ANALYSIS OF SOUND RADIATION FROM THE RING-STIFFENED CYLINDRICAL SHELL COATED WITH VISCOELASTIC LAYER IN FLUID MEDIUM

The Donnell theory of shell is applied to describe shell motion and layer motion is described by means of three-dimensional Navier equations.Using deformation harmonious condi- tions of the interface,the effects of stiffeners and layer are treated as reverse forces and moments acting on the cylindrical shell.In studying the acoustic field produced by vibration of the sub- merged ring-stiffened cylindrical coated shell,the structure dynamic equation,Helmholtz equation in the fluid field and the continuous conditions of the fluid-structure interface compose the cou- pling vibration equation of the sound-fluid-structure.The extract of sound pressure comes down to the extract of coupling vibration equation.By use of the solution of the equation,the influ- ences of hydrostatic pressure,physical characters and geometric parameters of the layer on sound radiation are discussed.

Experimental and Numerical Investigations of the Dynamic Response of Ring-Stiffened Cylinder Subjected to Underwater Explosion

Experimental and numerical investigations were carried out on the free-free end ring-stiffened cylinder subjected to underwater explosion loading. Numerical analysis was carried out by using the MSC.DYTRAN finite element code and the results were compared with experiment results. General coupling was used to simulate the interaction between fluid and structure. The strain rate effect, geometric nonlinearity and initial abnormity in shape were considered. The effective plastic stress and the strain of shell between ribs on different locations were compared and damage mechanism were analyzed..

Stability characteristics of ring-stiffened cylindrical shells under different longitudinal and transverse external pressures

Because ring-stiffened cylindrical shell structures have many merits, they are widely used in many areas. However, as the strength of steel increase continuously, ensuring of the structure stability is becoming more and more important. Therefore, it is necessary to carry on a more particular analysis. Based on the understanding and analysis of the characteristics of stability for a ring-stiffened cylindrical shell under uniform external pressure and under external single pressure, the characteristics under different cross uniform external pressures are analyzed, and the regularity of it is also gotten. The curve of stability given various geometrical parameters under different cross uniform external pressures is protracted by the analysis of the theory. The conclusion not only improves the theory structural mechanics, it also was important effects on engineering calculation and design.

DYNAMIC BUCKLING OF STATICALLY PRELOADED RING-STIFFENED CYLINDRICAL SHELLS UNDER AXIAL FLUID-SOLID IMPACT LOADING

The Initial Imperfection Amplified Criterion is applied toinvestigate the geometric nonlinear dynamic buckling of staticallypreloaded ring-stiffened cylindrical shells under axial fluid-solidimpact. Tak- ing account of the effects of large deformation andinitial geometric imperfection, the governing equations are obtainedby the Galerkin method and solved by the Runge-Kutta method. Theeffects of static preloading (uniform external radial pressure) onthe buckling features and the load-carrying ability of ring-stiffenedcy- lindrical shells against axial impact are discussed.

Limit analysis of viscoplastic thick-walled cylinder and spherical shell under internal pressure using a strain gradient plasticity theory

Plastic limit load of viscoplastic thick-walled cylinder and spherical shell subjected to internal pressure is investigated analytically using a strain gradient plasticity theory. As a result, the current solutions can capture the size effect at the micron scale. Numerical results show that the smaller the inner radius of the cylinder or spherical shell, the more significant the scale effects. Results also show that the size effect is more evident with increasing strain or strain-rate sensitivity index. The classical plastic-based solutions of the same problems are shown to be a special case of the present solution.

Acoustic radiation force on a cylindrical composite particle with an elastic thin shell and an internal eccentric liquid column in a plane ultrasonic wave field

A model with three-layer structure is introduced to explore the acoustic radiation force(ARF)on composite particles with an elastic thin shell.Combing acoustic scattering of cylinder and the thin-shell theorem,the ARF expression was derived,and the longitudinal and transverse components of the force and axial torque for an eccentric liquid-filled composite particle was obtained.It was found that many factors,such as medium properties,acoustic parameters,eccentricity,and radius ratio of the inner liquid column,affect the acoustic scattering field of the particle,which in turn changes the forces and torque.The acoustic response varies with the particle structures,so the resonance peaks of the force function and torque shift with the eccentricity and radii ratio of particle.The acoustic response of the particle is enhanced and exhibits higher force values due to the presence of the elastic thin shell and the coupling effect with the eccentricity of the internal liquid column.The decrease of the inner liquid density may suppress the high-order resonance peaks,and internal fluid column has less effects on the change in force on composite particle at ka>3,while limited differences exist at ka<3.The axial torque on particles due to geometric asymmetry is closely related to ka and the eccentricity.The distribution of positive and negative force and torque along the axis ka exhibits that composite particle can be manipulated or separated by ultrasound.Our theoretical analysis can provide support for the acoustic manipulation,sorting,and targeting of inhomogeneous particles.

Research on Strengthening Method of Concave Cone-toroid-cylinder Combined Shell with Initial Imperfection

As a new joint structure,the impact of initial imperfection to stress of Concave cone-toroid-cylinder combined shell was analyzed. Firstly the location and shape of combined shell's initial imperfection caused by welding was studied. Secondly dominated stress was chosen after comparing varioustypical stress. Then it was analyzed that the influence of imperfection to dominated stress via changing the shape of frame's deflection and shell's concave-convex. At last the strengthening case for combined shell with imperfection was pointed out. The conclusions are:(1) Stress of frame 9 is more sensitive to initial imperfection than circumferential stress of toroidmidsurface,which is a new concern;(2) To strength the frames in the sides of toroid not only can decrease the stress of frame,but also can reduce the circumference stress of toroid's midsurface.

ANALYTICAL SOLUTION OF AXIAL SYMMETRICAL WALL TEMPERATURE DISTRIBUTION FOR HOLLOW CYLINDER

Using the variable transformation method,the formulae of the axial symmetrical wall temperature distribution during steady heat conduction of a hollow cylinder are derived in this paper.The wall temperature distribution and the wall heat flux distribution in both axial and radial direction can be calculated by the temperature distribution of the liquid medium both inside and outside the cylinder with temperature changing in axial direction.The calculation results are almost consistent with the experience results.The applicative condition of the formulae in this paper consists with most of practice.They can be applied to the engineering calculation of the steady heat conduction.The calculation is simple and accurate.

BUCKLING OF COOLING TOWER SHELLS WITH RING-STIFFENERS

With the stability analysis of hyperbolic cooling tower shells with ring-stiffeners. our paper proposes the linear pre-buckling consistent theory. The numerical result shows that this linear analysis method is very effective and practical in engineering, for its precision of compulation is up to the level of the nonlinear analysis when it is used for the study of critical loads of the hyperbolic cooling tower which is mainly governed by wind pressure and for the study of the effect of some oilier factors concerned in design on the buckling of shells. Based on that, we have obtained a scries of conclusions whicii will greatly benefits the engineering design when discussing the effect on the critical windloading of the shell which is caused by the following factors such as the position of rings, the number of rings and the dead weight.

ANALYTICAL SOLUTION OF RADIATED SOUND PRESSURE OF RING－STIFFENED CYLINDRICAL SHELLS IN FLUID MEDIUM

In this paper, analytical formularions of radiated sound pressure of ring-stiffenedcylindrical shells in fluid medium are derived by means of Hamilton's principleHuygens principle and Green function . These formulations Can be used to compute the sound pressure of the shell's surface nearfield and farfield.

NONLINEAR BUCKLING ANALYSIS OF HYPERBOLIC COOLING TOWER SHELL WITH RING-STIFFENERS

This paper is concerned with a numerical solution of hyperbolic cooling tower shell, a class of full nonlinear problems in solid mechanics of considerable interest in engineering applications. In this analysis, the post-buckling analysis of cooling tower shell with discrete fixed support and under the action of wind loads and dead load is studied. The influences of ring-stiffener on instability load are also discussed. In addition, a new solution procedure for nonlinear problems which is the combination of load increment iteration with modified R-C are-length method is suggested. Finally, some conclusions having important significance for practice engineering are given.

Dynamics of luffing motion of a hydraulically driven shell manipulator with revolute clearance joints

In this study,a modeling method for investigating the dynamic characteristics of a hydraulically driven shell manipulator with revolute clearance joints is presented.This model accounts for the effect of the clearance,the flexibility of the rotating beam,and the coupled dynamic characteristics of the hydraulic cylinder.A modified contact force model was developed to simulate the physical properties of realistic revolute joints with small clearances,heavy loads,and variable contact stiffnesses and damping coefficients with variations of the indentations.Considering the strong coupling relationship between the hydraulic cylinder and the flexible beam,a system equation of motion combining the state variables of the hydraulic cylinder and mechanical system was established.The complex nonlinear friction force of the hydraulic cylinder motion was constructed using a modified Lu Gre model,and the parameters of the friction model were identified using intelligent identification algorithms.Moreover,a test system for the shell manipulator was established to achieve experimental validation.Finally,the effects of the clearance size and the stiffness of the cylinder support on the dynamic response were investigated.

Nonlinear Buckling Analysis of Pre-stressed Ring-Stiffened Circular Cylindrical Shells Under External Pressure

This paper is concerned with the nonlinear buckling behavior of pre-stressed ring-stiffened thin circular cylindrical shells under external pressure.According to the geometrical nonlinearity,governing equations are derived by incorporating initial stresses based on Donnell-type shell theory.The "smeared stiffeners" approach is used for ring stiffeners.The numerical analyses are conducted by Gelerkin's method to obtain critical buckling loads of shells.This study shows effects of initial stresses on stability of shells.Moreover,effects of initial stresses on buckling modes of shells are discussed.

shell煤气化装置锁灰阀的应用及气缸改进

简述shell煤气化装置开车运行中锁灰阀出现关不到位、阀塞、和阀座卡死等问题,介绍该阀的主要技术规格和故障分析以及对气缸控制气路改进,设备运行稳定,节约了生产成本。

双层耐压加筋圆柱壳结构承载能力与抗爆性能分析

[目的]为了探究不同层间加强筋形式对双层圆柱壳承载能力与抗爆性能的影响,对4种双层加筋圆柱壳在静水压力与水下爆炸载荷下的响应进行数值研究。[方法]首先,建立等质量不同结构形式加筋圆柱壳的有限元模型;然后,利用有限元软件ANSYS计算分析圆柱壳的结构形式对圆柱壳强度、稳定性和极限承载能力的影响;最后,利用有限元软件Abaqus/Explicit计算分析圆柱壳的结构形式对圆柱壳在爆炸载荷下的变形和塑性应变的影响。[结果]结果显示,与等质量的传统单层加筋圆柱壳结构相比,I形加强筋双层圆柱壳的承载能力具有较大的优势;当爆炸载荷水平较低时,肋骨间距较小的双层圆柱壳的抗爆性能相当,而当爆炸载荷水平较高时,肋骨间距较小的双层圆柱壳的抗爆性能则会降低。[结论]研究表明,合理设计双层加筋圆柱壳的结构形式能够获得承载能力与抗爆综合性能较好的设计方案。

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。

薄壁长筒壳体加工工艺和定位工装设计

分析薄壁长筒壳体加工易变形产生的原因,介绍壳体的加工工艺流程,设计两种定位装夹工装,对比两种定位工装的工作原理及使用方法,有效解决了加工过程中的变形问题,使加工精度达到设计要求,提高生产率。

基于圆柱壳舱段船舶典型动力设备系统性能分析

双层隔振系统广泛应用于车辆、船舶、机械等行业。船舶机械设备振动通过隔振装置传递到船体结构进而向水下辐射噪声,建立基于潜艇圆柱壳舱段的典型动力设备双层隔振系统模型,研究了筏体结构、基座结构等参数对隔振系统、隔振性能的影响规律。筏体结构对圆柱壳舱段的动力设备,在一定频率下隔振性能影响明显,安装阻振结构可进一步提高系统的隔振性能,安装阻振质量后,在0~1 000 Hz频段隔振系统的平均振级落差提高了0.2 dB。合适的阻振质量安装位置在900~1 000 Hz最大可提高系统的隔振性能7.3 dB。研究成果可为舰船的动力设备设计提供借鉴。

考虑遮挡和二次散射的修正板块元算法

对外部加环肋圆柱壳体的声散射研究表明,部件之间的互散射(二次散射)对反向散射声场有重要贡献。本文在板块元算法基础上,加入对遮挡和二次散射的判段,得到修正的板块元算法。通过计算外部加环肋圆柱壳体的目标强度,展现了二次散射和遮挡效应在不同角度的交替作用;而在考虑透射效应后,在高频段和低频段呈现出不同的效果。修正板块元计算结果与实测数据比较,两者一致。

有限水深环境圆柱壳声辐射及传播特性

采用虚源法建立了浅水环境中二维圆柱壳的振动声辐射数学物理模型,推导了浅水上下界面对柱壳声辐射的散射作用,利用柱函数转移公式推导了虚源和圆柱壳的互辐射阻抗矩阵,描述了不同虚像声场对本体圆柱壳的负载。利用典型圆柱壳参数和浅水参数初步计算了浅水对圆柱壳振动声辐射的影响规律及水深、潜深对声场分布和衰减特性的影响规律。研究结果表明:针对文中典型模型参数,圆柱壳没入水中深度超过0.5 m,其振动响应和表面声压与在无限水域中一致;水面和水底对圆柱壳辐射声的反射与本身辐射在有限水域内形成复杂驻波;有限水域的近场衰减特性与无限水域中的近场衰减特性基本一致;由于驻波的影响,远场声压衰减曲线相较无限水域的柱面波衰减曲线上下起伏6 dB左右,但总体衰减趋势基本一致。