Reliability Assessment of Metals with Corrosion Defects under Axial Tension Loading using Damage Tolerance Analysis

The notion of using fracture mechanics in reliability assessment is to make sure that the materials used in manufacturing critical components can survive the intended conditions. Fracture mechanics calculate the energy of a crack using the stress intensity factor (SIF). The SIF is a function of the applied (repeated) load and the orientation of the crack; it determines the extent and form of the plastic component ahead of the crack’s tip. In damage tolerance analysis an assumption is made that fatigue cracks can begin to grow in a component during its functioning life and that evolution of these minor cracks in fatigue will happen with continued applied stress. Determining the initiation of the cracks and the evolution can help assess a component’s reliability. In metals, corrosion pits have been identified as the stress concentrators providing surroundings favorable for crack initiation and propagation. In this work, a Finite Element Analysis (FEA) is applied to study the SIF around a corrosion pit under axial tension loading. The determined SIF has been used in an analytical reliability-based method using first passage probability theory to determine the reliability of corroded cast iron pipes (as an example).