Inspection method using magnetic particles in a liquid carrier in combination with electrical detection means

摘要

A method for inspecting the surface of a workpiece for the presence of flaws using a ferrofluid as a penetrant which is applied to the surface of the workpiece and then scanning the surface of the workpiece with electrical detection means placed adjacent to the surface for providing responses indicative of the presence of flaws in the surface of the workpiece. If desired, a magnetic field can be used to induce the flow of the ferrofluid into any flaws prior to inspection, and for post-inspection cleanup as well. By the use of a ferrofluid, the sensitivity of the electrical detection means, advantageously of the eddy current type, is enhanced in typical applications, and also allows the use of an eddy current probe to inspect workpieces made of nonconductive and/or nonferromagnetic materials.