Organised by ESIS TC03 “Fatigue of Engineering Materials and Structures ”
Wednesday, 8 July 2020
The Technical Committees No. 3 organises one day event in the frame of the “1st Virtual ESIS Summer School – VESS1”, entitled Fatigue of Materials and Structures.
The event aims to provide to young scientists and engineers both from Academia and Industry the unique opportunity to meet and learn from leading international experts about fatigue of materials and structures.
The format of the event will include tailored theoretical sections and hands-on activities provided by experts from leading international research institutions.
Lecturers from leading international research institutions
José Alexander Araújo, University of Brasília, Brazil
Alberto Campagnolo, University of Padua, Italy
Alfonso Carlos Fernandez Canteli, University of Oviedo, Spain
Ed Habtour, University of Washington, USA
Sabrina Vantadori, University of Parma, Italy
The course is specifically designed for Ph.D. students, young researchers and industry engineers interested in the field of fatigue of materials and structures.
Certificates will be issued on the basis of participation to the course and the evaluation of the final assessment will entitle Ph.D. students to 0.5 ECTS.
11.10 – 11.55: Phenomenological probabilistic models for assessment and prediction in fracture and fatigue
Alfonso Carlos Fernandez Canteli, (University of Oviedo, Spain), Enrique Castillo (Royal Academy of Engineering of Spain, Spain), (Presentation)
13.10 – 14.00: Break
14.00 – 15.00: Final Assessment
The lecture will provide an overview of fatigue in structural elements found in engineering and biological systems. Basic principles such as standard fatigue strength, stress-life curves, and endurance limit will be introduced. Finally, approaches for analyzing fatigue in cases where plasticity is present will be briefly introduced. Short practical examples will be provided.
The fatigue failure phenomenon of welded joints will be briefly commented by taking advantage of some experimental case studies. After that, the fatigue design of welded structures according to current International Standards and Recommendations will be presented. Accordingly, the nominal stress, the hot-spot stress, the notch stress approach and the Linear Elastic Fracture Mechanics (LEFM) applied to welded structures will be presented and compared. Finally, some further developments relevant to local approaches will be discussed.
Fretting fatigue is a type of failure that may occur in components of a mechanical assembly, which are not only subjected to some sort of vibration, but also to a time varying remote stress. In these cases, surface damage arises due to a minute relative displacement between the contacting surfaces. Further, the normal and shear contact loads generate high surface stresses that fall rapidly with distance from the contact interface. Crack initiation in this type of mechanical problem is thus mainly governed by the stress field and the surface damage generated by the contact loads. This seminar will provide an overview about the fretting fatigue phenomenon. Examples of mechanical components subjected to fretting fatigue will be shown and the use of simpler contact geometries to model and further understand the governing variables of the problem will be discussed. Some more recent approaches to design against fretting fatigue will also be addressed as well as the test devices which have been proposed to produce laboratory data in order to validate such approaches.
Prof. Alfonso Carlos Fernandez Canteli, (University of Oviedo, Spain, email@example.com), Prof. Enrique Castillo (Royal Academy of Engineering of Spain, Spain) "Phenomenological probabilistic models for assessment and prediction in fracture and fatigue"
Transferability and structural integrity are constantly invoked as ineluctable conditions to ensure safe component design. Among the different model types, phenomenological models, based on extreme value statistics, are particularly suitable to be used in the probabilistic assessment of experimental results and subsequent application on fracture and fatigue design of components. Among the physical and statistical conditions to be fulfilled, compatibility, represents a transcendental requirement which allows a new way, the use of functional equations, to be applied for deriving probabilistic S-N fatigue models. Some advantages provided by such models are the definition of the S-N field as percentile curves, the recognition of the normalized variable allowing the reduction of the whole S-N field as a single cumulative distribution function to be achieved, the probabilistic analysis of damage accumulation design using this normalized variable, the determination of the fatigue limit as a model parameter and the inherent consideration of the size effect, among others. The methodology proposed facilitates the extension to the consideration of different cases of sample functions, i.e. process evolution, as those related to fatigue crack growth.
On the other side, the correct experimental mechanical characterization in fracture and fatigue requires not only carrying out tests but a suitable plan of the experimental program in consonance with the model, followed by the consistent assessment of test data, i.e. independent of the particular type and size of specimens or test modality adopted, to provide reliable prediction in component design. This can be guaranteed by the adequate application of the generalized local model (GLM) with the only conditions of statistical independence among the experimental results and the applicability of the weakest link principle. As a result, a reliable evaluation of experimental results and failure prediction in fracture and fatigue life is ensured.
To introduce this general methodology of phenomenological probabilistic models is the aim of this presentation.
TC3 Secretariat: Professor Sabrina Vantadori
Department of Engineering & Architecture - DIA
University of Parma
Parco Area delle Scienze 181/A, 43124 Parma - Italy
Phone: +39 0521 905962