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Structural Health Monitoring of Beam with Symmetric Discontinuity Using Ultrasonic Guided Wave Propagation

Ghadami, Amin | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44499 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Behzad, Mehdi; Mirdamadi, Hamid Reza
  7. Abstract:
  8. Damage identification in uniform structures using Lamb waves has been studied by the researchers; however, as most of the industrial structures are not uniform, it is necessary to study more complex structures. In this thesis, a method of identifying notch specifications as damage in a symmetric stepped beam with arbitrary number of steps using Lamb wave propagation is presented. Initially, the study will examine and compare the Lamb wave propagation in uniform, symmetric stepped and asymmetric stepped beams. In the first stage, a method for detection of damage location in symmetric stepped beam is presented. This method is based on mode conversion phenomenon of Lamb wave modes. Moreover, this method is based on pitch-catch method as it is investigated that using pulse-echo method in our problem and also similar problems makes difficulty in signal processing. In the next step, a method is presented in order to identifying notch dimensions in the beam. The basis of this method is similar to the previous one and the results of damage localization will be used in this section, too. The power reduction of Lamb waves because of interaction with the existing damage is used in the presented method. Therefore, the power transmission and reflection coefficients of Lamb wave modes scattered by various types of notches is computed using both theatrical formulation and finite element method.
    Finally, in order to investigate the efficiency of presented methods, some examples are modeled in the ABAQUS® software and the notch specifications are identified using the methods. The results show that our methods can successfully identify all of the notch specifications, i.e. its location, depth and width
  9. Keywords:
  10. Damage Detection ; Lamb Wave ; Wave Propagation ; Symmetric Stepped Beam ; Lamb Wave Power ; Mode Conversion Phenomenon

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