Static and Dynamic Fracture of Structural Steel.

Abstract

The present study is concerned with the assessnent of structural steel fracture toughness, as close to real service loading conditions as practically possible in the laboratory, using small scale specimens. The effects of stored strain energy content is evaluated for slow-static and dynamic COD tests for maximum load and cleavage instability. The literature reviews elastic-plastic fracture mechanics and goes on to study the effect of stored strain energy, the COD technique and dynamic testing procedures presently available. Static and dynamic fracture toughness testing using the COD technique is carried out on BS4360 - 50D structural steel in its normalised state. The testing procedures used closely relate to either the BS5762 COD standard or BS5447 plane strain standard. The specimen size tested is 2B =U= 24 mn, with a fatigue notch size of approximately a/W between 0.48 and 0.57. Photographic-macros and SEM fractography were carried out after the specimens were tested to assess the micromechanism processes operative during a fracture test. It is believed the present work is of special significance to determinate structural design using structural steel, for example with liquefied gas pressure vessels. The resulting test data available from this thesis is envisaged to be the closest approach to real service "true limit severity", and consequently is beneficial to fracture prevention technology.