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Séance de cours

Plasticité: ingénierie vs vrai stress et contrainte

Description

Cette séance de cours traite de la différence entre l'ingénierie et les véritables mesures de stress et de contraintes, en se concentrant sur le processus de conversion et les implications pour le comportement des matériaux. Il couvre les mesures de contrainte obtenues à partir des courbes contrainte-déformation, les formules de conversion et l'utilisation de modèles de durcissement de la loi de puissance. L'instructeur explique l'importance de mesurer le stress d'ingénierie uniaxiale par rapport à la souche en laboratoire et la transition vers le vrai stress par rapport à la souche. La séance de cours se termine par un exemple pratique comparant le vrai comportement du matériau avec le comportement de l'ingénierie, soulignant l'importance de modèles de matériaux précis pour des problèmes d'ingénierie complexes.

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Enseignant·e·s (3)

William Curtin

John Martin Kolinski

Dr. Kolinski studied Applied Mathematics (Sc.M.) and Applied Physics (Ph.D.) at Harvard University, completing a PhD under the supervision of L. Mahadevan and Shmuel Rubinstein on the role of air in droplet impact. John did his post-doc at the Hebrew University of Jerusalem in Israel supported by the Fulbright post-doctoral fellowship. At HUJI, he worked on interfacial instabilities in soft matter in the labs of Eran Sharon and Jay Fineberg. John continues his research into interfacial mechanics at EPFL in EMSI, his newly founded laboratory for the study of Engineering Mechanics of Soft Interfaces.

John Botsis

John (Ioannis) Botsis obtained his diplôme in civil engineering at the University of Patras, Greece in 1979. He continued his education at Case Institute of Technology in Cleveland Ohio/USA, where he received his MS and Ph.D. in 1984. After two years at the research center for national defense in Athens he was nominated assistant professor at the University of Illinois in Chicago, associate in 1991 and full professor in 1995. In 1996, he was nominated professor of solids and structural mechanics at the EPFL. At EPFL he teaches mechanics of structures and mechanics of continuous media´ at the bachelors level and Fracture mechanics at the masters and doctoral levels. His research covers the mechanics of solids and structures, fracture mechanics and micromechanics of polymers, metals and their composites as well as biomechanics. He is also actively involved in full-filed optical methods for surface strain measurements as well as internal strain measurements using fiber Bragg grating sensors, aimed at characterizing micromechanics of fracture, residual strains and strain distribution in composite laminates for structural monitoring. Funding for his research comes from the Swiss National Science Foundation, State Secretariat for Education and Research and Swiss industry. He retired on February 28, 2020.

Source officielle

Proximité ontologique

Génie chimique

Science des matériaux: Deformation of materials

Concepts associés (23)

Stress–strain curve

In engineering and materials science, a stress–strain curve for a material gives the relationship between stress and strain. It is obtained by gradually applying load to a test coupon and measuring the deformation, from which the stress and strain can be determined (see tensile testing). These curves reveal many of the properties of a material, such as the Young's modulus, the yield strength and the ultimate tensile strength. Generally speaking, curves representing the relationship between stress and strain in any form of deformation can be regarded as stress–strain curves.

Deformation (engineering)

In engineering, deformation refers to the change in size or shape of an object. Displacements are the absolute change in position of a point on the object. Deflection is the relative change in external displacements on an object. Strain is the relative internal change in shape of an infinitesimally small cube of material and can be expressed as a non-dimensional change in length or angle of distortion of the cube. Strains are related to the forces acting on the cube, which are known as stress, by a stress-strain curve.

Stress–strain analysis

Stress–strain analysis (or stress analysis) is an engineering discipline that uses many methods to determine the stresses and strains in materials and structures subjected to forces. In continuum mechanics, stress is a physical quantity that expresses the internal forces that neighboring particles of a continuous material exert on each other, while strain is the measure of the deformation of the material. In simple terms we can define stress as the force of resistance per unit area, offered by a body against deformation.

Finite strain theory

In continuum mechanics, the finite strain theory—also called large strain theory, or large deformation theory—deals with deformations in which strains and/or rotations are large enough to invalidate assumptions inherent in infinitesimal strain theory. In this case, the undeformed and deformed configurations of the continuum are significantly different, requiring a clear distinction between them. This is commonly the case with elastomers, plastically-deforming materials and other fluids and biological soft tissue.

Résistance des matériaux

vignette|Essai de compression sur une éprouvette de béton, une pression croissante est appliquée verticalement sur l'échantillon pendant que deux appareils mesurent les déformations longitudinales et transversales de l'éprouvette. vignette|À l'issue du test, l'éprouvette s'est rompue. Notez la cassure longitudinale. La résistance des matériaux (RDM) est une discipline particulière de la mécanique des milieux continus, permettant le calcul des contraintes et déformations dans les structures des différents matériaux (machines, génie mécanique, bâtiment et génie civil).

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Explore les contraintes critiques, la mécanique de flexion et le calcul des contraintes dans les sondes flexibles.

Modèles de dommages au continuum orthotrope

Explore les modèles de dommages continus orthotropes, le comportement stress-souche, la représentation des fissures et la simulation de béton.

Réponse matérielle : FCC-BCC-HCP Connectez-vous à Mediaspace pour regarder cette vidéo

Explore la réponse du matériau à l'impact et au durcissement par déformation, y compris les bandes de cisaillement adiabatiques et leurs applications.

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Concepts associés (23)

Stress–strain curve

Deformation (engineering)

Stress–strain analysis

Finite strain theory

Résistance des matériaux

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