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Crack Detection on Asphalt Concrete Pavements Using Image Processing
,
M.Sc. Thesis
Sharif University of Technology
;
Sabouri, Mohammad Reza
(Supervisor)
Abstract
Road transportation has long been an important form of transportation for mankind. Mass production of motorized vehicles and a growing number of people using human and goods transportation have led engineers to monitor road pavement condition and to act on accordingly in the case of degradation. Due to road networks expansion and budget restrictions, road pavement maintenance and rehabilitation projects should be prioritized based on up-to-date data. Automatic collection of data related to the pavement condition such as the number and the length of cracks, could save time and reduce cost and workforce. This research proposes a hybrid method composed of two independent techniques for...
Buckling of cracked cylindrical thin shells under combined internal pressure and axial compression
, Article Thin-Walled Structures ; Volume 44, Issue 2 , 2006 , Pages 141-151 ; 02638231 (ISSN) ; Estekanchi, H. E ; Sharif University of Technology
2006
Abstract
Linear eigenvalue analysis of cracked cylindrical shells under combined internal pressure and axial compression is carried out to study the effect of crack type, size and orientation on the buckling behavior of cylindrical thin shells. Two types of crack are considered; through crack and thumbnail crack. Our calculations indicate that depending on the crack type, length, orientation and the internal pressure, local buckling may precede the global buckling of the cylindrical shell. The internal pressure, in general, increases the buckling load associated with the global buckling mode of the cylindrical shells. In contrast, the effect of internal pressure on buckling loads associated with the...
Arc Length Method for Extracting Crack Pattern Characteristics
, M.Sc. Thesis Sharif University of Technology ; Mohtasham Dolatshahi, Kiarash (Supervisor)
Abstract
Although manual crack inspection has been widely used for structural health monitoring over the last decades, the development of computer vision methods allows continuous monitoring and compensates the human judgment inaccuracy. In this study, an image-based method entitled, Arc Length method is introduced for extracting crack pattern characteristics, including crack width, and crack length. The method contains two major steps; in the first step, the crack zones are estimated in the whole image. Afterwards, the algorithm finds the start point, follows the crack pattern, and measures the crack features, such as crack width, crack length, and crack pattern angle. The efficiency of the method...
The finite element simulation of lamb wave propagation in a cracked structure with coupled filed elements
, Article Advanced Materials Research, 7 January 2012 through 8 January 2012 ; Volume 463-464 , January , 2012 , Pages 618-623 ; 10226680 (ISSN) ; 9783037853634 (ISBN) ; Abedian, A ; Khajehtourian, R ; Singapore Institute of Electronics (SIE); Science and Engineering Institute (SCIEI) ; Sharif University of Technology
2012
Abstract
Crack detection by Piezoelectric Wafer Active Sensors (PWAS) is one of the emerging methods of Non-destructive Evaluation (NDE). These sensors can assess the health state of the structure in far filed through the analyzing the high frequency Lamb wave propagation. As PWAS is the essential part of this method, simulation and modeling of these sensors and their interaction with the host structure, strongly affect the accuracy of results. In this study, unlike the previous works, in which some certain areas of the host structure were considered as a sensor and actuator, the direct simulation of electro-mechanical interaction of the PWAS and the host structure is modeled among modeling the PWAS...
Numerical investigation of crack orientation in the fretting fatigue of a flat rounded contact
, Article International Journal of Engineering, Transactions B: Applications ; Volume 23, Issue 3-4 , 2010 , Pages 223-232 ; 1728-144X (ISSN) ; Farrahi, G. H ; Sharif University of Technology
Materials and Energy Research Center
2010
Abstract
The growth of slant cracks by fretting fatigue of a half plane in contact with a flat rounded pad was studied. The mode I and mode II stress intensity factors for cracks of various lengths and directions were calculated using the semi-analytical method of the distribution of dislocations, and their cumulative effect on the crack growth was investigated using the strain energy density criterion. The results showed dominance of mode I fracture on crack growth, and based on the observation of strain energy density factor versus crack orientation, the results also suggest that depending on the crack length, the most critical orientations of cracks are at 0° to 20° outward the contact zone. Good...
Modeling of dynamic cohesive fracture propagation in porous saturated media
, Article International Journal for Numerical and Analytical Methods in Geomechanics ; Volume 35, Issue 10 , 2011 , Pages 1160-1184 ; 03639061 (ISSN) ; Barani, O. R ; Mofid, M ; Sharif University of Technology
2011
Abstract
In this paper, a mathematical model is presented for the analysis of dynamic fracture propagation in the saturated porous media. The solid behavior incorporates a discrete cohesive fracture model, coupled with the flow in porous media through the fracture network. The double-nodded zero-thickness cohesive interface element is employed for the mixed mode fracture behavior in tension and contact behavior in compression. The crack is automatically detected and propagated perpendicular to the maximum effective stress. The spatial discretization is continuously updated during the crack propagation. Numerical examples from the hydraulic fracturing test and the concrete gravity dam show the...