PSI - Issue 16

Oleksiy Nemchuk et al. / Procedia Structural Integrity 16 (2019) 245–251 Oleksiy Nemchuk et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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No clear dependence between polarization resistance and operated stress of metal was revealed (Fig. 4a) but a clear correlation between the mechanical and electrochemical metal characteristics is shown (Fig. 4b): the metal with a lower brittle fracture resistance has a lower polarization resistance. This relationship is suggested to use for non destructive examination of metal state of portal cranes in a course of their long term service.

Fig. 3. Dependence of impact toughness KCV and cyclic stress range Δ σ e for longitudinal ( 1 ) and transversal ( 2 ) specimens .

Fig. 4. Dependence of polarization resistance R p on stress range Δ  s (a) and impact strength KCV (b).

4. Summary Some units of 33 year operated crane are investigated from the point of a possible loss by rolled steel its initial mechanical properties. In-service loading of some units was modelled by the strain measurement and calculated methods and an agreement between the results of the stress state evaluation on rolling sheet surface by the different methods was shown. A level of operational stresses in different units varies by a factor of three. A strong dependence between the assessed level of in-service stresses and a drop of impact strength determined by Charpy testing is established. This indicates a crucial role of the force factor in a decrease in brittle fracture resistance of the operated metal. Comparison of the test results for the specimens cut in mutually perpendicular directions showed that the impact strength level of the transverse specimens relative to the rolling direction is lower than the longitudinal ones. This difference is revealed to become more pronounced with the build-up of metal degradation and, respectively, with an increase of operational stresses. Polarization resistance is defined for the tested units as the electrochemical parameter most sensitive to materials in service degradation. A clear correlation between the mechanical and electrochemical metal characteristics is shown: the metal with a lower brittle fracture resistance has a lower polarization resistance. This relationship is suggested to use for non-destructive examination of metal state of portal cranes in a course of their long term service.