Abstract

Ultrasonic imaging is widely preferred in the field of non-destructive evaluation, medical diagnostics, and underwater inspection because it offers various advantages such as safety and versatility. However, conventional ultrasonic imaging methods suffer from the poor resolution limit imposed by the loss of information on fine features within the near-field. Metamaterial concepts have attracted much research interest in recent years, yielding extraordinary benefits such as super-resolution imaging, vibration damping, and cloaking. In the context of imaging, Metalenses allow the successful transfer of the information carried by the evanescent waves to far-field by amplifying them and hence help in overcoming the resolution limit. Hyperlenses enable subwavelength resolution along with spatial magnification by transforming evanescent waves scattered past a material artifact into propagating waves at the far-field ‘imaging’ end of the medium. This paper discusses novel radially symmetric ultrasonic hyperlens for imaging defects in the context of non-destructive evaluation, a topic that has not been studied much. The effect of parameters such as defect extent and distance between the lens on the subwavelength imaging of the hyperlens is studied using numerical simulations. This study investigates the magnification achievable using the proposed hyperlens and the effectiveness of this approach for nondestructive evaluation using cost-effective ‘everyday’ transducers.

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