We present a level-set based technique to recover key characteristics of a defect or crack (e.g. location, length and shape) in a two-dimensional material from boundary electrical measurements. The key feature of this work is to extend the usual level-set technique for modeling volumetric objects to very thin objects. Two level-set functions are employed: the first one models the location and f...

Microstructural effects become important at regions of stress concentrators such as notches, cracks and contact surfaces. A multiscale model is presented that efficiently captures microstructural details at such critical regions. The approach is based on a multiresolution mesh that includes an explicit microstructure representation at critical regions where stresses are localized. At regions fa...

Steady state crack propagation produce substantial plastic strain gradients near the tip, which are accompanied by a high density of geometrically necessary dislocations and additional local strain hardening. Here, the objective is to study these gradient effects on Mode I toughness of a homogeneous rate-sensitive metal, using a higher order plasticity theory. Throughout, emphasis is on the tou...

poor stand establishment of canola (brassica napus l.) under flatland mechanized planting and crust-forming soil is a major problem for farmers in central iran. previous research there showed that irrigated cotton emergence on crust-forming soils under flatland planting can be significantly improved using a double-disk planter with zero-pressure press wheel tires and no crust-breaking. in that ...

Fatigue crack growth can be strongly influenced by crack closure, i. e., the contacting of the opposing faces of a fatigue crack above the minimum load in a loading cycle. This crack closure shields the crack tip from the full stress field, but different views are held regarding the extent of this shielding. The type of closure, whether it be plasticity-induced, or roughness-induced may also pl...

This paper deals with the modeling of the key mechanisms involved in the fracture of polymers: shear yielding and crazing. Along with the continuum model for shear yielding, we will discuss a recently proposed cohesive surface model for crazing. Applications to be presented include the study of the competition between the two mechanisms during growth of a mode I crack, and a numerical investiga...

We propose a new two-dimensional meshing algorithm called PINW able to generate meshes that accurately approximate the distance between any two domain points by paths composed only of cell edges. This technique is based on an extension of pinwheel tilings proposed by Radin and Conway. We prove that the algorithm produces triangles of bounded aspect ratio. This kind of mesh would be useful in co...

This work presents recent progress in phase-field-based fracture modeling in heterogeneous porous media. Existing algorithms that have been developed in the last years are extended to tackle three-dimensional configurations. Our solution technique is formulated in terms of a nested Newton loop that combines a primal-dual active set method (required for treating the crack irreversibility) and a ...

1. Abstract. This paper describes some aspects of reconstruction of microstructures in three dimensions. A distinction is drawn between tomographic approaches that seek to characterize specific volumes of material, either with or without diffraction, and statistical approaches that focus on particular aspects of microstructure. A specific example of the application of the statistical approach i...