Sea states effects on fatigue damage of large ship prone to springing effect
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摘要:
目的 针对大型船舶波激振动效应下的疲劳损伤问题进行研究。 方法 通过船模试验方法，比较两代400 000 DWT超大型矿砂船（VLOC）疲劳损伤的试验结果，分析船体梁波激振动效应下海况与疲劳的关系。通过递推方法，研究系列模型下的典型海况影响。 结果 结果表明，波激振动对疲劳的放大效应与有义波高和遭遇周期存在趋势关系。通过归纳递推方法，提出“主导海况”的概念，对疲劳损伤放大因子公式进行了修正；波激振动程度随海况的变化明显，波激载荷对疲劳损伤的放大效果随遭遇频率和有义波高的减小而增大。 结论 以“主导海况”代替多典型海况，可以在较短时间内获取相对准确的疲劳损伤放大因子，这在船舶设计初期具有指导意义。 Abstract:Objectives This paper aims to study the fatigue damage problem of large ship prone to springing effect. Methods The test result in two generation 400 000 DWT very large ore carrier (VLOC) are compared based on ship model test method, and the relation of sea states and fatigue including hull girder springing are analyzed. According to the recursion method, a classical sea state is selected from a series of model test sea states. Results The results show that the fatigue damage magnification effect has a trend relationship with significant wave height and encounter period. The concept of "dominant sea state" is proposed based on the recurrence method, and the expression of fatigue damage magnification factor is improved. The springing effect varies significantly according to different sea states, and the fatigue damage magnification effect of springing increases very rapidly as significant wave height and encounter period decrease. Conclusions Replacing multiple model test loading conditions with dominant sea state could allow relatively accurate fatigue damage magnification factor to be ascertained rapidly. As such, this paper can provide references during the initial design period. -
Key words:
- ship structure /
- springing /
- fatigue damage /
- ship model test
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图 2 典型的垂向波浪弯矩时历曲线.
Figure 2. Time histories of typical VBM with/without springing effect
图 5 第1代 400 000 DWT VLOC 的Fvib比较图
Figure 5. Comparison of Fvib for the 1st generation 400 000 DWT VLOC caculated by three methods
表 1 两代400 000 DWT VLOC的海况
Table 1. Sea states of two generation 400 000 DWT VLOC
序号 第1代 第2代 Hs/m Tz/Hz Hs/m Tz/Hz 1 2.5 7.5 2.5 7 2 2.5 9.5 2.5 9 3 2.5 11.5 2.5 11 4 2.5 13.5 2.5 13 5 4.5 7.5 4.5 7 6 4.5 9.5 4.5 9 7 4.5 11.5 4.5 11 8 4.5 13.5 4.5 13 9 6.5 7.5 6.5 7 10 6.5 9.5 6.5 9 11 6.5 11.5 6.5 11 12 6.5 13.5 6.5 13 13 8.5 7.5 8.5 7 14 8.5 9.5 8.5 9 15 8.5 11.5 8.5 11 16 8.5 13.5 8.5 13 
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表 2 两代400 000 DWT VLOC的航速
Table 2. Speeds of two generation 400 000 DWT VLOC
序号 第1代的航速/kn 第2代的航速/kn 压载 满载 压载 满载 1 14.5 14.5 15.4 14 2 14.5 14.5 15.4 14 3 14 14 15.4 14 4 14 14 15.4 14 5 12 12 13 12 6 12 12 13 12 7 11 11 13 12 8 11 11 13 12 9 9 9 11 10 10 9 9 11 10 11 8 8 11 10 12 8 8 11 10 13 6 6 8 7.3 14 6 6 8 7.3 15 5 5 8 7.3 16 5 5 8 7.3
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表 3 两代400 000 DWT VLOC疲劳损伤放大因子
Table 3. Fvib of two generation 400 000 DWT VLOC
疲劳损伤放大因子Fvib 压载工况 满载工况 第1代 2.41 2.04 第2代 5.85 2.61
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表 4 第1代400 000 DWT VLOC压载工况下的Fvib
Table 4. Fvib of the 1st generation 400 000 DWT VLOC under ballast condition
Hs/m Fvib Tz=8.0 s Tz=9.0 s Tz=10.0 s Tz=11.0 s Tz=12.0 s Tz=13.0 s 2.5 12.0 5.1 2.9 2.2 1.7 1.3 3.5 9.4 4.5 2.8 2.0 1.5 1.4 4.5 9.2 4.5 2.8 1.9 1.5 1.5 5.5 5.4 2.9 2.2 1.8 1.5 1.4 6.5 3.7 2.4 2.0 1.7 1.5 1.4 7.5 2.7 2.0 1.7 1.5 1.4 1.3 8.5 2.3 1.8 1.6 1.4 1.3 1.3
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表 5 第2代400 000 DWT VLOC压载工况下的Fvib
Table 5. Fvib of the 2nd generation 400 000 DWT VLOC under ballast condition
Hs/m Fvib Tz=8.0 s Tz=9.0 s Tz=10.0 s Tz=11.0 s Tz=12.0 s Tz=13.0 s 2.5 46.8 21.4 7.8 2.2 2.0 1.6 3.5 27.3 12.5 7.0 3.7 2.8 2.0 4.5 25.8 11.8 6.9 3.9 2.9 2.0 5.5ter" valign="middle">5.8 3.6 3.1 2.5 6.5 16.9 8.9 5.5 3.5 3.1 2.7 7.5 7.5 5.0 3.5 2.6 2.3 2.0 8.5 3.7 3.1 2.5 2.0 1.9 1.7
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表 6 第1代 400 000 DWT VLOC四海况等效疲劳放大因子
Table 6. Fvib_eq4 of the 1st generation 400 000 DWT VLOC
Hs/m Fvib_eq4 Tz=8.0 s Tz=9.0 s Tz=10.0 s Tz=11.0 s Tz=12.0 s Tz=13.0 s 2.5 12.0 5.1 2.9 2.2 1.7 1.3 3.5 9.4 4.5 2.8 2.0 1.5 1.4 4.5 9.2 4.5 2.8 1.9 1.5 1.5 5.5 5.4 2.9 2.2 1.8 1.5 1.4 6.5 3.7 2.4 2.0 1.7 1.5 1.4 7.5 2.7 2.0 1.7 1.5 1.4 1.3 8.5 2.3 1.8 1.6 1.4 1.3 1.3
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表 7 计算的第1代 400 000 DWT VLOC的Fvib
Table 7. Calcuated Fvib of the 1st generation 400 000 DWT VLOC
工况 疲劳损伤放大因子Fvib 模型试验 修改公式 原始公式 压载 2.41 2.41 2.32 满载 2.04 2.03 1.38
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