5 lectures

5 Lectures (1h30)

Lecture 1: Experimental methods and measurement technics at high strain-rates

Dr. Egil Fagerholt, Dep. of Structural Engineering, Norwegian University of Science and Technology

The lecture will focus on measurement techniques for kinematic measurements in mechanical testing, with emphasis on high strain-rate applications. Both conventional and state-of-the art techniques will be covered, with a focus on camera-based measurement techniques, such as Digital Image Correlation. The Limitations and advantages of the different techniques in the scope of high strain-rate applications will be addressed. Inverse modeling techniques, such as the Virtual Fields Method will be briefly discussed in terms of the different measurement techniques.

 Lecture 2: Impact and shock physics

Dr. Daniel Eakins, Dep. of Engineering Science, University of Oxford, Impact Laboratory

This 2-part lecture will provide an introduction to the behaviour of materials under shock compression and release. Part 1 will present an overview of the thermodynamics of shock loading, wave propagation and interaction, strength effects, and failure mechanisms, with emphasis on the weak-shock regime. The second part will focus on current and emergent diagnostic techniques for studying different aspects of material response under extreme conditions.

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Lecture 3: Plasticity and failure in ductile materials

Pr. Dirk Mohr,  Dep. of Mechanical and Process Eng., ETH Zürich

The first part of the lecture "Plasticity and failure in ductile materials" provides an overview on basic plasticity models that are suitable for describing the deformation response of polymers and metals under normal and extreme loading conditions (large strains, high strain rates and high temperatures). The identification of the model parameters based on static and dynamic experiments is discussed. Subsequently, recent developments are discussed, in particular the potential of machine learning in the context of plasticity model. The second part of this lecture is concerned with ductile failure. Here, micromechanics-based void growth models will be introduced as well as purely phenomenological damage indicator models. The hybrid experimental-numerical characterization of the stress-state (triaxiality and Lode parameter), strain rate and temperature dependent fracture response of metals is discussed. Towards the end of this lecture, examples of finite element simulations are shown involving large deformation and plasticity during impact loading.

Lecture 4: Discrete numerical methods for damage and fracture simulation in dynamic

Dr. Jeremie Girardot,  Arts et Métiers Institute of Technology, I2M Bordeaux

This lecture will deal with a specific numerical approach which is more and more used in the field of dynamic simulation. The first part will consist on presenting basics of the Discrete Element Method (DEM) regarding the classical continuum mechanics and how it can be a good choice for dynamic problems. The second part will explore numerical techniques within the DEM that can be set in order to simulate damage, fracture, fragmentation under dynamic loadings and will present the most used models in the litterature. It will be seen also that the discrete paradigm can be very convenient to take into account variabilities like material heterogeneities or porosities. Finally, several illustration cases will be examined in order to conclude on the usefulness of this approach. Some comparisons with continuous simulation will be analyzed and discussed and recent works on different kind of material will also be presented.

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Lecture 5: Dynamic fragmentation in brittle solids: experimantal approaches and modelling

Pr. P. Forquin, PhD students M. Blasone, M. Dargaud, D. Georges,  3SR Lab., Univ. Grenoble Alpes

This lecture will be dedicated to the experimental analysis and numerical modelling of dynamic fragmentation in brittle solids. In particular, the first part will be dedicated to the basis of single and multiple fragmentation modelling (critical defects, crack triggering, crack propagation) and the main related predictions in terms of cracking density, influence of loading rate, distribution of fragments. The second part will focus on the use of X-ray tomography analysis to develop a continuous or discrete modelling of the fragmentation process. A particular attention will be given to the relationship between microstructure, fragmentation properties and macroscopic behaviour of the brittle solids.

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