Ing Ind - Inf (Mag.)(ord. 270) - MI (491) MATERIALS ENGINEERING AND NANOTECHNOLOGY - INGEGNERIA DEI MATERIALI E DELLE NANOTECNOLOGIE

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A

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054191 - MECHANICAL BEHAVIOUR AND FAILURE OF METALS

U2E

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ZZZZ

096246 - MECHANICAL BEHAVIOUR AND FAILURE OF METALS

Obiettivi dell'insegnamento

The main objective of the course is to provide the students with the necessary tools for the basic design and assessment of machine components, both under static and fatigue loading. The basics of mechanical design are upgraded in order to include design methods for static and fatigue loads and tools for assessing the influence of defects on static and fatigue strength.

Theory of elasticity is extended in order to evaluate stresses in presence of notches by the definition of theoretical stress concentration factor and to evaluate the initial yielding and the fully plastc collapse. Composite materials are introduced and in particular the concept of anisotropic Hooke's law, orthotropic materials, elastic modulus parallel and transverse to fibres, failure criteria for orthotropic materials are given.

Risultati di apprendimento attesi

The students will possess the knowledge of the main tools used for the basic design and assessment of machine components subjected to static and fatigue loading. Thanks to the practices that are focussed on case studies, the students will improve the skills necessary for practical design application. The case studies will provide the capability to approach the solution of a problem and critically discuss the results. An intermediate homework that the students are asked to write will improve the capability on writing a technical report.

Argomenti trattati

LECTURES:

-Stress-strain equations and models: review of elastic deformation (elastic constants, Hooke’s law, Volumetric strain and hydrostatic stress) and plastic deformation (stress-strain models, unloading and reloading response of models)

-Mechanical testing: tension test (engineering stress-strain properties, strength, ductility, necking, hardening, true stress-strain curves); compression test; bending and torison test.

-State of stress and strain: review of principal plane and three-dimensional states of stresses (Normal, shear stresses) Yielding and fracture under combined state of stresses: maximum normal stress fracture criterion; maximum shear stress yield criterion; octhaedral shear stress yield criterion.

-Notches: definition of theoretical stress concentration factor and experimental stress concentration factor; elastic behaviour and initial yielding; fully plastic yielding; Neuber rule to estimate notch stress and strain.

-Linear-elastic fracture mechanics: effect of cracks on strength; strain energy release rate; stress intensity factor, fracture toughness of materials; effect of thickness; plastic zone near the crack tip (plane stress and strain); fully plastic loads

-Fatigue of materials: introduction and definitions; stress based approach (Wöhler curves, fatigue limits, factors affecting long life fatigue strength); notch effect and sensitivity; mean stress effect. Strain based approach to fatigue: cyclic behaviour of materials; strain-life tests (Coffin-Manson equations); trends for engineering materials, factors affecting strain-life curves; mean stress effect.

-Fatigue crack growth: fatigue crack growth testing; Paris law; trends with materials; life estimates for constant amplitude loading.

-Composite materials: introduction; anisotropic Hooke’s law; orthotropic materials; elastic modulus parallel to fibers; elastic modulus transverse to fibers; fracture criterion for orthotropic materials.

EXPERIMENTAL LABORATORIES: Fracture mechanics.

Prerequisiti

The courses assumes that the students already possess the basic knowledge of Mechanics of Structures and Basic Machine Design, including kinematic analysis and solutions of beams, De Saint-Venant cases, 2D stress and strains analysis, failure theories and assessment under static loading.

Modalità di valutazione

The exam is based on a compulsory written test with a maximum score of 27

An optional homework is evaluated with a maximum score of 3

The oral is on request with a maximum score of 2

Bibliografia

N.Dowling, Mechanical behavior of materials, Editore: Prentice Hall, Anno edizione: 2000
L. Vergani, Meccanica dei Materiali, Editore: McGraw-Hill, Anno edizione: 2001

Software utilizzato

Nessun software richiesto

Forme didattiche

Tipo Forma Didattica

Ore di attività svolte in aula

(hh:mm)

Ore di studio autonome

(hh:mm)

Lezione

32:30

48:45

Esercitazione

17:30

26:15

Laboratorio Informatico

0:00

0:00

Laboratorio Sperimentale

0:00

0:00

Laboratorio Di Progetto

0:00

0:00

Totale

50:00

75:00

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