ISO 7096:2000 pdf free download.Earth-moving machinery – Laboratory evaluation of operator seat vibration.
The operators of earth-moving machinery are often exposed to a low frequency vibration environment partly caused by the movement of the vehicles over uneven ground and the tasks carried out. The seat constitutes the last stage of suspension before the driver. To be efficient at attenuating the vibration, the suspension seat should be chosen according to the dynamic characteristics of the vehicle. The design of the seat and its suspension are a Compromise between the requirements of reducing the effect of vibration and shock on the operator and providing him with stable support so that he can control the machine effectively.
Thus, seat vibration attenuation is a compromise of a number of factors and the selection of seat vibration parameters needs to be taken in context with the other requirements for the seat.
The performance criteria provided in ISO 7096 have been set in accordance with what is attainable using what is at present the best design practice. They do not necessarily ensure the complete protection of the operator against the effects of vibration and shock. They may be revised in the light of future developments and improvements in suspension design.
The test inputs included in ISO 7096 are based on a very large number of measurements taken in situ on earth-moving machinery used under severe but typical operating conditions. The test methods are based on ISO 10326-1, which is a general method applicable to seats for different types of vehicles.
1.1 ISO 7096 specifies, in accordance with ISO 10326-1, a laboratory method for measuring and evaluating the effectiveness of the seat suspension in reducing the vertical whole-body vibration transmitted to the operator of earth-moving machines at frequencies between 1 Hz and 20 Hz, It also specifies acceptance criteria for application to seats on different machines.
1.2 This International Standard is applicable to operator seats used on earth-moving machines as defined in
ISO 6165.
1.3 ISO 7096 defines the input spectral classes required for the following earth-moving machines. Each class defines a group of machines having similar vibration characteristics:
— rigid frame dumpers >4 500 kg operating mass1
— articulated frame dumpers scrapers without axle or frame suspension2 wheel-loaders > 4 500 kg operating mass1 graders
wheel-dozers
— soil compactors (wheel type) backhoe-loaders
— crawler loaders
— crawler-dozers 50 000 kg operating mass1)’‘
1.5 The tests and criteria defined in ISO 7096 are intended for operator seats used in earth- moving machines of conventional design.
NOTE Other tests may be appropriate for machines with design features that result in significantly different vibration characteristics.
1.6 Vibration which reaches the operator other than through his seat, for example that sensed by his feet on the platform or control pedals or by his hands on the steering-wheel, is not covered.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of ISO 7096. For dated references, subsequent amendments to, or revisions of. any of these publications do not apply. However, parties to agreements based on ISO 7096 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards.
ISO 2041:1990, Vibration and shock — Vocabulary.
ISO 2631-1:1997, Mechanical vibration and shock — Evaluation of human exposure to whole-body vibration — Part 1: General requirements.
ISO 6016:1998, Earth-moving machinery — Methods of measuring the masses of whole machines, their equipment
and components.
ISO 6165:1997, EarTh-moving machinery — Basic types — Vocabulary.
ISO 8041:1990, Human response to vibration — Measuring instrumentation.
ISO 10326-1:1992. Mechanical vibration — Laboratory method for evaluating vehicle seat vibration — Part 1: Basic requ#emerits.
ISO 13090-1:1998, Mechanical vibration and shock — Guidance on safety aspects of tests and experiments with people — Part 1: Exposure to whole-body mechanical vibration and repeated shock.
4 General
4.1 The laboratory-simulated machine vertical vibration, specified as input spectral class, is based on representative measured data from machines in severe but typical working conditions. The input spectral class is a representative envelope for the machines within the class, as measured under severe conditions.
4.2 Two criteria are used for the evaluation of seat:
a) the Seat Effective Amplitude Transmissibility (SEAT) factor according to ISO 10326-1:1992. 9.1, but with frequency weighting according to ISO 2631-1;
b) the maximum transmissibility ratio in the damping test according to ISO 10326-1:1992, 9.2.
4.3 The measuring equipment shall be in accordance with ISO 8041 (type 1 instrument) and ISO 10326-1:1992, clauses 4 and 5. The frequency weighting shall include the effects of the band limiting filters, and be in accordance with ISO 2631-1.
4.4 Safety precautions shall be in accordance with ISO 13090-1.
Any compliant end-stops or devices normally fitted to production versions of the seat to be tested to minimise the
effect of suspension overtravel shall be in place for the dynamic tests.
5 Test conditions and test procedure
The test conditions and test procedure shall be in accordance with ISO 10326-1:1992, clauses 7 and 8.
5.1 Simulation of vibration See ISO 10326-1:1992, clause 5.
The operator seat for the test shall be representative of series-produced models, with regard to construction, static and vibration characteristics and other features which may affect the vibration test result. Before the test, the suspension seats shall be run-in under conditions stipulated by the manufacturer. If the manufacturer does not state such conditions, then the seat shall be run-in for 5 000 cycles, with measurements at 1 000 cycle intervals.
For this purpose, the seat shall be loaded with an inert mass of 75 kg and adjusted to the mass in accordance with the manufacturers instructions. The seat and suspension shall be mounted on the platform of a vibrator, and a sinusoidal input vibration shall be applied to the platform at approximately the suspension natural frequency. This input vibration shall have a peak to peak displacement sufficient to cause movement of the seat suspension over approximately 75 % of its stroke. A platform peak to peak displacement of approximately 40 % of the seat suspension stroke is likely to achieve this. Care should be taken to ensure against overheating of the suspension damper during the running-in, for which forced cooling is acceptable.
The seat shall be considered to have been run-in if the value for the vertical transmissibility remains within a tolerance of ± 5 % when three successive measurements are performed under the condition described above. The time interval between two measurements shall be half an hour, or 1 000 cycles (whichever is less), with the seat being constantly run-in.
The seat shall be adjusted to the weight of the test person in accordance with the manufacturer’s instructions.
With seats where the suspension stroke available is unaffected by the adjustment for seat height or test person weight, testing shall be performed with the seat adjusted to the centre of the stroke.
With seats where the suspension stroke available is affected by the adjustment of the seat height or by test person weight, testing shall be performed in the lowest position which provides the full working suspension stroke as specified by the seat manufacturer.
When the inclination of the backrest is adjustable, it shall be set approximately upright, inclined slightly backwards (approximately 10° ± 5°).
5.3 Test person and posture
The simulated input vibration test shall be performed with two persons. The light person shall have a total mass of
52 kg to 55 kg, of which not more than 5 kg may be carried in a belt around the waist. The heavy person shall have
a total mass of 98 kg to 103 kg, of which not more than 8 kg may be carried in a belt around the waist.
The simulated input vibration used to determine the SEAT is defined in accordance with ISO 10326-1:1992, 8.1, but the frequency weighting shall be in accordance with ISO 2631-1. The test input for each class is defined by a power spectral density, G1,(j), of the vertical (Z axis) acceleration of the vibrating platform, and by the unweighted mis vertical accelerations on that platform (ap12. ap34).
The vibration characteristics for each input spectral class EM 1 through EM 9 are shown in Figures 2 through 10, respectively. Equations for the acceleration power spectral density curves of Figures 2 to 10 are included in Table 2. The curves defined by these equations are the target values to be produced at the base of the seat for the simulated input vibration test of 5.5.2.
The input vibration shall be determined (calculated) without components at frequencies outside the frequency range defined byft andh.
Table 4 further defines the test input values for the actual test input PSO at the base of the seat. Three tests shall be performed for each test person and each input vibration in accordance with ISO 10326-1:1992,
9.1. The effective duration of each test shall be at least 180 s.
If none of the SEAT values relating to one particular test configuration deviate by more than ± 5 % from the arithmetic mean, then, in terms of repeatability, the three tests mentioned above shall be deemed to be valid. If this is not the case, as many series of three tests as are necessary to satisfy this requirement shall be carried out.
The sampling time 7’ and resolution bandwidth 8e’ shall satisfy the following:
2 X Be T8> 140
Be c 0,5 Hz
NOTE 1 Class EM 7 is also used to test agricultural wteeled tractor seats for class I tractor (see ISO 5007:1990, AgricWruraI wtieeted tractors — Operators seat — Laboratory measurement of transmitted vibration).
NOTE 2 Any means, including double Integralors, analog signal generators and filters, and digital signal generators with digital-to-analog converters, may be used to produce the required PSO and mis characteristics at the base of the seat for the simulated input vibration test.