Buckling Properties of Water-Drop-Shaped Pressure Hulls with Various Shape Indices Under Hydrostatic External Pressure

The water-drop-shaped pressure hull has a good streamline,which has good application prospect in the underwater observatory.Therefore,this study conducted analytical,experimental and numerical investigation of the buckling properties of water-drop-shaped pressure hulls under hydrostatic pressure.A water-drop experiment was conducted to design water-drop-shaped pressure hulls with various shape indices.The critical loads for the water-drop-shaped pressure hulls were resolved by using Mushtari’s formula.Several numerical simulations including linear buckling analysis and nonlinear buckling analysis including eigenmode imperfections were performed.The results indicated that the critical loads resolved by Mushtari's formula were in good agreement with the linear buckling loads from the numerical simulations.This formula can be extended to estimate the buckling capacity of water-drop-shaped pressure hulls.In addition,three groups of pressure hulls were fabricated by using stereolithography,a rapid prototyping technique.Subsequently,three groups of the pressure hulls were subjected to ultrasonic measurements,optical scanning,hydrostatic testing and numerical analysis.The experimental results were consistent with the numerical results.The results indicate that the sharp end of the water-drop-shaped pressure hulls exhibited instability compared with the blunt end.This paper provides a new solution to the limitations of experimental studies on the water-drop-shaped pressure hulls as well as a new configuration and evaluation method for underwater observatories.

Buckling of Cassini Oval Pressure Hulls Subjected to External Pressure

The paper focuses on Cassini oval pressure hulls under uniform external pressure. The Cassini oval pressure hull is proposed based on the shape index of Cassini oval. The buckling of a series of Cassini oval pressure hulls with the shape index of 0.09–0.30 and one spherical pressure hull with the diameter of 2 m is devoted. Such hulls are numerically studied in the case of constant volume, material properties, and wall thickness. The results show that Cassini oval pressure hulls with the shape index of 0.10–0.11 can resist about 4% more external pressure than the spherical one. This deviates from the classical mechanics conclusion that spherical shell is the optimal shape for underwater pressure resistant structures.

Multi-objective design optimization of composite submerged cylindrical pressure hull for minimum buoyancy and maximum buckling load capacity

This paper presents the design optimization of composite submersible cylindrical pressure hull subjected to 3 MPa hydrostatic pressure.The design optimization study is conducted for cross-ply layups[0_(s)/90_(t)/0_(u)],[0_(s)/90_(t)/0_(u)]s,[0_(s)/90_(t)]s and[90_(s)/0_(t)]s considering three uni-directional composites,i.e.Carbon/Epoxy,Glass/Epoxy,and Boron/Epoxy.The optimization study is performed by coupling a Multi-Objective Genetic Algorithm(MOGA)and Analytical Analysis.Minimizing the buoyancy factor and maximizing the buckling load factor are considered as the objectives of the optimization study.The objectives of the optimization are achieved under constraints on the Tsai-Wu,Tsai-Hill and Maximum Stress composite failure criteria and on buckling load factor.To verify the optimization approach,optimization of one particular layup configuration is also conducted in ANSYS with the same objectives and constraints.

Multi‑Crack Interaction and Influence on the Spherical Pressure Hull for a Deep‑Sea Manned Submersible

This study investigates the interaction and influence of surface cracks on the spherical pressure hull of a deep-sea manned submersible.The finite element model of the spherical hull is established,and a semi-elliptical surface crack is inserted in the welding toe of the spherical hull as the main crack.Considering the combined effect of external uniform pressure and welding residual stress at the weld toe,the stress intensity factor(SIF)is obtained based on the M-integral method.Inserting disturbing cracks at different positions on the spherical hull surface,the interaction and influence between multi-cracks are revealed by numerical calculation.The results show that the existence of the disturbing crack has a great influence on the stress intensity factor of the main crack,and the influence is different with the different location of disturbing crack.The study of the interaction of multiple cracks under different interference factors and the influence of disturbing cracks on the main crack can provide some reference for future engineering applications.

Design optimization of composite egg-shaped submersible pressure hull for minimum buoyancy factor

This paper describes a design optimization study of the composite egg-shaped submersible pressure hull employing optimization and finite element analysis(FEA)tools as a first attempt to provide an optimized design of the composite egg-shaped pressure hull for manufacturing or further investigations.A total of 15 optimal designs for the composite egg-shaped pressure hull under hydrostatic pressure are obtained in terms of fibers’angles and the number of layers for 5 lay-up arrangements and 3 unidirectional(UD)composite materials.The optimization process is performed utilizing a genetic algorithm and FEA in ANSYS.The minimization of the buoyancy factor eB:FT is selected as the objective for the optimization under constraints on both material failure and buckling strength.Nonlinear buckling analysis is conducted for one optimal design considering both geometric nonlinearity and imperfections.A sensitivity study is also conducted to further investigate the influence of the design variables on the optimal design of the egg-shaped pressure hull.

Study on Pressure Coefficient Distribution of the Airship Zhiyuan-1

A wind tunnel tests with different configurations,pitch and yaw angles were performed to study the wind load characteristics of the rigid model of the airship Zhiyuan-1. The rigid model was aimed to simulate a technical demonstrating stratospheric airship named Zhiyuan-1 according to the similarity principle of geometric and Reynolds number. Based on the results of wind tunnel test,the features of pressure coefficient distributions on the surface of the airship were described. It was indicated that the fins and the gondola of airship hardly have the effect on the pressure distribution on the surface of airship,but have obviously effect on the local areas near the fins and the gondola.

Numerical Investigation on Hydrodynamic Characteristics of a Tunneled Planing Hull in Calm Water

A tunneled planing hull has unique hybrid hydrodynamic and aerodynamic characteristics due to the presence of a tunnel.In this paper,experimental and numerical investigations on hydrody namic analysis of a tunneled planing hull are carried out.The resistance tests of models with three dif ferent masses(127.4 kg,159.5 kg,202.9 kg)are conducted for the Froude number in the range of 0.761≤Fn≤1.925.The results of resistance measured by towing tank imply that the tunneled planing hull with a larger displacement has a superior resistance performance.The numerical simulation of Reynolds Average Navier Stokes(RANS)equations based on the finite volume method is performed to analyze the hull characteristics in calm water(M=159.5 kg)with two degrees of freedom(sinkage and trim).The numerical results are compared with the experimental data,which shows good agreement.Pressure distribution,wave profiles and lift forces obtained by SST k-ωand Realizable k-εturbulence models are compared and discussed.Finally,the local fluid flow of streamline around the hull can be divided into four regions due to the presence of a tunnel,which is different from the behaviors of the conventional planing monohull with prismatic form.

基于连续介质损伤力学的钛合金耐压球壳极限强度分析

本文在连续介质损伤力学理论框架下,以深海载人装备耐压球壳结构为研究对象,开展Bonora损伤模型适用性研究。首先,设计TA31钛合金加载卸载试验,依据试验结果,分析Bonora模型参数对材料应力应变响应的影响规律;随后,提出一种模型参数校准方法,依据试验数据确定TA31钛合金的模型参数;最后,将Bonora模型通过VUMAT子程序的形式嵌入到有限元软件中,开展钛合金球壳结构的极限强度分析,并与传统方法进行对比。研究结果表明,在耐压球壳极限强度分析中,引入Bonora模型可以准确模拟耐压球壳结构的失效模式和破坏压力。该模型在材料本构关系中考虑了屈服强度、抗拉强度以及最大塑性应变的影响,结构失效的物理意义更加明确,对材料性能的优化与提升具有指导意义。

潜艇舷侧阀与管路阀件的不同技术特征辨析

潜艇舷侧阀为潜艇的关键件。与管路阀件服务于管路系统功能不同,潜艇舷侧阀用于保障潜艇生命力和潜艇安全性。本文对潜艇舷侧阀与管路阀件的传统结构样式进行对比,分析潜艇舷侧阀与管路阀件的技术要点差异,阐述潜艇通海通舷外系统舷侧阀的基本指标体系和核心要点,提出一体化舷侧阀(通海阀与二道闭锁阀的组合)是潜艇舷侧阀的进化结构型式,最后对特殊型式的潜艇舷侧阀的设计注意事项进行总结。本文通过研究、对比、分析,形成了系统性的潜艇舷侧阀的技术要素,对于开展新型舷侧阀特别是大潜深潜艇舷侧阀的研发具有重要指导意义。

高模量碳纤维复合材料深海耐压壳体结构设计及试验

基于理论公式开展了千米级深海耐压复合材料等截面圆筒计算,在等截面圆筒设计壁厚的基础上,结合有限元仿真开展了轻量化环肋加筋耐压壳体结构优化设计以及千米级深海复合材料耐压壳体的结构稳定性和强度分析,最后通过静水压试验对所设计复合材料耐压壳体进行了考核验证。研究发现,对于环肋加筋复合材料耐压壳体,其失效模式为环向失稳破坏;增加环筋数和增厚蒙皮可以增加耐压壳体的承压能力,相比于增加蒙皮厚度,增加环肋数量对压强质量比的提升更为明显;复合材料铺层的纵向弹性模量对于耐压壳体的承压能力影响显著;由于复合材料生产过程中难以避免的初始缺陷,环肋加筋复合材料耐压壳体的爆破压强应在有限元解基础上进行修正,根据本文试验结果,修正系数建议取值范围为0.5~0.7。

无人潜器耐压壳体选型与承载特征规律研究

[目的]以无人潜器耐压结构轻量化设计技术为背景,以圆柱壳段为对象,开展典型材质耐压柱壳段承载特征规律研究。[方法]首先,根据耐压壳力学特性,分析得出5种典型材质耐压壳段的承载规律和最优临界承载设计值(同时发生应力强度失效和稳定性失效);然后,基于工程需求,进一步探讨不同潜深时各典型材质耐压壳段的承载特性。[结果]结果显示,随着潜深的增加,壳板的失效模式将由稳定性破坏逐渐转变为强度破坏,最优临界承载设计值与材料属性有关;考虑承载效率等因素,在进行圆柱形耐压壳体材料选型时,300 m潜深范围内应选用铝合金壳体,300~600 m潜深范围内宜选用钛合金和玻璃纤维复合材料壳体,600~1000 m潜深范围内建议选用钛合金和碳纤维复合材料壳体,1000~3000 m潜深范围内的最佳方案则选用碳纤维和硼纤维复合材料壳体。[结论]所做研究可为不同材质无人潜器耐压壳体材料选型提供依据。

深海全通透耐压壳蠕变分析

有机玻璃(polymethyl methacrylate, PMMA)是一种透明高分子化合物,具有透明性好、耐腐蚀、重量轻、机械强度优异等优点,可作为全通透潜水器耐压壳体材料的候选材料。PMMA是一种黏弹性材料,当经受长时间的外界高压作用时,由PMMA制成的耐压结构可能发生蠕变,导致其承载能力下降。本文对PMMA耐压壳体进行了有限元分析,基于温度相关的时间硬化蠕变模型,获得了壳体的蠕变变形,并研究了不同类型无开孔和有开孔的耐压壳体的蠕变特性,分析了不同压力和温度下PMMA耐压壳体的应变-时间曲线和位移曲线。分析结果将为大深度载人潜水器全通透耐压舱的设计提供理论参考。

多耐压壳体结构振动传递控制技术研究

相对单耐压壳体,由于多耐压壳体通过舷间连接结构相互耦合,受激励耐压壳体向临近的舷间结构/舷间声介质、临近耐压壳体、轻外壳等主构件传递振动,总体上呈现多路径相互叠加的树形结构,传递路径复杂。采用数值方法,通过建立多耐压壳体有限元模型,基于多耐压壳体耦合特征,分析振动传递路径上基座、激励位置、舷间结构等相关参数对多耐压壳体声学特性影响,从传递路径上开展针对性的结构声学噪声控制技术研究。分析结果可为多体结构的工程设计和振动噪声控制提供有效参考。

Experimental investigation of vortex generator influences on propeller cavitation and hull pressure fluctuations

In this paper,the transient turbulent cavitating flow around a marine propeller behind a ship was investigated experimentally with emphasis on how vortex generator(VG)influences propeller cavitation and hull pressure fluctuations.The experiments were carried out in China Large Cavitation Channel with the closed test section covering 10.5 m in length and cross-section of 2.2 m^2×2.0m^2.The experiment recorded instantaneous cavitation photos of the propeller and pressure fluctuations on the hull surface.The results demonstrate that without vortex generator,the sheet cavitation inception begins at-50°(310°),and then from-50°(310°)to 30°,the extent and area of sheet cavitation increase.When vortex generator installed on the hull,the sheet cavitation inception occurs in advance at-60°(300°),and the sheet cavitation expands to larger rotation range due to the vortex generator.It is shown that the vortex generator with proper geometry and installed location may contribute the highly nonuniform wake to be more uniform,and can make the change of propeller cavitation to be milder,which decrease the pressure fluctuations in this study.Further analysis indicates that the vortex generator may promote the energy distribution to be more uniform in physical and spectral space in some degree.

环肋布局对钛合金圆柱耐压壳内爆过程的影响研究

环肋圆柱壳是深潜器耐压结构的主要形式,但由于极限承载能力和振动特性的需求,存在不同的环肋布局形式。为探究环肋布局对钛合金圆柱耐压壳内爆的影响,基于任意拉格朗日欧拉方法开展数值研究。首先对比试验结果验证液-固-气三相流固耦合数值模型的准确性。然后分析3种环肋布局下圆柱耐压壳水下内爆过程中的结构动态响应、冲击波传播以及能量演化等特征。结果表明,环肋均布时,内爆中心由筒体中部向一端移动。而中部和端部加强时,内爆中心由环肋稀疏位置向密集位置移动,结构动能均存在显著的二次波峰现象。此外,中部加强能有效降低最大冲击波峰值。通过对环肋圆柱壳内爆响应特性的分析,对深海耐压结构的设计具有重要的工程意义。

Non-linear buckling analysis of imperfect thin spherical pressure hull for manned submersible

Thin spherical pressure hulls are used as a human occupancy in deep water applications.DNV and other standards specify the imperfection allowed for pressure hulls.Numerical analyses are carried out to find the buckling pressure for both perfect and imperfect thin spherical pressure hulls,considering the geometric and material non-linearities.It is observed that there is a huge variation in the elastic and inelastic buckling pressure in perfect spherical pressure hulls.Moreover,if the manufacturing imperfections are considered in the inelastic numerical analysis,still there is a reduction in the buckling pressure.Design criteria,for deep water pressure hulls,is that both buckling pressure and yield pressure must be greater than the design pressure.In the elastic analysis,if t/D>0.006 buckling pressure is always greater than the yield pressure whereas in the inelastic analysis,the buckling pressure is falling below the yield pressure for all t/D ratios.Hence,inelastic numerical analysis with manufacturing imperfection has to considered in the design of deep water spherical pressure hulls of manned submersibles.

Numerical simulation and analysis of the underwater implosion of spherical hollow ceramic pressure hulls in 11000 m depth

Pressure hulls play an important role in deep-sea underwater vehicles.However,in the ultra-high pressure environment,a highly destructive phenomenon could occur to them which is called implosion.To study the characteristics of the flow field of the underwater implosion of hollow ceramic pressure hulls,the compressible multiphase flow theory,direct numerical simulation,and adaptive mesh refinement are used to numerically simulate the underwater implosion of a single ceramic pressure hull and multiple linearly arranged ceramic pressure hulls.Firstly,the feasibility of the numerical simulation method is verified.Then,the results of the flow field of the underwater implosion of hollow ceramic pressure hulls in 11000 m depth is analyzed.There are the compression-rebound processes of the internal air cavity in the implosion.In the rebound stage,a shock wave that is several times the ambient pressure is generated outside the pressure hull,and the propagation speed is close to the speed of sound.The pressure peak of the shock wave has a negative exponential power function relationship with the distance to the center of the sphere.Finally,it is found that the obvious superimposed effect between spheres exists in the chain-reaction implosion which enhances the implosion shock wave.

内外置耐压液舱结构力学特性分析

为研究内、外置式耐压液舱结构的力学特性,采用有限元方法分别对内、外置式耐压液舱结构进行计算,并对计算结果给出合理解释。结果表明,在空舱工况、结构尺度及板厚等基本相同的情况下,耐压液舱内置于耐压船体对舱段的应力状况有利,但耐压液舱内置会出现明显的应力集中状况,进而导致极限承载能力的下降;内置式液舱由于实肋板板宽及开口较大,导致其实肋板稳定性要远低于外置式耐压液舱;与此同时,耐压液舱内置带来的施工难度增加及艇内空间上的限制也应该充分考虑。

圆碟形水下滑翔机耐压壳体的优化设计

圆碟形水下滑翔机是一种新型的水下滑翔机,耐压壳体则是滑翔机的重要组件。本文主要研究在不同水深下机身直径、机身高度与机身表面饱和度对耐压壳体表面变形与压力分布情况的影响。通过有限元分析表明在100~300 m水深范围内应减小机身直径,从而降低机身的最大变形量和最大应力。随着机身高度的增加,最大变形量和最大应力的变化规律是先减后增,且随着工作水深的增加,这种趋势越发明显。对于不同机身表面饱和度的圆碟型水下滑翔机,其外壳的最大变形和最大应力分布规律并不统一,机身饱和度较低的圆碟形滑翔机的综合性能较优。本文分析结果可为圆碟形滑翔机在不同深度下的外形设计提供参考。

基于经验公式法的船舶螺旋桨脉动压力计算与软件开发

船体振动是船舶在航行过程中由于各种原因产生的振动,船上90%的振动源于螺旋桨的脉动压力,其可激起艉部振动、上层建筑振动和局部振动。特别是在螺旋桨上方区域,往往由螺旋桨脉动压力而激起局部结构共振或强迫振动,进而造成结构疲劳破坏或居住舒适度减小,因此减少螺旋桨脉动压力产生的振动很有必要。在螺旋桨设计初期,过于复杂的脉动压力计算方法便捷性不高,设计出1款能快速估算螺旋桨脉动压力的软件十分重要。该文基于QT平台和MATLAB软件混合编程,采用经验公式法,开发了1款船舶螺旋桨脉动压力快速估算软件,探讨了脉动压力的影响因素及其变化规律。结果表明:船舶剖面形状参数、船舶种类和螺旋桨转速对螺旋桨脉动压力影响较大。该项研究成果可为船舶减振降噪提供参考。