BS ISO 6721-9:2019 pdf free.Plastics一Determination of dynamic mechanical properties.
Apply a sonic pulse to the specimen, and measure the arrival time tA (s) to an accuracy of士0,5 us.Repeat the measurements described in 9.3.1 and 9.3.2 for the same specimen at least three different separation distances between the transducers. In order to get good accuracy, the values of the distance should be selected so as to be distributed uniformly within the whole range of the distance suitable for determining the arrival time (See Figure 2).The precision of this test method is not known because interlaboratory data are not available due to the difficulty in finding laboratories with test equipment capable of operating at the same frequency. It is recognized that the properties of thermoplastics are time-dependent, and the pulse propagation time and hence the dynamic modulus depend closely on the frequency of the sonic pulse used. For information purposes, however, the within-laboratory standard deviation has been determined using data from one laboratory which tested four different materials (see Annex A). The test report shall contain the following information:a) a reference to this document, i.e. ISO 6721-9;  b) all details necessary for complete identification of the material tested, including type, source, manufacturer’s code number, form and previous history where these are known; c) for films or sheets, their thickness and, if applicable, the direction of the major axes of the test specimens in relation to some feature of the films or sheets; d) the shape and dimensions of the test specimens; e) the method of preparing the test specimens;  f) details of the conditioning of the test specimens;When this method is used with certain materials, consideration should be given to various factors that can lead to a decrease in the repeatability of the measured values. Such factors include the following: a) poor contact between the specimen and the transducers, which may give rise to a low amplitude of the sonic pulse and associated errors in determining the pulse propagation time; b) anisotropy in the properties of the material, caused by molecular orientation, which will give rise to a dependence of the pulse propagation time on direction in the specimen; c) the presence of filler or reinforcement in the material such that the distribution or orientation of the filler or reinforcement affects the pulse propagation time. BS ISO 6721-9 pdf download.