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Experimental and numerical analyses of mixed mode crack initiation angle

Al Bin Mousa, Jafar Husain (2006) Experimental and numerical analyses of mixed mode crack initiation angle. Masters thesis, King Fahd University of Petroleum and Minerals.

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In fracture mechanics, one of the key factors in predicting crack propagation path is the value of the crack initiation angle. It is well known that crack propagation phenomenon is highly dependent on the state of stress in the vicinity of the crack tip, therefore, stress intensity factor 'SIF' is considered as the most significant parameter in predicting the crack propagation path. The knowledge of the crack initiation angle is an important issue in arresting the crack. In addition, SIF completely characterizes the crack tip stress condition in linear elastic material. Photoelastic technique is one of the common experimental methods used to determine the SIF for either pure or mixed mode fracture. The angle of crack initiation is inferred from fringe patterns using methods such as Schroedl and Smith and Sanford and Dally for the case of pure opening mode and mixed mode fractures, respectively. Numerical analyses are also used to describe the state of stress at crack tip and calculate SIF's from which angle of crack initiation is found. Beside analytical methods, experim,ental and numerical methods can be used either separately or in combination to find the crack initiation angle. The main objective of this study is to predict the crack initiation angle for mixed mode fracture using both photoelasticity and numerical techniques. The FE code "ANSYS" is used to estimate the SIF numerically. The estimated value of the SIF is going to be incorporated into crack initiation criteria to predict the crack initiation angle. Six criteria were considered in this analysis and these are the maximum tangential stress (MTS) criterion, the minimum strain energy density (S) criterion, the maximum dilatational strain (T) criterion, the maximum triaxial stress (M) criterion, the modified MTS criterion (M.MTS) and the ® criterion. A polycarbonate sheet of 3mm thickness was used for manufacturing single edge crack specimens. All specimens have the same crack length but different angles of inclination name, 0°, 10°, 20°, 30° and 40°. In the experimental analysis, the specimens were loaded until the crack initiated and the angle is measured to validate both techniques. A new model based on numerical results is proposed for estimating the geometric correction factor Y for an inclined edge crack panel.



Item Type:Thesis (Masters)
Date:June 2006
Date Type:Completion
Subjects:Mechanical
Divisions:College Of Engineering Sciences > Mechanical Engineering Dept
Creators:Al Bin Mousa, Jafar Husain
Committee Advisor:Merah, Nesar
Committee Members:Arif, Abul Fazal Mohammad and Eleiche, Abdel Salam
ID Code:9727
Deposited By:KFUPM ePrints Admin
Deposited On:22 Jun 2008 16:47
Last Modified:25 Apr 2011 09:19

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