Finite Element Analysis of a Fuselage Crack
13/09/2009
Analysis Of A Fuselage Crack
Anoop Retheesh
Fracture Mechanics and Fatigue
CONTENTS
Title Page Contents Abstract List of Figures List of Tables
i ii iii iv iv
1. Analysis of a Fuselage Crack
1.1 Introduction 1.2 State of Stress in the absence of the Crack 1.3 Geometrical Stress Intensity Factor at the Crack Tip 1.4 Fracture Analysis using Finite Element Methods 1.4.1 Finite Element Model of the Fuselage Crack 1.4.2 The Solution 1.4.3 Grid Independence Study 1.5 Variation in Stress Intensity Factor with Crack Length 1.5.1 Conclusion
1
1 2 3 5 5 8 9 10 12
2. References
13
Analysis of a Fuselage Crack
ii
Fracture Mechanics and Fatigue
ABSTRACT
Fracture & Fatigue are the most common engineering concerns that limit the useful life of mechanical components. In fact, it was estimated that the occurrence or prevention of fatigue failures costs the US economy about 3% of its gross national product (R P Reed, J H Smith, B W Christ; 1983). The term ‘fatigue’ represents the permanent structural changes occurring in a material subjected to fluctuating stresses that builds up cracks in it and leads to its complete fracture after a sufficient number of fluctuations (ASTM E-1150; 1987). Fracture mechanics, meanwhile deals with the microscopic aspects of fracture and the failure of metals due to fracture. During the past 50 years, the subject has evolved a lot and it helped in understanding and predicting not only fracture failure but also crack growth processes such as fatigue. Fracture mechanics, combined with the conventional fatigue design modals now became an integral part of mechanical engineering design. In this report, an analysis is carried out on the cracks developed on an aircraft fuselage skin using Linear Elastic Fracture Mechanics (LEFM) assumptions. The cracks, emanating from each side of the circular rivet holes in the fuselage is assumed to be in a state of stress equivalent to a wide thin plate subjected to
Analysis Of A Fuselage Crack
Anoop Retheesh
Fracture Mechanics and Fatigue
CONTENTS
Title Page Contents Abstract List of Figures List of Tables
i ii iii iv iv
1. Analysis of a Fuselage Crack
1.1 Introduction 1.2 State of Stress in the absence of the Crack 1.3 Geometrical Stress Intensity Factor at the Crack Tip 1.4 Fracture Analysis using Finite Element Methods 1.4.1 Finite Element Model of the Fuselage Crack 1.4.2 The Solution 1.4.3 Grid Independence Study 1.5 Variation in Stress Intensity Factor with Crack Length 1.5.1 Conclusion
1
1 2 3 5 5 8 9 10 12
2. References
13
Analysis of a Fuselage Crack
ii
Fracture Mechanics and Fatigue
ABSTRACT
Fracture & Fatigue are the most common engineering concerns that limit the useful life of mechanical components. In fact, it was estimated that the occurrence or prevention of fatigue failures costs the US economy about 3% of its gross national product (R P Reed, J H Smith, B W Christ; 1983). The term ‘fatigue’ represents the permanent structural changes occurring in a material subjected to fluctuating stresses that builds up cracks in it and leads to its complete fracture after a sufficient number of fluctuations (ASTM E-1150; 1987). Fracture mechanics, meanwhile deals with the microscopic aspects of fracture and the failure of metals due to fracture. During the past 50 years, the subject has evolved a lot and it helped in understanding and predicting not only fracture failure but also crack growth processes such as fatigue. Fracture mechanics, combined with the conventional fatigue design modals now became an integral part of mechanical engineering design. In this report, an analysis is carried out on the cracks developed on an aircraft fuselage skin using Linear Elastic Fracture Mechanics (LEFM) assumptions. The cracks, emanating from each side of the circular rivet holes in the fuselage is assumed to be in a state of stress equivalent to a wide thin plate subjected to