Abstract
Tightening experiment for evaluating tightening characteristics is one of the most important issues to boost the reliability of bolted joints. However, the conventional testing machines have some problems in terms of the accuracy, the applicability and/or the rigidity to perform the experiment specified in ISO/DIS 16047. This study aims to develop the new equipment having the possibility to resolve such problems. The piezo electric force sensors to be used as the load cell and the torque cell have advantages that the rigidity is about 7 times lager than conventional ones, and that the accuracy and the linearity are very high and independent of the range to be measured. On the other hand, the characteristics of the senor eccentrically placed and preloaded have not been clarified. Experiments and analytical investigation using FEM have shown that the pressure distribution on the sensor surface affects the sensitivity value but that the linearity remains its ideal value, and it is concluded that the axial force sensor can be used as the load cell for tightening experiment. As for the torque measurement, it was clarified that the cross talk of the axial force on shear force sensors due to manufacturing and installation errors affects the virtual sensitivity. However, such a cross talk can be compensated by calculation, and finally the possibility to develop the newly designed load cell / torque cell unit with sufficient accuracy was confirmed.
