Spectra thermal fatigue tests under frequency controlled fluid temperature variation; Strength tests

Kawasaki, Nobuchika ; Hasebe, Shinichi; Kobayashi, Sumio; Kasahara, Naoto

Thermal fatigue strength tests subjected to sinusoidal fluid temperature waves were performed by the SPECTRA test facility, where frequencies were 0.05, 0.2, and 0.5Hz. Cracks were observed on the inner surface of cylindrical test pieces after testing. 0.05Hz's wave caused a greater number of and deeper cracks than 0.5Hz's wave under the same fluid temperature range and the same fatigue cycles. The crack initiation region of the 0.05Hz's wave was larger than for the 0.5Hz's wave. Estimated fatigue failure cycles based on the frequency transfer functions were compared with test results. Frequency-dependency in failure cycles was observed through these test results, and frequency transfer functions could estimate this dependency. The test results supported the fatigue damage evaluation method with frequency transfer functions.