﻿ 初始缺陷对加筋板结构极限强度的影响研究
 舰船科学技术  2017, Vol. 39 Issue (3): 29-35 PDF

Effect of initial imperfections on the ultimate strength of stiffened panels
SHI Xing-hua, BIAN Xuan-yi, QIAN Peng, WANG Peng-xiang
School of Naval Architecture and Ocean Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China
Abstract: The ultimate strength of stiffened panel with three initial imperfections under uniaxial compression loading by the nonlinear finite element software ANSYS. Three initial imperfections, namely, initial deformation, dent is assumed to formed by the ball with different radius and different speed impacting on the stiffened plate and residual stress. One stiffened panel is introduced, the effect of three imperfections on the ultimate strength of stiffened panels. It is indicated that initial imperfections reduce the ultimate strength of stiffened panel, the effect of superposition of imperfections to ultimate strength i greater than that of only one imperfection to ultimate strength. Ultimate strength of stiffened panel decreases with the increase the depth of dent. Compared to initial deformation and dent, the reduction of residual stress to ultimate strength is greatest.
Key words: initial imperfections     stiffened panels     ultimate strength     dent
0 引 言

1 初始缺陷 1.1 初始变形

 ${{{w}}_p} = \left( { - {w_p}} \right) \times \cos \frac{{m\pi x}}{a} \times \cos \frac{{n\pi y}}{b}\text{，}$ (1)

 ${{{w}}_{oh}} = \left( { - {w_{os}}} \right) \times \cos \frac{{m\pi x}}{a} \times \sin \frac{{n\pi z}}{{2h}}\text{，}$ (2)

 ${{{w}}_{oh}} = \left( { - {w_{oc}}} \right) \times \cos \frac{{n\pi x}}{a}\text{。}$ (3)

1.2 焊接残余应力

1.3 凹陷

Paik[8]经过研究和分析发现：在凹陷的幅值一定的情况下，凹陷形状对板格极限强度的影响很小。因此，本文加筋板上的所有凹陷全由球撞击而成。采用显式有限元程序 LS-DYNA 进行球与加筋板的碰撞过程的模拟，得出结构所有节点的位移改变量，选取加筋板结构的碰撞模型作为含凹陷结构极限强度的分析模型。

2 计算模型

 图 1 加筋板计算模型 Fig. 1 Calculation model of stiffened panel

3 含初始缺陷结构极限承载力分析 3.1 初始变形和凹陷的叠加

 图 2 含初始变形的加筋板变形和应力云图 Fig. 2 Deformation and the stress distribution of stiffened plate with initial deformation

 图 3 加筋板的变形和应力云图（半径为 0.2 m） Fig. 3 Deformation and the stress distribution of stiffened plate（Radius of 0.2 m）

 图 4 加筋板的变形和应力云图（半径为 0.25 m） Fig. 4 Deformation and the stress distribution of stiffened plate（Radius of 0.25 m）

 图 5 加筋板的变形和应力云图（半径为 0.3 m） Fig. 5 Deformation and the stress distribution of stiffened plate（Radius of 0.3 m）

 图 6 含初始缺陷加筋板的应力-应变曲线图 Fig. 6 The stress-strain curves of stiffened panels under initial imperfections

 图 7 不同凹陷深度的加筋板应力-应变曲线 Fig. 7 The stress-strain curves of stiffened panels under different dent depths

 图 8 加筋板的变形和应力云图（速度为 8 m/s） Fig. 8 Deformation and the stress distribution of stiffened plate（velocity of 8 m/s）

 图 9 加筋板的变形和应力云图（速度为 9 m/s） Fig. 9 Deformation and the stress distribution of stiffened plate（velocity of 9 m/s）

 图 10 加筋板的变形和应力云图（速度为 11 m/s） Fig. 10 Deformation and the stress distribution of stiffened plate（velocity of 11 m/s）

 图 11 含初始缺陷加筋板的应力-应变曲线图 Fig. 11 The stress-strain curves of stiffened panels under initial imperfections

 图 12 不同凹陷深度的加筋板应力-应变曲线 Fig. 12 The stress-strain curves of stiffened panels under different dent depths

3.2 三种初始缺陷的叠加

 图 14 含初始缺陷的加筋板应力-应变曲线图 Fig. 14 The stress-strain curves of stiffened panels with initial imperfections

4 结 语

1）在考虑初始变形和凹陷对加筋板结构极限强度影响时发现，初始变形对结构的承载力影响最小，而凹陷对结构的承载力影响相对较大，凹陷对结构的承载力随着凹陷深度的增大而减小；

2）在考虑 3 种初始缺陷的影响时发现，残余应力严重影响结构的承载力，6 种模式下的结构只要含有残余应力，其承载力明显小于不含残余应力的。而在建造 FPSO 过程中所用的钢材都会经过焊接，这必然会在结构中残留残余应力，因此在校核结构强度时，不能忽视残余应力的影响；

3）初始缺陷的叠加对结构承载力的影响明显大于单独存在的情况。因此结构在建造运输等过程中，应该尽量避免在同一结构上造成缺陷的叠加，最大限度地保持结构的完整性。

 [1] ﻿张婧, 江小龙, 石晓彦, 等. 具有初始缺陷的裂纹加筋板剩余极限强度分析[J]. 哈尔滨工程大学学报. 2016, 37(7): 1–9. [2] 张婧, 施兴华, 顾学康. 具有初始缺陷的船体加筋板结构在复杂受力状态下的极限强度研究[J]. 中国造船. 2013, 54(1): 60–70. [3] 任慧龙, 郎舒妍, 任晨辉, 等. 带有初始缺陷的船体结构极限强度研究[J]. 舰船科学技术, 2015, 37(12): 38–41. REN Hui-long, LANG Shu-yan, REN Chen-hui, et al. Ultimate strength of hull structure with initial defect[J]. Ship Science and Technology, 2015, 37(12): 38–41. [4] PAIK J K, LEE J M, LEE D H. Ultimate strength of dented steel plates under axial compressive loads[J]. International Journal of Mechanical Sciences. 2003, 45(3): 433–448. [5] SAAD-ELDEEN S, GARBATOV Y, GUEDES SOARES C. Ultimate strength analysis of highly damaged plates[J]. Marine Structures, 2016, 45: 63–85 [6] CUI W, MANSOUR A E. Effects of welding distortions and residual stresses on the ultimate strength of long rectangular plates under uniaxial compression[J]. Mar Struct 1998(11): 251–269. [7] 汤夕春. 残余应力对H型钢梁柱构件极限承载力影响研究[D]. 武汉: 武汉理工大学, 2006. [8] PAIK J K. Ultimate strength of dented steel plates under edge shear loads[J]. Thin-Walled Structures. 2005, 43: 1475–1492.