基于压电传感的螺栓球节点连接状态监测

螺栓球节点具有安装方便、受力性能合理等优点,被广泛应用于各类大跨度空间结构中。然而,安装时杆件错位、螺栓假拧和使用过程中材料老化等问题会使节点连接发生松动,导致结构承载力下降,甚至坍塌;另一方面,连接螺栓位于螺栓球节点内部,从外部很难察觉内部螺栓连接发生了松动,造成节点连接状态监测难。该文提出了一种基于压电传感的螺栓球节点连接松动状态监测方法,通过在螺栓球和杆件上外贴压电陶瓷片,分别作为驱动器和传感器,利用压电陶瓷材料的正、逆压电效应,基于时间反演技术对螺栓球节点连接松动状态进行监测。设计制作了一个螺栓球网架模型,利用对套筒施加不同的扭矩来模拟螺栓球节点的不同松紧状态,通过模型试验,基于节点松动前、后压电陶瓷片接收到的聚焦信号峰值的变化,实现对螺栓球节点连接松动状态的监测。试验结果表明,该方法具有一定的有效性、可重复性和良好的抗噪性。

Monitoring of Connection State of Bolt Spherical Joints Based on Piezoelectric Sensor

The bolt spherical joints have the advantages of convenient installation and reasonable mechanical performance, and are widely used in various large span spatial structures. However, the problems such as dislocation of rods, false tightening of bolts and material aging during use will make the joint connection loose, leading to the decline of structural bearing capacity and even collapse; on the other hand, the connection bolt is located inside the node, so it is difficult to detect the looseness of internal bolt connection from the outside, which makes it difficult to monitor the joint connection state. In this paper, a method for monitoring the looseness state of bolt spherical joints based on piezoelectric sensor is proposed. By pasting the piezoelectric ceramic plates on the bolt spherical and the rod as the actuator and sensor respectively, and the positive and negative piezoelectric effect of piezoelectric ceramic material is used to monitor the looseness state of bolt spherical joints based on the time inversion technology. A bolt ball grid model is designed and manufactured. The different torques is applied to the sleeve to simulate the different tightness states of the bolt spherical joints. Through the model test, based on the change of the peak value of the focusing signal received by the piezoelectric ceramic chip before and after the node loosening, the monitoring of the looseness state of the bolt spherical joints can be realized. The experimental results show that the proposed method has certain effectiveness, repeatability and good noise resistance.