Rubber, leather, synthetic leather, soles, such as continuous bending fatigue, observe the degree of crack in order to understand or compare their durability.

JIS K6260  De Mattia

ISO 132, the ink type

ASTM D813 rubber metamorphic - test method of crack extension
ASTM D430 rubber worse -- dynamic fatigue test method
BS - 903 rubber physical test: determination of the abrasion resistance
GB/T 13934 vulcanized rubber and thermoplastic rubber flexible crack and the determination of crack growth