The paper presents the development of an intelligent image processing algorithm capable of detecting fatigue defects from images of the rail surface. The links between the defect detection algorithm and 3D models for rail crack propagation are investigated, considering the influence of input parameters (materials, vehicle characteristics, loading conditions). The dynamic behaviour at the wheel-...

In the present paper, computations of mixed mode stress intensity factor (SIF) variations along the crack front, and fatigue-crack-growth simulations, in cracked I-beams, considering different load cases and initial crack configurations, are carried out by employing the three-dimensional SGBEM (Symmetric Galerkin Boundary Element Method)–FEM (Finite Element Method) Alternating Method. For mode-...

An infinite elastic medium with a planar crack is considered. The crack is subjected to the pressure of fluid injected at a point on the crack surface. Description of the crack growth is based on the lubrication equation (balance of the injected fluid and the crack volume), the equation for crack opening caused by fluid pressure on the crack surface, the Poiseuille equation related local fluid ...

An assessment of the plasticity-induced crack-closure concept is made, in light of some of the questions that have been raised on the validity of the concept, and the assumptions that have been made concerning crack-tip damage below the crack-opening stress. The impact of using other crack-tip parameters, such as the cyclic crack-tip displacement, to model crack-growth rate behavior was studied...

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...

In this paper, we present a new class of volumetric displays that can be used to display 3D objects. The basic approach is to trade off the spatial resolution of a digital projector (or any light engine) to gain resolution in the third dimension. Rather than projecting an image onto a 2D screen, a depth-coded image is projected onto a 3D cloud of passive optical scatterers. The 3D point cloud i...

Stage-II fatigue crack propagation in FCC metals is investigated using 3D discrete dislocation dynamics (DD) simulations. The calculations show that dislocation/grain–boundary interaction affects slip dispersion everywhere the grain, including tip region. results are analysed and drawn form of simple, quantitative mathematical expressions, depending on a set physical variables. This approach he...