ISO 8568:2007

Mechanical shock — Testing machines — Characteristics and performance

ISO 8568:2007 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. ISO 8568:2007 is applicable to the shock-testing machines that are used for demonstrating or evaluating the effect of shock conditions representative of the service environment 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 ISO 8568:2007.

Chocs mécaniques — Machines d'essai — Caractéristiques et performance

General Information

• Status: Published
• Publication Date: 24-Jun-2007
• ICS: 17.160 - Vibrations, shock and vibration measurements
• Technical Committee: ISO/TC 108/SC 6 - Vibration and shock generating systems
• Drafting Committee: ISO/TC 108/SC 6 - Vibration and shock generating systems
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 15-Apr-2021

Relations

• Revises: ISO 8568:1989 - Mechanical shock — Testing machines — Characteristics and performance
• Effective Date: 15-Apr-2008

Standards Content (Sample)

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 8568:2007(E)
ISO 2007
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ISO 8568:2007(E)
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ISO 8568:2007(E)
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

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ISO 8568:2007(E)
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.

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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
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ISO 8568:2007(E)
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.
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ISO 8568:2007(E)

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.
4.3.2 Shock-response spectrum generation

A brief, low-level oscillatory transient impulse is typically applied to the specimen. The shock-response

spectrum is measured, compared with the desired shock-response spectrum, and the difference used to

modify the shape of the next impulse. Typically, this process is repeated several times until the desired shock

spectrum is achieved, and then an input transient impulse of the desired level is applied to the specimen. The

desired shock spectrum may be either standardized (i.e. one of the shock spectra of Annex B) or the shock

spectrum of a field environment.
4.4 Shock-testing machine components
A shock-testing machine consists of the following:

a) a rigid table or carriage with means of attaching test specimens and shock pulse-shaping devices;

b) a set of guides that controls the movement of the carriage;

c) a means for storing the potential energy necessary for imparting the shock, such as provisions for

hoisting or preloading springs and cords attached to the carriage;

d) a means for securing the carriage at a selected drop height or position, prior to initiation of the shock

pulse;
e) a release mechanism;
f) a reaction mass or base upon which the carriage impacts;

g) a pulse-shaping and rebound braking system, or means to generate and control the shock spectra;

h) control equipment;
i) shock-measuring system;
j) auxiliary power, cooling and other equipment, as required.
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ISO 8568:2007(E)
5 Shock-testing machine specification

The motion of the table or carriage may be specified by shock-response spectra and/or time-history

parameters. Depending on the type of shock-testing machine (specially designed shock generators or

vibration generators used in a shock mode), where applicable, data together with tolerances, shall be given for

the following items:
a) available pulse shapes for free fall and accelerated tables;
b) maximum velocity change;
c) maximum displacement;
d) range of reproducible shock-pulse peak accelerations versus pulse durations;
e) initial or pre-pulse acceleration and final or post-pulse acceleration;
f) minimum shock-pulse duration;
g) frequency range of wavelets to reproduce a shock-response spectrum;
h) shock-response spectrum flatness with resolution in 1/3, 1/6 or 1/12 octave;
i) maximum drop height, preload pressure or charge;
j) tare mass of table or carriage and total moving mass;
k) maximum allowable axial force of specimen-mounting screw;
l) natural frequencies of the table or carriage;
m) natural frequencies of the machine on its foundation;
n) required pressure and volume of gas and liquids;
o) quantities and flow rates of fluid or gas for the operation of the machine;
p) type of rebound braking system and braking force;

q) size and overall dimensions of the machine and its parts, especially the table or carriage and its

accessories;

r) dimensions, mass and mounting method of reaction masses and floor-loading requirements;

s) maximum size and mass of test specimen;
t) mounting facilities for test specimen and transducers;

u) number of shocks (shock pulses) possible per unit time, or, alternatively, minimum period between two

shocks;
v) specification of the shock-measuring system employed;
w) centre of gravity of the table, plus the effect of any off-centre load;

x) acceptable range of environmental conditions, i.e. temperature, humidity, etc.

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ISO 8568:2007(E)
6 Requirements for shock-testing machines
6.1 General

The performance of shock-testing machines shall be defined and specified by the manufacturer.

Detailed installation, operation and maintenance instruction manuals shall be provided by the manufacturer.

Instructions shall include requirements for periodic inspection, maintenance and lubrication of the equipment.

Signs of wear of replaceable components and possible structural failure shall be described by the

manufacturer. Appropriate steps shall be proposed for replacing deteriorating pulse-shaping devices and for

repairing leaks in the pneumatic and hydraulic systems.

Application and mounting of test specimens, adapter plates and fixtures to the table or carriage shall be

thoroughly described. The effects on the test of eccentric or faulty loading of the carriage shall be explained.

Installation dimensions shall include adequate working room, overhead clearances and walk-ways around the

equipment.

Electrical power requirements shall be stated and the normal operation of the machine shall not cause any

interference in the power network that might affect the test monitoring instrumentation.

If a shock-testing machine operates by means of compressed gases or fluids, then adequate seals shall be

used to prevent blow-out of gases or fluids during the test. All sections of barrels, cylinders and piping shall be

designed with an adequate safety factor. The maximum expected pressures produced throughout the worst-

case test should be considered.
6.2 Safety requirements

The overall machine design and installation shall provide sufficient safety and shall protect personnel from

flying objects if the equipment or test specimen fails structurally.

Guns shall be located in restricted remote areas, with adequate blast-proof enclosures for the protection of

personnel. Maximum gas pressures external to the gun and sound pressure levels shall be specified.

The table or carriage, piston or sabot shall be securely retained and fixed when being made ready for testing.

The table or carriage shall be prevented from striking the reaction mass while personnel are assembling

pulse-shaping devices.

Release or firing shall be possible only on command. The release mechanism shall be fail-safe and

impossible to activate accidentally, for example by providing two simultaneously activated switches, one of

which is lockable.

Gases that are likely to be compressed during testing shall not present any risk of spontaneous combustion by

self-ignition.

It should be remembered that shock-testing machines can be used for human exposure testing and should

therefore have proven reliability and safety. For such machines, the table or carriage shall be accessible

immediately after the impact so that the human subject can be released quickly.

Protection shall be provided to protect human subjects from electrical terminals. The complete system shall

meet appropriate safety requirements.
6.3 Table or carriage

The table of a vibration generator or the carriage of a shock generator (piston, sabot, spigot or tubes) and all

accessories used for movement of the test specimen during the shock test shall be designed for maximum

stiffness, strength and damping.
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ISO 8568:2007(E)

The means of attaching a test specimen and the limits of torque to be applied to the fixing screws shall be

indicated.

In the case of test tables, it shall be stated whether or not they are fitted with replaceable threaded inserts,

and whether they are recessed or raised. All test specimen mounting surfaces shall be geometrically flat and

of minimum roughness and the applicable tolerances shall be stated. If the surface is fitted with recessed

inserts, the flatness of the whole surface shall be indicated for normal reference atmospheric conditions (see

IEC 60068-1:1988, Clause 5). If replaceable raised inserts are provided, the resulting co-planarity of the insert

surfaces shall be given, based on the thickness tolerance of the insert flanges and the flatness of the insert-

mounting surface.

The maximum torque to be applied to replaceable inserts during installation shall be stated, together with the

types of materials being mated.

A drawing or diagram shall be provided giving all dimensions of the table or carriage, the dimensions and

positional tolerances of the inserts, and the material from which they are made.

The maximum permissible torque and axial force that may be applied to the inserts shall be stated, together

with the required perpendicularity of the test specimen fixing screws with respect to the mounting surface.

6.4 Hoisting or pre-loading

The free-fall and the accelerated shock-testing machines, and machines that use a hammer or a pendulum,

shall be supplied with mechanisms for hoisting and pre-loading the carriage to a predetermined drop height or

tension, for example by means of a built-in height- or angle-measuring scale with a residual indicator. The

precision of the drop height or pre-load setting shall be specified, together with tolerances. The machine shall

be fitted with devices to stop the carriage automatically or to indicate to the operator when the carriage has

reached a predetermined drop height or pre-load. The manufacturer shall specify the maximum drop height or

pre-load.

If the test has to be aborted, it shall be possible to disarm the machine and safely lower the table or carriage.

6.5 Braking systems

Shock-testing machines should be equipped with adequate braking systems. Braking may be achieved by

mechanical, electrical, pneumatic or hydraulic devices. Shock-absorbing materials or parachutes may be

employed on devices that are in free trajectory and these shall be recovered with minimum damage.

The design of the braking system shall ensure that minimum vibration is superimposed on the pulse trace and

that shock tests can be limited to a single pulse.

Acceleration limits for braking shall be given by the manufacturer, together with information on the braking

force required for controlled braking. The magnitude of acceleration applied during braking shall not exceed

25 % of that applied during the test pulse.

A shock-testing machine not equipped with a braking system should be adequately marked and shall be

prevented by other means from causing damage.
6.6 Reaction mass

If a reaction mass is used, it shall be a large and rigid structure compared to the table or carriage.

The resonance of the reaction mass shall have sufficiently high frequencies to avoid distortion of the shortest

shock pulse duration for which the machine is rated.

Seismically suspended reaction masses may be used. They may be installed when the shock has to be

isolated from the surroundings and where reduced dynamic floor loading is required. They may also be used

to control the recoil motion of the shock table or carriage by momentum transfer to the reaction mass.

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ISO 8568:2007(E)

The manufacturer shall provide or recommend the dimensions, masses and the ratio between the moving

masses, including the test specimen and the reaction mass, together with mounting methods.

6.7 Shock pulse-shaping devices and methods

The springs, impact pads and pulse programmers or generators used for controlling the shock pulse (i.e. the

pulse shape, duration and acceleration) depend on the dynamic force-deflection characteristics of the pulse-

shaping device.

If two or more masses are involved in a momentum exchange, the shock motion of each mass shall be taken

into consideration in the design of the shock pulse-shaping device.

Any special equipment needed to form the pulse-shaping devices (e.g. moulds for making lead forms) shall

also be specified. Guidelines for choosing shock-shaping devices are given in Annex A

Similarly, a special electronic shock synthesizing controller typically is used to generate the input signal to an

electrodynamic or servo-hydraulic vibration generator used to generate a shock impulse (see Annex B).

7 Inspection of a shock-testing machine
7.1 General

A procedure shall be specified for performing a shock inspection test for periodic evaluation of system

performance. A periodic inspection of the test equipment characteristics shall be carried out in accordance

with the specified control method or manual.

The inspection interval for a shock-testing machine should be recommended by the manufacturer, and may be

changed by the user depending on the constancy of the characteristics to be certified and the use of the

shock-testing machine with respect to time.
7.2 Preparation procedure

The shock-testing machine shall be supplied with at least two equivalent loads of m and 0,5 m , where

nom nom

m is the mass of the nominal load. If the shock-testing machine is used for testing specimens whose mass

nom

(including the mass of the means for attaching a test specimen) is less then 0,1 m , calibration may be done

nom

with zero load. A monolithic metal cylinder or prism with the ratio of height to diameter from 0,2 to 1,0 is

recommended as an equivalent load. (For electrodynamic vibration generators used in a shock mode, see

ISO 5344.)

NOTE It is possible to use models, adapter plates and attachment fixtures as equivalent load test specimens. In this

case, the results of the calibration of the shock-testing machine are valid only for the mentioned test specimens.

The design of an equivalent load shall enable mounting of an accelerometer at the check point of the table or

carriage. Generally, check point coordinates coincide with the geometrical centre of the table or carriage

surface if there are no other instructions provided by the manufacturer.

Shock-measuring instruments used for the calibration of the shock-testing machine shall provide

measurements in the range of the shock accelerations and pulse durations corresponding to the range of the

shock-testing machine. The total uncertainty of the shock-measuring instruments, including amplitude

nonlinearity of the transducer and dynamic errors of the transducer and amplifier, shall provide the true value

of the shock process as measured in the intended direction at the check point to be within the tolerances

required by IEC 60068-2-27 and IEC 60068-2-81, or within the tolerances specified by the manufacturer.

For a tolerance value equal to 20 %, the total uncertainty related to shock-measuring instruments shall not

exceed 7 % at a confidence level of 95 %. Calibration of the shock-measuring instruments shall be carried out

in accordance with the corresponding part of ISO 5347 or ISO 16063.
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ISO 8568:2007(E)

The accelerometer shall be mounted on the table in accordance with ISO 5348. In order to reduce the error of

shock measurements due to the strain of the table or carriage of the shock-testing machine, and if a

transverse shock motion has to be measured, an additional cube or cylinder may be used. In such cases, the

accelerometer shall be mounted on a steel cube or cylinder, whose maximum size shall not exceed 30 mm.

The use
...