双耳托板螺钉断裂原因分析及改进措施

双耳托板螺钉装配过程中在托板与杆部结合处发生断裂。对断裂螺钉进行断口形貌分析,确定断裂性质为过载断裂;对同批次螺钉进行了金相、硬度、拉力试验、楔负载试验以及模拟安装试验,结果表明,螺钉断裂原因主要与断裂位置流线密集有关,同时热处理制度不匹配和流线被切断对断裂有促进作用。针对螺钉断裂有关原因提出了改进冷镦工艺、调整热处理制度和优化头(托板)杆加工工艺等改进措施,并对改进效果进行了验证,结果表明改进有效,新工艺加工的螺钉装配过程未再发生相同断裂现象。     

钛合金螺钉脆性断裂原因分析

钛合金螺钉在装配过程中发生断裂失效,对装配和模拟扭转试验过程中断裂的钛合金螺钉断口进行了宏微观观察和能谱成分分析,对同批次螺钉进行了应力持久试验,对失效钛合金螺钉的金相组织进行了检查.结果表明,螺钉的断裂性质相同,均为脆性断裂;螺钉断裂的主要原因是存在内部缺陷,而与氢致脆性断裂的关系不大;螺钉的内部缺陷可能是在锻造过程后期由于某种偶然因素造成了原始β晶界开裂所致.     

杆端关节轴承失效分析

针对直升机杆端关节轴承杆端体多次出现断裂故障进行失效分析,通过断口宏微观观察、材质检测、能谱分析、裂纹源周围特征观察以及疲劳试验件断口分析等,结合对未装机国产件和进口件杆端体内壁加工表面观察对比,分析出故障件的断裂性质为疲劳断裂,断裂起源于杆端体内壁与轴承外圈的微动磨损处,故障件发生微动磨损的原因与杆端内壁表面加工方式不合理有关。为深入查找原因,对改进工艺后的同一型号国产件通过不同装配方式进行疲劳试验性能分析和疲劳断裂件失效分析,得出采用温差装配改进后的轴承可最大程度的降低发生疲劳断裂的风险。     

进气道拉紧螺栓断裂分析

机务检查发现飞机左侧进气道横向拉杆的拉紧螺栓发生断裂。对失效拉紧螺栓的宏微观特征和金相组织进行检查，并对其硬度和化学成分进行检测。结果表明:拉紧螺栓断裂性质为疲劳断裂，断裂原因与异常装配预紧力叠加进气道载荷有关。同时针对性提出调整工序顺序、增加专用工装、完善工艺规程等改进措施。通过监控20架飞机的装配过程，并收集部队1年多的飞行反馈信息，未发生同类故障。     

某型号前轴疲劳试验及结果分析

为测试前轴的疲劳寿命,采用台架试验装置对某型号汽车前轴进行了试验,仅运行19.9万次就发生断裂。通过对断口的观察分析、断口部位的金相分析、硬度检测等方式,确定了前轴的失效模式,并对其断裂失效原因进行了分析。研究结果表明:汽车前轴的断裂性质为疲劳断裂,裂纹源起源于锻件飞边表面,该处存在较明显的沟槽;锻件表面的加工沟槽形成的附加应力集中是造成前轴疲劳断裂的主要原因;加工沟槽可能由于切边模的磨损而产生,因此切边模刃口需及时修整。     

60Si2MnA弹条断裂分析

60Si2MnA钢制弹条进行疲劳寿命试验,未达到规定的疲劳寿命时发生断裂.通过断口宏微观观察、金相组织检查、硬度检测、化学成分检测,对弹条断裂原因进行了分析.结果表明:弹条断裂性质为弯曲-扭转疲劳断裂,其断口明显分成疲劳源区、扩展区和瞬断区3个区域,疲劳源区位于弹条表面;弹条断裂主要原因与弹条表面质量差有关,弹条表层存在脱碳层导致弹条抗疲劳性能降低,也是弹条疲劳断裂的又一原因.     

防喘压力信号管断裂分析

发动机防喘压力信号管多次于钎焊位置断裂。采用外观检查、断口宏微观形貌观察及金相分析,对其中一件典型管件进行了综合分析。结果表明：管件断裂于引接管长管弯管段球座根部位置,断裂起源于表面的钎料层,断口可见明显的疲劳条带特征,断裂性质为疲劳断裂。失效的主要原因是由于钎料层不均匀,韧性较差,且管件在装配过程中存在较大的变形,使钎料层沿枝晶开裂,形成原始裂纹。在防喘压力信号管工作过程中,在振动应力作用下发生疲劳扩展并最终导致管件断裂。通过严格控制钎焊过程并防止装配中管件发生较大的变形可以避免该类故障。     

基于有限元分析的螺钉断裂失效研究

油泵进行可靠性强化振动试验时发现一个螺钉提前断裂。通过宏微观观察和组织、硬度检测手段,对该螺钉的断裂性质和断裂原因进行了分析。结果表明:螺钉为疲劳断裂,主要是由螺帽与螺孔周围的不良接触导致。为进一步分析不良接触现象对螺钉应力分布的影响,进行了有限元分析,计算结果表明:局部集中力能够明显改变螺钉应力分布状态,显著增加了与局部集中力同侧的螺纹底部的最大应力水平。综合分析后可知,不良接触现象中焊点与螺帽之间的不良接触是螺钉断裂的主要原因。     

游星齿轮轴承失效分析

某发动机用游星齿轮轴承在工作过程中发生失效,保持架断裂,滚棒、滚道磨损.本文对失效保持架、滚棒、中间齿轮轴进行了断口形貌观察、金相组织及硬度检测、化学成分分析等工作.分析结果表明,保持架的断裂性质为疲劳断裂,滚道的损伤性质为接触疲劳.游星齿轮轴承的失效主要与轴承组件中应力不均匀、局部应力过大有关.     

30CrMnSiA钢制电机固定螺栓断裂原因分析

固定电机的30CrMnSiA钢制螺栓在使用过程中发生断裂,通过载荷分析、螺栓外貌及断口形貌观察、显微组织分析、化学成分及硬度检测,对其断裂原因进行了分析。结果表明:螺栓的失效性质为疲劳断裂,螺纹根部的加工损伤是疲劳裂纹源,而螺栓表面脱碳对疲劳断裂起到了促进作用。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

The Mirror with Patterns of Auspicious Animals and Grapes——Exquisite cast mirror and the technology of surface tin-enrichment by rubbing-in and infiltration of tin-rich powder

<正>Bronze mirrors were used by the Chinese people before the introduction of the glass mirror.Only after it was replaced by the glass mirror did the bronze mirror gradually retreat from people's lives.Different styles of bronze mirrors were made in different historical periods,particularly in the Warring States Period,the Han and Tang Dynasties,which were the three peaks of the development of bronze mirror arts in ancient China.The casting techniques were exquisite.The surface of the bronze mirror was smooth and bright enough to reflect one's image,and there were scarcely any casting defects on the mirror surface.On the back of the bronze mirror,there were rich depictions of Arts and Humanities,and the ornamentations were also     

The 9th China International Diecasting Congress & Exhibition

The 9th China International Diecasting Congress ＆ Exhibition was held on July 22-24, 2014 at Shanghai New International Expc Centre. This exhibition was the most successful over the years, with over 6890 visitors and 155 exhibitors, and the exhibition area increased by 30% from 9,500 square meters in 2012 to 12340 square meters. Die casting enterprises from a total of 24 countries and regions, including China mainland, Chinese Taiwan and Hong Kong, South Korea, Japan, Germany, India, Thailand, Malaysia, the United States, Russia, Australia, Iran, Ukraine, Brazil, Colombia, Singapore, Austria, Canada, Croatia, France, Turkey, United Kingdom, Vietnam, attended the congress and exhibition.     

Introduction of the Fluid Control Engineering Institute of Kunming University of Science and Technology

正The Fluid Control Engineering Institute of Kunming University of Science and Technology was set up in 1996.The researches of institute concentrate on electro-hydraulic(pneumatic)servo/proportional control and hydromechatronics.The Institute is committed to research and development of electro-hydraulic control of high-end technical equipment in ferrous metallurgy refining produc-     

RARE METALS Volume Contents

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Antimony Induced Crystallization of Amorphous Silicon

Antimony induced crystallization of PVD (physics vapor deposition) amorphous silicon can be observed on sapphire substrates. Very large crystalline regions up to several tens of micrometers can be formed. The Si diffraction patterns of the area of crystallization can be observed with TEM (transmission electron microscopy). Only a few and much smaller crystals of the order of 1μm were formed when the antimony layer was deposited by MBE (molecular beam epitaxy) compared with a layer formed by thermal evaporation. The use of high vacuum is essential in order to observe any Sb induced crystallization at all. In addition it is necessary to take measures to limit the evaporation of the antimony.     

A CUMULATIVE FATIGUE DAMAGE RULE UNDER THE ALTERNATIVE OF CORROSION OR CYCLIC LOADING

Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic loading was proposed. The specimens of aluminum alloy LY12-CZ soaked in corrosive liquid for different times were tested under the constant amplitude cyclic loading to obtain S-N curves. The test was carried out to verify the proposed cumulative fatigue damage rule under the different combinations among corrosion time, loading level, and the cycle numbers. It was shown that the predicted residual fatigue lives showed a good agreement with the experimental results and the proposed rule was simple and can be easily adopted.