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ISO 1431-1-2012 pdf free download
ISO 1431-1-2012 pdf free download.Rubber, vulcanized or thermoplastic Resistance to ozone cracking
Part 1:Static and dynamic strain testing
Caoutchouc vulcanisé ou thermoplastique — Résistance au craquelage par I’ozone — Partie 1: Essais sous allongement statique et dynamique.
A means of sampling the ozonized air from the vicinity of the test pieces in the chamber and a means of estimating the ozone content shall be provided.
Reference and alternative methods of determining the ozone concentration are described in ISO 1431-3.
5.5 Means of adjusting the gas flow
A mechanism shall be provided that is capable of adjusting the average velocity of the flow of ozonized air in the test chamber to a value of not less than 8 mm/s and preferably to a value between 12 mm/s and 16 mm/s. calculated from the measured gas flow rate in the chamber divided by the effective cross-sectional area of the chamber normal to the gas flow. In tests intended to be comparable, the velocity shall not vary by more than ±10 %. The gas flow rate is the volume throughput of ozonized air in unit time, and this shall be sufficiently high to prevent the ozone concentration in the chamber being significantly reduced owing to ozone destruction by the test pieces. The rate of destruction will vary depending on the rubber being used, the test conditions and other details of the test. As a general guide, it is recommended that the ratio of the exposed surface area of the test pieces to the gas flow rate not exceed 12 s/rn (see Note 1). However, the value of this ratio is not always low enough. In cases where there is doubt, the effects of destruction should be checked experimentally and, if necessary, the test piece area decreased. A diffusing screen or equivalent device shall be used to assist thorough mixing of incoming gas with that in the chamber.
In order to adjust the ozone concentration in the chamber and to exclude the effect of volatile components that are produced by test pieces, air circulation apparatus that draws in fresh ambient air may be used.
If high velocities are desired, a fan may be installed in the chamber to raise the velocity of the ozonized air to 600 mm/s ± 100 mm/s. If this is the case, it shall be stated in the test report.
NOTE 1 The ratio, expressed in seconds per metre (s/rn). is derived from surface area in m2 and volumetric flow rate in m3/s. NOTE 2 DiFferent results might be obtained it different ozonized-air velocities are used.
5.6 Mounting test pieces for static strain testing
Clamps shall be provided to hold the test pieces at the required elongation and with both sides in contact with the ozonized air in such a manner that the longitudinal axis of each test piece is substantially parallel to the direction of gas flow. The clamps shall be made of a material (for example aluminium) which does not readily decompose ozone.
The use of a mechanically rotating carrier mounted in the test chamber and upon which the clamps or frames holding the test pieces are mounted is recommended to equalize the effect of different ozone concentrations in different parts of the chamber. In one example of a suitable carrier, the test pieces move at a speed between 20 mm/s and 25 mm/s in a plane normal to the gas flow and each follows, consecutively, the same path In such a manner that the same position within the chamber is visited by the same test piece every 8 mm to 12 mm, and the area swept by the test pieces (shown shaded in Figure 2) is at least 40 % of the available cross-sectional area of the chamber.ISO 1431-1-2012 pdf free download.
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