Failure of a braided stainless steel hose connector

Flexible water hoses are used as line connections from water supply plumbing to fixtures and appliances. The design configuration of these hoses varies; however, a common design involves an elastomeric liner surrounded by an outer reinforcement of braided stainless steel wire. These hoses are subject to rupture in service, traceable to the fracture of the braided wire reinforcement. The mechanism of failure involves localized corrosion of the stainless steel wire braid, a condition arising from the presence of water exterior to the hose. The following case of a ruptured water hose demonstrates this condition.     

Flexible Water Hose Failures: A Case Study and General Design Considerations

Flexible water hoses (or flexible hose connectors) have become commonplace in recent years and provide a low-cost and convenient alternative to rigid pipe. Unfortunately, inadequate designs, particularly with regard to the selection of materials and material parameters, have made some hoses prone to failure. Such failures are often initiated by incidental exposure to corrosive substances commonly found in homes (including chlorides in tap water) that attack and corrode the stainless steel metal braid. A failure of the braid then leads to a rupture of the water-carrying tube. We evaluate the design considerations pertinent to flexible water hose failures and consider a recent failure scenario that illustrates some key points.     

套筒连接的预制拼装桥墩抗震性能研究

以灌浆套筒预埋于墩身的预制拼装桥墩为研究对象,分析了地震作用下此类桥墩墩身与承台接缝处的受力机理和套筒预埋于塑性铰区对桥墩整体受力性能的影响,进行了灌浆套筒预埋于墩身的预制拼装桥墩模型拟静力试验。在此基础上,采用数值模拟分析方法,建立有限元模型,比较了采用灌浆套筒连接的预制拼装桥墩与整体现浇桥墩的性能差异,以及不同直径的灌浆套筒对此类预制拼装桥墩抗震性能的影响。研究表明:采用墩身预埋灌浆套筒连接的预制拼装桥墩,因套筒刚度大,易在墩身套筒连接段形成刚性区域,发生墩身曲率重分布现象,导致墩底接缝处曲率增大,应变集中。此外,灌浆套筒埋置于墩身的预制拼装桥墩与整体现浇桥墩相比,等效塑性铰高度减小,位移承载能力降低,且灌浆套筒直径越大、长度越长,桥墩接缝处应变集中越明显,与整体现浇桥墩性能差异越大,导致桥墩最终破坏形式由传统的塑性铰区域混凝土破坏转变为墩底接缝处钢筋拉断。     

Creep rupture of thermomechanically treated Mo-5%W alloy

The effect of thermomechanical treatment such as high temperature swaging on the creep failure mechanism of the Mo-5%W alloy was investigated. It was found that heavily swaged specimens fail after a relatively large amount of creep deformation, while slightly swaged specimens fail after a few percent of strain. In this paper the above-mentioned behaviour is explained on the basis of a semiquantitative model.     

Failure analysis of flexible metal hose at compressor discharge

Flexible hoses are sometimes placed at compressor discharge to minimize the effect of vibrations on piping and vessels. Doing well for this purpose, these elements can suffer dynamic loads from gas pulsation and fail. The root cause of the failure of a flexible connection at the discharge of an oil distillery propane alternating compressor is investigated. The connection is a 150 mm stainless steel corrugated metal hose with an external braid. The failure took place by overload of the braid, after wear of the wires. The fractures in the wires were consequence of fatigue crack propagation in previously worn areas. It was found that the flexible connection was under a larger working pressure than the maximum allowable as defined by the manufacturer. The failed flexible had thinner wires and different braid design than those previously used by the user. Recommendations include procedures to verify dimensions previous to assembly and to increase the inspection frequency of these elements, as well as to verify vibration levels of the connected machines. An elastomer material placed between corrugated and braid would diminish the rate of wear caused by vibrations.     

燃气用具连接用不锈钢波纹软管长度测量方法

针对CJ/T 197-2010《燃气用具连接用不锈钢波纹软管》标准中软管长度无相关测量方法,通过对燃气软管相关标准的比对及软管相关标准调查研究,比对长度测量方法的异同,及测量方法对长度测量结果的影响等因素,及对目前常见接头类型的收集和分析,及燃气用具连接用不锈钢波纹软管等燃气软管应用环境的分析,提出燃气用具连接用不锈钢波纹软管等燃气软管统一的长度的测量建议,为相关燃气标准的长度测量提供参考。     

Wire-free constructions in suction hoses

Rubber Suction/Delivery hoses can be made without the use of the traditional steel helix; using instead a sandwich of rubber between two layers of synthetic macrofilament yarn, arranged circumferentially in the hose body. This construction resists vacuum and pressure, recovers rapidly after crushing, may be cut to length as required and fitted with re-usable flanges. These advantages make for great facility of hose supply and economy in the handling of abrasive solids and slurries.     

管道三层热缩套(带)现场补口应注意的问题

为解决三层聚乙烯热缩套(带)管道补口的质量问题,通过现场考察,总结出4类主要质量问题和4方面的现场条件问题,提出了与操作和检查有关的改进意见以及与套(带)选型选材有关的建议.结果表明,补口施工中的6个质量控制点是进行科学的质量检查和制定合理的质量标准;根据施工环境选择用套还是用带(定向钻工程中不应用带);套(带)收缩率不宜太高和收缩速度不宜太快;在保证底层质量的条件下允许有较小的空鼓或气泡;安装后边缘应有可见厚度的胶条;使用具有感温颜色显示功能的套(带),才能凭视觉控制最重要的温度指标.     

船用三层组合外套液压联轴器最优分层分析

液压联轴器外套采用多层筒组合式外套可提高液压联轴器的弹性极限承载能力．文中对液压联轴器不同材料双层组合式外套和同种材料3层组合式外套进行了分析，确定了双层和3层外套分层界面的最佳半径．结果表明，3层外套的弹性极限承载能力比单层外套的弹性极限承载能力提高了31．4％；3层外套的弹性极限承载能力比双层外套的弹性极限承载能力提高了7．4％．     

Influence of swaging on hydrogen charged tensile fracture of a 12 wt-%Cr steel

Abstract

The 12 wt-%Cr secondary hardening steel considered in this work is being evaluated for use in the first wall of fusion reactors. As the service temperature can approach 500°C, the microstructure of greatest interest has been a quenched and tempered structure obtained by tempering at 750°C after air cooling from the austenitizing temperature of 1050°C. This structure is susceptible to grain boundary failure whether internal hydrogen has been introduced by cathodic charging or not. In the uncharged condition failure is ductile, but follows prior austenite grain boundaries. Hydrogen charging results in a severe loss of ductility, and tensile fractures which are 30% brittle intergranular. This susceptibility to grain boundary fracture has been attributed both to phosphorus segregation to these grain boundaries and to a nearly continuous array of grain boundary carbides. This tendency for grain boundary fracture can be eliminated and the embrittlement associated with the introduction of internal hydrogen greatly reduced by swaging and subsequently retempering the quenched, and tempered microstructure. The improved properties of the swaged and retempered conditions are attributed to the effects of swaging on the prior austenite grain boundary structure and the orientation of the grain boundaries with respect to the tensile axis.

MST/376     

Selection and experimental evaluation of low-cost porous materials for regenerator applications in thermoacoustic engines

This paper aims at evaluating three selected low-cost porous materials from the point of view of their suitability as regenerator materials in the design of thermoacoustic travelling-wave engines. The materials tested include: a cellular ceramic substrate with regular square channels; steel “scourers”; and stainless steel “wool”. Comparisons are made against a widely used regenerator material: stainless steel woven wire mesh screen. For meaningful comparisons, the materials are selected to have similar hydraulic radii. One set of regenerators was designed around the hydraulic radius of 200 μm. This included the ceramic substrate, steel “scourers”, stainless steel “wool” and stacked wire screens (as a reference). This set was complemented by steel “scourers” and stacked wire screens (as a reference) with hydraulic radii of 120 μm. Therefore six regenerators were produced to carry out the testing. Initial tests were made in a steady air flow to estimate their relative pressure drop due to viscous dissipation. Subsequently, they were installed in a looped-tube travelling-wave thermoacoustic engine to test their relative performance. Testing included the onset temperature difference, the maximum pressure amplitude generated and the acoustic power output as a function of mean pressure between 0 and 10 bar above atmospheric. It appears that the performance of regenerators made out of “scourers” and steel “wool” is much worse than their mesh-screen counterparts of the same hydraulic radius. However cellular ceramics may offer an alternative to traditional regenerator materials to reduce the overall system costs. Detailed discussions are provided.     

Fatigue behaviour of commercially pure aluminium processed by rotary swaging

Fatigue strength of ultrafine-grained commercially pure aluminium (Al 1050) produced by severe plastic deformation (rotary swaging) was investigated. Fatigue tests were carried out on smooth and notched specimens. Results show improved static and fatigue strength of the rotary swaging processed material. However, the processed material was highly notch sensitive due to low work hardening capability, low ductility as well as low uniform strain. It was found that post-deformation annealing above recrystallization temperature can additionally enhance the work hardening capability and the ductility of the swaged material, which led to marked reduction in fatigue notch sensitivity. At the same time, this reduction is accompanied with pronounced loss in strength. Fatigue notch sensitivity of commercially pure aluminium can be good correlated to the work hardening capability and ductility. This behaviour was discussed in details based on microstructure and mechanical properties study.     

Role of the material of contacting parts in the resistance of steel to corrosion-fatigue fracture

The corrosion-fatigue strength of steel specimens with press-fitted sleeves was studied. It was established that the reduction in the corrosion-fatigue strength of steel does not depend on the sleeve material.     

被动围压条件下岩石材料冲击压缩试验研究

为研究煤矿岩石材料被动围压条件下动态力学性能和变形破坏规律,利用Ø50mm变截面分离式Hopkinson压杆(SHPB)试验装置,对45#钢质套筒环向约束状态下煤矿岩石试件进行了不同加载速率冲击压缩试验。试验结果表明：被动围压条件下SHPB试验中,岩石试件的材料延性和抗破坏能力均得到增强,试件轴向应力是采用同种加载条件无围压SHPB试验时的1.2倍,破坏应变比无围压SHPB试验提高2～3倍,且径向应力随轴向应变增大总体呈上升趋势,试件破坏为压剪破坏模式,与无围压SHPB试验有所不同。     

关于CJ/T 197-2010《燃气用具连接用不锈钢波纹软管》标准中螺纹要求的解析

针对CJ/T 197-2010《燃气用具连接用不锈钢波纹软管》标准中GB/T 7306. 1-2000和GB/T 7306. 2-2000与GB/T 7307-2001管螺纹标准之间异同点进行辩析,为使用者提供参考。针对燃气用具连接用不锈钢波纹软管对螺纹要求,及其与螺纹标准的对应关系进行解析,提出标准中存在的问题,及燃气用具连接用不锈钢波纹软管标准关于螺纹要求修改的意见和建议,完善燃气用具连接用不锈钢波纹软管标准,利于燃气用具连接用不锈钢波纹软管标准的推广使用。     

空间结构压杆的套管加固失效模式试验研究

空间结构压杆失稳是结构失效的重要原因之一。利用套管加固空间结构压杆以抑制压杆屈曲,增加构件的极限承载能力和延性。通过对不同壁厚、套管与内压杆间隙和内压杆外伸段长度的12根试件进行轴压试验,得到加固前后试件的极限承载能力、破坏模式和延性变化。加固后试件的极限承载能力最大提高了147%,且外套管壁厚越大,内压杆外伸段越短,承载力越高;内压杆与外套管间隙越大,承载力略有下降。加固试验中构件的破坏模式由加固前的整体屈曲失稳变化为加固后的整体失稳、内压杆端部外伸段失稳和两种耦合失稳,且壁厚越小,易发生整体失稳,外伸段越长,易发生内压杆端部失稳,间隙对失稳形态影响不明显。此外,加固后试件延性均大于未经加固内压杆,经过合理设计延性指标能够增加一倍以上。     

Failure loads for model adhesive joints subjected to tension,compression or torsion

The Griffith fracture criterion has been applied to model adhesive joints subjected to tension, compression or torsion. Two model joints are considered: a rigid cylinder partly embedded in and bonded to an elastic cylinder (termed rod joint here), and an elastic cylinder inserted partway into, and bonded to, a rigid tube (termed sleeve joint here). Both types of joint have been constructed, using vulcanized rubber cylinders bonded to aluminium rods and sleeves.Measurements have been made of the failure loads under tension, compression and torsional loading. They were found to be in satisfactory agreement with the theoretical predictions except, in some instances, for rod joints subjected to tension or torsional loading when the failure loads were as much as three times the predicted values. This discrepancy is attributed to friction between the partially-detached rubber cylinder and the embedded rod, enhanced to a great extent by the tendency of the rubber cylinder to shrink in radius on stretching or twisting. A theoretical analysis of the effect of friction is presented. It predicts increasingly large pull-out forces or torques, as the depth of embedment increases, until frictional seizure occurs. Experimentally, frictional effects were limited by applying an internal gas pressure to the region being detached. All of the failure loads were then found to be in satisfactory agreement with the original theory, ignoring frictional effects. Thus, a simple fracture energy criterion is shown to govern the failure of adhesive joints under complex loading conditions, with or without friction acting at the interface.On leave from the Rubber Research Institute of Malaysia, Kuala Lumpur, Malaysia.     

On stresses in reinforced high-pressure hoses

Summary This paper bears upon flexible high-pressure hoses which consist of a rubber cylinder reinforced by one or more steel braids. Each of the latter is made by two families of thin steel wires, wound along helical lines. Due to the fact that they are interwoven, they obstruct each others motion to some extent. The effect of it on the stress distribution in the hose is calculated approximately.With 6 Figures     

钢筋套筒挤压连接的预制RC柱抗震性能试验研究

为研究纵筋套筒挤压连接的预制柱抗震性能,完成了7个配箍特征值0.15~0.187、轴压比0.65~0.80、截面尺寸500 mm×500 mm的钢筋混凝土预制柱试件及1个用于对比的现浇柱试件的拟静力试验。结果表明,套筒挤压连接能够有效传递钢筋的拉、压力,预制柱试件与现浇柱试件的破坏过程、破坏形态基本相同,预制柱试件的水平力-位移滞回曲线饱满,偏心受压承载力试验值为计算值的1.26倍~1.42倍,极限位移角为1/42~1/26,抗震性能满足规范要求。套筒挤压连接可用于抗震设计的钢筋混凝土柱的纵向钢筋连接。     

Joining of CP-Ti to 304 stainless steel using friction stir welding technique

Friction stir welding parameters were adjusted in order to achieve defect-free dissimilar lap joint of CP-Ti to 304 stainless steel. Titanium as a softer material was selected to be on the lap top side. The joint stir zone was found to be consisted of two main regions; the dominant fine dynamically re-crystallized titanium grains at the upper region and a minor composite-type microstructure of fragments of 304 stainless steel in a matrix of fine dynamically re-crystallized titanium grains in the lower region. The stir zone was separated from the 304 stainless steel side by an interface layer of TiFe-based crystal structure. Joint shear strength was measured; a maximum failure load of ∼73% of that of CP-Ti was achieved. This was associated with the occurrence of fracture at the joint intermetallic-based interface. The failure load value of the fabricated joints is related to the thickness of the intermetallic interface.