BS 903-A8:1990 pdf free.Physical testingof rubber — Method for determination ofrebound resilience.
BS 903-A8 Remove the test piece holder and allow thependulum and attachments to oscillate freely.Record the amplitude of successive swings in thesame direction. Report the damping correctionfactor as one-quarter of the difference in amplitudebetween successive swings in the same direction.Repeat this procedure for several different
amplitudes covering the required range of resiliencevalues.
NOTE If a method of observing impact and rebound velocities isused, this correction for damping is not required.
Ensure that the test piece and test piece holder arethoroughly clean. Wipe the rear surface of the testpiece with solvent, to reduce shuffle. Bring the testpiece holder to the test temperature, insert the testpiece and leave it in position for a sufficient time forit to reach the test temperature.A period of at least 15 min for 7 mm thick test pieces is required.This period, however, may be shortened byfirst bringing the test piece to the test temperaturein a chamber separate from the test piece holder.
For tests at low temperatures, make provision forthe prevention of the formation of frost on the testpiece.
If the test piece appears to be tacky, lightly dust thefront surface only with talc.
NOTE Errors can arise if the test piece temperature is assumedto be that of the test piece holder. It is therefore recommendedthat the temperature of the test piece be measured by means of afine wire thermocouple inserted into the rubber in such a waythat it does not interfere with the pendulum.
Subject the test piece to a number of impacts of thependulum from its release position of 45°, in rapidsuccession, until the reading obtained from threeconsecutive impacts agrees to within 1 % point ofresilience.Use the mean value of these readings inthe calculation of results.
NOTE When using a non standard test piece (see note to 3.3),although results will not necessarily equate with those obtainedusing a standard test piece,it has been found useful to release thependulum at 25°to the horizontal, to reduce the energy of impactparticularly when softer rubbers are being tested.BS 903-A8 pdf download.