RIA: Dynamic Loosening and Tightening of Threaded Fasteners by Vibration

螺纹紧固件在许多系统和结构中普遍使用。虽然经常被忽视，紧固件代表了一个复杂的，往往是关键的设计元素。在某种程度上，所有紧固件都承受非定常载荷。然而，在这种条件下螺纹紧固件的行为仍然知之甚少。现有的螺纹紧固件振动分析是基于静态平衡条件，支持数据仅限于低频条件。这样的分析表明，只有净松动才会发生。然而，初步的实验表明，当考虑到大范围的振动条件时，发现在交替的频率范围内发生松动或拧紧作用。本研究的目标是在广泛的动态条件下对螺纹紧固件的动态力和运动进行良好的控制测量，并建立适当的螺纹紧固件非线性动态模型，以捕获和解释动态松动和拧紧运动。这些模型将适应摩擦和振动的相互作用，以及螺纹部件固有的动态约束和非线性。这项工作的结果预计将具有基本的工程兴趣，并在许多关键应用的接缝设计中立即使用

Threaded fasteners have found ubiquitous use in many systems and structures. Although frequently overlooked, fasteners represent a complex and often critical design element. To some extent, all fasteners are subjected to unsteady loading. Yet the behavior of threaded fasteners under such conditions is still poorly understood. Existing analyses of threaded fasteners under vibration are based on static equilibrium conditions with supporting data limited to only low-frequency conditions. Such analyses suggest that only a net loosening action can occur. However, preliminary experiments show that when a broad range of vibratory conditions are considered, alternate ranges of frequencies are found in which either a loosening or a tightening action occurs. The goals of this research are to perform well- controlled measurements of the dynamic forces and motions of threaded fasteners under a wide range of dynamic conditions and to develop appropriate nonlinear dynamic models of threaded fasteners which capture and explain the dynamic loosening and tightening motions. The models will accommodate the interaction of friction and vibration as well as the dynamic constraints and nonlinearities inherent to threaded components. The results of the work are expected to be of fundamental engineering interest and have immediate use in the design of joints in many critical applications.***//