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Seigneurie princiere, le comte de Dunois (cree en 1439 au profit de Jean, bâtard du duc d’Orleans) fut le siege d’un tabellionage dont une centaine de registres ont ete conserves. Leur etude permet d’etudier le travail quotidien des tabellions, ces notaires du nord de la France, qui ont ete l’objet d’un renouveau historiographique au cours des dernieres annees. Ils temoignent de l’uniformite des pratiques du tabellionage dans le Nord du royaume au xve siecle et nous permettent de connaitre les methodes de travail (les jours, les lieux), les origines, les activites economiques et l’integration dans la societe des tabellions. L’etude d’un cas particulier montre le parcours professionnel d’un homme, a partir de l’echelon le plus bas (clerc du bailliage) jusqu’au poste de tabellion. L’etude de son patrimoine foncier et de ses alliances matrimoniales illustre son ascension sociale : il devient membre de l’elite dunoise et integre la noblesse locale.

International audience

An experimental and numerical study of the scratch test on FeB/Fe 2 B bilayers is presented. The boride layers were formed at the surface of AISI 304 steels by developing the powder-pack boriding process at temperatures of 1223 K for 2, 6 and 10 h of exposure times. From the set of experimental conditions of the boriding process, scratch tests were performed with a linearly-increasing load mode of 1 to 90 N on 7 mm in length to determinate the most effective and informative testing conditions and to estimate the critical load (L c ) at which the boride layer fails. The damage in the boride layer was examined by high resolution SEM. Experiments tests indicated that at a critical load the boride layer fails through brittle fracture. Numerical calculations considering the residual stress field generated by the scratch load showed that at this load the tensile stresses inside the boride layer become large enough to cause brittle failure. The residual stress fields generated by the scratch load were analyzed and related with the failure mechanisms observed by the experimental tests.

International audience

Prior to the detection and monitoring by acoustic emission of defects in steel, this paper deals with the use of waveguide that avoids direct contact between the sensor and monitoring structure when working at high temperature. The study of the waveguide effect on elastic wave transmission shows that waveguide deforms the waveform but it does not affect its frequency. Waveguide length does not affect signal magnitude. An experimental example of compact tensile specimen monitoring by acoustic emission is given. The monitoring of the damage at low and high temperature “450 °C” by acoustic emission enables us to identify crack propagation stages and their acoustic signature.

Two Lock-in InfraRed Thermography (LIRT) techniques were developed and applied to detect interfacial defects in a ceramic coated steel plate deposited by plasma spraying technology. Stimulations were performed either by electromagnetic waves (lamps) or by high power ultrasonic waves (sonotrode). The first one is based on remote optical heating of the area of interest; while the second technique is based on the mechanical loss angle effect, occurring locally and for particular defects such as cracks and delaminations. The potential of these two techniques was evaluated against artificial (calibrated holes) and real (disbonding) interfacial defects. The results show success and also some limitations of both LIRT techniques in function of sizes and depths of ceramic coating interfacial defects.

As a result of the demand for increasing the operating life of aeronautic parts, it is sought in this work to optimize the mechanical characteristics of a bearing submitted to marine environment. Phase transformations during high speed austenizing have been studied together with the influence of thermal stresses due to induction heating. It is observed that there are two ways to obtain the best mechanical properties among which the shortest cycle could be used to reduce heat treatment time of highly alloyed cold work steels.

The aim of this work is to investigate the fracture behavior of a stationary crack lying along the interface in a coated system during interfacial indentation test. One traditional 3D numerical model and one cohesive element numerical model have been made to study the Vickers indentation test process. A crack-block approach is applied to generate 3D meshes containing the crack front along the interface. The stress intensity factors and the energy release rates (G) on the crack front are computed. The fracture mode mixity is also presented. It is found that the near surface propagation of the crack can be prevented during loading due to compressive stresses. It may occur during unloading due to residual stresses resulting from plastic strain.

The growing needs for energy combined with the will to reduce CO2 emissions lead to the increase of the demand for liquefied natural gas (LNG), which will be stably available for many decades to come. Cryogenic materials used for the manufacture of the inner tanks for LNG storage are composed of 9% Ni steel plates with excellent low-temperature toughness, great ductility and crack resistance for a high safety level. To guarantee the reliability and safe operation of large-scale metallic structures exposed to cryogenic temperatures for extended periods, it is important to evaluate structural and mechanical properties of the metal base as well as the welded zone in their own operating conditions in order to prevent damages that could occur.

International audience

International audience; This paper presents the development of V(z) inversion technique and its application to quantitative determination of interface adhesion by measuring interface tangential stiffness parameter KT. The measurement is performed in two steps on an air plasma sprayed bronze–aluminum alloy coating (on a steel substrate) having different adhesion levels: the determination of the coating elastic constants and the determination of the interface tangential stiffness KT are performed by optimizing the inverted angular-frequency reflectance function R(θ,f). The results obtained by the V(z) inversion are then compared to mechanical testing by interfacial indentation on the same sample. The same behavior (quality of interface adhesion) can be seen by both methods: the coating adhesion decreases as the interfacial stiffness parameter KT decreases.

International audience; Railway networks are subjected to more and more severe loading conditions requiring the use of steels with a high resistance to wear and good fatigue behaviour. The surveys carried out on out of use equipment, such as rails or switches, show that these equipments fail by wear after quite a long period of use, but they can fail by fatigue in a substantially shorter time. In service, crossings are submitted to rolling, impact and sliding stresses. The impact-sliding is the result of the wheel transition from rail wing to crossing nose. Very high contact forces act on the crossing nose while such wheels are passing over it. These large contact forces between wheel and crossing can cause severe damage at crossing nose and wing rail. The influence of contact parameters on the damage of the crossing alloy (Hadfield steel GX120Mn13) in comparison with rail steel (R260) was investigated by impact and impact-sliding tests. The results are described and discussed using weight loss and microhardness measurements, optical and scanning electron microscopy observations of the contact surface. Examination of the results shows large plastic deformation in surface and subsurface of samples. In comparison with impact tests, sliding produces a change in size and shape of the contact area, a higher weight loss and lower hardening. A better impact-sliding wear resistance of Hadfield steel has been confirmed.

International audience; Hadfield steel is well known for its high work hardening capacity and wear resistance. The alloy X120Mn12 is specifically used in railroad castings such as frogs and crossings in west European countries such as France. The influence of various contact parameters on the mechanical behaviour of this alloy was investigated by rolling contact tests. The results are described and discussed using micro-hardness measurements, optical and scanning electronic microscopy and EBSD analyses.

International audience; abstract simple

International audience

One of the methods used for the evaluation of coating adherence consists of determining an apparent interfacial fracture toughness through interfacial indentation in the cross-section of the coated system. In the present paper the interfacial crack propagation in a thermal spray coated system, during interfacial indentation test, was studied by finite element method. A Vickers indenter was applied at the coating/substrate interface to perform indentation test. In order to simulate the cracking, an initial semi-circular crack lying at the interface between the substrate and the coating was considered. Since the cracks resulting from interfacial indentation test have been reported to have a semi-circular shape, the crack was forced to advance by a uniform distance normal to the crack front in the plane of interface at each step of calculation. In these conditions it was shown that the interfacial crack has a mixed fracture mode. An apparent interfacial fracture energy Jca was calculated by this method to evaluate the interfacial adhesive toughness. The model was applied to study the crack propagation at the interface between a Cr3C2-NiCr HVOF coating and a grey cast iron substrate. A reasonable agreement between the calculation results and reported experimental data was found.

International audience; abstract simple