ANNEX V U.K.TEST PROCEDURE FOR CHECKING ENERGY DISSIPATION

1. SETTING UP, TEST APPARATUS, RECORDING INSTRUMENTS AND PROCEDURE U.K.

1.1. Setting up U.K.

The head restraint must be fitted and tested on the seat of the vehicle for which it is intended. The seat must be firmly secured to the test bench so that it does not move under impact.

1.2. Test apparatus U.K.

1.2.1. This apparatus consists of a pendulum whose pivot is supported by ball-bearings and whose reduced mass(1) at its centre of percussion is 6·8 kg. The lower extremity of the pendulum consists of a rigid headform 165 mm in diameter whose centre is identical with the centre of percussion of the pendulum. U.K.

1.2.2. The headform is fitted with two accelerometers and a speed-measuring device, all capable of measuring values in the direction of impact. U.K.

1.3. Recording instruments U.K.

The recording instruments used must be such that measurements can be made with the following degrees of accuracy:

1.3.1. Acceleration: U.K.

• accuracy: ± 5 % of the real value,

• frequency response: up to 1 000 Hz

• cross-axis sensitivity: < 5 % of the lowest point on the scale.

1.3.2. Speed: U.K.

• accuracy: ± 2·5 % of the real value,

• sensitivity: 0·5 km/h.

1.3.3. Time recording: U.K.

• the instrumentation must enable the action to be recorded throughout its duration and readings to be made within one thousandth of a second,

• the beginning of the impact at the moment of first contact between the headform and the head restraint being tested is noted on the recordings used for analyzing the test.

1.4. Test procedure U.K.

1.4.1. The surface to be tested must be so placed that the pendulum will strike the surface perpendicular to the point concerned. U.K.

1.4.2. The headform must strike the test item at a speed of 24·1 km/h this speed is achieved either by the mere energy of propulsion or by using an additional propelling device. U.K.

(1)

The relationship of the reduced mass ‘m_r’ of the pendulum to the total mass ‘m’ of the pendulum at a distance ‘a’ between the centre of percussion and the axis of rotation and at a distance ‘l’ between the centre of gravity and the axis of rotation is given by the formula: ·