In this study, in order to investigate the effect of humidity on the ultrasonic fatigue properties, ultrasonic fatigue tests were carried out in different conditions: dry air, saturated humidity and submerged in distilled water.
Ultrasonic fatigue testing was conducted using an ultrasonic fatigue testing machine manufactured by the University of BOKU, Vienna, Austria , as shown in Figure 3(a).
Ultrasonic fatigue testing was carried out in various environments with different RH (relative humidity) levels: dry air (RH<1%), saturated humidity (RH>99%) and submerged in distilled water.
In ultrasonic fatigue testing, tests performed in dry air resulted in the highest fatigue life and tests in distilled water resulted in the lowest fatigue life.
Obviously, ultrasonic fatigue testing in dry air has lowest water exposure and highest facets percentage.
For this aluminum alloy, the fatigue properties are different for tests conducted under ultrasonic fatigue (20 kHz) and conventional fatigue (30 Hz).
The percentage of facets observed on the fracture surfaces in ultrasonic fatigue testing correlate well with water exposure parameter (P/f); a high percentage of facets corresponding to low water exposure value.