Fracture behavior of a corroded structural component under bending load

In order to clarify the significance of corrosion damage for risk assessment, bend tests were carried out on a roughened corroded annular plate prepared from an oil storage tank. It was found that a marked decrease of load carrying capacity occurred in the high deflection region depending upon the degree of corrosion damage. The reason for extensive loss of load carrying capacity was successfully explained from successive observation of crack growth behavior on the corroded surface of the annular plate. Photographic evidence showed that multiple cracks, initiated around individual pits, grew rapidly not only by crack growth, but also by coalescence with other neighboring cracks under the influence of plastic constraint derived from the welded joint. The linking up of multiple cracks leading to a catastrophic failure was considered to be a characteristic event of the roughened corroded component, and was expected to occur depending upon the degree of corrosion damage under a complex stress state.