Use this URL to cite or link to this record in EThOS:
Title: A numerical investigation of geometry effects in the measurement of cleavage fracture
Author: Chiravachradej, J.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2000
Availability of Full Text:
Access from EThOS:
The main objective of this dissertation is to investigate whether modified Charpy specimens can be used instead of the standard fracture mechanics specimens (FS) to measure a material's fracture toughness. Two additional cracks are proposed for the modification; an electric discharge machined crack (EDM) which has a 0.1 mm width, and a fatigue crack (FA) which has virtually zero crack width. The investigation concentrates on the effects of size and crack geometry on the fracture toughness and brittle-to-ductile transition temperature, using published theories and a method developed during the course of this investigation. All theories agree that the effect of the geometry size and crack geometry, either individually or in combination, makes the EDM and FA behave differently from the FS geometries. The EDM geometry is found to have higher fracture toughness at a given temperature and lower Tt than the FS geometries. The comparisons between the FA and FS geometries are more complicated because not all theories agree. However, in general, all theories agree that the effect of specimen size is sufficient for FA geometry to have a different behaviour from the FS geometries. Although these findings do not favour the direct use of experimental results from the modified Charpy geometries for fracture assessment of an actual structure, they do not eliminate the possibility of their use. Each theory suggests some parameters that can be considered material properties, i.e. uninfluenced by the geometry size, crack shape, etc. Although some of these parameters are influenced by geometry, etc. this work shows that it should be possible to find the relationship between these parameters and the geometry, and hence provide a way for fracture assessment of an actual structure using small specimens.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available