. Daktilitas struktur yang tinggi merupakan salah satu keunggulan struktur ini, sehingga mampu menahan deformasi inelastik yang besar. Dalam desain, penggunaan metode desain elastis berupa evaluasi non-linear static (Pushover analysis) maupun evaluasi non-linear analisis (Time History Analysis) masih digunakan sebagai dasar perencanaan meskipun perilaku struktur sebenarnya saat kondisi inelastik tidak dapat digambarkan dengan baik. Metode Performance-Based Plastic Design (PBPD) berkembang untuk melihat perilaku struktur sebenarnya dengan cara menetapkan terlebih dahulu simpangan dan mekanisme leleh struktur sehingga gaya geser dasar yang digunakan adalah sama dengan usaha yang dibutuhkan untuk mendorong struktur hingga tercapai simpangan yang telah direncanakan. Studi dilakukan terhadap struktur baja 5 lantai yang diberi beban gempa berdasarkan SNI 1726, 2012 dan berdasarkan metode PBPD. Hasil analisa menunjukkan bahwa struktur yang diberi gaya gempa berdasarkan metode PBPD mencapai simpangan maksimum sesuai simpangan rencana dan kinerja struktur yang dihasilkan lebih baik .

scholarly journals Identification of Dynamic Parameters of Pedestrian Walking Model Based on a Coupled Pedestrian–Structure System

2021 ◽  
Vol 11 (14) ◽  
pp. 6407
Author(s):  
Huiqi Liang ◽  
Wenbo Xie ◽  
Peizi Wei ◽  
Dehao Ai ◽  
Zhiqiang Zhang
Keyword(s):  
Negative Correlation ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Field Testing ◽  
The Body ◽  
Structural Vibration ◽  
Pedestrian Dynamics ◽  
Structure Interaction ◽  
Mass Spring ◽  
Stiffness And Damping

As human occupancy has an enormous effect on the dynamics of light, flexible, large-span, low-damping structures, which are sensitive to human-induced vibrations, it is essential to investigate the effects of pedestrian–structure interaction. The single-degree-of-freedom (SDOF) mass–spring–damping (MSD) model, the simplest dynamical model that considers how pedestrian mass, stiffness and damping impact the dynamic properties of structures, is widely used in civil engineering. With field testing methods and the SDOF MSD model, this study obtained pedestrian dynamics parameters from measured data of the properties of both empty structures and structures with pedestrian occupancy. The parameters identification procedure involved individuals at four walking frequencies. Body frequency is positively correlated to the walking frequency, while a negative correlation is observed between the body damping ratio and the walking frequency. The test results further show a negative correlation between the pedestrian’s frequency and his/her weight, but no significant correlation exists between one’s damping ratio and weight. The findings provide a reference for structural vibration serviceability assessments that would consider pedestrian–structure interaction effects.

scholarly journals Record-to-record variability and code-compatible seismic safety-checking with limited number of records

2021 ◽  
Author(s):  
Fatemeh Jalayer ◽  
Hossein Ebrahimian ◽  
Andrea Miano
Keyword(s):  
Seismic Hazard ◽  
Linear Time ◽  
Time History ◽  
Time History Analysis ◽  
Seismic Safety ◽  
Hazard Curve ◽  
History Analysis ◽  
Non Linear ◽  
Seismic Hazard Curve ◽  
Cloud Analysis

AbstractThe Italian code requires spectrum compatibility with mean spectrum for a suite of accelerograms selected for time-history analysis. Although these requirements define minimum acceptability criteria, it is likely that code-based non-linear dynamic analysis is going to be done based on limited number of records. Performance-based safety-checking provides formal basis for addressing the record-to-record variability and the epistemic uncertainties due to limited number of records and in the estimation of the seismic hazard curve. “Cloud Analysis” is a non-linear time-history analysis procedure that employs the structural response to un-scaled ground motion records and can be directly implemented in performance-based safety-checking. This paper interprets the code-based provisions in a performance-based key and applies further restrictions to spectrum-compatible record selection aiming to implement Cloud Analysis. It is shown that, by multiplying a closed-form coefficient, code-based safety ratio could be transformed into simplified performance-based safety ratio. It is shown that, as a proof of concept, if the partial safety factors in the code are set to unity, this coefficient is going to be on average slightly larger than unity. The paper provides the basis for propagating the epistemic uncertainties due to limited sample size and in the seismic hazard curve to the performance-based safety ratio both in a rigorous and simplified manner. If epistemic uncertainties are considered, the average code-based safety checking could end up being unconservative with respect to performance-based procedures when the number of records is small. However, it is shown that performance-based safety checking is possible with no extra structural analyses.

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