Model of the Zero Drift of a Bellows Vacuum Gauge with an LC Oscillator and the Anomaly of the Axial Thermal Expansion of the Bellows

We have derived an equation of thermal perturbations by deduction from a physical model for deformation vacuum gauges with bellows as the elastic element. The model can be used to analyze the temperature zero drift of micropressure gauges, to divide the zero drift into components with regard to particular effects, and to eliminate or to diminish those effects. A zero drift of 0.1 Pa/K was obtained for a micropressure gauge rated at up to 1000 Pa (0.01 %/K). We have found that the temperature zero drift occurs mainly because with rising temperature the bellows expands to an anomalously large extent (1.5 to 2 times) along its axis as compared to the expansion of the alloy used to make the bellows.Translated from Izmeritel’naya Tekhnika, No.3, pp. 27–31, March, 2005.     

Stress corrosion cracking in 316L stainless steel bellows of a pressure safety valve

There were three consecutive occurrences of bellows failure in a particular pressure safety valve (PSV) of a petroleum refinery within a time span of one week. The bellows were made of 316L grade austenitic stainless steel, and the PSV was mounted on one of the vessels of vacuum gas oil service in a hydrocracker unit. Metallurgical analysis of the failed bellows revealed that the failure had occurred by stress corrosion cracking (SCC). It was found that the SCC was promoted in the bellows due to the presence of high amount of chloride ions in the operating environment. Studies confirmed that SCC had initiated from the outer surface of the bellows and propagated inwards, resulting in leakage of hydrocarbon from the PSV. The source of chlorine in the environment was identified. It was discovered that SCC in the bellows was caused due to a previous failure in the heavy polynuclear aromatics (HPNA) absorption bed located upstream the process flow line. This failure was due to the presence of high concentrations of chlorine in the granulated activated carbon that was used in the HPNA absorption bed. During the repair of the HPNA bed, there was deposition of carbon soot on the body of the PSV. This carbon soot was the source of chloride ions for SCC to occur in the bellows. Generally, in chloride SCC, crack propagation in 316L SS takes place by transgranular mode. In the present case, however, the crack propagation was predominantly by intergranular mode. The metallurgical factors responsible for this change in micro-mechanism of crack propagation during SCC have been discussed.     

基于瞬态动力学分析的波纹管结构优化

目的 优化波纹管结构尺寸,最大程度地减小波纹管的应力集中,提高波纹管的疲劳寿命。方法 利用ANSYS Workbench对真空灭弧室用波纹管进行参数化建模,对其耦合速度压力复杂工况进行瞬态动力学分析,借助DOE(DesignofExperiment)技术对波纹管关键几何参数进行单目标优化设计,对优化结果进行强度校核和疲劳寿命计算。结果 优化结果符合设计要求,波纹管在耦合速度压力复杂工况下满足强度的同时,最大等效应力减小了28.8%,疲劳寿命由3 064次提高到32 260次。结论 优化后的结构有效减小了波纹管危险部位的应力集中,疲劳寿命得到提高。     

Metallurgical investigation on stainless steel bellows used in satellite launch vehicle

Bellows made of austenitic stainless steel AISI 304 grade are being used as conduit for liquid fuel and oxidizer in propellant tank of satellite launch vehicle. These bellows encountered frequent leakage problems. Leakage locations were found to be along the fusion line of ring to ply weld. In many of such failures, synergistic effect of chloride ions and thermal stresses from welding was the cause identified. Detailed metallurgical characterization of bellows with different weld parameters have been carried out, which served as an efficient tool for qualification of the processing of bellows. This paper highlights various metallurgical features observed in stainless steel bellows during process qualification programme and their impact on the performance.     

Regeneration of peripheral nerves by bioabsorbable polymer tubes with fibrin gel

We developed two types of nerve conduits, straight tubes, and bellows tubes, for peripheral nerve regeneration with bioabsorbable polymer membranes. Mechanical properties of these straight and bellows tubes were analyzed. 30 straight tubes and 30 bellows tubes were implanted to a nerve defect made in a rat sciatic nerve and the nerve regeneration in the tube was investigated. A half of these tubes were utilized alone and the others were filled with fibrin gel made from coagulated plasma and implanted. Bellows tubes were superior in mechanical characteristics to straight tubes and the inner cavities of the bellows tubes were suitably maintained after implantation. At 4 weeks after operations, remyelinations were observed in the regenerated tissue at the location of the middle parts of the tubes filled with fibrin gel whereas no remyelinations in the tubes without fibrin gel. The use of fibrin gel as filling materials within the tubes significantly enhanced the nerve regeneration. The fibrin gel might be soft nanomaterials significantly enhance the regeneration of the peripheral nerves. We concluded that the developed bioabsorbable bellows tubes filled with fibrin gel were effective for peripheral nerve regeneration.     

基于波纹管简化模型的排气系统模态分析

为了探究汽车排气系统波纹管简化模型的合理性,对简化模型进行数值分析和理论研究.首先,以某重型卡车排气系统为研究对象建立有限元模型,将波纹管简化为零长度的CBUSH单元,对系统自由模态进行分析;其次,用波纹管将排气系统分隔开简化为二自由度模型进行理论计算;最后,综合对比分析表明,第7阶和第8阶模态频率接近于零,主要原因是绕X,Z轴刚度较小,验证了波纹管在该方向的隔振效果良好.理论方法与数值计算具有普遍性和工程指导意义.     

波纹管动力学分析研究进展

从理论模型、试验研究及有限元分析等方面回顾了波纹管固有频率、阻尼特性及机械阻抗等动力学参数的研究进展,总结了波纹管动力学响应的有限元分析方法及试验方法,分析了流体诱导振动的研究现状,展望了波纹管动力学研究亟待解决的问题.     

大口径铝合金波纹管电磁胀形数值模拟

目的研究大口径铝合金波纹管电磁成形过程及工艺参数对成形效果的影响规律。方法针对波纹管现有制造工艺——压弯和焊接复合成形存在压痕严重、焊缝多和可靠性不高等问题,提出采用电磁成形波纹管的方法,并基于ANSYS建立了波纹管电磁胀形的三维有限元分析模型。结果揭示了波纹管电磁胀形过程中的应力应变分布规律,发现波纹区域和过渡圆角区域是应力和应变集中区。采用单因素实验方法,获得了放电电压和线圈匝数对成形质量的影响规律。结论在波纹管电磁胀形过程中,波纹区域的应力和应变均呈圆环带状分布,波纹管的壁厚在波纹的波峰处达到最小,最大减薄率为10.67%。放电电压和线圈匝数都存在一个最佳值。放电电压过小时,成形不足,放电电压过大时,工件高速碰撞模具,引起较大反弹,导致最终贴模性较差;线圈匝数也对成形质量有一定的影响,在本次模拟实验中,11匝线圈作用下的工件贴模性最佳。     

U型波纹管的扭转振动固有频率的计算

采用等效的薄壁圆管模型来分析U型波纹管的扭转振动固有频率,为此要确定U型波纹管的等效半径和扭转刚度。等效半径采用两种计算方法。扭转刚度的计算即采用了钱伟长关于旋转壳的扭转刚度积分公式,也采用了等效的圆管模型方法,由此得到的相应的U型波纹管扭转固有频率的计算方法分别称为积分法和简化法。没有关于波纹管扭转固有频率的实验见诸文献。采用有限元法来验证上述计算方法,取得了很好的一致。积分法更为精确,简化法更适于工程计算。     

BEPCⅡ真空内扭摆磁铁波纹管RF屏蔽结构的改进

BEPCⅡ真空内扭摆磁铁的波纹管在电子束流的高流强运行中发生了损伤和真空泄漏。对损伤原因进行了分析,怀疑是波纹管RF屏蔽结构的弹簧片与接触套之间存在间隙,导致了高次模泄漏。如果波纹管没有压缩到设计的安装长度,弹簧片与接触套之间可能存在1 mm的间隙。利用MAFIA软件对这种情况下的尾场和阻抗进行计算,结果表明尾场收敛很慢,最大的尾场振幅为0.08 V/pC,阻抗在1.32 GHz存在窄带的共振峰。在该间隙处会发生高次模泄漏,有必要对屏蔽结构加以改进。对屏蔽结构的弹簧接触方式做了改进,将弹簧片改为环形的弹簧丝,最大调节量由4.0 mm提高到7.9 mm,且杜绝了间隙。300~500 mA的束流实验表明,屏蔽结构改进后,波纹管附近的真空度从2.66×10-7Pa提高到6.65×10-8Pa,波纹管的温度从40℃以上降低到25℃以下。     

城镇供热管网波纹管腐蚀失效及预防措施研究现状

随着波纹管补偿器在热力工程中的广泛应用,作为核心元件的波纹管的腐蚀失效也受到关注.结合部分波纹管失效案例,综述了城镇供热管网不锈钢波纹管常见的腐蚀失效形式及影响因素,并从不同角度总结了对供热波纹管腐蚀失效的预防措施.最后指出了目前对波纹管腐蚀失效研究的局限性与不足,以期对未来波纹管的腐蚀性能研究方向提供思路和参考.     

U形波纹管疲劳寿命有限元分析

运用ANSYS有限元软件对波纹管进行应力分析,得出波纹管应力集中位置,借助Fatigue tool模块,采用E—N方法进行疲劳寿命分析,得到波纹管的疲劳寿命分布。有限元分析结果与经验公式及试验结果的比较,得出有限元模拟结果比经验公式更加接近试验结果。最后指出了在进行波纹管疲劳寿命有限元分析过程中需要注意的问题。     

小波包能量谱和BP神经网络在波纹管压浆超声检测中的应用

针对小波分析在信号处理的局限性,将小波包分析和反向传播(Back Propagation,BP)神经网络相结合,提出一种基于小波包能量谱和BP神经网络的波纹管压浆超声检测方法。采用超声检测方法接收波纹管模型的回波信号,以小波包分解后各子频带的能量作为检测特征,当波纹管内部出现脱落时,检测特征会发生变化,最后将特征输入BP神经网络中进行分类识别。试验结果表明,该方法能够理想地实现波纹管内部缺陷的诊断,可为波纹管超声检测提供一定的技术支持。     

Jet expansion module for liquid-sampled GC-discharge ionization detection of liquefied gases

A rugged jet expansion module was designed, built, and utilized to sample liquefied gas for gas chromatography-discharge ionization detector (GC-DID) analysis. The module is inserted at an intermediate stage between a higher pressure sample cylinder and lower pressure gas injection manifold. The title jet module permits selection of liquid-phase or vapor-phase sampling by setting the valve-cylinder orientation up or down (relative to gravity). It consists of a four-way stainless steel cross, plus the following components connected to pipe thread ports: (1) mechanical pressure gauge, -15 to +30 psig; (2) threaded nut with 0.010-in. jet orifice (connect to sample cylinder valve); (3) bellows valve (connect to GC manifold); (4) bellows valve (connect to expansion cylinder). Making use of the jet module, measurement of air concentration in [15N]ammonia and sulfur hexafluoride (single-component) samples was found to be significantly lower in the liquid phase by GC-DID. This compact apparatus enables phase-selective sampling, reduces primary manifold contamination, and improves operator safety.     

A new 48 d.o.f. quadrilateral shell element with variable-order polynomial and rational B-spline geometries with rigid body modes

A 48 degrees-of-freedom (d.o.f.) quadrilateral thin elastic shell finite element using variable-order polynomial functions, B-spline functions and rational B-spline functions to model the shell surface is developed. This development may allow the stiffness formulation of the shell element to be linked to the geometry data bases created by computer aided design systems. The displacement functions are that of bicubic Hermitian polynomials. The displacement functions and d.o.f. are expressed and investigated in both the curvilinear and Cartesian forms. The cuivilinear form is simpler and can provide the proper solution for a certain class of shell problems. For certain highly curved shells such as bellows, however, the curvilinear form fails to properly model some rigid body modes even with either the explicit inclusion of rigid body terms or the high order displacement functions. It is suggested in this study that such difficulty can be circumvented and the rigid body modes can be properly included if a Cartesian form is used for displacement functions. The strain–displacement equations are expressed in curvilinear co-ordinates. Thus, the Cartesian displacement functions require a transformation to curvilinear displacement at each numerical integration point. Examples include a pinched cylinder, a translational shell under central load, a uniformly loaded hypar shell, a pressurized ovel shell, a semi-toroidal bellows and a U-shaped bellows. For the first four examples, geometric modellings consist of polynomials of second-order (subparametric), third-order (isoparametric), and fourth and fifth-order (both superparametric) as well as B-spline functions of fourth- and fifth-order. The geometries of the pinched cylinder, the semi-toroidal bellows, and the U-shaped bellows were modelled exactly using rational B-spline functions. All the results obtained are in good agreement with alternative existing solutions.     

金属波纹管补偿器的应力腐蚀开裂分析

采用宏观及微观断口分析、金相检验与化学成分检测等方法,对某铬一镍奥氏体不锈钢波纹管补偿器的腐蚀开裂失效原因进行了分析。结果表明：由于该铬一镍奥氏体不锈钢波纹管在氯离子含量超标的环境中服役,并承受来自于波纹管自身加工变形过程中形成的残余应力、工作应力以及装配应力,最终导致波纹管补偿器发生了由表及里的应力腐蚀开裂。     

工况环境下振动对波纹管疲劳性能的影响

研究了热网波纹管在工作应力、工作介质及工作温度等工况环境下系统振动对其疲劳性能的影响，采用显微组织分析、硬度分析、SEM分析等手段对波纹管的失效情况进行了分析。结果表明：波纹管的疲劳裂纹从内、外表面两侧起裂，并向材料中心方向扩展至尖端相近时，发生瞬断，裂纹相接处呈韧性断裂。工况环境下振动对波纹管残余应力起到了一定的消除作用，并显著提升了波纹管的抗疲劳性能。     

Failure analysis of an AM 350 steel bellows

The failure of an AM 350 steel bellows, which was to be used in the control rod drive mechanism (CRDM) of the fast breeder test reactor (FBTR), was noticed during helium leak testing. The leak test was carried out before performance testing in a test rig. Visual examination of the leak area did not indicate any obvious defect. Stereo microscopy and optical microscopy indicated the presence of pits. A few of these pits had propagated through the thickness. EDAX of the corrosion products revealed the presence of chlorides. The exposure of the bellows to a marine atmosphere during a storage period of 13 years was suspected to have caused the pitting.     

Simulation of a muscle joint directly or indirectly driven by pneumatic pressure

Summary A novel robotic joint is proposed. A rubber bellows muscle actuator with pliability is driven by a pneumatic pressure or tandem compound system consisting of pneumatics and hydraulics. The joints can be used as direct driving in a smart manipulator. A mechanical joint model driven by the muscle has been built, and an equation to calculate the volume of the bellows in correlation with the angle of its compliant bend is obtained. Finally a simple dynamic model between the angular displacement of the joint and time variable is created and a simulation of the dynamics is given based on an example.     

多层波纹管接触分析及稳定性屈曲分析

通过建立三层四波多层波纹管平面轴对称模型和三维实体模型,探讨了波纹管在内压载荷下所涉及到的层间接触问题和稳定性屈曲问题.针对多层结构接触问题所涉及到的摩擦系数、接触刚度和层间间隙等参数的取值进行了模拟试验对比,最后对非线性屈曲分析的初始缺陷和弹塑性极限分析所需施加的载荷值进行了描述,目的在于通过对多层波纹管有限元分析的...