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 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. 

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