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A B S T R A C TThe effect of frequency on giga-cycle fatigue properties was investigated in smooth and 0.3 mm-hole-notched specimens at three heats (Heats A, B, and C) for a 900 MPa-class Ti-6Al-4V alloy. Fatigue tests were performed at frequencies of 120 Hz, 600 Hz, and 20 kHz using electromagnetic resonance, high-speed servohydraulic, and ultrasonic fatigue testing machines, respectively. Heats A and B developed internal fractures, and in these cases, frequency effects were negligible. On the other hand, Heat C developed only surface fractures. In this case, high-frequency tests showed a higher fatigue strength, indicating frequency effects were not negligible. The tests using the notched specimens showed almost no frequency effects regardless of the heat. The frequency effects observed in the cases of surface fracture were believed to be related to a delay in local plastic deformation in response to high-frequency loading, since temperature increases in these specimens were successfully suppressed. The delay in the plastic deformation was observed to be reduced in the notched specimens because of stress concentration and limitation in the plastic deformation zone. In turn, the significant conclusion of this research is that high-frequency tests can be applied not only to internal fractures but also to notch problems, but are not applicable to surface fractures of smooth specimens.

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This paper summarizes the NIMS fatigue data sheets and makes a new gateway available to access them. The NIMS fatigue data sheets are a huge database of the fatigue properties of structural materials. This project covers fundamental fatigue properties at room temperature and at high temperatures, and the fatigue properties of welded joints. The fundamental fatigue properties recorded include high-cycle, low-cycle and gigacycle fatigue test results for steels, aluminium alloys, titanium alloys and so on. The high-cycle fatigue test results determine the fatigue limits. The low-cycle fatigue test results reveal not only the fatigue lives but also cyclic stress-strain curves. The gigacycle fatigue tests were conducted at 100 Hz for three years up to 1010 cycles, as well as at 20 kHz for a week. The fatigue properties at high temperatures were evaluated chiefly for steels, via low and high-cycle fatigue tests. The low-cycle fatigue tests were conducted by employing various strain rates and waveforms. The fatigue properties of welded joints were evaluated using thick plates of steels and aluminium alloys, conducting high-cycle fatigue and crack propagation tests employing large specimens in as-welded condition. The high-cycle fatigue tests were conducted using various specimen sizes, welding procedures, stress ratios and so on. The crack propagation tests were conducted for the base metal, the weld metal and the heat-affected zone. Many new findings were obtained with these fatigue data as reviewed in this paper.