Lecture

Plasticity and Deformation in Metals

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In course

MSE-310: Deformation of materials

Présentation des mécanismes de déformation des matériaux inorganiques: élasticité, plasticité, fluage. ...

Description

This lecture covers the microscopic mechanisms of low temperature plasticity, plastic flow in single crystals, work hardening, plasticization criteria, and the mechanics of plastic deformation. It also discusses the critical stress state triggering plastic strain, deviatoric stresses in plasticity, and the von Mises criterion. The instructor explains the isotropic assumption, kinematic hardening, and the evolution of the load surface. The lecture delves into the significance of the coefficient k, the shape of the load surface, and the estimation of elastic limits under different stress conditions. It also explores obstacles to dislocation movements, isotropic and kinematic hardening, and the concept of equivalent deformations in plasticity.

Instructor

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.

Official source

Ontological neighbourhood

Chemical engineering

Materials science: Deformation of materials

Related concepts (32)

Cauchy stress tensor

In continuum mechanics, the Cauchy stress tensor , true stress tensor, or simply called the stress tensor is a second order tensor named after Augustin-Louis Cauchy. The tensor consists of nine components that completely define the state of stress at a point inside a material in the deformed state, placement, or configuration. The tensor relates a unit-length direction vector e to the traction vector T(e) across an imaginary surface perpendicular to e: or, The SI units of both stress tensor and traction vector are N/m2, corresponding to the stress scalar.

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.

Stress (mechanics)

In continuum mechanics, stress is a physical quantity that describes forces present during deformation. An object being pulled apart, such as a stretched elastic band, is subject to tensile stress and may undergo elongation. An object being pushed together, such as a crumpled sponge, is subject to compressive stress and may undergo shortening. The greater the force and the smaller the cross-sectional area of the body on which it acts, the greater the stress. Stress has units of force per area, such as newtons per square meter (N/m2) or pascal (Pa).

Creep (deformation)

In materials science, creep (sometimes called cold flow) is the tendency of a solid material to undergo slow deformation while subject to persistent mechanical stresses. It can occur as a result of long-term exposure to high levels of stress that are still below the yield strength of the material. Creep is more severe in materials that are subjected to heat for long periods and generally increase as they near their melting point. The rate of deformation is a function of the material's properties, exposure time, exposure temperature and the applied structural load.

Deformation (physics)

In physics and continuum mechanics, deformation is the transformation of a body from a reference configuration to a current configuration. A configuration is a set containing the positions of all particles of the body. A deformation can occur because of external loads, intrinsic activity (e.g. muscle contraction), body forces (such as gravity or electromagnetic forces), or changes in temperature, moisture content, or chemical reactions, etc. Strain is related to deformation in terms of relative displacement of particles in the body that excludes rigid-body motions.

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