High Strength Steels Fracture Toughness Variation by the Media

The stress corrosion cracking process is at this moment an unknown mechanism of deterioration. It is a process that implies the joint action of the media, the presence of corrosion or a surface defect and of stress in the metal. Prestressing tendons can suffer SCC jointly with hydrogen embrittlement which dramatically changes not only the type of fracture (from ductile to brittle) but also the kinetics of the process leading to unexpected collapses. The metal should be resistant to this type of process which can be characterized by its toughness and therefore by its damage tolerance. This research shows that the Fracture Toughness change when the steel corrodes, questioning the idea that is an intrinsic characteristic of the material. The reduction in the fracture toughness of steel wires when they are in contact to aggressive media involve that the material fractures with a lower crack depth for the same stress level. That means that the material becomes less damage tolerant, which implies that it is necessary to detect defects of smaller size, as for example, small notch, pits or superficial cracks. In the paper some results of the percentage of decrease of the toughness of prestressing wires suffering corrosion are presented

Stress corrosion cracking and fracture toughness variation of high strength steels.

The stress corrosion cracking process is at this moment an unknown mechanism of deterioration. It is a process that implies the joint action of the media, the presence of corrosion or a surface defect and of stress in the metal. Prestressing tendons can suffer SCC jointly with hydrogen embrittlement which dramatically changes not only the type of fracture (from ductile to brittle) but also the kinetics of the process leading to unexpected collapses. The metal should be resistant to this type of process which can be characterized by its toughness and therefore by its damage tolerance. This research shows that the Fracture Toughness change when the steel corrodes, questioning the idea that is an intrinsic characteristic of the material. The reduction in the fracture toughness of steel wires when they are in contact to aggressive media involve that the material fractures with a lower crack depth for the same stress level. That means that the material becomes less damage tolerant, which implies that it is necessary to detect defects of smaller size, as for example, small notch, pits or superficial cracks. In the paper some results of the percentage of decrease of the toughness of prestressing wires suffering corrosion are presented

Hydrothermal monitoring using embedded sensors of the actual roof system of the prado museum

El Prado Museum in Madrid has been recently submitted to a refurbishment of its roof which from been made with the traditional tiles has been changed to the use of modern waterproofing layers covered with a metallic lead finishing. Due to an unexpected damp patch that produced leaking in the hall in which Las Meninas by Velázquez was exhibited, the authors were commissioned by the Ministry of Education and Culture to study the suitability of the roof and its waterproofing properties. The study led to suggestions of modifications in the design of the roof layers, which are out of the scope of present paper. In present paper are given the behaviour of the sensors embedded in two specific areas of the roof. The sensors installed were of: temperature, relative humidity, measurement of local strain and detection of liquid water. The liquid water sensors reveal that some water is withheld in the layer just below the thermal insulation material, although it is standing. The results of over four years of readings show that the temperature attenuates over distance away from the outermost layer, where the readings are very high in summer, due to it consists of lead. During the colder seasons, in turn, the temperature in the inner layers of the roof is higher than in the outer layers. The strain recorded follows the logical evolution of temperature with no abnormal behaviour being detected. Some of relative humidity sensors had measuring problems due to water condensing on them. In summary however, if the behaviour in this area is extrapolated to the rest of the roof, it can be considered to perform correctly as intended. No more leaking events have been detected from the design modifications were incorporated to the existing roof

Ab-initio molecular dynamics simulation of hydrogen diffusion in α\alpha-iron

First-principles atomistic molecular dynamics simulation in the micro-canonical and canonical ensembles has been used to study the diffusion of interstitial hydrogen in $\alpha$-iron. Hydrogen to Iron ratios between $\theta=1/16 and 1/2 have been considered by locating interstitial hydrogen atoms at random positions in a$2 \times 2 \times 2$ supercell. We find that the average optimum absorption site and the barrier for diffusion depend on the concentration of interestitials. Iron Debye temperature decreases monotonically for increasing concentration of interstitial hydrogen, proving that iron-iron interatomic potential is significantly weakened in the presence of a large number of diffusing hydrogen atoms

Molecular Dynamics simulations of Hydrogen Embrittlement: preliminary results

Hydrogen embrittlement is believed to be one of the main reasons for cracking of structures under stress. High strength steels in these structures often include a ferritic core made of alpha-iron (body centered cubic lattice). Previous work [1] was concerned with the interaction of atomic hydrogen with iron using first principles calculations. We studied the effect of interstitial hydrogen in the iron lattice and the stress induced by the interstitial hydrogen in the host lattice. In this paper we study the dynamical behaviour of hydrogen inside the iron lattice. Using ab-initio Molecular Dynamics we obtain hydrogen diffusion paths and by taking statistical averages we extract diffusion coefficients from Einstein’s equation. Depending on temperature, the diffusion path involve going through tetrahedral or octahedral sites. Simulations where a number of hydrogens occasionally coincide in one unit cell have been performed to elucidate the effect of interactions between hydrogen

Integrated geophysical-petrological modeling of lithosphere-asthenosphere boundary in central Tibet using electromagnetic and seismic data

We undertake a petrologically driven approach to jointly model magnetotelluric (MT) and seismic surface wave dispersion (SW) data from central Tibet, constrained by topographic height. The approach derives realistic temperature and pressure distributions within the upper mantle and characterizes mineral assemblages of given bulk chemical compositions as well as water content. This allows us to define a bulk geophysical model of the upper mantle based on laboratory and xenolith data for the most relevant mantle mineral assemblages and to derive corresponding predicted geophysical observables. One-dimensional deep resistivity models were derived for two groups of MT stations. One group, located in the Lhasa Terrane, shows the existence of an electrically conductive upper mantle layer and shallower conductive upper mantle layer for the other group, located in the Qiangtang Terrane. The subsequent one-dimensional integrated petrological-geophysical modeling suggests a lithosphere-asthenosphere boundary (LAB) at a depth of 80¿120 km with a dry lithosphere for the Qiangtang Terrane. In contrast, for the Lhasa Terrane the LAB is located at about 180 km but the presence of a small amount of water in the lithospheric mantle (<0.02 wt%) is required to fit the longest period MT responses. Our results suggest two different lithospheric configurations beneath the southern and central Tibetan Plateau. The model for the Lhasa Terrane implies underthrusting of a moderately wet Indian plate. The model for the Qiangtang Terrane shows relatively thick and conductive crust and implies thin and dry Tibetan lithosphere.Peer Reviewe

Velocity-conductivity relations for cratonic lithosphere and their application : example of Southern Africa

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 14 (2013): 806–827, doi:10.1002/ggge.20075.Seismic velocity is a function of bulk vibrational properties of the media, whereas electrical resistivity is most often a function of transport properties of an interconnected minor phase. In the absence of a minor conducting phase then the two should be inter-relatable primarily due to their sensitivity to temperature variation. We develop expressions between shear wave velocity and resistivity for varying temperature, composition, and water content based on knowledge from two kimberlite fields: Jagersfontein (Kaapvaal Craton) and Gibeon (Rehoboth Terrane). We test the expressions through comparison between a new high-resolution regional seismic model, derived from surface wave inversion of earthquake data from Africa and the surrounding regions, and a new electrical image from magnetotelluric (MT) data recorded in SAMTEX (Southern African Magnetotelluric Experiment). The data-defined robust linear regression between the two is found to be statistically identical to the laboratory-defined expression for 40 wt ppm water in olivine. Cluster analysis defines five clusters that are all geographically distinct and tectonically relate to (i) fast, cold, and variably wet Kaapvaal Craton, (ii) fast and wet central Botswana, (iii) slow, warm, and wet Rehoboth Terrane, (iv) moderately fast, cold, and very dry southernmost Angola Craton, and (v) slow, warm, and somewhat dry Damara Belt. From the linear regression expression and the MT image we obtain predicted seismic velocity at 100 km and compare it with that from seismic observations. The differences between the two demonstrate that the linear relationship between Vs and resistivity is appropriate for over 80% of Southern Africa. Finally, using the regressions for varying water content, we infer water content in olivine across Southern Africa.We wish to again acknowledge the three main funding agencies, the U.S. National Science Foundation’s Continental Dynamics Program (grant EAR0455242 to RLE), the South African Department of Science and Technology (grant to South African Council for Geoscience), and Science Foundation Ireland (grant 05/RGP/GEO001 to AGJ), for their support. Industry support for SAMTEX from De Beers Group Services, BHP Billiton and Rio Tinto Mining and Exploration resulted in a program far more extensive than originally conceived. S.F. has been supported by the NERC New Investigator grant NE/G000859/1. M.M. wishes to thank Science Foundation Ireland (grant 08/RFP/GEO1693 SAMTEX to AGJ) for support. J.F. wishes to thank Enterprise Ireland (grant Topo-Med to AGJ), Science Foundation Ireland (grant 10/IN.1/I3022 IRETHERMto AGJ), and the JAE-DOC Programme from Spanish CSIC, cofunded by FSE for support.2013-10-0

Evidence for surface uplift of the Atlas Mountains and the surrounding peripheral plateaux: Combining apatite fission-track results and geomorphic indicators in the Western Moroccan Meseta (coastal Variscan Paleozoic basement)

This work represents an initial attempt to link the evolution of the topography in relation to the general tectonic framework of western Morocco. For this purpose, in a section of the Western Moroccan Meseta different tools are combined in order to attain the general objective. Apatite fission-track (AFT) data of granitic rocks of the Rabat–Khenifra area give ages around 200 Ma with track length distributions which are compatible with the thermal models already established for the area. An inverse correlation between AFT ages and elevation is observed which is compatible with previous models indicating northward tilting of the whole Western Moroccan Meseta which is younger than 20–25 Ma. In order to test this possibility a detailed analysis of the topography at different scales in the Western Moroccan Meseta has been performed. Results indicate that two open folds with different amplitudes are recognized and that the one with wider wavelength could correspond to a lithospheric fold as previously stated by other authors on the basis of independent geological arguments. The northward tilting proposed based on the AFT data agrees with the results obtained in the analysis of the topography which reinforces the presence of a very open fold with a wavelength of 200–300 km in the north-western limb of the Western Moroccan Meseta

CIFRA: Challenging the ICT Patent Framework for Responsible Innovation. D3.2: Report on Assessment of Impact of proposed new Framings

The European Commission. CIFRA: Challenging the ICT Patent Framework for Responsible Innovation. Grant Agreement No.731940. Research and Innovation Action. Call: H2020-ICT-35-201

CIFRA: Challenging the ICT Patent Framework for Responsible Innovation. D4.3: Paper to well-recognized journals

The European Commission. CIFRA: Challenging the ICT Patent Framework for Responsible Innovation. Grant Agreement No.731940. Research and Innovation Action. Call: H2020-ICT-35-201