Ultrasonic inspection configuration with beam overlap verification

Abstract

Disclosed is a beam overlap verification system and method for phased array ultrasonic inspection. A scan plan for the ultrasonic inspection defines a suitable probe, wedge and calibration block having machined defects for the geometry to be inspected, and makes a beam definition which defines a set of ultrasonic beams emitted by the phased array. An intersection amplitude unit records the response amplitudes from each defect at predetermined intersection points of adjacent beam pairs as the probe and wedge are manually scanned across the calibration block. An overlap verification module determines the −6 dB overlap of all adjacent beam pairs which are relevant to the geometry to be inspected, and verifies that the beam overlap conforms to the required coverage according to the ASME or other relevant codes. In this way, coverage is experimentally verified during calibration prior to inspection of a known geometry, such as a weld.

What is claimed is: 
     
         1 . An overlap verification system for a non-destructive testing (NDT) system for inspecting a test object, the overlap verification system comprising:
 a calibration block having a block top surface and a plurality of known defects, among which a selected defect is at a selected depth below the block top surface;   a phased array probe being moved over the block top surface through a plurality of probe positions, the probe transmitting a plurality of ultrasonic beams, namely beam(n), where n=1 to N, and wherein the beam(n) has at least one adjacent beam, namely beam(n−1) and/or beam(n+1);   an acquisition unit configured to detect a plurality of response amplitudes of echo signals corresponding to reflections of the plurality of ultrasonic beams from the selected defect;   an intersection amplitude unit configured to record a maximum amplitude of beam(n) reflected from the selected defect and to acquire at least one intersection amplitude at each of a plurality of intersection probe positions where there are predetermined relationships that provide known beam overlap percentages between reflections of beam(n) and reflections of the at least one adjacent beam; and, an overlap verification module configured to calculate amplitude drops of the at least one intersection amplitude relative to the maximum amplitude, and to determine a test overlap percentage between beam(n) and the at least one adjacent beam based on the known beam overlap percentages and the amplitude drops, and to verify that the test overlap percentage is greater than a predetermined threshold.   
     
     
         2 . The overlap verification system of  claim 1  wherein the maximum amplitude of beam(n) is recorded at a first intersection probe position of the plurality of intersection probe positions, and a first intersection amplitude of the at least one intersection amplitude is the corresponding response amplitude of the at least one adjacent beam at the first intersection probe position, and a first amplitude drop of the amplitude drops is the ratio of the first intersection amplitude to the maximum amplitude. 
     
     
         3 . The overlap verification system of  claim 2  wherein a second intersection amplitude of the at least one intersection amplitude is recorded at a second intersection probe position of the plurality of intersection probe positions, wherein the response amplitude of beam(n) at the second intersection probe position and the response amplitude of the at least one adjacent beam at the second intersection probe position are both equal to the second intersection amplitude, and wherein a second amplitude drop is the ratio of the second intersection amplitude to the maximum amplitude. 
     
     
         4 . The overlap verification system of  claim 3  wherein the known beam overlap percentages comprise a first known beam overlap percentage of 50% at the first amplitude drop, and a second known beam overlap percentage of 0% at the second amplitude drop. 
     
     
         5 . The overlap verification system of  claim 4  wherein the predetermined threshold is a code overlap threshold at a code amplitude drop, and wherein the code overlap threshold and the code amplitude drop correspond to an industry regulation. 
     
     
         6 . The overlap verification system of  claim 5  wherein the test overlap percentage is determined at the code amplitude drop by interpolation between the first amplitude drop and the second amplitude drop. 
     
     
         7 . The overlap verification system of  claim 6  wherein the interpolation is linear. 
     
     
         8 . The overlap verification system of  claim 6  wherein the interpolation is non-linear. 
     
     
         9 . The overlap verification system of  claim 1  wherein the NDT system is for inspecting a weld in the test object and the selected depth corresponds to a depth within the weld. 
     
     
         10 . The overlap verification system of  claim 9  further comprising a beam relevance module for rejecting beams whose echo signals emanate from regions in the calibration block corresponding to regions outside a relevant weld inspection volume within the test object. 
     
     
         11 . The overlap verification system of  claim 5  further comprising an overlap optimization module for adjusting the plurality of ultrasonic beams so that the test overlap percentage of each of the plurality of beams(n) for n=1 to N conforms to the industry regulation. 
     
     
         12 . The overlap verification system of  claim 1  wherein each of the plurality of ultrasonic beams is emitted from a probe aperture at a refraction angle, and wherein the plurality of ultrasonic beams comprise sectorially scanned beams wherein the refraction angle is swept through a range of angles. 
     
     
         13 . The overlap verification system of  claim 12  wherein the plurality of ultrasonic beams are calibrated so that amplitudes of echo signals reflected from the selected defect are substantially equal for the plurality of ultrasonic beams having the range of angles. 
     
     
         14 . The overlap verification system of  claim 1  wherein the phased array probe has a plurality of selected apertures, and wherein each of the plurality of ultrasonic beams is emitted from a selected variable aperture at a fixed refraction angle, and wherein the plurality of ultrasonic beams comprise linearly scanned beams wherein there is lateral translation of the selected variable aperture. 
     
     
         15 . An overlap verification method for a non-destructive testing (NDT) system for inspecting a test object, the overlap verification method comprising the steps of:
 moving a phased array probe over a top surface of a calibration block having a plurality of known defects, among which a selected defect is at a selected depth below the block top surface;   configuring the probe to transmit a plurality of ultrasonic beams, namely beam(n), where n=1 to N, and wherein beam(n) has at least one adjacent beam, namely beam(n−1) and/or beam(n+1);   detecting a plurality of response amplitudes of echo signals corresponding to reflections of the plurality of ultrasonic beams from the selected defect;   recording a maximum amplitude of beam(n) reflected from the selected defect;   acquiring at least one intersection amplitude at a plurality of intersection probe positions where there are predetermined relationships that provide known beam overlap percentages between reflections of beam(n) and reflections of the at least one adjacent beam;   calculating amplitude drops of the at least one intersection amplitude relative to the maximum amplitude;   determining a test overlap percentage between beam(n) and the at least one adjacent beam based on the known beam overlap percentages and the amplitude drops; and,   verifying that the test overlap percentage is greater than a predetermined threshold;   
     
     
         16 . The overlap verification method of  claim 15  further comprising the steps of:
 recording the maximum amplitude of beam(n) at a first intersection probe position of the plurality of intersection probe positions; 
 recording a first intersection amplitude of the at least one intersection amplitude , wherein the first intersection amplitude is the response amplitude of the at least one adjacent beam at the first intersection probe position; and, 
 calculating a first amplitude drop of the amplitude drops, wherein the first amplitude drop is the ratio of the first intersection amplitude to the maximum amplitude. 
 
     
     
         17 . The overlap verification method of  claim 16  further comprising the steps of:
 recording a second intersection amplitude of the at least one intersection amplitude at a second intersection probe position of the plurality of intersection probe positions, wherein the response amplitude of beam(n) at the second intersection probe position and the response amplitude of the at least one adjacent beam at the second intersection probe position are both equal to the second intersection amplitude; and, 
 calculating a second amplitude drop, wherein the second amplitude drop is the ratio of the second intersection amplitude to the maximum amplitude. 
 
     
     
         18 . The overlap verification method of  claim 17  wherein the known beam overlap percentages comprise a first known beam overlap percentage of 50% at the first amplitude drop, and a second known beam overlap percentage of 0% at the second amplitude drop. 
     
     
         19 . The overlap verification method of  claim 18  wherein the predetermined threshold is a code overlap threshold at a code amplitude drop, and wherein the code overlap threshold and the code amplitude drop correspond to an industry regulation. 
     
     
         20 . The overlap verification method of  claim 19  wherein the step of determining the test overlap percentage includes determining the test overlap percentage at the code amplitude drop by interpolation between the first amplitude drop and the second amplitude drop. 
     
     
         21 . The overlap verification method of  claim 20  wherein the interpolation is linear. 
     
     
         22 . The overlap verification method of  claim 20  wherein the interpolation is non-linear. 
     
     
         23 . The overlap verification method of  claim 15  wherein the NDT system is for inspecting a weld in a test object and the selected depth corresponds to a depth within the weld. 
     
     
         24 . The overlap verification method of  claim 23  further comprising a step of rejecting beams whose echo signals emanate from regions in the calibration block corresponding to regions outside a relevant weld inspection volume within the test object. 
     
     
         25 . The overlap verification method of  claim 19  further comprising a step of adjusting the plurality of ultrasonic beams so that the test overlap percentage of each of the plurality of beams(n) for n=1 to N conforms to the industry regulation. 
     
     
         26 . The overlap verification method of  claim 15  wherein each of the plurality of ultrasonic beams is emitted from a probe aperture at a refraction angle, and wherein the plurality of ultrasonic beams comprise sectorially scanned beams wherein the refraction angle is swept through a range of angles. 
     
     
         27 . The overlap verification method of  claim 26  further comprising a step of calibrating the plurality of ultrasonic beams so that amplitudes of echo signals reflected from the selected defect are substantially equal for the plurality of ultrasonic beams having the range of angles.