Learning outcomes of the course unit
Knowledge and understanding:
At the end of this course the student should know the basics of machine design. He should gain understanding of the many factors affecting the design of mechanical parts with special regards to safety and reliability. He should be familiar with design schemes and checks required to analyze machine parts.
Applying knowledge and understanding:
He should be able to design a mechanical part on the basis of suitable material and process selection, load analysis and functional requirements. He should be able to select from catalogues the main mechanical components found in machines. He should be able to draw and dimension the part for production.
By the end of the course the student should be able to critically analyze machines and mechanical components and to their functions and requisites.
The student should be able to clearly present the functioning of mechanical devices and the design issues involved.
Strength of materials
Course contents summary
The course is divided in two parts: the design criteria against the main causes of failure and damage of mechanical parts are presented in the first part, the selection criteria and design check of mechanical elements are presented in the second part of the course.
Introduction to structural design, safety, safety factor, Technical
Mechanical tests on materials, tensile, hardness, impact, fatigue,
fracture, metallic materials (steel, cast iron, aluminum alloys,
magnesium, titanium, non-metallic materials (polymers and ceramics),
Manufacturing technology , Selection criteria.
Load analysis, statics, application of the beam model in mechanics, axial
load, bending load, shear load torsion. Stress and strain. Mohr circles.
Principal stresses, Strength criteria (Tresca, Von Mises, Rankine), ductility
and brittleness. Compression instability and Eulerian load. Stiffness.
Notches and stress concentration, nominal stress and local stress, stress
concentration factor Kt, Conforming and non-conforming contacts,
specific contact pressure, Hertzian theory, Contact stresses. Thermal
Fatigue of metallic materials, characteristics of the phenomenon, fatigue
experiments , fatigue limit, S / N curves , fatigue parameter estimates,
influencing factors, mean stress effect, fatigue damage accumulation,
multiaxial stress effect, notch sensitivity, notch factor Kf . Contact
fatigue, pitting, fretting.
Fixed connections , welding and bonding, technical standards, welded
joint design, weld types.
Non permanent connections, screws, bolts, rivets and nails, rules for
threaded connections, load transmission in shear or by friction, bolted
connections, preload, stiffness of the parts and load distribution, Fatigue
loading , self-locking devices.
Mechanical power transmission: axes and shafts, materials, construction
details, sizing and verification, shaft-hub connections, gears, pulleys.
Rolling bearings, types (rolls, balls) and load capacity, mounting, bearing
selection from the catalog. Bearings, examples, materials testing. Power
screws: Examples and thread types, checks.
Springs, fields of use, types, stiffness.
Juvinall Marshek “ Fundamentals of Machine Component Design” Wiley (2017)
Shigley’s “Mechanical Engineering Design (2015)
Course topics are presented through lectures and numerical exercises carried out in the classroom.
Every week a problem is proposed to be solved at home in small work groups and to be sent to the teacher before the discussion in the classroom.
The interest in the applications is motivated by allowing the individual study of malfunction or breakdown of a mechanical component to be proposed as one of the two topics for discussion at the oral examination.
Assessment methods and criteria
The exam consists of a open-book written test (3 and half hours) and an oral. The test results are are sent by e-mail.
The written part has to be evaluated at least sufficient to be admitted to the oral session. Two topics will be discussed during the oral session. One of the two topics can be optionally substituted by an individual project report.
Well-organized and complete notebooks and personal exercises influence positively the final grade.