Defect resonance frequency of spherical pore within isotropic elastic solid
1Department of Mechanical Engineering, National Institute of Technology Meghalaya, Shillong 793003, India.
Abstract:
Ultrasound based porosity imaging in metals, composite or additive manufactured structures pose a challenge due to various absorbing media. This paper addresses this problem by developing a defect resonance frequency equation that will be used for individual porosity imaging. An analytical model is developed for closed spherical shell supported on elastic foundation based on the six mode shell theory. The defect resonance frequency is calculated from the breathing mode, corresponding to maximum out-of-plane displacement, when supporting stiffness tending towards rigid condition. Thereafter, steady state and explicit dynamic analysis are carried out for a mild steel specimen with single and multiple pores to detect the defect resonance frequency along with defect mode. Further, the defect resonance frequency is validated with experiment involving a mild steel specimen with single spherical pore. The numerical and experimental results are good agreement with the results obtained from defect resonance frequency equation. This defect resonance frequency equation can be used for high resolution imaging of porosities.
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