Size-Scale Effects in the Failure Mechanisms of Materials and Structures

Two different types of experimental methods have beeen developed for measuring lateral interaction forces between two solid surfaces for nano- and micro-meter scale contacts. One is the type of direct measurement methods which typically utilize AFM instrumentations. In the direct lateral force measurements some size-scale effects are commonly observed due to the effects of adhesion and surface roughness. A recent development of a fine AFM lateral force calibration method, a diamagnetic lateral force calibrator, has made it possible to study such size-scale effects systematically. The other type is the field projection method which requires a high resolution measurement of a deformation field near the edge of a contact. For such measurements a comprehensive map of deformation measurement techniques is introduced in a domain of spatial and strain resolutions. This technique provides a way of assessing the non-uniform distribution of the surface interaction forces for nano and micro-meter scale contacts.

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Seismic Analysis of Concrete Gravity Dams: Nonlinear Fracture Mechanics Models and Size-Scale Effects

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.82.374 ◽

2011 ◽

Vol 82 ◽

pp. 374-379 ◽

Cited By ~ 2

Author(s):

Marco Paggi ◽

Giuseppe Ferro ◽

Franco Braga

Keyword(s):

Crack Propagation ◽

Seismic Analysis ◽

Scale Effects ◽

Constitutive Law ◽

Dam Failure ◽

Gravity Dams ◽

Dam Foundation ◽

Size Scale ◽

Concrete Gravity Dams ◽

Nonlinear Dynamic Problem

The phenomenon of interface crack propagation in concrete gravity dams underseismic loading is herein addressed. This problem is particularly important from the engineeringpoint of view. In fact, besides Mixed-Mode crack growth in concrete, dam failure is oftenthe result of crack propagation along the rock-concrete interface at the dam foundation. Toanalyze such a problem, the generalized interface constitutive law recently proposed by the¯rst author is used to proper modelling the phenomenon of crack closing and reopening at theinterface. A damage variable is also introduced in the cohesive zone formulation in order topredict crack propagation under repeated loadings. Special attention is given to the complexityresulting from the solution of the nonlinear dynamic problem and to the choice of the interfaceconstitutive parameters, taking into account the important size-scale e®ects observed in thesecyclopic structures. Numerical examples will show the capabilities of the proposed approachwhen applied to concrete gravity dams.

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