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Abstract

Low cycle fatiguetests at elevated temperatures under several types of saw-tooth wave strain cycling were carried out on two steels, a low carbon steel and an austenitic stainless steel, in order to investigate the effect of the difference in strain rate between tension going and compression going periods on the fatigue life.For both steels, the fatigue life was found to be longest under the strain cycling with equal tension going and compression going periods, and it became shorter as the difference between the two periods became larger. These results of fatigue life can be explained by the following damage concept.

Influence of Temperature and Dwelling Time on Low-Cycle Fatigue Characteristic of Isotropic Conductive Adhesive Joint

“…On the other hand, a grain boundary damage (gain boundary sliding) induced by creep deformation reduces fatigue life of polycrystalline materials at high temperatures (>0:5T m ). [16][17][18] The conductive adhesive, however, used in this study is not polycrystalline material that leads to a grain boundary sliding. Hence, the fatigue life was not degraded at the temperatures above the glass transition point, and then the fatigue life was kept at a higher level compared with the life at 298 K due to enhanced ductility.…”

Influence of Asymmetrical Waveform on Low-Cycle Fatigue Life of Micro Solder Joint

“…[6][7][8][9] Plastic strain primarily damages the grain interior, whereas creep strain primarily damages the grain boundaries in the polycrystalline state. In high-temperature low-cycle tension-compression fatigue tests performed on conventional specimens of SUS304 steel by Taira et al, hightemperature low-cycle fatigue using symmetrical triangular waves caused grain boundary sliding; however, almost no residual grain boundary sliding remained at the end of a cycle since the grain boundaries slid in a reversible manner during the tension-compression process.…”

“…[6][7][8] For example, Taira et al found in hightemperature low-cycle fatigue for low-carbon steel (S15C) and stainless steel (SUS304) that fatigue life under asymmetrical triangular strain waveforms was shorter than that under symmetrical triangular strain waveforms. 9 Studies using large specimens of the Sn-Ag-Cu alloy have also shown that fatigue life under asymmetrical waveforms was shorter than that under symmetrical waveforms. 10,11 These reports conclude that the reductions in fatigue life under asymmetrical waveforms were caused by accumulation of irreversible grain boundary sliding resulting from the asymmetry in the rate of deformation.…”