Date of Award

1981

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

Abstract

Neuber's rule which relates the stress and strain concentration factor at a notch to the theoretical stress concentration factor for a monotonic loading case. It is currently being used in a modified form to analyze cyclic loading cases. The purpose of this research was to experimentally measure the four quantities incorporated in Neuber's cyclic relation so that a direct evaluation of the relation could be made. Three of the parameters were measured during tests lasting a thousand cycles on notched specimens run under completely reversed load control. These three were the stress and strain in the specimen far removed from the notch and the strain at the edge of the notch. The latter value was obtained using a novel laser based interferometric technique. The fourth parameter, stress at the notch, was inferred from load data taken on a small, smooth specimen which was subjected to the strains measured at the notch. These measurements were conducted on specimens manufactured from three different materials, with two notch geometries, and run at both room and elevated temperatures. After having recorded this data, Neuber's rule was used to compute a value for numerous cycles of each test which was then compared to the theoretical stress concentration factor. Results showed that Neuber's parameter was generally less than the stress concentration factor regardless of material, notch geometry or temperature and is, therefore, a conservative design criterion.

Pages

152

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