抄録
Bolted joints are commonly used for many machines and structures. They sometimes suffere bolt loosening and may sometimes induce accidents. Therefore, bolt loosening detection techniques are essential for many machines and structures having bolted joints. Authors have proposed a new bolt loosening detection sensor using a natural frequency of a thin plate. The natural frequency is identified by admittance of piezoelectric elements attached to the plate without human commitments. However, this method requires function generator, voltage-current measurement circuit, A/D converter and computer with data processing software to identify the natural frequency. In this paper we propose an oscillator circuit which include piezoelectric elements as an easier natural frequency identification method. The oscillating frequency of the circuit is determined by the natural frequency of the plate. The relation between axial tension of the bolt and oscillating frequency is measured experimentally and validity of proposing method is confirmed.
