1 WIRELESS SENSORS FOR DETECTION OF MAXIMUM STRAIN

Simple and inexpensive passive sensors that can monitor the peak strain or displacement were developed. The developed sensors have an ability to quickly assess the degree of damage in a structure when a checkup is needed. The sensors need no power supply for monitoring. The peak values can be read wirelessly if desired. In addition, they can be easily modified to measure other peak values such as acceleration and force. The mechanism to memorize the peak strain or displacement value relies on pure plastic extension of a sensing section. The pure plastic extension of the sensing section is made possible by controlling the boundary condition and compression resistance. The change in the length of the section is detected by a change in resistance, inductance or capacitance. In addition, introduction of an LC circuit into the sensor enables wireless reading. Extensive studies were made theoretically and experimentally for various configurations. The studies exhibit their feasibility to be used for civil and building structures