1,721,059 research outputs found
Application of Pulsed Thermography and Post-processing Techniques for CFRP Industrial Components
No full textSeveral studies demonstrate the effectiveness of pulsed thermography for detection and visualization of sub-superficial flaws in composites. Continuous improvement of thermal data manipulation makes active thermography an attractive and powerful inspection method for industrial process control and maintenance aims. Therefore, temperature image-processing is the major ongoing challenge in the thermographic research field. However, the particular interest for thermographic inspections is to be more addressed to its simple and relatively fast industrial application; an appropriate image processing tool should be implemented and verified on industrial components, containing manufacturing and in-service defects. In the proposed research, well-established and previously proposed methods were analysed and compared for different defect typology inside three CFRP components. The main goal is not solely focused on establishing the suitable data processing approach, providing detection limits of processed data in terms of damage type, size and distribution. The aim of proposed work is to present detailed examples of thermal imaging methods applied on similar critical defects, evaluating different results among methods in terms of defects mapping capabilities and Tanimoto evaluation criterion, coupled also with the signal-to-noise ratio as assessment of defect detectability
Comparative Analysis of Thermal Processing Approaches for a CFRP Element Aided by UT Control
No full textThe present work resumes thermal data processing with most common algorithms in literature and introduces in addition a different data processing strategy, proposed to improve subsurface defect detection on industrial composites. These materials are successfully controlled with infrared Non-Destructive Investigations, since defects are easily detected by temperature response under thermal pulses with reliable results. To reduce application limits for non-destructive inspections, the proposed research shows possibility to combine pulsed thermographic technique with accurate image-processing methods implemented in Matlab environment for a reliable and rapid characterization of subsurface and internal damage. Thermal processing methods are evaluated for the proposed case of study, as the well-established DAC, PCT, TSR procedures. In addition, the authors proposed a better defect characterization that is achieved with refined data processing and accurate experimental procedures, providing detailed contrast maps where defects are easily distinguished. This improved algorithm automates the defect mapping and enhances the accuracy of defects inspection, optimized to identify defect boundaries according to spatial variations in neighboring of each calculation point of the whole thermal frame. Thermal data are evaluated with standard methods and the local boundary method is for carbon-fiber composite specimens with artificial defects, evaluating processed images obtained by different methods employing the Tanimoto criterion. Proposed thermal computation method is found suitable for automatic mapping of defect distribution and optimized for simultaneous defect boundaries’ detection in terms of Tanimoto criterion, in the inspected structure. In addition, ultrasonic controls are carried out for detection comparison between different control procedures
Microstructural analysis of AISI 304 bars welded with high speed pulsed discharges
No full textIn a way similar to the resistance welding the high speed pulsed welding exploits the power of elevated discharging current through an electrical circuit, which contains the two parts to be welded. During welding edges profile interact with the process parameters to determine both the weld microstructure and mechanical strength.
In this paper, the welding profiles at the opposite surfaces was machined so to have linear contacts instead of a classic single protrusion contact. The effect of this multilinears contact geometry was a weld that was in the midway between the capacitor discharge welding (CDW) and the projection welding (PW).
Pulsed welding experiments were performed using AISI 304 cylindrical bars in butt configuration. The welded microstructures were studied using an optical microscope and image analysis software. The Vickers microhardness tests were performed to a better characterization of the welding microstructure
COPERTURE IN RAME: INNOVATIVO SISTEMA DI SUPERFICIE CAPTANTE
No full textNegli ultimi anni sia l’avvento di nuove tecnologie costruttive ed impiantistiche che la progressiva
affermazione di materiali ecocompatibili hanno determinato evidenti trasformazioni anche nei
sistemi di copertura, influenzando spesso lo skyline urbano-territoriale e modificando l’insieme
dei requisiti prestazionali cui una copertura deve soddisfare.
Lo scopo del lavoro risiede nella definizione di un innovativo sistema per la realizzazione di un
manto di copertura in laminato metallico, in grado di soddisfare contemporaneamente esigenze
architettonico-formali, necessità tecnico-prestazionali ed attenzione ai temi di sostenibilità ed
impiego di energie rinnovabili.
L’esperienza progettuale ha così determinato, dal punto di vista tecnico, la messa a punto di un
sistema di copertura in profili di rame in grado di produrre acqua calda sanitaria, verificandone la
sostenibilità, dal punto di vista energetico-ambientale.
Per valutare l’efficacia del sistema ed ottenere parametri indicativi di progettazione dell’impianto,
è stato realizzato un campione di copertura orientato a Sud-Sud-est a L’Aquila. La copertura, realizzata
in lastre di rame 6/10 e dotata di un sistema di tubi in rame sottomanto, sfrutta le proprietà
di uno speciale formulato liquido termovettore di captare il calore solare. Il sistema è stato
monitorato nell’anno solare 2004, producendo risultati confrontabili (se non superiori) a quelli dei
pannelli solari presenti sul mercato.
L’applicazione progettuale di tale sistema è, poi, scaturita da una prima fase di ricerca in tre ambiti
distinti:
ricerca di carattere storico-informativo circa l’impiego dei laminati metallici in copertura, valutandone
le influenze architettonico-formali sugli edifici;
indagine delle proprietà del rame come materiale impiegato in edilizia
analisi dei vari sistemi di sfruttamento delle energie rinnovabili e relative caratteristiche, nonché
dei materiali edili ecocompatibili.
Nella seconda fase di progettazione è stato impiegato il software ECOTEC ed in particolare l’applicativo
WEATHER TOOL per studiare le migliori condizioni di esposizione per il posizionamento
della copertura, nota la località.
I vari contributi hanno portato alla definizione di una copertura con una sua caratterizzazione
architettonica, realizzata in materiale sostenibile ed in grado di sfruttare l’energia solare per la
produzione di acqua calda sanitaria.
Keywords
Coperture, energia, rame, acqua sanitari
Fatigue and damage analysis on aeronautical CFRP elements under tension and bending loads: Two cases of study
No full textThe present work is focused on experimental monitoring procedures to investigate stresses and damage settlement during fatigue tests of CFRP elements under bending and tensile loads. Continuous damage accumulation, coupled with mechanical properties degradation are monitored with ultrasonic inspection and with thermographic full field analysis, during long lasting HC fatigue loads. Effects of localized bending loads and artificial composite wrinkle presence within a notch are source of delamination initiation, investigated two different types of specimens under fatigue. Combined monitoring approaches, based on thermo-elastic and dissipative phenomena, together with ultrasonic through thickness properties variations are claimed to offer precise damage state and localization during tests, subsequently aided by FEM damage model analysis in case of static failure zone identification, to be compared with experimental data; in addition, experimental DIC computation of deformation on specimen critical zones is performed in order to check failure and delamination initiation spot. The thermal parameters and experimental compliance correlation seem to indicate a similar signal variation during damage progress, verified also by contemporaneous ultrasonic inspections of some specimens in the failure zones of CFRP elements
A Brief Review and Advances of Thermographic Image - Processing Methods for IRT Inspection: a Case of Study on GFRP Plate
No full textThe present work introduces a different data processing strategy, proposed in order to improve sub-surface defect detection on industrial composites; in addition, a resume of thermal data processing with most common algorithms in literature is presented and applied with new data. A deep comparison between the common absolute contrast, DAC, PCT, TSR and derivative methods and a new proposed contrast mapping procedure is implemented. Thermographic inspection was done in reflection mode on a Glass Fiber Reinforced Plastic plate, with flat bottom hole defects. Thermal data computation method is found to be critical for simultaneous defect detection and automatic mapping, optimized to identify defect boundaries at specific depth, with help of accurate image processing, implemented in a Matlab GUI for a reliable and rapid characterization of internal damage. The new processing approach, the Local Boundary Contrast method, elaborates different contrast maps and facilitates recognition of damage extension. Tanimoto criterion and the signal-to-noise ratio method were applied as a criterion to assess defect detectability of various processing methods
Stress/strain state for critical components of a jet engine aeronautical compressor
No full textIn order to prevent in-flight fatigue failure, a numerical analysis of in service-operative cases is an useful approach for preliminary evaluation of most stressed and critical zones in components of aeronautical engine. The zero-stage compressor rotor disk and blades represent one of the most critical part of aircraft turbojet. This paper presents a verification FEM analysis of this component. An accurate 3D scanning was performed to reconstruct both blade and disk real geometry and the detailed point cloud was obtained and opportunely elaborated by using specific software to generate CAD sections and volumes given in input to finite element analysis. The stress field due to different operating conditions is studied for a suitable evaluation of the most stressed and critical areas where a failure may occur, particularly near the rotor connection under contact conditions. FEM and flight data analysis are finally used for a subsequent fatigue life verification, based on classical Palmgren Miner’ rule. The suggested procedure for verification of engine aeronautical component is here optimized for maintenance program improvements
What does Brexit mean for UK cultural and creative cities?
No full textCultural and creative sectors (CCS) are increasingly recognized as a driving economic force. In addition to their undisputed soft power, creative jobs are expected to prove more resilient to automation, and may therefore play an important role in the future growth cycles of advanced global economies. But how is Brexit going to affect the UK’s flourishing creative economy at an urban level? Pre-Brexit evidence from the European Commission’s Cultural and Creative Cities Monitor (CCCM) clearly shows that UK cultural and creative cities excel in Europe in their capacity to attract and integrate foreign creative professionals. Creative non-nationals represent a diverse, crucial human capital pool for CCS, as 22% of CCS employers hire at least one non-UK worker. The effect of Brexit on the cultural and creative potential of UK cities can be devastating for CCS competitiveness if not properly addressed. As CCSs are widely regarded as leading sectors of the UK economy and major drivers of innovation and growth in the UK’s long-term developmental vision, suitable policy measures should be taken to prevent this possibility
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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