Widely-used in industry, pipeline structures might contain defects (cavities, cracks) which can be generate during fabrication, handling, girth-welding, or year-long operations. Their replacement is complex and expensive, therefore it is important to determine critical and non-critical defects. Pipelines indeed undergo internal pressure cycles so that defects such as cracks may propagate therefore affecting their lifetime.
This study is part of a larger work aiming at estimating global fracture parameters in components such as the stress intensity factors as well as the J–integral. It is common to address this problem using charts or simplified formulas that enable to quickly estimate stress intensity factors in structures containing cracks (Zerbst et al, 2007). Nevertheless those charts only deal with standard crack configurations and the interaction between cracks is rarely taken into account. A higher accuracy is indeed obtained using full-field finite element computations which however are very time consuming in particular if plasticity needs to be accounted for. To achieve both accuracy and fast response, it is proposed in this work to use a hyper-reduction method which has shown considerable speed improvement in plasticity (Ryckelynck et al, 2015).
The method allows describing structures and defects separately owing to their different sizes. Reduced basis are first created for both uncracked structures and defects. Multiscale construction techniques are then used to rapidly obtain solutions for cracked structure in the context of small deformations (Lacourt,2019). The technique thus allows (re)using crack databases on various structure. The new method is applied to a straight pipe containing various cracks. Results are compared to both full finite element simulations and known reference solutions. More complex cases for which no simple solutions exit, such as dissymmetric cracks, non-planar cracks or cracks with wavy front, are also investigated.