Host: The Japan Society of Mechanical Engineers
Name : Dynamics and Design Conference 2018
Date : August 28, 2018 - August 31, 2018
It is important to evaluate fastening force of the bolt to detect bolt loosening in its early stages. This study proposes an evaluation method for fastening force of the bolt. The proposed method uses an ultrasonic pulse that transmitted through the bolt, and focuses on its instantaneous frequency. Our previous study has shown that only a vertically incident ultrasonic pulse is applicable to a titanium bolt in a block made with polymethyl methacrylate (PMMA), which is a dental implant like object. This paper reports a new technique with an obliquely incident ultrasonic pulse that is titled at 5 degrees in order to extend the application of the method. We identified the ultrasonic paths in the block and the bolt, and estimated the received pulse using a three-dimensional numerical simulation. The simulated pulse was affected by contact condition on the flank of the thread and shear deformation of the thread that come from the fastening force. The instantaneous frequency of the pulse that was virtually received at 5 mm lower than the front of the transmitter was sensitive to the flank contact condition and the thread deformation. Next, we experimentally demonstrated the technique for evaluating the fastening force of the bolt in the object. The instantaneous frequency of the pulse that was received at the suited position also varied depending on the fastening force.
