1、Designation: E 756 05Standard Test Method forMeasuring Vibration-Damping Properties of Materials1This standard is issued under the fixed designation E 756; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method measures the vibration-damping pro
3、p-erties of materials: the loss factor, h, and Youngs modulus, E,or the shear modulus, G.Accurate over a frequency range of 50to 5000 Hz and over the useful temperature range of thematerial, this method is useful in testing materials that haveapplication in structural vibration, building acoustics,
4、and thecontrol of audible noise. Such materials include metals, enam-els, ceramics, rubbers, plastics, reinforced epoxy matrices, andwoods that can be formed to cantilever beam test specimenconfigurations.1.2 This standard does not purport to address all the safetyconcerns, if any, associated with i
5、ts use. It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standard:2E 548 Guide for General Criteria Used for Evaluating Labo-ratory Competence
6、2.2 ANSI Standard:S2.9 Nomenclature for Specifying Damping Properties ofMaterials33. Terminology3.1 DefinitionsExcept for the terms listed below, ANSIS2.9 defines the terms used in this test method.3.1.1 free-layer (extensional) dampera treatment to con-trol the vibration of a structural by bonding
7、a layer of dampingmaterial to the structures surface so that energy is dissipatedthrough cyclic deformation of the damping material, primarilyin tension-compression.3.1.2 constrained-layer (shear) dampera treatment tocontrol the vibration of a structure by bonding a layer ofdamping material between
8、the structures surface and anadditional elastic layer (that is, the constraining layer), whoserelative stiffness is greater than that of the damping material, sothat energy is dissipated through cyclic deformation of thedamping material, primarily in shear.3.2 Definitions of Terms Specific to This S
9、tandard:3.2.1 glassy region of a damping materiala temperatureregion where a damping material is characterized by a rela-tively high modulus and a loss factor that increases fromextremely low to moderate as temperature increases (see Fig.1).3.2.2 rubbery region of a damping materiala temperatureregi
10、on where a damping material is characterized by a rela-tively low modulus and a loss factor that decreases frommoderate to low as temperature increases (see Fig. 1).3.2.3 transition region of a damping materiala tempera-ture region between the glassy region and the rubbery regionwhere a damping mate
11、rial is characterized by the loss factorpassing through a maximum and the modulus rapidly decreas-ing as temperature increases (see Fig. 1).3.3 SymbolsThe symbols used in the development of theequations in this method are as follows (other symbols will beintroduced and defined more conveniently in t
12、he text):E = Youngs modulus of uniform beam, Pah = loss factor of uniform beam, dimensionlessE1= Youngs modulus of damping material, Pah1= loss factor of damping material, dimensionlessG1= shear modulus of damping material, Pa4. Summary of Method4.1 The configuration of the cantilever beam test spec
13、imenis selected based on the type of damping material to be testedand the damping properties that are desired. Fig. 2 shows fourdifferent test specimens used to investigate extensional andshear damping properties of materials over a broad range ofmodulus values.1This test method is under the jurisdi
14、ction ofASTM Committee E33 on Buildingand Environmental Acoustics and is the direct responsibility of SubcommitteeE33.03 on Sound Transmission.Current edition approved Oct. 1, 2005. Published October 2005. Originallyapproved in 1980. Last previous edition approved in 2004 as E 75604e1.2For reference
15、d ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St
16、.,4th Floor, New York, NY 100361Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.1.1 Self-supporting damping materials are evaluated byforming a single, uniform test beam (Fig. 2a) from the dampingmaterial itself.4.1.2 Nonself-suppor
17、ting damping materials are evaluatedfor their extensional damping properties in a two-step process.First, a self-supporting, uniform metal beam, called the basebeam or bare beam, must be tested to determine its resonantfrequencies over the temperature range of interest. Second, thedamping material i
18、s applied to the base beam to form a dampedcomposite beam using one of two test specimen configurations(Fig. 2b or 2c). The damped composite beam is tested to obtainits resonant frequencies, and corresponding composite lossfactors over the temperature range of interest. The dampingproperties of the
19、material are calculated using the stiffness ofthe base beam, calculated from the results of the base beamtests (see Section 10.2.1), and the results of the compositebeam tests (see Sections 10.2.2 and 10.2.3).4.1.3 The process to obtain the shear damping properties ofnonself-supporting damping mater
20、ials is similar to the twostep process described above but requires two identical basebeams to be tested and the composite beam to be formed usingthe sandwich specimen configuration (Fig. 2d).4.2 Once the test beam configuration has been selected andthe test specimen has been prepared, the test spec
21、imen isclamped in a fixture and placed in an environmental chamber.Two transducers are used in the measurement, one to apply anexcitation force to cause the test beam to vibrate, and one tomeasure the response of the test beam to the applied force. Bymeasuring several resonances of the vibrating bea
22、m, the effectof frequency on the materials damping properties can beestablished. By operating the test fixture inside an environmen-tal chamber, the effects of temperature on the material proper-ties are investigated.4.3 To fully evaluate some nonself-supporting dampingmaterials from the glassy regi
23、on through the transition regionto the rubbery region may require two tests, one using one ofthe specimen configurations (Fig. 2b or 2c) and the secondusing the sandwich specimen configuration (Fig. 2d) (SeeAppendix X2.6).5. Significance and Use5.1 The material loss factor and modulus of dampingmate
24、rials are useful in designing measures to control vibrationin structures and the sound that is radiated by those structures,especially at resonance. This test method determines theproperties of a damping material by indirect measurementusing damped cantilever beam theory. By applying beamtheory, the
25、 resultant damping material properties are madeindependent of the geometry of the test specimen used toobtain them. These damping material properties can then beused with mathematical models to design damping systems andpredict their performance prior to hardware fabrication. Thesemodels include sim
26、ple beam and plate analogies as well asfinite element analysis models.5.2 This test method has been found to produce good resultswhen used for testing materials consisting of one homogeneouslayer. In some damping applications, a damping design mayconsist of two or more layers with significantly diff
27、erentcharacteristics. These complicated designs must have theirconstituent layers tested separately if the predictions of themathematical models are to have the highest possible accuracy.5.3 Assumptions:5.3.1 All damping measurements are made in the linearrange, that is, the damping materials behave
28、 in accordance withlinear viscoelastic theory. If the applied force excites the beambeyond the linear region, the data analysis will not be appli-cable. For linear beam behavior, the peak displacement fromrest for a composite beam should be less than the thickness ofthe base beam (See Appendix X2.3)
29、.5.3.2 The amplitude of the force signal applied to theexcitation transducer is maintained constant with frequency. Ifthe force amplitude cannot be kept constant, then the responseof the beam must be divided by the force amplitude. The ratioof response to force (referred to as the compliance or rece
30、p-tance) presented as a function of frequency must then be usedfor evaluating the damping.5.3.3 Data reduction for both test specimens 2b and 2c (Fig.2) uses the classical analysis for beams but does not include theFIG. 1 Variation of Modulus and Material Loss Factor withTemperature(Frequency held c
31、onstant)(Glassy, Transition, and Rubbery Regions shown)FIG. 2 Test SpecimensE756052effects of the terms involving rotary inertia or shear deforma-tion. The analysis does assume that plane sections remainplane; therefore, care must be taken not to use specimens witha damping material thickness that i
32、s much greater (about fourtimes) than that of the metal beam.5.3.4 The equations presented for computing the propertiesof damping materials in shear (sandwich specimen 2d - see Fig.2) do not include the extensional terms for the damping layer.This is an acceptable assumption when the modulus of thed
33、amping layer is considerably (about ten times) lower than thatof the metal.5.3.5 The equations for computing the damping propertiesfrom sandwich beam tests (specimen 2d - see Fig. 2) weredeveloped and solved using sinusoidal expansion for the modeshapes of vibration. For sandwich composite beams, th
34、isapproximation is acceptable only at the higher modes, and ithas been the practice to ignore the first mode results. For theother specimen configurations (specimens 2a, 2b, and 2c) thefirst mode results may be used.5.3.6 Assume the loss factor (h) of the metal beam to bezero.NOTE 1This is a well-fo
35、unded assumption since steel and aluminummaterials have loss factors of approximately 0.001 or less, which issignificantly lower than those of the composite beams.5.4 Precautions:5.4.1 With the exception of the uniform test specimen, thebeam test technique is based on the measured differencesbetween
36、 the damped (composite) and undamped (base) beams.When small differences of large numbers are involved, theequations for calculating the material properties are ill-conditioned and have a high error magnification factor, i.e.small measurement errors result in large errors in the calculatedproperties
37、. To prevent such conditions from occurring, it isrecommended that:5.4.1.1 For a specimen mounted on one side of a base beam(see Section 10.2.2 and Fig. 2b), the term (fc/fn)2(1 + DT)should be equal to or greater than 1.01.5.4.1.2 For a specimen mounted on two sides of a basebeam (see Section 10.2.3
38、 and Fig. 2c), the term (fm/fn)2(1 +2DT) should be equal to or greater than 1.01.5.4.1.3 For a sandwich specimen (see Section 10.2.4 andFig. 2d), the term (fs/fn)2(2 + DT) should be equal to or greaterthan 2.01.5.4.1.4 The above limits are approximate. They depend onthe thickness of the damping mate
39、rial relative to the base beamand on the modulus of the base beam. However, when thevalue of the terms in Sections 5.4.1.1, 5.4.1.2,or5.4.1.3 arenear these limits the results should be evaluated carefully. Theratios in Sections 5.4.1.1, 5.4.1.2, and 5.4.1.3 should be used tojudge the likelihood of e
40、rror.5.4.2 Test specimens 2b and 2c (Fig. 2), are usually used forstiff materials with Youngs modulus greater than 100 MPa,where the properties are measured in the glassy and transitionregions of such materials. These materials usually are of thefree-layer type of treatment, such as enamels and load
41、ed vinyls.The sandwich beam technique usually is used for soft vis-coelastic materials with shear moduli less than 100 MPa. Thevalue of 100 MPa is given as a guide for base beam thicknesseswithin the range listed in 8.4. The value will be higher forthicker beams and lower for thinner beams. When the
42、 100 MPaguideline has been exceeded for a specific test specimen, thetest data may appear to be good, the reduced data may havelittle scatter and may appear to be self-consistent. Although thecomposite beam test data are accurate in this modulus range,the calculated material properties are generally
43、 wrong. Accu-rate material property results can only be obtained by using thetest specimen configuration that is appropriate for the range ofthe modulus results.5.4.3 Applying an effective damping material on a metalbeam usually results in a well-damped response and a signal-to-noise ratio that is n
44、ot very high. Therefore, it is important toselect an appropriate thickness of damping material to obtainmeasurable amounts of damping. Start with a 1:1 thicknessratio of the damping material to the metal beam for testspecimens 2b and 2c (Fig. 2) and a 1:10 thickness ratio of thedamping material to o
45、ne of the sandwich beams (2d). Con-versely, extremely low damping in the system should beavoided because the differences between the damped andundamped system will be small. If the thickness of thedamping material cannot easily be changed to obtain thethickness ratios mentioned above, consider chang
46、ing the thick-ness of the base beam (see Section 8.4).5.4.4 Read and follow all material application directions.When applicable, allow sufficient time for curing of both thedamping material and any adhesive used to bond the materialto the base beam.5.4.5 Learn about the characteristics of any adhesi
47、ve used tobond the damping material to the base beam. The adhesivesstiffness and its application thickness can affect the damping ofthe composite beam and be a source of error (see Section 8.3).5.4.6 Consider known aging limits on both the damping andadhesive materials before preserving samples for
48、aging tests.6. Apparatus6.1 The apparatus consists of a rigid test fixture to hold thetest specimen, an environmental chamber to control tempera-ture, two vibration transducers, and appropriate instrumenta-tion for generating the excitation signal and measuring theresponse signal. Typical setups are
49、 shown in Figs. 3 and 4.6.2 Test FixtureThe test fixture consists of a massive,rigid structure which provides a clamp for the root end of thebeam and mounting support for the transducers.6.2.1 To check the rigidity and clamping action of thefixture, test a bare steel beam as a uniform specimen (seeSection 8.1.1) using the procedure in section 9 and calculatethe material properties using the equations in Section 10.2.1.IfYoungs modulus is not 2.07 E+11 Pa (30 E+6 psi) and the lossfactor is not approximately 0.002 to 0.001 for modes 1 and 2and 0.001 or less for the h
