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1

Comparison of temperature dependence of internal damping of selected magnesium alloys

Oršulová Tatiana, Palček Peter, Uhríčik Milan

Production Engineering Archives

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2019

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Vol. 22

7--10

EN

The research is focused on the study of the temperature dependence of the internal damping of selected magnesium alloys with different contents of aluminium - AZ31 and AZ61. These alloys are currently widely used in various types of industry, mainly in the automotive industry. It belongs to a group of materials called HIDAMETS because they have excellent damping properties. The internal damping of the samples was measured on a unique ultrasonic device constructed at Žilina University in Žilina. Specimens were measured at baseline in the temperature range from 25 °C to 400 °C. Changes in internal damping caused by varying aluminium contents in investigated alloys were noted. As the aluminium content increases, maximum internal damping is achieved due to the formation, growth and subsequent dissolution of the continuous precipitate in the microstructure.

2

Development of identification procedure for the internal and external damping in a cracked rotor system undergoing forward and backward whirls

Roy Dipendra Kumar, Tiwari Rajiv

Archive of Mechanical Engineering

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2019

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Vol. LXVI, nr 2

229--255

EN

In the present work, a procedure for the estimation of internal damping in a cracked rotor system is described. The internal (or rotating) damping is one of the important rotor system parameters and it contributes to the instability of the system above its critical speed. A rotor with a crack during fatigue loading has rubbing action between the two crack faces, which contributes to the internal damping. Hence, internal damping estimation also can be an indicator of the presence of a crack. A cracked rotor system with an offset disc, which incorporates the rotary and translatory of inertia and gyroscopic effect of the disc is considered. The transverse crack is modeled based on the switching crack assumption, which gives multiple harmonics excitation to the rotor system. Moreover, due to the crack asymmetry, the multiple harmonic excitations leads to the forward and backward whirls in the rotor orbit. Based on equations of motions derived in the frequency domain (full spectrum), an estimation procedure is evolved to identify the internal and external damping, the additive crack stiffness and unbalance in the rotor system. Numerically, the identification procedure is tested using noisy responses and bias errors in system parameters.

3

Effect of cyclic loading on the internal damping of magnesium alloy AZ31

Uhricik M., Dresslerova Z., Palcek P.

Production Engineering Archives

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2017

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Vol. 15

7--10

EN

The article focuses on the analysis of the internal damping changes depending on the amplitude of the magnesium alloy AZ31. Internal damping reflects the ability of the material irreversibly dissipating mechanical energy oscillations. It means that the material of high internal damping ability is able to significantly reduce the vibration amplitude. Internal damping is, generally, dependent on many factors (temperature, material purity, grain size, mechanical and thermal processing, etc.) and its value is determined by interactions between various mechanisms dissipation of mechanical energy. Ultrasonic resonance method was used in experimental measurements, which is based on continuous excitation of oscillations of the specimen, and the entire apparatus vibrates at a frequency which is near to the resonance. Starting resonance frequency for all measurements was about f = 20470 Hz.

4

Influence of Internal and Constructional Damping on Vibrations of Telescopic Boom of Truck Crane

Sochacki W., Bold M.

Machine Dynamics Research

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2014

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Vol. 38, No. 4

51-58

EN

This study formulates and solves the problem of transverse damped vibrations in a crane boom of a truck-mounted crane. Dissipation of vibration energy in the model adopted in the study occurs as a result of internal damping of the viscoelastic material (rheological Kelvin-Voigt model) of the beams that model the system and motion resistance in slides between the moving components of the crane boom. Damped frequencies of vibrations and degree of amplitude decay were calculated. The study also presents eigenvalues of system vibration with respect to changes in damping coefficients and system geometry for selected rigidity of springs.

5

Wpływ tłumienia wewnętrznego elementów kompozytowych na charakterystyki amplitudowo-częstotliwościowe modelu zawieszenia samochodu

Przybyłowicz P., Fudała W.

Symulacja w Badaniach i Rozwoju

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2012

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Vol. 3, nr 2

89--97

PL

W pracy zaprezentowano nowe rozwiązanie układu zawieszenia samochodów. Zastosowano w nim wahacze kompozytowe, które nie tylko mają zadanie prowadzenia koła ale także są elementem sprężystym. W kompozytach występuje stosunkowo duże tarcie wewnętrzne. Zależy ono między innymi od kąta laminowania włókien w poszczególnych warstwach kompozytu. W pracy wyznaczono współczynniki tłumienia dla trzech wybranych zastępczych belek o różnych kątach laminowania. Następnie otrzymane wyniki posłużyły do analizy modelu samochodu o 4 stopniach swobody. Przeanalizowano wpływ tłumienia wewnętrznego występującego w belce na charakterystyki czasowe modelu samochodu.

EN

The paper presents a new approach to the problem of vehicle suspension system. It makes use of composite wishbones which not only control the geometry but also act as spring elements. The composites have relatively high internal friction properties. They depend, among other, on the angle of fiber lamination in the layers. Damping coefficients were determined for three equivalent composite beams with different lamination angles. Then the results were used to analyse the car model with 4 degrees of freedom. The influence of internal damping of the beam on the car model characteristic was presented.

6

Drgania siłownika hydraulicznego z uwzględnieniem tłumienia wewnętrznego

Sochacki W.

Modelowanie Inżynierskie

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2011

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T. 10, nr 41

371-376

PL

W pracy sformułowano i rozwiązano zagadnienie tłumionych drgań poprzecznych siłownika hydraulicznego. W zbudowanym modelu fizycznym uwzględniono rozproszenie energii w drgającym siłowniku na skutek tłumienia wewnętrznego materiału lepkosprężystego siłownika (model reologiczny Kelvina-Voigta). Obliczenia przeprowadzono po przyjęciu odpowiednich wielkości bezwymiarowych. Jako przykład przyjęto siłownik podpory górniczej. Wyniki obliczeń dotyczą wyznaczenia zależności pierwszej wartości własnej drgań poprzecznych siłownika od stopnia jego rozsunięcia przy dwóch wartościach obciążenia. Przedstawiono także wpływ wielkości tłumienia wewnętrznego na pierwszą wartość własną układu.

EN

In the work the problem of transverse vibrations of a hydraulic cylinder set with the consideration of the internal damping is formulated and solved. In the physical model of hydraulic cylinder the dissipation of vibration energy as the result of internal viscous damping (a visco-elastic Kelvin-Voigt material) is considered. The calculations is made after consideration pertinent dimensionless quantities. The results of calculations concern the assign of dependence of first eigenvalue (real and imaginary parts) for two values of loading from degree of hydraulic cylinder extension. The influence of size of internal damping on the first eigenvalue of system also was introduced.

7

The temperature dependence of internal damping and elastic modulus of Mg alloy

Kasencak M., Palcek P., Blazek D.

International Journal of Applied Mechanics and Engineering

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2010

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Vol. 15, no 2

329-333

EN

In this work, the experimentally determined changes of internal damping of magnesium alloy AZ31 and the relative changes of the elastic modulus are presented. The changes of internal damping for the basic material in the temperature range 30-450 C were measured. Increase of the damping properties of magnesium alloy AZ31 about high temperatures is caused by the movement of the binary point defects activated by the temperature during the solidification of the dendritic structure.

8

Internal damping of magnesium alloys

Palček P., Kasenčák M., Chalupová M., Bokůvka O.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Nauki Techniczne

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2009

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Z. 13

346--353

EN

The paper deals with experimentally determined curves of AZ 31 magnesium alloys internal damping in dependence on temperature. The curves of damping are mutually compared: the initial state of the alloy (i.e. not heat treated alloy) and after heat treatment (homogenic annealing). In both cases the maxims of damping were recorded which are caused by relaxation process in material. It was found out that the values of damping of heat treated alloy are approximately 3 times higher than in the case of initial state. Elastic-plastic behaviour of AS41 magnesium alloy was investigated using the amplitude dependence at two chosen temperatures: T1 – room temperature and T2 – 250oC.

9

Effect of a rotational spring support on the stability of a column with internal damping

Przybylski J.

Vibrations in Physical Systems

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2004

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Vol. 21

315--318

EN

This work concerns the problem of stability of a geometrically non-linear damped column loaded by a partially follower force. One end of the column is supported by a rotational spring of stiffness, which can be changed as a function of the external load. The loss of stability of such system is of flutter or divergence type what depends on the values of spring rigidity and follower parameter. The limit of stability has been established on the basis of kinetic criterion. For a nonconservative system an adjoint problem has been formulated. Lyapunow stability criterion has been complemented by Suguyama consideration concerning the time of achieving of demanded displacement by a chosen point on the vibrating column.

10

Non-linear dynamic analysis of an axialy moving viscoelastic beam

Marynowski K.

Journal of Theoretical and Applied Mechanics

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2002

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Vol. 40 nr 2

465-482

EN

Stability and oscillation characteristics of an axially moving beam have been investigated. Two different models of the beam material, i.e., Kelvin-Voigt and Maxwell have been considered. The numerical solutions of full nonlinear and linearized equations have been compared. The effects of axially traveling speed and the internal damping on dynamical stability of the axially moving beam have been studied in details. Numerical studies of the Kelvin-Voigt and Maxwell models show that both models give similar results only for small values of the internal damping (dimensionless internal damping coefficient smaller than ...). For materials with larger damping coefficient the considered models give different results.

PL

W pracy badano stateczność dynamiczną ruchu oraz drgania przesuwającej się osiowo belki. Do opisu własności materiału belki zastosowano dwa modele reologiczne: model Kelvina-Voigta oraz model Maxwella. Dla obu badanych modeli wyprowadzono nieliniowe równania różniczkowe o pochodnych cząstkowych opisujące ruch poprzeczny belki. Przybliżone rozwiązanie równań ruchu otrzymano stosując metodę Galerkina. Badania numeryczne przeprowadzono dla modelu belkowego przesuwającej się osiowo cienkiej wstęgi stalowej. Badano wpływ prędkości przesuwu oraz tłumienia wewnętrznego na stateczność dynamiczną układu. Wyniki badań wskazują, że tylko przy małych wartościach bezwymiarowego współczynnika tłumienia wewnętrznego ... układy z obydwoma badanymi modelami reologicznymi charakteryzują się podobnym zachowaniem dynamicznym. Przy wyższym tłumieniu wewnętrznym otrzymano różniące się wyniki badań dynamiki zarówno układu zlinearyzowanego, jak i układu nieliniowego.

11

Internal damping effect on the dynamic stability of axially moving web model

Marynowski K.

Mechanics and Mechanical Engineering

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2000

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Vol. 4, nr 2

291--296

EN

Dynamic investigations of string-like and beam-like models of axially moving web are carried out in this paper. The string model material as the Bűrgers element, and the beam model material as the Kelvin - Voigt element are considered. The results of numerical investigations show the solutions of the linearized and non-linear problems. Numerical results show axially traveling speed and internal damping effects on dynamic stability of axially moving web model.