Experimental stress intensity factors of cracks in lugs

• Main Author: Low, Kin Whye
• Other Authors: Chai Gin Boay
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/68663
• Institution: Nanyang Technological University

The use of lug connectors is widespread in modern aircraft design. As such, they are extremely important components as they connect the major structural components of an aircraft. Failure of a connector due to fatigue can lead to disastrous consequences. Hence it is important to be able to predict the life of a lug connector. In this project, lug shaped specimens with pre-made cracks were fabricated and subjected to fatigue testing to simulate the life cycle of a typical aircraft attachment lug. A tensile test was first conducted to determine an appropriate load for the fatigue test, so as to prevent premature failure before results were obtained. After the fatigue test, post-mortem fractography was conducted on the fracture surface. The loading sequence used for the fatigue test would have produced striation lines on the fracture surface which could then be analysed. The striation lines provide an important way to determine the crack propagation rate. The stress intensity factor could be calculated using the crack propagation rate and the geometry factor. With the crack propagation rate, number of cycles to failure and stress intensity factor known, the life cycle of a lug with similar crack configuration can be predicted.