Open Access

ARTICLE

Relaxation of Residual Stress under Fatigue Load Described in Terms of Cyclic-Plastic Deformation Model

by S. Kwofie

1 Department of Materials Engineering, College of Engineering, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana

Structural Durability & Health Monitoring 2012, 8(4), 295-306. https://doi.org/10.32604/sdhm.2012.008.295

Abstract

Fatigue life of components may be enhanced by mechanical surface treatments, such as shot penning, which induce compressive residual stresses in the component's surface. Under cyclic/fatigue loads, however, relaxation of the residual stress may occur thus, reducing the optimum benefit of the surface treatment. For health monitoring / life prediction under such conditions it is important to be able to assess stress relaxation in real-time. However, the phenomenon of cyclic relaxation of residual stress is not well understood and its tracking during component operation is a technical challenge. By means of cyclic plastic deformation model and the Matlab/Simulink Program cyclic relaxation of residual stress is simulated. Simulated results show that residual stress relaxation under cyclic loading is associated with mean-strain shift, which is indicative of stress redistribution. The significance of this mean strain shift is briefly discussed in terms of tracking and quantitatively determining residual stress relaxation in real-time. Reduction in residual stress may be estimated as the product of mean-strain shift and the elastic modulus of the material.

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