Eddy Current Testing
In standard eddy current testing, a circular coil carrying an AC current is placed in close proximity to an electrically conductive specimen. The alternating current in the coil generates a changing magnetic field, which interacts with the test object and induces eddy currents. Variations in the phase and magnitude of these eddy currents can be monitored using a second ’search’ coil, or by measuring changes to the current flowing in the primary ‘excitation’ coil. Variations in the electrical conductivity or magnetic permeability of the test object, or the presence of any flaws, will cause a change in eddy current flow and a corresponding change in the phase and amplitude of the measured current. This is the basis of standard (flat coil) eddy current inspection, the most widely used eddy current technique.
Barkhausen Noise Analysis (BNA)
Magnetic Resonance Imaging (MRI) Magnetic resonance imaging (MRI) is an imaging technique used primarily in medical settings to produce high quality images of the inside of the human body. MRI is based on the principles of nuclear magnetic resonance (NMR), a spectroscopic technique used by scientists to obtain microscopic chemical and physical information about molecules.
Microwave InspectionMicrowave (or short-pulse radar) inspection techniques involve the transmission and reflection of relatively low frequency (often around 1 GHz) electromagnetic (EM) waves in various materials. The term ground penetrating radar (GPR) is often used to describe microwave inspection systems for locating utility lines below ground and mild steel rebar in concrete decks/pavements. Microwave inspection exploits the principle that dielectric properties of various materials affect the transmission and reflection of EM waves in those materials.