Rubberized epoxy asphalt trackbeds, incorporating crumb rubber (CR) particles within the cured matrix, demonstrate superior vibration damping and deformation resistance characteristics. Current research remains predominantly focused on macroscopic properties, leaving a critical knowledge gap regarding the particulate-scale mechanisms controlling their dynamic performance under high-speed rail loading. This study bridges this gap through advanced discrete element modeling,developing two-dimensional DEM representations of four sleeper-asphalt composite units with varying CR concentrations (0%, 2%, 4%, and 6%). The models demonstrate exceptional validation accuracy against finite element analyses, with track stiffness predictions within 96.7−152.4 kN/mm range (maximum deviation <2.07%). Our particle-scale investigation of 350 km/h loading cycles reveals three key phenomena: (1) CR content proportionally increases dynamic deformation (stabilizing at 0.5 mm for 6% CR after three loading cycles), while simultaneously enhancing elastic recovery and cumulative deformation resistance; (2) CRparticles redistribute contact forces (0−100 N), with 4% content as a critical threshold shifting behavior from aggregate-dominated to CR-controlled; (3) This transition optimizes stress distribution and force chain homogeneity, achieving optimal balance between flexibility and stability. The findings provide essential insights for designing high-performance rubber-modified railway trackbeds.

The dry-mixed rubberized epoxy asphalt mixture (DREAM) has demonstrated superior mechanical properties. The addition of crumb rubber (CR) improves the damping performance and toughness characteristics of DREAM while offering significant potential for recycling waste materials. However, cracking remains a critical issue for DREAM, necessitating further experimental investigations into its crack resistance performance, especially regarding the sensitivity of evaluation indicators. In this study, semi-circular bending tests were conducted on DREAM with varying CR content under three loading rates and two test temperatures. P-values were utilized to evaluate the sensitivity of nine indicators. Results suggest that not all fracture performance indicators exhibit significant differences due to the varying toughness resulting from the CR content in DREAM. Normalized parameters, such as the pre- and total cracking resistance index (CRI^pre,CRI), tensile stiffness index (TSI), and tensile strength (TS) demonstrate superior performance in distinguishing the effects of CR content and test temperature. Meanwhile, TSI, CRI, and CRI^pre can only significantly distinguish the effects of loading rate in DREAM with high CR content. Moreover, the addition of CR reduces the load-bearing capacity and stiffness of DREAM while increasing its flexibility and crack propagation resistance. Among the effective indicators, TSI is more sensitive to changes in loading rate and test temperature compared to CRI^pre and CRI. This study aims to enhance the understanding of the crack resistance performance and indicator adaptability of DREAM via macro-mechanical experiments and provides guidance for its future applications.

Articular cartilage (AC) is an avascular and flexible connective tissue located on the bone surface in the diarthrodial joints. AC defects are common in the knees of young and physically active individuals. Because of the lack of suitable tissue-engineered artificial matrices, current therapies for AC defects, especially full-thickness AC defects and osteochondral interfaces, fail to replace or regenerate damaged cartilage adequately. With rapid research and development advancements in AC tissue engineering (ACTE), functionalized hydrogels have emerged as promising cartilage matrix substitutes because of their favorable biomechanical properties, water content, swelling ability, cytocompatibility, biodegradability, and lubricating behaviors. They can be rationally designed and conveniently tuned to simulate the extracellular matrix of cartilage. This article briefly introduces the composition, structure, and function of AC and its defects, followed by a comprehensive review of the exquisite (bio)design and (bio)fabrication of functionalized hydrogels for AC repair. Finally, we summarize the challenges encountered in functionalized hydrogel-based strategies for ACTE both in vivo and in vitro and the future directions for clinical translation.

To study the influence of bird impact position and impact posture on the transient response of a fan blade, a smooth particle hydrodynamics (SPH) mallard model established by CT scanning was used to simulate the process of a real bird strikes a high-speed rotating fan with five different impact positions and fifteen different impact attitudes according to the relative speed principle. The effect of impact position and attitude on the transient stress and displacement of the fan blade was obtained. Results show that during the impact process, stress concentration is likely to occur in the blade root and the leading edge, these areas are most susceptible to damage and deformation, and the anterior root has greater stress than the posterior root, which is more likely to be damaged. The impact force on the blade and the stress at the blade root and the leading edge are the largest when the bird strikes the 2/6 blade height position. In the Y-135°, Y-270°, Y-315°, Z-135° and Z-315° impact postures, the equivalent stress of the anterior root is the largest. In the Z-135 impact posture, the equivalent stress of the posterior root is the largest, and the displacement of the leading edge is the largest in the Y-270° impact posture. The results of this study have reference value for the design of anti-bird impact and airworthiness evaluation of fan blades in aero-engine.