Fictitious Domain methods for simulating thermo-hydro-mechanical processes in fractures

<p>Fictituous domain methods provide an promising way for simulating fluid structure interaction in fractures with complex geometries. The main characteristic of the method is that the solid and the fluid problem are simulated on different, non-matching meshes, with the solid being immersed into the fluid. The problems are coupled by L<sup>2 </sup>- projections, which transfer physical variables between the two computational domains and either the penalty, augmented Lagrangian or Lagrange multiplier method to represent the solid in the fluid. We show the evolution of our framework in the last three years, starting with benchmark problems such as Poiseulle flow, with successive extension to contact, fracture intersections and thermal coupling.</p>

Inverse problem of contact fracture mechanics for a hub of friction pair taking into account thermal stresses

Methods of fracture mechanics enable a new approach to the design of structures, ensuring prevention of crack development. The plane problem of mechanics of contact fracture for the hub of a friction pair during operation is studied. It is accepted that near the rough friction surface, the hub has a rectilinear crack. A criterion and a method for solving the inverse problem of the mechanics of contact fracture on definition of the function of displacements of external contour points of the hub of a friction pair with regard to temperature drop and inequalities of the contact surface in friction pair components is given. The found function of displacements of the external contour points of the hub provides an increase of the load-bearing capacity of the hub of a friction pair. The problem of prevention of the fracture of the hub of a friction pair with allowance for the real friction surface was first posed and then solved.

Characterization of Hydrogen-Induced Contact Fracture in High-Strength Steel

This study investigated the hydrogen embrittlement (HE) cracking behavior produced by local contact loading of high-strength steel. When a spherical impression was applied to a hydrogen-absorbed high-strength steel, HE induces contact fracture, where radial cracks are initiated and propagated from the indentation impression. The length of the radial crack was found to be dependent on the hydrogen content in the steel as well as the applied contact force. A combined experimental/computational investigation was conducted in order to clarify the mechanism of hydrogen-induced contact fracture. In the computation, crack propagation was simulated using a cohesive zone model (CZM) in finite element method (FEM), in order to elucidate stress criterion of the present HE crack. It was found that the normal tensile stress was developed around impression, and it initiated and propagated the HE crack. It was also revealed that the hydrogen content enhanced contact fracture damage, especially the resistance of crack propagation (i.e., threshold stress intensity factor, Kth). The findings may be useful for countermeasure of contact fracture coupled with hydrogen in high-strength steel. Such phenomenon is potentially experienced in various contact components in hydrogen environment.