Methods and systems for detecting defects in welded structures

A method for testing a weld for the presence of defects, the method comprising:

• inducing ultrasonic signals at multiple measurement locations along the weld;
• collecting an ultrasonic response signal for each of the measurement locations along the weld;
• filtering the ultrasonic response signal from each of the measurement locations by:
• decomposing the ultrasonic response signal by discrete wavelet transform with a plurality of mother wavelets to produce sets of wavelet coefficients corresponding to each mother wavelet;
• band pass filtering the sets of wavelet coefficients to isolate a frequency range sensitive to defects in the weld;
• reconstructing each set of filtered wavelet coefficients by inverse discrete wavelet transform to produce a plurality of filtered response signals for each measurement location;
• calculating a plurality of energy distributions for the weld based on the plurality of filtered response signals for each of the measurement locations;
• and
• comparing each of the plurality of energy distributions to a corresponding baseline energy distribution to determine the presence of a defect in the weld.

A defect detection system for determining the presence of defects in a weld, the defect detection system comprising a controller, an acoustic signal generator, an acoustic signal detector, and a positioning device, wherein the acoustic signal generator, the acoustic signal detector and the positioning device are electrically coupled to the controller and the controller is programmed to:

• induce ultrasonic signals at multiple measurement locations along the weld with the acoustic signal generator;
• collect an ultrasonic response signal from each of the measurement locations with the acoustic signal detector and store the ultrasonic response signals in a memory operatively associated with the controller;
• filter the ultrasonic response signal collected from each of the measurement locations to produce a plurality of filtered response signals for each of the measurement locations;
• calculate a plurality of energy distributions for the weld based on the plurality of filtered response signals for each of the measurement locations;
• and
• determine the presence of defects in the weld by comparing each energy distribution to a corresponding baseline energy distribution by calculating a summed energy difference distribution for the weld and identifying locations along the weld which have a summed energy difference that is less than a low energy threshold.

A method for processing ultrasonic response signals collected from a plurality of measurement locations along a weld to determine the presence of a defect in the weld, the method comprising:

• filtering an ultrasonic response signal from each of the measurement locations to produce a plurality of filtered response signals for each of the measurement locations, wherein each filtered response signal corresponds to specific types of defects;
• calculating a plurality of energy distributions for the weld based on the plurality of filtered response signals for each of the measurement locations;
• and
• determining the presence of defects in the weld by comparing each energy distribution to a corresponding baseline energy distribution by calculating a summed energy difference distribution for the weld and identifying locations along the weld which have a summed energy difference that is less than a low energy threshold.