Thesis
Reducing the effect of ball variation in bat performance measurements
Washington State University
Master of Science (MS), Washington State University
2010
Handle:
https://hdl.handle.net/2376/101818
Abstract
The performance of softball bats depend on the properties of the ball. Three of these ball properties are the weight, elasticity and stiffness. They vary with the type of material used in the manufacturing. It is desired to remove these properties from standardized testing. Previous work has shown that weight dependence is readily accounted for in bat performance measurements. Attempts to remove elasticity and stiffness dependence have not been successful. The following analyzes a method to determine bat performance, independent of the ball. Elasticity of the ball was accounted for through a cylindrical coefficient of restitution (CCOR). Ball stiffness (kT) was found from a high speed impact and calculated using four different techniques. All four approaches maintained relatively the same trend. Three bats varying in performance were compared with a large range of different ball types. In some cases the normalizing technique eliminated the ball properties from the bat performance however, in other cases it did not. The procedure for removing CCOR worked for a wider range of balls than kT. Overall, with the different ball models a medium performance bat had a range in Batted Ball Speed (BBS) from 104 mph to 93 mph. The range in the normalized BBS reduced to from 98 mph to 92 mph. Balls with low kT and balls with a combined low CCOR and high kT provided the largest range in BBS. A numerical model was developed and analyzed bat-ball impacts in more detail than was possible experimentally. In the model the BBS of a medium performance bat had a range from 105 mph to 92 mph, the normalized BBS had a range from 99 mph to 94 mph (similar to the experimental results). It was found that during impact the effective bat stiffness changed with kT and the bat was not elastic (a common assumption). A technique was developed to account for the changes in bat stiffness that reduced the range in normalized BBS to between 97 mph and 95 mph. The improvement demonstrated that the effect of the ball in the bat stiffness is the primary limitation of normalizing bat performance.
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Details
- Title
- Reducing the effect of ball variation in bat performance measurements
- Creators
- Warren Leland Faber
- Contributors
- Lloyd V. Smith (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Mechanical and Materials Engineering, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525197301842
- Language
- English
- Resource Type
- Thesis