Ifsttar PhD subject

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Title : Variational approach to model fracture in viscoelastic materials of bituminous type

Main host Laboratory - Referent Advisor MAST - LAMES  -  CHUPIN Olivier      tél. : +33 240845786

Director of the main host Laboratory VILLAIN Géraldine  -

Laboratory 2 - Referent Advisor MAST - MIT  -  HAMMOUM Ferhat  -    -  tél. : +33 240845767

PhD Speciality Mécanique

Axis of the performance contract 2 - COP2017 - More efficient and resilient infrastructure

Main location Nantes

Doctoral affiliation ECOLE CENTRALE NANTES

PhD school Sciences de l'Ingénierie et des Systèmes (SIS)

Planned PhD supervisor HAMMOUM Ferhat  -  Université Gustave Eiffel  -  MAST - MIT

Planned financing Contrat doctoral  - Ifsttar

Abstract

The deterioration of pavement due to the fracturing of layers made of bituminous materials is a significant challenge, necessitating a deeper understanding of the associated mechanisms and factors. Addressing this issue involves the development of essential theoretical models and numerical tools. Bituminous materials are widely acknowledged for their viscoelastic characteristics, forming the core focus of this thesis. In this context, the present thesis focuses on the cracking of viscoelastic materials in a quasi-static setting. A novel, thermodynamically consistent variational approach is introduced to model damage within viscoelastic solids. This approach enables the integration of local constitutive equations into a global incremental potential, the minimization of which yields the solution to the mechanical problem. To overcome the spurious mesh-dependent results associated with softening damage models, the lip-field approach has been used to regularize the problem. A detailed numerical implementation for both one-dimensional (1D) and two-dimensional (2D) scenarios is presented, complemented by Python-based finite element (FE) codes. The simulation results for the 2D case show the ability of the model to fit experimental force-displacement curves (for mode-I fracture) and to predict the crack paths (for mixed mode fracture). This work not only provides a robust theoretical and numerical foundation for potential future applications in pavement mechanics but also extends its relevance beyond bituminous materials. The methodology developed here can be applied effectively to model cracking in various viscoelastic materials.

Keywords : Damage, Fracture, Viscoelasticity, Lip-field approach, Bituminous materials, Variational approach

Main host Laboratory - Referent Advisor	MAST - LAMES - CHUPIN Olivier tél. : +33 240845786
Director of the main host Laboratory	VILLAIN Géraldine -
Laboratory 2 - Referent Advisor	MAST - MIT - HAMMOUM Ferhat - - tél. : +33 240845767
PhD Speciality	Mécanique
Axis of the performance contract	2 - COP2017 - More efficient and resilient infrastructure
Main location	Nantes
Doctoral affiliation	ECOLE CENTRALE NANTES
PhD school	Sciences de l'Ingénierie et des Systèmes (SIS)
Planned PhD supervisor	HAMMOUM Ferhat - Université Gustave Eiffel - MAST - MIT
Planned financing	Contrat doctoral - Ifsttar
Abstract The deterioration of pavement due to the fracturing of layers made of bituminous materials is a significant challenge, necessitating a deeper understanding of the associated mechanisms and factors. Addressing this issue involves the development of essential theoretical models and numerical tools. Bituminous materials are widely acknowledged for their viscoelastic characteristics, forming the core focus of this thesis. In this context, the present thesis focuses on the cracking of viscoelastic materials in a quasi-static setting. A novel, thermodynamically consistent variational approach is introduced to model damage within viscoelastic solids. This approach enables the integration of local constitutive equations into a global incremental potential, the minimization of which yields the solution to the mechanical problem. To overcome the spurious mesh-dependent results associated with softening damage models, the lip-field approach has been used to regularize the problem. A detailed numerical implementation for both one-dimensional (1D) and two-dimensional (2D) scenarios is presented, complemented by Python-based finite element (FE) codes. The simulation results for the 2D case show the ability of the model to fit experimental force-displacement curves (for mode-I fracture) and to predict the crack paths (for mixed mode fracture). This work not only provides a robust theoretical and numerical foundation for potential future applications in pavement mechanics but also extends its relevance beyond bituminous materials. The methodology developed here can be applied effectively to model cracking in various viscoelastic materials.
Keywords :	Damage, Fracture, Viscoelasticity, Lip-field approach, Bituminous materials, Variational approach

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