The microstructure and softening behaviour have been investigated in an aluminum plate heavily deformed by equal channel angular extrusion and subsequently annealed at 170 °C. It is found that at this temperature the microstructure evolves by coarsening with no apparent signs of recrystallization even after 2 h of annealing. Both coarsening and softening are rapid within first 10 minutes of ann...

We present a refinement and coarsening algorithm for the adaptive representation of Right-Triangulated Irregular Network (RTIN) meshes. The refinement algorithm is very simple and proceeds uniformly or locally in triangle meshes. The coarsening algorithm decreases mesh complexity by reducing unnecessary data points in the mesh after a given error criterion is applied. We describe the most impor...

The development of high temperature aluminum alloys able to operate up to 400 oC is crucial to replace steel and titanium and decrease the mass of vehicles in the automotive and aerospace industries. This review relates the past two decades of aluminum alloy engineering done at Northwestern University focusing on developing coherent L12 Al3M nanoprecipitates strengthened aluminum alloys that ar...

Adaptive, unstructured grid methods, in which the mesh is allowed to deform, and grid quality subsequently restored through localized coarsening and refinement, offer the potential of a more rapid, straightforward approach to generalized moving body problems. Automation of this mesh movement and quality correction strategy requires a close coupling with the flow solution process. With parallel ...

Some pattern formation processes on single-crystal catalytic surfaces involve transitions between alternative surface phases coupled with oscillatory reaction dynamics. We describe a two-tier symmetry-breaking model of this process, based on nanoscale boundary dynamics interacting with oscillations of adsorbate coverage on microscale. The surface phase distribution oscillates together with adso...

We present maximally fast numerical algorithms for conserved coarsening systems that are stable and accurate with a growing natural time step Deltat=At2/3s. We compare the scaling structure obtained from our maximally fast conserved systems directly against the standard fixed time-step Euler algorithm, and find that the error scales as square root of A--so arbitrary accuracy can be achieved. Fo...

In this paper we introduce a coarsening algorithm for quadrilateral meshes that generates quality, quad-only connectivity during level-of-coarsening creation. A novel aspect of this work is development and implementation of a localized adaptation of the polychord collapse operator to better control and preserve important surface components. We describe a novel weighting scheme for automatic del...

Incomplete LU factorization (ILU) techniques are a well-known class of preconditioners, often used in conjunction with Krylov accelerators for the iterative solution of linear systems of equations. However, for certain problems, ILU factorizations can yield factors that are unstable, and in some cases quite dense. Reordering techniques based on permuting the matrix prior to performing the facto...

Modeling of multiphase flow and transport in highly hetero­ geneous porous media must capture a broad range of coupled spatial and temporal scales. Recently, a hierarchical approach dubbed the Multilevel Multiscale Mimetic (M3) method , was developed to simulate two-phase flows in porous media. The M3 method is locally mass conserving at all levels in its hierarchy, it supports unstructured pol...