50008 - Reliability and Safety of Mechanical Constructions

Academic Year 2021/2022

  • 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, slides and other teching materials are provided by the teacher.

Office hours

See the website of Cristiano Fragassa

SDGs

Industry, innovation and infrastructure Responsible consumption and production

This teaching activity contributes to the achievement of the Sustainable Development Goals of the UN 2030 Agenda.