Characteristic of slipping behaviour in vibratory wear of a supported tube

Fretting wear of a vibratory tube is studied from the investigation of the slipping characteristics on the contacts between the tubes and the supports. The primary application of the present research is the tube bundle structures subjected to a flow-induced vibration in the nuclear power plant components. Tests were carried out to simulate the vibration of the fuel rods, in particular, those supported by springs and dimples. Two typical types of supports were used at both ends of the tube, which was forced to vibrate with 30 Hz. The supporting condition was varied artificially: positive contact force or gap existence. During the tube vibration, the amplitudes were measured continuously in the vicinity of the supports. Simple equations were derived to evaluate the slip displacement on the contacts. Wear volume, area and the maximum depth of the wear scars on the tubes were investigated after 106 vibration cycles. As a result, it was found that the supporting condition affected the vibration characteristics near the contacts. In the positive contact condition, the phase difference of the vibration signals at both sides of the contact was 180°. It is altered in the gap condition and the multiple values of 30 Hz were found from the fast Fourier transform analysis. The high frequency vibration is thought to cause the wear to become severer in the gap condition. The support with dimples revealed more wear. The influence of the contact shape on the wear was discussed from this. The relationship between the slip displacement and the wear was also discussed together with a new wear parameter.