银基触头材料裂纹类型及形成机理研究

根据不同电流等级及不同触头闭合压力,对银基触头材料裂纹类型及形成机理进行了分析研究。通过实验研究和理论分析,提出了三种裂纹类型并分析了每种裂纹的形成机理。     

输气管道环焊缝表面裂纹管道极限载荷计算方法

为了便于对天然气长输管道环焊缝缺陷进行准确快速的安全评估,建立了考虑裂纹尖端奇异性的含环焊缝缺陷的有限元模型,计算了不同缺陷尺寸下的管道环焊缝裂纹J积分,分析了焊缝匹配系数及材料硬化指数对J积分的影响,进而研究了基于J积分理论的含缺陷管道的极限载荷影响因素,并在此基础上提出了适用于特定匹配系数和材料硬化指数情况下能够实现J积分及极限载荷快速求解的工程计算公式。研究结果表明:①根据有限元计算结果拟合的工程计算公式具有较高的精度,可以满足较大缺陷几何尺寸范围内J积分求解,实现含环焊缝裂纹缺陷的管道极限载荷求解;②含环焊缝缺陷管道的裂纹J积分与缺陷尺寸、材料属性以及焊缝匹配系数密切相关,含缺陷管道的极限载荷会随着裂纹尺寸的增加而降低,而随着材料硬化指数的增大而增大;③对含环焊缝中心线处表面裂纹的X80钢制管道而言,低匹配焊接管道极限承载能力要弱于高匹配或等匹配焊接管道。结论认为,该研究成果可为现役输气管道的安全评价及完整性管理提供参考。     

Creep crack growth testing of P91 and P22 pipe bends

Laboratory component tests play an important role in the development of life assessment procedures for high temperature crack initiation and growth. Thus, the working programme of the project BE 1702 HIDA, which addressed the validation, expansion and harmonisation of existing procedures for high temperature defect assessment, included a comprehensive experimental programme with feature tests of components as its core. Because of their relevance for the high temperature industry, P91 and P22 were included in HIDA among five materials. This paper presents laboratory creep crack growth tests of P91 and P22 pipe bends, discusses the test experience and draws some conclusions for laboratory component tests in general. The components were prepared with spark-eroded notches at the outer surface. The test temperature was 625°C for P91 and 565°C for P22.     

某固体火箭发动机点火器药柱断裂分析与改进

针对某固体火箭发动机点火器加速老化后,在低温动力环境试验中部分产品的B/KNO 3点火药柱断裂现象,采用故障树法对断裂的原因进行了排查,并通过压力试验、强度仿真等方法对其进行分析。结果表明：药柱支撑体与装药管体间较大的间隙和药柱支撑体排列的不合理,导致药柱在振动过程中出现应力集中区域,从而产生断裂。因此,提出了消除间隙、增加支撑体、优化支撑位置等改进措施,验证试验表明改进措施消除了药柱断裂现象。     

Two-Dimensional Problem of a Crack in Thermoelectric Materials

The two-dimensional problem of a crack in thermoelectric materials is studied in this research. The general solution is derived based on the complex variable method. For the case of a crack subjected to remote electric current and heat flow, the solutions are obtained in closed-form. The results show that the fields of heat flow, electric current, and stress exhibit traditional square-root singularity at the crack tip. The remote electric current produces both type I and II stress intensity factor. Furthermore, the stress intensity factor has a linear relationship with the heat flux, but a non-linear relationship with the electric current.     

12V190大功率柴油机模锻连杆断裂失效分析

本文通过对190柴油机模锻连杆上的裂纹检验分析,找到了造成该批连杆开裂的主要原因,是由于原材料中存在严重的成分偏析所致。同时指出了连杆在锻造和热处理过程中存在问题。通过这一失效事件,我们也指出了这种原材料缺陷目前在我国国家标准GB3077《合金钢结构钢》中还没有做出限制规定。希望有关单位,今后在制定原材料验收标准及生产操作时应引起重视。     

The Fracture Behaviour of a Rubber-Modified Epoxy Under Impact Fatigue

The fracture behaviour of a rubber-modified epoxy adhesive under impact fatigue has been investigated. An instrumented-impact test has been employed to apply multiple, “repeated-blow,” impacts to pre-cracked three-point-bend specimens at sub-critical energy levels. A fracture mechanics approach has been adopted to assess the effects of the impact-fatigue damage on the epoxy material.     

环氧树脂裂纹扩展的扫描电镜原位观察与分析

在扫描电镜内对环氧树脂ＣＴ试样加载，观察分析了裂尖场材料的微观力学行为．结果表明，低速加载时，裂纹的扩展是不连续的．扩展的模式为裂尖张开、钝化和向前扩裂尖应力应变场内的应变不均匀．在裂尖的正前方和与裂面成３５°～４０°角处出现高应变区，微损伤在该区域萌生发展，从而增加材料的裂纹扩展抗力．     

共振诱导V形槽尖端萌生裂纹机构的研究

在低应力精密下料中,提出采用共振效应诱导棒料V形槽尖端萌生微裂纹的方法,并设计了相应的激振系统.利用Solidworks和ANSYS软件,简化了该激振系统的三维造型,并对其进行了模态分析.结果表明,调整振动电动机的偏心块质量,能够有效实现激振系统的整体性能,这为高效高质量精密下料打下了基础.