Failure process analysis of cement under explosive loading with a generalized driven nonlinear threshold model

The microstructural heterogeneity and stress fluctuation play important roles in the failure process of brittle materials. In this paper, a generalized driven nonlinear threshold model with stress fluctuation is presented to study the effects of microstructural heterogeneity on continuum damage evolution. As an illustration, the failure process of cement material under explosive loading is analyzed using the model. The result agrees well with the experimental one, which proves the efficiency of the model.

"Future fit your catalog" Panel [Presentation]:World Cat Local Implementation as part of a Consortia of Libraries within the University System of Maryland and Affiliated Institutitons

Power Point from Panel presentation giving implementation and search result displays and linking (17 slides)

Long-Term Evolution Of Delayed Ettringite And Gypsum In Portland Cement Mortars Under Sulfate Erosion

The magnitude evolution of ettringite and gypsum in hydrated Portland cement mortars due to sulfate attack was detected by X-ray powder diffraction. The influences of sulfate concentration and water-to-cement ratio on the evolution of ettringite and gypsum were investigated. Experimental results show that the magnitude of ettringite formation in sodium sulfate solution follows a three-stage process, namely, the 'penetration period', 'enhance period of strength', and 'macro-crack period'. The cracking of concrete materials is mainly attributed to the effect of ettringite. The gypsum formations occurred in two stages, the 'latent period' and the 'accelerated period'. The gypsum formation including ettringite formation was relative to the linear expansion of mortars to some extend. Both water-to-cement ratio and sulfate concentration play important roles in the evolution of ettringite and gypsum. (C) 2008 Elsevier Ltd. All rights reserved.

A simple method to simulate shrinkage-induced cracking in cement-based composites by lattice-type modeling

A new numerical procedure is proposed to investigate cracking behaviors induced by mismatch between the matrix phase and aggregates due to matrix shrinkage in cement-based composites. This kind of failure processes is simplified in this investigation as a purely spontaneous mechanical problem, therefore, one main difficulty during simulating the phenomenon lies that no explicit external load serves as the drive to propel development of this physical process. As a result, it is different from classical mechanical problems and seems hard to be solved by using directly the classical finite element method (FEM), a typical kind of "load -> medium -> response" procedures. As a solution, the actual mismatch deformation field is decomposed into two virtual fields, both of which can be obtained by the classical FEM. Then the actual response is obtained by adding together the two virtual displacement fields based on the principle of superposition. Then, critical elements are detected successively by the event-by-event technique. The micro-structure of composites is implemented by employing the generalized beam (GB) lattice model. Numerical examples are given to show the effectiveness of the method, and detailed discussions are conducted on influences of material properties.

Atomistic simulation studies of the cement paste components

230 p.

Desarrollo de componentes para el panel de administración de GeoServicios® on-line

Panel de Administración que ofrece una solución completa a la hora de realizar visores para mapas y que permite al cliente configurar un visor en base a sus necesidades, mediante diferentes módulos. Dicho panel, se ha realizado utilizando un desarrollo basado en el prototipado. En el caso de este proyecto, se especifica el desarrollo de los dos primeros prototipos. Los módulos desarrollados son los siguientes: Panel de login: Este panel permite el acceso a la aplicación. Módulo de usuarios/grupos: Este componente permite gestionar grupos y usuarios, tanto la creación, edición de los mismos como la visualización de estos. Módulo de datos: Este componente permite gestionar las fuentes de datos del cliente. Crear plantillas a partir de datos procedentes de BBDD propias, así como la edición de dichas plantillas. Módulo GeoAsset: Este componente permite configurar aplicaciones web o visores. Un visor tendrá asociado un mapa, una lista de control de accesos, etc. Siguiendo la estructura de módulos, también es objeto del proyecto la realización de un segundo prototipo que contiene la mejora de uno de los módulos ya creados: Mejora de módulo de datos: Este componente implementa además de las funcionalidades creadas en la anterior versión, una funcionalidad para permitir la subida de datos a la aplicación.