Hybrid fatigue crack propagation analysis using damage and fracture mechanics methods

Steel structures are frequently exposed to high‐cycle loading in which fatigue cracks initiate and propagate in the service life. The development of crack(s) will affect the structural integrity. In extreme cases, e.g., earthquakes and impacts, structures may be overloaded in several cycles or even a single loading cycle with the development of significant plastic deformation and macro cracks. Service loads, e.g., traffic and waves, will afterwards still be experienced in these damaged structures. The aforementioned two types of deformation are currently analyzed using damage and fracture mechanics methods, respectively. The cycle‐by‐cycle calculation and jump strategy relying on the Paris' equation, are employed for the low (including monotonic) and high‐cycle problems, using elastoplastic and linear‐elastic materials, respectively. The two calculation methods were developed independently, which presents a challenge in analyzing overloaded high‐cycle fatigue problems. This paper presents and executes a hybrid analysis using damage and fracture mechanics models for the single‐edge notch bend specimen. Either linear‐elastic or elasto‐plastic materials is employed in finite element simulations. The hybrid analysis with the combination of damage and linear‐elastic fracture mechanics shows the potential of a promising solution for assessing the fatigue behaviour of steel structures experiencing extreme loading and associated stepwise material damage. Some challenges are addressed in the combination of the ductile fracture followed by the high cycle fatigue calculation.