Damage Mechanics

The earthquake of the 9th of July 1998 that hit in the central group of the Azores archipelago greatly affected the islands of Faial, Pico and São Jorge, reaching a magnitude of Mw 6.2 with the epicentre located about 15km northeast of the Faial Island. This earthquake allowed the collection of an unprecedented quantity of data concerning the characterisation of the building stock and the damage suffered by construction. This is the main purpose of this research, consisting essentially of three main aspects: (i) A detailed characterisation of the building stock, assigning a five category classification, from old traditional rubble stone masonry to reinforced concrete moment framed buildings; (ii) A detailed damage grade classification based on the different damage mechanisms observed; and, (iii) A seismic vulnerability assessment of the building stock. The results of the vulnerability assessment together with the building stock database and damage classification were integrated into a GIS tool, allowing the spatial visualation of damage scenarios, which is potentially useful for the planning of emergency response strategies and retrofitting priorities to mitigate and manage seismic risk.

Geometrical models needed for finite element discretization of plain-weave fabric-reinforced composites are developed from measurements taken on photomicrographs of single lamina and laminated composites. Then, a meso-level damage model is implemented into ANSYS as a user-defined material model for predicting the non-linear behavior of plain-weave reinforced laminates under tensile loading. The damage model is validated for the tensile response of T300/5208 laminate for four configurations, [10/−10]2s, [0/45/−45/90]s, [30/−30]2s and [45/−45]2s. Then, the damage behavior of plain-weave fabric-reinforced laminates is analyzed using the proposed damage model in the context of the finite element method. The modes of continuum damage are identified from the analysis. Comparisons with experimental data are provided in order to support validity of the proposed models.

The use of self-organizing maps and artificial neural networks for structural health monitoring is presented in this paper. The authors recently developed a nonparametric structural damage detection algorithm for extracting damage indices from the ambient vibration response of a structure. The algorithm is based on self-organizing maps with a multilayer feedforward pattern recognition neural network. After the training of the self-organizing maps, the algorithm was tested analytically under various damage scenarios based on stiffness reduction of beam members and boundary condition changes of a grid structure. The results indicated that proposed algorithm can successfully locate and quantify damage on the structure.

Для более точной оценки прочности эксплуатируемых железобетонных конструкций необходимо использовать модели с дискретным расположением арматурных стержней с учетом реальных характеристик сцепления арматуры с бетоном, определяемых, как правило, экспериментальным путем. Одним из наиболее распространенных способов определения характеристик сцепления является вытягивание арматурного стержня из бетонного блока (pull-out test). Процесс разрушения связей сцепления арматуры с бетоном при выдергивании стержня из бетонного блока представляет собой сложный многостадийный процесс, сопровождающийся присутствием неоднородного и неупругого деформирования, нарушением адгезионных связей, возникновением и развитием трещин различной формы и ориентации, наличием изменяющихся зон контакта и трибологических явлений. В рамках данной работы выполнены экспериментальные исследования и произведено сравнение с результатами расчета с использованием различных моделей разрушения связей сцепления арматуры с бетоном в задаче о вытягивании стержневой профилированной арматуры из бетонного блока. В первой части статьи рассматриваются модели с учетом несплошности соединения, во второй – модели без явного учета несплошности.
The problem of pulling the reinforcing bar from the concrete block is urgent for the practice, as it represents the most widespread method of experimental evaluation of characteristics of reinforced-concrete bond behavior, which are necessary for an estimation of the strength and durability of reinforced concrete structures. Fracture process of bonds at pulling the rebar from the concrete is a complex multistep process, accompanied by the presence of inhomogeneous and inelastic deformation, a rupture of adhesive bonds, the initiation and propagation of cracks of different shape and orientation, the presence of contact and tribological phenomena. The nonlinear finite-element solutions of the problem of pulling the reinforcing bar from the concrete block have been obtained with using various models of bond behavior and concrete cracking. The comparison of obtained numerical results with experimental data has been presented and discussed. The first part of the article is devoted to the models taking into account the discontinuity of the connection, while the second part is concerned with the models without explicitly taking into account of discontinuities.

This book is written for people who wish to learn MATLAB for the first time. The book is really designed for beginners and students. In addition, the book is suitable for students and researchers in various disciplines ranging from engineers and scientists to biologists and environmental scientists. One of the objectives of writing this book is to introduce MATLAB and its powerful and simple computational abilities to students in high schools. The material presented is very easy and simple to understand - written in a gentle manner. The topics covered in the book include arithmetic operations, variables, mathematical functions, complex numbers, vectors, matrices, programming, graphs, solving equations, and an introduction to calculus. In addition, the MATLAB Symbolic Math Toolbox is emphasized in this book. There are also over 230 exercises at the ends of chapters for students to practice. Detailed solutions to all the exercises are provided in the second half of the book.

Structural health monitoring (SHM) and vibration-based structural damage detection have been a continuous interest for civil, mechanical and aerospace engineers over the decades. Early and meticulous damage detection has always been one of the principal objectives of SHM applications. The performance of a classical damage detection system predominantly depends on the choice of the features and the classifier. While the fixed and hand-crafted features may either be a sub-optimal choice for a particular structure or fail to achieve the same level of performance on another structure, they usually require a large computation power which may hinder their usage for real-time structural damage detection. This paper presents a novel, fast and accurate structural damage detection system using 1D Convolutional Neural Networks (CNNs) that has an inherent adaptive design to fuse both feature extraction and classification blocks into a single and compact learning body. The proposed method performs vibration-based damage detection and localization of the damage in real-time. The advantage of this approach is its ability to extract optimal damage sensitive features automatically from the raw acceleration signals. Large-scale experiments conducted on a grandstand simulator revealed an outstanding performance and verified the computational efficiency of the proposed real-time damage detection method.

To achieve safety and reliability in pipelines installed in seismic and permafrost regions, it is necessary to use linepipe materials with high strength and ductility. The introduction of dual-phase steels, e.g., with a bainite and dispersed martensite–austenite (MA) constituent, would provide the necessary ingredients for the improvement of the strain capacity (as required by a new strain-based linepipe design approach) and toughness. To fine-tune the alloy design and ensure these dual-phase steels have the required mechanical properties, an understanding of the governing deformation micromechanisms is essential. For this purpose, a recently developed joint numerical–experimental approach that involves the integrated use of microscopic digital image correlation analysis, electron backscatter diffraction, and multiphysics crystal plasticity simulations with a spectral solver was employed in this study. The local strain and stress evolution and microstructure maps of representative microstructural patches were captured with a high spatial resolution using this approach. A comparison of these maps provides new insights into the deformation mechanism in dual-phase microstructures, especially regarding the influence of the bainite and MA grain size and the MA distribution on the strain localization behavior.

This review addresses possible adaptation strategies in rice production to abiotic stresses that will aggravate under climate change: heat (high temperature and humidity), drought, salinity, and submergence. Each stress is discussed regarding the current state of knowledge on damage mechanism for rice plants as well as possible developments in germplasm and crop management technologies to overcome production losses. Higher temperatures can adversely affect rice yields through two principal pathways, namely (i) high maximum temperatures that cause—in combination with high humidity—spikelet sterility and adversely affect grain quality and (ii) increased nighttime temperatures that may reduce assimilate accumulation. On the other hand, some rice cultivars are grown in extremely hot environments, so that the development of rice germplasm with improved heat resistance can capture an enormous genetic pool for this trait. Likewise, drought is a common phenomenon in many rice growing environments, and agriculture research has achieved considerable progress in terms of germplasm improvement and crop management (i.e., water saving techniques) to cope with the complexity of the drought syndrome. Rice is highly sensitive to salinity. Salinity often coincides with other stresses in rice production, namely drought in inland areas or submergence in coastal areas. Submergence tolerance of rice plants has substantially been improved by introgressing the Sub1 gene into popular rice cultivars in many Asian rice growing areas.Finally, the review comprises a comparative assessment of the rice versus other crops related to climate change. The rice crop has many unique features in terms of susceptibility and adaptation to climate change impacts due to its semiaquatic phylogenetic origin. The bulk of global rice supply originates from irrigated systems which are to some extent shielded from immediate drought effects. The buffer effect of irrigation against climate change impacts, however, will depend on nature and state of the respective irrigation system. The envisaged propagation of irrigation water saving techniques will entail benefits for the resilience of rice production systems to future droughts. We conclude that there are considerable risks for rice production stemming from climate change, but that the development of necessary adaptation options can capitalize on an enormous variety of rice production systems in very different climates and on encouraging progress in recent research.

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights a b s t r a c t This study addresses the effects of basalt fibre hybridization on quasi-static mechanical properties and low velocity impact behaviour of carbon/epoxy laminates. Interply hybrid specimens with two different stacking sequences (sandwich-like and intercalated) are tested at three different energies, namely 5, 12.5 and 25 J. Residual post-impact properties of the different configurations of carbon/basalt hybrid laminates are characterized by quasi static four point bending tests. Post-impact flexural tests and interlam-inar shear tests are used for the mechanical characterization along with two non-destructive methods, namely acoustic emission and ultrasonic phased array, in order to get further information on both the extent of damage and failure mechanisms. Results indicate that hybrid laminates with intercalated configuration (alternating sequence of basalt and carbon fabrics) have better impact energy absorption capability and enhanced damage tolerance with respect to the all-carbon laminates, while hybrid laminates with sandwich-like configuration (seven carbon fabric layers at the centre of the laminate as core and three basalt fabric layers for each side of the composite as skins) present the most favourable flexural behaviour.

We present a compendium of optocoupler radiation test data including data on neutron, proton and heavy ion displacement damage (DD), single event transients (SET) and degradation due to total ionizing dose (TID). Proton data includes ionizing and non-ionizing damage mechanisms.

In this work a novel methodology for fracture toughness characterization by means of the small punch test (SPT) is presented. Notched specimens are employed and fracture resistance is assessed through a critical value of the notch mouth displacement δ SPT. Finite element simulations and interrupted experiments are used to track the evolution of δ SPT as a function of the punch displacement. The onset of crack propagation is identified by means of a ductile damage model and the outcome is compared to the crack tip opening displacement estimated from conventional tests at crack initiation. The proposed numerical–experimental scheme is examined with two different grades of CrMoV steel and the differences in material toughness captured. Limitations and uncertainties arising from the different damage phenomena observed in the lowest toughness material examined are thoroughly discussed.