Thesis
Experimental and numerical characterization of softballs
Washington State University
Master of Science (MS), Washington State University
2004
Handle:
https://hdl.handle.net/2376/280
Abstract
The performance of baseball and softball bats can depend strongly on the properties of the ball. Ball hardness is measured in a quasi-static compression test and the coefficient of restitution (COR) is measured by impacting the ball at 60 mph against a rigid flat plate. There is concern that these current methods of measuring softball performance are not adequate. The ball COR and dynamic compression were measured as a function of speed, geometry, degradation, and environmental conditions. A dynamic compression test, where the ball impacts a rigidly mounted load cell, was used to compare static and dynamic compression. A cylindrical impact surface was observed to decrease the COR and dynamic compression, but increase the contact time. The frequency of ball testing was observed to affect the ball’s measured response. Humidity was observed to have a negligible effect on a ball’s COR and dynamic hardness, but a measurable effect on its static hardness. Removing the cover of the softball increased the COR and decreased the dynamic compression. The validity of normalizing bat performance to account for differences in the softball was investigated. It was found that the current method of normalizing for the COR may not be valid, while normalizing for ball mass appeared to work very well. Increasing ball hardness was observed to increase bat performance, especially for high performing bats whose barrel stiffness is low. Two viscoelastic material models of the softball were investigated using the dynamic finite element code LS-Dyna. A three parameter Power law model was found to be in good agreement with experimental results. A parameter study was undertaken to determine how the parameters of the Power Law model affected the COR dynamic compression. The relaxation curve of the polyurethane foam core of the softball was experimentally determined using dynamic mechanical analysis (DMA). A Prony series model was used to fit the relaxation curve, but the numerical results were in poor agreement with experimental data.
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Details
- Title
- Experimental and numerical characterization of softballs
- Creators
- Joseph Gerald Duris
- 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, Washington] :
- Identifiers
- 99900525123601842
- Language
- English
- Resource Type
- Thesis