Experimental Study of Longevity in the Metallic Structure of Boom for a Portal Crane of Seaport

The usage of cranes in the seaport is widespread and essential. However, long-term use unavoidably leads to failures of portal cranes’ structural parts, severe damages, or total collapses, and is often followed by very high financial losses and serious injuries or crane-related fatalities. Sea portal cranes are operated under intensive cyclic loading, which leads to steel plasticity exhaustion. However, the latent and educated defects that are available during manufacturing and operation lead to a reduction in their useful life. They can serve as concentrators of fatigue cracks; their development is random. The work of quay crane operations for handling “shore-to-ship” was analyzed. For studies, flat beam specimens with one-side notch were used in the ferrite-pearlite class St38b2 steel and cut from the lower and rear shelves of the crane boom, as well as the right boom, used for 40 years in the river port. From the obtained experimental kinetic diagrams of the fatigue fracture of the material, it was found that an increase in the asymmetry of the cycle leads to an intensification of crack growth at values of 0.6 and 0.8. Also, there was no crack closure effect, a decrease in the fatigue threshold, and crack growth was intensified over the entire range. The metallographic evaluation of experimental samples showed the absence of intercrystalline corrosion.