30 research outputs found

    Analysis and modelling of mechanical anchorage of 4D/5D hooked end steel fibres

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    This paper represents an analytical model to predict the influence of the fibre geometry on the pull-out behaviour of various geometrical hooked end steel fibres. The model is established based on the concept of a frictional pulley along with two, three and four plastic hinges to simulate the mechanical anchorage effect provided by the hook. The mechanical contribution of the hook is a function of the cold work needed to straighten the fibre during the pull-out. The input parameters used in this model are directly related to geometrical and mechanical properties of each fibre. Model predictions are validated against experimental results for single fibre pull-out tests, and very good agreement is shown.The first author gratefully acknowledges the financial support of the Ministry of Higher Education and Scientific Research of Iraqi Government for this Ph.D. projec

    On the effects of friction modelling on small punch creep test responses: a numerical investigation

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    This paper shows the results of finite element (FE) analyses of Small Punch Creep Testing (SPCT) of a P91 steel at 600°C using two different approaches to model the friction between the specimen and the punch. The numerical results obtained by using the “classical” Coulomb friction model (i.e. constant friction coefficient) have been compared with those obtained by a more modern formulation, which takes into account the effects of local loading conditions, i.e. the contact pressure, between the contacting bodies (the small disc specimen and the punch) on the coefficient of friction. The aim of the work is to investigate the effects of the friction formulation used for the calculations on the numerical results representing the output of the test, i.e. the variation of the punch displacement versus time and the time to rupture. The calculations, carried out for various load levels, showed that the friction coefficient is not constant at all positions on the contacting surface between the punch and the specimen during the deformation process. The maximum value for the coefficient of friction is reached at the contact edge, which is a very important region in the specimen, because this is the position at which most of the creep deformation occurs. As expected, the displacement versus time curve (that is usually the only output obtained from experimental SPCTs) is affected by friction formulation which is used, as this directly influences the stress and strain fields in the specimen

    Wireless Sensors for Intraoral Force Monitoring

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    A device for wireless intraoral forces monitoring is presented. Miniaturized strain gauge sensors are used for the measurements of forces applied by tongue and lips. A sensor interface IC is able to multiplex among four sensors and a low energy transmission module, equipped with an ARM Cortex–M0 core, is used for signal elaboration and remote wireless data transmission using Bluetooth® Low Energy standard protocol. The main novelty rely in the dynamic correction of the output corrupted by the prestrain issue. Moreover, the device shows a reduced dimension and the ability to transmit data wirelessly, without the use of external cables normally used in state-of-the-art intraoral monitoring devices

    Mechanical Loading

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