Finite strain behavior of polyurea for a wide range of strain rates
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 2010.
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| Format: | Thesis |
| Language: | eng |
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Massachusetts Institute of Technology
2010
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| Online Access: | http://hdl.handle.net/1721.1/58458 |
| _version_ | 1811086050987081728 |
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| author | Shim, JongMin, 1975- |
| author2 | Tomasz Wierzbicki and Dirk Mohr. |
| author_facet | Tomasz Wierzbicki and Dirk Mohr. Shim, JongMin, 1975- |
| author_sort | Shim, JongMin, 1975- |
| collection | MIT |
| description | Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 2010. |
| first_indexed | 2024-09-23T13:20:07Z |
| format | Thesis |
| id | mit-1721.1/58458 |
| institution | Massachusetts Institute of Technology |
| language | eng |
| last_indexed | 2024-09-23T13:20:07Z |
| publishDate | 2010 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/584582019-04-10T16:11:23Z Finite strain behavior of polyurea for a wide range of strain rates Shim, JongMin, 1975- Tomasz Wierzbicki and Dirk Mohr. Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering. Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering. Civil and Environmental Engineering. Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 2010. Cataloged from PDF version of thesis. Includes bibliographical references (p. 101-112). Polyurea is a special type of elastomer that features fast setting time as well as good chemical and fire resistance. It has also good mechanical properties such as its high toughness-to-density ratio and high strain rate-sensitivity, so its application is recently extended to structural purpose to form sandwich-type or multi-layered plates. Those structures can be used for retrofitting of military vehicles and historic buildings, absorbing energy during structural crash. In order to investigate its behavior of hysteresis as well as rate-sensitivity, three different testing systems are used to cover a wide range of strain rates up to strain of 100%. In view of impact and blast events, the virgin state of polyurea is considered throughout the experiments. First, a hydraulic universal testing machine is used to perform uniaxial compressive loading/unloading tests in order to investigate its hysteresis behavior at low strain rates (0.001/s to 10/s). Second, two distinct gas-gun split Hopkinson pressure bar [SHPB] systems are employed to cover high strain rates: a nylon bar system (700/s to 1200/s) and an aluminum bar system (2300/s to 3700/s). Lastly, the rate-sensitivity for intermediate strain rates (10/s to 1000/s) is characterized using a modified SHPB system. (cont.) The device is composed of a hydraulic piston along with nylon input and output bars. A finite strain constitutive model of polyurea is presented in order to predict the hysteresis and rate-sensitivity behavior. The 1-D rheological concept of two Maxwell elements in parallel is employed within the framework of the multiplicative decomposition of the deformation gradient. Model parameters are calibrated based on the uniaxial compressive tests at various rates. The corresponding algorithms is implemented as a user-defined material subroutine VUMAT for ABAQUS/Explicit, and used to predict the response of polyurea. The proposed constitutive model reasonably captures the experimentally observed asymmetric rate-sensitivity and stress-relaxation behavior: strong rate-sensitivity and large amount of stress relaxation during loading phase, but weak rate-sensitivity and smaller amount of stress relaxation during unloading phase. In order to validate the proposed model, various dynamic punching tests are performed, and their results are well compared with the model predictions during loading although the prediction of unloading behavior can be further improved. by Jongmin Shim. Ph.D. 2010-09-03T18:56:09Z 2010-09-03T18:56:09Z 2009 2010 Thesis http://hdl.handle.net/1721.1/58458 639539491 eng M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 112 p. application/pdf Massachusetts Institute of Technology |
| spellingShingle | Civil and Environmental Engineering. Shim, JongMin, 1975- Finite strain behavior of polyurea for a wide range of strain rates |
| title | Finite strain behavior of polyurea for a wide range of strain rates |
| title_full | Finite strain behavior of polyurea for a wide range of strain rates |
| title_fullStr | Finite strain behavior of polyurea for a wide range of strain rates |
| title_full_unstemmed | Finite strain behavior of polyurea for a wide range of strain rates |
| title_short | Finite strain behavior of polyurea for a wide range of strain rates |
| title_sort | finite strain behavior of polyurea for a wide range of strain rates |
| topic | Civil and Environmental Engineering. |
| url | http://hdl.handle.net/1721.1/58458 |
| work_keys_str_mv | AT shimjongmin1975 finitestrainbehaviorofpolyureaforawiderangeofstrainrates |