42CrMo钢轮毂锻件超声波探伤缺陷分析

某批42CrMo钢轮毂锻件在进行超声波探伤检验时发现有密集型缺陷,导致锻件报废。通过低倍检验、金相检验以及扫描电镜分析等试验,对该轮毂锻件超声波探伤缺陷性质及产生原因进行了分析。结果表明:该42CrMo钢轮毂锻件超声波探伤缺陷性质为白点裂纹;其是在钢中氢和正火冷却应力共同作用下产生的;建议锻件在锻后避免直接空冷,且应进行去氢热处理。     

航空锻件常见表观缺陷及其控制研究

目的 揭示服役寿命长、工况苛刻、锻造成本高、质量控制难度大的航空结构件与发动机盘件用钛合金、高温合金等锻件外观缺陷的产生原因及控制措施。方法 按照航空锻件锻造流程(开坯、制坯、模锻和锻后热处理),分别研究裂纹、折叠、错移等锻造缺陷产生的原因。结果 航空锻件产生表观质量缺陷的原因一般由工艺设计不合理、锻造操作不当、工装设备保障不到位等导致,需结合锻件材料、形状、变形过程等采取对应措施进行优化解决。结论 对航空锻件缺陷产生原因进行了研究,给出了行之有效的解决措施,对于航空锻件质量的提高,尤其是新材料、大尺寸、复杂结构的航空锻件研制具有重要的工程指导意义。     

MB15镁合金模锻件纵梁低倍试样条状缺陷分析

某MB15变形镁合金模锻件纵梁低倍试样表面出现条状缺陷。通过断口分析、金相检验和能谱分析对条状缺陷的性质及其产生原因进行了探讨。结果表明:该缺陷的性质为偏析,其产生原因为锆元素偏聚,在模锻时沿零件变形方向纵向分布,低倍腐蚀后暴露出沿流线方向分布的缺陷形貌。     

300M钢锻件中的凹坑缺陷及其形成机理

对300M钢制锻件中的凹坑缺陷进行了观察与分析，并对凹坑缺陷的形成机理进行了分析与研究，结果表明，锻件中的凹坑缺陷是在锻造过程中产生的，它是在锻件裂纹延性开裂与扩展时，伴随锻造裂纹的产生，扩展以及微裂纹与空洞形成，连通，圆钝与氧化而形成的。     

浅谈固态模锻铝合金悬垂线夹

简述了固态模锻铝合金悬垂线夹的生产工艺,并针对该种模锻件的结构特点,从生产工艺角度分析了常见缺陷和产生的原因。     

20CrNi2MoA齿轮轴锻件缺陷分析

20CrNi2MoA钢齿轮轴锻件在第三次超声探伤过程中发现有4处严重超标缺陷。通过低倍检验、化学成分分析、金相检验和断口分析等方法对其超标缺陷进行了定性分析。结果表明:该缺陷为在氢和应力共同作用下产生的延迟性白点裂纹。     

车用2A12铝合金连接锻件变形规律分析与工艺设计

针对某种2A12铝合金车用连接锻件质量差,容易报废的问题,利用Deform仿真系统对该锻件的变形过程进行了模拟分析.根据模拟结果可知,锻件易报废是由于材料相对流动产生折叠引起的.鉴于此,在原工艺基础上增加了预锻工序,预成形后有效消除了材料的折叠缺陷.但同时又出现了锻件顶部枝叉充不满的缺陷,因此对锻模进行了优化,引入了阻...     

7A04模锻螺母开裂原因分析

通过化学成分分析、硬度测试、宏观及微观检验对某螺母螺纹根部出现开裂的原因进行了分析。结果表明:螺母开裂的原因是其存在设计缺陷,即退刀槽设计为模锻件的分模面,致使关键部位螺纹根部存在非锻造组织而使强度弱化。     

TC11钛合金锻件中疑似夹杂物缺陷成因分析

某TC11钛合金锻件在铣切加工过程中发现了疑似夹杂物缺陷,采用微观组织形貌观察、微区成分测试对其进行了定性分析,并通过预制夹杂物缺陷熔炼验证试验,确定了该缺陷的形成原因。结果表明:该TC11钛合金锻件中的疑似夹杂物缺陷为铣切加工过程中嵌入产品表面的刀具掉落碎块,为铣切加工时瞬间进刀量过大造成铣刀刀尖崩裂所致。     

0Cr18Ni9钢小接管锻件开裂原因分析

结合 0Cr18Ni9钢锻造、焊接工艺特点及过程 ,采用宏、微观检验及能谱分析等手段 ,对规格为2 7mm× 8mm的 0Cr18Ni9钢小接管锻件在组焊后出现开裂的现象进行了分析。结果表明 ,锻坯原材料中存在的中心疏松和氧化物夹渣等低倍缺陷是导致锻件开裂的主要原因。锻坯原材料是锻件质量控制的关键要素。     

基于类等势场和响应面法的复杂锻件预成形优化设计

为实现复杂锻件的预成形设计,以连杆的热锻预成形设计为研究对象,建立基于类等势场和响应面分析的三维复杂锻件的预成形设计方法。在分析毛坯与终锻件间等势场分布规律与特点的基础上,采用逆向拟合法提取等势面及线面光顺处理,实现等势面的高效精确重构。针对长轴类锻件的预成形设计要求,提出沿零件的长、宽、高分别设置合理的缩放因子的非均匀缩放方法。实现了预成形件材料分布的合理调控,获得了优化的预锻件和辊锻毛坯,最终获得了充填完整、无任何成形缺陷且飞边小的连杆终锻件。数值模拟结果表明,所建立的方法能较好实现复杂锻件的预成形优化设计。     

大型饼类锻件镦粗过程形变力学演变研究

针对大型饼类锻件夹层裂纹缺陷形成力学机理问题,采用非线性有限元模拟技术,建立了圆柱锻件镦粗过程的热力耦合分析模型.通过模拟计算,分析了H/D>2时镦粗过程中各向应力场、等效应变、应变速度以及形变梯度分布规律,得出了镦粗过程锻件内部应力状态演变分布图.研究结果表明:对于大型饼类锻件,夹层裂纹缺陷不能从应力状态得出合理的解...     

Evaluation of ultrasonic measurements in forgings

Large dynamically stressed forgings in nuclear and conventional power stations constitute a high risk potential if flaws are present and must therefore be subjected to ultrasonic inspection. Since flaws frequently cannot be repaired, it is important to determine their size for an appraisal of component integrity by fracture mechanics. By the example of large rotation-symmetrical forgings with manufacturing flaws, the possibilities and limits of evaluating the ultrasonic findings are described.     

钢锻件的超声波纵波手动检测工艺的优化

钢锻件超声波手动检测时,其工艺类似钢板纵波检测,但锻件厚度较大,不易确定其缺陷位置,也不易确定其当量。本文对此工艺进行了优化：包括对超声波检测仪器、试块、探头的选择、直探头偏离的测定、检测时机和表面准备、方向、灵敏度的确定校准和复核、手动扫查方法、灵敏度补偿、缺陷当量确定、记录和评级等。     

TC6钛合金安装座荧光显示缺陷原因

某TC6钛合金安装座在航空发动机上试车后,拆机进行荧光检查,在该安装座圆弧处发现长度约4 mm的线性荧光显示.采用宏观观察、微观分析、金相检验、硬度测试、能谱分析等方法对荧光显示缺陷产生的原因进行了分析.结果表明:该安装座上的荧光显示缺陷为疲劳裂纹.安装座圆弧表面在人工砂轮打磨时完整性被破坏,形成了疲劳裂纹源,在试车过...     

Analysis of surface defects of aluminium components with hard anodized layers

Final quality inspection regularly reveals surface defects on components after hard anodizing. The aim of the analysis was to identify the cause of the defects and unambiguously determine whether the defect is caused by the quality of the base material, manufacturing technology of the component, the heat treatment or by the final surface treatment technology (anodizing). Analysis of the chemical composition and hardness measurements were performed to eliminate the possibility of any errors during material selection and heat treatment process. The capillary test revealed two major defects and also small amount of minor defects. To determine cause of the defects, light and scanning electron microscopy including EDS chemical microanalysis was used. Detailed study of the major defect and EDS microanalysis of its interior confirmed existence of defect prior to coating formation. Further examination of the major defect and its surroundings led to conclusion, that the defect was formed during primary foundry processes when billet was manufactured.     

Comparative analysis of vision systems for electroplating surface quality inspection

In industrial practice, a human operator establishes the surface quality of an electroplated deposit through a subjective visual inspection, and this tends to be the immediate indicator of a quality defect. Electroplating in connector manufacture is a continuous process yet the quality inspection is an offline, operator-dependent process. The goal of this research was to automate the inspection of surface quality through the application of inline vision systems. Three vision system types were evaluated: a high-speed greyscale system, a standard colour system and a high-speed colour system. The efficacy of each approach was evaluated using attribute repeatability and reproducibility analysis (ARR); other factors considered were throughput, ease of operation and cost. The results proved that the high-speed colour system achieved the highest resolution reliability output for defect identification. Using key factor analysis and designed experiments, the optimum factor conditions were established for the high-speed colour system. To determine the practical implications such as false-positive and -negative results, the work was applied to a high-volume connector manufacturer. The overall benefit of such an implementation is an improvement in the defect rate and a reduction in risk priority number on the failure, modes and effects analysis of the process.     

Failure Analysis of an Automotive Bushing

The cause of a longitudinal fracture of an automotive bushing during the assembly process is presented in this study. On the basis of macroscopic inspection, scanning electron microscopy, energy-dispersive spectroscopy, microstructural examination, chemical analysis and hardness measurements, cleavage fracture was determined by the dominant fracture mode, and the fracture near the outer surface of the bushing was covered by impurities which is similar to the composition of the coating. Therefore, it is possible to infer that the crack existed before installation. In addition, the detailed metallurgical analysis demonstrates decarburization at the fracture surface due to a folding defect. In the process of assembly of bushing, the stress concentration and surface defect promoted the old crack propagation, finally, leading to the fracture of the bushing.     

桥梁电子化人工巡检养护管理系统

将危险性分析与量化管理理念应用于桥梁电子化人工巡检养护管理系统的总体设计中,为大型桥梁量身定制巡检养护规划,规范桥梁巡检养护流程,编制巡检养护手册,用于指导巡检养护工作的实施;针对桥梁结构的具体特点,建立专门结构的损伤库,编制电子化人工巡检养护软件,实现巡检养护管理工作的电子化。