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Finite element models of wood baseball bats are a valuable tool to explore the relationship between bat profile and bat durability. However, for such finite element models to be credible, the material models must capture the mechanical response of the wood under consideration. In the current research, a comprehensive experimental program was conducted to characterize the mechanical behavior of maple and ash woods for the range of densities used to make major-league quality baseball bats. The test program included (1) four-point bend testing to determine elastic moduli and strength and (2) Charpy testing to determine strain to failure as a function of strain rate and wood density. The material parameters were subsequently calibrated by completing finite element simulations of the Charpy tests in LS-DYNA using the MAT_WOOD material model. This paper describes the experimental characterization program used to determine material parameters of maple and ash wood species for use in finite element simulations of wood baseball bats.

In a response to reverse the trend of a perceived increase in multi-piece failures (MPFs) of wood baseball bats in Major League baseball games, the Office of the Commissioner of Baseball implemented changes to the Wooden Baseball Bat Specifications (WBBS) in December 2008. These changes introduced bat-supplier regulations that outlined strict quantitative requirements for wood quality and instituted a third-party inspection of professional wooden baseball bats for the 2009 season. Additional changes to the WBBS for the 2010, 2011, and 2012 seasons targeted increasing the density of the wood used to make maple bats, thereby increasing the minimum breaking strength of the wood allowed for these bats. By the completion of the 2014 season, these changes had driven a 65% reduction in the rate of MPFs per game relative to the 2008 season. It is hypothesized that the rate of MPFs can be further reduced if regulations on the allowable geometries of the taper region for the bats used by MLB teams are implemented. To develop a fundamental understanding of the relationship among (1) the angle of the taper (2) the starting point of the taper along the length of the bat, and (3) wood density, a series of generic bat profiles that were subjected to bat/ball impacts was investigated using LS-DYNA. In this paper, the results of these bat/ball impact simulations are shared, and a summary of the various combinations of these geometric parameters on bat stress and strain is presented. The durability information gained from these generic bat profiles is then used to give guidance in understanding why certain bat profiles used in professional baseball have relatively high rates of MPFs while other profiles exhibit a relatively low rate of MPFs.

Major League Baseball (MLB) currently has few restrictions on the bat profiles allowed for use during gameplay. Although current multi-piece failure (MPF) rates are at their lowest in years, there is still room for further improvement by regulating the bat profiles allowed in games. The influence of bat profile tapering was analyzed utilizing finite element models of various known profile geometries to determine the effect on bat durability. LS-DYNA simulations were processed for profiles over a range of maple wood densities that would be currently allowed by MLB regulations. This paper will describe the various modelling studies conducted to determine the factors that comprise a bat profile of good durability. The results of the modelling are compared to on-field data of bat failures during gameplay of known profiles used by MLB players. A profile scoring formula is proposed that is a combination of bat geometrical characteristics and bat wood density. This score is shown to be a good predictor of the relative durability of a given set of bat configurations.

The bats used in Major League Baseball (MLB) are required to be turned from a single piece of wood. Northern white ash had been the wood of choice until the introduction of hard maple in the late 1990s. Since the introduction of maple to the game, there was a perceived increase in the rate of bats to exhibit multiple piece failures (MPF)—both ash and maple. These failures introduced a new aspect to the game that can be a significant factor during play, i.e. pieces of bats going into the field of play, thereby distracting fielders while reacting to the batted ball. Observations of bat breakage in the field and lab testing of bats in controlled conditions have shown the bat durability is a function of wood quality and bat profile. Wood quality is described by the density and the slope of grain of the wood used in the bat. The density and the slope of grain determine the effective strength of the wood. The bat profile is described by the variation in the diameter of the bat along its length. The wood densities and bat profiles which are preferred by players, are typically in direct contradiction with what makes for a durable bat. In this paper, the finite element method is used to develop calibrated models of the breaking of wood bats in controlled lab conditions. The modeling approach is then used to explore how bat profile influences bat durability and what potential changes can be made in bat profile to satisfy player desires while increasing bat durability.

Northern white ash had been the wood of choice for Major League Baseball (MLB) bats until the introduction of hard maple in the late 1990 s. Since the introduction of maple to the game, there has been a perceived increase in the rate of bats to exhibit multi-piece failures (MPF)–both ash and maple. Lab and field data indicate that while a maple bat is as equally likely to crack as an ash bat, maple is three times more likely than ash to exhibit an MPF. In 2009 MLB implemented a number of additional regulations and inspection processes for the wood billets in an effort to reduce the MPF rate. In 2010, another regulation was added requiring that before any new wood species can be introduced to the game, it must it must obtain approval from MLB Baseball Operations. This paper will describe a proposed wood species certification protocol to quantify its durability relative to ash, where ash is being taken as the acceptable baseline for durability. A demonstration of the protocol is conducted using yellow birch with white ash as the baseline. Finite element models of bats made of these two wood species are used to explore the relationship between wood density and bat durability.