Finite-element simulation of ductile crack propagation in steel structures

Fracture is a critical limit state in steel structures, which can lead to catastrophic failure of structural components. As such, understanding of the fracture process is crucial in order to maintain function of critical components in structures, so that global stability under extreme loads can be maintained. Over the past three decades, aided by advances in computing power and structural analysis software, significant advances have been made in the development of computational models which can predict the initiation of fracture in steel structures under complex stress states and loading conditions.

While these models have proved useful, they are only capable of predicting the initiation of a ductile crack. Many full-scale structural tests have demonstrated that steel components can often withstand significant ductile crack growth (up to several millimeters) before ultimate failure. Therefore, methods to reliably simulate the growth of ductile cracks after they initiate must be developed.

To address this shortcoming, an adaptive cohesive zone (ACZ) model for simulating ductile crack propagation was developed. The ACZ model is a hybrid model which combines an established model for ductile fracture initiation under complex stress states (the stress-weighted ductile fracture model) and the cohesive zone model for simulating the formation of new crack surfaces in continuum finite element analyses. Theoretical background and details on computational implementation will be discussed, along with methods for calibrating and validating the various model parameters. Results of coupon-scale experiments will be compared to complimentary finite element analyses to demonstrate the capabilities of the new model.

Learning Objectives:
Describe the mechanisms which lead to ductile fracture in steel components.

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