Fracture mechanics

From the beginning of the industrial era to the end of the first half of the 20th century, engineers were confronted with unexplained rupture phenomena directly involving human safety. Boiler explosions, gas appliance explosions, sudden ruptures of liberty-ships during the Second World War, in-flight explosions of the first Comet commercial aircraft equipped with turbojet engines in the 1950s. These cases can be considered as the founders of fracture mechanics, whose theory, based on the presence of cracks, was developed in the first half of the 20th century, with the first applications in industry starting in the 1960s. Since then, fracture mechanics has gone from strength to strength, and the development of computer science has opened the way to numerical methods that can model complex cracks as closely as possible, with simulation times compatible with industrial design cycles.

In this article, we will review the principles that are important to know when dealing with fracture mechanics, then present the concepts of linear fracture mechanics, which enable engineers to deal with defect propagation via the concept of stress intensity factor and the laws describing cracking kinetics. Finally, a focus will be given on an industrial application in the aeronautics industry, with information on regulatory aspects and the implementation of a fatigue cracking study for a turbomachinery part.