考虑应变率相关性对材料性能影响的动载荷下集装箱船船体梁极限强度

A study on the hull girder under dynamic loading considering the effects of strain-rate dependency on material properties

    摘要
  • 摘要:
      目的  近年来，诸如冲荡之类的动载荷对集装箱船结构强度的影响已成为重要课题之一，因此，有必要研究动载荷对船体梁极限强度的影响，并了解动载荷作用下的破坏特性。
      方法  以集装箱船为研究对象，建立3 100 TEU集装箱船舯剖面半宽度模型，运用LS-DYNA商用有限元软件，分析船体梁在冲荡等动载荷作用下的极限强度。考虑应变率相关性对材料性能的影响，采用常规Cowper-Symonds公式及其不同的改进材料模型，对结构的极限载荷进行动态分析。
      结果  结果表明：对于船体梁纵向弯曲破坏，在施加冲荡的动载荷时，动态极限载荷比准静态极限强度高出约7%~9%；即使施加的动载荷时长处于正常的波浪感应载荷水平，动态极限载荷也比准静态极限强度超出约4%~5%。
      结论  在评估动态船体梁的极限强度时，可以使用常规CS公式。然而，在估算残余变形和残余强度时可能需要使用适当的材料模型。

     

    Abstract:
      Objectives  The effects of such dynamic loading as whipping on the structural strength of a container ship has become an important subject in recent years. Given that, it is necessary to study the impact of such dynamic loading on the hull girder ultimate strength of the midship structure, in particular, to understand that of the strain-rate dependency of the material properties on its collapse behaviors.
      Methods  This paper takes the container ship as research object, establishes a half breadth model of midship section of a 3 100 TEU container ship. Commercial finite element analysis (FEA)software LS-DYNA is used to investigate the ultimate strength of hull girder subject to dynamic loads such as whipping. Considering the effect of the strain-rate dependency of the yield stress of the material, conventional Cowper-Symonds(CS) formula and improved CS models are employed to have dynamic analysis on the ultimate strength.
      Results  The results show that, the dynamic collapse load when such dynamic load as whipping is applied is about 7%-9% greater than quasi-static ultimate strength. Even when the time duration of applied dynamic loading is at the normal wave-induced loading level, the dynamic collapse load becomes about 4%-5% greater than quasi-static ultimate strength.
      Conclusions  when evaluating dynamic hull girder ultimate strength, there is no problem with using the conventional CS formula, however, to estimate residual deformation and residual strength using FEA, it might be necessary to use a proper material model.

     

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