High temperature electromagnetic acoustic transducer (EMAT) probe and coil assemblies

摘要

An enhanced EMAT probe and coil construction takes advantage of heat transfer and magnetic flux principles to permit inspection of workpieces at elevated temperatures of 1200° F. and higher. A ferromagnetic, cup-shaped probe assembly having an end cap and a barrel is provided for carrying a coil assembly, preferably one or more permanent magnets, and a frustoconical focus core. The magnets are located within the barrel and connected to the end cap, and the cup- shaped probe assembly positions the coil assembly proximate the surface of the workpiece. A plurality of passageways may be provided in the end cap and barrel for admitting cooling air to an interior portion of the cup-shaped probe assembly. The cup-shaped probe assembly serves to provide a return path for magnetic flux of the magnetic field back to the permanent magnet means. The coil assembly has a coil disk having a matrix of holes and grooves which allow at least one eddy current coil wire to be threaded and interwoven into the coil disk without shorting against itself. A layer of fiberglass cloth covers the coil assembly to thermally and electronically insulate it from the workpiece, providing a durable, rugged and economical construction.