ENERGY DISSSIPATION TEST
Seats and head restraints play a critical role in occupant protection and personal comfort. The seat and head restraints can be
subjected to substantial forces in a crash so they must be carefully designed, constructed and installed to ensure that they provide
adequate protection. So various tests are carried out on vehicles prior to launch to ensure passenger safety. Accordingly the vehicle
standards are created. Energy Dissipation test is one such test on head restraints and seats. It complies with AIS 016/2000 or ECE
The function of this vehicle test is to specify requirements for the design of ‘Head Restraints’ so as to limit the severity of injury in
the event of crash and rear-end impacts and to ensure that the ‘Head Restraint’ cannot be adjusted too low.
EXISTING SET UP AT ARAI ,INDIA
1.2.1 SET UP:
The seat, as mounted in the vehicle, shall be firmly secured to the test bench with the attachment parts provided by the manufacturer, so as to remain stationary when the impact is applied. The seat-back, if adjustable, shall be locked in the position specified in the Regulation. If the seat is fitted with a head restraint, the head restraint shall be mounted on the seat-back as in the vehicle.
1.2.2 TEST APPARATUS:
This apparatus consists of a pendulum whose pivot is supported by ball-bearings and whose reduced mass at its centre of percussion is 6.8 kg. The lower extremity of the pendulum consists of a rigid head form 165 mm in diameter whose center is identical with the centre of percussion of the pendulum. The head form shall be fitted with two accelerometers and a speed-measuring device, all capable of measuring values in the direction of impact.
1.2.3 RECORDING INSTRUMENTS:
The recording instruments used shall be such that measurements can be made with the following degrees of accuracy :
· Accuracy = ± 5 per cent of the actual value;
· Frequency class of data channel: class 600 corresponding to ISO Standard 6487 (1980);
· Cross-axis sensitivity = < 5 per cent of the lowest point on the scale.
· Accuracy: ± 2.5 per cent of the actual value;
· Sensitivity: 0.5 km/h.
1.2.6 TIME RECORDING:
The instrumentation shall enable the action to be recorded throughout its duration and readings to be made to within one one-thousandth of a second; the beginning of the impact at the moment of first contact between the head form and the item being tested shall be detected on the recordings used for analysing the test.
(A) With the seat installed as indicated in set-up, the direction of impact from the rear towards the front shall be on a longitudinal plane at a downwards angle of 45° from the vertical and in vertical plane.
1. In the case of separate seats without head restraints, this area shall include the rear part of the seat-back between the longitudinal vertical planes situated at 100 mm on either side of the longitudinal median plane of the seat centre line, and above a plane perpendicular to the reference line 100 mm below the top of the seat-back.
2. In the case of bench seats without head restraints, this area shall extend between the longitudinal vertical planes situated at 100 mm on either side of the longitudinal median plane of each designated outboard seating position defined by the manufacturer and above a plane perpendicular to the reference line 100 mm below the top of the seat-back.
3. In the case of seats or bench seats with head restraints, this area shall extend between the longitudinal vertical planes, on both side of and 70 mm from the longitudinal median plane of the seat or of the seating position concerned and situated above the plane perpendicular to the reference line 635 mm from the R point. For the test, the head restraint, if adjustable shall be placed in the most unfavorable position (generally the highest) permitted by its adjustment system.
1. In the case of seats or bench seats
without head restraints and seats or bench seats with detachable or separate
head restraints, area 2 shall extend above a plane perpendicular to the
reference line 100 mm distant from the top of the seat-back, other than parts
of area 1.
2. In the case of seats or bench seats with integrated head restraints, area 2 shall extend above a plane perpendicular to the reference line 440 mm distant from the R point of the seat or of the seating position concerned, other than parts of area 1.
(B) The impact points shall be selected by the test laboratory in area 1 as defined in above paragraph, or if necessary in area 2 as defined in above paragraph on surfaces exhibiting radii of curvature less than 5 mm.
(C) The head form shall strike the test point at a speed of 24.1 ± 0.5 km/h: this speed shall be achieved either by the mere energy of propulsion or by using an additional impelling device.
____ INITIAL POSITION _ _ _ _ POSITION UNDER LOAD
FIG: SEAT DURING IMPACT
The deceleration rate shall be taken as the average of the readings on the two decelerometers.