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# ES 240 Project Proposal - Jane Yoon, Sun Min Jung

**Stress/Strain ****Analysis of ****Bullet-Holes****on**** ****the Boeing 737 Fuselage**** **Boeing 737 is the most popular aircraft in the sky today, with each one taking off or landing on average of every 6 seconds. One of the most important analyses conducted on these passenger aircrafts is determining the impact of any damage on the fuselage. In order to conduct such analysis, several advanced computational modeling techniques are used to simulate the effects and thus fix them to prevent any disasters. What most people, including Boeing engineers, may not be able to foresee, is that prior to the assembly of the Boeing 737 aircrafts, the fuselage sometimes suffers an unusual structural damage during transportation. More specifically, while the fuselage is being relocated on a train from Wichita, Kansas (where the fuselage is manufactured) to Renton, Washington (where parts are assembled), several bullet holes are found occasionally throughout the large fuselage structures. These damages are due to civilians practicing shooting skills at the moving fuselages during transportation. These structural damages cause residual stress and strain fields that need to be addressed in order to repair these structures. This project aims to apply continuum mechanics as well as finite element analysis (FEA) via the program ABAQUS to model the damage that bullet-holes cause to the fuselage, and to analyze the resulting stress and strains caused by these deformations. We will look at 4 particular cases: 1. stress/strain caused by a single bullet hole2. stress/strain caused by two bullet holes at a finite distance apart3. stress/strain caused by a single bullet hole near a window4. stress/strain caused by two bullet holes at a finite distance apart near a window In addition to these analyses, we will attempt to also determine how the distance between the centers of the two bullet holes affects the stress and strain relationship; in other words, we will try to analyze the case where two bullet holes overlap. In order to begin stress/strain analysis on the damaged fuselage, we will first mathematically compute the residual stress and strain fields caused by simplified models, such as the Lamé problem for cylindrical shapes. We will then make more complicated models to analyze the more intricate situation of the two bullet holes placed in proximity to one another, and the case of the two bullet holes overlapping. Based on these mathematical models, we will then use ABAQUS to determine how similar the theoretical expressions and values are to the FEA simulated ones. For this project, we will attempt to simulate all the properties of a Boeing 737 fuselage to model our system. Since most of the information is Boeing Property and not available to us, we will research to find similar material constants that make up the fuselage. This is an actual real-life problem faced by Boeing engineers, and we will use as much information as possible to make sure our analyses follow as closely to the specifications of the actual Boeing 737 fuselage.

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