3D Hybrid Modeling for the Ultrasonic Phased Array Inspection of Porosity in Heavy Plates: Simulation and Experimental Validation

Quantitative non-destructive testing (NDT) modelling and simulation tools are important in design and fabrication of ultrasonic phased array (UTPA) sensors with optimum characteristics and reduce the number of experimental efforts and development time. In order to achieve high accuracy with a low computational time in the simulation, the modeling tools require not only the high-frequency approximation of the ultrasonic wave propagation but also the high-precision electro-acoustic coupling model. In this work, an application specific 4 MHz, 32-element linear phased array probe with an optimized angle beam wedge for the inspection of porosity in heavy plates was developed based on the new 3D hybrid modeling approach. As a first step, we performed the FEA modeling of an UTPA sensor, which includes the full 1-3 piezo-composite design with the arrangement of array elements, conducting electrodes, multi-phase damping material, acoustical matching layer and the electrical circuit of a 50 Ω coaxial cable. In addition, the real excitation pulse of an industrial UT equipment was included in the current modelling to achieve the high accuracy in the simulated result. In the second step, the FEA simulated pulse-echo characteristics of an array element were further used as the reference signal in the CIVA-UT Software to simulate the imaging of porosity in heavy plates, quantitatively. Furthermore, the 3D wedge-geometry of the array sensor was modeled and optimized to suppress the unwanted wedge-boundary reflected echoes and to improve the signal-to-noise ratio (SNR) in the detected signals. The 3D hybrid model simulated Time Corrected Gain (TCG) curves for the 3 mm SDH at different depths in the reference steel plate were compared with the real experiments and a good quantitative agreement was achieved.