Finite-element analysis of the reliability of corroded welded pipelines at non-destructive evaluation and state monitoring

Speaker:
Milenin, Alexey; Institut elektrozvaruvanna imeni E O Patona Nacional'na akademia nauk Ukraini; Ukraine

Authors:
Makhnenko, O.; E.O. Paton Electric Welding Institute of NAS of Ukraine; Ukraine
Milenin, A.; E.O. Paton Electric Welding Institute of NAS of Ukraine; Ukraine
Pivtorak, N.; E.O. Paton Electric Welding Institute of NAS of Ukraine; Ukraine
Rozynka, G.; E.O. Paton Electric Welding Institute of NAS of Ukraine; Ukraine
Velikoivanenko, E.; E.O. Paton Electric Welding Institute of NAS of Ukraine; Ukraine

ID: ECNDT-0149-2018
Session: Meta Modeling
Room: J2
Date: 2018-06-12
Time: 16:40 - 17:00

The assessment of residual life of critical structures includes analysis of the results of flaw detection with corresponding computational confirmation of their static strength and long-term workability. Main and technological pipelines are typical structures of various industrial systems being operated under complex thermal and force loading that complicates computation analysis of their state. Most of the pipelines are welded only one time, therefore, weld metal and heat affected zone are the regions of local inhomogeneity that should be taken into account at definition of conservative methodology for evaluation of revealed defects’ acceptability. A numerical methodology of reliability of defective welded structures has been developed within the limits of this work with regard to steel pipelines having local corrosion defects of metal loss in the region of circumferential or multipass repair welds. An analysis of a stressed-deformed state of the pipeline has been implemented. The latter is based on finite-element solution of a problem of non-stationary thermoplasticity by tracing the elastic-plastic deformations from the beginning of welding to the complete cooling of the pipe and subsequent static or cyclic nonisothermal loading to the limit state. A continuous dilatation model of fracture and criteria for macroscopic failure are based on a stepwise prediction of micro- and macro-damage of the material. This numerical methodology allowed predicting the workability of welded pipelines with revealed isolated or multiple corrosion defects at minimum schematization and conservatism. Typical corrosion-erosion defectiveness of pipelines was used as an example of study of influence of operation conditions and actual state of the structure. Thus, character of interaction between welding area and geometry anomaly and its influence on peculiarities of subcritical and critical fracture under static and cyclic loading have been studied. Additional impact of creep deformation has been investigated for technological pipeline operated under high temperatures.