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Exploration of Cosserat Elastic Structures with Novel Characteristics via Experimental Micromechanics
Başlık:
Exploration of Cosserat Elastic Structures with Novel Characteristics via Experimental Micromechanics
Yazar:
Rueger, Zachariah D., author.
ISBN:
9780438082175
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (170 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-11(E), Section: B.
Advisors: Roderic S. Lakes Committee members: Susan Babcock; Melih Eriten; Don Stone; Xudong Wang.
Özet:
The currently accepted classical theory of elasticity is limited when describing many materials by its two elastic constants. Another theory of elasticity, the Cosserat theory, incorporates rotation of points and distributed moments (couple stresses) in addition to the translation of points and force stress present in classical elasticity. Consequently, the Cosserat theory has more freedom and offers a richer framework to describe materials than the classical theory - it contains six elastic constants. Understanding materials by the more descriptive capabilities of the Cosserat theory will facilitate a novel approach to material design - optimization of the six Cosserat elastic constants. Additionally, Cosserat elasticity predicts several key phenomena to differ from classical predictions. One such phenomenon is the Cosserat prediction of a size effect in the torsion and bending of circular cylinders of Cosserat elastic materials - specimens are more rigid than expected classically.
In this document, a variety of materials are systematically analyzed using the framework of Cosserat elasticity via experimentation. The size effects demonstrated by the following materials are explored, the Cosserat elastic constants extracted, and the mechanisms by which deformation is controlled are probed and related to Cosserat phenomena. First, open cell polyurethane foams of two cell sizes are explored as Cosserat continua. Next, specimens of the large cell foam, triaxially compressed under heat to achieve a negative Poisson's ratio, are studied. Unidirectional composites composed of corrugated nylon tubing segments and silicone rubber cement are engineered and demonstrate extremely large size effects in torsion. Approximate solutions for bending and torsion of Cosserat elastic materials with square cross sections are used to probe Cosserat behavior of designed negative Poisson's ratio tetragonal lattices. Conclusions drawn from studies up to this point are employed to engineer triangular prismatic unit cell lattices demonstrating Cosserat elastic effects including large magnitude size effects in torsion and bending. The lattices made of triangular prismatic unit cells incorporating strain gradient sensitive rib elements are engineered and experimentally analyzed as Cosserat material. Finally, the systematic design and experimentation process leading to the development of triangular prismatic unit cell lattices demonstrating large size effects is covered in detail.
Notlar:
School code: 0262
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(695248.1) | 695248-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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