102,084 research outputs found
The use of electrochemical noise analysis on corroding systems
No full textThis paper gives an overview of the use of Electrochemical Noise (EN) for corrosion studying and monitoring. Since the quality and reliability of noise data are affected by a number of acquisition parameters, such as sampling interval, sampling duration, D.C. trend and instrumental noise, some experimental and practical aspects were discussed. The use of statistical parameters such as standard deviation, Pit Index and/or Localization Index and Noise Resistance to analyze noise data of corroding systems were examined. Many experimental applications of Electrochemical Noise Measurements on different metals and alloys were given. EN data have been compared with traditional electrochemical techniques. EN allowed to characterize the corrosion behavior of samples giving in some cases good quantitative estimation. The transposition of current and potential noise acquisition in the frequency domain (by Fast Fourier Transform and/or Maximum Entropy Method), gave further information on corrosion mechanism and in particular permitted to identify the type of corrosion. Finally the use of Discriminant Analysis permitted to deduce the best sampling frequency and sampling duration for EN acquisition, able to discriminate between two different situations
Electrochemical noise for corrosion detection
No full textIn the last years, a growing interest on the use of Electrochemical Noise (EN) for corrosion studies may be detected in the main literature. As a result of this, several methods for analyzing noise data have been developed.
In this paper a review of the investigative possibilities offered by EN in the field of corrosion is given.
All the experimental data reported are from research projects developed in our laboratory where, for more than 15 years, EN has been applied to the solution of different corrosion problems and some dedicated software have been developed for EN data analysis (FFT-MEM, PSD slope detection, discriminant analysis). Much attention will be given to the use of statistical parameters and their significance in terms of corrosion behavior of the electrode.
Moreover, the experimental caution to use in order to have meaningful data will be highlighted
Microstructural Properties of Microporous a-Hematite ceramics Investigated by fractional factorial design
No full text
On-line corrosion resistance tests in sea water on metals for MED plants
No full textThis paper reports the results of corrosion tests performed on 254SMO and 2507SAF stainless steels and titanium, in flowing seawater at 60 degrees C. Tests were performed at Mareco CNR marine corrosion laboratory sited in Bonassola (La Spezia, Italy) for four months. The evolution of corrosion phenomena were followed by means of online simultaneous acquisition of open circuit potential (OCP), linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS) and electrochemical noise analysis (ENA). Moreover, the effect of antiscaling and biocide water treatment on corrosion behaviour of selected metals, was studied. At the end of test, samples were dismounted and inspected by visual and microscopic observation. As a general trend, a good behaviour was observed for all materials. A strong, positive effect of the water treatment was detected in particular on titanium
Discrete Damage Modelling for Computer Aided Acoustic Emissions.
No full textThis chapter is conceived as an essay on modern multiscale discrete damage modelling,
providing a brief personal perspective about its foreseeable applications-implications for
structural health monitoring purposes. In particular, it is argued that this sort of damage
modelling could be potentially useful in damage detection by acoustic emissions (AE),
which is a class of non-destructive techniques (NDT) used to capture damage evolution in a
number of materials (e.g. from concrete systems such as bridges and beam elements to
composites in aircraft components and pressure equipments) and from a number of external
actions (e.g. sustained load, monotonic testing, fatigue, corrosion, etc.) (Biancolini & Brutti,
2006 ; Carpinteri & Lacidogna, 2008 ; Grosse & Ohtsu, 2008). With AE it is possible to “hear”
the microcracking phenomenon and characterize the location and magnitude of a single
microcrack (of size and “strength”1 beyond certain thresholds) acting as an acoustic source.
Hence, it is routinely possible to plot the released energy of each crack as a time series or to
map them over a 2D spatial domain by counting and locating individual acoustic events in
time. Yet the analysis of this type of output is not straightforward and major difficulties
exist, let alone sensitivity issues of equipment, material dependence, and other practical
issues. The scope of this discussion covers two issues of general interest:
1. the randomness of the AE signal,
2. the need for structure-property relations as companion to AE monitoring
“Design, manufacture and testing of self-sensing carbon fibre-glass-fibre self-sensing polymer rods”
No full textAt present much attention is being devoted to the study of self-monitoring materials, which simultaneously offer good structural and sensing properties. In the present study self-sensing carbon–glass hybrid structural composites, behaving as 'guard' sensors (i.e. they give a warning when fixed loads are reached) were designed, manufactured and tested. In particular, samples containing different carbon fibre/glass fibre ratios were prepared and tested, by performing both mechanical (monotonic and cycle tensile tests) and electrical measurements. The results showed the efficiency of the proposed system and the possibility to design such materials to suit any specific application need. The advantages of these materials, compared to other more sophisticated monitoring systems, are the ease of fabrication and use, low production costs and versatility, so such materials are suitable for widespread low-cost applications
Caratterizzazione di leghe Sn-In-Cu per saldatura
No full textIn questo lavoro vengono presentati i risultati delle prove di corrosione e delle prove di trazione condotte su tre tipologie di campioni di lega per saldatura 75Sn-24In-1Cu. La prima serie è una “as cast” ovvero la lega come uscita dal getto di fusione, mentre sulle altre due tipologie sono stati effettuati un processo di laminazione e un processo di laminazione seguito da una ricottura. I campioni sono stati sottoposti a prove di resistenza di corrosione in NaCl 3% ed effettuando misure di Spettroscopia di Impedenza (EIS) ed i dati sono stati analizzati mediante l’uso di circuiti equivalenti. Sono state realizzate prove di trazione semplice su tutte le tipologie di lega
Advances in jewellery microcasting
No full textTraditional moulds for jewellery casting are made of SiO2 refractory particles agglomerated by a bonding phase. Typical precious alloys are moulded around 1100°C, a temperature that might lead to partial thermal decomposition of the bonding phase, typically CaSO4. The degradation process usually causes release of gas, e.g. SOx, which is responsible for high porosity and roughness in the casting. These gas imperfections are responsible for about 10% of the overall casting failures. The study of novel bonding phases, developed to eliminate gas defects and improve mechanical strength, is reported in this paper. In traditional moulds, bonding is generated during the investment stage, the new phases are obtained during ceramic burnout. New moulds are made from a mixture of quartz and CaO powders, and in the investment stage, quartz particles are embedded in a network of Ca(OH) 2. In the next firing, Ca(OH)2 first dehydrates and then reacts with the surface of SiO2 particles to form Ca xSiOx+2 phases. These interfacial compounds provide a refractory scaffold for SiO2. The process has been studied by TG-DTA. Different firing temperatures have been tested and the silicate moulds have been studied by XRD. Mechanical and casting performances have been evaluated by compression tests and microstructural analysis. Cast comparison with respect to the traditional refractory is also illustrated. © 2004 Elsevier B.V. All rights reserved
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