Development of Testing Equipment for Tightening Characteristics Evaluation

评估轴承表面与配合螺纹之间摩擦特性的紧固试验是保持螺栓连接可靠性的唯一途径。然而，传统的试验机在精度、适用性、刚性等方面存在一定的问题。本研究旨在开发有可能解决这些问题的新设备。用于该设备的压电式力传感器具有两大优点，一是其刚度比传统称重传感器大7倍左右，二是精度和线性度非常高，且与被测范围无关。另一方面，应明确偏心放置和预加载传感器的特性。实验和有限元分析表明，传感器表面的压力分布影响灵敏度值，但线性度保持理想值，因此轴向力传感器可以作为该设备的测压元件。在对扭矩测量结果的评价方面，对具有四个剪切力传感器的扭矩传感器的结构进行了研究。结果表明，由于制造和安装阶段产生的误差引起的轴向力串扰影响了剪切力传感器的虚拟灵敏度。然而，这样的串扰可以被控制成正比的轴向力，并可以通过计算进行补偿。最后，验证了采用新设计的具有12个传感器的称重传感器单元进行足够精度的拧紧实验的可能性。

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.