Acoustic emission

About: Acoustic emission is a research topic. Over the lifetime, 16293 publications have been published within this topic receiving 211456 citations.

Onset of free-edge delamination in composite laminates under tensile loading

Abstract: Edge delamination onset on composite laminates has been investigated for a carbon/epoxy T800/914 composite material. On the edge of laminates, out-of-plane stresses arise, even up to material's failure. Layer thickness is also known as well to influence delamination onset stress. Making use of a conventional model (that is to say assuming plies homogeneity, elastic linear behaviour, plane interlaminar surface and interface's infinite stiffness) and of a local stress tensor correction near the edge, allows, thanks to an asymptotic method, an efficient calculation of the full stress tensor. A stress criterion has then been studied. Criterion parameters assessment, from test results, has been focused on, based on conjugate gradient method and experimental thickness effect. Edge Delamination Tests have been performed on several specimens of various layups. Interlaminar shear, tension, as well as shear and tension combination have been investigated. Acoustic emission was used to detect delamination onset. As expected, these tests have exhibited layer thickness influence on onset stress. Shear parameter assessment shows good agreement between theory and experimental results. A single set of parameters is necessary to predict delamination for different layups. But experimental testing for both tensile and mixed mode has shown that failure may not be interlaminar, as expected, but intralaminar.

Rational-Dilation Wavelet Transform Based Torque Estimation from Acoustic Signals for Fault Diagnosis in a Three-Phase Induction Motor

Abstract: Condition monitoring of electric drives play a significant role for a safe working environment. Induction motors are widely used in industries and any fault in it leads to interruption in the process or complete shutdown of the equipment. In this paper, acoustic-based fault detection in a three-phase induction motor is done by estimating the torque from the acoustic signals released by the machine. The fault detection is possible as acoustic emission is different for faults such as single phasing, bearing cage damage, and broken rotor bars. The acoustic signals are processed using rational-dilation wavelet transform (RADWT) technique to extract the fault features and thereby diagnose the fault type. The torque estimation is done using multiple regression method by extracting the energy possessed in the processed acoustic signal and the faults are diagnosed precisely. An experimental setup comprising of a three-phase induction motor with brake drum loading is used to validate this approach. The RADWT has adjustable frequency resolution in comparison with other wavelet methods. When high Q-factor filters are employed in the RADWT, better representation of different faults are obtained in the decomposed sub-bands. In addition, characteristic frequencies of different faults are calculated analytically and validated by observing the frequencies in the FFT spectrum of acoustic fault signals.