<p>The mechanical behavior, damage characteristics, and crack evolution of sandstone under tensile stress remain insufficiently understood. In this study, we employed Digital Image Correlation (DIC) technology in combination with laboratory testing and discrete element modeling to investigate the tensile response of sandstone samples from the YC Formation in the Ordos Basin. A correlation between microcrack initiation and macroscopic failure was established through experimental observation and numerical simulation. Results show that conventional Brazilian disc tests tend to underestimate the tensile strength of sandstone due to stress concentrations at the loading points. Flattened disc simulations and experiments reveal a bimodal failure pattern: the flattened surfaces reduce end-concentrated stresses, promote the initiation of central cracks, and delay full crack penetration at the initial peak. In standard disc specimens, local end damage partially relieves stress concentration, producing a pseudo-flattened effect that promotes central crack initiation and propagation. Moreover, compressive stress zones within flattened discs were found to suppress shear crack propagation at the specimen ends. Additional numerical tests indicate a trend in the relationships among (uniaxial compressive strength) UCS, direct tensile strength (DTS), and indirect tensile strengths. These findings enhance the understanding of tensile failure mechanisms in sandstone and offer implications for more reliable evaluation of tensile strength in rock mechanics applications.</p>