Abstract
There are many problems in the fatigue cracks for the expressway since the high economic growth period. These damaged parts have been increasing tendency every year recently. 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 using strain gauges. To overcome this problem, the piezo-electric material with high mechanical strength is used by measuring as strain gauges. The comparison examines whether to relate the timing that becomes unstable destruction from the stability destruction. The strain gauges and the piezo-electric material generated the voltage measure the strains around the cracks. We produce the crack growth by the liberating energy method.
