Textile Reinforced Concrete Part I: Process Model for Collaborative Research and Development

The goal of the collaborative research center (SFB 532) >Textile reinforced concrete (TRC): the basis for the development of a new material technology< installed in 1998 at the Aachen University is a complex assessment of mechanical, chemical, economical and productional aspects in an interdisciplinary environment. The research project involves 10 institutes performing parallel research in 17 projects. The coordination of such a research process requires effective software support for information sharing in form of data exchange, data analysis and data archival. Furthermore, the processes of experiment planning and design, modification of material compositions and design parameters and development of new material models in such an environment call for systematic coordination applying the concepts of operational research. Flexible organization of the data coming from several sources is a crucial premise for a transparent accumulation of knowledge and, thus, for a successful research in a long run. The technical information system (TRC-TIS) developed in the SFB 532 has been implemented as a database-powered web server with a transparent definition of the product and process model. It serves as an intranet server with access domains devoted to the involved research groups. At the same time, it allows the presentation of selected results just by granting a data object an access from the public area of the server via internet

К анализу торцового трещинообразования при сушке древесины сосны

В статье рассмотрена причина появления трещин усушки и показана необходимость их контроля с учетом влияния на качество сушки пиломатериала. Приведены данные по контролю торцовых трещин, выходящих на боковые поверхности, и расчетным путем определены скорости изменения температурного поля пиломатериала в момент начала интенсивного трещинообразования. В результате получено, что в первом периоде сушки, характеризующемся интенсивным изменением температурного поля, в древесине сосны появляются только мелкие торцовые трещины, не выходящие на поверхность пиломатериала. Во втором периоде сушки - периоде постоянной скорости, характеризующемся интенсивным испарением влаги, появляются развитые торцовые трещины, выходящие на боковые поверхности и дающие большой процент брака

Effect of twist, fineness, loading rate and length on tensile behavior of multifilament yarn

The idea underlying the present study was to apply twisting in order to introduce different levels of transverse pressure. The modified structure affected both the bonding level and the evolution of the damage in the yarn. In order to isolate this effect in a broader context, additional parameters were included in the experiment design, namely effects of loading rate, specimen length and filament diameter (directly linked to the fineness of the yarn). These factors have been studied in various contexts by several authors. Some related studies on involved factors will be briefly reviewed

Textile Reinforced Concrete Part II: Multi-Level Modeling Concept

The development of a consistent material model for textile reinforced concrete requires the formulation and calibration of several sub-models on different resolution scales. Each of these models represents the material structure at the corresponding scale. While the models at the micro-level are able to capture the fundamental failure and damage mechanisms of the material components (e.g. filament rupture and debonding from the matrix) their computational costs limit their application to the small size representative unit cells of the material structure. On the other hand, the macro-level models provide a sufficient performance at the expense of limited range of applicability. Due to the complex structuring of the textile reinforced concrete at several levels (filament - yarn - textile - matrix) it is a non-trivial task to develop a multiscale model from scratch. It is rather more effective to develop a set of conceptually related sub-models for each structural level covering the selected phenomena of the material behavior. The homogenized effective material properties obtained at the lower level may be verified and validated using experiments and models at the higher level(s). In this paper the development of a consistent material model for textile reinforced concrete is presented. Load carrying and failure mechanisms at the micro, meso and macro scales are described and models with the focus on the specified scales are introduced. The models currently being developed in the framework of the collaborative research center are classified and evaluated with respect to the failure mechanisms being captured. The micromechanical modeling of the yarn and bonding behavior is discussed in detail and the correspondence with the experiments focused on the selected failure and interaction mechanisms is shown. The example of modeling the bond layer demonstrates the application of the presented strategy

Experimental and Numerical Analysis of Spalling Effect in TRC Specimens

The paper presents the study of spalling effect occurring under tensile loading in thin-walled TRC specimens. The experimentally observed failure patterns are first classified and the performed experiment design is explained and discussed. A parameter study of spalling effect with varied thickness of concrete cover and reinforcement configurations including both the textile fabrics and the yarns provided the basis for numerical analysis of the effect. The applied numerical model was designed in order to capture the initiation and propagation of longitudinal cracks leading to the separation of concrete blocks from the textile fabrics. A meso-scopic material resolution in a single crack bridge is used for the simulation exploiting the periodic structure of the crack bridges both in the lateral and in the longitudinal direction of the TRC specimens. The matrix was modeled using an anisotropic damage model falling in the microplane-category of material models. The bond between yarn and matrix follows a non-linear bond-law calibrated using pull-out tests. The epoxy-impregnated reinforcement is considered as a homogeneous bar

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements