Prototype fatigue tests simulate in-place working condition of dynamic umbilicals which are usually conducted to verify the fatigue life. The fatigue failure hot spot locates on the top segment of the umbilical. The umbilical reaches a maximum curvature at the hot spot. The hot spot position of the umbilical is always inside or near the bend stiffener. The radial gap between the umbilical and the bend stiffener is very small, which makes it difficult to put traditional sensors in the gap. In this work, a prototype umbilical tension-bending test is conducted, and the optic frequency domain reflectometer (OFDR) technology is utilized to measure the distributed strain of the umbilical inside the bend stiffener. The curvature of the umbilical is obtained to locate the fatigue hot spot in order to verify the feasibility of this approach. The test results show that the umbilical curvature can be measured well with the use of OFDR technology. The influence of tension and swing angle on the position of the maximum curvature is studied. The method proposed in this paper provides a valuable approach for curvature monitoring in the application of dynamic umbilical fatigue tests.

中文翻译：

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在疲劳测试中使用 OFDR 技术测量动态脐带缆最大曲率的方法

原型疲劳试验模拟动态脐带缆的就地工作条件，通常用于验证疲劳寿命。疲劳失效热点位于脐带上段。脐带在热点处达到最大曲率。脐带的热点位置总是在弯曲加强筋内部或附近。脐带和弯曲加强筋之间的径向间隙非常小，这使得传统传感器难以放入间隙中。在这项工作中，进行了原型脐带拉伸弯曲试验，并利用光频域反射仪（OFDR）技术测量弯曲加强筋内脐带的分布应变。获取脐带的曲率以定位疲劳热点，以验证该方法的可行性。测试结果表明，使用OFDR技术可以很好地测量脐带曲率。研究了张力和摆角对最大曲率位置的影响。本文提出的方法为动态脐带疲劳试验中的曲率监测提供了一种有价值的方法。