- Docente: Cristiano Fragassa
- Credits: 6
- SSD: ING-IND/14
- Language: Italian
- Teaching Mode: Traditional lectures
- Campus: Forli
- Corso: First cycle degree programme (L) in Mechanical Engineering (cod. 0949)
Learning outcomes
After completing the course, the student has the tools to address
and solve problems of reliability with particular attention to the
specificities that are inherent in the construction of mechanical
systems. As part of the course provides some tools and methods for
evaluating the reliability of components and mechanical systems:
tools and methods based on probabilistic calculation and
statistical tools and methods for statistical quality control of
products and processes, tools and methods for the study and the
probabilistic analysis and stochastic modeling of the mechanical
components and their failure modes, tools for reliability analysis
of mechanical systems and meccattronici complex taking into account
any maintenance.
Course contents
What is reliability: how to define and how it is calculated.
The concepts of MTTF (Mean Time To Failure), MTBF (Mean Time
Between Failures), failure rate. Calculation
of the reliability starting from the accrual of failure.
The functions of cumulative probability of damage and probability
density. Failure
probability and reliability conditional.
Calculation of reliability, probability, MTTF and failure rate for
systems in series and in parallel. Systems in
series-parallel.
Binomial probability distribution and cumulative
probability.
Systems in redundancy k n: calculation reliability and MTTF.
Processing of the formula for calculating the MTTF in the case of n
blocks in complete redundancy. Systems in redundancy
with standby.
Complex systems: generalities, methods of decomposition (or
key-item) and enumeration: application to a case study.
The minimal path sets and minimal cut sets: determination of the
lower and superore reliability.
The trees
in the logical reliability analyzes.
The fault tree (FTA): generalities, logical connectors,
symbolist.
Illustration of fault trees with reference to accidents that
actually occurred. Link
between fault tree and minimal cut sets. The event tree (ET).
I
outline fishbone diagrams of Hishikawa. Resolution of numerical
exercises.
FMEA (Failure Mode and Effect Analysis): definition, general,
purpose, composition of the team.
Determining the Risk Priority Number (Coefficient of priority of
risk, RPN).
The FMECA (Failure Mode and Effect Criticality Analysis) according
to the Military Standard MIL-STD-1629A: establishment of the
severity of a failure, the probability of occurrence, the array of
problems, the index of criticality for each failure mode
and for components, determination of the ranking of criticality by
class of severity.
Practical exercises and case studies on:
Determining the rate of failure according to the statistical
analysis of a large population of experimental data.
Execution and industrial applications of FTA
Execution
and industrial applications of FMECA.
Readings/Bibliography
A. Freddi, Imparare a progettare. Principi e metodi del
progetto concettuale per lo sviluppo della creatività
industriale, Pitagora Editrice, 2005, ISBN: 8837115121
S. Beretta, Affidabilità delle costruzioni meccaniche, Springer, 2008, ISBN: 978-88-470-1078-9
P.D. Berger, R.E. Maurer, Experimental design with applications in management, engineering and the sciences, Duxbury Press, Belmont, CA, 2002, ISBN: 0-534-35822-5
R.C. Michelini, R.P. Razzoli, Affidabilità e sicurezza del manufatto industriale. La progettazione integrata per lo sviluppo sostenibile, Editrice Tecniche Nuove, 2000, ISBN: 8848110851
Teaching methods
Lectures (at the blackboard). Projection of slides. Exercise group. Individual exercises.
Assessment methods
The exam consists of a written and oral phase, to be supported on the same day. The script, the average duration of one hour, usually includes the resolution of one or more numerical exercises on one or more topics of the course. The oral focuses on theoretical questions on the main topics of the course.
Teaching tools
Books and other materials provided by the teacher.
Links to further information
https://www.dropbox.com/sh/xxuv481s6iig1t7/AACiaxmvURakLjZeBCwJlfXsa?dl=0
Office hours
See the website of Cristiano Fragassa