DYNAMIC PROPERTIES OF HIGH DAMPING METALS

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DYNAMIC PROPERTIES OF HIGH DAMPING

METALS

U. Vandeurzen, H. Verelst, R. Snoeys, L. Delaey

To cite this version:

CoZloque suppZ6ment au nOIO, Tome 42, octobre 1981

DYNAMIC PROPERTIES OF HIGH DAMPING METALS

e

U. Vandeurzen, H. Verelst, R. Snoeys and L. ~elaey"

Department of Mechanical Engineering and

* ~ e ~ a r t m e n t of MetaZZurgg, Kaatholieke Universiteit Leuven, BeZgim

Introduction.

-

An experimental procedure to determine the material parameters, elastic modulus and loss factor of high damping metals, is presented. Most other measuring techniques which are based on bending or torsion of the test specimen, determine element or system parameters which depend not only on the material but also on the size, shape, as well as on the stress amplitude and stress distribution

I

brought about by the method of loading. The procedure discussed ili this paper is based on Fourier Analysis and has as important features the uniform stress distri- bution generated in the cross section of the test specimen and the selectability of the control parameters : frequency, temperature, dynamic amplitude and preload. Results of a comparative study of the dynamic properties of some hidamets are pre- sented. The dependence on the influence parameters will be discussed. Finally some applications of hidamets as layered damping treatments are indicated. These applications have been designed by means of calculation methods based on bending theory of plates and for complex structures based on the modal parameters.

The loss factor ( Q ) characterizing the damping capacitd of a material is defined as (1) :

energy dissipated during one cycle rl =

maximal strain energy stored in the material duringlone cycle The loss factor can be defined for linear and non-linear materiais.

Experimental procedure.

-

The general set-up to investigate dynamic properties of hidamets is shown in Fig. 1 (9). The tubular test specimen is mounted between a dynamometer and a hydraulic exciter. The exciter is controlled by a dynamic force superponed on a static force. The temperature is controlled by a gas flow, either heated pressurized air or cooling C02, flowing inside the test specimen. Important features of the test ring are the uniform stress distribution generated in the cross section of the test specimen and the selectability of the control parameters: pre-load, dynamic amplitude, frequency and temperature.

The applied force and the longitudinal deformation of the test specimen are measured by appropriate transducers. The transfer function between applied force and resulting deformation is determined by means of a Fourier-analyser. E- lastic modulus (E') is proportional to the real part of the transfer function; loss modulus (E") is proportional to the imaginary part of the transfer function.

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The loss factor ( 1 7 ) can be calculated, referring to its definition and assuming harmonic signals :

2nw

j (c xosinot)

.

x sinot d(wt)

t=O

n =

2n1:'2.W (k.xz cos ~ t ) . sinot d(ut) where x = x cos wt

k = stiffness constant of test specimen c = damping constant of test specimen

The alloys discussed in the present paper are the martensitic Cu-Zn-A1 alloys (PROTEUS-alloys) supplied by Proteus (N.V. Bekaert S.A., Metallurgie Hoboken- Overpelt and Leuven Research and Development), Fe-12Cr-3Mo (Gentalloy) and a Mn- Cu-Al-Fe-Ni alloy (Sonoton) supplied by Sumitomo and Prof. Sugimoto, Mg-Zn-Rare earth supplied by Magnesium Elektron, Ni-Ti alloy (Nitinol) supplied by Brown-Bo- veri and pure magnesium.

The various test conditions are given in the following table, where o and

Parameters influencing the dynamic properties of hidamets. - High damping metals combine high strength properties with fairly good damping capabilities. According to the damping mechanism, one can distinguish composite materials (cast iron), ferromagnetic materials (Gentalloy), materials with dislocation damping (Mg, Ug-

Zr) and materials with movable crystal- or phase boundaries (for example Sonoston, Nitinol, Cu-Zn-A1 martensite) (2,3).

Dynamic properties, elastic modulus and loss factor, are depending on tem- perature, frequency, static and dynamic stress (4,5,9).

For Cu-Zn-A1 alloys, the loss factor exhibits a maximum at temperatures corresponding with the martensitic transformation temperature (Fig. 2). This transformation temperature can be varied by changing the composition of the alloy (6). The loss factor is almost independent of temperature for Gentalloy, Mg and Mg-Zr, in the considered temperature range. Damping phenomena or mechanisms can be either frequency independent, linearly frequency dependent or non-linearly de- pendent. The loss factor is almost independent of frequency for Cu-Zn-Al, whereas for Nitinol and Gentalloy some increases of loss factor with increasing

ud are the static and dynamic test stresses.

d ) *

are respresented in Fig. 3. Loss factors increase quasi-linearly with increasing dynamic stress; a simultaneous linear decrease of elastic moduli is observed.

Except for Proteus, all other hidamets show a decrease of loss factor with increasing static pressure (o ) , as indicated in Fig. 4. An increase of static prestress causes an increase of loss factor for Cu-Zn-A1 alloys as already pointed out earlier (7). For Cu-Zn-A1 alloys, loss factor values can be obtained either for low static stress levels combined with high dynamic amplitudes, either for high static stress levels combined with small dynamic amplitudes. This is an important feature for design applications.

Applications. - The damping capacity of hidamets has been illustrated by manufactu- ring three typical mechanical parts out of a high damping Cu-Zn-A1 alloy : a circu- lar sawblade, a tool holder and a gear transmission composed of two conical gears. The noise emitted by the Cu-Zn-A1 sawblade due to hammer impact, was redu- ced by some 12 dB, compared to the noise emission of a similar steel sawblade. This was measured in the most disturbing frequency range, between 400 and 2000 Hz. The loss factor ( n ) of the first modes of the toolholder and gears increa- sed from approximately 1 % to values between 3 % and 7 %. In the example above, almost no damping due to friction losses in interfaces occured. If friction losses in interfaces are dominant, so called "additive" layer treatments are preferable. Techniques have been developed to predict the effect of damping layers (5,9). For simple beams or plates these calculations are based on classical bending theory. For complex structures a more general method based on modal parameters has been developed (9). These techniques have been used to evaluate the effect of high dam- ping metallic strips on some consumer products. The loss factor of the first three modes increased by a factor 3. Fairly good agreement between experimental and theoretical results have been established. Cu-Zn-A1 layers have been applied to an oil-carter as well. A modal analysis on an oil pan revealed as most contribu- ting modes in the frequency range between 0 - 800 Hz an in phase first bending of the two side walls at 299 Hz and a double bending of the rear end of one side wall at 484 Hz. This latter side wall was partially covered with a high damping Cu-Zn- A1 layer. Driving point frequency responses at a characteristic point of this mo- dified side wall, for the oil pan with and without Cu-Zn-A1 layer, are represented in Fig. 5. It can be seen that there is a significant decrease of amplitude for the oil pan with a Cu-Zn-A1 layer in the considered frequency range. Loss factors of the modes at 299 and 484 Hz increased from values around 1 % to resp. 3.3 and

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Conclusions. - In thik paper the dynamic properties of the high damping metals have been shortly discussed. High values of loss factors are obtained for high dynamic

amplitudes and in a limited temperature range.

The experimental case-study confirm and illustrate the applicability of high damping materials to enhance the structural damping. A more detailed report on other properties (elastic moduli, cycling dependendy) and dealing also with other hidamets will be published elsewhere (10).

Acknowledgements.

-

The authors would like to thank Dr. J.C. Beguin and Dr. Stulemeyer (Pechiney), Dr. Bailey and Dr. Bradshaw (Magnesium Elektron), Prof. K. Sugimoto, Dr. Mercier (Brown Boveri), Dr. D. Goldstein (NSWC, USA), Dr. Tanigawa

(Sumitorno), Dr. Tuffrey (Stone Manganese Marine), Dr. Kennedy (Delta Materials), Dr. Schettky (INCRA), Prof. H. Warlimont (Vacuumschmelze), Toshiba and Proteus (N.V. Bekaert S.A., Metallurgie Hoboken-Overpelt and Leuven Research and Develop- ment, Belgium) for providing us samples of various high damping metals, some of them been discussed in the present paper and others will be discussed in a more extensive review on the hidamets.

The authors would also like

\

to thank IWONL (Instituut voor Aanmoediging van het Wetenschappelijk Onderzoek in de Nijverheid en de Landbouw of Belgium) for financial support and a research grant (U.V. and H.V.).

References

1. ACOUSTICAL SOCIETY OF AMERICA STANDARD, "Nomenclature for specific damping pro- perties of damping materials", ASA-STD-6-1976.

2. K. SUGIMOTO, Mem. Inst. Sci. Res., Osaka Univ. 35 (1978) 31

3. L. DELAEY, K. SUGIMOTO and W. DEJONGHE, Metaalbewerking

45

(1979) 303

4. D.W. JAMES, "High damping metals for engineering applications", Mater. Sci. Eng. Y (1969) 1

5. B.J. LAZAN, "Damping of materials and members in structural mechanics", Perga- mon Press, Oxford, 1968

6. L. DELAEY, W. DEJONGHE, R. DE BATIST, J. VAN HUMBEECK, "Temperature and ampli- tude dependence of internal friction in Cu-Zn-A1 alloys", Metal Science, Nov. 1977, 523-530

7. W. DEJONGHE, L. DELAEY, 0. MERCIER, Zeits. fiir Metallkunde,

70

(1969) 486

8. R. SNOEYS, D. ROESEMS, U. VANDEURZEN, P. VANHONACKER, "Survey of modal analysis applications", Annals of the CIRP, Vol 28/2, 1977, 497-510

9. U. VANDEURZEN, R. SNOEYS, J. PEETERS, "Additive damping treatments for mecha- nical structures", Proc. of the annals of the CIRP, 1981

Fig. 1 Test set-up for dynamic testing of Hidamets C

1

TEST- SPECIMEN HYDRAULIC POWER FORCE SIGNAL

,p-

;d22 d

q

'

PROTEUS

'*"*..

826

/*/

.

I

l

-7-.

t

64.-

-*,J,*c.

-

i

971 Mg \ ' 1 *<*-0-0-**--- 0 ' GENTALLOY 1 a 0 & 20

ho

TEMPELTURE

(.c)

Fig. 2 Temperature dependence of loss factor for Cu-Zn-Al, Gentalloy, Mg- and Mg-Zn-Rare earth alloy

-

LOSS FACTOR

-

-

-

4 T I I DISPLACEMENT PICK-UP "

-

FORCE ERROR CORRECTION

-

AMPLI - FlER Y F E E D BACK F-SETTING

F"

FOURIER

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PRO

I

I 1 I C

10 20 30 4;

DYNAMIC STRESS (N/im2)

Fig. 3 Dependence of loss factor on dynamic stress

694 GENTALLOY

STATIC STRESS (N/mm2)

Fig. 4 Influence of static stress on loss factor

...

WITH PROTEUS-STRIP ORIGINAL OIL-SUMP

FREQUENCY (Hz)