Development and comparative evaluation of a new structural modification method in application to aircraft structures

Thesis Type: Postgraduate

Institution Of The Thesis: Middle East Technical University, Faculty of Engineering, Department of Mechanical Engineering, Turkey

Approval Date: 2006

Thesis Language: English

Student: Sertaç Köksal



In the development of engineering products, it is necessary to predict dynamic properties of the modified structures. Achieving such predictions by using the structural properties of the original structure and information on the modifications is commonly referred to as structural modification analysis. In this thesis, Özgüven’s Structural Modification Method and Sherman-Morrison Method are selected as exact methods for structural modifications to predict the dynamics of a locally modified structure. Also, a new structural modification method named as “Extended Successive Matrix Inversion Method” is developed in this study. These three methods are implemented in a software developed herein, called “Structural Modification Toolbox”. The software uses modal analysis results of MSC Nastran© for the original structure and calculates the modified frequency response functions by any of the methods above. In order to validate the software, direct modal analysis results of MSC Nastran© for the frequency response functions of the modified structure are used. The methods are compared in terms of computational time, and the effectivity of each method is studied as a function of modification size to determine which of these methods is more suitable. In order to investigate the application of the methods and compare their results with experimental ones, modal tests are conducted on a scaled aircraft structure. The solutions are compared with test results obtained from modified test structure. Additionally, the software is used for comparison of real aircraft test results and frequency response functions of the modified structure.