Abstract
Bat durability is defined as the relative bat/ball speed that results in bat breakage, i.e., the higher the speed required to initiate bat cracking, the better the durability. In 2008, Major League Baseball added a regulation to the Wooden Baseball Bat Standards concerning Slope-of-Grain (SoG), defined to be the angle of the grain of the wood in the bat with respect to a line parallel to the longitudinal axis of the bat, as part of an overall strategy to reverse what was perceived to be an increasing rate of wood bats breaking into multiple pieces during games. The combination of a set of regulations concerning wood density, prescribed hitting surface, and SoG led to a 30% reduction in the rate of multi-piece failures. In an effort to develop a fundamental understanding of how changes in the SoG impact the resulting bat durability, a popular professional bat profile was examined using the finite element method in a parametric study to quantify the relationship between SoG and bat durability. The parametric study was completed for a span of combinations of wood SoGs, wood species (ash, maple, and yellow birch), inside-pitch and outside-pitch impact locations, and bat/ball impact speeds ranging from 90 to 180 mph (145 to 290 kph). The *MAT_WOOD (MAT_143) material model in LS-DYNA was used for implementing the wood material behavior in the finite element models. A strain-to-failure criterion was also used in the *MAT_ADD_EROSION option to capture the initiation point and subsequent crack propagation as the wood breaks. Differences among the durability responses of the three wood species are presented and discussed. Maple is concluded to be the most likely of the three wood species to result in a Multi-Piece Failure. The finite element models show that while a 0°-SoG bat is not necessarily the most durable configuration, it is the most versatile with respect to bat durability. This study is the first comprehensive numerical investigation as to the relationship between SoG and bat durability. Before this numerical study, only limited empirical data from bats broken during games were available to imply a qualitative relationship between SoG and bat durability. This novel study can serve as the basis for developing future parametric studies using finite element modeling to explore a large set of bat profiles and thereby to develop a deeper fundamental understanding of the relationship among bat profile, wood species, wood SoG, wood density, and on-field durability.
Highlights
In the early years of baseball, bats were made from a wide variety of wood species as players explored various woods in their quest to find the perfect wood
In are relevant to to thethe current finite element modeling studies are Inthis thissection, section,the thebasic basictopics topicswhich which are relevant current finite element modeling studies presented. These topics include a discussion on the lab testing for wood-bat durability, the single-piece are presented. These topics include a discussion on the lab testing for wood-bat durability, the singlefailure (SPF) and a multi-piece failurefailure (MPF) (MPF)
The results of the finite element simulations for a range of wood SoGs were analyzed to the mode of failure and durability as a function of the combination of SoG, impact velocity, wood investigate the mode failure and durability as afor function combination of SoG, impact
Summary
In the early years of baseball, bats were made from a wide variety of wood species as players explored various woods in their quest to find the perfect wood. Northern white ash became the wood of choice as it had the best combination of density, stiffness, and impact resistance properties. Hickory has better impact resistance than the northern white ash, but it is denser than ash, thereby making for a relatively heavy bat. In the late 19th century, the Hillerich family in Louisville, Kentucky cemented the central role of ash bats in baseball when it began manufacturing northern white ash bats for a number of professional teams [1]. The barrel is the Baseball are region. The barrel the intended intended ball bats impact. Theofbarrel of a typical (86.4incm) long1.baseball batisextends from balltip impact region.
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