Magnetic Estimation of Stresses in Welded Joint Zones with Different Initial Plastic Strains

Gorkunov, Eduard; Institute of Engineering Science, Ural Branch of the Russian Academy of Sciences; Russian Federation

Gorkunov, E.S.; Institute of Engineering Science UB of RAS; Russia
Povolotskaya, A.M.; Institute of Engineering Science UB of RAS; Russia
Zadvorkin, S.M.; Institute of Engineering Science UB of RAS; Russia

ID: ECNDT-0057-2018
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During assembly or transportation to the site of assembly, as well as in operation, structural components may suffer additional uncontrollable plastic strain. This may change the initial level of informative test parameters.
In order to determine the capabilities of magnetic methods for the estimation of the stress-strain parameters of the material of individual zones of welded metal structures, in view of their his-tory, the effect of preliminary plastic strain on the magnetic behaviour of metal in different zones of a welded pipe under subsequent elastic tension/compression is studied.
Three groups of flat tensile test specimens cut out from the base metal, the weld and the heat-affected zone (HAZ) of a pipe made of the X70 steel are studied. In the first stage, the speci-mens were subjected to uniaxial tension to different values of plastic strain. In the second stage, the specimens plastically tensioned to different values were subjected to elastic tension/compression.
A correlation has been found between the magnetic characteristics of the metal in the differ-ent zones of the welded X70 steel pipe and the amount of plastic strain in these zones.
The magnetic behaviour of the base metal, the materials of the weld and the HAZ of a pipe has been determined as dependent on applied uniaxial tensile/compressive stresses, in view of the material history in the form of plastic strain to different degrees.
The magnetic characteristics of the materials are shown to vary uniquely in the range of ap-plied elastic uniaxial stresses between ‒200 and 120 MPa, and this makes them usable for the evalu-ation of the stress-strain state of the individual zones of welded X70 steel pipes.
The obtained results testify to the necessity of taking into account the initial SSS of metal structures when developing magnetic methods for the determination of their SSS parameters.