Lecture

Fracture and Toughness of Materials

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In course

MSE-101(b): Materials:from chemistry to properties

Ce cours permet l'acquisition des notions essentielles relatives à la structure de la matière, aux équilibres et à la réactivité chimique en liaison avec les propriétés mécaniques, thermiques, électriques, magnétiques et optiques des matériaux. ...

Description

This lecture covers the concepts of fracture and toughness of materials, focusing on the stress intensity factor, surface energy, and crack propagation. The instructor explains the relationship between surface energy, elastic modulus, and the critical stress for crack advancement. The lecture also discusses the differences in behavior between ideal elastic materials and those with plasticity, highlighting the importance of toughness in material resistance. Various material properties such as ductility, plasticity, and fracture toughness are explored, providing insights into the mechanisms governing material failure.

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Instructors (4)

Roland Logé

Roland Logé is an associate professor at EPFL, with a primary affiliation to the Materials Institute, and a secondary affiliation to the Microengineering Institute. After graduating in 1994 at UCL (Belgium) in Materials Engineering, he earned a Master of Science in Mechanics in 1995, at UCSB Santa Barbara (USA). He received his PhD at Mines Paristech-CEMEF (France) in 1999, where he specialized in metal forming and associated microstructure evolutions. After a postdoc at Cornell University (USA) between 1999 and 2001, he entered CNRS in France. In 2008, he was awarded the ALCAN prize from the French Academy of Sciences, together with Yvan Chastel. In 2009 he became head of the Metallurgy-Structure-Rheology research group at CEMEF. In 2011, he launched a “Groupement de Recherche” (GDR), funded by CNRS, networking most of the researchers in France involved in recrystallization and grain growth. In 2013, he became Research Director at CNRS. In March 2014 he joined EPFL as the head of the Laboratory of Thermomechanical Metallurgy.

Michel Rappaz

After a PhD in solid state physics (1978) at the Ecole Polytechnique Fédérale de Lausanne (EPFL) and a post-doc at Oak Ridge National Laboratory, Michel Rappaz joined the Institute of Materials of EPFL in 1981. After two years in an engineering company, he came back to EPFL in 1984 where he was nominated Adjunct Professor in 1990 and Full Professor in 2003. He retired from EPFL in 2015 and is now Emeritus Professor and independent consultant for several industries and research centres. His main interests are in phase transformations and solidification, in particular the coupling of macroscopic aspects of heat and mass transfer with microscopic aspects of microstructure and defect formation. Among his diverse achievements, one can mention in particular the development of cellular automata for grain structure predictions and of granular models for hot tearing formation in castings, the coupling of Finite Element method with microscopic models of nucleation and growth, the application of the phase field method to the understanding of various microstructures, the discovery of quasicrystal mediated-nucleation in alloys, and many other studies both fundamental at the microstructure-defect level and more applied at the level of processes. Some of the software developments have been commercialized by a spin-off company founded by his group in 1991 (Calcom SA), now part of the French company ESI. Michel Rappaz initiated in 1992 an annual postgraduate course on solidification which has been attended by more than 900 participants from all over the world. He is presently collaborating closely with another spin-off company started from his group, Novamet SàrL. Michel Rappaz has received several awards, in particular the Mathewson co-author award (1994) and author award (1997) of the American Mineral, Metals and Materials Society (TMS), the Koerber foundation award jointly with Profs Y. Bréchet and M. Asbby (1996), the Sainte-Claire Deville Medal (1996) and the Grand Medal (2011) from the French Materials Society, the Bruce Chalmers Award of TMS (2002), the Mc Donald Memorial Lecture award of Canada (2005), the FEMS European Materials Gold Medal (2013) and the Brimacombe Prize of TMS (2015). He is a highly-cited author of ISI, a fellow of ASM, IOP and TMS, and has co-authored more than 200 publications and two books.

Official source

Ontological neighbourhood

Chemical engineering

Materials science: Deformation of materials

Related concepts (32)

Strength of materials

The field of strength of materials (also called mechanics of materials) typically refers to various methods of calculating the stresses and strains in structural members, such as beams, columns, and shafts. The methods employed to predict the response of a structure under loading and its susceptibility to various failure modes takes into account the properties of the materials such as its yield strength, ultimate strength, Young's modulus, and Poisson's ratio.

Material

Material is a substance or mixture of substances that constitutes an object. Materials can be pure or impure, living or non-living matter. Materials can be classified on the basis of their physical and chemical properties, or on their geological origin or biological function. Materials science is the study of materials, their properties and their applications. Raw materials can be processed in different ways to influence their properties, by purification, shaping or the introduction of other materials.

Materials science

Materials science is an interdisciplinary field of researching and discovering materials. Materials engineering is an engineering field of finding uses for materials in other fields and industries. The intellectual origins of materials science stem from the Age of Enlightenment, when researchers began to use analytical thinking from chemistry, physics, and engineering to understand ancient, phenomenological observations in metallurgy and mineralogy. Materials science still incorporates elements of physics, chemistry, and engineering.

Fracture

Fracture is the separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. If a displacement develops perpendicular to the surface, it is called a normal tensile crack or simply a crack; if a displacement develops tangentially, it is called a shear crack, slip band or dislocation. Brittle fractures occur without any apparent deformation before fracture.

Elastic modulus

An elastic modulus (also known as modulus of elasticity) is the unit of measurement of an object's or substance's resistance to being deformed elastically (i.e., non-permanently) when a stress is applied to it. The elastic modulus of an object is defined as the slope of its stress–strain curve in the elastic deformation region: A stiffer material will have a higher elastic modulus. An elastic modulus has the form: where stress is the force causing the deformation divided by the area to which the force is applied and strain is the ratio of the change in some parameter caused by the deformation to the original value of the parameter.

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Fabien Sorin

Sep 2002-Oct 2007 Ph.D., Department of Materials Science and Engineering, MIT, USA. Supervisor: Prof. Yoel Fink; Thesis: Multi-material, Multifunctional Fiber Devices. After graduating with an engineering degree and a Master of Science in Physics from the Ecole Polytechnique in Palaiseau, France, Prof. Sorin joined the department of Materials Science and Engineering at the Massachusetts Institute of Technology (MIT) in Cambridge, USA for his graduate studies. He worked as a research assistant in the Photonic Bandgap Fibers and Devices Group of Professor Yoel Fink and graduated with a PhD in 2008. His PhD thesis led to the development of a new class of fiber material and devices and he was a pioneer of the field of multi-material fibers. Mar 2008-Oct 2010 Postdoctoral Associate and Research Scientist, Research Laboratory of Electronics, MIT. He then joined the Research Laboratory of Electronics at MIT as a Postdoctoral Associate, and continued as a Research Scientist associate, where he conducted independent research in the emerging field of multi-material fibers and was involved and led a variety of projects in fundamental research as well as in collaborations with local start-ups. Apr 2011 Feb 2013 Research Engineer, Saint-Gobain Recherche, Aubervilliers, France. Surface du Verre et interface Group In 2011, prof. Sorin returned to Europe and joined the company Saint-Gobain in the Saint-Gobain Recherche center, its biggest research center located near Paris in France. As a research engineer, he developed a new research thrust investigating new photonic materials and nanostructures for the energy and building industries. In particular, he and colleagues developed innovative processing approaches to deploy photonic nanostructures for light management over large area substrates, for applications in energy harvesting and saving, and for building materials and windows. Mar 2013 Present Assistant Professor tenure-track, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland. Head of the Photonic materials and fibre devices laboratory (FIMAP) Since March 2013, he is in the department of Materials Science (IMX) at the Ecole Polytechnique Fédérale de Lausanne (EPFL) as an assistant professor tenure-track. He is starting a research group on photonic materials and fiber devices (FIMAP), continuing on developing innovative materials processing approaches and photonic device architectures to develop new solutions in energy harvesting, saving and storage, in sensing and monitoring, health care and smart fabrics.

Related concepts (32)

Strength of materials