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Different kinetics of hydrogen absorption in T40 (grade 2) and TA6V ELI (grade 23) under cathodic polarization in artificial seawater have been highlighted. These polarizations were made by applying potentials from -0.8 to -1.8V/SCE in artificial seawater and NaCl solution. Four stages were identified and related in term of hydrogen ingress, hydrides formation and calcareous deposit growth. The formation of γ and δ-hydrides have been observed, localized and characterized using several techniques. On T40, hydrides form as a layer that increases the surface roughness and clusters form in the bulk after first moments of hydrogen absorption. Whereas in TA6V ELI, hydrogen is absorbed by β-phase leading to a volume expansion of this phase. Then after reaching the hydrogen solubility limit of β-phase, hydrides form on interfaces α/β or α/α and in α grains. For long durations, the hydrogen ingress is limited by the subsurface hydrides and the stabilized calcareous deposit. These different steps are time depend on processes which need to be tacked into account to improve knowledge of hydrogen embrittlement in titanium alloys.

Micro-arc Oxidation (MAO) process is a plasma assisted electrochemical process, which allows formation of ceramic-like dry oxides on top of light alloys surfaces. The good corrosion resistance as well as the low density of titanium alloys are recognized and so required for conception of structural parts in marine environment. However, their tribological behaviour reveals an important tendency to stick-slip phenomenon, which makes use of these alloys for dynamic contact mechanisms difficult. Through the MAO project from IRT M2P, formation of a MAO coating composed of aluminium titanate has been investigated to improve tribological behaviour of a commercially pure titanium (Grade 2) and an α+β alloy (TA6V, Grade 5). Pin-on-disc testing has been carried out to evaluate friction coefficient and the presence or not of stick-slip phenomenon in various contact configurations (involving non-treated titanium surfaces, MAO treated surfaces, with steel or titanium balls …) in dry or artificial seawater media. Those test campaigns are completed by evaluation of fatigue behaviour, and tribological testing on a demonstrator. Finally, this study highlights influence of MAO coating on diminishing (to removed) stick-slip phenomenon, accompanied by a reduction of friction coefficient, whatever the kind of contact (single treated surface or both ones) and the medium.

The effect of hydrogen charging by cathodic polarization on T40 (grade 2) and TA6V ELI (grade 23) in artificial seawater appeared to be dependent on the metallurgical structure of the alloys. Mechanical tensile tests were performed on smooth samples and with different notches without and with hydrogen charging. Evolution of the fracture mode has been studied and the impact of hydrides was questioned. FEM calculation offers the opportunity to associate the local hydrostatic stress σm and equivalent plastic strain εpeq leading to the fracture and to illustrate the evolution of these conditions with hydrogen absorption and hydrides formation. Hydrogen charged by cathodic polarization appeared to have a small impact on grade 2 reducing its A%, whereas it leads to a strong embrittlement of grade 23 when the solubility limit of β-phase is exceeded and hydrides formed.

L’alpinisme est l’une des pratiques sportives les plus affectées par la crise climatique actuelle en raison de l’évolution des milieux physiques de haute montagne. Certains itinéraires ont disparu, d’autres ne sont plus fréquentables en été (exposition aux aléas, difficultés techniques, etc.). Des recherches ont déjà été réalisées sur les impacts du changement climatique sur la pratique de l’alpinisme et l’adaptation des pratiquants. Le massif du Mont-Blanc et les Alpes valaisannes ont ainsi servi de territoires d’étude pour comprendre l’évolution des itinéraires d’alpinisme au cours des dernières décennies. Une cartographie des processus géomorphologiques et glaciologiques affectant des itinéraires d’alpinisme a été réalisée pour le Valais et la présente étude vise à appliquer cette méthode au massif des Écrins, qui restait non étudié malgré son caractère emblématique. Le célèbre topoguide Le massif des Écrins — Les 100 plus belles courses et randonnées (1974) a été utilisé comme base de travail, et 70 itinéraires ont été sélectionnés selon leur fréquentation et leur notoriété. L’ensemble des processus qui les affectent ont été cartographiés sous SIG et une analyse statistique a été réalisée pour mieux comprendre l’évolution des itinéraires, en parallèle d’entretiens semi-directifs auprès d’expert·es et praticien•nes de terrain. Un nouveau processus — la fonte prématurée en saison estivale des couvertures glacio-nivales — a été identifié. Comme pour le massif du Mont-Blanc et le Valais, un itinéraire est en moyenne affecté par neuf processus, et près de 25 % des itinéraires ne sont plus fréquentables l’été. Les itinéraires en neige et mixtes et d’une difficulté supérieure à D (Difficile) sont les plus impactés. La méthode de cartographie a ainsi été appliquée avec succès au massif des Écrins, permettant de compléter les connaissances sur l’évolution récente des itinéraires d’alpinisme.

Mountaineering is one of the most affected sports activities due to the current climate crisis and the resulting changes in the physical environment of the high mountain areas. Some routes have disappeared while others are no longer accessible in summer (hazards, technical difficulties, etc.). Research has already been conducted on the impact of climate change on mountaineering and on adaptation. The Mont-Blanc massif and the Valais Alps have been used as study areas to understand the evolution of mountaineering routes over recent decades. A mapping of the geomorphological and glaciological processes affecting mountaineering routes has been conducted for the Valais. This study aims to apply this method to Écrins massif (French Alps), which had so far remained unstudied despite its emblematic character. The famous topo-guide "Le massif des Écrins - Les 100 plus belles courses et randonnées" (1974) was used as a basis for the study with 70 routes being selected according to their notoriety and visitor numbers. All the processes affecting the routes were mapped using GIS, and a statistical analysis was carried out to gain a better understanding of the evolution of the routes, together with semi-directive interviews with experts and practitioners. A new process – the early summer melting of ice and snow cover – was identified. As is the case in the Mont-Blanc massif and the Valais, a route is affected by 9 processes on average, and almost 25% of the routes can no longer be climbed in summer. The mapping method has been successfully applied to Écrins massif, providing new knowledge of the recent evolution of mountaineering routes in the Alps.

This article analyses a still understudied figure that is present in martyrological accounts of the Early Modern Period: the child martyr which is an intriguing and important character in Catholic propaganda during the wars of religion that shook Europe. We will see how a Jesuit missionary uses this character in his account of the Christian mission in Japan. Nicolas Trigault (1577–1628), in his work L'Histoire des martyrs du Japon (The History of the Martyrs of Japan) takes up a long Christian martyrological tradition while anchoring it in a context of cultural exchanges between Europe and Japan. Using various biblical narratives (whether the Passions of Christ or the martyrdom of the Maccabees) as a point of comparison with these Japanese martyrs, Trigault places these Christians, so far removed from his target audience, in a Catholic community that extends over a long period of time and a vast geographical territory. In this use of the martyrological narrative, the death of the children proves to be a powerful argument. As exceptional figures of martyrdom, they act as witnesses to the level of faith of a community, the sacrifice of the children being the ultimate demonstration of its constancy. However, the figure of the martyred child also comes into conflict with the figure of the morally crippled child, testifying to the ambiguity that European culture and the Christian religion have with this period of life. These stories, later exported to Europe, are used to edify both the youngest children, urging them to imitate their Japanese counterparts, and the parents, presenting an ideal imagery of the Christian family. [ABSTRACT FROM AUTHOR]

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