ISO 16750-3:2012

INTERNATIONAL ISO
STANDARD 16750-3
Third edition
2012-12-15
Road vehicles — Environmental
conditions and testing for electrical
and electronic equipment —
Part 3:
Mechanical loads
Véhicules routiers — Spécifications d’environnement et essais de
l’équipement électrique et électronique —
Partie 3: Contraintes mécaniques
Reference number
©
ISO 2012
© ISO 2012
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Published in Switzerland
ii © ISO 2012 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Tests and requirements . 1
4.1 Vibration . 1
4.2 Mechanical shock .27
4.3 Free fall .29
4.4 Surface strength/scratch and abrasion resistance .29
4.5 Gravel bombardment .29
5 Code letters for mechanical loads .29
6 Documentation .30
Annex A (informative) Guideline for the development of test profiles for vibration tests .32
Annex B (informative) Recommended mechanical requirements for equipment depending on the
mounting location .44
Bibliography .46
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 16750-3 was prepared by Technical Committee ISO/TC 22, Road vehicle, Subcommittee SC 3,
Electrical and electronical equipment.
This third edition cancels and replaces the second edition (ISO 16750-3:2007), which has been
technically revised.
ISO 16750 consists of the following parts, under the general title Road vehicles — Environmental conditions
and testing for electrical and electronic equipment:
— Part 1: General
— Part 2: Electrical loads
— Part 3: Mechanical loads
— Part 4: Climatic loads
— Part 5: Chemical loads
iv © ISO 2012 – All rights reserved

INTERNATIONAL STANDARD ISO 16750-3:2012(E)
Road vehicles — Environmental conditions and testing for
electrical and electronic equipment —
Part 3:
Mechanical loads
1 Scope
This part of ISO 16750 applies to electric and electronic systems/components for road vehicles. It
describes the potential environmental stresses and specifies tests and requirements recommended for
the specific mounting location on/in the vehicle.
This part of ISO 16750 describes mechanical loads.
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 16750-1, Road vehicles — Environmental conditions and testing for electrical and electronic equipment —
Part 1: General
IEC 60068-2, 6, Environmental testing — Part 2-6: Testing, Test Fc: Vibration (Sinusoidal)
IEC 60068-2, 14, Basic environmental testing procedures — Part 2-14: Tests — Test Nb: Change of temperature
IEC 60068-2, 64, Environmental testing — Part 2-64: Test methods — Test Fh — Vibration, broad-band
random (digital control) and guidance
IEC 60068-2, 80, Environmental testing — Part 2-80: Tests — Test Fi: Vibration — Mixed mode testing
IEC 60068-2-31, Environmental testing procedures — Part 2: Tests; Test Ec: Free fall, Clause 5.2
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 16750-1 apply.
4 Tests and requirements
4.1 Vibration
4.1.1 General
The vibration test methods specified consider various levels of vibration severities applicable to on-
board electrical and electronic equipment. It is recommended that the vehicle manufacturer and
supplier choose the test method, the environmental temperature and vibration parameters depending
on the specific mounting location.
Following the expressions in MIL-STD please notice:
When applied properly, the environmental management and engineering processes described in this part
of ISO 16750 can be of enormous value in generating confidence in the environmental worthiness and
overall durability. However, it is important to recognize that there are limitations inherent in laboratory
testing that make it imperative to use proper caution and engineering judgement when extrapolating these
laboratory results to results that may be obtained under actual service conditions. In many cases, real-
world environmental stresses (singularly or in combination) cannot be duplicated practically or reliably in
test laboratories. Therefore, users of this part of ISO 16750 should not assume that a system or component
that passes laboratory tests of this part of ISO 16750 would also pass field/fleet verification trials.
— “The specified values are the best estimation one can get up to the moment when results from
measurements in the car are received – but they do not replace a car measurement!”
The specified values apply to direct mounting in defined mounting locations. Using a bracket for
mounting can result in higher or lower loads. If the device under test (DUT) is used in the vehicle with a
bracket then all vibration and mechanical shock test shall be done with this bracket.
Carry out the vibration with the DUT suitably mounted on a vibration table. The mounting method(s)
used shall be noted in the test report. Carry out the frequency variation by logarithmic sweeping of 0,5
octave/minute for sinusoidal tests and the sinusoidal part of sine on random tests. The scope of the
recommended vibration tests is to avoid malfunctions and breakage mainly due to fatigue in the field.
Testing for wear has special requirements and is not covered in this part of ISO 16750.
Loads outside of the designated test frequency ranges are to be considered separately.
NOTE Deviations from the load on the DUT can result, should vibration testing be carried out according to
this part of ISO 16750 on a heavy and bulky DUT, as mounting rigidity and dynamic reaction on the vibrator table
excitation are different compared to the situation in the vehicle. This deviation can be minimized by applying the
average control method (see Annex A).
Application of the weighted average control method according to IEC 60068-2, 64 is to be agreed upon.
Subject the DUT during the vibration test to the temperature cycle according to IEC 60068-2, 14, with
electric operation according to diagram 1. Alternatively, a test at constant temperature may be agreed on.
Operate the DUT electrically as indicated in Figure 1 at T (short functional test after the DUT completely
min
reached T . This functional test shall be as short as possible ― only long enough to check the proper
min)
performance of the DUT. This minimizes self-heating of the DUT. Additional electrical operation of the
DUT between 210 min and 410 min of the cycle (see Figure 1).
Additional drying of test chamber air is not permitted.
In the vehicle, vibration stress can occur together with extremely low or high temperatures; for this
reason, this interaction between mechanical and temperature stress is simulated in the test, too. A
failure mechanism is, for example, a plastic part of a system/component, which mellows due to the high
temperature and cannot withstand the acceleration under this condition.
2 © ISO 2012 – All rights reserved

Key
Y temperature [°C]
X time [min]
a
Operating mode 3.2 according to ISO 16750-1.
b
Operating mode 2.1 according to ISO 16750-1.
c
One cycle.
Figure 1 — Temperature profile for the vibration test
Table 1 — Temperature versus time for the vibration test
Time Temperature
min °C
0 20
60 -40
150 -40
210 20
a
300 T
max
a
410 T
max
480 20
a
See ISO 16750-4.
4.1.2 Tests
4.1.2.1 Test I — Passenger car, engine
4.1.2.1.1 Purpose
This test checks the DUT for malfunctions and breakage caused by vibration.
The vibrations of a piston engine can be split up into two kinds: Sinusoidal vibration which results from the
unbalanced mass forces in the cylinders and random noise due to all other vibration-schemes of an engine,
e.g. closing of valves. In the lowest frequency range from 10 Hz to 100 Hz the influence of rough-road
conditions is taken into account. The main failure to be identified by this test is breakage due to fatigue.
NOTE 1 Road profile usually has negligible impact on engine-mounted components. Shock inputs are effectively
isolated by suspension, and engine-mounting systems.
The test profiles specified in the following clauses apply to loads generated by (four stroke)
reciprocating engines.
NOTE 2 If the DUT is to be tested for a specific resonance effect, then a resonance dwell test according to 8.3.2
of IEC 60068-2, 6:2007 can also be applied.
4.1.2.1.2 Test
4.1.2.1.2.1 General
It is required to perform this test as a mixed mode vibration test according to IEC 60068-2, 80.
NOTE The test duration is based on A.4. The temperature in the chamber is above room temperature (RT) at
the end of the test (2 3/4 temperature cycles).
4.1.2.1.2.2 Sinusoidal vibration
Perform the test according to IEC 60068-2, 6, but using a sweep rate of ≤ 0,5 octave/minute. Use a test
duration of 22 h for each plane of the DUT.
Use curve 1 in Table 2/Figure 2 for DUT intended for mounting on engines with 5 cylinders or fewer.
Use curve 2 in Table 2/Figure 2 for DUT test intended for mounting on engines with 6 cylinders or more.
Both curves may be combined to cover all engine types in one test.
Key
Y amplitude of acceleration [m/s ]
X frequency [Hz]
curve 1 (≤5 cylinders)
curve 2 (>5 cylinders)
Figure 2 — Vibration severity curves
4 © ISO 2012 – All rights reserved

Table 2 — Values for max. acceleration versus frequency
Curve 1 (see Figure 2)
Frequency Amplitude of acceleration
Hz m/s
100 100
200 200
240 200
270 100
440 100
Curve 2 (see Figure 2)
Frequency Amplitude of acceleration
Hz m/s
100 100
150 150
440 150
Combination
Frequency Amplitude of acceleration
Hz m/s
100 100
150 150
200 200
240 200
255 150
440 150
4.1.2.1.2.3 Random vibration
Perform the test according to IEC 60068-2, 64. Use a test duration of 22 h for each plane of the DUT.
The r.m.s. acceleration value shall be 181 m/s .
The PSD versus frequency are referred to in Figure 3 and Table 3
NOTE The Power Spectral Density (PSD) values (rand
...