الفهرس 
CHAPTER (1) IntroductionOnly 14 pages are availabe for public view
 |  | from | 101 |  |  |
| | | from | 101 | | |
Abstract
Damage in engineering structures has been of concern to the engineering community for many years. The ability to detect and monitor damage using non-destructive testing in structures and mechanical components becomes very important. Many damage identification
techniques have been proposed relying on vibration testing. Vibration-based damage identification techniques rely on the fact that existence of a localized damage in a structure
affects the global structural dynamic behavior. In the literature, one of the promising techniques rely on combining a finite element model of the undamaged structure with a set of
experimentally-measured frequency response functions (FRF) of the structure under investigation to construct a so-called Damage Location Vector (DLV). This paper aims to
assess both theoretically and experimentally damage detection using DLVs. Firstly The method is studied theoretically on a composite plate using simulated damage. Then, it is tested experimentally using free- free and fixed-free boundary condition for a plate with middle damage using shaker test. The method is improved through the use of FRFs of the undamaged structure obtained both numerically and experimentally in an attempt to overcome difficulties
imposed by initial damage and noise. Finally, a case study has been done to assess the DLV technique on composite plates. The main results and conclusions are:
1- The DLV method could detect damage location successfully both theoretically and experimentally.
2- The DLV can identify single cracks damage locations.
3- Damage identification based on DLV can accurately determine the extent of the damage from natural frequency and mode vector line drive.
4- Frequency response function (FRF) of the intact structure obtained numerically and experimentally, the DLV method could overcome difficulties imposed by initial damage and noise to detect and localize the damage experimentally.
5- The position of nodes and antinodes are shifted for cracked composite plates compared with plain ones.