Zwave Solutions Ltd

Montréal, Canada

Zwave Solutions Ltd

Montréal, Canada

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Portillo O.,Zwave Solutions Ltd | Cebon D.,University of Cambridge
Journal of Engineering Mechanics | Year: 2012

Finite-element analysis is used to model the failure of thin-film butt-joint specimens of pure bitumen in tension for a wide range of test conditions (temperature and strain rate). The approach uses a powerful numerical scheme based on two components: a nonlinear viscous, temperature- and rate-dependent constitutive material model that describes the mechanical deformation behavior of bitumen, implemented into a special-purpose finite-element user material subroutine, and a cohesive zone model for simulating the fracture process. The finite-element model is validated by comparing computed fracture characterization parameters with experimental results. The predicted force versus displacement characteristics and the normalized toughness, G/2h, are found to compare favorably with experimental results in the ductile and brittle regimes, with the failure mode being accurately simulated. © 2012 American Society of Civil Engineers.


Portillo O.,Zwave Solutions Ltd | Cebon D.,University of Cambridge
International Journal of Pavement Engineering | Year: 2014

The durability of asphalt pavements is strongly impaired by cracks, caused primarily by traffic loads and environmental effects. In this work, fracture behaviour of idealised asphalt mixes is investigated. Experiments on idealised asphalt mixes under pure-tension mode (mode I cracking) were performed and fracture parameters were evaluated. In these three-point bend fracture tests, the test variables were temperature and load rate. The test data were stored in an asphalt materials database and special-purpose tools were implemented to analyse and handle the laboratory data automatically. Fracture mechanism maps were constructed, showing the conditions associated with ductile, brittle and ductile-brittle transition regimes of behaviour. The mechanism maps show the failure response of the material in terms of the stress intensity factor, strain energy release rate and J-integral as a function of the temperature-compensated crack mouth opening strain rate. Fracture behaviour of asphalt mix specimens was simulated by cohesive zone model in conjunction with a novel material constitutive model for asphalt mixes. The finite element model agrees well with the experimental results and provides insights into fracture response of the notched asphalt mix beam specimens. © 2014 © 2014 Taylor & Francis.


Portillo O.,Zwave Solutions Ltd. | Cebon D.,University of Cambridge
Journal of Materials in Civil Engineering | Year: 2013

The fracture behavior of thin films of bitumen in double cantilever beam (DCB) specimens was investigated over a wide range of temperature and loading rate conditions using finite-element analysis. The model includes a phenomenological model for the mechanical behavior of bitumen, implemented into a special-purpose finite-element user material subroutine, combined with a cohesive zone model (CZM) for simulating the fracture process. The finite-element model is validated against experimental results from laboratory tests of DCB specimens by comparing measured and predicted load-line deflection histories and fracture energy release rates. Computer simulation results agreed well with experimental data of DCB joints containing bitumen films in terms of peak stress, fracture toughness, and stress-strain history response. The predicted "normalized toughness," G=2h, was found to increase in a power-law manner with effective temperaturecompensated strain rate in the ductile region as previously observed experimentally. In the brittle regime, G=2h is virtually constant. The model successfully captured the ductile and brittle failure behavior of bitumen films in opening mode (tension) for stable crack growth conditions. © 2013 American Society of Civil Engineers.


Portillo O.,Zwave Solutions Ltd | Cebon D.,University of Cambridge
Engineering Fracture Mechanics | Year: 2012

This work presents an experimental and numerical investigation to characterise the fracture properties of pure bitumen (the binder in asphalt paving materials). The paper is divided into two parts. The first part describes an experimental study of fracture characterisation parameters of pure bitumen as determined by three-point bend tests. The second part deals with modelling of fracture and failure of bitumen by Finite Element analysis. Fracture mechanics parameters, stress intensity factor, KIC, fracture energy, GIC, and J-integral, JIC, are used for evaluation of bitumen's fracture properties. The material constitutive model developed by Ossa et al. [40,41] which was implemented into a FE code by Costanzi [18] is combined with cohesive zone models (CZM) to simulate the fracture behaviour of pure bitumen. Experimental and numerical results are presented in the form of failure mechanism maps where ductile, brittle and brittle-ductile transition regimes of fracture behaviour are classified. The FE predictions of fracture behaviour match well with experimental results. © 2012 Elsevier Ltd.

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