Visit Iowa State University for more information on ultrasonic inspection. Liquid Penetrant Inspection Liquid Penetrant is considered one of the more simple inspection methods. The Penetrant pulls the dye into any defects open to the surface. After removing the excess Penetrant a developer, similar to talcum powder, is applied. This helps draw the Penetrant to the surface of the part and provides a contrasting background for the Penetrant.
Penetrant dyes come in either a visible red dye or a fluorescent dye.
By generating high frequency alternating electrical current through a coil the associated expanding and collapsing magnetic fields will produce, in a conductive material, a week electrical current and it's associated magnetic fields. If the electrical currents are disrupted by a crack, change in material properties, or nonconductive coating an indication will be produced on a meter, or Cathode Ray Tube. Eddy current inspections are performed on aircraft to locate cracks or to determine paint coating thickness. Eddy current inspections are also used in electrical generating plants to locate thinning and cracks in tubing. By magnetizing a ferromagnetic material, areas of cracks or other disruptions of the continuity at or near the surface of the material will produce a leakage of the magnetic field.