ISO 18437-2:2005

Mechanical vibration and shock - Characterization of the dynamic mechanical properties of visco-elastic materials - Part 2: Resonance method

ISO 18437-2:2005 defines a resonance method for determining from laboratory measurements the dynamic mechanical properties of the resilient materials used in vibration isolators. It is applicable to shock and vibration systems operating from a fraction of a hertz to about 20 kHz. ISO 18437-2:2005 is applicable to resilient materials that are used in vibration isolators in order to reduce -- transmissions of unwanted vibrations from machines, structures or vehicles that radiate sound (fluid-borne, airborne, structure-borne, or other), and -- the transmission of low-frequency vibrations that act upon humans or cause damage to structures or sensitive equipment when the vibration is too severe. The data obtained with the measurement methods that are outlined in ISO 18437-2:2005 are used for -- the design of efficient vibration isolators, -- the selection of an optimum material for a given design, -- the theoretical computation of the transfer of vibrations through isolators, -- information during product development, -- product information provided by manufacturers and suppliers, and -- quality control.

Vibrations et chocs mécaniques — Caractérisation des propriétés mécaniques dynamiques des matériaux visco-élastiques — Partie 2: Méthode de résonance

General Information

• Status: Published
• Publication Date: 17-Apr-2005
• ICS: 17.160 - Vibrations, shock and vibration measurements
• Technical Committee: ISO/TC 108 - Mechanical vibration, shock and condition monitoring
• Drafting Committee: ISO/TC 108/WG 28 - Vibration materials
• Current Stage: 9060 - Close of review
• Completion Date: 02-Sep-2029

Relations

• Consolidated By: ISO 6789-2:2017 - Assembly tools for screws and nuts - Hand torque tools - Part 2: Requirements for calibration and determination of measurement uncertainty
• Effective Date: 06-Jun-2022
• Amended By: ISO 18437-2:2005/Amd 1:2010 - Mechanical vibration and shock - Characterization of the dynamic mechanical properties of visco-elastic materials - Part 2: Resonance method - Amendment 1
• Effective Date: 18-Dec-2021

Overview

ISO 18437-2:2005 specifies a resonance method to characterize the dynamic mechanical properties of visco‑elastic (resilient) materials used in vibration isolators. The standard defines laboratory measurements to obtain complex elastic properties (e.g., Young’s modulus and loss factor) across a frequency range relevant to shock and vibration systems - from very low frequencies up to about 20 kHz - and describes procedures to extend measured data via time‑temperature superposition.

Key topics and technical requirements

• Measurement principle: Resonance testing of bar or rod specimens to determine the complex Young’s modulus and loss factor (tan δ).
• Linearity: Tests assume linear vibrational behavior at small strain magnitudes; dynamic linearity checks are required.
• Specimen preparation:
  • Mould bar specimens (mould length ≥ 150 mm); typical trimmed length 100 mm ± 10 mm with square cross‑section ~6.0 mm or circular 6–8 mm diameter.
  • Acceptable specimen lengths from half to twice the nominal length.
• Test equipment (typical specifications):
  • Electro‑dynamic vibration generator: force > 5 N, peak displacement < 0.1 mm; drive frequency practical range often 25 Hz–10 kHz.
  • Matched accelerometers (or corrected pair): charge sensitivity > 1 pC/g.
  • Charge amplifiers (≥ 1 mV/pC) or pre‑amplified sensors.
  • Dual‑channel spectrum analyser: FFT, coherence, r.m.s. averaging, random noise excitation, resolution down to 0.1 Hz and dynamic range > 42 dB.
  • Environmental chamber: allows cooling below room temperature, controlled temperature steps (increase in 5 °C increments) and stability to about 0.5 °C.
• Data analysis:
  • Extraction of modulus and loss factor from resonance peaks.
  • Application of time‑temperature superposition and shift factors to build broad‑band frequency behavior (typically many decades of frequency at a reference temperature).
  • Reporting and presentation requirements for test data.

Applications and who uses it

ISO 18437-2:2005 is used by:

• Designers and engineers creating vibration isolators, mounts and shock mounts.
• Materials scientists and R&D teams selecting or developing visco‑elastic materials.
• Test laboratories performing dynamic mechanical analysis for product data sheets and quality control.
• Acoustic and structural engineers performing theoretical computations of vibration transfer or specifying damping materials.

Practical uses include material selection, isolator design optimization, theoretical transfer‑function calculations, product development, manufacturer product information, and production quality control.

Related standards

• ISO 18437 series (Part 3: Cantilever shear beam method; Part 4: Impedance method under preparation)
• Referenced documents: ISO 4664‑1, ISO 6721‑1, ISO 10112, ISO 10846‑1, ISO 23529, ISO 472, ISO 2041.

Keywords: ISO 18437-2:2005, resonance method, visco‑elastic materials, dynamic mechanical properties, vibration isolators, Young’s modulus, loss factor, time‑temperature superposition.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 18437-2
First edition
2005-04-15
Mechanical vibration and shock —
Characterization of the dynamic
mechanical properties of visco-elastic
materials —
Part 2:
Resonance method
Vibrations et chocs mécaniques — Caractérisation des propriétés
mécaniques dynamiques des matériaux visco-élastiques —
Partie 2: Méthode de résonance

Reference number
©
ISO 2005
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ii ISO 2005 – All rights reserved

Contents Page
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Test equipment (see Figure 1) . 3
4.1 Electro-dynamic vibration generator . 3
4.2 Accelerometers . 3
4.3 Charge amplifiers . 4
4.4 Test stand . 4
4.5 Environmental chamber . 5
4.6 Dual-channel spectrum analyser . 5
4.7 Computer . 5
5 Operating procedures . 5
5.1 Sample preparation and mounting . 5
5.2 Conditioning . 6
5.3 Number of test pieces . 7
5.4 Data acquisition . 7
5.5 Temperature cycle . 8
6 Analysis of results . 8
6.1 Modulus and loss factor . 8
6.2 Time-temperature superposition . 10
6.3 Data presentation . 10
6.4 Test report . 11
Annex A (informative) Linearity of vibration resilient materials . 12
Annex B (informative) Time-temperature superposition . 13
Bibliography . 15
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ISO 2005 – All rights reserved iii

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International
Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 18437-2 was prepared by Technical Committee ISO/TC 108, Mechanical vibration and shock.
ISO18437 consists of the following parts, under the general title Mechanical vibration and shock —
Characterization of the dynamic mechanical properties of visco-elastic materials:
— Part 2: Resonance method
— Part 3: Cantilever shear beam method
Part 4 (Impedance method) is under preparation.
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iv ISO 2005 – All rights reserved

Introduction
Visco-elastic materials are used extensively to reduce vibration magnitudes in structural systems through the
dissipation of energy (damping) or isolation of components, and in acoustical applications that require a
modification of the reflection, transmission or absorption of energy. Such systems often require specific dynamic
mechanical properties in order to function in an optimum manner. Energy dissipation is due to interactions on
the molecular scale and is measured in terms of the lag between stress and strain in the material. The visco-
elastic properties (modulus and loss factor) of most materials depend on frequency, temperature, and strain
magnitude. The choice of a specific material for a given application determines the system performance. The
goal of this part of ISO 18437 is to provide details in constructing the resonance apparatus, in setting up the
measurement equipment, in performing the measurements and analysing the resultant data. A further intent is
to assist users of this method and to provide uniformity in the use of this method. This part of ISO 18437 applies
to the linear behaviour observed at small strain magnitudes.
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ISO 2005 – All rights reserved v

INTERNATIONAL STANDARD ISO 18437-2:2005(E)
Mechanical vibration and shock — Characterization of the
dynamic mechanical properties of visco-elastic materials —
Part 2:
Resonance method
1Scope
This part of ISO 18437 defines a resonance method for determining from laboratory measurements the
dynamic mechanical properties of the resilient materials used in vibration isolators. It is applicable to shock and
vibration systems operating from a fraction of a hertz to about 20 kHz.
This part of ISO 18437 is applicable to resilient materials that are used in vibration isolators in order to reduce
a) transmissions of unwanted vibrations from machines, structures or vehicles that radiate sound (fluid-borne,
airborne, structure-borne, or others), and
b) the transmission of low-frequency vibrations that act upon humans or cause damage to structures or
sensitive equipment when the vibration is too severe.
The data obtained with the measurement methods that are outlined in this part of ISO 18437 and further
detailed in ISO 18437-3 are used for
— the design of efficient vibration isolators,
— the selection of an optimum material for a given design,
— the theoretical computation of the transfer of vibrations through isolators,
— information during product development,
— product information provided by manufacturers and suppliers, and
— quality control.
The condition for the validity of the measurement method is linearity of the vibrational behaviour of the isolator.
This includes elastic elements with nonlinear static load deflection characteristics, provided that the elements
show approximate linearity in their vibrational behaviour for a given static preload.
Measurements using this method are made over one or two decades in frequency at a number of temperatures.
By applying the time-temperature superposition principle, the measured data are shifted to generate dynamic
−3 9
mechanical properties over a much wider range of frequencies (typically 10 to 10 Hz at a single reference
temperature) than initially measured at a given temperature.
NOTE For the purposes of this part of ISO 18437, the term “dynamic mechanical properties” refers to the determination of
the fundamental elastic properties, e.g. the complex Young's modulus as a function of temperature and frequency and, if
applicable, a static preload.
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ISO 2005 – All rights reserved 1

2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced document
(including any amendments) applies.
ISO 472:1999, Plastics — Vocabulary
ISO 2041:1990, Vibration and shock — Vocabulary
ISO 4664-1:2005, Rubber, vulcanized or thermoplastic — Determination of dynamic properties — Part 1:
General guidance
ISO 6721-1:2001, Plastics — Determination of dynamic mechanical properties — Part 1: General principles
ISO 10112:1991, Damping materials — Graphical presentation of the complex modulus
ISO 10846-1:1997, Acoustics and vibration — Laboratory measurement of vibro-acoustic transfer properties of
resilient elements — Part 1: Principles and guidelines
ISO 23529:2004, Rubber — General procedures for preparing and conditioning test pieces for physical test
methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions given in ISO 472, ISO 2041, ISO 4664-1,
ISO 6721-1, ISO 10112, ISO 10846-1, ISO 23259 and the following apply.
3.1
Young's modulus
∗
E
quotient of normal stress (tensile or compressive) to resulting normal strain, or fractional change in length
NOTE 1 Unit is the pascal (Pa).
� ��
NOTE 2 Young's modulus for visco-elastic materials is a complex quantity, having a real part E and an imaginary part E .
NOTE 3 Physically, the real component of Young's modulus represents elastic-stored mechanical energy. The imaginary
component is a measure of mechanical energy loss. See 3.2.
3.2
loss factor
ratio of the imaginary part of the Young's modulus of a material to the real part of the Young's modulus (the
tangent of the argument of the complex Young's modulus)
NOTE When there is energy loss in a material, the strain lags the stress by a phase angle, δ. The loss factor is equal to
tanδ.
3.3
time-temperature superposition
principle by which, for visco-elastic materials, time and temperature are equivalent to the extent that data at one
temperature are superposed upon data taken at a different temperature merely by shifting the data curves along
the frequency axis
3.4
shift factor
measure of the amount of shift along the logarithmic (base 10) axis of frequency for one set of constant-
temperature data to superimpose upon another set of data
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2 ISO 2005 – All rights reserved

3.5
glass transition temperature
T
g
temperature at which a visco-elastic material changes state from glassy to rubbery, and corresponds to a
change in slope in a plot of specific volume against temperature
NOTE 1 Unit is degrees Celsius (°C).
NOTE 2 The glass transition temperature is typically determined from the inflection point of a specific heat vs. temperature
plot and represents an intrinsic material property.
NOTE 3 T is not the peak in the dynamic mechanical loss factor. That peak occurs at a higher temperature than T and
g g
varies with the measurement frequency; hence is not an intrinsic material property.
3.6
resilient material
visco-elastic material intended to reduce the transmission of vibration, shock or noise
NOTE 1 It is sometimes referred to as an elastic support, vibration isolator, shock mounting, absorber or decoupler.
NOTE 2 The reduction may be accomplished by the material working in tension, compression, torsion, shear, or a
combination of these.
3.7
linearity
property of the dynamic behaviour of a resilient material if it satisfies the principle of superposition
NOTE 1 The principle of superposition is stated as follows: if an input x (t) produces an output y (t) and in a separate test
1 1
an input x (t) produces an output y (t), superposition holds if the input αx (t)+βx (t) produces the output
2 2 1 2
αy (t)+βy (t). This holds for all values of αβ, and x (t), x (t), where αβ and are arbitrary constants.
1 2 1 2
NOTE 2 In practice, the above test for linearity is impractical. Measuring the dynamic modulus for a range of input levels
can provide a limited check of linearity. For a specific preload, if the dynamic transfer modulus is nominally invariant, the
system measurement is considered linear. In effect this procedure checks for a proportional relationship between the
response and the excitation.
4 Test equipment (see Figure 1)
4.1 Electro-dynamic vibration generator
An electro-dynamic vibration generator is required to provide a driving force for the test specimen, producing an
oscillating displacement in the vertical direction. The dynamic strain level shall be adjusted to assure linear
behaviour (see Annex A). The following specifications are typical:
— frequency range: 25 Hz to 10 kHz;
— force rating: > 5N;
— peak displacement: < 0,1 mm.
4.2 Accelerometers
A matched pair of accelerometers is required, or a relative calibration correction shall be applied. Piezoelectric
accelerometers, with the following specifications, are typical of those required to measure the input and output
acceleration of the test sample:
— frequency range: 25 Hz to 10 kHz;
— charge sensitivity: > 1 pC/g.
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ISO 2005 – All rights reserved 3

The mass of the accelerometer plus the lower mounting block should be as small as possible (see 5.1).
NOTE It is possible to use other types of sensors, but they need to be functionally equivalent.
Key
1 electro-dynamic vibration generator
2 mounting blocks
3 accelerometers
4 test specimen
5 test stand
6 environmental chamber
7 dual-spectrum analyser
8 computer
9 charge amplifiers
10 noise source
Figure 1 — Schematic diagram of the resonance apparatus
4.3 Charge amplifiers
Charge amplifiers with a sensitivity of not less than 1 mV/pC are required to amplify the output signal from the
accelerometers. Alternatively, piezoelectric accelerometers with built-in amplifiers may be used.
4.4 Test stand
A test stand is needed to suspend the vibration generator and the test sample in a vertical position, as shown in
Figure 1. The sample and vibration generator shall be positioned so as to eliminate or minimize any horizontal
motion.
NOTE The presence of horizontal motion will appear as spurious peaks in the spectra.
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4.5 Environmental chamber
An environmental chamber is required to cool the test sample to a temperature below room temperature. This
temperature shall be maintained until the sample has reached equilibrium, then the temperature of the sample
◦
shall be increased in increments of 5 C. The chamber should be capable of operating over the temperature
◦ ◦ ◦
range from 60C7 to 0 C and should be controllable to within 0,5 C. The temperature sensor shall be
appropriately calibrated.
NOTE 1 The required temperature range is appropriate for a visco-elastic material having a glass transition temperature
◦
greater than −45 C. Materials with lower glass transition temperatures will require a lower starting temperature point.
NOTE 2 Some materials are sensitive to humidity and it may be desirable to control or at least record the relative humidity
in the chamber.
4.6 Dual-channel spectrum analyser
A dual-channel spectrum analyser with the following capabilities is typical of that required to drive the vibration
generator and analyse the accelerometer output signals:
— random noise source;
— two input channels;
— frequency response function (FFT), and coherence analysis;
— r.m.s. signal averaging;
— frequency range: 25 Hz to 10 kHz;
— dynamic range: > 42 dB;
— band selectable zoom FFT resolution: 0,1 Hz.
4.7 Computer
The use of a computer is advantageous to automate the calibration, data acquisition and processing.
5 Operating procedures
5.1 Sample preparation and mounting
Mould test specimens into the shape of a bar. The mould should be at least 150 mm long, with uniform square
� �
lateral dimensions of 6,0 mm. Trim the moulded specimen of all flash and cut to a length of
−0,1
100 mm± 10 mm, using a razor blade. Square the ends of the bar by machining if necessary. The bar shall be
able to stand upright on either end without support. Square ends are required to obtain a good bond between
the test specimen and mounting blocks.
A uniform circular cross-section of about 6mm to 8mm diameter is also acceptable instead of a square bar.
Lengths not less than one-half the 100 mm specified or not more than twice that length are also acceptable.
NOTE 1 Shorter lengths produce resonances at higher frequencies and lead to fewer peaks being observed due to higher
absorption at higher frequencies. Longer lengths produce resonances at lower frequencies and lead to problems due to
bending of the longer specimen.
Three properties of the specimen that are required in the analyses shall be measured before bonding the
specimen to the mounting blocks. In accordance with ISO 23529, determine the length, in metres, to four
significant digits. Determine, using a balance, the mass of the specimen, in kilograms, to four significant digits.
Determine the density of the specimen in kg/m by a water-displacement technique.
[1]
NOTE 2 A method such as ASTM D 792 is acceptable.
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ISO 2005 – All rights reserved 5

At the vibration generator end (Figure 1) of the specimen, bond the specimen and one accelerometer by
adhesive to the mounting block. The dimensions of the mounting steel block are typically
25 mm× 20 mm× 10 mm. Both rigid epoxy and cyanoacrylate adhesives are acceptable.
The adhesive thickness shall be less than 0,5 mm and the modulus of the adhesive shall be greater than that of
the material to be measured. Under these conditions, it has been shown that the adhesive does not affect the
[2]
measurement .
Bond the second accelerometer to the accelerometer mounting block (Figure 1), which is then bonded to the
specimen. Use the same adhesive for bonding as used previously. The accelerometer mounting block shall
have the same cross-section as the sample (steel cube, 6mm on each side, or appropriate diameter if a circular
specimen is used). Determine, using a balance, the mass of the accelerometer and mounting block, in
kilograms, to three significant digits.
NOTE 3 The purpose of the accelerometer mounting block is to avoid the wear and tear of repeatedly bonding and de-
bonding the accelerometer to the specimen. In the arrangement specified, the accelerometer is bonded to one side of the
mounting block and remains there. The other end of the block is de-bonded and re-bonded each time a new specimen is
mounted.
A small accelerometer mounting block is desirable to minimize creep in the sample. While the block should be
the same cross-sectional area as the sample, it is acceptable for the block to be shorter than the sample, but not
longer.
5.2 Conditioning
5.2.1 Storage
The time delay between moulding or vulcanization and testing and preconditioning of samples shall be in
accordance with ISO 23529.
5.2.2 Temperature
Test pieces shall be thermally conditioned before each sequence of tests. At each test temperature, it is
essential that the test piece be conditioned for sufficient time to reach equilibrium,
...