TY - JOUR
T1 - Bolt-hole corner crack inspection using the photoinductive imaging method
AU - Tai, Cheng Chi
AU - Moulder, John C.
N1 - Funding Information:
This work was supported by the NSF Industry/University Center for NDE at Iowa State University. The authors gratefully acknowledge the contribution of Mr. Tauquir A. Khan in making measurements using the conventional eddy current imaging method. We would like to thank Dr. J. Chao of the Pratt & Whitney Company for providing several of the samples. We are also grateful to Mr. Brian F. Larson for preparing the fatigue crack samples. We are especially grateful to Dr. James H. Rose for first suggesting this study to the authors and for his helpful suggestions during the course of the investigation. Finally, the invaluable assistance of Dr. Norio Nakagawa in correcting the manuscript is gratefully acknowledged.
PY - 2000/9
Y1 - 2000/9
N2 - We applied a laser-excited eddy current (EC) imaging technique, or so-called photoinductive (PI) imaging, to characterize corner cracks at the edge of a bolt hole. Crack images with excellent signal-to-noise-ratios were obtained. The PI signals revealed the geometrical shape of the electrical-discharge-machined (EDM) notches that were either triangular or rectangular. The results show that this technique is promising to characterize the length, as well as possibly the depth and shape, of corner cracks. In this paper we present measurement results of 0.25-mm, 0.50-mm, and 0.75-mm rectangular and triangular EDM notches. We also show measurement results of a very small notch (<0.25 mm) which would be difficult to detect with conventional eddy current techniques. The dependencies of PI signals on laser chopping frequencies and eddy current frequencies are also examined. To demonstrate the photoinductive imaging capabilities to image actual cracks, we display images of fatigue cracks grown in a Ti-6Al-4V hole specimen. Finally, we present comparisons of the photoinductive imaging results with usual eddy current images obtained from a 0.75-mm triangular EDM notch using a rotating bolt-hole scanner. This article intends to verify experimentally that the photoinductive imaging technique has a potential to become a useful nondestructive testing method.
AB - We applied a laser-excited eddy current (EC) imaging technique, or so-called photoinductive (PI) imaging, to characterize corner cracks at the edge of a bolt hole. Crack images with excellent signal-to-noise-ratios were obtained. The PI signals revealed the geometrical shape of the electrical-discharge-machined (EDM) notches that were either triangular or rectangular. The results show that this technique is promising to characterize the length, as well as possibly the depth and shape, of corner cracks. In this paper we present measurement results of 0.25-mm, 0.50-mm, and 0.75-mm rectangular and triangular EDM notches. We also show measurement results of a very small notch (<0.25 mm) which would be difficult to detect with conventional eddy current techniques. The dependencies of PI signals on laser chopping frequencies and eddy current frequencies are also examined. To demonstrate the photoinductive imaging capabilities to image actual cracks, we display images of fatigue cracks grown in a Ti-6Al-4V hole specimen. Finally, we present comparisons of the photoinductive imaging results with usual eddy current images obtained from a 0.75-mm triangular EDM notch using a rotating bolt-hole scanner. This article intends to verify experimentally that the photoinductive imaging technique has a potential to become a useful nondestructive testing method.
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U2 - 10.1023/A:1026505625735
DO - 10.1023/A:1026505625735
M3 - Article
AN - SCOPUS:0034261919
SN - 0195-9298
VL - 19
SP - 81
EP - 93
JO - Journal of Nondestructive Evaluation
JF - Journal of Nondestructive Evaluation
IS - 3
ER -