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Prove di flessione non tradizionali su acciai zincati. Caratterizzazione cinematica e statica del meccanismo ed identificazione dello stato di danneggiamento del rivestimenti
Full text linkThe aim of this work was the analysis of the hot dip zinc coated steel plates mechanical properties by means of a non-tradition bending test performed minimizing both the bending moment differences along the bending axis and the interactions between the clamping system and the specimen coating. A complete kinematic and static mechainism analysis was performed. All the kinematic and static variables were identified in order to completely characterise the specimen deformation mechanism and the stress level. Bending tests were performed both on non-coated and on hot dip zinc coated plates, correlating the measured varia bles (applied load and crosshead displacement) with the bending moment and the specimen bending angle. Tests are characterised by a good repeatability. Results show a crosshead displacement - load diagrams that depend on the main deformation mechanisms. Furthermore, the mechanical behaviour was influenced by the coating thickness. It can be seen throught the load values increase and the crosshead displacement - load diagram modification. For all the investigated coating conditions, radial cracks are observed. They initiate corresponding to the F phase and propagate up to the ζ-η interface. The coating thickness increase implies both an increase of the importance of the cracks in δ and ζ phases and the presence of cracks at ζ-δ interfaces. As a consequence, the increase of coating thickness implies an increase of the susceptibility to a coating-steel debonding damage mechanism, with a consequent loose of the coating adhesion and a decreasing of the capability of the zinc coating to improve the steel corrosion resistance
Provenance and geological significance of red mud and other clastic sediments of the Mugnano cave (Montagnola Senese, Italy)
Full text linkThe Mugnano cave is characterized by a thick clastic sedimentary fill showing a great variability of sedimentary facies, ranging from clay to coarse-grained sand deposits. This paper deals with combined sedimentological and mineralogical (XRD and SEM) studies of these sediments and bedrock insoluble residues in order to understand the origin and geological significance of cave deposits, with particular attention to red mud sediments, often considered as the residue of host rock dissolution. Three different sedimentary facies were recognized: i) YS, yellow sand with occasionally shell fragments, testifying the arrival of sediments from the surrounding landscape; ii) RS, red laminated mud; iii) GS, grey and red-grey mud and sand, dolomite-rich sediments. Furthermore, the results obtained in the present study allowed the identification of two fingerprint minerals: i) quartz, present only as traces in the limestone host-rock, and ii) dolomite, certainly related to the incomplete bedrock dissolution. Results obtained by this multidisciplinary approach testify that no one of the investigated sediments is representative of a completely autochthonous sedimentation (i.e. accumulation of insoluble residue of limestone in a cave environment). In fact, all the three sedimentary facies show a bulk composition rich in quartz, a mineral indicating an external origin for these sediments. Also the grey sediments, despite of their high content of bedrock- related dolomite, are quite rich in quartz and they testify the mixing of autochthonous and allocthonous sediments. The clay fraction of cave sediments shows strong compositional similarities with bedrock insoluble residue and consequently its analysis cannot be considered as a clear proxy for distinguishing between different parent materials. Therefore, the origin of these cave deposits is dominantly related to external sediments inputs, with terra rossa surface soils as the most probable parent material for red mud sediments
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
Fatigue crack propagation in a C70250 alloy
No full textThe fatigue behavior of a C70250 alloy has been studied. The crack propagation behavior was investigated by performing fatigue crack propagation tests at load ratio R varying over the range 0.3–0.7. A considerable crack deflection and jagging was observed at low R-ratio. The study of the crack paths revealed that the closure effect is more relevant for R = 0.3. In this case the crack path is characterized by considerable peak heights and deflection angles and the closure effect is mainly related to the fracture surface mismatch. The main crack propagation micro-mechanisms observed are transgranular with few areas characterized by intergranular fracture
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