AIMS AND CONTENT

LEARNING OUTCOMES

The course aims at giving the basics of machine design and to introduce the practices to correctly dimension the machine elements of mechanical systems. Based on the formerly acquired knowledge of structural mechanics, the students will learn how to design those elements for static and dynamic loads. Then, the main machine components will be studied to understand the criteria for proper choosing or sizing them in mechanical systems

AIMS AND LEARNING OUTCOMES

The course aims to provide students with the basic knowledge of structural design criteria (design for static strength and fatigue design) and on the methodologies and tools available for the analysis and structural design of the main mechanical parts. In addition, the course aims to introduce the student to product design, with particular reference to the design/choice of machine elements.

Attendance at lectures and guided exercises and individual study will allow the student to:

• learn the general aspects of Machine Design
• learn how to model and compute the mechanical behavior of machine elements when subjected to static and dynamic loads
• master the use of the mechanical characteristics of the materials most commonly used in the mechanical and structural fields, resorting to the use of pre-existing databases and the interpretation of experimental results, as well as simplified methods validated also at a regulatory level
• understand the reliability of the results obtained with conventional calculation methodologies, essentially simplified analytical

TEACHING METHODS

The teaching unit will be composed of contextual and integrated lectures and exercises, carried out by the teacher in charge of the course.

A practical part is then planned that will consist of the development of the project of a simple mechanical system of which the various components (typically shafts, gears, supports, etc.) will be defined. The project will be developed in groups (3-4 students per group) with methods and procedures that will be illustrated during the lectures. The results of the project work will be illustrated by writing a technical report that will explain the adopted design choices and sizing of the components. The project is mandatory being an integral part of the evaluation.

SYLLABUS/CONTENT

Part I – Structural Design Criteria

Design for static strength. State of stress and state of strain in solids, plane problems of stress and strain, theory of beams (recalls). Concept of structural stiffness, stiffness of systems connected in series and in parallel. Static strength of materials. Ideal or equivalent stress. Strength criteria for brittle and ductile materials. Safety condition for static strength: limit stress, safety factor, permissible stress.

Concentration of stress. Notches and their effects. Theoretical and experimental stress concentration factors. Safety condition for static strength in the presence of notches.

Fatigue design. Fatigue in metallic materials. High-cycle fatigue. Wöhler curves. Influence of the average stress. Notches and their influence. Size factor. Surface finish factor. Safety condition for constant amplitude stresses. Safety condition for variable amplitude stresses. Cumulative damage.

Part II – Design of Mechanical Parts

Vessels and pipes, thin cylindrical tubes. Spherical vessels. Vessels for high pressures.

Elements for the transmission of motion between coaxial parts: keys, tabs, plugs. press-fits and shrink fits.

Non-removable connections: welding, riveting, bonding.

Detachable connections by screws: bolted joints.

Elastic connections: coil springs, leaf springs, disc springs, ring springs, other types.

Power transmission components: gears.

Rotating parts supports: rolling bearings.

RECOMMENDED READING/BIBLIOGRAPHY

Lecturers' notes (handouts).

Reference texts:

• R.C. Juvinall, K.M. Marshek, Fundamentals of Machine Component Design,  Wiley; 7th edition, 2020
• R. G. Budynas, J.K. Nisbett, Shigley's Mechanical Engineering Design, McGraw-Hill, 11th edition, 2014
• S.R. Schmidt, B.J. Hamrock, Fundamentals of Machine Elements: SI Version, CRC Press, 3rd edition, 2014

More materials will be suggested via the AulaWeb course page.

TEACHERS AND EXAM BOARD

LESSONS

LESSONS START

https://corsi.unige.it/en/corsi/8720/studenti-orario

Class schedule

ELEMENTS OF MACHINE DESIGN

EXAMS

EXAM DESCRIPTION

Exam with written test consisting of the solution of 1-2 design problems of a mechanical system, with the choice and/or sizing of some parts/components (practice) and 1-2 questions on the topics covered in class (theory).  Both practical and theoretical tests must be sufficient (score of at least 9/15 points). The evaluation of the papers of the project exercise with a score ±3 points will be added to the grade of the written exam obtained as the sum of the evaluations of the two components of practice and theory (up to a maximum of 15+15 points). An overall score greater than or equal to 32 may result in a grade of 30 laude.

Students with SLD, disability or other special educational needs are advised to contact the teacher at the beginning of the course to agree on teaching and examination methods that, in compliance with the teaching objectives, take into account individual learning methods and provide suitable compensatory tools.

ASSESSMENT METHODS

The exercises proposed in the written exam will be aimed at evaluating the ability to solve simple problems of mechanics of structures, with reference to the components of machine parts. The questions will allow students to verify the ability to set up simple mathematical proofs, aimed at identifying the formulas for sizing and verifying them, and the understanding of the physical and mechanical aspects of the topics covered.