Ultrasonic testing is a non-destructive testing method that can be used to detect inhomogeneities and defects in the entire cross-sectional area of workpieces made of all types of sound-conducting material.
The test method is based on the transit time measurement of sound waves emitted by an ultrasonic source and the reflections of which are absorbed by the sound sensors. Errors such as inclusions, cracks, blowholes, separation points or the occurrence of boundary surfaces cause a different reflection behavior of the sound waves.
By evaluating the transit times, the type and position of defects can be detected which deviate from known nominal values or wall thicknesses, layer thicknesses and hardness depths can be measured.
The waviness of the test surfaces must not lead to a gap > 0.5 mm between the probe and the test surface. To meet this requirement, the test surfaces may have to be machined.
Only objects or defects larger than half the wavelength of the sound can be detected.
Pipelines in operation that are to be tested for erosion or corrosion damage can also be tested using the ultrasonic method. Weld seams, which have to be checked for reliability and due to the material thickness, the material or the location of the defect to be found, the X-ray inspection can no longer provide reliable information, can be examined with the ultrasonic inspection.