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Climent N.,University of Barcelona | Arroyo M.,University of Barcelona | Gens A.,University of Barcelona | O'Sullivan C.,South Kensington Campus
Numerical Methods in Geotechnical Engineering - Proceedings of the 8th European Conference on Numerical Methods in Geotechnical Engineering, NUMGE 2014 | Year: 2014

Sand production around a wellbore is here simulated using a three dimensional numerical model based on Discrete Element Method (DEM) coupled with Computational Fluid Dynamics (CFD). The model is calibrated against a well-known poro-elastoplastic analytical solution for the dry case, and later applied on hydrostatic conditions, at different levels of pore pressure and effective stress. The outcomes of the numerical model are examined and compared with the response predicted by the analytical solution. The microscopic asymmetry of the numerical model and the damping effect of the drag force are found to play a large role in the response. © 2014 Taylor & Francis Group. Source


Etoundi A.C.,University of Bristol | Burgess S.C.,University of Bristol | Vaidyanathan R.,South Kensington Campus
Journal of Mechanisms and Robotics | Year: 2013

This paper presents a novel condylar hinge for robotic limbs which was inspired by the human knee joint. The ligaments in the human knee joint can be modeled as an inverted parallelogram four-bar mechanism. The knee joint also has a condylar cam mechanism between the femur and tibia bones. The bio-inspired joint mimics the four-bar mechanism and the cam mechanism of the human knee joint. The bio-inspired design has the same desirable features of a human knee joint including compactness, high mechanical advantage, high strength, high stiffness and locking in the upright position. These characteristics are important for robotic limbs where there are often tight space and mass limitations. A prototype hinge joint similar in size to the human knee joint has been designed and tested. Experimental tests have shown that the new condylar hinge joint has superior performance to a pin-jointed hinge in terms of mechanical advantage and stiffness. The prototype hinge has a mechanical advantage that is greater than a pin-jointed hinge by up to 35% which leads to a corresponding reduction in the peak force of the actuator of up to 35% for a squatting movement. The paper also presents a five-step design procedure to produce a combined inverted parallelogram mechanism with a cam mechanism. © 2013 by ASME. Source


Schwankl M.,Airbus | Sharif Khodaei Z.,South Kensington Campus | Aliabadi M.H.,South Kensington Campus | Weimer C.,Airbus
Key Engineering Materials | Year: 2012

Numerical modelling of EMI for damage detection has been presented in this paper. The PZT model is validated against the published experimental result for free disk and tied to the structure. The numerical modelling of the PZT patch will result in the admittance measure of the structure. The imaginary part of the admittance measure is used for developing a self-diagnostic sensor system. The real part of the admittance measure was used to develop a damage detection algorithm. Damage detection using EMI method was successfully applied to a simple composite disk and a stiffened panel. The EMI method is suitable for short range damage detection in structural parts with limited or no access. Source


Sharif Khodaei Z.,South Kensington Campus | Ghajari M.,South Kensington Campus | Aliabadi M.H.,South Kensington Campus | Apicella A.,Alenia
Key Engineering Materials | Year: 2012

A SMART Platform is developed based on sensor readings for Structural Health Monitoring of a stiffened composite panel. The platform's main function is divided into three categories: Passive sensing, Active sensing and Optimal sensor positioning. The platform has selfdiagnostic capabilities, i.e. prior to its application the health of the sensors and their connection will be checked to avoid any false alarm. Passive sensing results in impact location and force magnitude detection. Active sensing is performed for damage detection. It results in detecting the damage location and severity. Finally the optimal sensor location can be provided given the number of sensors and probability of detection value. This platform is the first step in applying the developed SHM methodologies to real size structures in service load conditions. Source


Ghajari M.,South Kensington Campus | Khodaei Z.S.,South Kensington Campus | Aliabadi M.H.,South Kensington Campus
Key Engineering Materials | Year: 2012

In this work, a number of impacts on a composite stiffened panel fitted with piezoceramic sensors were simulated with the finite element (FE) method. During impacts, the contact force history and strains at the sensors were recorded. These data were used to train, validate and test two artificial neural networks (ANN) for the prediction of the impact position and the peak of the impact force. The performance of the network for location detection has been promising but the other network should be further improved to provide acceptable predictions about the peak force. © (2012) Trans Tech Publications. Source

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