The eccentric errors of planetary roller screw mechanism (PRSM) affect the contact kinematic characteristics and exacerbate the cumulative wear of thread pairs, which will reduce its transmission accuracy and reliability. Hence, it is significant to investigate the cumulative wear of PRSM with the eccentric errors. In this work, based on the conjugate surface contact condition and Archard wear theory, the sliding speed and cumulative wear depth of PRSM with eccentricity errors are modeled, respectively. The effects of eccentric errors on the sliding velocities and cumulative wear depth of PRSM are investigated. It has been determined that the eccentric errors of the screw and nut do not cause the sliding motion in the nut–roller contact region (NRCR). However, there are noticeable variations in sliding velocity and cumulative wear depth in the screw–roller contact region (SRCR). The eccentric errors of the screw and nut have a combined effect on the sliding velocity and wear between the screw and roller. This investigation and finding can provide a valuable reference for the processing and assembly of PRSM.

Stiffness-tunable mechanical metamaterials have attracted significant attention due to their potential for adaptive structures and systems. However, current designs often suffer from limited tuning ranges or discontinuous variations in stiffness. To address these challenges, this study presents a novel rotation-based mechanical metamaterial unit capable of continuous stiffness modulation via angular adjustment. Experimental and numerical analyses demonstrate an exceptional 22-fold variation in stiffness, ranging from 123.71 N mm ⁻¹ to 2751.52 N mm ⁻¹ , significantly outperforming existing tunable metamaterials. Parametric studies reveal the influence of key geometric parameters, including spoke width, cutout radius, and thickness, on stiffness behavior, while structural arrangement strategies further enhance the mechanical programmability. This work establishes a robust foundation for the design of adaptive systems with broad applicability in fields such as robotics, aerospace, and precision machinery.