Rafik Hariri philanthropic and developmental contributions are countless. The most remarkable being the multifaceted support to educate more than 36,000 Lebanese university students within Lebanon, and beyond.
You are here
THE EFFECT OF SCRATCHES ON THE FATIGUE LIFE AND FATIGUE CRACK GROWTH OF AL 2024 – T3 CLAD
Primary tabs
Nader A. NADER
|
Univ. |
Wichita State University |
Spec. |
Mechanical Engineering |
Dip. |
Year |
# Pages |
|
Ph.D. |
1993 |
149 |
The present study extends, the work done by investigators on the effect of scratches on fatigue life of aluminum alloys. This research has been expanded to include Al 2024-T3 clad, and to study the mechanism of fatigue failure considering linear elastic fracture mechanics (LEFM). Also, an investigation of the effect of scratches on cyclic stressstrain curves as well as crack nucleation and propagation in Al 2024-T3 clad was accomplished. Based on the crack data obtained, and according to previous investigators who obtained numerous models, equations were found to predict the long and short cracks behavior in scratched samples. In addition, to understand the ongoing mechanism of scratches, a thorough examination of the fracture surface and scratch surface has been made using optical and scanning electron microscopes.
An experimental study of the effect of scratches on the fatigue life and fatigue crack growth of Al 2024-T3 clad material has been conducted. The results show that Al 2024-T3 clad material is a scratch sensitive material with a drop in life as much as 95% for material with scratch depth of 100 µm. Also, it has been found that cracks propagate faster in scratched samples than unscratched and at a lower stress intensity factor. In addition, a model that predicts the fatigue crack propagation of scratched samples has been developed. Furthermore, scanning electron microscope fractographes show that scratches generated microcracks which are responsible in decreasing the fatigue life of the material.
In chapter two, a review of previous work on fatigue and fracture mechanics are presented. Chapter three deals with the experimental procedure, material specification and testing machines used in this research. In chapter four the discussion and the analysis of the results are presented. Chapter five contains both the summary and the conclusion of this work, and also includes some recommendations for future work.
