【作者】 余晓菲；

【导师】 刘土光；

【作者基本信息】 华中科技大学 ， 船舶与海洋结构物设计制造， 2007， 博士

【摘要】 本文基于离散加筋模型,以矩形截面加强筋为例,将流体理想化为不可压缩理想势流,合理的简化水下爆炸所产生的冲击波载荷,考虑流体动压力的影响,建立了加筋圆柱壳结构的理论分析模型,并且寻求有效的分析计算方法,初步探讨了结构受水下爆炸冲击载荷作用下的动力响应及动力屈曲问题,为提高水下浸潜结构的抗冲击能力提供了一些的有意义的结论。本文的工作主要有以下几个方面:首先全面回顾总结了加筋板壳结构的自由振动,在冲击载荷作用下的动力响应和动力屈曲,重点对加筋圆柱壳受水下爆炸冲击载荷作用下的动力特性展开了评述。运用商业有限元软件MSC.DYTRAN,模拟了球形TNT药包在水下爆炸的过程,着重用两种耦合方法(General coupling and ALE)研究了加筋圆柱壳在水下球形TNT药包爆炸载荷作用下的振动和动响应特性,并将结果与有关参考文献中的实验结果进行了比较,两者基本吻合。接着,将环向加筋圆柱壳离散成由圆柱壳和加筋肋骨组成,并且两者在接触处刚性连接的壳体-肋骨系统,计及壳体剪切变形、转动惯性以及加筋肋骨的拉伸,弯曲和剪切变形的影响,采用Hamilton变分原理导出了系统运动方程。将位移展开为Fourier级数形式,由Galerkin方法得到了以位移傅氏系数形式表示的动力屈曲控制方程,运用四阶龙格-库塔法求解,计算了加筋圆柱壳在水下爆炸冲击载荷作用下的动力响应。着重讨论了流体动压力、静水压力、加筋肋骨几何参数、壳体厚度以及Fourier级数项数对计算结果的影响,验证了一些常用的结论。并且还讨论了加筋圆柱壳在水下的自由振动问题。在上述分析的基础上,计及大变形及初始缺陷的影响,研究了加筋圆柱壳在水下爆炸载荷作用下的非线性响应,总结出了一些有用的结论。接着分析了环向加筋圆柱壳在水下爆炸载荷作用下的弹塑性动力响应问题。弹塑性本构关系由Mises屈服条件和各向同性硬化的增量理论给出。借助增量数值(在时域采用四阶Runge-Kutta方法)方法来分析加筋圆柱壳的弹塑性行为。着重分析了环向加筋肋骨,均匀径向外压和材料应变率敏感性等因素对结构弹塑性动响应的影响。然后研究了加筋圆柱壳在水下爆炸冲击和轴向流-固冲击联合载荷作用下的非线性动力屈曲问题,用B-R准则来确定结构临界屈曲载荷,比较了结构分别在轴向流-固冲击载荷,水下爆炸冲击载荷单独作用和两载荷联合作用下的屈曲模态、临界载荷等,着重探讨了两个方向临界载荷之间的关系,环向加筋肋骨对加筋圆柱壳结构动力屈曲性态和抗轴向冲击屈曲能力的影响,得出了一些有意义的结论。并且还用B-R准则和Southwell两种方法来计算了加筋圆柱壳在水下爆炸径向冲击载荷作用下的弹塑性动力屈曲载荷。分析了结构几何参数,材料硬化参数等对加筋圆柱壳结构临界动力屈曲载荷的影响。更多还原

【Abstract】 On the basis of discrete stiffened model, taking the stiffener section as rectangular, assuming the flow field to be incompressible,predigesting the underwater explosive wave loading reasonably, taking the hydrodynamic impulsive loading into account, the analytical model of the stiffened cylindrical shells is constructed. By way of effective analysis method, the dynamic response and dynamic buckling of stiffened cylindrical shells subjected to underwater explosive loading induced by spherical charges are studied numerically and theoretically in this paper. The aim is to provide some meaningful conclusions for enhancing the strength of the underwater structures. The major work in this paper is as follows:The advances in the research of free vibration and dynamic response and dynamic buckling under impact loading of stiffened plates and shells are reviewed comprehensively at first. The dynamic characteristics of stiffened cylindrical shells subjected to underwater explosive loading are mainly commented.First the process of TNT charge exploding underwater is simulated with the code MSC.DYTRAN, and the dynamic response of the stiffened cylindrical shells subjected to the underwater explosive loading are computed emphatically by the two coupling methods (General coupling and ALE). The results are proved to be correct after comparing with some correlative literatures.Then discrete the stiffened cylindrical shell into shell-beam system by the rigid joint, the equations of structure motion subjected to underwater explosive loading are derived from Hamilton variational principle, considering the shear deformation, rotation interia of the shell and shear deformation, bending deformation and tension deformation of the stiffeners. The partial defferential equations are transformed to ordinary differential equations by Galerkin method and solved numerically by fourth-order Runge-Kutta method. The effects of the hydrodynamic impulsive loading, the static water pressure, the geometrical parameters of the stiffeners, the thickness of the shell,ηj =B j/Hj ratio and the terms of Fourier series on the dynamic response are discussed. Some common experiences are validated. On the basis of aforementioned analysis ,the nonlinear dynamic response of the stiffened cylindrical shell subjected to the underwater explosive loading are investigated, considering the effects of the initial geometric imperfections and the large deformation. Some appreciate conclusions are summarized. The elastic-plastic dynamic response of the stiffened cylindrical shells subjected to underwater explosive loading are studied through increment numerical method. The constitutive relation accord with Mises yield criteria and isotropic hardening increment theory. The effects of stiffeners, the uniform circumferential external pressure and the strain-rate sensitivity of materials on the elastic-plastic dynamic response are discussed.Next the nonlinear dynamic buckling of the stiffened cylindrical shells subjected to combined radial underwater explosive loading and axial fluid-structure impact loading are analyzed. The criterion proposed by Budiansky and Roth is applied to obtain the critical loading. The buckling modes and the critical loadings of the structure subjected to the axial fluid-structure impact loading and the radial underwater explosive loading are studied respectively. Then the relation between the critical loadings on the two directions are emphasized. The effects of the circular stiffeners on the bearing ability against axial impact , the buckling modes and the critical loadings are discussed. On the other hand the elastic-plastic dynamic buckling subjected to the underwater explosive loading are also studied. The B-R criterion and Southwell method are used. The effects of the geometrical parameters, the hardening parameters on the structure critical loadings are examined.更多还原