A simple repair method of fatigue cracks using stop-holes reinforced with wedge members: applicability to reinitiated cracks and effects of an anti-fatigue smart paste

ABSTRACT

A simple method of repairing fatigue cracks using stop-holes reinforced with wedge members, that was previously proposed by the author, has been examined for the case of reinitiated cracks. By using this method, the stress intensity factor range around a reinitiated crack tip is expected to be reduced by the wedge load effect of the wedge members. The chief advantages of this method are that the repair work can be easily performed from only one side of a cracked structure, and that the wedge member can be set so adaptive as to maintain the wedge load automatically and effectively as the reinitiated crack grows. Specifically, slope-type wedge members have been adopted, and an adaptive mechanism of the wedge member has been devised using a pulley and a wire-type displacement metre. Fatigue tests were performed on a steel plate specimen with a drill hole and a notch, and validity of the above repair method was experimentally examined using both of simple and adaptive wedge members. In addition, an anti-fatigue smart paste, which consists of fine alumina particles and silicone grease, was applied to the periphery of the drill hole, and its effects on automatic restraint and visual detection of crack growth were investigated. FE analyses using contact elements were also carried out for a comparative study. As a result, it was found that the strain range on the specimen side is reduced to 44.0 % and the fatigue life is prolonged by 12.4 times by application of the adaptive wedge member as compared with the case of the conventional stop-hole. As for the anti-fatigue smart paste, it was found that the fatigue life is further prolonged by about three times as compared with the case of the adaptive wedge member and the paste has an evident function to facilitate visual detection of cracks.

KEYWORDS:

• Fatigue crack
• repair method
• stop-hole
• wedge load
• adaptive wedge
• anti-fatigue smart paste
• reinitiated crack
• crack growth

Acknowledgements

Suga Aoi of the Ocean Engineering Department, National Maritime Research Institute provided valuable cooperation in the performance of these fatigue tests and data handling and I would like to express my sincere gratitude for this here.

Additional information

Funding

The original study was supported by a JSPS Grant-in-Aid for Scientific Research [JP17K06548] and I would like to express my gratitude for this here.