Calculation Of Radiation Beam Field From Phased Array Transducer With A Multi-gaussian Beam Model Based On Fraunhofer Approximation

Nowadays, ultrasonic phased array is widely used in nondestructive testing. Simulation of beam field plays a great role in products development and testing. However, the Rayleigh integral costs much time in calculation and the paraxial multi-Gaussian beam model(MG) can’t obtain the precise solution in off-axis beam fields. When faced an irregular surface and complex interface, the phased array simulation may not obtain perfect results. The resea rches in this paper will try to address the above mentioned problems.A multi-Gaussian beam model based on Fraunhofer approximation(FMG) for the rectangular aperture is proposed in this paper to improve calculation speed and address the issue of MG which can’t obtain the precise solution in off-axis beam fields. The nonparaxial multi-Gaussian beam model(NMG), MG and the proposed model are together used for calculating and comparing with the respective beam field of a linear phased array transducer. Simul ation results show that the proposed model can overcome the inaccuracy problem of MG in off-axis beam fields just like NMG does. However, the proposed model runs faster than NMG and it takes about 4/5 time of the latter. In addition, focusing effect of this proposed model is better than the other two methods, which means that the proposed model is more applicable to stimulate the beam field of linear phased array. By changing deflecting angles, focusing distances and materials, all of the three methods are used for testing the defect echo in this paper. Simulation results show that echoes of FMG and NMG are stronger than MG.Flexible phased array is used for irregular surface testing. MG, NMG and FMG are used for calculating the beam field of flexible phased array. Simulation results show that all of the three methods can be used for flexible phased array calculation, while FMG or NMG is better than MG method.An acrylic-water-steel interface is studied for the irregular interface of multi-layer media testing in the paper. Radiation calculation results of different steering angles are obtained for the acrylic-water-steel interface testing. Results show that irregular interfaces beam field simulation can be perfectly obtained by the MG method of multi-layer media.