Gapless calibration method for phased array ultrasonic inspection

A method of calibrating a phased array ultrasound inspection system, the method comprising a normalization step and a calibration step;

• wherein the normalization step comprises:
• performing a normalization scan to acquire normalization scan data with at least one phased array probe sonically coupled to a calibration object having an axis with an axial direction, the calibration object having a plurality of flaws, each flaw having a long direction making a flaw angle with respect to the axial direction, wherein each one of the at least one phased array probe has at least one aperture emitting an ultrasonic beam and receiving a maximum echo response from each of the plurality of flaws at a series of reception angles with respect to a probe surface normal direction;
• generating angle response curves for each of the plurality of flaws, wherein the angle response curves are plots of the maximum echo response as a function of the reception angle;
• generating a normalization curve, wherein the normalization curve is a plot of a most probable maximum echo response value as a function of the reception angle;
• selecting a plurality of reception channels, wherein each reception channel corresponds to a selected reception angle;
• generating a plurality of calibration targets, wherein each calibration target is defined so as to bring the normalization curve to a predetermined level after calibration, wherein each calibration target is a target for the maximum echo response from one of a plurality of calibration flaws at a corresponding reception channel, and wherein the calibration flaws are selected ones of the plurality of flaws;
• and,
• wherein the calibration step comprises:
• performing a calibration scan of the calibration flaws on the calibration object, wherein a plurality of apertures from each of the at least one phased array probe emits ultrasonic beams and receives the maximum echo responses from the calibration flaws at the corresponding reception channels;
• and
• calibrating the gain of each of the plurality of apertures based on the calibration targets.