There have been a number of studies concerning the integrity of high-strength carbon steel pipe elbows weakened by local pipe wall thinning, the latter can be typically caused by flow accelerated erosion/corrosion. In particular, the focus of several recent studies was on low cycle fatigue behavior of damaged elbows, mainly, in relation to strength and integrity of piping systems of nuclear power plants subjected to extreme loading conditions, such as earthquake or shutdown. The current paper largely adopts the existing methodology, which was previously developed, and extends it to copper-nickel elbows, which are widely utilized in civil infrastructure in seismically active regions. FE (finite element) studies along with a full-scale testing program were conducted and the outcomes are summarized in this article. The overall conclusion is that the tested elbows with various severity of local wall thinning, which were artificially introduced at different locations, demonstrate a strong resistance against low cycle fatigue loading. In addition, elbows with wall thinning defects possess a significant safety margin against seismic loading. These research outcomes will contribute to the development of strength evaluation procedures and will help to develop more effective maintenance procedures for piping equipment utilized in civil infrastructure.

Various industrial standards and safety regulations specify the minim number of cycles, which pressure equipment must tolerate during a single seismic event. The compliance with these standards and regulations is necessary in order to ensure safety and strength of critical structural components, eg, pressure pipe system of the primary coolant loop of nuclear reactors or condensed water supply of large hospitals or other large facilities. However, the strength can degrade with time due to flow accelerated corrosion causing wall thinning. Pipe bends are particularly susceptible to the localised corrosion, and, therefore, these structural elements need a special consideration. The current paper studies the effect of localised corrosion on low cycle fatigue behaviour of a copper-nickel elbows using experiment and finite element method (FEM). The outcomes of the study demonstrate a quite low reduction of low cycle fatigue life even at severe local wall thinning at different locations.

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