34313 - Machine Design

Learning outcomes

The outcomes of the course are to provide the basic knowledge, the methods and the tools useful for the correct definition of the mechanical design activities. At the end of the course the students will be able to reproduce the representation of a simple mechanical system, to define the relationship between the elements, to calculate the constraints, to draw the stress diagrams and to compute the maximum tensile state of the components. Furthermore they will be able to verify the fatigue life of simple mechanical components and to calculate the strength of some basic bolted and welted structures. Finally they will be able to select the most appropriate rolling bearings to be positioned as constraints of shafts, pins and axes.

Course contents

Introduction to the study and to the analysis of a mechanical system.

Function analysis of a product; the kinematics and dynamic representation of a simple mechanical system and the relationships between the machine elements.

The rigid body equilibrium.

Work and power. Motion and energy transmission between the machine elements. Morphologic characteristics and the load analysis of the mechanical systems. Structural models and tensile state analysis. Stress concentration factors. Residual stresses. The normal stress. The bending stress. The shear stress. The torsion stress. The failure of materials under static loads. The equivalent uniaxial stress in case of static load.

The dynamic failure of the metals. The fatigue stress. The S-N (Wlöer) curves and the Haigh diagrams. The surface, gradient, dimension and load effects on the fatigue strength. The equivalent uniaxial stress in case of dynamic load. The medium stress effects on the fatigue strength.

The gear design. The tooth stress: the bending and the pitting strength. The cylindrical gears straight-toothed and helical-toothed. The conical gears. The loads produced by the gears on the shafts.

Fundamentals of bolted and welded structures: the static calculation.

The rolling bearings selection and their life prediction.

Readings/Bibliography

Texts references

Dario Croccolo, Nicolò Vincenzi - Lezioni di fondamenti e tecnica della progettazione meccanica - Società Editrice Esulapio - Bologna - 2011

Dario Croccolo, Massimiliano De Agostinis, Giorgio Olmi - Esercizi di Coportamento meccanico dei materiali ed Elementi delle macchine - Società Editrice Esulapio - Bologna - 2013

Dario Croccolo, Massimiliano De Agostinis, Giorgio Olmi - Esercizi di Costruzione di macchine e Tecnica delle costruzioni meccaniche - Società Editrice Esulapio - Bologna - 2013


Recommended reading

R. Giovannozzi

“Costruzione di macchine” vol I e II

Patron, Bologna



Niemann/Winter

“Elementi di macchine” vol I

EST Springer–Verlag Berlin, Heidelberg, New York

Teaching methods

The lectures concern the fundamentals problems of the mechanical design of products and systems. The practicing are collective and concern the application and practical solutions of theoretical problems proposed during the lectures.

Assessment methods

As a result of the emergency situation linked to the pandemic from Covid-19, from June 2020 and up to the date to be assigned, the exams will take place on the online mode, with the combined use of the On Line Exams (EOL) and Zoom platforms.

Exam method

First, the student must register on the list regularly by the date indicated in Almaesami.

Students who are not inserted into the list of the exam in Almaesami and students who are not up to date with the payment of the enrollment fees and/or present other impediments reported by Almaesami will NOT BE ADMITTED to the test. Each student is, therefore, STRONGLY INVITED to CHECK HIS POSITION promptly and, if necessary, to FIX IT BEFORE the exam date.

Once connected to EOL, the student will be able to read the instructions with reference to the exam to which he is regularly enrolled, Students who have NOT managed to register within the deadlines will NOT be able to access, on EOL, the material related to the exam. FOR THIS REASON, THE PRESENCE IN THE LIST OF THE EXAM IS CONSIDERED COMPULSORY IN ORDER TO PARTICIPATE IN THE EXAM.

Here are the instructions

1. Click on the link to the Zoom meeting and log in using your credentials. Wait for the classroom overseer to give access.

2. Activate the computer's Web-Cam and show the attendant an identification document and the checkered (or white) sheets, which will be used during the test.

3. Share the desktop of your computer. Important! Web-Cam and desktop sharing must be active for the entire duration of the test, under penalty of exclusion from the exam.

4. Download the theme from the link, which can be accessed after the exam begins with an access code.

5. Carry out the proposed theme or themes using the input data corresponding to the group, which will be assigned using an algorithm.

6. Write the development of the teme or themes assigned on the sheets previously shown to the classroom overseer. The sheets must be numbered and must contain (each) the assigned group letter, the surname, the name, the personal enrollment number and the original signature.

7. Once the development of the exam is complete, scan all the sheets using a smartphone. For this purpose, you can use a program for the creation of PDF documents directly from the camera of the smartphone: we recommend using Adobe Scan (freely downloadable and usable for iOS and Android systems). The duration of the test has been increased by 15 minutes (compared to the presence mode), just to take into account the time required for scanning and uploading operations.

8. By the end of the time assigned to the exam completion (180 minutes plus 15 additional minutes = 195 minutes), upload the PDF file created (with pages in sequential order) by the uploading tools of EOL after having named it with Letter_Group_ Surname_Name_student ID number.PDF. For example, the student Matteo Rossi, with the student ID number 12345678, who has carried out the theme of Group D, will have to name his file: D_Rossi_Matteo_12345678.PDF.

The assessment test of learning is written. The written test consists of the solution of three exercises on the three main parts of the program.

Teaching tools

PC projector. Overhead projector. Blackboard.

Office hours

See the website of Dario Croccolo

See the website of Francesco Robusto