Evolution of Engineering Principles for Fracture-Safe Design of Steel Structures

Abstract

An interpretive review is presented of the development of scientific knowledge of fracture processes and of the technological application of this information to the evolution of engineering principles for fracturesafe design. The review is in the format of a chronological exposition of the successive advancements in the state of knowledge relating to both the mechanical and metallurgical aspects of the subject. The consolidation of these aspects emphasizes that fracture-safe design practices are not separable into metallurgical and mechanical aspects, but rather involve detailed engineering consideration of both factors. The evolution of modern fracture-safe design technology has Its origins in the broad-scope research activity period of the 1940's. The results of the early research provided an enduring base on which more selective studies were evolved in the ensuing decades. The evolution of significant fracture toughness characterization test methods and of procedures for their analytical interpretation, with respect to both metallurgical quality and mechanical aspects, paced the rate of progress during this time period. In this report a detailed description is provided of these various tests, with separation as to types which were primarily of research interest as compared to those which emerged as suitable for general engineering usage. The theoretical bases for analytical translation of laboratory test data to structural performance factors are discussed, with particular reference to the subject of fracture mechanics. The role of metallurgical factors is described in relation to microfracture processes which determine the macroscopic engineering properties. PROBLEM STATUS This is a special summary and interpretative report covering the results of a wide spectrum of investigations within the Metallurg/Division of NRL. These investigations are aimed at the general problem of metallurgical optimization andfracture-safe design. The major portions of the studies are continuing under the established problems.

Fracture Mechanics of Ship Structures

“…More importantly to other investigators was the difference in transition temperature as seen by a Charpy test compared to transition as seen by other tests. Thicker specimens were needed, which led to the Drop Weight Tear Test (DWTT) of Pellini and Puzak (1963), and the Dynamic Tear (DT) test of Pellini (1969), which measure energy from much larger specimens. The DT specimen is similar to the Charpy Vnotch in that it has a machined notch and is impacted by a swinging hammer.…”

Significance of Charpy-V Test Parameters as Criteria for Quenched and Tempered Steels

“…From linear elastic fracture mechanics and the R•tioo Analysis Diagram (RAD) concepts for fracture toughness characterization (28,29), it is recognized that steels of increasing yield strength require higher values of Cv energy to give comparable structural performance. If a given value of LE is indicative of constant level of toughness, regardless of yield strength, then it must provide the same static or dynamic ratio of KId/ d. Note that it is the ratio (a measure of plastic zone size) and not the absolute value of KIc that determines structural behavior.…”

Numerical simulation of underwater explosion bulge test

“…Failure criterion was either physical failure of the weld joint by the appearance of a crack or the required reduction in thickness. Pellini [11] demonstrated the effect of temperature on the plastic deformation of weld panels when subjected to explosive loading. The ductility of the plates decreased with decrease in temperature and a behaviour similar to the energy absorption of Charpy's V-notch specimen as a function of temperature was observed.…”