LEARNING OUTCOMES

The aim of this course is to supply  overall methods for machine design in reference to static, fatigue strength, and brittle failure

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 with particular reference to structural design criteria for static and fatigue loads, creep and fracture

• 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

What’s Machine design

Materials

Static strenth, Plastic deformation, Strength and hardness, Viscoelasticity, Creep and temperature properties

Design for static strength

Failure of ductile and brittle materials, Stress concentration, Determination of stress concentration factors, Stress concentration charts, Design for static strength with notched elements

Design for fatigue strength

S-N diagram, High-cycle fatigue, Endurance –limit modifying factors, Stress-concentration effects, Torsion, stress due to combined loading, Cumulative fatigue damage

Fracture mechanics

Stress state in a crack, SIF, Critical stress-intensity factor, Fracture toughness factors, Fatigue cracks propagation

Pressure vessel design

Cylindrical and spherical pressure vessels: thick and thin-walled vessel, shrink fits

Shafts

Flexural vibration, Torsional vibration

Weldings design for static and fatigue loads

RECOMMENDED READING/BIBLIOGRAPHY

J.E. Shigley, “Mechanical Engineering Design”, MCGraw-Hill

R.E. Peterson, “Stress Concentration factors”, Wiley-Interscience Publication

R.W. Hertzberg, “Deformation and fracture mechanics of engineering materials”, John Wiley & Sons

R.C. Juvinall, “ Fundamentals of machine component design”, John Wiley & Sons