涂层酸性盐雾环境下失效过程的电化学阻抗谱分析

目的探究车辆装备有机涂层在沿海地区酸雨污染环境下的腐蚀行为。方法利用电化学阻抗谱技术,对金属漆涂层酸性盐雾环境下的腐蚀失效过程进行研究,分析其电化学阻抗谱特征及涂层电容的变化规律,并利用10 Hz下的中频相位角(θ_(10))和阻抗模值(|Z|_(10))评价金属漆涂层的防护性能。结果金属漆涂层的腐蚀失效过程大致经历3个阶段,即涂层完好阶段、涂层防护性能下降阶段和涂层失效阶段,随着腐蚀时间的增加,涂层电容逐渐增大,当θ1028.78°,|Z|101.78×10~7?·cm~2时,涂层基本丧失腐蚀防护能力。结论利用中频相位角和阻抗模值可以有效地评价金属漆涂层酸性盐雾环境下的腐蚀防护性能,为车辆装备在沿海地区的腐蚀防护提供技术支撑。     

热循环作用下圆筒基体热障涂层的失效过程分析

用等离子喷涂的方法在高温合金圆筒上制备热障涂层,通过红外线辐照圆筒外部对试件进行加热以及内部通冷却空气强制冷却的方法对热障涂层系统进行了热循环失效试验。利用有限元工具ABAQUS对热障涂层系统中的瞬时温度场与应力场进行了计算以分析热障涂层的失效原因。计算结果表明,试样处于稳态最高温度时以及降温过程开始的很短时间内,陶瓷层中出现较大的周向拉应力,该应力将导致热障涂层出现表面垂直裂纹;陶瓷层与粘接层界面的径向应力不足以引起界面的开裂,界面的起裂来源于垂直裂纹出现后所带来的边缘效应。     

衔铁连续冷挤压模具失效分析及工艺改进

通过对衔铁连续冷挤压工艺进行试验,对挤压过程中模具失效进行了分析,并提出了合理的工艺改进,对薄壁、非对称零件连续冷挤压工艺设计及试验有参考作用。     

直眼掏槽破岩过程模拟与空孔效应分析

基于空孔直眼掏槽的基本形式,运用三维有限元软件LS-DYNA,模拟了槽孔与3种不同直径空孔的动态破碎贯通过程,得到了直眼掏槽爆破应力分布规律.模拟结果表明:空孔在掏槽爆破中提供初始自由面,对槽腔岩石破碎具有导向作用;通过3组模型破岩过程的对比,可以清晰的看出空孔直径越大,破岩过程的拉伸破坏区域和压缩破坏区域越明显.进一...     

某型火炮击针失效分析

目的为了解决火炮击针断裂的问题。方法对断裂的火炮击针进行了宏观检查、化学成分分析、机械性能测试、断口分析、宏微观组织检测,确定了击针断裂的性质和产生原因。结果火炮击针断口属多源疲劳断口。结论击针断裂的主要原因:一是螺纹槽根部半径R较小,截面过渡不够平滑和自然,形成了较大的应力集中;二是螺纹槽根部的加工比较粗糙,进一步加剧了应力集中;另外,发射药形成的高温气体对火炮击针螺纹槽根部有腐蚀作用,导致击针螺纹槽根部R处出现点蚀坑,点蚀坑破坏了该处的表面完整性,形成了较大的应力集中,导致在点蚀坑处萌生了早期疲劳裂纹。建议改进工艺设计,增大螺纹槽根部R,确保截面过渡平滑自然,以降低颈部的应力集中系数;改进加工能力和水平,防止出现机加工缺陷。     

摆动凸轮失效分析

采用化学成分分析、硬度测试和断口分析等方法分析了某载重车辆钢摆动凸轮断裂的原因。结果表明：摆动凸轮断裂是由于回火脆而导致的脆性断裂。     

Failure Analysis and Prevention of High-Voltage Failure of FHP Motor

This paper describes a systematic approach adopted to identify the possible causes of fractional horsepower AC motor failure and subsequent fault-proofing procedures developed using Poka-yoke concept. Seven quality control tools and Why–Why analysis are employed to determine the root cause of problem, and poka-yoke technique is used for process redesign. As a result human errors are eliminated, and improved process design led to negligible failures from the initial failure rate (4500 ppm). The whole approach is generic in nature and can be adopted to solve wide variety of industrial problems.     

橡胶密封膜的失效分析

用红外光谱和电子能谱对某破损橡胶密封膜进行了分析 ,分析结果表明 ,橡胶密封膜为氯丁橡胶和丁腈橡胶并用胶 ,与外层胶材质要求不符 ,这是橡胶密封膜过早失效的主要原因     

水翼船大王柱断裂原因分析

对水翼船断裂的大王柱进行了化学成分、力学性能、断口等分析,并结合其使用环境、受力情况及工作状况进行研究。结果表明,大王柱的断裂是由于采用低强度材料进行表面补焊所致,其不合理的尖角设计以及表面加工粗糙也是造成其断裂的原因。     

Stress and Failure Analysis of Brittle Matrix Composites. Part II: Failure Analysis

A linear elastic fracture mechanics analysis of a cylindrical element of matrix with a single fiber and two matrix annular cracks perpendicular to the fiber direction under longitudinal tensile load was undertaken. The order of singularity and the angular dependence of the stress field in the neighborhood of the crack periphery were determined by using the stress function approach proposed by Zak and Williams. The stress intensity factor was evaluated by combining the results of the local stress solution with a finite element analysis. The case of fiber debonding originating from the periphery of the annular cracks was also studied. For that problem both opening-mode and sliding-mode stress intensity factors and the strain energy release rate were determined. These results help to understand the various failure mechanisms including matrix cracking, debonding along interfaces and kinking of interface cracks into fibers in brittle matrix composites. This revised version was published online in July 2006 with corrections to the Cover Date.     

从银行取款过程重看流程的概念及分析

基于银行取款过程的分析，对流程、阶段、任务、操作的概念进行了讨论。指出对流程概念存在的误解：如人不可以是操作对象、原流程分析容易忽略顾客的目标和需求、系统范围太窄、系统内有两个以上的操作者将会有协作问题等。由此，强调了分析中系统目标的重要．指出流程概念至少包含两个层次，最底层应该是相对的原子操作，因此分析中没有考虑原子操作的优化流程不应该视为优化流程。最后给出了取款过程改进的结果。     

一次不锈钢电抛光故障的排除

按照工艺配方[1]配制不锈钢电抛光溶液后,严格按工艺规范操作,发现零件电抛光后,表面或多或少有过腐蚀的现象,过腐蚀部位并不固定,并且过腐蚀程度也不同。 我厂采用的不锈钢电抛光配方及操作条件是:     

Failure of Wheels Due to Improper Manufacturing Process

Premature cracking of wheels was observed in the prime movers used for logistic services. The fractures were located between the stud-holes and between stud-holes and hand-holes. A detailed study was carried out to investigate root cause(s) of these failures. Although chemical composition and mechanical properties of bulk material were the same, there was a difference in microstructure and hardness at the edges of stud-holes. In addition, metallography revealed the presence of burr at the circumference of the stud-holes. A number of hairline cracks and a severely distorted structure were also observed at this location. Fractography, using an SEM, confirmed the presence of sharp cracks at the root of the burr. The hardness at the edge was also higher than the bulk material. The problem was found to be due to the manufacturing process which may be inducing more work hardening and deformation than permissible at regions near the holes edges. This deformation and hardening created a material condition that led to fine cracks in this region. The resulting fine cracks grew during service under fatigue and caused premature failure of the wheels.     

压缩机活塞杆断裂分析及预防

通过某压缩机断裂活塞杆材料成分、宏观和微观断口、力学性能、金相组织等分析，确定了其断裂的模式为疲劳断裂，找到了造成断裂的主要原因和影响断裂的各种因素，提出了预防断裂的有效措施。     

失效分析专家系统

对系统结构、失效分析知识的获取和表达及计算机推理进行了研究.该系统包括六个主要功能模块:知识库及其管理系统、知识获取、数据库及其管理系统、字典库及其管理系统、推理机、人机交互界面.失效分析知识的获取采用了通过文本及机器学习方法;知识的表达采用了框架、规则及面向对象综合表达方式.计算机推理则采用不确定性推理方法,具体采用了置信度方法.     

涡轮导向叶片的失效分析EI

使用光学、电子等微观手段及宏观力学分析方法证明，由不均匀的温度分布所引起的热应力、燃气中的腐蚀性介质及铸态组织中的枝晶是引起涡轮叶片开裂的主要原因。本文还对提高其使用寿命的方式进行了探讨。     

气阀失效分析

某船机增压器有异常响声,拆卸后发现喷嘴环上有破损气阀残留物卡滞,气阀盘部掉块打坏增压器。采用宏观检验、化学成分分析、力学性能测试、金相检验和硬度测试等方法对气阀的失效原因进行了分析。结果表明：该气阀失效是由于高温氧化引起的热腐蚀疲劳失效。最后对目前的气阀工艺提出了改进建议。     

Cervical Stent Failure Analysis

Harrington rods failed after a short period in service. Metallurgical analysis showed (1) notches were present on the rods, (2) small cracks present in the bent regions of the rod, and (3) the fractures occurred at clamped locations. All of these conditions can shorten the fatigue life by eliminating the crack initiation stage of fatigue and allowing corrosion fatigue to occur.     

Inconel 625合金波纹管失效分析

采用化学分析,透射电子显微镜(TEM)、X射线光电子能谱仪(XPS)和扫描电子显微镜(SEM)等微观测试手段对失效波纹管化学成分、力学性能、断口腐蚀产物及断口微观形貌进行综合分析。研究结果表明,波纹管的失效是材料在腐蚀性环境下局部高应力处首先发生高温氧化、硫化腐蚀,产生疲劳裂纹源,在交变应力的作用下发生腐蚀疲劳而造成的。通过降低腐蚀和波纹管应力可以防止或减轻腐蚀疲劳发生,延长波纹管使用寿命。