Axial structural damping behavior induced by internal friction and viscoelastic properties of polymeric layers may have an inevitable influence on the global analysis of flexible pipes. In order to characterize this phenomenon and axial mechanical responses, a full-scale axial tensile experiment on a complex flexible pipe is conducted at room temperature, in which oscillation forces at different frequencies are applied on the sample. The parameters to be identified are axial strains which are measured by three kinds of instrumentations: linear variable differential transformer, strain gauge and camera united particle-tracking technology. The corresponding plots of axial force versus axial elongation exhibit obvious nonlinear hysteretic relationship. Consequently, the loss factor related to the axial structural damping behavior is found, which increases as the oscillation loading frequency grows. The axial strains from the three measurement systems in the mechanical experiment indicate good agreement, as well as the values of the equivalent axial stiffness. The damping generated by polymeric layers is relatively smaller than that caused by friction forces. Therefore, it can be concluded that friction forces maybe dominate the axial structural damping, especially on the conditions of high frequency.

中文翻译：

---

无粘结软管的轴向力学实验

聚合物层的内摩擦和粘弹性引起的轴向结构阻尼行为可能会对挠性管的整体分析产生不可避免的影响。为了表征这种现象和轴向机械响应，在室温下对复杂的挠性管进行了全面的轴向拉伸实验，其中将不同频率的振荡力施加到样品上。待确定的参数是轴向应变，可通过三种仪器测量：线性可变差动变压器，应变仪和相机联合粒子跟踪技术。轴向力与轴向伸长率的对应曲线显示出明显的非线性滞后关系。因此，找到了与轴向结构阻尼行为有关的损耗因子，随着振荡负载频率的增加而增加。在机械实验中，来自三个测量系统的轴向应变以及等效轴向刚度的值显示出良好的一致性。聚合物层产生的阻尼相对小于摩擦力引起的阻尼。因此，可以得出结论，摩擦力可能是轴向结构阻尼的主导，特别是在高频条件下。