High-resolution imaging of defects in ultrasound phased arrays based on solid directivity beam multiply sum algorithm

•Detection blindness of complex components when performing ultrasonic inspection.•Introducing a solid directivity factor into conventional ultrasound imaging algorithms.•Experiments for angle blind area defects.•The proposed method can increase the phased array detection range and improve the imaging quality.•It has guiding significance for high-resolution and high-quality ultrasound imaging. As a non-destructive testing method, Ultrasonic testing plays an important role in industrial inspections. When the ultrasonic propagation in complex structures, with the propagation angle and ultrasonic phased array center angle increases, the directivity and energy of the beam will gradually weaken, which will lead to a decrease in the detection of defects as the angle increases, the formation of the detection of the angle of the blind area, known as the angle blind area. Defects cannot be effectively detected in the angle blind area, resulting in missed inspection. In order to overcome this limitation, in this paper, Solid Directivity Factor (SDF) is introduced into the traditional TFM imaging algorithm, and the SDF-weighted TFM (SDF-TFM) algorithm is constructed, which utilizes the solid directivity factor to compensate for the imaging amplitude of the defects in the angle blind area, and enhances the detection capability. Based on this, the Solid Directivity Beam Multiply Sum (SDBMS) algorithm is constructed. With the SDBMS, the signals received by each array element are cross-multiplied and summed to increase the lateral resolution and SNR of defect imaging, it effectively suppresses artifacts and background noise, achieving high-precision imaging of defects of complex structures. The experimental results show that the SDBMS algorithm improves the lateral resolution by at least 20.1%, 25.5% and 33.2% respectively compared with TFM, CDF-TFM and SDF-TFM.