Testing of bars and billets by electromagnetic methods

Abstract

AbstractThe magnetic leakage flux principle for non-destructive testing utilizes the disturbance of magnetic flux caused by defects in ferromagnetic materials. Different methods for indicating leakage flux are used. Direct methods use field-sensitive elements which scan the material being tested, while indirect methods use magnetic particles. Between these two methods there exists a third one, the magnetic tape method, where magnetic particles are also used. In this case, however, they are not spread over the material being tested but are embedded in a rubber tape which transports the stray flux signals from the surface of the materzal to a scanning device. This paper describes commercial systems which use all three methods; the Magnetograph, the Rotomat, and the continuous powder test system.