101-0121-00L Fatigue and Fracture in Materials and Structures
|Semester||Autumn Semester 2019|
|Lecturers||E. Ghafoori, A. Taras|
|Periodicity||yearly recurring course|
|Language of instruction||English|
|Abstract||In this course, the students will learn:|
• Mechanisms of fatigue crack initiations in materials.
• Linear elastic and elastic-plastic fracture mechanics.
• Modern computer-based techniques to deal with cracks.
• Laboratory fatigue tests on metallic details with cracks.
|Objective||The course will provide a basic knowledge on fatigue and fracture mechanics that are useful in different engineering disciplines such as mechanical, aerospace and civil engineering domains.|
|Content||The course covers the basics in fatigue and fracture of materials and structures. It starts with an introduction and then explains the learning goals and the importance of fatigue and fracture in different engineering areas such as mechanical, civil and aerospace engineering domains. The course includes different main topics summarized below: |
I) Damages mechanisms and crack initiation in materials under cyclic loadings:
• Mechanisms of fatigue crack initiation in (ductile and brittle) metals.
• Crack initiation under uni-axial fatigue loadings: critical plane approach (critical distance theory), equivalent stress approach, constant life diagram approach, rainflow analysis and Miner's damage rule.
• Crack initiation under multi-axial fatigue loadings: proportional and non-proportional loading.
II) Fracture mechanics:
• Energy analysis, energy release rate and limits of linear elastic fracture mechanics (LEFM).
• Weight function approach: stress intensity factors, crack opening displacement, etc.
• Elastic-plastic fracture mechanics: Irwin and Dugdale models, plastic zone shapes, crack-tip opening displacement and J-integral.
• Fatigue crack growth: crack growth models, Paris' law, crack closure effects, crack growth under mixed-mode.
III) Modern computer lab to simulate fatigue cracks:
• Finite Element Method (FE) and eXtended FEM (XFEM) in complex details.
• XFEM laboratory: training and exercises.
IV) Fatigue and fracture in civil engineering structures:
• An overview of the state-of-the-art (advanced) fatigue design and assessment methods as prevalent in (Central) Europe.
• Haibach, Sonsino, Radaj, FKM-Richtlinie and all the pertaining nominal to local approaches in fatigue assessment of civil structures (e.g., bridges) will be covered in this part.
• Overview of the Swiss and European fatigue design and verification standards of steel structures; for example, Swiss SIA 263 and 269 and Eurocode 3 (EN 1993-1-9) documents.
V) Fatigue and fracture in aerospace structures:
• Design philosophy based on damage tolerance approach.
• Fatigue of mechanically fastened joints and built-up structures (aircraft wing boxes).
• Crack repair techniques.
VI) A visit to the Swiss Federal Laboratories for Materials Science and Technology (Empa) in Dübendorf. The students will:
• Visit different small-scale and large-scale fatigue testing equipments.
• Get to know different ongoing fatigue- and fracture-related projects.
• Witness and help to conduct a fatigue test on a steel plate with a pre-crack.
• Compare the experimental crack-growth behavior (from the lab tests) with their own calculations (from the fracture theories).
|Lecture notes||Lectures are based on the lecture slides and handouts and will be updated throughout the course.|
|Literature||1. Schijve J. “Fatigue of Structures and Materials”, 2008: New York: Springer.|
2. Anderson T.L. “Fracture Mechanics - Fundamentals and Applications”, 3rd Edition, Taylor & Francis Group, LLC. 2005.
3. Budynas R.G., Nisbett J.K. “Shigley's Mechanical Engineering Design”, 2008, New York: McGraw-Hill.
|Prerequisites / Notice||Laboratory demonstrations and tests at the Structural Engineering Research Laboratory of Empa in Dübendorf, including laboratory tour and showcasing the Empa large-scale 7-MN fatigue testing machine for bridge cables, different fatigue and fracture testing equipment for structural components, etc.|