Mechanical characterization of alumina coatings on C35 steel

International audienc

Some insights on dynamic rupture modelling using a finite element method

International audienceFinite element methods (FEM), as often used in soil dynamics should be a powerful tool to simulate the dynamic rupture process on earthquake faults, allowing us to take into account the asymmetry of fault geometry with respect to the ground surface as well as material heterogeneity with inelastic properties. A FEM program to model non-linear elastodynamics, GEFDYN, is used to model rupture propagation on a seismic fault. The fault is simulated using "joint-elements" that are thin and flat and may be programmed to simulate a number of frictional properties. We perform preliminary simulations on a single plane fault embedded in a 2D homogeneous unbounded elastic media and compare results with those of a boundary integral equation method. Under uniform initial stress conditions, we release certain amount of stress on a small area of the fault and the dynamic rupture progresses spontaneously controlled by the plastic behaviour of joint-elements used to simulate the Coulomb friction law on the fault. The formulation of the joint elements, as well as the parameters of their constitutive model are analysed and discussed, such as the shear elastic modulus Gjoint. We find it important to carefully treat these joint-elements to obtain the accurate solutions. With these tests, we demonstrate that this tool constitutes an appropriate model to study dynamic rupture propagation on a fault

Elaboration and characterisation of plasma sprayed alumina coatings on nickel with nickel oxide interlayer

International audienc

Continuous dissolved gas tracing of fracture‐matrix exchanges

International audienceTransport in fractured media plays an important role in a range of processes, from rock weathering and microbial processes to contaminant transport, and energy extraction and storage. Diffusive transfer between the fracture fluid and the rock matrix is often a key element in these applications. But the multiscale heterogeneity of fractures renders the field assessment of these processes extremely challenging. This study explores the use of dissolved gases as tracers of fracture‐matrix interactions, which can be measured continuously and highly accurately using mobile mass spectrometers. Since their diffusion coefficients vary significantly, multiple gases are used to probe different scales of fracture‐matrix exchanges. Tracer tests with helium, xenon and argon were performed in a fractured chalk aquifer and resulting tracer breakthrough curves are modelled. Results show that continuous dissolved gas tracing with multiple tracers provide key constrains on fracture matrix interactions and reveal unexpected scale effects in fracture‐matrix exchange rates