Ultrasonic measurement system and detection method for detecting deep structural fissures

The present application discloses an ultrasonic measurement system and a detection method for detecting deep structural fissures. By utilizing the detection method, the size of a deep sub-wavelength-scale linear micro-fissure of a material can be quantitatively detected. After being excited by ultrasonic pulses, the micro-fissure deep in the material can generate ultrasonic scattering and reflection; after being received by an ultrasonic transducer, ultrasonic signals pass through a signal amplifier and an analog-to-digital converter and are stored in a computer; and a power spectrum of the ultrasonic signals is obtained by computing. A spectrum parameter, namely a power spectrum slope, can be obtained by carrying out linear fitting on low-frequency bands of the power spectrum, the spectrum slope and the diameter of the micro-fissure are in one-to-one correspondence, and the diameter of the sub-wavelength micro-fissure can be quantitatively evaluated by computing the slope. Because the quantitative detection