The buckling behavior of U-shaped bellows under pressure loads

Bellows exhibit unique buckling behavior because of their peculiar shape. The buckling behavior and buckling criteria of bellows subjected to pressure loads are examined analytically and compared with test results. Under internal pressure, two different buckling modes can occur, namely, in-plane squirm and column squirm. On the other hand, under external pressure, bellows deformation is different from that under internal pressure.

The authors investigated various types of buckling behavior of bellows by means of simplified methods of analysis and finite-element analyses and conducted validation tests under various conditions. On the basis of these analytical and experimental studies, a rational method for evaluation of the buckling of bellows is proposed.     

In-plane instability tests of bellows subjected to internal pressure and deformation load

The in-plane instability of U-shaped bellows is analyzed. The in-plane instability critical pressure of bellows which are subjected to zero, tensile and compressive deformation are measured experimentally. The in-plane instability critical pressure of bellows under compressive deformation is apparently lower than that under zero deformation, and the in-plane instability critical pressure of bellows under tensile deformation is higher than that under zero deformation.     

Formulae and graphs of elastic stresses for design and analysis of U-shaped bellows

This paper presents equations describing the meridional and circumferential elastic stress levels at the root and crown due to external pressure and axial deflection of U-shaped bellows. The derivation is based on a statistical analysis of selected bellows configurations. The mathematical formulations and various graphical representations are proposed as aids to bellows design and analysis.     

A simplified method of evaluating ratcheting in bellows and a test of its validation

The ratcheting mechanism of a bellows under a pressure load and a cyclic-displacement load is studied. In this paper, it is shown that the ratcheting mechanism of bellows cannot be explained by conventional ratcheting models, such as a parallel two-bar model or the Bree model. In order to represent the ratcheting behavior of bellows, the authors assume that this mechanism is governed by the interaction of bending moments between the crown and the root of each convolution, and they develop a rational-analysis model by using a rectangular beam. The model is extended to bellows, and a simplified evaluation method to predict the ratcheting limit and the enhanced creep strain is proposed. The validity of this method is verified by FEM analyses and experiments.     

发电电动机空冷器波纹管补偿器失稳原因分析及处理

本文通过介绍某抽水蓄能电站发电电动机空冷器波纹管在试运行期发生的失稳故障,其主要原因是选型和安装不符合要求造成,说明了正确地选择波纹管结构,严格按工艺要求安装,是保证抽水蓄能技术供水波纹管补偿器安全可靠性的有效措施.     

带波纹管伸缩节的地面钢衬钢筋混凝土管道对活断层错动变形的适应性研究

对于跨活断层管道,在地震等外力作用下采用地面明钢管易产生支座扭曲破坏或钢管落梁破坏,以滇中引水工程过活动断裂的观音山倒虹吸为例,选取钢衬钢筋混凝土管道,在过活动断裂带管线中布置若干波纹管伸缩节以吸收错动位移,研究不同工况下管道和伸缩节对活动断层蠕滑、粘滑变形的适应性。结果表明,波纹管伸缩节可承担大部分的断层错动变形,减小断层错动对管道的影响;钢衬钢筋混凝土管道+波纹管伸缩节的布置方案不仅对断层蠕滑错动具有较好的适应性,且在粘滑错动情况下,也能控制破坏发生范围,以预先采取工程措施减少二次灾害的发生。     

Effect of the elliptic degree of Ω-shaped bellows toroid on its stresses

This paper investigates the stresses of Ω-shaped bellows with ideal and elliptic toroids imposed by internal pressure or deflection, and analyzes the stress distribution state. The calculated stress results of Ω-shaped bellows with elliptic toroid correspond with our experiment. This paper also analyzes the effect of the toroid elliptic degree on the bellows stresses. It shows that the toroid elliptic degree needs to be greatly reduced in the manufacturing process.     

基于ANSYS的U形波纹管热应力分析

本文基于非线性有限元理论,针对波纹管轴向刚度大,径向刚度小,能承受较大的轴向位移和一定的内、外压力的特点,采用ANSYS有限元软件首次对整体波纹管进行热-应力耦合分析,研究波纹管在交变载荷和温度场的作用下刚度与位移、应力应变情况,并预测波纹管的疲劳寿命.     

光管与波节管传热性能试验研究

本文对Hsn70-1A波节管与Hsn70-1A光管进行了不同风速下传热性能的对比试验研究。通过试验结果可以看出波节管的传热性能明显优于光管，本实验的风速范围0．8～8m／s。     

Design diagrams and formulae for U-shaped bellows

The U-shaped bellows is a type of expansion joint very widely used in pipelines. This paper presents some design diagrams and design formulae for such a bellows in a manner intended to enable the pipeline designer to evaluate more easily the elastic characteristics; maximum stress, elongation and reaction stress.     

Service life of corrosion pitted pipes subject to fatigue loading and hydrogen embrittlement

The structural service life of brittle material pipes with exterior corrosion pits is likely to depend on crack initiation and crack development and this may be influenced by pressure loading fluctuations and the possibility of material hydrogen embrittlement. Recently developed methods are used to estimate the cracking pattern, the failure state of the crack development from external pits and the rate of Hydrogen-Assisted Cracking under fluctuating loadings. The effect of hydrogen from the surrounding environment on the cracking rate is formulated using a generalized form of Paris' law. The depth of cracks initiated from surface pits is estimated as a function of pipe age. A realistic example is presented and the results discussed.     

Sensitivity of pipelines with steel API X52 to hydrogen embrittlement

The following cases of hydrogen influence on pipeline metal were considered: gaseous hydrogen under internal pressure in notched pipes and electrochemically generated hydrogen on external pipe surface from soil aqueous environment. The burst tests of externally notched pipes under pressure of hydrogen and natural gas (methane) were carried out after the pipe has been exposed to a constant “holding” pressure. It has been shown that even for relatively “soft” test conditions (holding pressure p = 20 bar and ambient temperature) the gaseous hydrogen is able to penetrate into near surface layers of metal and to change the mechanism of local fracture at notch. The sensitivity to hydrogenating of given steel in deoxygenated, near-neutral pH NS4 solution under soft cathodic polarisation was studied and the assessment local strength at notches in pipeline has been made for this conditions. Here, the relationship between hydrogen concentration and failure loading has been found. The existence of some critical hydrogen concentration, which causes the significant loss of local fracture resistance of material, was also shown.     

A study of external surface pressure effects on the properties for lithium-ion pouch cells

Lithium-ion pouch cells are widely used in electric vehicles because of their high energy density than other structures. There is an unavoidable external surface pressure between the cells in the process of packing and driving of electric vehicles. The influence of external surface pressure on the main properties of the lithium-ion pouch cell has been studied, which is of great significance to packing batteries and reusing retired cells. In this study, a testing device applied for the measurement of constant external surface pressures of lithium-ion pouch cells was first proposed and the different pressure stress-strain distribution on the external surface of cells under semirigid material pads were analyzed by simulation. The effects of pressure on the capacity, internal resistance, and open circuit voltage of fresh and aged LiNi_xCo_yMn_zO₂ (NCM) lithium-ion pouch cells are analyzed through experiments under 1 Mpa external surface pressure. The results show that the internal resistance of fresh cells tends to decrease. The average percentage of the maximum reduction of internal resistance is 13.28%. The experiments also demonstrate that the capacity of aging cells increased by 2.3%. Irreversibility of capacity improvement indicates applying appropriate external surface pressure can improve the secondary utilization efficiency of aging cells.     

深埋有压隧洞平行四边形管片衬砌结构受力特性研究

水荷载是深埋有压隧洞的主要荷载,内水压力或外水压力直接作用在衬砌管片上,管片衬砌的受力特性对于工程安全稳定运行具有重要意义。平行四边形管片作为一种新型管片,在错缝拼装方式下应用具有较大优势,但尚未对其结构受力特性进行研究。依托某市供水隧洞工程实际,建立新型平行四边形管片衬砌的三维有限元数值模型,研究其在运行期和检修期的受力特性。结果表明,运行期内水压力作用下,衬砌各管片单独受力,管片间变形与拉应力不连续,以环向螺栓连接,各接缝开度呈现靠近衬砌内侧小、外侧大的特点;检修期外水压力作用下,衬砌管片受力整体性较好,管片间环向变形与压应力连续,环向螺栓压应力偏小,各接缝压力靠近衬砌内侧较大、外侧较小。同时,根据衬砌与豆砾石间摩擦系数讨论结果可看出,运行期衬砌朝外变形,管片与豆砾石间呈压紧趋势,其受力变形受摩擦系数的影响较为敏感,检修期管片与豆砾石间呈分离趋势,管片受力特征基本不受摩擦系数的影响。     

External overpressure of vented hydrogen-air explosion in the tube

Vented explosion experiments involving hydrogen-air mixtures are performed in a 2 m-long cylindrical tube under the influences of the hydrogen concentration and vent burst pressure. Photos of the external flame shot by a high-speed camera show that the jet flame was expelled outside the vessel, and the relation between the flame propagation and external overpressure is summarized. The internal peak overpressure increases and then decreases with increasing hydrogen concentration. In contrast, the external peak overpressure exhibits the opposite correlation in comparison with the internal peak overpressure. The variations in the pressure peaks of the internal pressure curves are also discussed. When the hydrogen concentration is lower than 40 vol %, the second pressure peak plays a more dominant role than the other pressure peaks. However, when the hydrogen concentration is higher than 40 vol %, the third pressure peak becomes more dominant.     

含张开单裂隙砂岩破裂过程围压效应的数值模拟

为研究不同倾角裂隙砂岩试样在压缩过程中的围压效应,以室内单轴压缩试验结果标定岩体细观参数,采用改进刚体弹簧元法对不同倾角裂隙试样在不同围压下的破坏过程进行模拟。基于模拟结果,研究了围压对岩样强度、破坏模式及微裂纹发育特征的影响。结果表明,裂隙砂岩试样在压缩过程中具有明显的围压效应,相同裂隙倾角试样,其峰值强度、残余强度、弹性模量和变形模量均表现出随围压增加而增加的规律;不同围压作用下,不同倾角裂隙试样内部微裂纹演化规律相似,且其最终破坏形态均表现出以剪切破坏为主的破裂方式。     

Hydrogen: Its Effect in Environmental Protection

Presented here is a parametic study of the relationships that govern the operation of a bellows heat pipe for use in the cooling of electronic components. The defining equations are combined with the proper similarity relations to develop a mathematical model that can be used to describe the operational characteristics and performance limitations of such a heat pipe. The paper starts with a review of the recent experimental work done in the area of bellows heat pipes, formulates the governing equations, and proceeds through the development of a computer model. Preliminary testing of the computer model was carried out using experimental data obtained from previous investigations, to ensure that it accurately reflected the heat pipe performance. Once the model had been verified, it was used to develop an optimum design for a small bellows heat pipe.     

冷凝器不锈钢波纹管导波检测技术的研究

为了实现对冷凝器不锈钢波纹管的主动健康监测,采用附着在结构上的压电陶瓷晶片以及套在结构表面的电磁声换能器激励接收导波模态,优化各种参数以用于缺陷的识别和评估。试验选取经Hanning窗调制的正弦脉冲信号在波纹管中激励中心频率240kHz的纵向超声导波L(0,2)模态,用于波纹管中人工缺陷的检测,并分析了L(0,2)模态对不同类型缺陷的敏感程度。试验结果表明,利用压电陶瓷晶片和电磁声传感器激励接收频率为240kHz的L(0,2)模态可以识别波纹管中的裂纹缺陷。     

Experimental study of a bellows‐type reciprocating‐mechanism driven heat loop

The reciprocating‐mechanism driven heat loop (RMDHL) is a novel two‐phase heat transfer device that could find many important applications in energy systems and electronic cooling. However, the previous RMDHL is based on a solenoid driver that may have difficulty in handling a large amount of heat transfer rate over a long distance due to the driver's inability to provide a large displacement volume. To overcome this difficulty, a bellows‐type RMDHL demonstration model has been designed, fabricated, and tested. The results show that the bellows‐type RMDHL has successfully overcome the weakness of the solenoid driver and may be employed for applications involving large heat transfer rates and over a large surface area. Another advantage of the bellows‐type RMDHL is its potential to maintain an exceedingly uniform temperature over a relatively large surface. Additionally, the power consumption of the bellows driver was less than 5 W when the power input to the cold plate was up to 600 W, resulting in the ratio of driver's power input to the heat input to the cold plate being less than 1%, which represents a tenfold improvement over the solenoid‐based RMDHL. All these technical improvements over the previous RMDHL have demonstrated significant progresses towards a refined RMDHL system for energy and electronics cooling applications. Copyright © 2012 John Wiley & Sons, Ltd.     

Thermodynamic characteristic in a cryogenic storage tank under an intermittent sloshing excitation

A numerical calculation model is developed to study the coupled thermal dynamic performance in a cryogenic fuel tank under an intermittent sloshing excitation. Both external heat inputs and the intermittent excitation are realized by User-defined functions. The volume of fluid method is adopted to simulate fluid sloshing, coupled with the mesh motion treatment. Validated against related fluid sloshing experiments, the numerical model was turned out to be acceptable on fluid sloshing prediction. Cooled by subcooled liquid, vapor is always in condensation. The middle vapor pressure test point suffers less from the intermittent excitation and has a linear pressure decrease profile, while the middle liquid pressure test point has fluctuating variations. For vapor and interface temperature monitors, obvious temperature fluctuations appear in the second holding period. While for liquid test points, the temperature profiles experience intensive fluctuations during sloshing periods and stable temperature variation during holding periods. Due to the holding period of external excitation, the tank pressure reduction in intermittent sloshing case is less than that in continuous sloshing case. That is to say the tank pressure decrease rate could be adjusted by proper intermittent excitation. This work is significant to deeply understand fluid sloshing phenomenon under some irregular external excitations in fuel storage tanks.