An Investigation of Fatigue Crack Growth in Thermally Cycled Components

Kerr, David Charles (1993) An Investigation of Fatigue Crack Growth in Thermally Cycled Components. PhD thesis, University of Glasgow.

Abstract

Fatigue Crack Growth In Thermally Loaded Components. The design of first wall components in a nuclear fusion reactor must take into account thermal cycling, through thickness temperature gradients and the possible presence of surface defects arising during construction or through plasma bombardment during service. This thesis describes the experimental procedures and the analysis performed in an investigation of the thermal fatigue crack growth behaviour of defective tubular components of the fusion reactor first wall material, ICL 167 SPH. To provide a basis for the investigation, a literature review is initially presented. The literature review introduces the process of fatigue failure and the important relationships and equations. Fatigue crack growth rate is identified as the parameter used to determine the component life, while the application of both linear elastic fracture mechanics and post yield fracture mechanics to thermal fatigue is discussed. Finally the metallurgy, both physical and mechanical properties and the behaviour of ICL 167 SPH under cyclic loading is presented. Both low cycle fatigue and linear elastic fatigue loading experiments were performed on standard specimen geometries to develop the material characteristics at the temperatures of interest. The experimental rigs, specimen development and method of data accumulation are described. The results are compared with available data for the similar Type 316L austenitic stainless steel and coefficients for the fatigue relationships produced. A thermal cycling rig was constructed to simulate the thermal loading of first wall tubular components. The development and instrumentation of the tubular components is described in conjunction with the adaptation of the direct current potential drop method which monitored the thermal fatigue crack growth. Beyond the influence of the crack initiating notches, the thermal fatigue crack growth rates were found to be similar from either the external or the internal surfaces of the components and were in a similar range to the resultant crack growth rates from the mechanical fatigue crack growth experiments. A thermal strain finite element analysis was performed to determine the values of stress and strain, through the thickness of a defect free, unnotched component, during a number of thermal cycles. The superposition method was applied to calculate the equivalent stress intensity factor at various crack depths through the thickness of the component. The difficulties in analysing thermal cyclic problems and the necessity for post yield evaluation were identified. Finally, it was concluded that mechanical fatigue crack growth rate data could be used to predict thermal fatigue crack growth rates in the thermal cycling loading of first wall tubular components.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: R C Hurst
• Keywords: Mechanical engineering, Nuclear engineering
• Date of Award: 1993
• Depositing User: Enlighten Team
• Unique ID: glathesis:1993-75304
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 21:16
• Last Modified: 19 Nov 2019 21:16
• URI: https://theses.gla.ac.uk/id/eprint/75304