Crack growth modelling from stress concentrations under cyclic loading histories

  • Ross Beesley

Student thesis: Doctoral Thesis

Abstract

Structural integrity is a vitally important field of engineering with fracture and fatigue causing the vast majority of mechanical failures. This is of particular importance within the power industry where the consequences of failure can be severe. Power plant components may contain complex geometries and critical features which can introduce stress concentrations, and are often subject to complex cyclic loading histories. Consequently,fatigue is a dominant failure mechanism which can limit the component life.This research is targeted towards industrial gas turbines, with a specific application to nozzle guide vanes, in which, the extreme temperatures involved induce great thermal loading, compromising their integrity. To this end, extensive development is continually performed to carefully balance their thermal and structural requirements. However,there is still a need to improve understanding of these complex stress distributions.Conventional fatigue life assessment methods can be overly simplistic and tend to offer a one-size-fits-all approach, potentially providing overly conservative values of fatigue life. More realistic methods with improved levels of accuracy are therefore needed. This highlights the requirement for more bespoke techniques that can offer a greater understanding of the stress distributions in these complex components and high specification materials. During the development of such bespoke methods, it is important that they are readily accessible for routine use within engineering, by providing a user-friendly step-by-step approach.This industrial sponsored research aims to address these issues and provide a turn-key solution.Included in this procedure, are two novel methodologies which have been developed during the course of this work. These are the Reversed Plasticity Domain Method for the determination of the critical loads to cause low cycle fatigue failure, and the Modified Monotonic Loading Concept for the calculation of the cyclic J-integral.
Date of Award1 Oct 2016
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsRolls-Royce PLC, University of Strathclyde & Siemens Industrial Turbomachinery Limited
SupervisorHaofeng Chen (Supervisor) & Robert Hamilton (Supervisor)

Cite this