| 摘要 |
Internal defects formed within a substrate tire for manufacturing a retreaded tire are detected in a non-destructive manner by rotating the inflated tire at a constant speed of 1 r.p.m. while a displacement sensor is urged against an outer surface of the tire at different pressures to derive first and second sets of displacement signals, deriving displacement differences between the first and second displacement signals at corresponding measuring points on the outer surface of the tire, deriving a minimum value of the displacement differences, calculating deviations between the displacement differences and the minimum value, deriving the maximum deviation, and by comparing the maximum deviation with a first threshold value. When the maximum deviation exceeds the first threshold value, it can be judged that the tire includes a local separation. Further an average of the displacement differences is derived and is compared with a second threshold value. When the average of the displacement differences exceeds the second threshold value, it is judged that the tire includes a circumferential separation or fatigue. Moreover, a standard deviation of the displacement differences is calculated and is compared with a third threshold value. When the standard deviation exceeds the third threshold value, it is judged that the tire has the circumferential separation or fatigue.
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