Aims of the course
The aim of the course it to give students the tools for assessing a mechanical system in terms of reliability of its components on the basis of strength/life data. This type of analysis, which is vital in the design of vehicles and aerospace systems, is connected with a modern planning of reliability and acceptance tests. In particular students, after learning reliability techniques, will address special projects for the analysis of components and systems.
Description of the topics
1. Analysis of reliability data: histograms, reliability and life, distributions for describing engineering data, sampling distributions, ML method and analysis of data from industrial tests (run-outs and inspections), model for life degradation (temperature, fatigue).
2. Statistics of Extremes: from parent distribution to extremes, asymptotic distributions, block maxima sampling and return period, extrapolation to extreme events. Structural applications to analysis of loads and defects in a material (sampling from polished sections and CT scans).
3. Reliability analysis for a component: Calculation of failure probability for common failure modes (static and fatigue failures, progressive damage). Basic concepts of Montecarlo simulation. How to describe component failure rate.
4. Methods for system reliability: Reliability block diagrams, minimal cut sets and conditional probability; Stand-by and active redundancy. FMECA for describing simple systems (SAE method); Fault and Event Trees. Application to aeronautical power and hydraulic systems. Preventive maintenance.
5.a Reliability testing: estimate of failure rate, minimum data sample for a given test, reliability demonstration tests.
5.b Structural reliability: Weakest-link and fail-safe structures, simple bounds for failure probability for these schemes, Weibull format for brittle failures. (this topic can be alternatively chosen by the students instead of Reliability testing).
Characteristic features of the course are design laboratories (with mechanical and aerospace applications) where the following case-histories will be analyzed:
1) reliability of a component realized by Additive Manufacturing (including analysis of CT scans) and 2) reliability of a simple mechanical power transmission;
3) reliability block diagram and FMEA of an engine and 4) analysis for the hydraulic power of AIRBUS 319 together with comparison, in terms of reliability, with the hydraulic lift of a tractor.
Course organization and exam
Class schedule planning: Lessons (30 hours), Training (12 hours), Computer and Application Laboratory (31 hours).