Papers by Keyword: Low Cycle Fatigue Damage

Abstract: We have proposed a new cold processing method to enlarge the diameter of a short section of a metal shaft using a combination of a cyclic bending load and an axial compressive load that is lower than the yield stress of the sample material. We call this cold processing method the diameter-enlargement working method, and refer to the enlarged section of the processed shaft as the diameter-enlargement section. The processing method produces large plastic deformation, and its key features are as follows: the diameter-enlargement deformation progresses easily under a low axial compressive load at room temperature and the processed part exhibits little temperature increase. However, a crack is generated in the notch near the diameter-enlargement section during processing, and the cause is not yet clearly understood. Therefore, we conducted processing experiments to clarify the crack generation conditions, and simulated the working process using the finite element method to investigate the behaviors of stress and strain during processing. Furthermore, we calculated the low-cycle fatigue damage in the processed shaft using the Manson–Coffin expression. This study clarifies the mechanism of crack generation during processing and evaluates the fatigue strength of the processed part.

Abstract: Abstract: Based on the Miner′s linear accumulative damage theory and the low cycle fatigue damage parameter that is relative to the total strain amplitude and the mean stress of the plastic zone near crack tip, a new numerical simulation method to predict the fatigue crack growth (FCG) of materials is presented. The numerical FCG results for middle-cracked tension (MT) specimens of Cr2Ni2MoV steel, TA12 and TC4 alloys by ANSYS are closed to those by tests. Therefore, the new method has capability to give good FCG prediction accuracy for different materials. Furthermore, the Paris FCG models of TA17 and TC11 alloys were predicted by this method and can be referred to the key engineerings.

Abstract: Triaxiality function (Rv) has been known as one of the important factors that responsible for damage initiation in adhesive bonding. Damage evolution law for low cycle fatigue (LCF) is function of Rv, von Mises equivalent stress (Seqv) and number of cycles (N). From previous research, it was found that the Rv values of two cases: bulk adhesives and single lap joint (SLJ), were close to unity. Those values are uncontrollable. Meanwhile, the damage equation for general solution contains Rv as an independent variable. There is need to choose another joint type that can characterise Rv as an independent variable. This paper presents the choice of scarf joint as specimen that can simulate variation of Rv. Several types of adhesive joints have been modelled and analysed using ANSYS as finite element analysis (FEA) tool. In ANSYS, Rv values were calculated directly from direct output results: von Misses equivalent stress and Hydrostatic stress. From FEA, it was shown that Rv changed as a function of adhesive bondline angle of the scarf joint. The values of Rv are constant along adhesive line except at the free edges. This choice is better than Cleavage joint where the values of Rv are not constant along adhesive line due to the presence of bending moment.