The Swiss engineering master's degree

The course addresses fundamental and technical issues related to the design and maintenance of structures that shall not fail under cyclic loading. Students will be taught the principles of fatigue testing and fatigue failure analysis of mechanical structures, addressing the issues of how fatigue behavior is characterized, how fatigue failure is predicted, which physical mechanisms are responsible for the initiation and propagation of fatigue in various materials, with particular emphasis on metals and structural alloys, and how this behavior is related to the microstructure of the material.
This course will also present the most important applications of fatigue design in industry, including failure analysis, fatigue life calculation, experimental techniques, destructive and non-destructive methods of damage detection and characterization.

Requisiti

• Mathematics, Calculus and Mathematical Analysis
• Linear algebra and analytical geometry
• Material Science and Engineering
• Solid Mechanics
• Basics of mechanics of composite materials
• Basics of computational mechanics, including finite element methods

Obiettivi di apprendimento

• Understand the theory of fracture mechanics applied to brittle, ductile and quasi-brittle materials;
• Learn experimental techniques for the characterization of the propertie affecting crack onset and propagation;
• Understand the fatigue phenomenon of materials, including factors that affect the residual life of structures under cyclic loading and analytical methods for fatigue strenght assessment;
• Use computational mechanics as a tool to solve fracture mechanics problems and prediction of fatigue life;
• Apply the knowledge of fatigue and fracture mechanics in the design of structures and to investigate possible causes of structural failure;

Contenuti del modulo

Introduction to Fracture Mechanics

Linear Elastic Fracture mechanics

• Griffith’s analysis, 1st law of thermodynamics and crack growth, Energy release rate (ERR)
• Stress analysis and stress intensity factor (SIF). Failure modes (mode I, II and III)
• Relation between the SIF and ERR
• Mixed-mode propagation
• Plane stress, plane strain, R-curve, and stability of the propagation
• Experimental determination of the Fracture toughness: standard and non-standard methods

Elasto-plastic fracture mechanics

• Crack opening displacement (COD)
• J integral
• Relation between J-integral, COD and ERR

Fatigue of metals, plastic and composite materials

• Fatigue limit
• Factors affecting the crack propagation process
• Fatigue in brittle and ductile solids
• Low Cycle Fatigue and High Cycle Fatigue: application of strain- or stress-life approach in different scenarios
• Analytical and numerical methods for fatigue strength assessment
• Fatigue and random vibration analyses
• Fatigue of welded structures
• Fatigue of composite and plastic materials
• Experimental assessment of the fatigue behaviour
• Application of the theory concepts to the fatigue strength assessment in real industrial case studies

Computational fracture mechanics

• Determination of the SIF
• Determination of the J-Integral
• Virtual Crack Closure technique
• Cohesive elements

Metodologie di insegnamento e apprendimento

• Lectures in presence
• Tutorial in presence
• Self-study

Bibliografia

Lecture notes and learning material will be distributed to students during the semester, along with references to books and scientific papers for the specific topics discussed.