Abstract
Visual observations of fatigue crack propagation of a low alloy steel in an autoclave filled with pressurized water at high temperatures simulating a boiling water reactor environment were conducted. The observation system consisted of a distant focusing relay lens, a camera and a picture control device. A sapphire single crystal rod was employed as solid light path in high temperature water in order to reduce the image distortion due to convection. Observations were carried out at temperatures ranging from room temperature to 288°C. The total resolution power of the observation system decreased with increasing temperature but satisfied a requirement of ASTM standard even at temperature of 288°C.
Crack growth curves were successfully obtained from the successive pictures and compared with those obtained by a compliance method using LVDT for the same specimen. A good coincidence was obtained between both measurements.
