﻿ 砰击弯矩下船体梁动态极限强度研究
 舰船科学技术  2022, Vol. 44 Issue (8): 24-29    DOI: 10.3404/j.issn.1672-7649.2022.08.005 PDF

Research on dynamic ultimate strength of hull girder under slamming bending moment
XIA Jin-song, LI Fei, ZHAO Nan, JIANG Cai-xia, LIU Jun-jie
China Ship Scientific Research Center, Wuxi 214082, China
Abstract: The dynamic response characteristics of hull girder under slamming load need to consider the dynamic constitutive relationship, inertia effect and stress wave effect of the hull steel material, which is obviously different from the static failure characteristics. At present, a large number of research results have been obtained for the static ultimate strength of hull girder. The dynamic ultimate strength is an important index for evaluating the safety performance of hull girder under slamming load, and few scholars have conducted research on this. Therefore, it is particularly important to study the dynamic ultimate strength of hull girder under slamming load. In this paper, the hull girder bending moment-rotation curve, static ultimate strength (Mu) and static limit rotation angle (Ry0) are obtained under static load based on the dynamic display method. The static limit angle of rotation is used as the basis for evaluating the dynamic ultimate strength of hull girder under slamming dynamic load. The effects of slamming load duration, slamming impulse and slamming load amplitude on the dynamic response characteristics of hull girder are discussed.
Key words: slamming load     hull girder     ultimate strength     ultimate turning angle
0 引　言

1 有限元模型 1.1 材料模型

 ${\sigma _{{{dy}}}} = {\sigma _y}\left( {1 + {{\left( {\frac{{\dot \varepsilon }}{D}} \right)}^{1/q}}} \right)。$

1.2 舱段模型

 图 1 舱段结构图 Fig. 1 Cabin structure diagram
1.3 边界条件及载荷施加

2 船体梁动态破坏特性分析 2.1 静态极限强度分析

 图 2 船体梁静态弯矩-转角曲线 Fig. 2 Hull girder static bending moment-rotation curve

 图 3 01甲板应力云图和塑性应变云图 Fig. 3 01 Deck stress cloud chart and plastic strain cloud chart

 图 4 1甲板应力云图和塑性应变云图 Fig. 4 1 Deck stress cloud chart and plastic strain cloud chart
2.2 砰击载荷形状

 图 5 砰击弯矩历程曲线 Fig. 5 Slamming moment history curve
 $f(t) = \sin \left(\frac{{{\text{π}} t}}{{{t_p}}}\right)，$
 ${M_k}\left( t \right) = {M_{\max }}f(t) = {M_{\max }}\sin \left(\frac{{{\text{π}} t}}{{{t_p}}}\right) 。$
2.3 计算工况

3 计算结果和讨论 3.1 船体梁砰击响应

 图 6 01甲板应力云图和塑性应变云图 Fig. 6 01 Deck stress cloud chart and plastic strain cloud chart

 图 7 1甲板应力云图和塑性应变云图 Fig. 7 1 Deck stress cloud chart and plastic strain cloud chart

L03，L04和L05工况下船体梁动态响应曲线如图8所示。可知：船体梁端面转角在砰击载荷峰值之后达到最大值，在时间维度有滞后性；当砰击弯矩衰减为0时，船体梁端面有残余转角产生（小于静态极限转角Ry0）；L03工况下船体梁的响应峰值大于L04和L05工况下的响应峰值，L04和L05工况作用下的船体梁响应峰值与静态载荷作用下的响应峰值(Ry0)非常接近，这是因为L03工况下的砰击时间最为接近船体梁的固有振动周期(T=8.7 ms)，可能激发了共振，导致响应峰值结果增大；根据Cui[10]的结论，可知L04和L05工况作用下船体梁结构响应过程可被看成准静态响应。

 图 8 无量纲端面转角时间历程曲线 Fig. 8 Time history curve of dimensionless end face angle

3.2 砰击载荷持续时间的影响分析

 图 9 无量纲残余变形-砰击持续时间曲线 Fig. 9 Dimensionless residual deformation-slamming duration curve
3.3 砰击冲量的影响分析

 图 10 砰击冲量一定时船体梁端面无量纲残余变形随砰击时间的变化曲线 Fig. 10 Dimensionless residual deformation of hull girder-slamming duration curve when the slamming impulse remains unchanged
3.4 砰击载荷幅值的影响分析

 图 11 无量纲残余变形-无量纲砰击弯矩曲线 Fig. 11 Dimensionless residual deformation-dimensionless slamming bending moment curve

 图 12 5种工况L03和L07～L10下模型塑性应变云图 Fig. 12 Plastic strain cloud diagram of the model under L03 and L07～L10 conditions
4 结　语

1）砰击弯矩下船体梁动态失效模式与静态失效模式不同，动态载荷作用下的结构响应(Ry0)峰值更大；

2）砰击弯矩一定时，砰击持续时间越长，其对应的砰击冲量越大，但相应的无量纲残余变形却越来越小，即船体梁残余变形对砰击载荷持续时间非常敏感；

3）砰击冲量一定时，随着砰击持续时间的减小，船体梁端面动态响应峰值和残余变形增大；

4）砰击时间一定时，船体梁端面动态响应峰值和残余变形随砰击弯矩幅值的增大而增大。

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