Fatigue Design of Mechanical Joints and Aerospatial Structures
Objectives
The fundamental objective of this course is to provide students with the necessary knowledge to carry out the fatigue design of primary mechanical joints used in the aerospace industry, such as bolted, riveted, welded and adhesive connections. At the end of this course, the student is expected to have acquired knowledge, skills and competencies that allow him/her to:
- Describe the main types of mechanical joints likely to be used in the aerospace industry;
- Design against fatigue the main types of mechanical joints involved in the assembly and manufacture of aerospace structures;
- Identify, understand and take into account some of the special conditions of fatigue crack propagation, namely at high and low-temperature, under the influence of corrosion, or subject to fretting;
- Understand the influence of surface conditions, notches, stress concentration and residual stresses in the fatigue design of mechanical connections and aerospace structures;
- Be able to fatigue design according to the principles of safe-life, fail-safe or damage tolerance methodology;
- Understand the concepts of Probabilistic Fracture Mechanics;
- Simulate with the Finite Element Method (FEM) the primary mechanical joints using commercial software (SW Simulation®, Ansys®, Abaqus®).
General characterization
Code
13151
Credits
6.0
Responsible teacher
António José Freire Mourão, Rui Fernando dos Santos Pereira Martins
Hours
Weekly - 4
Total - 56
Teaching language
Português
Prerequisites
No requirements are necessary.
Bibliography
- Fatigue of Structures and Materials, Jaap Schijve, https://doi.org/10.1007/978-1-4020-6808-9
- Failure Analysis and Prevention, Vol 11, ASM Handbook, ASM International, 2002
- Reddy, J. N.; An Introduction to the Finite Element Method. ISBN: 0-07-112799-2
Teaching method
Theoretical lectures and practical laboratory classes for solving exercises, preparing mechanical joints, and testing them.
One test (30%) and two practical assignments on crack propagation simulation, each with an equal weight of 35% in the final grade, will assess the acquired knowledge.
Evaluation method
The knowledge assessment will consist of a theoretical-practical test (Test) (30%) and two fatigue crack propagation assignments (Numerical simulation, T1, and Experimental, T2), each weighing 35% of the final grade. Grades, ranging from 0 to 20, will be rounded to two decimal places.
Attendance, valid for one year, requires a weighted average of the assignments (T1 and T2) equal to or greater than 9.50. The minimum grade for the theoretical-practical test is 9.50.
Passing the course requires a final grade (NF) of at least 9.50, calculated differently depending on the assessment period:
Continuous Assessment: NF = 0.3 × Test + 0.35 × T1 + 0.35 × T2
Resit/Special/Extraordinary Exam Period: NF = 0.3 × Exam + 0.35 × T1 + 0.35 × T2
Subject matter
1) Description of the main concepts of Fatigue Design:
- Stress Intensity Factor.
- Mode I, Mode II, Mode III or mixed-mode crack propagation
- Mean Stress Effect
- Crack propagation under the effect of constant or variable amplitude loading
- Crack nucleation and propagation under tensile, flexural, torsional or combined loading
- Low-Cycle fatigue, High-Cycle or Very High-Cycle fatigue loading
- Influence of notch(s), stress concentration and residual stresses
2) Description of the main mechanical joints: bolted, riveted, welded and adhesive;
3) Fatigue design of mechanical joints and aerospace structures
4) Fatigue design involving high and/or low temperature, corrosion and fretting;
5) Fatigue crack propagation: fatigue life prediction and analysis models;
6) Mechanical testing of fatigue strength and fatigue crack propagation. Statistical analysis. Scatter;
7) Fundamentals of Probabilistic Fracture Mechanics;
8) Fundamentals of Finite Element Method (FEM): types of elements, mesh generation, material models, boundary and loading conditions, convergence analysis, errors;
9) Finite Element Software (Solidworks Simulation®, ANSYS® and ABAQUS®). Numerical simulation of fatigue crack propagation;
10) Failure Analysis: case studies.