Flex-Cracking and Crack Growth Tests Some Important Factors

Abstract

Abstract Flex-cracking has been a major cause of failure in rubber articles for many years and since the early 1930's various test methods have been suggested. The whole subject of the mechanism of flex-cracking and flex-cracking tests was reviewed recently, and in 1950 Committee ISO/TC/45 agreed that only the De Mattia machine should be considered for international standardization and that the question of crack growth should be tackled before flex-cracking. Cooperative tests, following the suggested crack-growth procedure, are being carried out in nine laboratories, four laboratories in the United Kingdom, one in Austria, one in France, one in Holland, one in Italy, and one in the United States. Preliminary results show that agreement between laboratories is not good and support the view that the greatest possible care and attention must be given to experimental details if reproducible and comparable results are to be obtained in different laboratories. In the earlier paper referred to above, three important aspects of accuracy of testing are defined as: (a) the accuracy of the measurement of flex-cracking and crack-growth resistance of any one sample; (b) the degree of reproducibility of the test conditions; (c) the degree of reproducibility of the test-specimens.