Nonlocal continuum damage models for quasi-brittle fracture: algorithms and applications

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School of Engineering | Doctoral thesis (article-based) | Defence date: 2021-10-14
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Date

2021

Department

Rakennustekniikan laitos
Department of Civil Engineering

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Mcode

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Language

en

Pages

66 + app. 136

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Aalto University publication series DOCTORAL DISSERTATIONS, 127/2021

Abstract

Quasi-brittle fracture – characteristic for mineral-based materials typical in construction – concerns a large number of structural failures which, due to the abrupt nature of the phenomenon, may cause loss of lives and damage to infrastructure. Therefore, it is crucial to develop numerical methods, besides certain theoretical and experimental approaches, to predict the whole process of mechanical failure from the elastic phase, the damage initiation, the stable and unstable propagation of failure until the final rupture. This dissertation studies a continuum damage approach, by focusing on the development of a nonlocal model with enhanced performance and accuracy in the modeling of localized quasi-brittle damage. The damage model is formulated to cope with a wide range of mineral-based materials, including plain and spatially random heterogenous concrete in which the variability of material properties substantially influences the global response of the structures. For the class of microarchitectural materials, the damage model is enriched in light of a simplified form of Mindlin's strain gradient elasticity theory. The gradient-enriched model is proved to be capable of capturing the size effects induced by microarchitectures in both the elastic and the softening regimes, especially in finer scales where the characteristic size of the internal structure is of the same order as the exterior dimensions of the specimen itself. For thin-walled structures, the damage model is integrated into a plate model of third-order shear deformation theory to remedy the computational burden of the corresponding simulations with nonlinear three-dimensional models. The plate formulations cover various functionally graded material configurations with material properties set to smoothly vary in the direction of the plate thickness. For the numerical implementations of the dissertation, either the finite element or isogeometric Galerkin methods are employed in the form of an in-house software package. The former, as a de facto industrially accepted methodology for computational mechanics, boasts an excellent capability in meshing complex geometries, whereas the latter is exploited in the present dissertation for the non-standard gradient-enhanced problem settings that require higher-order continuity over element boundaries. Through a series of benchmark problems, the implementations of the numerical methods are verified and the damage models are validated, and the roles of their key features are demonstrated.

Description

Defence is held on 14 October 2021 at 12:00 Online https://aalto.zoom.us/j/7799660770

Supervising professor

Niiranen, Jarkko, Associate Prof., Aalto University, Department of Civil Engineering, Finland

Thesis advisor

Niiranen, Jarkko, Associate Prof., Aalto University, Department of Civil Engineering, Finland

Keywords

continuum damage, nonlocal interactions, quasi-brittle failure, heterogeneous material, micro-architecture, strain-gradient theory, size effect, third-order shear deformation theory, functionally graded material

Other note

Parts

  • [Publication 1]: Nguyen, Hoang Anh Tuan; Bui, Quoc Tinh; Hirose, Sohichi. 2018. Smoothing gradient damage model with evolving anisotropic nonlocal interaction tailored to low-order finite elements. Elsevier. Computer Methods in Applied Mechanics and Engineering, Volume 328, pages 398-541. ISSN: 0045-7825.
    DOI: 10.1016/j.cma.2017.09.019 View at publisher
  • [Publication 2]: Castillo, Daniel; Nguyen, Hoang Anh Tuan; Niiranen, Jarkko. 2021. Spatially random modulus and tensile strength: contribution to variability of strain, damage, and fracture in concrete. SAGE. International Journal of Damage Mechanics. ISSN: 1056-7895.
    DOI: 10.1177/10567895211013081 View at publisher
  • [Publication 3]: Nguyen, Hoang Anh Tuan; Niiranen, Jarkko. 2020. A second strain gradient damage model with an implementation for quasi-brittle materials with microarchitectures. SAGE. Mathematics and Mechanics of Solids, Volume 25, issue 3, pages 515-546. ISSN: 1081-2865.
    DOI: 10.1177/1081286519884695 View at publisher
  • [Publication 4]: Nguyen, Hoang Anh Tuan; Niiranen, Jarkko. 2021. Nonlocal continuum damage modeling for functionally graded plates of third-order shear deformation theory. Elsevier. Thin-walled Structures, Volume 164, page 107876. ISSN: 0263-8231.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202105196825
    DOI: 10.1016/j.tws.2021.107876 View at publisher

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https://urn.fi/URN:ISBN:978-952-64-0515-5

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[diss] Insinööritieteiden korkeakoulu / ENG