LNG围护系统结构失效模式的有限元模拟

Finite element simulation of structural failure modes of an LNG containment system

LNG运输船设计关键技术之一是液舱围护系统的结构安全设计。为了保证LNG液体的运输安全,需要特别关注围护系统的结构设计,其中对结构失效模式及其发生机理的研究具有很高参考价值。为了能够全面研究薄膜型液舱结构特性,采用基于有限元的数值模拟方法,针对在晃荡荷载下的结构响应,建立了一种简化的二维有限元模型。根据层式复合材料特点,分别选取对应的强度失效准则,分析结构的失效模式。数值分析结果显示,首层聚氨酯泡沫层在晃荡荷载作用下最先发生压溃破坏,在MARKⅢ型液舱设计中应该被重点关注;其他的结构失效模式依次为:次层聚氨酯泡沫层压溃失效、层合板剪切失效以及树脂绳压溃失效。采用数值模拟进行围护系统的截面失效模式分析,能够快速高效地指导LNG液舱结构设计,是在液舱设计领域新的应用尝试。

A critical technology in the design of LNG carriers is structural safety of a containment system. The structural design of the LNG containment system plays an important role in the safety of LNG cargo during the transportation. The failure modes and re lated mechanism has a significant reference value for the structural design of an LNG containment system. The critical failure modes of the MARK III containment system induced by the sloshing impact were studied in this paper. A simplified 2D numerical model based on the finite element method was established to simulate the stress response. According to the characteristics of different corn ponents, the structural failure modes of different components of layered composites were obtained according to their material charac- teristics and corresponding strength failure criteria. The numerical result shows that crushing of primary foam is the primary failure mode under the sloshing impact, which should be carefully considered in the structural design of MARK Ill tanks. Other failure modes are crushing of secondary foam, shear failures of plywood sheets, and crushing of resin ropes. The structural design of LNG tanks can be improved with numerical simulation of failure modes analysis, which is a new application attempt in the containment system design.