Search results for "Crack"
showing 10 items of 209 documents
Automation of Optimized Gabor Filter Parameter Selection for Road Cracks Detection
2016
International audience; Automated systems for road crack detection are extremely important in road maintenance for vehicle safety and traveler's comfort. Emerging cracks in roads need to be detected and accordingly repaired as early as possible to avoid further damage thus reducing rehabilitation cost. In this paper, a robust method for Gabor filter parameters optimization for automatic road crack detection is discussed. Gabor filter has been used in previous literature for similar applications. However, there is a need for automatic selection of optimized Gabor filter parameters due to variation in texture of roads and cracks. The problem of change of background, which in fact is road text…
Application of the 3-D boundary element method to delaminated composite structures
2013
A three-dimensional boundary element model for anisotropic solids is presented to study the fracture mechanics behavior of delaminated composite structures. The multi-domain technique is implemented to model the layered configurations and the cracks occurring at bi-material interface. The Modified Crack Closure Integral technique is implemented to characterize the fracture mechanics behavior of delaminations in terms of the total energy release rate and mode mix phase angles. Validating analyses, performed on different delaminated configurations, have shown the effectiveness of the proposed approach. Moreover, some original results are presented to investigate the effects of the stacking se…
The mechanically-based approach to 3D non-local linear elasticity theory: Long-range central interactions
2010
Abstract This paper presents the generalization to a three-dimensional (3D) case of a mechanically-based approach to non-local elasticity theory, recently proposed by the authors in a one-dimensional (1D) case. The proposed model assumes that the equilibrium of a volume element is attained by contact forces between adjacent elements and by long-range forces exerted by non-adjacent elements. Specifically, the long-range forces are modelled as central body forces depending on the relative displacement between the centroids of the volume elements, measured along the line connecting the centroids. Further, the long-range forces are assumed to be proportional to a proper, material-dependent, dis…
3D boundary element analysis of delamination crack using the Modified Crack Closure Integral
2012
Structural Health Monitoring of delaminated composite structures by the Boundary Element method
2012
Structural Health Monitoring (SHM) for composite materials is becoming a primary task due to their extended use in safety critical applications. Different methods, based on the use of piezoelectric transducers, strain memory alloys as well as of fibre optics, has been successfully proposed to detect and monitor damage in composite structural components with particular attention focused on delamination cracks. In the present paper a Structural Health Monitoring model based on the use of piezoelectric sensors, already proposed by the authors for isotropic damaged components, is extended to delaminated composite structures. The dynamic behavior of the host damaged structure and the bonded piez…
Buckling and post-buckling analysis of cracked composite plates via a single-domain Ritz approach
2018
Thin and moderately thick composite multi-layered plates are widely employed in many engineering applications, especially in naval and aerospace structures. These structural components can experience in service the presence of cracks, generated for example by corrosion, fatigue or accidental external causes. Cracks can affect the load carrying capability, buckling and post-buckling behaviour of plates; therefore, their effects need to be investigated and taken into account for fail safe or damage tolerant design. Additionally, attention should be devoted to the interaction of cracks with buckling and post-buckling behaviour, as the energy release rate in post-buckling regimes can be adverse…
Simplified technique for constitutive analysis of SFRC
2014
Steel fibre reinforced concrete (SFRC) has become widespread material in areas such as underground shotcrete structures and industrial floors. However, due to the absence of material models of SFRC reliable for numerical analysis, application fields of this material are still limited. Due to interaction of concrete with fibres, a cracked section is able to carry a significant portion of tensile stresses, called the residual stresses. In present practices, residual stresses used for strength, deflection and crack width analysis are quantified by means of standard tests. However, interpretation of these test results is based on approximation using empirically deduced relationships, adequacy o…
A kinetic study of the cracking, isomerization, and disproportionation of n-heptane on a chromium-exchanged Y zeolite
1982
The kinetic rate constants for the cracking, isomerization, and disproportionation of n-heptane over a CrHNaY (32% chromium exchanged) zeolite catalyst at 400, 450, and 470 °C have been calculated. The interaction of n-heptane with a model Lewis acid such as BF3 and progress along the reaction coordinate have been studied by means of molecular orbital calculations. From the kinetic results, i.e., activation energies and frequency factors, and the theoretical calculations, it can be concluded that the controlling step in these reactions is not the formation of the carbonium ion, but the subsequent transformation of this carbonium ion. In addition, the theoretical calculations show that the a…
Current views on the mechanism of catalytic cracking
2000
Abstract The cracking mechanisms of hydrocarbons have been reviewed and the kinetic and thermodynamic implications of the different steps, i.e. initiation, chain propagation, and termination, have been discussed. Although the cracking mechanism of olefins and alkylaromatics is well established, the initiation step for the cracking of paraffins is still under debate. The role of Bronsted-type active sites and also the possible influence of extra-framework Al species in the case of zeolite catalysts, especially when commercial feeds and industrial conditions are employed, are presented. The product distribution is determined by the number of propagation events occurring per initiation step, a…