Soft matter mechanics of baseball's Rubbing Mud

• 成果类型: Article
• 署名作者: Pradeep, Shravan; Chen, Xiangyu; Seiphoori, Ali; Vann, David R.; Arratia, Paulo E.; Jerolmack, Douglas J.
• 署名单位: University of Pennsylvania; University of Pennsylvania; Norwegian Geotechnical Institute, NGI
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-12295
• DOI: 10.1073/pnas.2413514121
• 发表日期: 2024-11-19
• 关键词: suspensions; viscoelasticity; locomotion; adhesion; rheology; aluminum; BEHAVIOR; surface

摘要

Researchers looking for sustainable materials with optimal mechanical properties may draw inspiration from a baseball tradition. For nearly 100 y, a mysterious mud harvested from an undisclosed river site in New Jersey (USA) has been the agent of choice in the USA's Major League Baseball for de-glossing new baseballs. It is unclear, however, what makes this Rubbing Mud work. Here, we perform a multiscale investigation of the rheology and tribology of this mud material under baseball-relevant conditions and identify three mechanisms by which the mud alters the surface properties of the baseball. First, the mud creates a more uniform baseball surface by filling in pores in the leather; this is possible because of its relatively high cohesion (clays and organics) making the material remarkably shear thinning. Second, the residue of cohesive particles coating the baseball effectively doubles contact adhesion. Third, a sparse population of angular sand grains are bonded to the baseball by clay-sized particles, leaving a studded surface that enhances friction. The proportions of cohesive, frictional, and viscous elements in Rubbing Mud conspire to create a soft material with an unusual mix of properties, that could find other applications in the development of sustainable geomaterials. Our improved understanding of the flow and friction of natural muds may also find use in modeling natural hazards such as mudslides and for locomotion in muddy environments.