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Number of results: 164
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Abstract

In this stud y, we attempt to analyse free nonlinear vibrations of buckling in laminated composite beams. Two new methods are applied to obtain the analytical solution of the nonlinear governing equation of the problem. The effects of different parameters on the ratio of nonlinear to linear natural frequencies of the beams are studied. These methods give us an agreement with numerical results for the whole range of the oscillation amplitude.

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Authors and Affiliations

G. Abdollahzadeh
M. Ahmadi
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Abstract

Laplace Transform is often used in solving the free vibration problems of structural beams. In existing research, there are two types of simplified models of continuous beam placement. The first is to regard the continuous beam as a single-span beam, the middle bearing of which is replaced by the bearing reaction force; the second is to divide the continuous beam into several simply supported beams, with the bending moment of the continuous beam at the middle bearing considered as the external force. Research shows that the second simplified model is incorrect, and the frequency equation derived from the first simplified model contains multiple expressions which might not be equivalent to each other. This paper specifies the application method of Laplace Transform in solving the free vibration problems of continuous beams, having great significance in the proper use of the transform method.

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Authors and Affiliations

H.B. Wen
T. Zeng
G.Z. Hu
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Abstract

People living in buildings may be exposed to dynamic actions. In the diagnosis and design of buildings there is an increasing need of taking into account these activities and verification of compliance of the building requirements for vibration comfort of people residing in buildings. This study presents the results of analysis of such criteria in the following standards: Polish PN-88/B-02171 [1], British BS 6472-1 [2], German DIN 4150 [3], and ISO international standards [4,5]. Basing on the results of this analysis and on the review of selected items of literature, the application of standards recommendations in diagnosis and design of buildings, as well as areas for further research on this subject is indicated. This article is an extended version of the conference paper [6] presented on the conference Urban Transport 2011.

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Authors and Affiliations

J. Kawecki
A. Kowalska
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Abstract

Latest developments in international standardization of whole-body and hand-arm vibration are pre- sented. In addition, two German projects are presented that might have impact on international work programs in the next years.
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Authors and Affiliations

Martin Liedtke
Jörg Rissler
Uwe Kaulbars
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Abstract

In the paper, the authors describe and solve the problem of optimum control of selected vibration forms in mechanical systems. Two illustrative examples have been used to present the procedure for determination of the optimum controller coefficients.

In the first example, a simplified mechanical system is considered, while in the second one – a rotor with magnetic bearing. In both cases, the integral performance indices have been defined in order to minimize the vibration level at selected points of the structures.

The system with the magnetic bearing is structurally unstable. For this reason, the authors present the way of finding the weight coefficients of integral performance index for unstable, multi-degrees-of-freedom system. In that way, the selected modal forms attain the previously assumed dynamic properties and the performance index takes the minimum value. The results of numerical analysis show that the proposed way is efficient and makes it possible to control selected forms of vibration in the system.

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Authors and Affiliations

Edmund Wittbrodt
Rafał Hein
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Abstract

In this paper, the authors consider the influence of axial load on the stability of shells of revolution subjected to external pressure. Shells of different geometry are investigated with emphasis to barrelled shells. The variable quantities are length L and meridional radius of curvature R1 of a shell. The constant parameters are: thickness of the shell h, mass ms and reference radius r0. The material of shells is steel. Numerical calculations were performed in the ABAQUS system. All the shells considered in this paper were subjected to axial compression to determine the force corresponding to the loss of stability in such conditions. A part of this force is then used to preload shell before the buckling analysis in the conditions of external pressure is started. The buckling shapes for shells of different geometry are presented with and without the influence of axial load. The ability of controlling the buckling strength and shape is discussed.

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Authors and Affiliations

Paweł Jasion
Krzysztof Magnucki
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Abstract

In the paper, the authors describe the method of reduction of a model of rotor system. The proposed approach makes it possible to obtain a low order model including e.g. non-proportional damping or the gyroscopic effect. This method is illustrated using an example of a rotor system. First, a model of the system is built without gyroscopic and damping effects by using the rigid finite element method. Next, this model is reduced. Finally, two identical, low order, reduced models in two perpendicular planes are coupled together by means of gyroscopic and damping interaction to form one model of the system. Thus a hybrid model is obtained. The advantage of the presented method is that the number of gyroscopic and damping interactions does not affect the model range.

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Authors and Affiliations

Rafał Hein
Cezary Orlikowski
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Abstract

The problem of influence of mechanical vibrations on a measurement is well known and analyzed for ground conditions. However, the problem becomes quite essential and difficult to solve in space conditions. The influence of vibrations on accuracy of the measurement was observed on MIPAS – ENVISAT and in PFS Mars Express.

This paper presents an experimental and theoretical investigation on sensitivity to mechanical disturbances of the Fourier-transform infrared spectrometer PFS.

A theoretical analysis has been performed in order to highlight the expected effect of the vibration, then laboratory tests have been designed and carried out for instrument characterization.

The theoretical investigation has been confirmed by experimental tests.

The data were distorted by errors that reflect the influence of vibrations on the instrument and temperature instability of the reference source.

The considerations are a perfect example presenting the scale of vibrations problem and the instability of the reference source in assessing accuracy of the measurement in space.

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Authors and Affiliations

R. Pietrzak
M. Rataj
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Abstract

Reducing the effect of unwanted vibrations is an important topic in many engineering applications. In this paper we describe some recent developments in the area of passive vibration mitigation. This is based on a new device called the inerter which can be exploited in a range of different contexts. In this paper we consider two recent examples; (i) where a flywheel inerter is combined with a hysteretic damper, and (ii) in which a pivoted bar inerter is developed for a machining application. In both cases, experimental test results show that the devices can outperform existing methods.
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Authors and Affiliations

David J. Wagg
1
ORCID: ORCID

  1. Department of Mechanical Engineering, University of Sheffield, Sheffield, United Kingdom
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Abstract

The problem of transmitting vibrations with audible frequencies by steel springs, constituting the vibration isolation system was considered in this paper. The analytical relationships allowing determining the value of the transmissibility for the springs resonance frequencies responsible for the transmissibility of high frequency vibrations have been derived and checked by means of FEM method. Also the occurrence of the increasing stresses in the springs in the areas between the resonances has been shown. The typical system, i.e. the serial system with rubber cushion, has been analyzed, reducing the transmission of high frequency vibrations by the spring. It has been shown that the transmission is reduced not as a result of differences in the wave impedance of the boundary of both media but due to the increased dispersion of energy in the rubber, and the analytical relationships allowing the evaluation of the effectiveness of this method have been derived.
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Authors and Affiliations

Jerzy Michalczyk
Leszek Majkut
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Abstract

The paper deals with a study of relations between the measured Ra, Rq, Rz surface roughness parameters, the traverse speed of cutting head v and the vibration parameters, PtP, RMS, vRa, generated during abrasive water jet cutting of the AISI 309 stainless steel. Equations for prediction of the surface roughness parameters were derived according to the vibration parameter and the traverse speed of cutting head. Accuracy of the equations is described according to the Euclidean distances. The results are suitable for an on-line control model simulating abrasive water jet cutting and machining using an accompanying physical phenomenon for the process control which eliminates intervention of the operator.
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Authors and Affiliations

Pavol Hreha
Agata Radvanska
Lucia Knapcikova
Grzegorz M. Królczyk
Stanisław Legutko
Jolanta B. Królczyk
Sergej Hloch
Peter Monka
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Abstract

The article is a continuation of the authors’ elaboration (Dąbrowski, Dziurdź, 2016). The aim of this continuation is to prove that a proposed way of modelling and using the coherent analysis to filter nonlinear disturbances is a useful technique in vibroacoustic diagnostics. The thesis was proved by solving the task of diagnosing the damage of the gear of the car gearbox on the basis of the measurement of mechanical vibrations and the noise in the engine chamber.

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Authors and Affiliations

Zbigniew Dąbrowski
Jacek Dziurdź
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Abstract

Contemporary tools which help to design technical objects refer to the conclusions drawn from studying the changes of physical processes accompanying the exploitation, especially to vibroacoustic processes. The main problem is to define such vibroacoustic measures, where their changes would model the analyzed physical phenomena in the best way. Basing on simple indicators which refer to occurring phenomena, it is possible to obtain accurate solutions with a satisfactory reliance level without using complex computing techniques needing detailed descriptors. According to the author, the indicators which are based on the analysis of vibroacoustic energy propagation are very useful in solving engineering problems. These indicators are useful while diagnosing the condition of technical systems, identifying and minimizing the vibroacoustic risks. The possibilities of using such indicators in order to find design solution are illustrated by sample results of the research of the structures with vibroacoustic elements which reduce the noise of rail vehicles by the rail vibration damping.
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Authors and Affiliations

Grzegorz Klekot
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Abstract

A gear system transmits power by means of meshing gear teeth and is conceptually simple and effective in power transmission. Thus typical applications include electric utilities, ships, helicopters, and many other industrial applications. Monitoring the condition of large gearboxes in industries has attracted increasing interest in the recent years owing to the need for decreasing the downtime on production machinery and for reducing the extent of secondary damage caused by failures. This paper addresses the development of a condition monitoring procedure for a gear transmission system using artificial neural networks (ANNs) and support vector machines (SVMs). Seven conditions of the gear were investigated: healthy gear and gear with six stages of depthwise wear simulated on the gear tooth. The features extracted from the measured vibration and sound signals were mean, root mean square (rms), variance, skewness, and kurtosis, which are known to be sensitive to different degrees of faults in rotating machine elements. These characteristics were used as an input features to ANN and SVM. The results show that the multilayer feed forward neural network and multiclass support vector machines can be effectively used in the diagnosis of various gear faults.

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Authors and Affiliations

Muniyappa Amarnath
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Abstract

In this paper a cross-shaped isolator consisting of cuboidal magnets and a cylindrical isolator are compared by resonance frequency to volume ratio and shape. Both isolators are capable of obtaining a low resonance frequency, i.e. 0.15 Hz and 0.01 Hz for the cross and cylinder, respectively. The volume of both isolators is comparable, only the shape is different, resulting in a tall structure with a small footprint for the cross and a flat with a large diameter cylindrical structure. A sensitivity analysis shows that due to the large amount of magnets, the cross-shaped isolator is less sensitive to manufacturing tolerances.

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Authors and Affiliations

D.T.E.H. Van Casteren
J.J.H. Paulides
E.A. Lomonova
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Abstract

In the paper, the authors discuss the possibility to apply the "Nodalised Beam" method for vibroinsulation of manually operated tools. They indicate the difficulties in applying the original method for this purpose. On the bases of the reciprocity principle, the authors propose a method for modifying the system that allows them to avoid the mentioned disadvantages. Equations derived for the modified system that makes it possible to define the position of nodal points. The relations were verified at a test station. Furthermore, a method of tuning the system was proposed.
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Authors and Affiliations

Leszek Majkut
Jerzy Michalczyk
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Abstract

The paper introduces a new design of a platform mechanism with 6 DOF. The platform is supported on three active legs, each equipped with two rotating drives. The mechanism can be used in active vibration control systems. The values of drive angular velocities are precisely controlled, so that the transmission of the base vibrations onto the platform could be minimal. The values of drive torques to be generated are determined. The mechanism was modelled using the Working Model® 30. The effects of active vibration control are also presented.
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Authors and Affiliations

Grzegorz Tora
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Abstract

Manufacturing by casting method in aluminum and its alloys is preferred by different industries today. It may be necessary to improve the mechanical properties of the materials according to different industries and different strength requirements. The mechanical properties of metal alloys are directly related to the microstructure grain sizes. Therefore, many grain reduction methods are used during production or heat treatment. In this study, A356 alloys were molded into molds at 750 °C and exposed to vibration frequency at 0, 8.33, 16.66, 25, and 33.33 Hz during solidification. Optical microscopes images were analyzed in image analysis programs to measure the grain sizes of the samples that solidified after solidification. In addition, microhardness tests of samples were carried out to examine the effect of vibration and grain reduction on mechanical behavior. In the analyzes made, it was determined that the grain sizes decreased from 54.984 to 26.958 μm and the hardness values increased from 60.48 to 126.94 HV with increasing vibration frequency.
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Bibliography

[1] Mondolfo, L.F. (1979). Aluminium Alloys Structures and Properties. London: Butterworths, 806.
[2] Kocatepe, K. & Burdett, C.F. (2000) Effect of low frequency vibration on macro and micro structures of LM6 alloys. Journal of Materials Science, 35(13), 3327-3335. https://doi.org/10.1023/A:1004891809731.
[3] Schaffer, P.L. & Dahle, A.K. (2005). Settling behaviour of different grain refiners in aluminium. Materials Science and Engineering. A, 413, 373-378. https://doi.org/10.1016/j.msea.2005.08.202.
[4] Kumar, P.S., Abhilash, E., Joseph, M.A. (2010). Solidification under mechanical vibration: variation in metallurgical structure of gravity die cast A356 aluminium alloy. In International Conference on Frontiers in Mechanical Engineering (FIME), 20-22 May 2010 (pp. 140-146). India.
[5] Taghavi, F., Saghafian, H. & Kharrazi, Y.H. (2009). Study on the effect of prolonged mechanical vibration on the grain refinement and density of A356 aluminum alloy. Materials & Design. 30(5), 1604-1611. https://doi.org/10.1016/j.matdes.2008.07.032.
[6] Hernandez, F.R. & Sokolowski, J.H. (2006). Comparison among chemical and electromagnetic stirring and vibration melt treatments for Al–Si hypereutectic alloys. Journal of Alloys and Compounds. 426(1-2), 205-212. https://doi.org/10.1016/j.jallcom.2006.09.039.
[7] Jian, X., Meek, T.T. & Han, Q. (2006). Refinement of eutectic silicon phase of aluminum A356 alloy using high-intensity ultrasonic vibration. Scripta Materialia. 54(5), 893-896. https://doi.org/10.1016/j.scriptamat.2005.11.004.
[8] Chirita, G., Stefanescu, I., Soares, D. & Silva, F.S. (2009). Influence of vibration on the solidification behaviour and tensile properties of an Al–18 wt% Si alloy. Materials & Design. 30(5), 1575-1580. https://doi.org/10.1016/ j.matdes.2008.07.045.
[9] Promakhov, V.V., Khmeleva, M.G., Zhukov, I.A., Platov, V.V., Khrustalyov, A.P., & Vorozhtsov, A.B. (2019). Influence of vibration treatment and modification of A356 aluminum alloy on its structure and mechanical properties. Metals. 9(1), 87. https://doi.org/10.3390/met9010087.
[10] Selivorstov, V., Dotsenko, Y. & Borodianskiy, K. (2017). Influence of low-frequency vibration and modification on solidification and mechanical properties of Al-Si casting alloy. Materials. 10(5), 560. https://doi.org/10.3390/ma10050560.
[11] Yüksel, Ç. (2018). Titreşimli katilaştirmanin birincil ve ikincil Al7Si0, 3mg alüminyum alaşimlarinin içyapisina etkisi. Niğde Ömer Halisdemir Üniversitesi Mühendislik Bilimleri Dergisi. 7(2), 986-992.
[12] Sulaiman, S. & Zulkifli, Z.A. (2018). Effect of mould vibration on the mechanical properties of aluminium alloy castings. Advances in Materials and Processing Technologies. 4(2), 335-343. https://doi.org/10.1080/ 2374068X.2017.1421737.
[13] Y. Seetharama Rao, Rajana Vara Prasad, Sri Ram Murthy Paladugu (2019). Experimental investigations of microstructure and mechanical properties of aluminium alloy using vibration mold. Journal of Recent Activities in Production e-ISSN: 2581-9779. 4(2), 25-34.
[14] ASM International Handbook Committee. (1990). ASM Handbook, Volume 02 - Properties and Selection: Nonferrous Alloys and Special-Purpose Materials. ASM International.
[15] Kocatepe, K. (2007). Effect of low frequency vibration on porosity of LM25 and LM6 alloys. Materials & Design. 28(6), 1767-1775. https://doi.org/10.1016/ j.matdes.2006.05.004.
[16] Naik, S.N., & Walley, S.M. (2020). The Hall–Petch and inverse Hall–Petch relations and the hardness of nanocrystalline metals. Journal of Materials Science. 55(7), 2661-2681. https://doi.org/10.1007/s10853-019-04160-w.
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Authors and Affiliations

Taha Süreyya Özgü
1
ORCID: ORCID
Recep Çalın
1
ORCID: ORCID
Naci Arda Tanış
1
ORCID: ORCID

  1. Kırıkkale University, Turkey
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Abstract

The present paper addresses the analysis of structural vibration transmission in the presence of structural joints. The problem is tackled from a numerical point of view, analyzing some scenarios by using finite element models. The numerical results obtained making use of this process are then compared with those evaluated using the EN 12354 standard vibration reduction index concept. It is shown that, even for the simplest cases, the behavior of a structural joint is complex and evidences the frequency dependence. Comparison with results obtained by empirical formulas reveals that those of the standards cannot accurately reproduce the expected behavior, and thus indicate that alternative complementary calculation procedures are required. A simple methodology to estimate the difference between numerical and standard predictions is here proposed allowing the calculation of an adaptation term that makes both approaches converge. This term was found to be solution-dependent, and thus should be evaluated for each structure.

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Authors and Affiliations

Jaime Ramis
Enrique Segovia
Jesús Alba
Jesús Carbajo
Luís Godinho
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Abstract

A dynamic economy contributes to the increase in the number of workers exposed to mechanical vibration caused by machines and transport equipment. As the means of transport are insufficiently recognised sources of mechanical vibrations, this article presents the results of whole-body and hand-arm vibration tests of 30 most common means of in-house transport. An analysis of vibration signals recorded at each workstation according to PN-EN 14253 and PN-EN ISO 5349 made it possible to determine the weighted values of components of directional vibration acceleration and the values of daily vibration exposure A(8).

In order to assess exposure to whole-body and hand-arm vibration at the tested workstations of in-house transport, indices of vibration hazard related to admissible values, the total evaluation index (developed in a previous study at CIOP-PIB) and a three-degrees scale for assessing exposure to vibrations were used. The assessment showed that the workstations were a major hazard. Vibration hazards at all those workstations were classified as either medium or high.

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Authors and Affiliations

Piotr Kowalski
Jacek Zając
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Abstract

The reduction of structural vibrations on the example of two pedestrian bridges (in Poznań and Wrocław) with using of tuned mass dampers (TMD) has been presented in the paper. The results of theoretical and experimental studies of pedestrian bridge vibrations has been described and discussed. Basing on the results of calculations and measurements, tuned mass dampers (TMD) has been designed and mounted in the structure of the bridges. The measurements after the assembly of TMD show a high efficiency of vibration damping.

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Authors and Affiliations

Wiesław Fiebig
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Abstract

In spite of the fact that standardizing operations and increased awareness of hazards led to a significant improvement of vibroacoustic climate of operator’s stands of new machines, their long-term operation - often under difficult conditions - leads to a fast degradation of acoustic qualities of machines. Temporary operations performed during surveys and periodical overhauls are rarely effective, due to the lack of any guidelines. In this situation the authors propose the algorithm for selection of eventual screens or sound absorbing and sound insulating partitions, utilizing the measuring procedure aimed at identification, at the operator’s stand, of main noise components originated from various sources. On the basis of this procedure, the vibroacoustic energy propagation paths in the machine was estimated.
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Authors and Affiliations

Zbigniew Dąbrowski
Jacek Dziurdź
Radosław Pakowski
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Abstract

The acoustic properties of the sitar string are studied with the aid of a physical model. The nonlinearity of the string movement caused by the bridge acting as an obstacle to the vibrating string is of special interest. Comparison of the model's audio output to recordings of the instrument shows interesting similarities. The effects dispersion and bridge have on the sound of the instrument are demonstrated in the model.

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Authors and Affiliations

Sadjad Siddiq

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