|SCIENTIFIC DISCIPLINARY SECTOR||ING-IND/14|
The course aims to provide students with tools and criteria for structural analysis and design (design for static strength, in presence of creep, against brittle fracture, in presence of fatigue, against instability) and with methodologies and instruments for the analysis and structural design of the main mechanical members.
Furthermore the course aims to introduce students in methods that allow the engineer to go from idea to executive design of an industrial product, to provide the knowledge required for classification, representation and choice of standard components and to explain the basics of the product-oriented design.
The course aims to provide students with knowledge and understanding of the criteria of structural design (for static strength, in presence of creep, against brittle fracture, in presence of fatigue, against instability) and with methodologies and instruments for the analysis and structural design of the main mechanical members.
Furthermore the course aims to introduce students to product design, with particular reference to the design process and to design for safety, for manufacturability, for cost, for assembly and for environment.
Lectures and practice integrated with lectures.
1st part – Fundamentals of machine design
Mechanics of solids and structures
Stresses and strains in solids (recalls). Principal stresses (recalls). Special problems of solid mechanics. Plane strain and plane stress problems. Special problems of structural mechanics. Beam theory (recalls). Curved members in flexure. Membrane theory for thin axisymmetric cylindrical and spherical shells. Contact stresses.
2nd part – Criteria of structural design
Static strength of materials. Ideal or equivalent stress. Strength criteria for ductile materials. Strength criteria for brittle materials. Safety condition: Limit stress, Safety factor, Admissible stress, Safety margin (grade). Notches and their effect. Elastic and experimental stress concentration factor. Safety condition in presence of notches.
Fatigue in metallic materials. Fatigue spectra. High cycle fatigue: Wöhler curves; Influence of the mean stress; Notches and their influence; Size factor; Surface factor. Safety condition for stresses of constant amplitude. Safety condition for stresses of variable amplitude: Cumulative damage.
Brittle fracture in presence of cracks. Linear elastic fracture mechanics (LEFM): Stress intensification factor; Plastic zone at the crack tip; Fracture toughness. Safety condition according to LEMF criteria. Crack propagation by fatigue (outline).
Creep in metallic materials. Creep tests. Larson Miller parameter. Safety condition in presence of creep.
Long columns with central loading
Euler column formulas. The “ k “ method.
3rd part – Design of mechanical elements
Vessels and pipes
Cylindrical vessels and pipes. Spherical vessels. Vessels for high pressures.
Disks of constant thickness. Disk with crown and hub.
Connections that cannot be dismantled
Weldings. Riveted joints. Glued on joints. Forced connections.
Connections that can be dismantled
Threads. Power screws. Threaded connections. Set screws (outlines). Elements for transmitting motion between co-axial members (outlines): Gib-head keys; Woodruff keys; Pins.
Elements for power transmission and lifting
Gears. Flexible elements (outlines): Belts; Wire ropes; Chains.
Members for storage or transfer of energy associated to rotating motion (outlines)
Brakes. Clutches. Flywheels.
Rolling contact bearings. Principles of hydrodynamic lubrication (outlines); Journal bearings.
Axles and shafts
Static design. Dynamic design.
Members for the motion transformation
Crankshafts. Connecting rods.
4th part – Elements of product design
Design for safety; Design for manufacturability; Design for cost; Design for assembly; Design for environment.
Teacher’s lecture notes.
De Paulis A., Manfredi E., Costruzione di macchine, Pearson Italia, Milano, 2012
Chirone, E., Tornincasa, S., Disegno tecnico industriale, Ed. Il Capitello - Torino, 2011
Medri G., Cenni di progettazione di prodotto, Liguori Editore, 2008
Office hours: Office hours:The lecturer is available for the students at the end of each lesson. Meetings can be scheduled via MS Teams, at DIME Sezione Mec - Via all’Opera Pia 15/A or at the Polo didattica – La Spezia. In addition, it is always possible to request for a meeting via email. For appointments, please send an email to: email@example.com
Office hours: The teacher is available for the students at the end of lessons and by appointment (face-to-face or Teams meeting)
MASSIMILIANO AVALLE (President)
MARGHERITA MONTI (President Substitute)
All class schedules are posted on the EasyAcademy portal.
Written and oral examination. The written test regards the solution of one or two exercises. The oral examination consists of one or two questions on theory. A positive evaluation of the written test is a necessary condition to access the oral examination.