Module: Fatigue and Fracture Mechanics

Objectives

Structures rarely fail from “one big load”, they often fail from millions of load cycles and small cracks. This module equips students with the core methods used in engineering practice to assess the durability, remaining life and safety of steel components in bridges, pipelines, towers, industrial structures, and offshore/onshore wind
support structures. 
In addition, a key focus is the link between mechanics and digital engineering workflows: students learn how fatigue and crack assessment can be supported by digital inputs and computer vision (e.g., images/measurements of critical details) and how these can be translated into suitable assessment and simulation models. The module combines fundamentals with practical application, from simplified nominal design concepts to local and numerical methods.
 

After completing the module, students can:
- explain fatigue and crack mechanisms under cyclic loading,
- select appropriate fatigue assessment concepts (nominal versus local approaches) and understand their limitations,
- apply essential fracture mechanics concepts (crack driving forces, resistance and crack growth), and
- interpret numerical results to support design decisions and lifetime-extension/inspection strategies.
This module is particularly recommended for students interested in on and offshore wind turbines, bridges, structural safety, lifetime extension and inspection planning.

Topics

Part A: Fatigue
- Mechanisms of fatigue crack initiation in ductile and brittle materials
- Crack initiation under uniaxial high-cycle fatigue loading
- Crack initiation under multiaxial high-cycle fatigue loading
- Fatigue assessment using nominal and local concepts: applicability and limitations

Part B: Fracture mechanics and crack assessment
- Linear elastic fracture mechanics (LEFM)
- Elastic–plastic fracture mechanics
- Fatigue crack growth models and remaining-life concepts
- Cohesive zone modelling concepts Computer laboratory
- Basic introduction to simulations in ABAQUS FE Package and programming using MATLAB Laboratory visit
- Testing Laboratory: Visit to the “Institute for Steel Construction” testing laboratory (fatigue and crack experiments, measurement and monitoring methods

Exam