Structural damage detection using Hilbert-Huang Transform and instantaneous signal phase

Document Type : full paper

Authors

• Mansour Azami ¹
• Mehdi Salehi ²

¹ MSc student, Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran

² Assistant Professor, Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran.

Abstract

This paper examines the damage detection in structures using the Hilbert Huang transform. Instantaneous phase changes are considered as the characteristic parameter for determining structural damage. In this research, the free vibration response of the structure was used to determine the structural damage. First, the governing relationships are presented to calculate the instantaneous variations of the phase angle of each of the EMD decomposition modes. The proposed method is implemented on a defective cantilever beam. By breaking down the structural response into some IMFs through EMD, two sets of intrinsic modes are calculated for intact and damaged states. Then, by using Hilbert transformation, the instantaneous phase changes of the first intrinsic modes are calculated and, based on that, the damage detection is fulfilled using the proposed relationships. In order to evaluate the effectiveness of this method in real-world conditions, modal test was performed on a beam in intact and damaged states. The system impulse response functions are calculated by applying the inverse Fourier transformation on the frequency response functions of the test. The method is implemented on the attained impulse responses. The results are satisfactory both for the numerical model and for the experimental results.

Keywords

• Structural damage
• Hilbert-Huang
• EMD
• signal phase

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