Document ID: chunk:federal_register_of_legislation:F2015C00542:reg:254:p2
Version: federal_register_of_legislation:F2015C00542
Segment Type: reg
Provision Reference: reg 254 (pt 2/18)
Character Range: 103407–106298

multiples of the acceleration due to gravity.

              (1)

               The time for which a deceleration of 80 g with ares is continually exceeded and the greatest deceleration of ares should be determined. The HIC-value should be calculated as a measurement of the danger of blunt skull-brain-injuries using the following equation (2):

              (2)

               The integral limits t1 and t2 should be selected in such a way that the integral takes a maximal value.

              4. Test of resistance to abrasion

              4.1. Apparatus

              4.1.1. Abrading instrument[10] shown diagrammatically in Figure 4 and consisting of: A horizontal turntable, with centre clamp, which revolves counter-clockwise at 65 to 75 rev/min.;

Figure 4

Diagram of abrading instrument

               Two weighted parallel arms each carrying a special abrasive wheel freely rotating on a ball-bearing horizontal spindle; each wheel rests on the test specimen under the pressure exerted by a mass of 500 g.

               The turntable of the abrading instrument shall rotate regularly, substantially in one plane (the deviation from this plane shall not be greater than ±0.05 mm at a distance of 1.6 mm from the turntable periphery).

               The wheels shall be mounted in such a way that when they are in contact with the rotating test piece they rotate in opposite directions so as to exert, twice during each rotation of the test piece, a compressive and abrasive action along curved lines over an annular area of about 30 cm2.

              4.1.2. Abrasive wheels[11], each 45 to 50 mm in diameter and 12.5 mm thick, composed of a special finely-screened abrasive embedded in a medium-hard rubber. The wheels shall have a hardness of 72 ± 5 IRHD, as measured at four points equally spaced on the centreline of the abrading surface, the pressure being applied vertically along a diameter of the wheel and the readings being taken 10 seconds after full application of the pressure.

               The abrasive wheels shall be prepared for use by very slow rotation against a sheet of flat glass to ensure that their surface is completely even.

              4.1.3. Light source consisting of an incandescent lamp with its filament contained within a parallelepiped measuring 1.5 mm x 1.5 mm x 3 mm. The voltage at the lamp filament shall be such that the colour temperature is 2,856 ± 50 K. This voltage shall be stabilized within ±1/1,000. The instrument used to check the voltage shall be of appropriate accuracy.

              4.1.4. Optical system consisting of a lens with a focal length f of at least 500 mm and corrected for chromatic aberrations. The full aperture of the lens shall not exceed f/20. The distance between the lens and the light source shall be adjusted in order to obtain a light beam which is substantially parallel. A diaphragm