Thesis
Dynamic characterization of rigid polyurethane foam used in FEA softball simulations
Washington State University
Master of Science (MS), Washington State University
2012
Handle:
https://hdl.handle.net/2376/103176
Abstract
Numerical simulation of sport ball impacts is challenging due to the varied contact conditions involved and the difficulty in characterizing nonlinear materials at high strain rates. The following considers rigid polyurethane (PU) foam used in softballs. Past works have shown that load displacement curves from viscoelastic material models do not completely agree with experiment, suggesting incorrect mechanisms of compressive deformation. Additionally, dynamic testing using a pressure bar apparatus was unable to achieve strain rates low enough and dynamic mechanical analysis was unable to achieve strain magnitudes large enough to represent play conditions. A method was developed to impact PU foam samples over a range of displacement rates and magnitudes representative of play conditions. A single, rate-independent master curve describing the stress-strain loading response was experimentally developed and implemented into LS-DYNA's Mat #57 foam material model. Five constant-rate loading curves were also derived experimentally and incorporated into a second foam material with rate-dependent formulation (Mat #83). Comparison of experimental and numerical load-displacement curves produced agreeable results for both materials. Lack of temporal formulation for Mat #57 resulted in low rebounding rate dependence while Mat #83 showed penetration between contacting surfaces which led to nonlinear rebounding trends. Both foam material models were implemented into a simulated softball which impacted flat and cylindrical surfaces at speeds between 60 and 120 mph. Mat #57 showed excellent correlation with both the shape and magnitude of experimental load-displacement curves, predicting softball deformation mechanisms better than previous linear-viscoelastic models both as a function of speed and surface geometry. Mat #83 characterized rebound behavior on both flat and cylindrical impact surfaces within 2% of experiment, which was better than any comparable model.
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Details
- Title
- Dynamic characterization of rigid polyurethane foam used in FEA softball simulations
- Creators
- Scott D. Burbank
- 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
- 99900525148701842
- Language
- English
- Resource Type
- Thesis