Fatigue fractures may occur as a consequence of cyclic loading structures. In particular, within the context of fatigue and damage tolerance certification, engineers should have the knowledge and skills to analyse and assess fatigue life and fatigue performance. This includes the ability to design against fatigue and to validate designs with validated fatigue strength justifications. Fatigue fractures and related structural failures may be caused by a variety of factors, such as quality of applied materials, the production technology, the structural design, inappropriate reliability calculations, underestimations of load spectra, and inappropriate use of structures. With so many possible factors an integral and rigorous engineering approach is required.
This course will provide you with the knowledge and skills to identify potential critical locations and sources of poor fatigue performance; to develop strategies to avoid fatigue fractures and to improve fatigue performance of structures.
The course suits mainly aerospace engineers whose responsibilities include aircraft structures. However civil engineers, structural engineers, as well as engineers working in the manufacturing industry would benefit as well from a high-level review of fatigue life assessment and damage growth.
For anyone working on development, design or strength justification of engineering structures this course will be invaluable. It will not only learn the methods and best practices, but also explain thoroughly the fundamentals that allow assessing the limits of current practices, and ways to overcome such limitations. In short, you will become a fatigue and damage tolerance specialist!
By the end of this course you will be able to:
- Interpret and discuss the fatigue fracture features with respect to the characteristics of each phase in fatigue life.
- Define and determine stress concentration factors for notched structures with or without residual stresses.
- Explain and discuss S-N curves with respect to mean stress, material surface effects, and scatter, and perform fatigue life analyses considering mean stress and notch root plasticity.
- Assess the fatigue life of tension and shear joints, and explain limitations to the similarity principles.
- Explain Linear Elastic Fracture Mechanics concepts for damage growth, and perform crack growth analyses with these concepts.
- Explain the consequences of variable- and constant amplitude loading on fatigue life and damage growth, and perform fatigue life analyses for arbitrary load spectra.
- Explain the effect of environment on fatigue life and fatigue phenomena.
- Perform residual strength analyses.
- Week 1: Fatigue phenomena and societal consequences. Understanding the various fatigue fracture phenomena in engineering metallic and composite structures. Definition of fatigue and description of the history of fatigue assessment. Principles for designing against fatigue. Fatigue damage initiation and growth mechanisms.
- Week 2: an introduction to stress concentration factors (SCFs), principles to work with and calculate SCFs and design against stress concentrations. Influence of residual stresses.
- Week 3: Assessment of fatigue life, definitions and best practices, discussion of scatter. Discussion of joining in relation to fatigue, aspects like fretting corrosion and pretensioning.
- Week 4: Introduction to stress intensity factors (SIFs) and damage growth predictions. The relation between physics of phenomena and stress based methods. Crack growth predictions.
- Week 5: Discussion of the effect of variable amplitude loading on fatigue life assessment and damage growth predictions. Load spectra measurements and usage monitoring.
- Week 6: Fatigue in composites; description of typical fatigue mechanisms and phenomena in relation to best practices for evaluation. Influence of environment.
- Week 7: Residual strength analysis and testing in relation to aerospace damage tolerant design certification.
Assignment(s) and Assessment
This course aims to convey the knowledge via online lectures, while quizzes and assignments aim to practice the related skills. Collaboration and discussion with fellow online students are strongly recommended to improve the learning experience: you learn it best by explaining it to others.
Student/professionals are expected to complete the following assignments prior to the written examination:
- Assignment 1: Stress concentration factors
- Assignment 2: Fatigue properties and S-N curves
- Assignment 3: Pre-tensioning and fatigue
- Assignment 4: Stress intensity factors
- Assignment 5: Fatigue life under variable amplitude loading
- Assignment 6: Crack growth under variable amplitude loading
- Assignment 7: Residual strength
Date of proctored exam: October 29, 2018.
Date of resit: January 21, 2019.
This school offers programs in:
Last updated September 18, 2018