Patent ID: 7240554

Claim:
A method for determining the size of a crack in a workpiece, using the ultrasonic pulse-echo method, said method involving the following method steps: a workpiece is chosen having a front face and a back face, wherein the workpiece exhibits a crack starting at the back face, an angle beam probe is placed on the front face, the angle beam probe sends ultrasonic pulses at an angle alpha into the workpiece and receives echo signals of said pulses, the angle beam probe is moved at least once over the crack so that the radiation beam of the angle beam probe sweeps across the entire crack, the received echo signals are digitalized and stored in a memory as pairs of echo signal values over travel time, whereby the stored pairs of values form a multitude and an envelope curve is constructed of this multitude, wherein for the construction of the envelope curve the high values of the stored pairs are used, and the size of the crack is calculated from the width of the envelope curve at a predetermined partial amplitude and from the maximum amplitude of the envelope curve, wherein the size of the crack is proportional to the product of the maximum amplitude of the envelope curve and the width of the envelope curve at 50% of the maximum amplitude.