Final answer:
Performing sectorial scans from multiple positions during phased array weld inspections is critical for detecting discontinuities. Calibration is necessary for accuracy in results, and reference level sensitivity calibrations can be used with blocks compatible with both phased array and manual ultrasonic testing procedures.option a is correct.
Step-by-step explanation:
When performing weld inspections with phased array testing, it is a standard industry practice to perform sectorial scans from at least two index positions to detect discontinuities. This technique helps identify defects that may not be visible from a single scan position due to the orientation of the cracks or other anomalies. It is true that ultrasound reflections from changes in density can reveal defects such as cracks and voids in solids which are crucial for the integrity of structures like aircraft wings.
Calibration is an essential part of phased array testing and needs to be conducted to ensure accuracy; it is incorrect to assume that calibration is not required. Calibration ensures that the sensitivity and accuracy are maintained, and the stored data reflects the true condition of the welds. Reference level sensitivity calibrations can indeed be performed on blocks used for manual ultrasonic testing, provided they meet the requirements for the phased array test procedure. The goal of calibration is to ensure the equipment is correctly interpreting the reflected sound waves, which are strongest where there are the greatest density changes.