Fundamental Research on a development of CFRP Riser Pipe for 4000 m Deep Sea Scientific Drilling

日本建造了一艘深海科学立管钻探船“Chikyu”，计划在不久的将来在4 000米水深的海底钻探，以获取地幔。然而，在4000 m水深处使用钢制立管几乎是不可能的，因此需要发展CFRP立管。CFRP立管的关键元件是其机械结构，其中CFRP管在管端通过几对相互接触的螺纹连接到钢连接器。本研究就是围绕这一新型CFRP立管的研制而展开的，在2005年的研究中，对机械结构的结构和尺寸进行了参数化的改变，并通过有限元分析明确了其对机械结构强度的影响，对CFRP立管的机械结构进行了优化。在2007年的研究中，制作了优化尺寸的CFRP立管拉伸试验模型，并进行了拉伸试验，得到了该模型的拉伸强度、延伸率和应变。通过对CFRP管段的损伤观察，假设裂纹扩展通道，通过有限元分析得到的计算应变与实验应变的相关性，明确了机械结构的断裂过程，并在此基础上总结了4000 m深海CFRP立管的设计思路。

A deep sea scientific riser drilling vessel "Chikyu" was constructed in Japan and it is planned to drill the sea floor at the water depth of 4000 m to obtain the mantle in the near future. However, it is almost impossible to use the steel riser pipe at the water depth of 4000 m and the development of CFRP riser pipe is desired. The key element of the CFRP riser pipe is its mechanical structure where the CFRP pipe is connected at the pipe ends to the steel connectors through several pairs of mutually contacting threads. This research is concerned with the development of this type of CFRP riser pipe.In the research of 2005, the configuration and dimension of the mechanical structure were parametrically changed and their influence on the strength of the mechanical structure was made clear using FEM analysis and the optimization of the mechanical structure of the CFRP riser pipe was performed. The characteristic of the axial vibration of the optimized CFRP riser pipe was also studied and it was confirmed that the riser pipe had no resonance with the heaving of the drill ship.In the research of 2007, a tensile test model, which had the optimized dimension, was fabricated and tested and its tensile strength, elongations and strains were obtained. The fracture process of the mechanical structure was made clear from the correlation between the experimental strains and the calculated strains which were obtained from FEM analysis with assuming crack propagation passes based on the damage observation of the CFRP pipe section.Based on the results stated above, the thinking concerning the design of the CFRP riser pipe for 4000 m deep sea has been summarized.