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Interface mechanical problems in heterogeneous materials

Paggi, Marco Interface mechanical problems in heterogeneous materials. PhD Thesis thesis, Politecnico di Torino. (2005)

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The simplified assumption of material homogeneity underlying many problems of structural mechanics is very often far from the complex reality we have to cope with. Junctions and interfaces between di®erent materials must typically sustain mechanical and thermo-elastic stresses without failure. Consequently, they exert an important and sometimes controlling influence on the overall performance of the material. Therefore, current attempts in materials engineering to increase the strength and ductility of materials require a full appreciation of material interfaces, their properties and characterization. Since interface problems are one of the main concern in civil, mechanical and electronic engineering, as well as in biomechanics and in materials science, this research field is characterized by multidisciplinary aspects. New concepts in engineering the material microstructure mark the beginning of a paradigm shift in the way we think about materials and structures. Due to recent advances in material processing, material and structural design considerations are moving toward a full integration. With this respect, it is evident that a proper modeling of the mechanical behavior of interfaces at di®erent length scales is an outstanding point. The possibility of controlling the mechanical behavior of the material over all the scales by tailoring interfaces clearly emerges as one of the new challenges of the scientific community. This thesis aims at giving a reasonably complete overview of the most relevant mathematical and numerical techniques that can be applied to solve interface mechanical problems in heterogeneous materials. With this objective in mind, the connections between the wide literature of Linear Elastic and nonlinear Fracture Mechanics and Contact Mechanics are deeply investigated and emphasized. Novel features of this work include: (1) theoretical and numerical characterization of stress-singularities arising at multi-material interfaces in 2D linear elastic problems; (2) numerical and experimental study of brittle and fatigue crack growth in multi-layered materials; (3) definition of a unified interface constitutive law for the study of decohesion and contact problems at bi-material interfaces; and (4) interpretation of size-scale e®ects in new advanced composite materials, such as the prediction of the critical grain sizes for the activation of the superplastic behavior in fine grained composites and for the inversion of the Hall-Petch relationship at the nano-scale.

Item Type: Thesis (PhD Thesis)
Subjects: T Technology > TJ Mechanical engineering and machinery
Research Area: Computer Science and Applications
Depositing User: Prof Marco Paggi
Date Deposited: 25 Nov 2013 09:57
Last Modified: 09 Oct 2014 09:20
URI: http://eprints.imtlucca.it/id/eprint/1935

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