scholarly journals Fully plastic j-integrals for mixed mode fracture induced by inclined surface cracks in pressurized ductile pipes

Author(s):  
Weigang Wang ◽  
Wei Yang ◽  
Chun-Qing Li
Author(s):  
Weigang Wang ◽  
Wei Yang ◽  
Chun-Qing Li

Surface cracks have been recognized as major causes for fracture failures of ductile pipes. This paper intends to derive a normalized fully plastic J-integral solution to mixed-mode fracture caused by inclined surface cracks in pressurized ductile pipes. A combined J-integral and finite element method is developed to evaluate the J-integral for inclined surface cracks. A set of predictive formulas for normalized fully plastic J-integrals are developed. It is found in this paper that the normalized fully plastic J-integral increases with the decrease of crack inclination angle and aspect ratios, and the increase of strain hardening exponent. It is also found that the critical locations of crack propagation occur between the surface point and the deepest point of cracks when the inclination angle is relatively small. The paper concludes that the developed formulas can accurately predict the normalized fully plastic J-integrals along the front of inclined surface cracks. The results presented in the paper can enable researchers and practitioners to accurately predict the mixed-mode fracture failure of pressurized pipes subject to inclined surface cracks.


Author(s):  
Meng Fan ◽  
Yan Jin ◽  
Thomas Wick

AbstractIn this work, we develop a mixed-mode phase-field fracture model employing a parallel-adaptive quasi-monolithic framework. In nature, failure of rocks and rock-like materials is usually accompanied by the propagation of mixed-mode fractures. To address this aspect, some recent studies have incorporated mixed-mode fracture propagation criteria to classical phase-field fracture models, and new energy splitting methods were proposed to split the total crack driving energy into mode-I and mode-II parts. As extension in this work, a splitting method for masonry-like materials is modified and incorporated into the mixed-mode phase-field fracture model. A robust, accurate and efficient parallel-adaptive quasi-monolithic framework serves as basis for the implementation of our new model. Three numerical tests are carried out, and the results of the new model are compared to those of existing models, demonstrating the numerical robustness and physical soundness of the new model. In total, six models are computationally analyzed and compared.


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