In a roller bit, the flat rubber ring (FRR) often needs to apply a certain amount of compression to ensure that its rotation and static sealing surfaces can be stably sealed. For the predicted Mises stress, values smaller than the actual Mises stress due to soft single-axis compression (SAC) stress are predicted by the Yeoh (N = 3) model. To more reasonably predict stress under the static compression of the FRR in the roller bit, the sealing effect of the FRR based on the SAC contact stress and the calculated Mises stress was evaluated by the Yeoh_revised model. Based on the assumption that hydrogenated nitrile-butadiene rubber (HNBR) is isotropic and incompressible, first, we derived the fitting formulas for three types of constitutive models and the Jacobi matrix of the Yeoh_revised model and developed hyperelastic constitutive subroutines. Simultaneously, the accuracy of three models (Yeoh, Yeoh_revised and Ogden) was evaluated by the goodness of fit (R²) to data from three kinds of tensile experiment tests. The highest R² is 0.9771 with the Yeoh_revised model, which merges the advantages of the other two fitting models and effectively improves the Yeoh model’s soft property of SAC contact stress. Additionally, by measuring on-site FRR wear, the maximum Mises stress on the sealing surface calculated based on the Yeoh_revised model is about twice that of the Yeoh model, and the maximum Mises stress on the rotation contact sealing surface is higher than that on the outside (static sealing) surface, which makes the aging of the rotation surface more severe. Thus, it was demonstrated that, on the premise of ensuring FRR sealing contact stress, the Yeoh_revised model can more reasonably predict the sealing effect of the FRR to more precisely calculate Mises stress than the Yeoh model. This also contributes to FRR structure optimization to prolong the service life of the FRR in the roller bit.

This paper developed a horizontal drillstring-wellbore-bit experimental setup based on the similarity of physical behaviors. A data acquisition and control system was established to achieve real-time control over the Rotations Per Minute (RPM) and Rate of Penetration (ROP). Combining experts’ experience and practical drilling experiments, a constant Weight on Bit (WOB) fuzzy controller was designed for rock-breaking experiment. To validate the reliability of the control system, control tests were conducted with different WOB settings at varying RPM. The results indicated that the WOB control error was within 60 N, with an error rate below 3%. Rock drilling experiments were conducted on different rocks. In sandstone drilling experiments, as WOB increased from 600N to 900 N, the ROP, Torque on Bit (TOB), and Stick-slip Vibration Intensity (SSVI) increased significantly, reaching 114.12, 3.6, and 2.97 times of the original values, respectively. When the RPM increased from 21 to 30 RPM, TOB, SSVI, and ROP changed to 1.43, 0.89, and 3.84 times of the original values. The increase in ROP during sandstone drilling was evident, suggesting a moderate increase in drilling parameters, with caution against stick-slip vibrations, which can be mitigated by increasing RPM. In limestone drilling experiments, as WOB increased from 900 to 3300 N, TOB, SSVI, and ROP increased by 2.45, 3.17, and 56.34 times, respectively. When RPM was increased from 45 to 63 RPM, TOB, SSVI, and ROP changed by 0.88, 0.74, and 1.68 times, respectively. Under conditions of high WOB and RPM, the limestone drilling speed increased more significantly.