OVERVIEW

The objective of this course is to provide the concepts, procedures, decision analysis techniques necessary to design machine elements commonly found in mechanical devices.

AIMS AND CONTENT

LEARNING OUTCOMES

The course aims to provide students of the knowledge and understanding of the criteria of structural design of the main mechanical members.

AIMS AND LEARNING OUTCOMES

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

• study the solids mechanics basic models and recognize these patterns in machine parts and structures to deal with them through appropriate simplification

• 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

• achieve a clear vision of the physical aspects of the analyzed structural behaviors

• 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

TEACHING METHODS

The course consists of lectures and a theoretical-practical laboratory component.

The lectures, which may also follow a flipped classroom format or other forms of active and interactive teaching, together with numerous exercises drawn from engineering practice, place particular emphasis on highlighting how to simplify a real object into an appropriate model that can be solved analytically. By consulting appropriate diagrams, the critical aspects of structures are emphasized—both in static and dynamic contexts—using as examples results obtained from numerical analyses on components not only from mechanical engineering, but also from naval, civil, and biomedical fields. In this way, students are encouraged to develop the ability to abstract from a specific problem and acquire the skill to extrapolate solutions to problems they have never encountered before. All diagrams relating to the mechanical properties of materials are constructed step by step, starting from real data obtained through experimental tests.

The laboratory will be conducted by the course instructors. At the beginning of each laboratory session, there will be a brief theoretical introduction aimed at providing the basic principles underlying the methodologies to be used. In the practical part, students—divided into groups of two or three and supported by instructors and tutors—will be required to apply the provided experimental protocol and the described methods. At the end of each session, students must submit a brief report detailing the results obtained from the experimental activity. The organization and dates of the laboratory activities will be communicated directly by the instructors at the beginning of the course.

Students with certification for Specific Learning Disorders (SLD), disabilities, or other special educational needs are encouraged to contact the instructor at the beginning of the course to agree on teaching and examination methods that, while respecting the course objectives, take into account individual learning styles and provide suitable compensatory tools.

SYLLABUS/CONTENT

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

RECOMMENDED READING/BIBLIOGRAPHY

Reference books:

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

TEACHERS AND EXAM BOARD

LESSONS

LESSONS START

https://corsi.unige.it/en/corsi/8784/studenti-orario

Class schedule

MACHINE DESIGN

EXAMS

EXAM DESCRIPTION

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.

ASSESSMENT METHODS

The written test assesses the student's ability to:

• schematize a device by converting its elements to types that can be solved with algorithms (beams, plates, etc.)
• apply the appropriate constraints between the various elements and between them and the frame
• schematize the loads acting on the structure
• draw the characteristics of stress in specific sections
• identify the most stressed areas
• dimension the critical areas by choosing the right material
• unambiguously present the product, according to the European projections method

The oral exam focuses on the topics faced during the lectures and aims to assess to which extent the student:

• has assimilated an adequate level of knowledge about the legislation
• has acquired the ability to logically face problems that will be posed during the test
• can illustrate theories and solve problems
• expresses his thinking clearly
• uses appropriate terminology
• uses a methodological approach oriented to manufacturing feasibility
• interprets and formulates principles related to the description of parts in a univocal, unambiguous and non-redundant manner

FURTHER INFORMATION

Suggested pre-requisite: Applied Mechanics, Technical Drawing