Estimation of fatigue lives of machines and structures is a major concern with regards to service safety and costs. Numerous analytical techniques are available and can be used with varying degrees of success; however, many questions still arise. Which methodology is best suited for which application? How to define the correct inputs for a specific technique? How can the structure be improved to meet the service conditions? This seminar will address these questions from the fracture mechanics perspective – relatively young branch of material science and mechanics.
Any fracture analysis or fatigue life estimation procedure consists of three main areas that are used to input the data and carry out the analysis:
- loading/stress history;
- material properties; and
- geometry of analyzed mechanical component or engineering structure.
The basics of the fracture mechanics theory, the derivation of all input data necessary for fracture mechanics analyses and their physical meanings will be discussed in the first part of the course.
Secondly, the general rules concerning the static strength analysis of cracked bodies will be briefly discussed in order to make an analyst aware of differences between the static and fatigue failure processes and stress parameters used in such analyses. Particular attention will be devoted to the nature of stress parameters used in fatigue analyses, i.e. stresses normal to the potential crack plane, stress distributions and Stress Intensity Factors. Various methods of calculating Stress Intensity Factors for notched and welded components will be discussed and illustrated with practical examples.
Finally the Fracture Mechanics based fatigue analyses (da/dN - ∆K) will be discussed including the calculation of appropriate Stress Intensity Factors for cracks in geometrically complex machine components, evaluation of the residual stress effect, evaluation of the weld geometry and the effect of their scatter on the predicted fatigue life. Among others the weight function technique, particularly useful for calculating Stress Intensity Factors for non-classical crack problems, when combined with the Finite Element stress data will be presented. A technique for the fatigue crack growth analysis of planar irregular cracks in nonlinear stress filed will be discussed and the possibility for its application for the fatigue analysis of small inclusions or/and material imperfections.
The course will be concluded with failure analysis of several mechanical and structural cases encountered in practice.
- Basic concepts of the fracture mechanics methodology
- The meaning and determination of stress intensity factors
- Stress concertation and stress intensity factors for cracks in weldments
- Fatigue crack growth theories
- Analysis of fatigue cracks growth in weldments
- Geometrical and residual stress effects
Basic courses on mechanics of materials and stress analysis, material science.
The seminar is particularly relevant to people involved in design, optimisation and fatigue assessment of steel structures and machinery components. Therefore the attendance is recommended to designers, structural engineers, mechanical engineers, fabricators, welding engineers, quality control, maintenance and inspection personnel, university lecturers, students, and researchers.
The seminar might be useful to the following industry sectors: steel construction, infrastructure fabrication and maintenance, bridge building, transport industry, power generation, machinery, shipbuilding, maintenance and aviation industry, ground vehicles, and earth moving machinery.
Dr. Grzegorz (Greg) Glinka, D.Sc.
Professor, Department of Mechanical and Mechatronics Engineering, University of Waterloo
Dr. Glinka has been with the University of Waterloo, Ontario, Canada since 1989. He was a Post-Doctoral Fellow at The University of Iowa (USA) in 1978 and has also lectured at the University of Metz, France and at the University College London, England. He holds a PhD and D.Sc. from the Warsaw University of Technology. He has also acted as an expert of the United Nations and visiting professor at The Aalto University in Helsinki, Finland. Dr. Glinka is a specialist in fracture and fatigue of steel structures and mechanical engineering machinery. His research interests include fracture of materials, fatigue of structures, multiaxial fatigue and creep of engineering materials, computer aided design, FEM-elastic-plastic stress-strain analysis, and reliability. His recent research activities concern modeling of fatigue crack growth under random loading and fatigue optimization of welded structures. Dr. Glinka has published over 190 related articles in technical journals and textbooks.