Soft matter mechanics of baseball's Rubbing Mud.

Autor:	Pradeep S; Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA 19104.; Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104., Chen X; Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104., Seiphoori A; Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA 19104.; Norwegian Geotechnical Institute, Houston, TX 77043., Vann DR; Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA 19104., Arratia PE; Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104., Jerolmack DJ; Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA 19104.; Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104.
Jazyk:	angličtina
Zdroj:	Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2024 Nov 19; Vol. 121 (47), pp. e2413514121. Date of Electronic Publication: 2024 Nov 04.
DOI:	10.1073/pnas.2413514121
Abstrakt:	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. Competing Interests: Competing interests statement:The authors declare no competing interest.
Databáze:	MEDLINE
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