加筋板的大挠度塑性动力响应研究

对加筋板的大挠度塑性动力响应进行了理论研究,应用单轴对称截面的线性化轴力-弯矩交互作用曲线和相关联的塑性流动法则推出了梁达到塑性弦状态所应满足的挠度条件.此外,详细地分析了梁在不同载荷情况下可能的运动模式.最后应用本文理论和有限元软件ANSYS、ABAQUS/Explicit对四边固支单向加筋板结构进行了求解.     

Dynamic plastic response of clamped stiffened plates with large deflection

Study on the dynamic response, and especially the nonlinear dynamic response of stiffened plates is complicated by their discontinuity and inhomogeneity. The finite element method （FEM） and the finite strip method are usually adopted in their analysis. Although many useful conclusions have been obtained, the computational cost is enormous. Based on some assumptions, the dynamic plastic response of clamped stiffened plates with large deflections was theoretically investigated herein by a singly symmetric beam model. Firstly, the deflection conditions that a plastic string must satisfy were obtained by the linearized moment-axial force interaction curve for singly symmetric cross sections and the associated plastic flow rule. Secondly, the possible motion mechanisms of the beam under different load intensity were analysed in detail. For structures with plastic deformations, a simplified method was then given that the arbitrary impact load can be replaced equivalently by a rectangular pulse. Finally, to confirm the validity of the proposed method, the dynamic plastic response of a one-way stiffened plate with four fully clamped edges was calculated. The theoretical results were in good agreement with those of FEM. It indicates that the present calculation model is easy and feasible, and the equivalent substitution of load almost has no influence on the final deflection.     

Ultimate collapse tests of stiffened-plate ship structural units

An increasingly popular approximate method for assessing ship hull girder ultimate strength is to combine the individual elasto-plastic load-carrying characteristics of each single stiffened-plate unit comprising the ship hull cross section. In order to evaluate methods (numerical and experimental) for developing the load-carrying characteristics (load–shortening curves), a full-scale testing system was designed and constructed to provide data for stiffened steel plate units under combined axial and lateral loads. The system included an assembly of discrete plate edge restraints that were developed to represent symmetric boundary conditions within a grillage system. Twelve full-scale panels including ‘as-built’, ‘deformed’ and ‘damaged’ specimens were tested in this set-up.

The specimens failed by combined plate and flexural buckling, stiffener tripping or local collapse, depending on the magnitude of lateral loads and local damage. Load-shortening curves associated with different failure modes were found to be distinctly different and it was found that a small lateral load could change the failure mode from flexural buckling to tripping. Current design criteria should directly consider effects of the lateral loads on the failure modes and the collapse loads of stiffened plates.     

固支方形板在水下爆炸冲击波载荷作用下动态响应数值仿真研究

舰船在实际海战中的抗打击能力是舰船生命力的重要指标.板格是舰船结构的基本组成单元,为了研究板格在爆炸载荷作用下的承载能力,采用数值方法研究了正方形板在水下爆炸冲击波载荷作用下的动态响应,分析了板的变形模式,研究了板厚和爆炸冲击因子对板的最大变形绕度的影响,推导出简单适用的经验公式.     

导弹分段刚体模型和弹性体模型的动响应区别

针对目前一种新提出来的潜射导弹分段刚体模型的试验方案,通过求解在同一载荷作用下分段刚体模型与实际弹性体模型的动响应,来定量分析该模型试验所测得极大载荷值和实际情况下极大载荷的偏差.     

非均布力激励Euler-Bernoulli梁振动响应的WPA分析

基于弯曲波叠加原理和极限积分思想，推导了非均匀分布力激励下均匀有限长梁振动响应的WPA法解析表达式，并运用WPA法计算了Euler-Bernoulli梁在梯形（三角形）和正弦两种典型非均匀分布力作用下的动态响应，得到其精确数值解，为浮筏隔振系统等的分析奠定了基础。     

十字交叉梁模型的塑性动力响应计算方法

船体板架在水下爆炸载荷作用下的塑性动力响应计算是舰船抗爆性能研究中的一项重要工作,鉴于有限元法对其求解的计算效率无法保证,同时解析法对其求解有技术上的困难等研究现状,提出了一种将船体板架结构简化成刚塑性十字交叉梁,并通过动量定理和动量矩定理由运动方程推导出十字交叉梁结构中横向和纵向构件二者在关联处有力的相互作用时的变形挠度的计算方法。利用此方法计算所得的结果,与实船舱段的有限元模型结果,以及实船舱段的水下爆炸试验的数据进行对比后,吻合较好。结果表明,力学模型选取是合理的,用于水下非接触爆炸的舰船板架挠度变形计算方法不仅保证了计算效率,也保证了计算精度,具有工程实用性。     

基于频响函数相关系数灵敏度的浮筏舱段有限元模型修正

在建立复杂结构的有限元模型时,对实际结构的简化直接影响到计算结果的准确性,对有限元模型进行修正十分必要。引入试验和初始有限元模型得到的频响函数的相关准则,利用频响函数相关系数灵敏度分析技术,用于对浮筏舱段结构有限元模型进行修正,修正后计算和试验的频响函数基本一致,结果表明：该方法可用于对复杂结构有限元模型的修正。     

焊接梁动力学建模及动态特性分析

以工程中常见的焊接梁结构为对象,把焊接部位模化成等截面弹性梁结构,建立梁-焊接件-梁系统动力学模型。利用传递矩阵法,推导了子结构的传递矩阵,得到了焊接梁系统的动态响应表达式,详细讨论了焊接梁结构尺寸和参数对系统动态性能的影响。搭建了典型焊接梁实物模型,测试了焊接梁的加速度频响,结果表明,所建立的焊接梁力学模型正确。     

随机导管架平台结构动力可靠性及灵敏度分析

基于Kriging模型和一次二阶矩方法对具有随机参数的导管架平台结构动力可靠度进行了分析.首先根据首次超越破坏准则建立了随机结构动力可靠度的隐式功能函数表达形式.然后通过有限元分析得到用于隐式功能函数近似的Kriging模型,进而求得可靠度指标.最后根据可靠度对随机参数均值和标准差的灵敏度公式,分析了导管架平台可靠度对各随机变量的敏感性,并得出了一些有益于工程设计、参数优化和精度控制的结论.     

深海工程船锚泊仿真系统

为实现工程船定位和控位快速模拟仿真,以45000载重吨海洋工程船为例,采用均匀设计试验方法,确定深海船舶工作的不同工况组合,基于Ansys-Aqwa软件对该船的深海锚泊动态响应进行仿真分析。对仿真结果进行回归分析处理,得到船舶位移和锚索张力与锚索长度和环境载荷(风、浪、流)之间的数学响应模型。对位移数学响应模型进行求反函数处理,获取船舶控位调整锚索长度的方法,为深海锚泊软件仿真系统提供模型支撑。     

Experimental study on the nonlinear pressure acting on a high-speed vessel in regular waves

It is well known that the hydrodynamic responses of a high-speed vessel traveling in regular head waves of even moderate wave height can show significant nonlinear behavior, and so linear statistical techniques become insufficient for predicting the statistics of responses in irregular waves. On the other hand, it has been shown that an approximate third-order Volterra model is applicable to handling the statistics of some nonlinear seakeeping problems, such as motions and vertical hull girder loads. In the present study, the focus is on the nonlinear behavior of the pressure responses of the hull surface, especially on the pressures acting on alternately wet and dry areas near the waterline and on the bow zone with high deadrise angles that may be subject to slight impact and water pile-up effects. To clarify the validity of applying Volterra modeling to this problem, a series of experiments in regular and irregular head waves were carried out, and approximate third-order and fifth-order Volterra models with the proposed algorithm for finding frequency response functions (FRFs) were applied as a means of validation. In the present article, the first part of the validation was performed using experimental data in regular waves. It was confirmed that the third-order Volterra model has adequate accuracy to simulate deterministically the variation of pressure responses in regular waves of different wave steepness up to a wave amplitude to wavelength ratio of 0.01 even for the highly nonlinear pressures acting on the above-mentioned areas of the hull surface.     

浅水单点系泊FPSO软刚臂参数敏感性分析

软刚臂单点系泊FPSO是浅水油田广泛采用的油气开采设备。为研究单点系泊系统的受力性能,针对一艘作业于浅水油田的16万吨级软刚臂单点系泊FPSO,在线性三维势流理论的基础上,基于多体动力学方法建立FPSO-系泊腿-软刚臂的耦合模型,在时域内计算软刚臂单点系泊系统（SYMS）的动力响应特性;并进行软刚臂单点系泊系统参数敏感性分析,研究软刚臂系泊系统的系泊点高度、系泊刚架高度、软刚臂长度、系泊腿长度、压载舱重量等设计参数的变化对系统动力响应性能的影响。结果表明：单点载荷和系泊腿轴向载荷随着系泊点高度、系泊刚架高度和压载重量的增加先减小后增大,而随着软刚臂长度、系泊腿长度的增加则是先增大后减小;且单点载荷对软刚臂长度和压载重量这2个参数的变化最为敏感,而系泊腿轴向载荷则对系泊刚架高度、软刚臂长度这2个参数的变化最为敏感。     

Experimental study on the nonlinear pressure acting on a high-speed vessel in irregular waves

The present study focuses on the nonlinear behavior of pressure on the hull surface of a high-speed vessel in irregular waves, particularly the pressure responses of alternately wet and dry areas near the waterline and on the bow zone. The vessel has high deadrise angles that may be subject to slight impact and water pile-up effects. A series of experiments in regular and irregular head waves were conducted, and the validity of applying Volterra modeling was investigated. In a previous article using experimental data in regular waves, it was confirmed that the approximate third-order Volterra model adequately simulated the variation of pressure responses in regular waves of different steepness up to a wave amplitude with a wavelength ratio of 0.01, even for the highly nonlinear pressures acting on the abovementioned areas of the hull surface. In this article, further validation for the second part of the study was obtained using experimental data in irregular waves. The frequency response functions obtained from the previous study’s experimental data in regular waves were applied to the third-order Volterra model by combining the input of irregular waves to simulate the responses in irregular waves of sea state five. Then, the spectra and statistics were analyzed. For the motions, accelerations, and pressure responses in irregular waves (as well as for the simulated time histories) variance spectra and statistics such as cumulative distributions of peak values and probability density functions were compared with the experimental results. It was confirmed that even for highly nonlinear and non-Gaussian pressures on the abovementioned areas of the hull surface, the approximate third-order Volterra model simulates the pressure responses in irregular head waves up to a sea state of five with adequate accuracy on deterministic and statistical bases.     

极地船舶冰带区域关键节点研究

随着极地探索的不断发展,针对冰区航线的船体结构设计不再局限于传统的经验公式方法,人们更加关注作用于结构上的实际冰载荷及结构响应,研究冰载荷作用下的结构响应计算成为极地船舶结构设计中的关键部分。

首先,通过有限元方法对某极地航行船舶遭遇的碎冰、浮冰、层冰等冰载荷工况进行数值仿真,考虑材料应变率影响,计算冰载荷作用下的结构动态响应;然后,以结构响应等效为基准,进行动态响应的静态转换,并提出动静转化系数的概念;最后,给出不同冰载荷工况下动静转化系数的取值范围。

结果表明,船首结构在不同工况下动载荷响应的静载荷等效转换计算的转换系数为1.0～1.4之间。

船首结构冰致动力响应的准静态等效方法是合理可行的。

     

导弹战斗部冲击下舷侧梁的动力响应及失效模式分析

根据理想刚-塑性材料模型假设,同时考虑梁的剪切、弯曲及拉伸,分析了均匀矩形截面简支梁中部在中低速、大尺寸、大质量、平头弹体正冲击下的动力响应,得到了梁的初始塑性变形模式及梁的塑性变形过程,并根据有效塑性应变失效准则,分析了简支梁的失效模式,得到了冲击过程中梁的临界失效挠度及吸能量,讨论了梁截面的形状及跨长对梁变形吸能能力的影响.     

基于Timoshenko梁理论的三体船波激响应

以Timoshenko梁理论和薄壁杆件理论为基础,考虑梁模型受到静止的波浪载荷预应力的作用,使连接桥产生垂向剪切变形以及垂向弯矩和扭转所产生的转角。通过梁模型简化小水线面三体船,建立三梁模型,从而对其波激响应进行数值模拟分析。结果显示,三梁模型在分析小水线面波激响应方面有较好的实用价值,给相关分析提供了一个实用的方法。     

远场非接触爆炸作用下舱段模型动态响应的数值模拟

利用非线性有限元软件ABAQUS计算了舱段模型在非接触水下爆炸作用下的动态响应过程,给出了各部位的加速度时间历程,利用模型爆炸试验来检验计算的正确性,在数值计算和工程试验的基础上讨论了舱段模型在远场爆炸下的响应,此研究对舰船结构抗冲击仿真评估具有一定的参考价值.