Effective strain in composites as well as potential rupture and debonding of composite materials play a crucial role in predicting the strength of retrofitted reinforced concrete (RC) beams.However, only limited experimental data on these phenomena is available, mainly due to the inadequacy of traditional monitoring systems. This paper presents a comparative analysis of different instrumentation for monitoring retrofitted RC elements. In particular, the paper addresses beams retrofitted with composite materials (FRP and FRCM) and considers strain gauges (SG), fibre-optic Bragg grating (FBG) sensors, linear variable differential transformer (LVDT), digital image correlation (DIC) and acoustic emission (AE) sensors for monitoring strain, displacement, cracking and debonding. Experiments on six beams were carried out and the measured data from the monitoring devices was compared. The accuracy of DIC for strain and displacement monitoring, as well as the ability of using AE for detecting cracks and debonding, were shown to match the performance of traditional methods, with the added benefit of providing full-field and depth monitoring. This is of particular interest for compositestrengthened concrete elements in which the accurate measurements of effective strain and debonding of the composite material can lead to developing more precise design formulae.
a 3D Optical Metrology (3DOM) unit, Bruno Kessler Foundation (FBK), ABSTRACTThis paper aims to provide a procedure for improving automated 3D reconstruction methods via vision metrology. The 3D reconstruction problem is generally addressed using two different approaches. On the one hand, vision metrology (VM) systems try to accurately derive 3D coordinates of few sparse object points for industrial measurement and inspection applications; on the other, recent dense image matching (DIM) algorithms are designed to produce dense point clouds for surface representations and analyses. This paper strives to demonstrate a step towards narrowing the gap between traditional VM and DIM approaches. Efforts are therefore intended to (i) test the metric performance of the automated photogrammetric 3D reconstruction procedure, (ii) enhance the accuracy of the final results and (iii) obtain statistical indicators of the quality achieved in the orientation step. VM tools are exploited to integrate their main functionalities (centroid measurement, photogrammetric network adjustment, precision assessment, etc.) into the pipeline of 3D dense reconstruction. Finally, geometric analyses and accuracy evaluations are performed on the raw output of the matching (i.e. the point clouds) by adopting a metrological approach. The latter is based on the use of known geometric shapes and quality parameters derived from VDI/VDE guidelines. Tests are carried out by imaging the calibrated Portable Metric Test Object, designed and built at University College London (UCL), UK. It allows assessment of the performance of the image orientation and matching procedures within a typical industrial scenario, characterised by poor texture and known 3D/2D shapes.
An opportunity is offered by porous structures as implants in medical applications and arthroplasties because their mechanical and physical properties can be tuned to match patient-specific needs. For ex vivo research, there is merit in using 3D models instead of 2D layers in tissue engineering to recapitulate cell growth in microenvironments that are similar to native tissue, because this narrows the gulf between in vitro tests and clinical translation. [1] Titanium and its alloys have been researched extensively because of their biocompatibility, high strength, low wear, and corrosion resistance (due to the passivating oxide layer spontaneously formed on the surface [2] ). When embodied as porous structures, they offer mechanical properties that can match those of cortical and trabecular bone, [3] avoiding stress shielding and biomechanical failure. Porous scaffolds must be conducive to osseointegration by means of providing channels and interconnected pores for nutrient distribution, [4] networks for cellular proliferation, differentiation and maturation, and ultimately for bone healing. [5] Much work has explored different pore architectures and sizes and routes by which they can be physically realized. Advances in computer-aided design (CAD), multiphysics modeling, [6] and additive manufacturing (AM) technology have allowed the definition of a design space to digitally test manufacturability boundaries for porous structures with the desired physical, mechanical, and permeability properties that can enhance biological behavior. [7] Techniques such as selective laser melting (SLM) or electron beam melting (EBM) have been demonstrated as practical processing routes to achieve both parametric and nonparametric designs, ordered or random, using metals. With regard to parametric designs, triply periodic minimal surface (TPMS) structures [8] have received attention in recent years as AM managed to realize the manufacture of these topologies that offer mechanical superiority due to a uniformly distributed load transfer, free of discontinuities and self-intersecting elements, and
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