We developed a novel technique for bolt tightening control by utilizing SrAl2O4:Eu (SAOE) paint film to detect axial force generated during bolt tightening. Conventionally, torque method is prevalently used for bolt tightening control. The major problem of this method which indirectly controls the axial force in bolted joints is that only a small proportion of the torque actually contributes to the bolt extension. It is the axial force due to such an extension that fastens the bolted joints. Therefore, it is urgently necessary to directly measure the axial force in order to realize a smart tightening control. Considering the extension of bolt during tightening can induce elastico-luminescence of SAOE if it is painted on the bolt or washer, we have painted SAOE/polymer film on the washer and consequently measured elastico-luminescence of SAOE film while tightening the bolt under various conditions. In the present work, we also demonstrated the correlation between the elastico-luminescence intensity and tightening conditions including tightening speed and strain as well as axial force.
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