Method and device for detecting a defect using ultrasound

A method for detecting a defect in a region of interest within a part to be tested, said method comprising the following successive steps:

• a) for a reference part identical to the part to be tested but free from defects,
• a1) determining a set of resonant modes each defining:
• a resonant frequency of the reference part, considering that the modulus of elasticity of the reference part is constant, and
• a field of mechanical stresses or deformations on and/or in the reference part that are generated when the reference part resonates at said resonant frequency;
• a2) selecting the resonant mode, referred to as “optimum resonant mode”, that generates, in the region of interest, a maximum mechanical stress or deformation compared to the other resonant modes;
• b) determining a loading mode, referred to as “optimum” loading mode, that primarily activates said optimum resonant mode, a loading mode defining at least an excitation wave, an injection zone where the excitation wave is injected into the reference part, and an output zone where an output wave resulting from the excitation wave passing through from the injection zone to the output zone is picked up;
• c) carrying out nonlinear resonant spectrometry analysis based on the optimum loading mode, so as to determine a nonlinearity parameter for each of said part to be tested and reference part;
• d) classifying the part to be tested on the basis of the difference between the nonlinearity parameters for the part to be tested and for the reference part.