To address the issue of signal attenuation caused by geometric shadowing effects in PAUT of internal porosity defects in pressure vessel mitered pipe weld zone. In this paper, by constructing a structural geometry tensor angle-acoustic beam propagation attenuation model, combined with a sound range compensation algorithm. The propagation characteristics of ultrasonic waves and defect detection effects under four sample bend angles of 45°, 60°, 90° and 135° are systematically investigated. The study employed an FDTD algorithm to establish a dynamic response simulation model of the mitered pipe weld and validated the findings through experiments using aluminum alloy specimens with pre-drilled defects. The results indicate that the signal amplitude of the 45° defect increased from 50.4 to 97.4, and the SNR improved from 6.27 dB to 11.99 dB. Similarly, for the 60° defect, the signal amplitude increased from 77.5 to 97.5, and the SNR improved from 9.00 dB to 12.00 dB. The calculated deviation in SNR was less than 1.5 dB, and the defect detection rate increased by 23%. The study confirmed that the occlusion effect caused by the bend angle significantly affects the sound beam propagation path and signal amplitude. The proposed model and correction algorithm can effectively compensate for detection errors in non-standard structures, providing a quantitative theoretical basis for optimizing ultrasonic testing procedures for the pressure vessel weld zone.