浅谈车用CNG气瓶的定期检验

随着压缩天然气(CNG)的推广以及普及,越来越多的汽车进行改造安装CNG气瓶,而车用CNG气瓶的安全则成为了人们首要关注的事情,CNG气瓶定期检验,就是为了保障用车的安全。利用外观检查、水压试验、气密性试验等方法,对CNG气瓶进行定期检验,通过检验能够及时的发现缺陷,及时的排除隐患,因此对车用CNG气瓶进行定期检验是非常有必要的。     

车用压缩天然气气瓶爆炸事故原因分析

一燃料为压缩天然气(CNG)的车辆发生了CNG气瓶爆炸事故。为了解事故原因,确认是车辆自燃引起CNG气瓶爆炸,还是由于CNG气瓶爆炸而引起车辆燃烧,对爆炸后的气瓶残骸进行了试验检测与分析。经过对爆炸气瓶不同区域的化学成分分析、常温拉伸试验和显微金相检测,并根据爆炸气瓶残骸试验检测结果进行综合分析,最终确定了事故发生原因。     

车用CNG气瓶的安全检验与质量管理

针对当前天然气使用的安全性问题,就如何加强车用的CNG气瓶安全性检验和管理问题,进行重点研究和探讨。对此本文结合当前我国车用CNG气瓶应用的现状及存在的问题,提出在常用CNG气瓶的检验和管理中的几点措施,以此为当前车用气瓶的安全管理提供借鉴与参考。     

纤维环向缠绕复合材料气瓶冲击损伤容限研究

为研究纤维缠绕复合材料层CNG气瓶冲击后损伤容限问题,采用疲劳应变比率作为损伤变量,建立疲劳累积损伤模型;对气瓶缠绕层的冲击损伤剩余强度采用开孔等效计算方法,应用Nuismer—Whitney平均应力准则,关联疲劳累积损伤函数中的最大应力与拉伸载荷下的含孔层合板剩余强度的关系,建立适用于在疲劳载荷下的含孔层合板结构剩余强度的估算方法,用于复合材料CNG气瓶冲击剩余强度的预测。结果表明,文中提出的分析模型预测结果与专家提出的复合材料气瓶冲击损伤评定标准基本吻合。     

精简高效型CNG机床布局的研究设计

鉴于用途广泛的CNG气瓶专用加工机床布局繁杂、控制系统要求高等,研究设计简洁高效的机床布局,研究设计高精加工的数控移置式刀架,研究设计效果显著的雾化冷却系统,为CNG气瓶的高精加工提供新的技术,为其他产品的专用机床研究设计提供了发展方向。     

针对一种重型卡车燃气构架的优化设计及仿真分析

一种匹配了CNG的自卸车,CNG气瓶托架在用户使用过程中出现裂纹,且这种气瓶托架质量较重.本文作者针对以上两点对该托架做技术改进.应用CAE仿真分析其断裂处的受力情况,对其结构做优化设计.试验表明该方案满足试验要求,且有效降低了托架重量.     

CNG长管拖车气瓶爆破泄放装置结构探讨

根据有关标准要求,CNG长管拖车气瓶需要安装爆破泄放装置,为了提升CNG长管拖车的安全性与可靠性,该文对目前市场上已使用的多种泄放装置结构进行了分析,总结了其性能特点及存在的问题,并且在这些泄放装置结构的基础上设计了新型爆破泄放装置,该文对CNG长管拖车气瓶合理选用爆破泄放装置具有参考价值。     

气瓶内衬屈服强度对环缠绕复合气瓶疲劳性能影响的研究

为考察气瓶内衬材料的屈服强度对环缠绕复合材料气瓶(CNG-Ⅱ)性能影响,利用有限元数值模拟的方法,在气瓶的结构参数、纤维缠绕层参数、内衬材料的抗拉强度、自紧压力一定的情况下,研究内衬屈服强度变化对气瓶疲劳寿命的影响。有限元分析结果表明,随着内衬材料屈服强度的增加,CNG-Ⅱ复合气瓶的自紧效果变差,工作压力下所受环向平均应力增大,疲劳寿命降低。同时,对三种不同规格尺寸的环缠绕气瓶在不同屈服强度下的疲劳试验数据进行分析,进一步验证了复合气瓶的寿命随着内衬屈服强度的增加而减小。因此,在CNG-Ⅱ复合气瓶的生产过程中,有必要在一定程度上降低内衬的屈服强度,以改善复合气瓶的性能。     

CNG气瓶泄漏爆炸后果评价模型对比分析

CNG气瓶是CNG加气站中常用的一种储气装置,它作为一种高压储气容器,如果失效将会产生重大的危害后果。文中对其泄漏后产生的爆炸后果进行了分析,对比了蒸气云爆炸（VCE）定量评价模型和API pub 581定量后果评价模型,并在分析过程中结合某气瓶组的实例,对两种评价模型所得到的爆炸后果进行了比较。     

缠绕层表面缺陷对CNG-2复合气瓶爆破压力的影响

为了研究复合材料层表面缺陷对于CNG-2复合气瓶爆破压力的影响,通过考察实际的表面缺陷形状,将复合层表面缺陷简化为一定尺寸的矩形槽。对带有2 mm深度矩形槽型缺陷的复合气瓶进行爆破试验,并利用有限元数值计算软件ANSYS计算其爆破压力,以分析2 mm深矩形槽型缺陷对气瓶爆破压力产生的影响及其原因。结果表明,矩形槽型表面缺陷对于气瓶内衬应力的影响并不明显,而对缠绕层应力影响较大,缠绕层矩形槽型缺陷底面的应力超过复合材料抗拉强度保证值,使得复合气瓶爆破压力减小。     

A residual stress analysis program using a Matlab GUI on an autofrettaged compound cylinder

A program for the residual stress analysis of an autofrettaged compound cylinder is designed using a Matlab graphical user interface (GUI) and program design technique. The high-pressure vessels are autofrettaged in order to increase their operating pressure and fatigue life. An autofrettage process causes plastic expansion of the inner section of the cylinder, adding residual compressive stress to the bore after relaxation. Such a compound cylinder is produced via a shrink-fit procedure that incorporates a monobloc tube that has previously undergone autofrettage. This paper presents a simple and visual tool to calculate the residual stress and describe the distribution of residual stress for both the elastic-perfectly plastic model and the strain-hardening model.     

Analysis of the autofrettage effect in improving the fatigue resistance of automotive CNG storage vessels

Type II compressed natural gas (CNG) storage vessels for automobiles are becoming widely used. They are not only supplied to automakers in Korea (such as Hyundai Motors), but are being exported overseas in increasing numbers. Autofrettage is a process that produces beneficial residual stresses in a vessel by subjecting it to excessive internal pressure. This strengthens the vessel and improves its fatigue resistance. This paper presents research into the autofrettage process and the residual stresses it produces in type II CNG storage vessels. Finite element analysis and a closed-form equation are used. Fatigue resistance is then analyzed via a fatigue evaluation performed according to ASME section VIII.     

厚壁圆筒自增强压力的优化分析

采用考虑材料应变强化效应和包辛格效应的双线性材料模型,建立了厚壁圆筒自增强理论模型。基于工作时的等效应力及周向应力,提出了最佳自增强压力的评定方法并给出了理论求解过程。采用有限元软件对自增强厚壁圆筒涉及的三个加载过程进行模拟分析,模拟结果与理论计算结果相吻合。由模拟结果得到了厚壁圆筒工作时的最大等效应力和最大周向应力与自增强压力的关系曲线,并采用直接加权组合法进行优化,得到了最佳自增强压力。研究结果为厚壁圆筒最佳自增强压力的求解提供了新思路,具有一定的工程意义。     

A comparative study of thermal and hydraulic autofrettage

Thermal autofrettage is a potential process to generate beneficial compressive residual stresses at and around the inner wall of a thickwalled cylinder for increasing its pressure carrying capacity. Due to its simplicity and inexpensive arrangement, it can compete with the conventional hydraulic autofrettage process. In this work, a comparative study of the thermal autofrettage and the hydraulic autofrettage is carried out. As the thermal autofrettage does not require hydraulic power pack, the process is more economical than the hydraulic autofrettage. The thermal autofrettage process is also studied for the thick-walled cylindrical vessels subjected to high thermal gradient with or without pressure and is compared with the hydraulic autofrettage. Comparison shows that for cylinders subjected to high thermal gradient without pressure, the thermal autofrettage is superior to the hydraulic autofrettage.     

基于LabVIEW的超高压自增强测试系统设计

为了提高超高压缸体的承载能力并延长疲劳寿命,对制造缸体的原材料采取自增强处理,同时将LabVIEW技术应用到自增强处理过程中,开发了一个专门的超高压自增强测试系统.在LabVIEW环境下完成对自增强系统重要参数的采集、显示、存储以及相关性分析和曲线拟合等数据处理工作,取得了较好的效果.     

Effect of optimum plastic depth on stresses and load-bearing capacity of autofrettaged cylinder

Autofrettage is an effective measure to even distribution of stresses and raise load-bearing capacity for (ultra-)high pressure apparatus. Currently, the research on autofrettage has focused mostly on specific engineering problems, while general theoretical study is rarely done. To discover the general law contained in autofrettage theory, by the aid of the authors’ previous work and according to the third strength theory, theoretical problems about autofrettage are studied including residual stresses and their equivalent stress, total stresses and their equivalent stress, etc. Because of the equation of optimum depth of plastic zone which is presented in the authors’ previous work, the equations for the residual stresses and their equivalent stress as well as the total stress and their equivalent stress are simplified greatly. Thus the law of distribution of the residual stresses and their equivalent stress as well as the total stress and their equivalent stress and the varying tendency of these stresses are discovered. The relation among various parameters are revealed. The safe and optimum load-bearing conditions for cylinders are obtained. According to the results obtained by theoretical analysis, it is shown that if the two parameters, namely ratio of outside to inside radius, k, and depth of plastic zone, kj, meet the equation of optimum depth of plastic zone, when the pressure contained in an autofrettaged cylinder is lower than two times the initial yield pressure of the unautofrettaged cylinder, the equivalent residual stress and the equivalent total stress at the inside surface as well as the elastic-plastic juncture of a cylinder are lower than yield strength. When an autofrettaged cylinder is subjected to just two times the initial yield pressure of the unautofrettaged cylinder, the equivalent total stress within the whole plastic zone is just identically equal to the yield strength, or it is a constant. The proposed research theoretically depicts the stress state of ultra-)high pressure autofrettaged cylinder more accurately and more reasonably and provides the reference for design of (ultra-)high pressure apparatus.     

复合机械自紧技术研究

由于Bauschinger效应的影响，自紧厚壁管反向屈服现象普遍存在，使得内壁残余应力减少，厚壁管承载能力下降，因此，通过复合机械自紧技术，可消除Bauschinger效应，提高自紧厚壁管的弹性强度。本文在理论上和工艺上对复合自紧技术进行了研究，结果表明可大幅提高自紧 厚壁管的强度，这对自增强压力容器和管道设计具有指导意义。     

Residual stress analysis of an external grooved thick-walled pressure vessel

Residual stress analysis of an autofrettaged thick-walled pressure vessel containing an external groove was described in order to calculate the stress concentration at the external groove. The autofrettage residual stress distributions of the external grooved thick-walled pressure vessel were simulated using an equivalent thermal loading from the analogy of thermal and autofrettage residual stress fields. Thermal stresses due to the simulated thermal loadings for various degrees of autofrettage overstrain level were computed using finite element methods. Very high stress concentration factors due to autofrettage loadings were obtained at the external groove root that contained a sharp root radius. Experimental measurement of residual stresses for a fully autofrettaged smooth thick-walled pressure vessel using an equivalent saw cut method resulted in very close agreement with the theoretical autofrettage residual stress distributions. The stress analysis results implied that the autofrettage residual stress concentration might cause a cracking problem at the external groove root of the thick-walled pressure vessel, indicating that lower autofrettage overstrain and a groove geometry change were desirable for enhanced durability.     

压缩天然气钢瓶水压试验监控系统设计与实现

介绍了基于组态软件MCGS的压缩天然气(Compressed NaturalGas,CNG)钢瓶水压试验监控系统的设计及实现方法,上位机采用组态软件MCGS建立人机界面,下位机采用西门子S7-300型PLC进行现场控制,系统监控界面友好,运行稳定可靠,实现了压缩天然气钢瓶水压试验的自动化操作,检验效率提高。     

Elastic-plastic stress analysis and fatigue lifetime prediction of cross-bores in autofrettaged pressure vessels

Elastic-plastic stress analysis has been performed to evaluate the fatigue life of an autofrettaged pressure vessel containing cross-bores subjected to pulsating internal pressure of 200 MPa. Finite element analyses were used to calculate the residual and operating stress distributions of the pressure vessel due to the autofrettage process and pulsating internal pressure, respectively. Theoretical stress concentration factors of 3.06, 2.58, and 2.64 were obtained at the cross-bore of the pressure vessel due to internal pressure, 50%, and 100% autofrettage loadings, respectively. Local stresses and local strains determined from the elastic-plastic finite element analysis were employed to calculate the failure location and fatigue life of the pressure vessel with radial cross-bores, incorporating the low-cycle fatigue properties of the pressure vessel steel and fatigue damage parameters. Increase in the amount of overstrain by autofrettage process moved the crack initiation location from the inner radius toward a mid-wall, and extended the crack initiation life, Predicted fatigue life of the fully autofrettaged pressure vessel with cross-bores increased about 50%, compared to the unautofrettaged pressure vessel. At the autofrettage level higher than 50%, the failure location and fatigue life of the pressure vessel were not significantly influenced by the autofrettage level.