An investigation on the ductile damage evolution law of high-cycle fatigue

Abstract

Continuum damage mechanics (CDM) opens up a new method to deal with fracture problems in structures. This approach treats rupture by means of an equation of damage evolution and the critical damage value of a material. There is, therefore, a need to develop a reliable model of damage evolution and to measure the critical damage variable accurately under different loading conditions. However, these are sometimes very difficult. In this paper, an investigation is made of the ductile damage evolution law of high-cycle fatigue. The results of experimental studies, both a multi-specimen test and a single-specimen test, clearly show that the variations of the damage variable D with the cyclic ratio n/N ƒ or the time ratio n/ N <. zhfl; fit excellently to the power law. Moreover, the critical value of damage variable D c of high-cycle fatigue for 40Cr steel is deduced based on the power law and is much less than D c of static tension. This indicates that the critical damage value of materials is loading condition dependent.