冰激结构频率锁定振动的发生机理及简单分析方法

屈衍; 黄子威; 邹科; 尹昊阳; 张大勇

doi:10.6052/0459-1879-20-382

冰激结构频率锁定振动的发生机理及简单分析方法

doi: 10.6052/0459-1879-20-382

屈衍^*,2), ,,
黄子威^*,
邹科^*,
尹昊阳^*,
张大勇^†

^*南方科技大学前沿与交叉科学研究院,广东深圳 518055
^††大连理工大学工业装备结构分析国家重点实验室,辽宁大连 116024

基金项目: 1) 国家自然科学基金(41976195);国家自然科学基金(51679033);国家研发计划(2016YFC0303400);工业装备结构分析国家重点实验室开放课题(GZ19120)

详细信息

作者简介:
2) 屈衍,副研究员,主要研究方向：极地海洋工程. E-mail: quy3@sustech.edu.cn

通讯作者:
屈衍

中图分类号: P751,P731.15
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- 被引次数: 0
出版历程
- 收稿日期: 2020-11-19
- 刊出日期: 2021-03-10

MECHANISM AND SIMPLE ANALYSIS METHOD OF ICE INDUCED FREQUENCY LOCK-IN VIBRATION OF OFFSHORE STRUCTURES

Qu Yan^{*,2)
, ,},
Huang Ziwei^*,
Zou Ke^*,
Yin Haoyang^*,
Zhang Dayong^†

^*Academy for Advanced Interdisciplinary Studies,Southern University of Science and Technology,Shenzhen 518055,Guangdong,China
^††State Key Laboratory of Structure Analysis for Industrial Equipment,Dalian University of Technology, Dalian 116024,Liaoning,China

摘要

摘要: 冰激结构频率锁定振动是冰区海洋工程结构的危险工况.对频率锁定振动过程的传统机理解释没有体现这一过程的全部物理特征,导致现有的分析方法无法准确分析这一问题.本文基于对现场测量结果的分析,提出了一种海冰韧性损伤-破碎过程与结构振动耦合导致频率锁定振动的机理.该机理认为,海冰在直立结构频率锁定振动过程中发生韧性损伤-破碎行为,海冰的韧性损伤-破碎与结构运动相位耦合,导致了频率锁定振动. 海冰对结构作用产生的载荷为锯齿形,作用过程可以分为加载和卸载两个阶段,其中加载阶段时间长度约为卸载阶段3倍以上.在加载阶段,结构从平衡位置先与海冰运动方向相反振动到反向最大振幅位置后回摆,然后与海冰同向运动到正向最大振幅位置,这段过程中海冰与结构接触部位内部产生裂纹并扩展但未发生主要的破碎,在此阶段海冰发生韧性损伤;在卸载阶段,结构从最大振幅位置向平衡位置回摆,结构与海冰运动方向相反,这一过程中应变速率的突然增大导致裂纹加速扩展并失稳开裂,此时带有韧性损伤的海冰发生破碎.基于这一新的机理解释,本文提出了一种冰激结构频率锁定振动幅值的简单分析方法.该方法认为海冰破碎长度是频率锁定振动的关键参数. 理想状态下,海冰破碎长度约为结构水线处振动幅值的2.2倍.当冰速接近海冰破碎长度与结构自振周期的比值时,结构会发生频率锁定振动.该方法对评估海洋工程结构频率锁定振动的发生概率及疲劳损伤具有指导意义.
- 冰激振动 /
- 频率锁定 /
- 韧性损伤-破碎 /
- 海冰破碎长度
Abstract: Ice induced frequency lock-in vibration of offshore structures has been recognized as a serious load condition in ice regions. The traditional mechanism cannot fully explain all the physical phenomena in the frequency lock-in vibration, nor can a reasonable analysis method be obtained. Based on the analysis of full scale measurement data, this paper proposes a new mechanism of frequency lock-in vibration caused by the coupling of sea ice ductile damage-collapse failure and structural vibration. It is believed that the ductile damage-collapse failure of sea ice occurs during the frequency lock-in vibration of vertical structures, which is coupled with the phase of structural motion, resulting in frequency lock-in vibration. Saw-teeth-shape ice load is caused by the action between sea ice and the structure. The action process can be divided into loading and unloading stages, the loading stage takes about 3 times the time of the unloading stage. In the loading stage, the structure moves against ice from equilibrium position to its maximum negative amplitude and then moves back together with ice at the same direction to its maximum positive amplitude. Cracks are formed in the contact part of the sea ice and the structure, but not collapse. The sea ice undergoes ductile damage at this stage. In the unloading stage, the structure moves in the opposite direction to the sea ice, swinging back from the maximum amplitude to its equilibrium position. The sudden increase of strain rate leads to the accelerated propagation and instable fracture of cracks. The sea ice with ductile damage collapses at this stage. Based on the new mechanism explanation, this paper presents a simple analysis method of ice induced frequency lock-in vibration of offshore structures. It is considered that the sea ice break length is the key parameter of frequency lock-in vibration. In the ideal situation, the sea ice break length is about 2.2 times of the vibration amplitude at the waterline of the structure. When the ice velocity is close to the ratio of sea ice break length to the natural vibration period of the structure, frequency lock-in vibration will occur. This method has guiding significance for evaluating the occurrence probability of frequency lock-in vibration and fatigue damage of offshore structures.
- ice induced vibration /
- frequency lock-in /
- ductile damage-collapse failure /
- sea ice break length

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