Development of Testing Equipment for Tightening Characteristics Evaluation

紧固试验是评价螺纹与支承面间摩擦特性的唯一方法，是保证螺栓联接可靠性的重要手段。然而，传统的试验机在精度、适用性和刚性方面存在一些问题，本研究旨在开发新的设备，有可能解决这些问题。用于该设备的压电式力传感器具有两个优点，即它们的刚度比传统的测压元件大约7倍，并且精度和线性度非常高并且与待测量的范围无关。另一方面，应阐明偏心放置和预加载的传感器的特性。实验和有限元分析表明，传感器表面的压力分布对传感器的灵敏度有影响，但线性度保持在理想值，轴向力传感器可以作为该装置的称重传感器。在扭矩测量评价方面，对四个剪切力传感器的扭矩传感器结构进行了研究。结果表明，由于制造和安装过程中产生的误差而引起的轴向力串扰会影响剪切力传感器的虚拟灵敏度。然而，这种串扰可以被控制为与轴向力成比例，并且可以通过计算来补偿。最后，确认了通过使用新设计的具有12个传感器的测力传感器单元以足够的精度进行紧固实验的可能性。

Tightening experiments for evaluating frictional characteristics between bearing surfaces and mating threads are, the only way to maintain the reliability of bolted joints. However, the conventional testing machines have some problems in terms of the accuracy, applicability and rigidity.This study aims to develop the new equipment having the possibility to resolve such problems. The piezo electric force sensors to be used for the equipment have two advantages that the rigidity of them is about 7 times larger than conventional load cell, and that the accuracy and the linearity are very high and are independent of the range to be measured. On the other hand, the characteristics of the sensor eccentrically placed and preloaded should be clarified. Experiments and analytical investigations 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 this equipment.As for the evaluation for the torque measurement, the investigations were done for the torque cell construction with four shear force sensors. As a result, it was clarified that the cross talk of the axial force due to the errors generated in both manufacturing and installing stages affects the virtual sensitivity of shear force sensors. However, such a cross talk can be controlled to be proportional to the axial force, and can be compensated by calculation.Finally, the possibility to perform the tightening experiment with sufficient accuracy by using the newly designed load cell unit with 12 sensors was confirmed.