Abstract
There are many problems in the fatigue cracks for the expressway built since the high economic growth period. These damaged parts have been increasing tendency every year. We consider that the budget can be reduced by planning to repair for strategy forecasting the crack growth. However, when the fatigue cracks happened the high cycle fatigue cannot be endured with a usual strain gauge. To overcome this problem, the PVDF film with high mechanical strength is used by measuring as strain gages. The comparison examines whether to relate the timing that becomes unstable destruction from the stability destruction. The strain gauges and the PVDF films generated the voltage measure the strains around the cracks. We guess the crack growth by the liberating energy method.
