electiveHQ

Syllabus: This module provides a comprehensive introduction to the important field of engineering fracture mechanics. Firstly, an overview is given of the historical development of the subject, from the early part of the twentieth century to the present day. Approximate equations are developed for the theoretical strength of a defect-free material using a simple atomic model. Linear elastic fracture mechanics (LEFM) is then introduced using both Griffith's energy-based and Irwin's stress intensity factor approaches.The experimental determination of a material's fracture toughness is then discussed with the aid of double cantilever beam (DCB) and tapered double cantilever beam (TDCB) specimen geometries. The state of stress in the vicinity of a crack tip under the three fundamental modes of loading is then discussed and the size and shape of the plastic zone ahead of a crack tip are determined. The influence of the three dimensional state of stress in the near-tip region on the apparent fracture toughness is also analyzed.Great emphasis is placed on the application of fracture mechanics as a engineering design and analysis tool, and numerous case studies are examined.The important application of LEFM to fatigue crack growth is discussed in detail, with comparison being made to traditional approaches to fatigue design. The fatigue failure of the Comet aircraft in the 1950s will be analyzed in detail. An introduction to elastic-plastic fracture mechanics (EPFM) is also provided, with a discussion of the two most important fracture parameters, the crack tip opening displacement (CTOD) and the J-integral. As before, the standard testing procedures for the experimental determination of these parameters are described and the theoretical and practical importance of these quantities is discussed. Laboratory session: Failure analysis of a selection of fractured engineering components from a variety of industries. All laboratories are carried out with reference to current School Health and Safety protocols. Students should follow these during all laboratory activities. Further information is available at https://intranet.ucd.ie/smme/index.html Regular tutorials will take place during scheduled lecture times in which case studies will be discussed illustrating the application of fracture mechanics to real world problems. A research literature-based assignment will be undertaken by groups of students who will then present their findings to staff and classmates. Homework Assignment: A fracture mechanics approach will be used to estimate the service life of a typical machine component. Textbook: Fracture Mechanics - Fundamentals and Applications, T.L. Anderson, 4th edition, CRC Press (Taylor & Francis), 2017.