Development of nondestructive techniques for micro-damages; Application of ultrasonic detection method for evaluation of creep-fatigue damage

Kawasaki, Hirotsugu

In order to develop remaining life assessment of FBR plant, application of nondestructive detection for creep-fatigue damage are studied. To evaluate remaining life from early stage of life, nondestructive detection technology was needed to detect for micro-damage. So, the ultrasonic detection system generated burst wave-form which was used effective frequency analysis, was applied to evaluate damage for the specimen with pores imitated cavity which was creep-fatigue damage dominantly and the specimen of creep-fatigue damage. The feasibility for creep-fatigue damage detection and the estimation parameter for quantitative damage detection from bottom echo were evaluated. The results are as follows. (1)The ultrasonic detection were carried out for three types specimen with pores imitated cavity. It was found that ultrasonic velocity was not changed dearly for area fraction of pore below 10. (2)The peak frequency of power spectrum on pore specimen's bottom echo was decreased with increasing area fraction of pore. In case of 50MHz sensor, the difference of peak frequency became more clear. (3)The ultrasonic detection was also carried out for several interrupted specimens under creep-fatigue loading. The peak frequency of power spectrum on creep-fatigue specimen's bottom echo was decreased with progressing creep-fatigue damage. (4)Area of Fourier frequency range as evaluation of damage parameter was decreased with increasing area fraction of pore and with progressing creep-fatigue damage, It was found that this parameter was evaluated for the difference of damage at the early stage of creep-fatigue life.