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1.
A flange-to-pipe weldment in a seawater-intake-return-line suffered from cracking on its flange portion after in service for 4 months. The flange was fabricated from S32750 super duplex stainless steel. The cracked flange was investigated by visual inspection and fractographic examination on the crack surface, metallographic examination, hardness measurement, and chemical composition analysis of the flange-to-pipe weldment. The results of laboratory analysis showed that the flange had cracked in a brittle manner resulting from the presence of large amount of sigma phase in the flange material. Formation of such brittle second phase precipitates in the flange material was due to improper heat treatment.  相似文献   

2.
朱奇  李国强 《工程力学》2014,31(9):51-56
根据波纹腹板梁翼缘局部失稳的特性提出波纹腹板H型钢梁翼缘局部失稳的理论计算模型,指出波纹腹板梁翼缘失稳相当于两加载边简支,一非加载边弹性转动约束的弹性板。由理论推导得到了翼缘局部弹性屈曲应力计算公式,利用有限元分析验证了该理论模型的有效性。同时探讨了受拉翼缘、梁的长度以及腹板参数变化对受压翼缘局部失稳的影响,最后根据有限元计算结果给出了可供工程设计参考的翼缘宽厚比限值计算公式。  相似文献   

3.
合肥先进光源(HALF)计划建成为低能区衍射极限储存环光源,采用多弯铁消色散磁聚焦结构(MBA lattice)。相比于三代光源,MBA lattice使得超高真空系统布局更紧凑,磁铁间常用ConFlat法兰安装困难。链式卡箍法兰轴向尺寸仅为链条宽度,远低于ConFlat法兰,且安装位置在直径方向,所需安装空间小,很好的满足了储存环真空系统对法兰部件提出的要求。但其技术被国外厂商垄断,且国内外相关研究文献较少。为了解决这些难题,设计并加工了一套小通径链式卡箍法兰组件,实验测量了法兰实现超高真空密封漏率的最小力矩,反复安装并更换垫圈8次以评估法兰寿命,研究了法兰组件在高温循环烘烤和低温液氮环境下的工作情况。测试结果表明所设计的法兰组件满足超高真空法兰的密封性能要求,对温度变化有较好的耐受性。通过受力分析和有限元方法,计算了法兰密封力和垫圈应力分布。  相似文献   

4.
针对内外法兰在拉弯荷载下的力学行为及承载力计算方法进行研究。基于平截面假定推导了半解析计算方法,并将该方法的计算结果与非线性有限元分析结果进行了比较验证。通过研究旋转轴、中性轴和承载力随轴向拉力变化,揭示了其在拉弯荷载下的受力特征。最后对一系列内外法兰的承载力进行计算和分析,总结了拉弯荷载下的设计计算方法。研究表明,内外法兰的抗弯承载力随拉力的增加而减少。与有限元分析相比,半解析计算方法具有足够的计算精度,更高的计算效率。论文所提出的设计计算方法较传统刚性法兰承载力计算理论更为准确和可靠,为内外法兰设计计算提供了依据。  相似文献   

5.
于春广  陶功权 《工程力学》2016,33(1):201-208,245
对某地铁线路的车轮磨耗进行了跟踪测试,掌握了该线路车轮磨耗特征;从轮轨关系研究的角度,分析了轮缘异常磨耗的原因;建立了地铁车辆动力学仿真模型,结合基于磨耗功的车轮磨耗评价方法,提出了车轮磨耗减缓措施。车轮磨耗测试结果表明,该线路地铁车轮以轮缘磨耗为主,且存在轮缘偏磨现象;轮缘缺乏润滑和线路小半径曲线分布不对称是造成轮缘磨耗过大和轮缘偏磨的主要原因。仿真结果表明,适当降低一系纵向刚度有利于减缓车轮磨耗;采用轮缘润滑或小半径曲线外轨轨侧涂油等方式降低摩擦系数,能显著降低轮缘和轨侧磨耗,摩擦系数每减小0.05,轮轨磨耗将降低约16.1%;载客量的大小对轮轨磨耗具有一定的影响,轴重每增加1 t,轮轨磨耗将增大约4.8%。针对所调查的地铁线路实际情况,建议对小半径曲线外轨采取涂油措施,以减小轮缘和轨侧磨耗;此外,定期对车辆进行掉头运行,以减缓轮缘偏磨现象。  相似文献   

6.
Optical fibre-based sensor systems are being used increasingly in civil engineering applications where structural integrity monitoring is of interest or concern. This paper reports on an optimisation scheme for an optical fibre-based sensor protection system designed to protect and enhance the strain-transfer characteristic when it is embedded in concrete. The sensor protection system consisted of a stainless steel tube with specified flange designs. Three flange designs were considered: disc, cone and inverted cone. Non-linear finite element analysis incorporating contact logic was performed to select and optimise the shape and dimensions of the flange. The analysis showed high stress concentrations in the vicinity of the flanges. However, this effect was localised and was not transmitted to the intended location of the sensor. The results showed that all three flange designs were effective but the 5 mm diameter disc-shaped flange gave the best results in terms of the magnitude and symmetry of the shear stress at the tube-concrete interface.  相似文献   

7.
A cracked reducer flange was analyzed for the cause of the failure. The flange was carefully cut to obtain samples for metallographic, X-ray, and scanning electron microscopy (SEM) Examinations. The examinations revealed that the introduction of chloride ions in the operational service led to pitting corrosion in the inner surface of the flange. Chloride ion inclusions were probably the result of chemical contaminations, i.e., cleaning chemicals’ contamination during shutdown of the operation. The introduction of corrosion pits caused unexpected load stress intensification and cracking of the flange. Consequently, stress corrosion cracking emanated from the pits under the influence of chloride attack and operational pressure. Then the cracks propagated in a transgranular manner, in the radial direction of the flange, until the final failure occurred.  相似文献   

8.
目的 研究大尺寸A356.2铝合金铸旋车轮内轮缘部位经涂装烘烤后力学性能的变化,以及取样部位的厚度对性能的影响。方法 通过对热处理毛坯、热处理毛坯过喷涂烘箱、热处理毛坯机加工后过喷涂烘箱A356.2铝合金铸旋车轮内轮缘部位力学性能进行对比分析。结果 分析表明,热处理毛坯经涂装烘箱烘烤后内轮缘部力学性能会发生变化,强度会有所提高,伸长率会有所下降;内轮缘部位力学性能变化幅度会受轮型状态或结构的影响,轮型内轮缘较薄、重量较小的轮子强度提高幅度较大,但伸长率下降幅度并不十分明显。结论 涂装烘烤对T5热处理的A356.2铝合金铸旋车轮内轮缘部位性能有影响;同时,内轮缘厚度、轮子重量对性能的变化也有影响。  相似文献   

9.
The functioning of multipart flange beam with riveted flanges, which are loaded with random external forces, is examined. Prior to elastic assembling the beam had random initial flexures of the flanges. We obtained relations for determination of probability of flange beam critical condition by the loss of flat form of flexure under the influence of random shear forces, which occur at the welding points between web plate and flanges of the beam. The examples for determination of probability of critical condition of flange beam under the influence of random initial flexures of the flanges are provided. __________ Translated from Problemy Prochnosti, No. 5, pp. 131 – 137, September – October, 2005.  相似文献   

10.
The applicability of carburising treatment of injector flange in a diesel engine was investigated. Initially, a carburized case structure made of low-carbon (0.23%) steel was approximately modelled by five sub-regions. Then, finite element stress analyses were performed using Abaqus CAE® software to determine performances of several models, which the thickness of five sub-regions were changed. Examining performances of case thicknesses with respect to load bearing capacity, minimum case thickness value was approximately determined to be 1 mm. After determining this superior case thickness configuration, for real service loading and boundary conditions, FE analyses were repeated to determine the cyclic stress components for a fatigue analysis. Based on the FE results, carburising treatment was applied and superior strength was determined for a case, in which the maximum hardness is 570 ± 20 Hv on surface and 290 ± 25 Hv at depth 1.05 mm from the surface with the condition that heat treatments before and after cold forming were properly applied. Experiments and FE analyses give almost similar results. The result showed that carburising treatment of injector flange provides 8% increase in static load bearing capability with 1 mm case thickness. Additionally, it is realized that the case hardened flange had a reasonable fatigue safety factor. In the real service test with 200 carburized flanges on 50 diesel engines, no failure was observed during 3000 engine operation hours (approximately 2 years).  相似文献   

11.
为了提高复合材料机翼的整体强度和刚度, 降低制造成本, 机翼的主要结构件采用缝编技术。肋片由肋腹板、缘条组成, 它是由整块缝编层合板剪裁加工制成。肋水平缘条和垂直缘条分别缝纫于蒙皮及桁腹板上, 桁缘条也缝纫于蒙皮上。采RTM 工艺成型。当在肋腹板方向施加拉力后, 肋水平缘条和蒙皮之间存在着剪应力, 引起层合板的分层, 肋垂直缘条和桁腹板之间存在着拉应力, 引起它们之间的撕裂。采用了二维和三维有限元混合模型进行分析, 获得了肋水平缘条与蒙皮、以及肋垂直缘条与桁腹板交界面上的应力分布, 并由试验研究验证了分析计算的正确性。   相似文献   

12.
Martensitic stainless steel nuts were received for failure analysis. A few of these nuts cracked at the immediate stress loading while the others fractured after 2 years of service. These nuts were subjected to different metallurgical tests such as visual examination, optical microscopy, chemical analysis, hardness testing, and fractography. It was concluded that improper heat treatment weakened the structure and subsequently fractured on the application of load.  相似文献   

13.
The strains at which buckling and debond growth occur in adhesively bonded composite flanges containing an initial debond were experimentally measured. Test parameters including initial debond geometry, flange material stiffness, and the adhesive critical strain energy release rate (Gc) were investigated. Debond growth was found to be strongly dependent on initial debond length but weakly dependent on flange width; i.e., debonding resistance did not increase in direct proportion with the bonded overlap dimension. Flanges having higher bending stiffness exhibited significantly lower debonding strain. Finally, the effect of Gc was evaluated at three levels by controlling the adhesive cure temperature and bondline thickness. Lower values of Gc (207 and 552 J/m2) allowed debond growth to occur while at the highest value of Gc (1500 J/m2), alternate failure modes occurred prior to debond growth. Ultrasonic C-scans revealed that debond growth occurred along a curved front, as dictated by the post-buckling deformation of the flanges.  相似文献   

14.
童根树  倪闻昊 《工程力学》2013,30(1):112-118
对于薄壁构件框架结构的梁柱节点处翘曲未知量之间的转换,软件ANSYS和ABAQUS采用了错误的做法。该文把节点域梁柱翼缘和加劲肋看成井字梁系,考虑它们在框架平面外的弯曲和扭转,通过翼缘板件内力和位移与杆件截面内力和位移的关系,得到了节点域与杆件的四个连接面上双力矩和翘曲位移的关系。对 形框架进行了算例分析,与板壳有限元计算结果进行了对比,验证了得到的翘曲半刚性公式的正确性。通过算例也验证了梁柱节点处柱子翘曲位移与梁翘曲位移近似存在着相等相反的关系。  相似文献   

15.
航天器大型法兰设计与计算   总被引:1,自引:0,他引:1  
针对航天器接口大型法兰所面临的空间环境条件的特点,鉴于在航天史上曾发生过航天器泄漏事件而造成重大损失的教训,为确保航天器密封法兰设计的安全性,从航天器法兰强度及刚度的理论计算入手,对法兰螺栓选择及优化设计进行了探讨.通过实践验证了这种计算和设计是可行的.  相似文献   

16.
为研究工业用途的某特种钢结构的抗震性能,该文在3个特殊构造梁柱节点的循环加载试验研究的基础上,采用有限元软件ABAQUS中的C3D8R实体单元建立模型,对该特殊构造梁柱节点的滞回性能进行了模拟分析,模型考虑了材料非线性、几何非线性的影响。通过有限元分析与试验结果的比较,验证了有限元模型的正确性。在此基础上,提取有限元模拟的局部分析结果,包括螺栓拉力的变化与节点组件的损伤指数,进一步为试验研究的最终破坏形态提供微观的力学解释。结果表明,试件I螺栓端板连接中梁翼缘两侧的螺栓拉力基本相同;试件I和试件II中柱强轴方向连接构造的断裂最可能发生在连接界面处的梁下翼缘中心,试件II和试件III中柱弱轴方向连接构造的断裂最可能发生在柱翼缘端部的盖板。研究结果可为此类特殊构造梁柱节点的各个组件力学行为分析以及相关的设计方法提供一定的参考。  相似文献   

17.
为进一步改善现行薄壁钢板组合截面PEC柱构件双向不等刚度和翼缘局部屈曲过于集中等力学性能缺陷,该文提出了采用翼缘钢板卷边的新型卷边钢板组合截面PEC柱类型。以拉结板条间距作为基本参数,对4个按新型卷边钢板组合截面强轴布置的足尺试件进行了恒定竖向荷载下的水平低周反复荷载试验,观察了试验过程中PEC柱卷边钢板组合截面翼缘钢板局部屈曲和混凝土部分裂缝开展与压溃发展过程,得到了试件的荷载-位移滞回曲线。根据试验结果分析了PEC柱的承载力、抗侧刚度、耗能与延性、变形模式与破坏模态等力学性能。结果表明:试验卷边PEC柱试件充分发挥了薄板局部屈曲后性能,具有优越的变形与耗能能力;构件的破坏模式为柱脚部位卷边钢板组合截面翼缘局部屈曲部位不断扩展和伴随混凝土大面积压溃。  相似文献   

18.
One of the 12 screws meant to fasten the diffuser segment to the flange of a turbine casing in an aeroengine was found broken in-service. Cracks were also observed in some of the remaining screws. The screws made of 35NC6 steel material were plated with cadmium. The chemistry, hardness, and microstructure (heat-treatment condition) of the screws met the drawing requirements. Heavy oxidation was noticed on the surface as well as on the fracture surface of the screws. Fractographic studies showed brittle intergranular features. Scanning electron microscope?Cenergy dispersive x-ray spectroscopy (SEM?CEDS) analysis detected cadmium on the entire fracture surface of the screws. Micro-examination and SEM?CEDS analysis of the cracked screws showed the presence of cadmium all along the path of crack propagation including the crack tip. From microscopic and fractographic studies, it was concluded that the screws had failed by liquid-metal-induced embrittlement (LMIE). It appeared that the screws had experienced high service temperature that had resulted in melting of the cadmium plating on the screws. The molten cadmium had penetrated (adsorbed) along the grain boundaries of the screw material causing the screws to eventually fail in the brittle (intergranular) manner by the phenomenon of LMIE.  相似文献   

19.
The satisfactory sealing of large reactor vessel flanges in petrochemical plant is a significant problem. It is necessary to accommodate relative flange movement of large pressure vessels and provide a system where adequate bolting can be applied. The leakage from a large flange can be a major contributor to plant emissions. Here a corrugated metal graphite covered gasket has been used to seal a flange 20 feet (6 m) in diameter on a high-temperature (450°C) reactor vessel. This has resulted in a significant reduction in emissions and plant maintenance. This feature is based on the submission by the winning team in the Fluid Sealing Association's 2003 Environmental Achievement Awards.  相似文献   

20.
In welded plate structures, fatigue cracks may initiate at the intersections between the flanges of longitudinal stiffeners and the web-stiffener attached to a transverse girder. The weld-toe cracks may initiate and propagate in the flange of the longitudinal stiffener, while in certain cases they may initiate from the root of the fillet weld resulting in the separation of the welded attachment from the flange. In order to distinguish such a morphological change of crack growth behavior, series of fatigue tests have been carried out, and the morphological variation of these fatigue cracks are successfully identified in terms of the normal and shear stress distribution acting along the fillet weld between the flange and the attachment.  相似文献   

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