Masters Theses

Kang Lee

Date of Award

8-1990

Degree Type

Thesis

Degree Name

Master of Science

Major

Engineering Science

Major Professor

J. D. Landes

Committee Members

T. G. Carley, W. E. Scott

Abstract

The LMN normalization method introduced by Landes et al. has been used successfully to develop J-R curves from load versus displacement records without crack length measurement. This method uses a so-called LMN function to describe the plastic deformation curve, which gives an unique relationship between load, plastic displacement and crack length. It not only eliminates the need for crack length monitoring equipment, therefore providing a method for more easily conducting and evaluating J-R curve tests; but it could be useful for tests conducted under some special conditions such as in hot cell testing or dynamic testing, or even in a facility with limited instrumentation. One proposed application of the LMN normalization method is for developing J-R curves from load versus crack length records where displacement measurements cannot be made. This could be important, for example for conducting and analyzing a J-R curve test in a hot cell. In order to do this some additional details of the method must be developed. The key in such a case is how to determine the LMN function for each test specimen. This study tries to use the material flow properties to predict some calibration points on the plastic deformation curve for the determination of the LMN function. Three approaches are proposed. These are applied to different test specimens which include a 10 to 1 difference in size and several different metallic materials. These tests were conducted and analyzed previously by the elastic compliance method and also analyzed by the LMN normalization method from records where both load and displacement were available. The new results are compared with those from both earlier analyses. This study describes the development of the new features of the three approaches and shows examples of how well they work. One approach in particular, the power law approach, is found to work best. The results from this approach are found to be consistent with those from the earlier analyses which use the compliance and complete normalization methods. Finally the use of the new approaches for the ASTM J-R curve test is discussed.

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