Finite Element Analysis of In-Plane Displacements and Von-Mises Stresses in Ellipsoidal and Circular Cylinderical Petroleum Tankers

Road tankers are the most used means of transporting petroleum product to end users due to its cost effectiveness and energy-efficiency. The cylindrical tank has been well designed for by ASME VIII divisions 1 and 2 using analytical equations. Petrol tankers are not circular but elliptical probably for stability during transportation. This paper has used the finite element method to investigate in-plane displacements and Von-Mises stresses in both circular and elliptical cylindrical tanks under full loading. An elliptical OANDO? tanker of 66.78 m3volume and shell thickness of0.2 mmand an equivalent volume circular cylindrical tank was used for the simulation. MATLAB? was used to generate geometrical mesh model of the petroleum tankers, extract element coordinates and conduct the finite element analysis. Plane strain condition was used in analyzing a section of the petroleum tanker. It was observed that an equivalent volume circular cylindrical tank was under a higher internal pressure (16,858 N/m2) compared to the elliptical cylinder (14,480 N/m2). Von-Mises stress and in-plane displacements showed direct linear relationships with internal fluid pressure. Von-Mises stress in the elliptical tank was found to be lower (5.7 × 106 N/m2) than for the circular tank (8 × 106 N/m2). In plane displacements was zero in the longitudinal direction for both tanks and of the order of 10-4 mm in the y-direction for both tanks with the circular larger by about 2.5 × 10-3 cm. So in addition to tank stability on the lorry, the Von-Mises stresses were lower as well for the elliptical tank. It was also observed that Von-Mises stresses were far below the yield stress of the steel plate. However, the effect of weldment area on lowering of yield stress was not studied. Stress values were validated using analytical method and found to be insignificantly different (P > 0.05).

MULTIPOINT BLANK HOLDER FORCE CONTROL IN HYDROFORMING OF FUEL TANK

The study of multipoint blank holder force（BHF） control is carried out for hydroforming a complicated shape motorcycle fuel tank. By finite element method （FEM） simulation, the configuration of multipoint blank holder cylinders and the setting of local BHF are optimized, and the influences of the multipoint BHF on the hydromechanical deep drawing and conventional hydroforming processes are studied. The desired fluid pressure and whole BHF are predicted for hydromechanical deep drawing process. Finally, simulation results are testified by forming experiment, and they are in agreement very well.

Generation and Properties of Freak Waves in A Numerical Wave Tank

Freak waves are generated based on the mechanism of wave focusing in a 2D numerical wave tank. To set up the nonlinear numerical wave tank, the Boundary Element Method is used to solve potential flow equations incorporated with fully nonlinear free surface boundary conditions. The nonlinear properties of freak waves, such as high frequency components and wave profile asymmetry, are discussed. The kinematic data, which can be useful for the evaluation of the wave forces exerted on structures to avoid underestimation of linear predictions, are obtained, and discussed, from the simulated results of freak waves.

The Computer Aided Integrated Design and Analysis of Oil Tank in Vehicle

This paper creates 3D solid model and assembly of U RJ 92-6 oil tank and analyses its strength by integrated CAD/CAE/CAM software I-D EAS. Through integrated simulation in computer, design efficiency and quality of oil tank is greatly improved. Adopting integrated CAD/CAE/CAM software to carry out integrated research to equ ipment and products, we will be able to take overall analysis in aspects of 3-D solid modeling, pre-assembly and strength, etc., to realize non-paper designi ng and parallel designing. Problems can be found and settled during designing, w hich will increase designing efficiency and one-time success rate and realize o ptimum designing for products.

Simulating regular wave propagation over a submerged bar by boundary element method model and Boussinesq equation model

Numerical models based on the boundary element method and Boussinesq equation are used to simulate the wave transform over a submerged bar for regular waves.In the boundary-element-method model the linear element is used,and the integrals are computed by analytical formulas.The Boussinesq-equation model is the well-known FUNWAVE from the University of Delaware.We compare the numerical free surface displacements with the laboratory data on both gentle slope and steep slope,and find that both the models simulate the wave transform well.We further compute the agreement indexes between the numerical result and laboratory data,and the results support that the boundary-element-method model has a stable good performance,which is due to the fact that its governing equation has no restriction on nonlinearity and dispersion as compared with Boussinesq equation.

Simulation of Fully Nonlinear 3-D Numerical Wave Tank

A fully nonlinear numerical wave tank (NWT) has been simulated by use of a three-dimensional higher order boundary element method (HOBEM) in the time domain. Within the frame of potential flow and the adoption of simply Rankine source, the resulting boundary integral equation is repeatedly solved at each time step and the fully nonlinear free surface boundary conditions are integrated with time to update its position and boundary values. A smooth technique is also adopted in order to eliminate the possible saw-tooth numerical instabilities. The incident wave at the uptank is given as theoretical wave in this paper. The outgoing waves are absorbed inside a damping zone by spatially varying artificial damping on the free surface at the wave tank end. The numerical results show that the NWT developed by these approaches has a high accuracy and good numerical stability.

基于实测沉降多因素影响下储罐的屈曲变形分析及加固研究

在役储罐往往因罐底不均匀沉降导致罐壁产生较大变形,影响储罐的安全运行.为了研究沉降作用下罐壁的变形与罐底沉降的关系,采用有限元模拟方法,并基于实测沉降数据,研究了不同沉降加载比例、罐内储液高度对罐壁变形的影响.此外,探究了储罐加固措施位置对加固效果的影响.结果表明:罐底沉降向下位移时,罐壁向外侧位移,而罐底沉降向上位移时,罐壁向内侧位移,且罐底沉降位移曲线与罐壁位移曲线大致相同;随着罐内储液高度上升,罐壁位移减小,表明罐内储液高度的提升可以增强储罐抵抗不均匀沉降,降低对罐壁变形的影响;加强圈对储罐的加固作用取决于其在罐壁上的位置,与未加固措施的储罐相比,设置加强圈后储罐临界沉降比例系数LPFs增大,且LPFs在沉降罐罐壁发生屈曲破坏的位置时达到最大,对储罐的加固效果最佳.

大型集装箱船甲醇燃料舱结构设计

针对甲醇作为船舶替代燃料的特点,提出一种适用于大型集装箱船的甲醇燃料舱设计方案,以一艘大型集装箱船为例,采用有限元方法来验证甲醇燃料舱区域的结构强度,同时探讨燃料舱端部节点设计对船体结构强度的影响。为大型集装箱船甲醇燃料舱的结构设计提供参考。

基于实测数据立式热水储能罐罐壁力学特性分析

为掌握立式储能罐结构的受力特征,基于某30 000 m~3立式热水储能罐项目,依托远程监测技术采集了运行状态下罐壁应力和温度数据,将采集结果与考虑罐底摩擦接触约束建立的有限元模型分析结果进行比较,验证了此有限元模拟方法的合理性;依托实测温度数据,研究了立式储能罐罐壁热力耦合作用下罐壁位移以及应力分布规律。结果表明:罐壁底部和顶部为温度影响敏感区域,温度升高,使其产生压应力;对于环向应力,在底部受温度荷载影响较顶部更显著;而对于竖向应力,影响主要是罐壁底部;温度对罐壁变形影响较大,在空罐时,最大位移位置出现在罐壁最顶端;而满罐时最大变形位置出现在中上部的位置,温度作用大于静水压力对罐壁变形的影响。

拱顶储罐罐顶缺陷漏磁检测技术研究

针对拱顶储罐在长期使用过程中,罐顶因环境因素和储存介质的影响造成内外壁腐蚀损伤而严重威胁储罐安全运行的问题,对拱顶储罐罐顶进行了缺陷漏磁检测技术研究。建立了罐顶漏磁检测三维模型,并采用有限元分析方法对该模型进行求解;分析不同影响因素对漏磁信号特征的影响,通过对漏磁场峰值的拟合,得到了不同影响因素对罐顶缺陷漏磁场的影响规律。结果表明,外壁半球形缺陷漏磁检测信号峰值与缺陷半径符合线性拟合规律,内壁半球形缺陷漏磁检测信号峰值与缺陷半径符合二次拟合规律,加强肋处形成的漏磁检测信号与缺陷检测信号波形相反。通过试验验证了漏磁检测方法能有效检测储罐罐顶的缺陷,并能确定缺陷的深度和位置。

基于流固耦合的LNG储罐外罐地震响应分析

为研究流固耦合对LNG储罐外罐的地震响应问题,采用振动台试验和数值仿真相结合方法对不同地震波下不同液体高度的LNG储罐进行震动分析。试验结果表明:地震会改变罐体加速度和位移的分布情况,不同地震波和不同液体高度对位移和加速度的放大效应有着不同的影响,在El Centro波、Taft波和SHM2波作用下,流体振荡产生的减震作用和流体压力产生的附加惯性作用能够减小储罐中部的位移,但对加速度有所放大。利用时程分析法对5000m^(3)LNG储罐的位移和环向应力进行地震模拟分析,结果表明:储罐的环向应力呈现出中间大两头小的走势,在罐高的1/4h、1/2h和3/4h上出现极值;位移沿罐高度方向先增加后减少,峰值出现在1/4h、1/3h、1/2h和3/4h处。因此在LNG储罐抗震设计时,应考虑流固耦合效应对结构的影响,在1/4h、1/3h、1/2h和3/4h处的薄弱位置,宜采用增加壁厚、设置阻尼器和钢筋加密等措施增强结构的可靠性和安全性。

大型LNG储罐预冷模型构建和预冷参数计算

预冷作业是大型液化天然气(Liquified Natural Gas, LNG)储罐投用前最关键的环节。预冷介质用量、预冷时间以及储罐各部分构件降温速率的控制是大型LNG储罐预冷作业得以顺利进行的重要保证。依托某大型LNG接收站项目,旨在较精确地计算预冷介质用量。选取最复杂的大型LNG储罐为研究主体,综合考虑保冷材料比热容变化、储罐日常蒸发、预冷介质输送管道漏热等因素,搭建有限元模型进行数值模拟计算,并利用上述结果计算预冷模型中的参数。预冷模型计算结果表明:大型LNG储罐预冷工作实施过程中,提高预冷降温速率可减少预冷介质用量和预冷时间,同时降低大型LNG储罐漏热所消耗的预冷介质占比,但需要注意储罐内元件的温差;考虑输送管线和机械结构漏热,预冷介质用量增多,与现场实际数据更吻合,相对误差不超过5%。研究结果对指导大型LNG储罐预冷操作具有参考价值。

基于有限元法的可移动罐柜拟静力分析

基于晃动流体力学模型,将可移动罐柜运输过程动荷载等效为拟静力荷载,采用有限元ANSYS软件平台,对WB2258-1型6立方药剂罐可移动罐柜进行了11种主要工况的拟静力强度分析,结果表明,可移动罐柜罐体的应力显著小于框架和裙座应力,最危险应力点出现在框架结构,最小安全系数为1.04。对有限元计算发现的2种最危险工况进行了吊装、叉举和垂直冲击试验,测得的主要变形量都满足规范要求。本文的研究工作为6 m^(3)药剂储存用可移动罐柜的安全性评估和优化设计提供了有价值的参考。

碰撞冲击载荷下船用LNG燃料罐的结构强度评价

针对LNG燃料船舶在碰撞事故发生情况下的LNG燃料罐结构安全问题,应用有限元方法建立有限元分析模型,并参照规范形成碰撞载荷计算及加载、结构强度评价等方法,提出碰撞冲击载荷作用下船用LNG燃料罐结构安全评价的解决方案。以18 m~3船用LNG燃料罐作为研究对象进行仿真计算分析,评估碰撞载荷作用下LNG燃料罐筒体、封头、内外容器间的支撑结构及鞍座等部件的应力水平和总体结构安全状况。结果表明,该船用燃料罐各构件应力均小于规范中的许用值,强度满足要求,符合行业规范,验证有限元分析方法在LNG燃料罐结构强度评价的可行性;内容器是工况条件下最容易失效的结构,其最大应力可达123.63 MPa,与许用值相差13.07 MPa。

基于多纤维RVE和聚类分析的低温复合材料贮箱跨尺度计算

采用碳纤维增强复合材料贮箱可显著减轻运载火箭的质量,但贮箱在低温环境中机械-热载荷作用下的分析方法有待研究,尤其是要准确地考量纤维与基体间产生的细观热应力。采用包含多根纤维的代表体元模型,结合基体、纤维失效准则,建立了细观应力场及失效预测模型,并采用k-means聚类方法开展降维计算,提出了一种高效、高精度复合材料贮箱跨尺度分析方法。结果显示:该方法能够根据纤维和基体的热、力学常数准确地预测复合材料单层板的弹性常数和破坏强度;结合某贮箱模型,模拟了机械-热载荷共同作用下复合材料贮箱渗漏失效的发生过程,给出了明确的失效载荷及失效状态。

大型锻压设备的液压系统设计

本文结合锻压设备的特点及锻压设备的发展,对锻压设备的液压系统设计流程进行了简单的介绍。并以一种典型的大型液压系统为例,对液压分配系统、液压泵站的设计进行了阐述。其中,由于各手册、文献中对液压系统油箱强度设计方面的介绍较少,本文基于有限元分析的方法,研制了50000L大型液压站。该液压系统及液压站经测试、使用,性能符合使用要求。

大型液氢球罐的支柱连接结构设计与性能对比研究

围绕双层液氢球罐支柱连接设计,建立热-结构耦合数值模型,研究大型液氢球罐中支柱与内罐连接处应力与应变的分布规律,分析不同连接形式对其受力性能及传热性能的影响。研究表明:支柱与内罐连接部位无论采用标准规定的何种连接结构,当考虑温度载荷时,最大应力及应变均大幅增加;在四种支柱-内罐连接结构中,直圆形连接结构的最危险处应力值是最小的,该结构下的最大应力数值为331.33 MPa,而直接连接结构具有最好的绝热性能,该结构下的热流密度为758.75 W·m^(-2)。由于四种连接形式均能满足应力校核条件,故从减小漏热的角度出发推荐采用直接连接结构作为支柱与内罐连接部位的连接方式。该研究结果可为大型液氢球罐支柱与内罐连接处的设计和选型提供理论指导。

聚脲涂覆油箱抗冲击仿真研究

为提高车载油箱抗冲击能力、降低结构变形和损伤程度,以聚脲涂覆油箱为研究对象,通过材料试验获取Air1608型聚脲弹性材料力学性能参数。在普通油箱表面均匀喷涂5 mm厚聚脲材料,分别开展普通油箱和聚脲涂覆油箱在5 m高度自由跌落工况的有限元仿真计算和试验,仿真结果与试验结果有较好的一致性,聚脲涂覆油箱局部结构最大变形量与涂覆前相比降低约32%。同时开展在油箱内侧和双侧均匀喷涂聚脲情况下的仿真计算,研究发现双侧喷涂聚脲对油箱结构的弹性变形有良好的限制作用,能够减小油箱塑性变形,抗冲击性能较好。

2×6MV串列加速器钢桶的机械设计与应力校核

钢桶是串列加速器主体的核心部件,此前国内大多数学者都是根据经验或参照外国同类产品进行串列加速器钢桶的机械设计,因而对其的研究缺乏完善的理论依据。针对此问题,该文以2×6MV串列加速器为基础开展理论设计研究。在保障其结构强度与气密性的前提下,通过控制外壁厚度来实现桶身质量减小的目的。首先基于无矩理论,钢桶选取标准椭圆形封头,外壁最小名义厚度为9 mm;然后根据卧式容器近似分析与计算方法,确定出鞍座底板中心至封头切线的最佳距离为0.64 m;最后建立钢桶有限元模型,开展应力与变形分析。该研究通过对封头形状、外壁厚度、鞍座位置的设计与选择,得出了使钢桶质量最小的机械参数,为2×6MV串列加速器钢桶的实际加工和其它有相似结构的串列加速器的机械设计提供了理论依据。

双燃料集装箱船中货舱典型舱段有限元分析

针对双燃料集装箱船燃油舱布置在水密横舱壁的特点,其存在一系列高应力区域,具有结构硬点的节点设计存在一定难度。基于BV规范要求,对某大型甲醇双燃料集装箱船中货舱船体结构开展舱段有限元计算分析,并进行优化设计;对于较难处理的节点,采用子模型法对重点关注区域进行细网格分析,比较各种优化节点形式对节点受力的改善。