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In tire industry, fatigue crack propagation in elastomers is studied toimprove the service life of products. Natural rubber (NR) is a key compound in tires,because of its remarkable mechanical properties and more particularly its excellentresistance to fatigue crack growth as compared to synthetic rubbers. To explain thesegood properties, the literature often mentions the strain-induced crystallization (SIC)phenomenon that takes place at the tip of fatigue cracks in NR. In this study, an originalexperimental set-up that couples synchrotron radiation with a homemade fatiguemachine has been developed to study SIC and multiaxiality around fatigue cracks inNR. During uninterrupted fatigue tests, recording of wide-angle X-ray diffractionpatterns is performed in the crack tip region. It provides a 2D spatial distribution ofeither crystallinity or principal strain directions. The influence of loading conditions(maximum elongation and non-relaxing loading conditions) on the size of thecrystallized zone is particularly investigated, in order to relate it to the fatigue crackpropagation rates. Finally, the multiaxiality results, in terms of principal straindirections, give good correlation with results obtained by digital image correlation andfinite element analysis.