Eddy Current Flaw Detection
Eddy current crack testing is an electromagnetic testing method that uses disturbances in the induced induction field to detect near-surface cracks and material inhomogeneities. It detects microscopic surface cracks and damage in the material structure.
Physical-Chemical Mechanism of Action
Eddy current crack testing uses an electric field generated by a coil circuit. This field induces an alternating current in the material being tested. If there are cracks or material inhomogeneities, this disturbs the electric field and changes the material's inductance. These changes are detected by a detector coil circuit.
Metallurgical Relevance & Welding Risks
Eddy current crack testing is especially useful for detecting cracks and material changes in the weld and the surrounding area. It can help uncover hot cracks before use, which are caused by insufficient cooling or incorrect welding parameters. A negative result indicates possible material degradation or faulty welding processes.
Shop Practice & Instructions
To perform an eddy current crack test, the material to be tested is clamped in a coil circuit. The electric current is activated and the detector signals are recorded and evaluated. A positive signal indicates cracks or inhomogeneities. It's important that the material is clean and free of dirt to get correct results. The test should be done after welding before the material goes into service.