弹性模量对深海立管涡激振动疲劳损伤的影响(英文)

Effect of Elastic Modulus on the VIV-induced Fatigue Damage in Deep Sea Risers

K.Vikestad文章中预报出的立管疲劳寿命特别长,经过仔细校核发现作者用于计算的弹性模量与试验值不同。是否这一错误会导致疲劳寿命的重要差别,本文对这一问题做了进一步研究。本文采用了与上述文章中类似的方法来重新计算立管的涡激振动疲劳损伤。利用作者所在课题组开发的涡激振动预报程序来确定立管动力响应,并假设涡激振动引起的长期应力范围分布是Rayleigh分布,运用Palmgren-Miner线性累积损伤准则来预报海洋立管涡激振动疲劳损伤。和依据试验测量数据计算得到的疲劳损伤以及VIVANA预报的结果比较表明,本文的预报方法是合理的。研究表明上述文章中过高的疲劳寿命是由错误的弹性模量引起的。结果显示,立管的弹性模量对于涡激振动疲劳损伤是个重要的参数。弹性模量越大,疲劳寿命越低。

The VIV-induced fatigue lives in deep sea risers predicted by Vikestad are extremely long, and by looking at their paper carefully it was found that the elastic modulus used in calculation is different from that in experiment. Whether this mistake could lead to significantly different fatigue life is worth studying. In this paper, a similar method as that used by Vikestad is adopted to recalculate the fatigue lives of deep sea risers.Assuming that the long-term stress ranges are nar row-banded and close to a Rayleigh distribution, the Palmgren-Miner linear damage accumulation rule is adopted to predict the VIV-induced fatigue damage.The VIV response is estimated using the VIV prediction program developed by authors＇ group. Compared with the results calculated directly from the measured experimental data and those from VIVANA, the present method is in reasonable agreement with these two methods for predicting the VIV-induced fatigue damage of marine risers. Results show that the over-predicted fatigue life by Vikestad is caused by the wrong elastic modulus. It is found by comparison that the elastic modulus has great effect on the VIV-induced fatigue damage. The larger the elastic modulus, the lower the fatigue life. Hence, the elastic modulus is a key parameter for the VIV-induced fatigue damage.