A hyperplasticity framework for efficient modelling of cyclic loading ratcheting

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• Dr Christelle Abadie, CUED
• Friday 20 January 2023, 14:00-15:00
• Oatley Seminar Room, Department of Engineering.

If you have a question about this talk, please contact Hilde Hambro.

Modelling of the non-linear response on loading, hysteretic behaviour on unloading and reloading, and the phenomenon of ratcheting under very many cycles is a challenge. First, because of the non-linearity and the difficulties in devising a plasticity model that is thermodynamically robust, but mostly, because of the computational cost involved in modelling large number of cycles. This talk presents a theoretical framework to describe the response of a one dimensional mechanical system under cyclic loading. The methods are formulated within the hyperplasticity framework, which is first detailed and explained. The model can be expressed in the form of general incremental relationships, can therefore be applied without modification directly to any loading history, and can be readily implemented within a time-stepping numerical code. A rigorous procedure is described to accelerate the ratcheting process, so that the effects of very large numbers of cycles can be analysed through a reduced number of cycles. A generalisation from unidirectional to multidirectional loading is described, together with a tensorial form for application to material modelling. The original motivation was for the application to design of piles under lateral loading, and an example of this application will be presented. However, the model is equally applicable to many other problems involving uni-directional or bi-directional cyclic loading in which the system exhibits a similar character of hysteretic behaviour, with ratcheting under large numbers of cycles.

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Dr. Christelle Abadie is an assistant professor in civil engineering at the University of Cambridge. She holds an Engineering degree from the French “Grandes Ecoles” ENSTA ParisTech, and a D.Phil from the University of Oxford. During her PhD, she studied the response of monopile foundations to long-term cyclic lateral loading (HARM model), and continued studying offshore wind monopiles through a PDRA at Oxford, working on the PISA2 project (Pile Soil Analysis). Her current research activities focus on geotechnics for sustainable infrastructure development in the context of climate change and include pile design under seismic loads for wind energy applications, onshore wind turbine foundation design and sensing of climate-change induced geo-hazards. Christelle works with a range of industry partners, in order to ensure knowledge transfer from academia to practice. She is a fellow of Fitzwilliam College and the academic representative of the Offshore Engineering Society.

This talk is part of the Engineering - Mechanics and Materials Seminar Series series.

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