Abstract

MATHMATICAL ANALYSIS OF FATIGUE DISPLACEMENT DISCONTINUITY IN CRITICAL STRUCTURAL COMPONENTS UNDER CYCLIC MONOTONIC AMPLITUDE LOADING USING MODIFIED EXPONENTIAL MODEL

Onwubuya, M. N. and Oyesanya, M. O.

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Abstract Dissipation of energy in critical solid components is a critical issue, it is the single largest cause of damage in metallic structural materials. The risk of structural fatigue failure due to progression of displacement discontinuity as the major cause of structural defect, collapse, crashes, explosive decompression, breakup and disintegration of components of cyclic monotone amplitude. Adequate understanding of fatigue failure mechanism becomes determinative and necessary, failure modes, safety, and service life of the element are to be accurately determined and safely monitored; hence this paper, presented modified exponential model on mathematical analysis of fatigue displacement discontinuity in assessing critical structural components under cyclic monotonic amplitude. The study adopted the principles of power law, numerical integration technique and exponential differential equation growth model and its modification for better and accurate prediction. In the study, analysis showed that gives the estimate of the fatigue life of the structural component; describes the number of cycles required to propagate a crack from initial crack length to critical length and m expresses the specific crack growth rate in the interval i to j where signifies the fatigue life of the structural component under monotonic displacement loading. Under the modified model, the paper revealed that the fatigue crack growth trend fitted adequately with the fourth order polynomial equation for second and third regime when the values of curve fitting constants were determined; for 4th polynomial is a function of initial flaw magnitude and material used. The modified exponential differential equation model present a simple way of evaluating fatigue life of structural component compared to complicated numerical integration approach and the exponential model for fatigue life prevision in terms of crack growth rate. Keywords: Fatigue, displacement discontinuity, cyclic monotonic amplitude, displacement and loading

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