ULTRASONIC FATIGUE TEST METHOD FOR TESTING OF CAST ALUMINUM

Experiments were conducted to determine the gigacycle fatigue behavior of cast Aluminum AS5U3G-Y35 by ultrasonic fatigue test system. Specimens were tested at 20?kHz and 35?Hz with stress ratios of R=-1 and R=0.1. The S-N curves between 10 4 and 10 10 cycles were obtained. The experimental results show that fatigue failure can occur over 10 7 cycles, and the fatigue endurance stress continues to decrease with increasing number of cycles to failure between 10 7 and 10 10 cycles with R=-1, the fatigue endurance stress did not decrease after 10 8 cycles with R=0.1. The experimental results tested at frequencies of 20?kHz and 35?Hz respectively show that there is no apparent difference below 10 7 cycles. That is, there is no frequency effect on the fatigue properties of cast Aluminum AS5U3G-Y35. Scanning electron microscopy is used to examine the fatigue crack surface. The small voids are distributed in the material, and most fatigue crack emanate from the voids.