Magnetic Testing Fundamentals

The magnetic field that remains in a ferromagnetic material after the magnetizing force is removed.

A high residual field in a material means that the magnetic field will remain strong even after the magnetizing force is removed.

A low residual field in a material means that the magnetic field will weaken quickly after the magnetizing force is removed.

The strength of the magnetic field required to demagnetize a ferromagnetic material.

High coercive force means that a strong magnetic field is needed to demagnetize the material.

Low coercive force means that a weak magnetic field is needed to demagnetize the material.

The ability of a material to become magnetized.

The areas at each end of a magnet where the magnetic field is strongest.

The magnetic field distribution around a solid magnetic material carrying direct current.

The magnetic field distribution around a solid magnetic material carrying alternating current.

The magnetic field distribution around a hollow conductor of a nonmagnetic material carrying direct current.

The magnetic field distribution around a hollow conductor of a magnetic material carrying direct current.

The magnetic field distribution around a hollow conductor of a magnetic material carrying alternating current.

The magnetic field distribution around a nonmagnetic central conductor carrying direct current inside a hollow magnetic material.

The direction of magnetic lines of force is always perpendicular to the direction of the magnetizing current. This ensures that any defects present within the material are perpendicular to the magnetic field, making them easier to detect.

The process of creating a magnetic field within a material for magnetic particle inspection. The direction of the magnetic field is crucial for defect detection.

Magnetizing a component by sending current directly through the part. This method is most effective when the material can be easily energized with a current.

Magnetizing a component indirectly by bringing the part close to a magnetic field. This is helpful when it is impractical to pass current directly through the object.

The smallest magnetic unit within a material. Each domain acts like a tiny magnet, aligned with its north and south poles.

The process of changing the magnetic properties of a material in response to an external magnetic field. It is related to how the magnetic field interacts with the domains in the material.

The relationship between the magnetizing force and the magnetization of a material. It reflects the material's ability to retain its magnetic properties even after the magnetizing force is removed.

The separation between yoke poles, measured as a quarter of this distance on either side of the centerline.

The distribution of the magnetic field generated by a coil. It is measured using a QQI (Quantitative Quality Indicator).

The magnetic field that runs perpendicular to the direction of the magnetizing current. Ideal for detecting surface breaking defects.

The magnetic field that runs parallel to the direction of the magnetizing current. Ideal for detecting subsurface defects.

The rate at which the magnetic field changes directions, measured in Hertz (Hz).

A phenomenon where alternating current (AC) is concentrated near the surface of a conductor. This is why AC is primarily used for surface defect detection in MT.

The temperature at which a ferromagnetic material loses its magnetic properties. Above this temperature, the material becomes paramagnetic.

A technique using a magnetic field opposite to the existing magnetization to reduce or eliminate it.

A method of demagnetization where a DC current is gradually reduced and reversed until it reaches zero, effectively demagnetizing the material.

A demagnetization technique using a yoke (a U-shaped magnet) with alternating current to create a changing magnetic field that demagnetizes the material.

The part being demagnetized should be oriented with its longest axis in an east/west direction.

Demagnetization equipment using DC currents that are stepped down and reversed to demagnetize materials.

A method of demagnetization using DC step-down reversing currents, typically completed in about 30 seconds with one second per step.

Demagnetization equipment that uses a yoke with AC current to demagnetize materials.

A type of magnetic field created by a direct current (DC) source, where the current constantly flows in one direction.

The depth a magnetic field can penetrate into a material. It's limited in HWDC due to the pulsating nature of the field.

A type of magnetic field created by inverting the negative portion of an alternating current (AC) flow, making the current flow continuously in one direction.

A more powerful type of FWDC created by using three-phase AC electricity. It offers a faster response and better indication formation.