贮氢压力系统结构安全评定研究

发布时间：2019-02-13 20:49

【摘要】：贮氢压力系统是一类用于加注、贮存及快速释放氢的小型装置,其安全性是产品寿命周期内关注的重点。贮氢压力系统结构较为复杂,存在焊接,缺陷不可避免。对于产品在制造和运行过程中出现的缺陷,遵循“合于使用原则”,以断裂力学方法为基础,开展结构缺陷的检测与计算分析,评估产品的安全性,从而决定其是否还允许继续使用,是一类合理有效的工程评定方法。基于J积分理论的失效评定图技术由于理论严密,适用于多种失效模式,已经成为目前国际上“含缺陷构件安全评定标准”的主流方法,本文基于此技术开展贮氢压力系统主体承载结构安全评定工作。本文首先依据BS7910、SINTAP和GB/T 19624标准,根据贮氢压力系统结构、制造、材料及载荷特点,拟定了结构安全评定程序及项目；然后开展了系统结构缺陷检测与表征,材料性能参数获取,结构应力求解三项研究工作；最后基于Ainsworth和通用失效评定曲线构建理论、GB19624和BS7910塑性截止线规则,建立系统结构安全的失效评定图,计算不同缺陷参数评定点绘于失效评定图中,由图给出贮氢压力系统结构安全评定结论,并计算评定点安全系数和最大缺陷尺度下的极限载荷。研究结论包括：贮氢压力系统结构主缺陷为焊缝底端未焊透,基于工程可操作性和保守性要求,将其等效简化为三参量矩形截面环向缺口。系统结构用材FeCrNi奥氏体不锈钢强度、塑性及韧性良好,但充氢后材料塑性和断裂韧性有损减。电子束焊缝区与基材性能差异不显著,弯曲载荷下破坏模式仍为塑性失稳。内压及离心载荷联合作用下,系统结构最大等效应力出现在未焊透缺陷根部两侧尖端,且随缺陷深度的增加而增大,随缺陷宽度的减小而增加；未焊透缺陷深度对应力的影响大于宽度的影响,窄而深的缺陷应加强控制和消除。当未焊透缺陷深度不超过1.5mm(60%壁厚)时,结构是安全的,安全系数为1.9至4。系统结构失效模式为塑性失稳,在韧度下降及裂纹扩展情况下向弹塑性撕裂转变。系统结构强度随离心载荷增大而接近安全边界,未焊透缺陷深度1.5mmm宽0.1mm时,以屈服应力计算载荷比,离心载荷约190g时系统结构处于临界安全状态；以流变应力计算载荷比,离心载荷约270g时系统结构处于临界安全状态。贮氢压力系统结构安全评定是一项系统工作,研究涉及制造检测、材料、力学等多学科领域,拘于有限的时间和能力,本课题至此还存在诸多问题和不足,比如未考虑焊接区域的热应力、焊缝与基材强度的高低匹配性、非均布应力状态下应力强度因子的有限元精确解、计算模型中的数据分散性等问题,这都有待后续研究。
[Abstract]:Hydrogen storage pressure system is a small device for charging, storage and rapid release of hydrogen. Its safety is the focus of attention in product life cycle. The structure of hydrogen storage pressure system is complex, welding is existed, and defects are inevitable. In order to evaluate the safety of the products, the defects in the manufacturing and operation process should be tested and calculated based on the fracture mechanics method, in accordance with the principle of "fit for use". It is a kind of reasonable and effective engineering evaluation method to decide whether it is allowed to be used or not. Due to the rigorous theory, the failure assessment chart technology based on J integral theory is suitable for various failure modes, and has become the mainstream method in the international "safety assessment standard for defective components". Based on this technology, the safety assessment of the main bearing structure of hydrogen storage pressure system is carried out. Firstly, according to BS7910,SINTAP and GB/T 19624 standards, according to the structure, manufacture, material and load characteristics of hydrogen storage pressure system, the procedure and project of structural safety assessment are worked out. Then, the structural defect detection and characterization of the system, the acquisition of material properties parameters, and the solution of structural stress are carried out. Finally, based on the theory of Ainsworth and general failure evaluation curve, and the plastic cut-off line rule of GB19624 and BS7910, the failure assessment diagram of system structure safety is established, and the evaluation points of different defect parameters are calculated and drawn in the failure assessment diagram. The conclusion of structural safety assessment of hydrogen storage pressure system is given from the diagram, and the safety factor of the assessment point and the limit load under the maximum defect scale are calculated. The conclusions include: the main defect of hydrogen storage pressure system is that the bottom end of the weld is not fully welded. Based on the requirements of engineering maneuverability and conservatism, the structure of hydrogen storage pressure system is reduced to a three-parameter circular notch with rectangular section. The strength, ductility and toughness of FeCrNi austenitic stainless steel are good, but the ductility and fracture toughness of the material decrease after hydrogen filling. There is no significant difference between the properties of the electron beam weld zone and the substrate, and the failure mode is still plastic instability under bending load. Under the combined action of internal pressure and centrifugal load, the maximum equivalent stress of the system appears at the tip of the root of the defect which is not welded through, and increases with the increase of the depth of the defect and the decrease of the width of the defect. The influence of depth of weld penetration defect on stress is greater than that of width, and the narrow and deep defect should be controlled and eliminated. The structure is safe when the depth of the defect is not more than 1.5mm (60% wall thickness), and the safety factor is 1. 9 to 4. The failure mode of the system is plastic instability, which changes to elastic-plastic tearing under the condition of the decrease of toughness and crack propagation. The structural strength of the system is close to the safety boundary with the increase of centrifugal load. When the depth of weld penetration defect is 1.5mmm wide 0.1mm, the yield stress is used to calculate the load ratio, the centrifugal load is about 190g and the system structure is in a critical safe state. When the centrifugal load is about 270 g, the structure of the system is in a critical safe state when the flow stress is used to calculate the load ratio. The structural safety assessment of hydrogen storage pressure system is a systematic work. The research involves many subjects such as manufacturing, testing, materials, mechanics and so on, and is limited to limited time and ability. So far, there are still many problems and shortcomings in this subject. For example, the thermal stress in the welding area, the strength matching between weld and substrate, the finite element exact solution of stress intensity factor under non-uniform stress state, and the data dispersion in the calculation model are all to be studied in the future.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TH49

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