Intergranular corrosion in an aircraft structure may be defected by ultrasonic inspection. The first pip represents the front side of the structure, third pip represents the back sale of the structure, and the pip in the middle represents the location of the corrosion within the structure.
A method of detecting material thickness or an indicator of the internal damage by injecting variable-frequency ultrasonic energy into a material. A specific frequency of energy will produce the greatest return in a given thickness of material. When equipment is calibrated for a specific thickness and this thickness changes, an aural or visual indication of this change is given during this inspection.