|SCIENTIFIC DISCIPLINARY SECTOR||ING-IND/14|
|MODULES||This unit is a module of:|
The objective of this course is to provide the concepts, procedures, decision analysis techniques necessary to design machine elements commonly found in mechanical devices.
The course aims to provide students of the knowledge and understanding of the criteria of structural design of the main mechanical members.
The aim is to introduce the student to Machine Design as a branch of Mechanics that tackles structural and resistance problems of mechanical components, focusing on the design of the single machine part and providing hints on the design choices of a machine in its entirety.
Attendance to lectures and guided exercises and individual study will allow the student to:
learn the general aspects of Machine Design
learn the computation methods of these elements when subjected to static and dynamic loads
identify the structural criticalities of the machine parts and outline constructive measures to avoid or at least reduce them
master the use of the mechanical characteristics of the materials most used in the mechanical and structural fields, making use of both pre-existing databases and interpretation of experimental results, and simplified methods validated also at a regulatory level
understand the reliability of the results obtained with conventional computation methods
know how to extend the principles learned to new elements, not covered in the course
The lectures and the practical exercise classes, showing real engineering examples, are aimed at showing the ways of simplifying a real object in an appropriate model, for which explicit computations can be carried out through analytical formulas. By consulting appropriate diagrams, the criticalities of the structures, both in the static and dynamic field, are highlighted, taking as case study examples various numerical analyzes on components of mechanical, naval, civil and biomechanical types. In this way, the students are encouraged to learn the skill of extrapolating and generalizing from the specific problem to problems never faced. All the diagrams concerning the mechanical characteristics of the materials are built step by step, starting from real data deriving from experimental tests.
1st part – Fundamentals of machine design: recalls
Equation of the elastic line.
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.
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.
Long columns with central loading. Euler column formula.
3rd part – Shafts and associated parts; keys, Woodruff keys, pins
Thin-walled vessel design
J.E. Shigley, “Mechanical Engineering Design”, MCGraw-Hill
R.E. Peterson, “Stress Concentration factors”, Wiley-Interscience Publication
R.C. Juvinall, “ Fundamentals of machine component design”, John Wiley & Sons
Office hours: The teacher is available for the students at the end of lessons and by appointment (face-to-face or Teams meeting)
MARGHERITA MONTI (President)
ROBERTO RAZZOLI (President Substitute)
All class schedules are posted on the EasyAcademy portal.
The exam includes a written test and an oral test.
The written test consists of an exercise to be solved within 2 hours. During the test, only the use of the calculator is allowed. Smartphones have to be switched off.
Those who obtain a score of at least 18/30 for the written test can access the oral exam. Those who do not pass the written test have to repeat it in any official scheduled date.
The oral exam, which can be held within a calendar year after passing the written test, includes two questions: one on the topics of Machine Design and one for those of Machine Drafting. A failed oral exam does not invalidate the written test which can be reused in the future (within one year).
The final mark is given by the average of the marks of the oral and written tests: if it is a decimal, it is rounded to the upper unit.
The written test assesses the student's ability to:
The oral exam focuses on the topics faced during the lectures and aims to assess to which extent the student:
Suggested pre-requisite: Applied Mechanics, Technical Drawing