Localizing gradient damage model with decreasing interactions

• Published in: International journal for numerical methods in engineering Vol. 110; no. 6; pp. 503 - 522
• Main Authors: Poh, Leong Hien, Sun, Gang
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 11.05.2017; Wiley Subscription Services, Inc
• Subjects: Consistency; Damage; Damage assessment; Deformation; Failure; Finite element method; Fracture mechanics; frature; gradient damage; localization; Microcracks; micromorphic continua
• ISSN: 0029-5981; 1097-0207
• DOI: 10.1002/nme.5364

Summary Nonlocal integral and/or gradient enhancements are widely used to resolve the mesh dependency issue with standard continuum damage models. However, it is reported that whereas the structural response is mesh independent, a spurious damage growth is observed. Accordingly, a class of modified nonlocal enhancements is developed in literature, where the interaction domain increases with damage. In this contribution, we adopt a contrary view that the interaction domain decreases with damage. This is motivated by the fact that the fracture of quasi‐brittle materials typically starts as a diffuse network of microcracks, before localizing into a macroscopic crack. To ensure thermodynamics consistency, the micromorphic theory is adopted in the model development. The ensuing microforce balance resembles closely the Helmholtz expression in a conventional gradient damage model. The superior performance of the localizing gradient damage model is demonstrated through a one‐dimensional problem, as well as mode I and II failure in plane deformation. For all three cases, a localized deformation band at material failure is obtained. Copyright © 2016 John Wiley & Sons, Ltd.