title = "Magnetic Particle Testing (MT/MPI)"

content = """
Magnetic Particle Testing (MT), also called Magnetic Particle Inspection (MPI), is an NDT method for detecting surface and near-surface discontinuities in ferromagnetic materials — primarily carbon and low-alloy steels and cast iron. At Ridgecrest Metalworks, MT is used on weldments, forgings, and shafts where surface cracks and lack-of-fusion defects must be identified.

The principle of MT relies on magnetic flux leakage. When a ferromagnetic part is magnetized, magnetic flux travels through the material. At a discontinuity (crack, lamination, porosity near the surface), the flux is forced to leak out of the surface. Finely divided magnetic particles (dry powder or wet suspension) applied to the surface are attracted to and bridge the leakage field, forming a visible indication.

Two magnetization methods are used:
- Yoke (electromagnetic or permanent magnet): Portable handheld device placed on the component; magnetizes the material between the yoke poles. Suitable for field use and large components. The yoke must be oriented in two perpendicular directions (or at 45°/135°) to detect defects at all orientations.
- Prod technique: Two electrodes (prods) are pressed against the surface and current is passed through the metal, inducing a circular magnetic field. Suitable for large weld seams. Creates local heating at contact points; only approved for materials that can tolerate localized resistance heating.

Wet fluorescent MPI uses particles suspended in a carrier fluid (water-based or oil-based) that fluoresce under UV-A (black light) illumination. This is the most sensitive MT technique and is used for critical applications such as aerospace forgings and highly stressed structural welds. Dry particle MT uses colored powder (black, red, or gray) applied to the surface and is used in field inspections where wet technique is impractical.

Acceptance criteria for weld MT inspection are typically per ISO 23278 or customer specifications. Relevant indications are classified by type (linear vs. rounded) and size. Linear indications (cracks, lack of fusion) are generally cause for rejection regardless of size below the threshold; rounded indications (porosity) are assessed by size and distribution.

After inspection, parts are demagnetized to residual magnetism levels acceptable for downstream operations. Residual magnetism is measured with a gaussmeter; values must be below the specified limit before release.
"""

version = "0.0.1"
