Wyniki wyszukiwania - BazTech

1

Experimental research on the vibration characteristics of canvas and primed canvas of paintings

Gao Yulong, Ziegler Pascal, Heinemann Carolin, Hartlieb Eva, Eberhard Peter

Archive of Mechanical Engineering

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2023

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LXX, nr 3

333--350

EN

Paintings inevitably bear severe mechanical loads during transportation.Understanding the dynamic characteristics of paintings helps to avoid damage during transportation and to effectively slow down their aging.In this contribution, the vibration characteristics of canvas and primed canvas of paintings and their influencing factors are studied experimentally.For this reason, two dummy paintings with canvas in a common orientation and a tilted orientation are investigated, and an experimental setup using an excitation mechanism and a laser Doppler vibrometer is developed.In order to avoid changes of the modal parameters related to humidity or temperature, all experiments were conducted in a climate box.The modal parameters of dummy paintings are identified by means of experimental modal analysis.Also, the difference in modal properties of the two dummy paintings before and after applying the primer are compared.The identified modal parameters are used to reconstruct their eigenmodes.From the identified modal parameters a numerical model is derived, which is then compared to measurements.The comparison shows a good agreement, hence is a hint for the correctness of assuming a modal structure and the quality of the modal parameter identification.Lastly, with the help of the climate box, the influences of humidity and temperature on the eigenfrequencies of dummy paintings are studied.

2

Parametric analysis of the whole loading process of translation-torsion coupled vibration characteristics of the multi-layer bi-directional eccentric frame structure

Kuang Yuping, Liu Yanshan

Journal of Theoretical and Applied Mechanics

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2022

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Vol. 60 nr 3

479--494

EN

Earthquake investigations confirm that irregular structures suffer more damage than their symmetric counterparts. The vibration mode of irregular structures is affected by the cou- pling of lateral and torsional vibration characteristics. The analysis of the lateral-torsional coupling effect is mainly limited to unidirectional eccentric structure or single-layer eccentric design. To fill this gap, this paper presents a parametric study of the whole loading pro- cess, exploring lateral-torsional coupling vibration characteristics of multi-layer bi-directional eccentric structures. The performed nonlinear static analysis revealed that the natural fre- quency of eccentric frames with different layers exhibited a general pattern with a three-stage evolution from elastic to elastic-plastic stages. Accordingly, three different elastic-plastic de- velopment stages of parametric analysis were defined. The effects of the uncoupled torsion-to- -lateral frequency ratios Ω and stiffness eccentricities on the translation-torsion coupled vi- bration characteristics in the above three stages were simulated via self-compiled programs on the MATLAB platform. The results obtained show that the range of Ω controlling the vibration characteristics was related to the eccentricities. Therefore, it was proposed to set different limit values of Ω in designing and analyzing the structures with different bi- directional eccentric degrees. At Ω = 1.1 ∼ 1.2, the coupling effect between bi-directional eccentricities led to transformation between the first- and second-order vibration modes, while the direction with the lowest lateral stiffness could not be directly judged as the structure first-order principal vibration direction. In the third stage, when the bi-directional eccentricities reached or even exceeded 0.3, the second and third modes transformed into each other.

3

Vibration analysis of ball bearing considering waviness under high speed and an axial load

Hou P. P., Wang L. Q., Peng Q. Y.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2020

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Vol. 68, nr 3

517--527

EN

Based on the rolling bearing vibration measurement principle in ISO standard, a nonlinear dynamic model of ball bearing is built and motion equations of the inner ring, outer ring, and rolling elements are derived by using Lagrange’s equation. The ball bearing model includes the influence of waviness, rotational speed, external load, arbor supporting stiffness and arbor eccentricity. Ball bearing high-speed vibration tests are performed and used to verify the theoretical results. Simulated results showed that specific waviness orders produced the principal frequencies that were proportional to rotational speed. Rotational speed mainly affected the value of the natural frequency of the bearing system, and RMS (Root Mean Square) of the full band had a great fluctuation with the increase of rotational speed. In the experiment, spectrum and RMS of 2 ƒs-30 kHz (ƒs : the rotational frequency of inner ring/arbor) under high speed could include not only the influence of rotational speed but also principal frequencies produced by waviness, which could cover the part of requirements of the standard bearing vibration measurement.

4

Razrabotka matematiceskoi modeli sobstvennyh castot kolebanii cilindrovyh vtulok sudovogo dizela

Valishin A., Adamkiewicz A.

Zeszyty Naukowe / Akademia Morska w Szczecinie

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2014

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nr 40 (112)

31--36

EN

This paper presents the results of analytical studies on determination of vibration characteristics of cylinder liners of diesel engines based on the development and application of mathematical models. Mathematical relationships for cyclic deformations in a longitudinal cylinder sleeve for circumferential and radial directions have been developed. Sufficient convergence of the model with the results of practical measurements given in the literature has been shown.

5

Study on transformer tank vibration characteristics in the field and its application

Shengchang J., Lingyu Z., Yanming L.

Przegląd Elektrotechniczny

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2011

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R. 87, nr 2

205-211

EN

Vibration signal analysis method is one of effective methods to monitor the condition of transformer windings and core. In this paper, the multi-channels vibration measurement system is set up and the vibration signals on the oil-tank surface of running transformer in the field are measured. The influences of transformer type and sensor positions on the measured vibration signals are analyzed. The results show that, the same type of transformer' oil tank vibration signals have almost same characteristics, and the vibration signals measured on a transformer tank surface have similar characteristics only at the same position of phase "A" (or "a") and "C" (or "c"). Moreover, the attachment position of each sensor should be marked on the tank surface with paint, which is the reference position in the next measurement. It was recommended that the permissible error in the position of the sensor is within 5 cm. The vibration characteristics acquired in the field are applied to diagnose a transformer suffered three-phase short circuit, and the results presented show the accuracy and efficiency of the acquired transformer tank vibration characteristics.

PL

Analiza sygnału wibracji jest jedną z metod monitorowania stanu uzwojeń. i rdzenia transformatora. W artykule zastosowano wielokanałowy analizator wibracji do badania pracującego transformatora. Analizowano wpływ pozycji czujnika dla różnych typów transformatora. Stwierdzono, że sygnały wibracji miały podobny charakter dla jednego rodzaju transformatora i że sygnały są podobne dla tej samej pozycji czujnika. Rekomendowane jest więc zaznaczanie pozycji czujnika (z tolerancją. 5 cm) dla otrzymania powtarzalności pomiarów. Otrzymane sygnały wibracji mogą być wtedy wykorzystywane do diagnostyki.

6

Study on the experiments of the relationship between the geometric dimensions of flexural vibration disk and its vibration characteristics

Yuan Y., Ma Y., Chen M., Wang D., Zhao B.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 18, nr 1-2

255--258

EN

Purpose: The vibration characteristics of flexural vibration disk in ultrasonic honing system were studied systematically through experiments. Design/methodology/approach: The vibration of flexural vibration disk was tested using the acoustic system of ultrasonic honing. Findings: The results showed that the amplitude of vibration disk increases with the reducing of its thickness, when the disk was thin disk (the ratio between the thickness and radius was less than or equal to one fifths) the vibration of disk was flexural vibration, the good vibration effect could be obtained. The maximal amplitudę could reach 20.5μm,at the same time, the number of the wave crests and size could be obtained. There exist amplifying characteristics in the vibration of the disk. When the diameter of disk was not changed, the resonant frequency would decrease with the reducing of the thickness of disk. The resonance could be excited at different frequencies. The corresponding maximal amplitude value provides certain reference value for the dimensional design and application of flexural vibration disk. Research limitations/implications: From analysis, the ratio between diameter and thickness of flexural vibration disk has direct effect on amplitude. The rational diameter and thickness of flexural vibration disk should be selected according to specific machining conditions and the size requirements of the whole honing equipment during the course of design of ultrasonic honing acoustic system. Originality/value: The studied on relationship between geometric dimensions of flexural vibration disk and its vibration characteristics were made.