Session: Virtual Presentations in Acoustics, Vibration, and Phononics

Paper Number: 94931

94931 - Numerical Investigation of Ultrasonic Phased Array Reverse Time Migration Technique Considering Spatial Wave Characteristics 

Ultrasonic phased array technology has been extensively investigated by academia and industry as 
a powerful approach for non-destructive evaluation (NDE) purpose. The development of novel 
ultrasonic phased array probes and high-quality imaging algorithms forms the key directions of 
scientific research advancement in this regard. Numerical modeling of ultrasonic phased array can 
provide a theoretical basis for the design and manufacture of ultrasonic phased array probes. It also 
facilitates an in-depth understanding of the mechanism behind the complex wave phenomena and 
the formulation of the imaging algorithms. However, such simulation results are still very limited 
and should be strengthened. 
Based on the fundamental principle of ultrasonic phased arrays, the current study takes an aluminum 
bulk material as the research object. The ultrasonic phased array nondestructive evaluation 
procedure is numerically investigated using finite element simulations, exploring the wave 
generation, propagation, and interaction with various types of structural damage. In this study, a 
thick aluminum bulk is used as the target structure to be tested, and an ultrasonic phased array 
composed of piezoelectric materials and damping blocks is prosed as the transducers for generating 
and receiving elastic waves. Firstly, a finite element model (FEM) of a pair of transducers is 
established to study the wave generation and reception performance. In particular, the suppression 
effect of different backing material parameters (damping ratio, thickness, implementation details) 
on the piezo-elements to absorb excessive resonant vibrations is investigated, in order to send out 
and receive spatially squeezed mechanical pulses into the target medium. Then, a full-scale FEM is 
established with the complete probe set and typical structural damage types to understand the wave 
propagation and its interaction with damage. Both longitudinal (L) and shear (S) waves are studied, 
while they interact with a hole and cracks with different orientations with respect to the incident 
wave direction. Finally, the reverse time migration algorithm is further developed by considering 
the spatial wave characteristics. The amplitude variation along the propagation distance is taken into 
account to form a time/space-gain compensation function to improve the damage imaging quality 
and sensitivity, especially for far field damage sites. At the same time, the imaging algorithm is 
tested for the single L-wave, the single S-wave, and the fused LS-wave scenarios. It was found that 
the combination of L-mode and S-mode can significantly improve the damage imaging results. This 
numerical investigation may lay a solid foundation for the development of ultrasonic phased array 
technique for NDE of bulky materials. This paper ends with a summary, concluding remarks, and 
suggestions for future work. 

Presenting Author: Shulong Zhou University of Michigan-Shanghai Jiao Tong University Joint Institute

Presenting Author Biography: PhD student in mechanical engineering, UM-SJTU Joint Institute, Shanghai Jiao Tong University, 2021.9-present<br/>B.S. in mechanical and electrical engineering, Shandong University, 2017.9-2021.6

Authors:

Shulong Zhou University of Michigan-Shanghai Jiao Tong University Joint Institute
Yanfeng Shen University of Michigan-Shanghai Jiao Tong University Joint Institute