The course is proposed to illustrate the mechanical behaviour of the metallic materials under different strains and environmental conditions. The interdisciplinary course will approach the metallurgical damage phenomena which can give rise to failures of mechanical devices in service, with special reference to the metallurgical characteristics affecting the behaviour of the materials. The most recent theories able to predict and describe the failures are presented. Cases of failure analysis will be discussed. Aim of the course is to illustrate the fundamental mechanisms that regulate the relation between mechanical-structural properties and resistance to the atmosphere of structural alloys for engineering. The student will be able to acquire good knowledge to choice and control of metallic materials for construction of mechanical components, according to the exercise conditions.
Study of the metallurgical damage phenomena which can give rise to failures of mechanical devices in service, with special reference to the metallurgical characteristics affecting the behaviour of the materials. The most recent theories able to predict and describe the failures are presented especially in reference to fracture mechanics, creep, corrosion and wear.
–) Fracture mechanics:
The yielding behaviour of metals in multiaxial stress fields; plastic deformation of polycrystalline materials; Linear elastic fracture mechanics (such as Griffith's criterion, Irwin's modification, Stress intensity factor, Strain energy release, Small scale yielding, Fracture toughness tests, Limitations ecc..); Fracture and types of fracture in metals; metallographic aspects of brittle and ductile fracture; dislocation theories of fracture; characteristic microstructural and morphological aspects; Elastic–plastic fracture mechanics (such as CTOD, R-curve, J-integral, Cohesive zone models, Transition Cracktip constraint under large scale yielding , R6 and EPRI method, Fracture toughness tests ecc..); Dinamic fracture in particular in reference to Fatigue failure (Morphology of the fracture surface, influence of the material, of the microstructure, of the surface conditions and of the environmental conditions. Corrosion fatigue. Fretting fatigue. Thermal fatigue ecc..); Examples of failure analysis.
–) Creep:
Creep and stress rupture. The high-temperature materials problem. The creep curve. Theories of low-temperature creep. Theories of high-temperature creep. Fracture at elevated temperature. Presentation of engineering creep data. Effect of metallurgical variables. Stress relaxation, C*.
–) Corrosion:
Corrosion damage of the mechanical parts. Corrosion mechanisms especially Stress corrosion cracking;
-)Wear:
Wear damage of the mechanical parts. Wear mechanisms: adhesive wear; tribo-oxidation; abrasive wear; contact fatigue. Wear processes: sliding wear; rolling wear; fretting; erosion. Wear tests. Engineering methods for prevention. Surface engineering: thermo-chemical treatments, surface coatings; surface analysis.
-)Failure analysis and test methods:
Fracture toughness tests,visual examination and optical microscope analysis, electronic microscope analysis, fractography, quantitative analysis, examples of failure analysis.
G.E. Dieter "Mechanical Metallurgy", Mc Graw Hill;
Ted L. Anderson "Fracture Mechanics: Fundamentals and Applications";
Frontal teaching combined with experimental activity in metallurgical laboratories
Oral test