Use this URL to cite or link to this record in EThOS:
Title: Crack growth behaviour in austenitic stainless steel components under combined thermal fatigue and creep loading
Author: Gandossi, L.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2000
Availability of Full Text:
Access from EThOS:
This thesis describes the work carried out in an investigation of crack growth behaviour in 316L steel hollow cylindrical components subjected to conditions of thermal fatigue interacting with creep. Type 316L austenitic stainless steel is a widely used material for high-temperature structural components such as heat exchangers. A thorough knowledge of its behaviour in the presence of severe cyclic loading with dwell times at high temperature and under the superimposition of sustained mechanical loads is highly desirable. A review of the relevant literature background, necessary to understand both the fatigue and creep mechanisms in relation to crack initiation and growth, is given. Physical and mechanical properties of the material under examination are then presented. The design and construction of a unique experimental facility able to reproduce the required conditions of creep/thermal fatigue interaction is described. In order to generate the required temperature gradients, induction heating was used to cyclically heat the external surface of thick-walled cylindrical component between 80° and 600°C while the internal surface was cooked by water flow. A mechanical load could be axially introduced in the specimen by means of a dead-weight creep machine. Artificial defects, simulating actual stress concentrators in real components, acted as crack starters. The direct current potential drop method was used for in-situ real-time crack growth monitoring. A significant experimental activity was completed under a combination of varying experimental parameters, such as hold time, severity of the thermal shock and primary load. Numerical methodologies were applied to predict stress fields during cycling and to assess cracking rates. Fracture mechanics crack tip parameters were evaluated. An "effective" stress intensity factor range proved to yield satisfactory results in correlating the experimental data. A general discussion in which the experimental results are analysed is given. Finally, the principal findings are summarised and some areas for future investigation proposed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available