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Resonant activation of different intermodulation frequencies using dual excitations
N S V N Hanuman1, Subhankar Roy1, Tanmoy Bose1
1Department of Mechanical Engineering, National Institute of Technology Meghalaya, Shillong 793003, India.
Ultrasonics
|April 6, 2020
Summary
This study presents an analytical framework to understand intermodulation frequencies in composite plates with delaminations. The research reveals distinct intermodulation peaks (LDRI and SPFI) generated by specific excitation types, offering insights into defect detection.
Area of Science:
- Mechanical Engineering
- Materials Science
- Nonlinear Dynamics
Background:
- Composite materials like GFRP are susceptible to delaminations, which can affect structural integrity.
- Nonlinear phenomena, such as intermodulation distortion, can arise from defects under dynamic loading.
- Understanding these nonlinear responses is crucial for effective structural health monitoring.
Purpose of the Study:
- To develop an analytical framework for predicting intermodulation frequencies in composite plates with delaminations.
- To investigate the generation mechanisms of different intermodulation frequencies under dual excitation.
- To experimentally validate the analytical model using GFRP plates.
Main Methods:
- Analytical derivation of flexural wave propagation in orthotropic composite plates with quadratic nonlinearity.
- Application of dual excitation: a single periodic frequency (SPF) and a variable frequency (local defect resonance (LDR) frequency, its superharmonics, and subharmonics).
- Experimental verification using glass fibre reinforced plastic (GFRP) plates with single and double delaminations.
Main Results:
- Two types of intermodulation peaks were identified: local defect resonance intermodulation (LDRI) and single periodic frequency intermodulation (SPFI).
- SPFI generation was observed exclusively during superharmonic and subharmonic excitation.
- At LDR frequency excitation, only higher harmonics were detected, with no SPFI peaks.
- Acoustic nonlinearity parameters increased with the order of harmonics and delamination diameter.
Conclusions:
- The analytical framework accurately predicts intermodulation frequencies in delaminated composite plates.
- The study differentiates the generation mechanisms of LDRI and SPFI peaks based on excitation conditions.
- Findings contribute to enhanced non-destructive testing techniques for composite structures by correlating nonlinear acoustic responses with defect characteristics.
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