Classification of ductile cast iron specimens: A machine learning approach

In this paper an automatic procedure based on a machine learning approach is proposed to classify ductile cast iron specimens according to the American Society for Testing and Materials guidelines. The mechanical properties of a specimen are strongly influenced by the peculiar morphology of their graphite elements and useful characteristics, the features, are extracted from the specimens’ images; these characteristics examine the shape, the distribution and the size of the graphite particle in the specimen, the nodularity and the nodule count. The principal components analysis are used to provide a more efficient representation of these data. Support vector machines are trained to obtain a classification of the data by yielding sequential binary classification steps. Numerical analysis is performed on a significant number of images providing robust results, also in presence of dust, scratches and measurement noise

Mineralogy of sediments from AND-2A drill core (McMurdo Sound, Antarctica)

The present study deals with a combined clay-heavy mineral analysis of marine sediments recovered in 2007 in the McMurdo Sound region (Ross Sea, Antarctica) during the ANtarctic DRILLing Program (ANDRILL) - Southern McMurdo Sound Project. The main objectives are to: 1) study how clay minerals reflect paleoclimatic conditions, in particular the Mid-Miocene Climatic Optimum, 2) investigate how heavy mineral assemblages reflect different source rocks and hence different provenance areas 3) study the ice sheet development in East-Antarctica in the last 20 Ma. The AND-2A drill core recovered several stratigraphic intervals that span from Early Miocene to Pleistocene and it collected a variety of terrigenous clastic lithologies. The clay mineral assemblages of the 1138,54 m thick sedimentary succession have been analyzed through X-Ray Diffraction (XRD) analyses on clay fraction, Field Emission scanning Electron Microscopy (FESEM), Scanning Electron Microscopy (SEM) observations and SEM-EDS microanalyses on smectite particles. SEM observations and SEM-EDS microanalyses were carried out on heavy mineral samples starting from 650 mbsf. In the upper sedimentary sections (36 - 440 mbsf, 0.7 - 16.5 Ma) smectites are interpreted to be predominantly detrital, whereas in the lower portion of the core (440 -1123.20 mbsf, 18.5 - 20.2 Ma) authigenic smectites are the most common feature. The predominance of illite, the abundance of chlorite and the nature of smectites in the upper part of the core indicate physical weathering under cold and dry climate and dominant provenance for the clay minerals from the Transantarctic Mountains. Smectites in the lower section are considered mostly authigenic and they are probably the result of early diagenetic processes being formed from the alteration of volcanic material and/or through precipitation from fluids of a possible hydrothermal origin. The heavy mineral analysis shows that the sediments are a mix of detritus dominated by McMurdo Volcanic Group (MVG) sources most likely located in the present-day Mount Morning area (Proto-Mount Morning) with minor contribution from Transantarctic Mountains (TAM) rocks located west of the drill site. The clay and heavy mineral records of the lower 650 mbsf indicate that an ice sheet similar in size to modern ice sheet was periodically present between 17.6 and 19.3 Ma and between 20.1 and 20.2 Ma. The clay and heavy mineral records of AND-2A drill core have increased our understanding of the timing and spatial distribution of ice sheet growth and decay in the McMurdo Sound region during Early Miocene (15.9 - 20.2 Ma) and the Miocene Climate Optimum (ca. 15 - 17 Ma). The present study has demonstrated that the occurrence of authigenic clay minerals may conduct to incorrect paleoclimatic interpretations. Therefore, detailed clay mineral analyses, possibly integrated with heavy mineral study, are necessary for reconstructing sediment provenance and consequently ice-sheet dynamics. // Il presente studio riguarda un’analisi combinata dei minerali argillosi e pesanti dei sedimenti marini recuperati nel 2007 nella regione del McMurdo Sound (Mare di Ross, Antartide) durante il progetto ANtarctic DRILLing Program (ANDRILL) - Southern McMurdo Sound. I principali obbiettivi sono quelli di: 1) studiare come i minerali argillosi riflettono le condizioni paleoclimatiche; 2) investigare come le associazioni di minerali pesanti riflettono le differenti rocce sorgenti e quindi le diverse aree di provenienza; 3) studiare il comportamento della calotta glaciale nell’Antartide Orientale durante gli ultimi 20 milioni di anni. La perforazione AND-2A ha recuperato numerosi intervalli stratigrafici che spaziano dal Miocene medio al Pleistocene e ha collezionato una varietà di litologie terrigene clastiche. Le associazioni di minerali argillosi della successione sedimentaria spessa 1138,54 m sono state analizzate mediante diffrattometria a raggi X (XRD) sulla frazione argillosa, attraverso osservazioni in microscopia elettronica a scansione ad emissione di campo (FESEM) e microscopia elettronica a scansione (SEM) e microanalisi SEM-EDS sulle particelle di smectite. Delle osservazioni al SEM e microanalisi SEM-EDS sono state effettuate sui minerali pesanti a partire da 650 m di profondità. Nelle sezioni sedimentarie superiori (36 - 440 mbsf, 0.7 - 16.5 Ma) le smectiti sono interpretate come prevalentemente detritiche, mentre nella porzione inferiore della perforazione (440 - 1123.20 mbsf, 18.5 - 20.2 Ma) le smectiti autigene sono la caratteristica più comune. La predominanza dell’illite, l’abbondanza della clorite e la natura delle smectiti nella parte superiore della perforazione indicano un’alterazione di carattere fisico in climi freddi e asciutti e la provenienza dominante dei minerali argillosi dalle Montagne Transantartiche. Le smectiti nella sezione inferiore sono considerate principalmente autigene e sono verosimilmente il risultato di processi di diagenesi precoce essendosi formate dall’alterazione di materiale vulcanico e/o attraverso la precipitazione da fluidi di possibile origine idrotermale. L’analisi dei minerali pesanti dimostra che i sedimenti sono un insieme di detrito dominato da rocce sorgenti del McMurdo Volcanic Group (MVG) verosimilmente ubicate nell’area dell’attuale Mount Morning (Proto-Mount Morning), con un contributo inferiore dalle rocce delle Montagne Transantartiche (TAM) situate ad ovest del sito di perforazione. I record dei minerali argillosi e dei minerali pesanti degli ultimi 650 m della perforazione indicano che una calotta glaciale simile nelle dimensioni all’attuale calotta glaciale era periodicamente presente tra 17.6 e 19.3 Ma e tra 20.1 e 20.2 Ma. I record dei minerali argillosi e di quelli pesanti hanno migliorato la nostra conoscenza della distribuzione spaziale e temporale della crescita e della diminuzione della calotta glaciale nella regione del McMurdo Sound durante il Miocene Inferiore (15.9 - 20.2 Ma) e durante l’Optimum climatico miocenico (ca. 15 - 17 Ma). Il presente studio ha dimostrato che la presenza di minerali argillosi autigeni può condurre ad incorrette interpretazioni paleoclimatiche. Per questo motivo sono necessarie delle analisi dettagliate sui minerali argillosi, possibilmente integrate con uno studio dei minerali pesanti, per ricostruire la provenienza dei sedimenti e di conseguenza le dinamiche della calotta glaciale

Ductile cast irons: microstructure influence on fatigue crack propagation resistance

Microstructure influence on fatigue crack propagation resistance in five different ductile cast irons (DCI) was investigated. Four ferrite/pearlite volume fractions were considered, performing fatigue crack propagation tests according to ASTM E647 standard (R equals to 0.1, 0.5 and 0.75, respectively). Results were compared with an austempered DCI. Damaging micromechanisms were investigated according to the following procedures: - "traditional" Scanning Electron Microscope (SEM) fracture surfaces analysis; - SEM fracture surface analysis with 3D quantitative analysis; - SEM longitudinal crack profile analysis - Light Optical Microscope (LOM) transversal crack profile analysis

Modeling early neuronal development in Kabuki Syndrome using human induced pluripotent stem cells.

Neurodevelopmental disorders (NDDs) are disabilities in which the formation and development of the central nervous system is altered. NDDs severely impact the quality of life of the individuals that are affected by them, however little is known about the causes or the molecular mechanisms that are behind their onset. For this reason, being able to model them is pivotal to our society since, by understanding the mechanisms underlying such disorders, we could develop possible treatments. Previous research has suggested that disturbances in the early neuronal development could be at the basis of NDDs onset. Therefore, in this work, I have modeled neuronal differentiation in Kabuki syndrome (KS), a known NDD, assaying the expression of key early neurodevelopmental markers at four specific timepoints, using induced pluripotent stem cell (iPSC) technology. By concurrently differentiating three KS patient-derived and three control iPSC lines to neural precursor cells (NPCs) and profiling them with immunocytochemistry (ICC) and quantitative real-time PCR (RT-qPCR), I was able to identify differences in the early developmental trajectories of NPCs between the two conditions. The ICC data suggested that differentiating KS cell lines incur in precocious differentiation when compared to control cell lines, suggesting that the disease-causing mutations could lead to accelerated neuronal maturation of early NPCs. However, RT-qPCR analysis of the expression patterns of key neurogenesis markers was unable to statistically confirm the observed trend between the two phenotypes, likely due to limitations in statistical power. Despite this, the expression of four out of seven NPC markers was higher in early KS cells than in control cell lines, supporting the hypothesis of accelerated neuronal maturation. Taken together, this work highlighted some of the challenges related to iPSC-based disease modelling studies, and the need to further confirm the inferred mechanisms of asynchronous neuronal development observed in this work

Graphite nodules features identifications and damaging micromechanims in ductile irons

Ductile irons mechanical properties are strongly influenced by the metal matrix microstructure and on the graphite elements morphology. Depending on the chemical composition, the manufacturing process and the heat treatments, these graphite elements can be characterized by different shape, size and distribution. These geometrical features are usually evaluated by the experts visual inspection, and some commercial softwares are also available to assist this activity. In this work, an automatic procedure based on an image segmentation technique is applied: this procedure is validated not only considering spheroidal graphite elements, but also considering other morphologies (e.g. lamellae)

Pearlitic Ductile Cast Iron: mechanical properties gradient analysis in graphite elements

Abstract Ductile Cast Irons (DCIs) are able to combine a good versatility and high performances with a low cost, especially if compared to steels with analogous performances. For these reasons, although these grades have been relatively recently developed, DCIs applications are more frequent. Analyzing the damaging micromechanisms in static, quasi-static or cyclic conditions, the analysis of the role played by the graphite elements is not univocal. Sometimes, they are considered as voids embedded in a more or less ductile matrix, sometimes they are considered as a soft but homogeneous material. In this work, the role played by the graphite nodules in pearlitic grains is reviewed and their mechanical properties are investigated by means of nanohardness tests

Fatigue microstructural evolution in pseudo elastic NiTi alloy

Abstract Shape memory property characterizes the behavior of many Ti based alloys (SMAs). This property is due to a metallurgical phenomenon, which allows to change the lattice structure without boundaries changing as a reversible transition. Equiatomic NiTi alloys are among the most industrially used SMAs: they are characterized by two different mechanical behaviors in terms of shape recovering: • a shape memory effect (SME). This is obtained when the recovery of the initial shape takes place only after heating over a critical temperature, with a consequent crystallographic structure transition; • a pseudoelastic effect (PE). This is obtained when the critical temperature is lower than environmental temperature. In this case, the recovery of the initial shape takes place only after unloading. In recent years, research relating to materials of shape memory has gone in the direction of application in many fields of engineering such as aerospace or mechanical systems. In this work the evolution of microstructural lattice has been studied taking in to account the effect of low cycles fatigue loads

analysis of the intergranular corrosion susceptibility in stainless steel by means of potentiostatic reactivation tests

Abstract: Intergranular corrosion cracking in stainless steels is a selective corrosion attack due to a local (grain boundary) Cr depletion. An undesired Cr carbides (Cr 23 C 6 ) precipitation after heat treatment in the sensitization temperature range (usually between 550 and 850°C, depending on the steel chemical composition) is obtained with a kinetics that is mainly influenced by the C content. In this work, the sensitization susceptibility of four sensitized stainless steels was investigated by means of potentiostatic reactivations tests. In addition, chronoamperometric tests and scanning electron microscope (SEM) observations of the specimens surfaces were performed in order to analyze the evolution of the corrosion morphologies

duplex stainless steels 475 c embrittlement influence of the chemical composition on the fatigue crack propagation

Abstract: Duplex stainless steels (DSSs) are prone to age hardening and embrittle over a wide temperature range depending on their chemical composition. This is mainly due to precipitation phenomena that may occur inside ferrite grains and at ferrite-austenite grain boundaries. The aim of this work is the analysis of chemical composition influence on fatigue crack propagation resistance of "475°C embrittled" duplex stainless steels. Fatigue crack propagation resistance of 21 Cr 1 Ni, 22 Cr 5 Ni and 25 Cr 7 Ni duplex stainless steels was investigated considering both as received and 475°C embrittled conditions (1000h). Microstructural analyses were performed using a transmission electron microscope (TEM). Concentrations of the main elements, but carbon, were evaluated using a standardless analysis program