Thesis
Impact response of polyurethane
Washington State University
Master of Science (MS), Washington State University
2009
Handle:
https://hdl.handle.net/2376/102386
Abstract
The properties of polyurethane, the primary component of softballs, have been found to be rate sensitive. The impact response of softballs containing different rebound properties and stiffnesses were desired. Samples from five different softball models were tested at high and low strain rates. To test the polyurethane at high strain rates a split Hopkinson pressure bar with aluminum bars was designed and constructed. For comparison the polyurethane materials were also measured at low strain rates of 0.3 s-1 on a universal testing machine. An elastic modulus was measured during both the high strain rate and low strain rate tests. A viscoelastic model, obtained from numeric simulations, was compare to the measured high strain rate properties of the polyurethane. It was found that during impact a softball experiences a peak strain rate of 2500 s1 and strain magnitude of 0.2 strain. The average strain rate in the pressure bar tests was 2780 s-1 . The stress measured at 0.2 strain increased 42% when the strain rate increased from 0.3 s-1 to 2780 s-1 . On average the modulus was 33% high at 2780 s-1 compared to 0.3 s-1 .The average modulus increase from the increase in strain rate was 33%. The viscoelastic model predicted stresses three times higher than the stresses observed during the high strain rate tests. Softballs with different stiffness and rebound properties were compared. The stress and modulus increased with ball stiffness in both the high strain rate and low strain rate tests. Hysteresis in the load-displacement response from the 0.3 s-1 tests was not sensitive to the measured ball COR. This suggests that rate effects are important to correctly characterize the ball.
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Details
- Title
- Impact response of polyurethane
- Creators
- John Andrew Bryson
- 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
- 99900525039301842
- Language
- English
- Resource Type
- Thesis