NL8201985A - METHOD FOR DAMPING VIBRATIONS USING FORM MEMORY ARTICLES. - Google Patents

Description

82.5085 / Ti / jz

Short designation: Method for damping vibrations using shape memory alloy objects.

The application relates to a method of damping mechanical vibrations in a solid material construction using one or more metal alloy objects having shape memory properties which are in the martensite phase at ambient temperature.

Shape memory metal alloys, with varying degrees of success, can absorb the energy of distortion vibrations and convert them to heat, through their internal friction in the martensite phase. The ability to do this exists mainly in the martensite phase, so these metals belong to the group of hidamets. However, the damping capacity of all memory alloys is not sufficiently high or not stable enough over time or after a certain number of vibrations in all circumstances; for example, they can lose their damping power relatively quickly.

The memory alloys are characterized by a transformation from a lower temperature martensitic phase to a β-phase intermetallic compound, which may be accompanied by a macroscopic shape change of the object which occurs in reverse upon re-cooling to the martensite phase. The limit temperatures on heating are Ag and and on cooling M and M ^. Mechanical stress affects these temperatures.

The object of the invention is to convert a larger share of the vibrational energy absorbed by an object with shape memory into a different energy form and to optimize the degree of this damping after repeated vibration load. Repeated vibration load is understood to mean those circumstances in which the object 8201985 - 2 goes through an indefinite number of vibration cycles in the form of, for example, a standing vibration or a repeated shock load in one. determined course of time, for example a number of shocks per minute or per hour, so that the term "tool life" is attached to the object.

The invention provides a method in which one or more shape memory alloy objects, which are completely martensite phase at ambient temperature, are fixedly attached to a vibration-prone mechanical construction such that they undergo a vibration amplitude of -5 greater than 10 and which is preferably below the limit of microplastic deformation. This limit is usually considered to be -3 to 10. Preferably, the range is used between 4, 3, 10 "and 10". The vibration amplitude is here determined as the dimensionless -3 magnitude of distortion, 10 is 0.1 $ distortion, measured between the neutral position and the maximum deflection.

In order to make a shape memory alloy object completely martensite, it must be cooled above M after satisation of the structure, and cooled to below M after certain waiting time at that temperature within certain limits of cooling rate. ^ temperature.

In order to obtain improved damping, the martensitic article must not have deformed and must remain fully in this state during its function, which means that it must not contain any precipitate from any other phase and after cooling it may not fall below M 2. at no time are formation of another phase, nor by heating above A, s

nor by deformation or stresses. This A

s temperature must therefore be higher than the ambient and operating temperature of the vibration damping, however the difference may vary between 1 ° C to 100 ° C or more. The damping level 8201985 - 3 - φ * * may decrease as the difference becomes more important.

The cooling procedure is also important to obtain better vibration damping, especially to maintain a certain damping level for an extended period of time. This depends on the composition of the alloy. Preferably, a shape memory alloy workpiece is brought to the equilibrium temperature of the β phase and cooled in a quenching medium to a temperature above Mg, for example 70 ° C to 200 ° C and kept at that temperature (aged) for a time. it can vary from one minute to several hours, for example three hours. The chosen time will be longer if the treatment is done close to M or if the quenching speed was faster.

5 '

The time is shorter if the treatment is done at a temperature significantly higher than M or if the cooling rate is slower 3

15. This treatment can, for example, be carried out in oil between 70 ° C and 100 ° C or 200 ° C. The aging time is not arbitrarily long because the precipitation of some elements in, for example, bainite or CC phase (a metallic solution) adversely affects the damping property. The alloy must consist of a metastable β-compound with mainly substituently dissolved side elements and must cool further below M

3 and M ^. completely converted to martensite and preferably at a cooling rate of between 0.5 ° C and 10 ° C per minute. The aging time depends on the absolute temperature and the composition and is optimized for each individual case.

Additionally or alternatively, improved damping properties are obtained through the judicious selection of the alloy properties. The treatment can then be adapted to the thermo-mechanical history.

30 A deformation of the martensite phase, for example, will cause the A temperature to be higher, even at 3 8201985 - 4 -

, J

•> usual heating rates. This effect disappears after one or more transformation cycles. The damping capacity of deformed martensite quickly decreases after a limited number of vibrations. A possible deformation in martensite is preferably such that after removal of the deformation force a plastic fumigation remains which is, for example, less than Λ%.

The ambient temperature at which the method according to the invention is applied is in most cases at room temperature between 0 ° C and 40 ° C. The Ash temperature of undistorted martensite must then be higher than 40 ° C. If for some reason a partial transformation has occurred, this must be neutralized by cooling below M ^.

A construction of solid material is considered to be any mechanical structure where, during use, a mechanical vibration occurs in one or more parts, either continuously or intermittently. This is, for example, the stop or die of a molding press machine, a part of a machine tool, the protection plate of a cable machine or an engine, parts of a vehicle, vessel or aircraft in metal, plastic or composite. However, the damping that occurs naturally in plastic or composites is usually greater than that of hidamets. The shape memory alloy articles can be attached to the solid material construction as a functional part or as a non-functional part, for example, as a glued-on plate, as a profile, rod, connecting element, pad, ballast weight, etc. or in any way vibrating mass confirmed. The design and the placement are preferably carried out according to known technology in such a way that especially the low-frequency vibrations are damped, for instance below 100 Hz; after all, these vibrations are the most pervasive. The occurring vibration frequency per se is partly determined by the 8201985 - 5 - ♦ source and the inherent frequency of the system · However, the frequency that occurs is secondary for the damping. It is also possible to design the damping parts as a mixture of shape memory alloy articles in combination with a thermosetting or thermoplastic material, an elastomer or a combination of these materials.

The damping is expressed as a quantity as the loss factor Q * "^. This loss factor is the ratio of the energy fraction Δ W per unit volume of the object which is lost by internal friction during vibration to the total energy factor. content W in the form of vibration present per unit volume multiplied by 2 TT.

You 2ΤΓ W

The loss factor can be determined at different temperatures. 15 with a device of the types DMA 980 and 981, "Dynamic

Mechanical Analyzer "mentioned and proposed by Du Font Instruments, Wilmington DE 19898 - USA with the corresponding description E 16368. The samples tested at their own frequency are usually shape memory-20 metal plates of 30.5 mm length, a width of 5 to 10 mm and a thickness of 0.3 to 1.5 mm The frequency that is possible in this arrangement is between 3 Hz and 100 Hz, but is usually understood between 20 and 50 Hz. of a deformed state, the shape memory of the alloy is not used directly.

Most shape memory alloys are suitable for vibration damping, but preference is given to more readily available materials such as copper alloys and more particularly Cu Zn Al. In some cases Cu is to a limited extent substituted by 6 or more elements such as, for example, Ni. Cu Al Ni, 8201985 • »- 6 -

Cu Sn, Ni Ti and other formulations are eligible for the same application without limiting this list.

The composition changes the A transition temperature so that s 5 can be selected according to the prevailing working conditions. Due to the combination of thermo-mechanical pretreatment and the chosen composition, the working area and the stability of the vibration damping over time can be determined on the basis of an experiment with vibration analysis. It is assumed that the loss factor Q ^ after 100,000 vibration cycles must be even higher than 2%. This limit is in some cases brought to $ 4 even after 1,000,000 cycles. In other circumstances, the limit is at 10,000 cycles, for example. This damping stability can be improved by adjusting the in-phase aging time or by taking a different alloy composition or by combining both.

The invention will be elucidated with reference to the figures, in which the vibration behavior is shown. The alloy composition is given by weight in each case.

Fig. 1 shows the change of the loss factor at falling temperature;

Fig. 2 shows the variation of the loss factor with the number of cycles.

FIG. 3 shows an example of heat treatment.

Fig. 4 shows a detail of the ternary diagram Cu Zn Al.

Fig. 5 shows the influence of Ni substitution in Cu Zn Al on the stability of the loss factor.

Fig. 1 was determined by the damping analyzer.

A shape memory alloy metal plate was vibrated with its own frequency. From a temperature in the 8201985 'Λ • * -7 - metastable β phase, it was gradually cooled, determining the loss factor Q "^, its course giving the curve 1. When M exceeds M in 2, Q ^ rises very quickly. up to a maximum 3 to descend so that the curve 1 has a 5 inflection point 4 when it is reached * Then the curve shows a minimum 5 to reach again, after the increase in point 6, a second maximum 7 and then gradually decrease in the part 8 * At room temperature K there is stable damping and this corresponds to the zone 6, With reheating a 10 analog 1 * is registered where the point A can be around M $ s without a direct relationship. of the loss factor then occurs between A and Ar.

—1 s t

However, the loss factor CT determined in this way is only a snapshot at variable temperature. If the temperature is kept constant in the transition region between Mg and, for example, the loss factor drops after a few vibration cycles to a small residual value that has little meaning (see curve 15 in Fig. 2). The behavior presented in Figure 1 is a typical example. However, there are a number of variants in which, for example, the damping remains at the maximum level with decreasing temperature.

Fig. 2 gives results of the damping measurement with said device on an alloy (curve 10) at a peak amplitude of 0.2 mm. The sample consisted of 73.7% Cu, 20.3 $ Zn 25 6.0 $ Al wt. and after plating at 750 ° C and 15 min, was aged for 30 min at 95 ° C, air cooled and tested at 22 ° C. The M temperature is + 80 ° C and the A temperature + 75 ° C.

s. . -1 S.

The initial value of the measurement is Qq. After an initial maximum Cf ^, after 3.6 kS (kilo-seconds) in 11, the loss factor decreases gradually to 0.9 Cf7 at 11 kS. At that time, the amplitude is brought to 0.8 mm for 2 seconds, generating a new damping characteristic 12 analogous to the 8201985-8 first 10. This regeneration of the damping is also possible by mechanically relaxing (loosening) the sample or by repeating a thermal cycle above A ^ and below M ^. 5 Line 13 is the simultaneous recording of the frequency which is between 25 and 30 Hz expires. Curve 14 gives the attenuation course of an identical sample, which was, however, directly scraped to 20 ° C martensite in water.

If the martensitic transformation did not complete passage 10, the attenuation will become almost negligible as shown in the curve 15. Other attenuating compositions are given in Table II.

Fig. 3 is the schematic of the thermal treatment as a function of time and with respect to the conversion temperatures of 15 Ms, Mj. on cooling and A ^ on heating to achieve an improved damping, whereby the loss factor remains longer above a limit value over time. Line 16 indicates the temperature trend over time S. The shaded zone indicates when insufficient attenuation is found. For example, the alloy consists of $ 65.6 Cu, $ 14.1 Zn, $ 8.3 Al, $ 2 Ni, $ weight.

The aging takes place at 70 ° C (Τβ) for a period a of 120 min. The temperature of 45 ° C and 15 ° C is exceeded by cooling in a water ice mixture. The sample is then allowed to reheat to 20 ° C, the test temperature, as much as 25 A (45 ° C). The cycle must be completed for regeneration s

above A.

Fig. 4 shows in a ternary diagram a number of compositions of alloys Cu Zn Al, in which the invention can be applied. The region of interest is 30 between points 17, 18, 19 and 20. The following points 17: 1 $ Al and 35 $ Zn; 18: 5 $ Al and 21 $ Zn; 19: 12.5 $ Al and 0 $ Zn; 20: 14 $ Al and 0 $ Zn, all in percent by weight, the remainder in 8201985 - 9 - mainly Cu, possibly replaced by a few percent of another metal, for example Ni to 2.3 $. The conversion temperature varies between about 0 ° C and 200 ° C. The difference between Ag and M is a few ° C. The actually measured conversion temperature 5 is a more efficient criterion than the composition, which is only a visual parameter due to accuracy limits of the analysis.

Fig. 5 shows the influence on the damping factor of such alloys. Ni is added as a substitute for Cu by weight, because at the same ratio Al - Zn a small deviation from M.

S 'is expected. Compositions A and M temperatures are shown in Table I s s. Line 21 is the damping factor after 100,000 cycle cycles, line 22 after 200,000 cycles, and line 23 after 300,000 cycles. Replacement of 2 $ Cu by 2 $ Ni has a stabilizing effect on the value of the damping factor. The aging time was 2 hours at 220 ° C.

It goes without saying that a similar behavior can be found, especially with copper alloys where a transition from a β Hume - Rothery metallic compound to a martensitic phase at suitable temperature is possible.

However, the aging time can be decisive for a positive or negative result. For example, the damping factor in the example of Fig. 5 was significantly smaller when the quench time was reduced from 2 hours to 1 hour or 30 minutes.

FIG. 6 refers to an alloy 73.44 $ Cu, 20.24 $ Zn and 6.06 $ Al and shows the influence of the amplitude on the damping factor when vibrating for a long time kS (kiloseconds). The figures for the different curves are the imposed amplitudes.

At lower amplitudes, the damping factor is variable over time, while at higher amplitudes around 10, the damping factor remains practically the same or even increased for a very long time.

The sample's natural frequency is usually between 25 and 8201985. 10 - 3 Hz.

TABLE I

Cu Zn Al Ni Μ A

-ίίϊ_ίίΐ _ {$} _ (- $) _- (° C) (° C) a 73.44 20.24 6.06 - 70 65 76.83 14.44 8.22 0.51 100 85 c 72, 6 20.7 6.2 0.5 87 80 d 74.96 17.30 6.97 0.56 74 56 e 76.18 14.79 7.92 0.96 35.5 22 f 76.79 12. 68 8.6 1.94 62 41 s 75.57 14.06 8.17 2.03 37.5 26

TABLE II

Cu Zn Al M A

^) - (#) .- (#) (° c) (° C) h 73.7 20.3 6.0 60 55 i 73.94 20.24 6.06 80 75 y 70.0 26, 0 4.0 53 48 k 78 14 8 72 60 8201 985

Claims (10)

1. A method for damping mechanical vibrations in a solid material construction by means of one or more metal alloy objects with shape memory which have a conversion temperature A higher than the ambient temperature, so that at this A temperature the torture phase at s reproducibly transitions to the / * phase of a metallic compound, characterized in that one or more shape memory metal alloy objects are mounted on a solid material construction, that these objects are completely martensitic and that they absorb vibration energy with a -5 deformation amplitude greater than 10 and less than the limit of microplastic deformation through repeated vibration loading. 2. A method according to claim 1, characterized in that the objects are aged above the Mg temperature during quenching from the / 3 phase and then cooled below the temperature. 3. Method according to claim 1 or 2, characterized in that the objects consist of martensite with a permanent plastic deformation of less than 1%. 4. Method as claimed in claims 1 to 3, characterized in that the deformation amplitude is less than 10 Method according to any one of claims 1 to 4, characterized in that the deformation amplitude -4 is greater than 10. 8201985 - 12 - Method according to any one of claims 1 to 5, characterized in that after repeated vibration loading the amplitude is changed briefly and drastically to increase the output damping again. A method according to any one of claims T to 5, with. It is noted that the metal alloy is a copper alloy with more than 50 $ Cu, Process according to claim 7, characterized in that the copper alloy contains Zn and Al between the 10 compositions (17) Cu 62.5 $, Al 1 $, Zn 35 $ - (18) Cu 74 $, Zn 21 $, Al 5 $ - (19) Cu 87.5 $, Al 12.5 $, Zn Q $ and (20) Cu 86 $, Al 14 $, Zn 0 $. 9. Process according to claim 8, characterized in that 1 to 2.3 Cu is substituted by Ni. 10. Construction of solid material comprising one or more shape memory metal alloy articles having a conversion temperature A higher than the ambient temperature so that at this A temperature the martensite phase transitions to the phase of S in a reproducible manner. a metallic compound, characterized in that these objects are completely in a martensitic state such that they absorb vibrational energy with a deformation amplitude greater than 10 and less than the limit of microplastic deformation by repeated vibration loading. 8201985