ISO 8568:2007

INTERNATIONAL ISO
STANDARD 8568
Second edition
2007-07-01
Mechanical shock — Testing machines —
Characteristics and performance
Chocs mécaniques — Machines d'essai — Caractéristiques et
performance
Reference number
©
ISO 2007
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ii © ISO 2007 – All rights reserved

Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 Performance . 2
4.1 General. 2
4.2 Operation principles. 2
4.3 Test types . 3
4.4 Shock-testing machine components. 3
5 Shock-testing machine specification . 4
6 Requirements for shock-testing machines. 5
6.1 General. 5
6.2 Safety requirements . 5
6.3 Table or carriage. 5
6.4 Hoisting or pre-loading . 6
6.5 Braking systems . 6
6.6 Reaction mass. 6
6.7 Shock pulse-shaping devices and methods. 7
7 Inspection of a shock-testing machine . 7
7.1 General. 7
7.2 Preparation procedure . 7
7.3 Example of an inspection procedure for a shock-testing machine operation . 8
Annex A (informative) Devices for shaping various pulse shapes . 10
Annex B (informative) Shock-response spectra, shock synthesis and analysis . 12
Annex C (informative) Use of a vibration generator for producing a shock pulse. 15
Annex D (normative) Determination of uniformity of acceleration and relative transverse motion
on the table of a shock-testing machine . 20
Annex E (normative) Stray magnetic field. 22
Bibliography . 23

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 8568 was prepared by Technical Committee ISO/TC 108, Mechanical vibration, shock and condition
monitoring, Subcommittee SC 6, Vibration and shock generating systems.
This second edition cancels and replaces the first edition (ISO 8568:1989), which has been technically revised.

iv © ISO 2007 – All rights reserved

INTERNATIONAL STANDARD ISO 8568:2007(E)

Mechanical shock — Testing machines — Characteristics and
performance
1 Scope
This International Standard specifies performance parameters and methods of inspection of mechanical
shock-testing machines and gives guidelines for describing their characteristics. It is intended to ensure that
the potential user of a particular shock-testing machine is provided with an adequate description of the
characteristics of the machine, and also to give guidance on the selection of such machines.
This International Standard is applicable to the shock-testing machines that are used for demonstrating or
evaluating the effect of shock conditions representative of the service environment in accordance with the
relevant part of IEC 60068 and also for diagnostic testing. The purpose of the shock test is to reveal
mechanical weakness and/or degradation in specified performance. It can also be used to determine the
structural integrity of a test specimen or as a means of quality control.
Machines used for simulation of earthquakes, sonic booms, explosions and implosions, bursting tests,
metalworking, forming, etc. are not covered in this International Standard.
Several techniques for generating the desired shock motion are discussed. Both simple-pulse and complex
transients can be produced. The simulation of transients can be achieved by control of the test with a
specified shock-response spectrum.
NOTE 1 Annex A gives a description of pulse-shaping devices. Annex B defines methods of application of the shock
response spectra. Annex C considers a method of evaluating the possibility of using a vibration generator for producing a
shock pulse. Annexes D and E deal with the methods of measurement of some characteristics in inspection methods (or
procedures) of shock-testing machines.
NOTE 2 Characteristics of vibration-generating equipment are covered in ISO 5344, ISO 6070 and ISO 8626.
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 2041:1990, Vibration and shock — Vocabulary
ISO 5347 (all parts), Methods for the calibration of vibration and shock pick-ups
ISO 5348, Mechanical vibration and shock — Mechanical mounting of accelerometers
ISO 15261, Vibration and shock generating systems — Vocabulary
ISO 16063 (all parts), Methods for the calibration of vibration and shock transducers
IEC 60068-1:1988, Environmental testing — Part 1: General and guidance
IEC 60068-2-27:1987, Environmental testing — Part 2: Tests — Test Ea and guidance: Shock
IEC 60068-2-81, Environmental testing — Part 2-81: Tests — Test Ei: Shock — Shock response spectrum
synthesis
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 2041, ISO 15261 and the following
apply.
3.1
check point
fixing point nearest to the centre of the table surface of the shock-testing machine, unless there is a fixing
point having a more rigid connection to the table, in which case the latter point is used
3.2
nominal load
maximum load used for the testing of a shock-testing machine as specified by the manufacturer
3.3
shock-testing machine
device for subjecting a system to controlled and reproducible mechanical shock
[ISO 2041:1990, 3.23]
NOTE Shock-testing machines can be classified as specially designed shock generators, gravity and powered, and
vibration generators of electrodynamic and servo-hydraulic types used in a shock mode.
4 Performance
4.1 General
The performance of a shock-testing machine is based on a relatively slow accumulation of energy used to
reproduce a shock, and its consequent discharge in an energy-transducing device for a short period of time.
The energy needed to create a shock may be achieved by the work against gravity (in free-fall machines) or, if
the shock is in a direction other than upwards or if the free-fall machine does not provide enough velocity
change, the necessary potential energy may be supplied by elastic cords, springs or hydraulic and pneumatic
means.
The shock can also be achieved by releasing compressed gas, by explosives or by transfer of momentum
from one moving mass to another.
4.2 Operation principles
According to the principle used, shock-testing machines are classified as free-fall or accelerated shock-testing
machines, or as gas guns or explosive guns, hydraulic and pneumatic, as well as servo-hydraulic and
electrodynamic.
The shock pulse (either a single-pulse or a transient vibration) is produced by a shock pulse-shaping device
mounted on the table or carriage, on the reaction mass, or on both. A wide selection of pulse shapes can be
produced depending on how the kinetic energy is transferred by pulse-shaping devices. Annex A gives some
guidelines on the selection of pulse-shaping devices.
Pulse-shaping devices can be used in a rebounding or non-rebounding mode. Usually the device that
attaches the test specimen is initially accelerated and a shock is produced during the rebound of the test
specimen. Sometimes (for large masses or when the acceleration of the test specimen during shock
pre-history is undesirable) a reaction mass or a hammer can be initially accelerated and the shock is produced
as a result of the impact between the reaction mass and the device that attaches the test specimen. This
mode is classified as non-rebounding.
2 © ISO 2007 – All rights reserved

As an alternative to the shaping of the shock pulse, for electrodynamic or servo-hydraulic vibration generators,
a shock-response spectrum of the impulse to be applied to the specimen may be shaped to be similar to the
required shock-response spectrum.
When the test specification requires some tolerance for a test shock-response spectrum (e.g. +3 dB, −1,5 dB),
electrodynamic and servo-hydraulic test equipment for generating vibration may also be used for shock testing.
These machines can generate classical shock waveforms (half-sine, trapezoidal, saw-tooth, etc.) as well as
arbitrary waveforms which have the required shock-response spectra, and are usually produced by means of
digital control, but generally have limited velocity and displacement capability. A method for maintaining the
above limitations is briefly treated in Annex C. Characteristics of vibration-generating equipment are covered
in ISO 5344, ISO 6070 and ISO 8626.
4.3 Test types
4.3.1 Shock pulse generation
Classical shock pulse shapes in accordance with IEC 60068-2-27 are generated with additional pre-pulse and
post-pulse shaping to limit velocity and displacement. The amplitude of the pre-pulse and post-pulse shapes is
limited to a small fraction of the primary pulse amplitude.
...