Results of steel specimens tensile testing using the metal magnetic memory method

Dubov, Anatoly; Energodiagnostika Co. Ltd; Russian Federation

Dubov, An.A.; Energodiagnostika Co. Ltd; Russia

ID: ECNDT-0018-2018
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Session: Material Characterisation Metal Magnetic Memory
Room: R2
Date: 2018-06-12
Time: 10:00 - 10:20

It is known that the main sources of damages occurrence in operated engineering products and structures are stress concentration zones (SCZs), in which metal corrosion, fatigue and creep processes develop most intensively. Sizes of local SCZs, in which the metal reaches failure stress with formation of micro- and macrocracks, range from several micrometers to several millimeters. In recent years the metal magnetic memory (MMM) method becomes more and more widespread in practical application in Russia and a number of other countries.

The MMM method – is a passive non-destructive testing method based on the analysis of self-magnetic leakage fields (SMLF) distribution on the products’ surface to detect SCZs, defects and structural inhomogeneities of the metal in products and welded joints. The MMM method does not require external magnetization or any preparation of products’ surfaces to carry out the inspection.

One of the main tasks of the MMM method is detection of local SCZs on the surface and in deep layers of the metal of various inspection objects (IO), as well as determination of the metal’s limit strain state before its failure.

Tensile tests of specimens made of steel 20 with simultaneous measurement of magnetic and mechanical parameters were carried out. Correlation between variation of the specimens’ self-magnetic leakage field and their deformation was demonstrated. Relation between magnetic and mechanical parameters, characterizing the limiting strain capacity of the metal, was established. The possibility of the metal magnetic memory method application to determine the true limit failure stress was demonstrated.