高载荷条件下TC17钛合金低周疲劳和保载疲劳损伤行为研究

研究了高应力水平下不同加载波形对TC17钛合金疲劳损伤的影响,结果表明,对于在峰值应力处保载120S的加载波形,TC17钛合金的保载疲劳寿命低于无保载加载波形试验的寿命,在相同的保载疲劳条件下,片层组织的保载疲劳敏感性较等轴组织的疲劳敏感性低。断口分析表明,保载疲劳试样裂纹源出现在样品表面和亚表面处,常规疲劳试样裂纹源出现在试样表面处,保载疲劳断口较常规疲劳断口附近小平面平坦,保载条件并未从根本上改变断裂模式。     

螺栓疲劳断裂失效分析

通过宏微观断口形貌分析、化学成分分析、金相组织分析等手段,分析了螺栓断裂的原因.结果表明:螺栓疲劳断裂主要原因是螺栓表面脱碳层所导致的螺栓表面弱化,加速了疲劳裂纹源的形成,从而加速了疲劳断裂过程.     

铝型材挤压机张力柱疲劳断裂失效分析

分析了８ＭＮ铝型材挤压机张力柱疲劳断裂失效的原因，提出预防与改善的措施，对类似的压机导柱，注塑机拉杆疲劳断裂失效有同样的参考价值。     

电机轴疲劳断裂失效分析

通过扫描电镜（SEM）,能谱（EDS）和金相分析等方法对电机轴疲劳断裂失效原因进行了分析,发现疲劳裂纹源为轴表面的环状切削加工痕迹,轴表面的堆焊层,钢中硫化锰含量过高以及未按要求进行调质处理等因素加速了电机轴的疲劳断裂过程。     

关于两起工程机械设备早期疲劳失效的分析及探讨

通过宏观分析、扫描电镜、光学显微镜等手段对装载机车架及液压挖掘机的液压泵驱动轴的早期断裂进行了综合分析,结果表明均为制造工艺不当而诱发的疲劳断裂失效,同时对有关防范措施作了探讨。     

飞机框架结构件振动疲劳失效分析

某ZL205A铸造铝合金飞机框架结构件在经过技术标准下的振动试验后发生断裂失效,通过宏观视察、X射线探伤、荧光渗透无损检测、断口形貌观察、微观组织分析、化学成分分析、力学性能测试等手段对该中层支架进行失效分析。结果表明,倒角部位近表面疏松的铸造缺陷是导致疲劳断裂的主要诱因。铝合金铸造疏松的几何尺寸及其呈现的空间树突状结构特点,对于疲劳裂纹的萌生和扩展有着特殊影响。     

氢对Ti-2Al-2.5Zr钛合金疲劳性能的影响

研究了4种含量的氢对Ti-2Al-2.5Zr钛合金疲劳性能的影响。结果表明，自然含氢量的材料具有最好的疲劳性能。而当疲劳载荷大于材料的屈服强度时，氢含量对疲劳寿命基本没有影响；低于屈服强度后，疲劳寿命随着氢含量的升高而和。认为固溶的原子氢导致驻留滑移带软化，裂纹萌生提前，造成在较大△σ时充氢试样的疲劳寿命降低；而材料中氢化物对驻留滑移带（PSB）的阻碍作用导致氢化物与基体分离 而成为裂纹源，是小△σ下疲劳寿命降低扩要原因。     

TC11钛合金在疲劳—蠕变交互作用下的解理断裂研究

研究了具有等轴、双态和网篮三种组织的TC11合金在520℃下的疲劳—蠕变交互作用特性,发现在断裂过程中出现的解理特征不仅与蠕变空洞形核率有关,而且受拉伸保时过程中裂尖蠕变应变累积和裂尖应力状态的控制,即受临界空洞形核应变和临界空穴扩张比参数V_(GC)的综合影响。     

风电齿轮箱行星齿轮疲劳断裂失效分析

研究了825 kW风电机组齿轮箱运行5年后出现行星齿轮疲劳断裂的问题。通过对断裂齿轮进行化学成分、显微组织、宏微观断口分析以及力学性能、断裂韧性检测的试验分析,查明齿轮发生疲劳断裂的原因。结果表明：行星齿轮的断裂是多源疲劳裂纹萌生和扩展行为,齿轮内圈沟槽存在初始加工缺陷,负载较大时出现应力集中;齿轮的表面与心部硬度的离散性较大说明存在热处理与表面渗碳等工艺问题;此外长期满负荷运行和过载冲击加速了疲劳裂纹的扩展,导致齿轮箱疲劳寿命降低。     

The effects of gas nitriding on fatigue behavior in titanium and titanium alloys

Fatigue behavior has been studied on gas-nitrided smooth specimens of commercial pure titanium, an alpha/beta Ti-6Al-4V alloy, and a beta Ti-15Mo-5Zr-3Al alloy under rotating bending, and the obtained results were compared with the fatigue behavior of annealed or untreated specimens. It was found that the role of the nitrided layer on fatigue behavior depended on the strength of the materials. Fatigue strength was increased by nitriding in pure titanium, while it was decreased in the Ti-6Al-4V and Ti-15Mo-5Zr-3Al alloys. Based on detailed observations of fatigue crack initiation, growth, and fracture surfaces, the improvement and the reduction in fatigue strength by nitriding in pure titanium and both alloys were primarily attributed to enhanced crack initiation resistance and to premature crack initiation of the nitrided layer, respectively.     

The effects of spark anodizing treatment of pure titanium metals and titanium alloys on corrosion characteristics

This study evaluated the surface characteristics of oxide films on commercially pure titanium metals (CP-Ti; Grade 2 and Grade 3) and titanium alloy (Ti6Al4V and Ti6Al7Nb) samples formed by an anodic oxidation treatment, and investigated the effects of anodization on the corrosion characteristics. FE-SEM, XRD, and Raman spectroscopy were used to evaluate the micromorphology and crystalline structure of the oxide films. The corrosion resistance of the sample groups was evaluated using open-circuit potential and cyclic polarization tests. After anodic oxidation up to dielectric breakdown with the same electric current, 150-200 nm-sized pores were distributed homogeneously on pure titanium metal samples, partially occluded pores were observed on the Ti6Al4V alloy, and there was an inhomogeneous size and distribution of pores on the Ti6Al7Nb alloy. The titanium dioxide films formed through anodic oxidation contained a phase mixture of anatase and rutile. The cyclic polarization tests showed that all the tested sample groups were not susceptible to localized corrosion. The as-received and anodically oxidized CP-Ti grade 3 groups showed a higher corrosion resistance than the other groups. The mean E_corr values of the anodically oxidized sample groups, except for the anodized Ti6Al7Nb alloy, showed higher values than those of the respective as-received sample groups. In particular, the Ti6AL7Nb alloy showed a statistically higher E_corr value in the anodized group than in the as-received group (p < 0.05).     

Effects of hydrogen on fatigue life of Ti-4Al-2V titanium alloy

1　INTRODUCTIONFewresearcheshaveplacedontheregionofhy drogen influenceonfatiguepropertiesoftitaniumal loys .Becausetheeffectsofhydrogenonpropertiesoftitaniumaredifferentfromthoseonsteel,plusthattitaniumalloysarehydrogenstoragematerials ,theeffectsofhydrogenarequitecomplex .AlthoughthefunctionsoffatigueloadingsΔσamplitudefortheini tiationandpropagationoffatiguecracksofhydrogenchargedtitaniumalloyshavenotbeenreported ,alotofstudies[1,2 ] ofthosefunctionsonstaticloadingshavebeenmade .Willi…     

驻留时间和加载速率对无铅焊点低周疲劳行为的影响

在25 ℃下利用单轴微力疲劳试验机对96.5Sn-3Ag-0.5Cu无铅焊点进行不同驻留时间(1~20 s)和不同应变速率(0.01~0.08 mm/s)条件下的低周疲劳试验. 结果表明,在25 ℃下1~20 s的驻留时间对焊点的疲劳寿命影响不大;随着应变速率的加快,焊点的疲劳寿命逐渐降低,断裂机制逐渐由延性断裂向脆性断裂转变. 不同应变速率条件下的疲劳裂纹主要在焊点边缘钎料与金属间化合物(IMC)之间的界面处萌生,并在近IMC层的钎料内扩展. 焊点断口主要分为:裂纹扩展区和最终断裂区.     

TC4钛合金电子束焊接头低周疲劳性能与断裂行为

文中比较了30 mm厚TC4电子束焊接头和母材的低周疲劳性能。试验结果表明,母材的低周疲劳性能稍优于接头,母材和接头的应变疲劳极限分别为0.49%和0.44%。对接头的疲劳断裂位置进行了观察,接头的疲劳断裂位置在焊缝。对接头和母材的疲劳断口进行了观察,疲劳裂纹源均出现在试样表面,疲劳裂纹扩展区均发现典型的疲劳辉纹,但接头的辉纹间距要小于母材,最后拉伸断裂区均发现韧窝,为韧性断裂。最后运用高分辨SEM对接头的组织进行了研究,母材为典型的双态组织,主要是由等轴α相和晶间β相构成,热影响区等轴α相边缘逐渐溶解,转变成较多的层状α’相,焊缝主要是由针状α’相组成的网篮状组织构成。     

Fretting fatigue studies of titanium nitride-coated biomedical titanium alloys

Fretting fatigue is an adhesive wear mechanism caused by repetitive tangential micro-oscillation between two contacting materials pressed together under cyclic load. Bioimplants, such as hip joints and bone plates, are prone to undergo fretting fatigue failures during their service within the body. This article presents the fretting fatigue damage characterization of physical vapor deposition (PVD) TiN-coated biomedical titanium alloys (Ti-6Al-4V and Ti-6Al-7Nb) subjected to cyclic loads. The PVD TiN layer delayed the damage because of superior tribological properties compared with uncoated alloys. Delamination and abrasive wear damage of TiN at contact caused failure of the alloy. Friction coefficient curves of the PVD TiN-coated pair showed an irregular pattern caused by the influence of wear particulates and Ringer fluid at the contact.     

钛合金及其成形技术在民品中的应用前景

对国内外近年来钛合金及其成形技术进行了介绍，分析了民品应用钛合金的障碍，提出了钛合金近净成形技术的发展将会有效地推动钛合金在民品中的应用。     

Effect of welding conditions on the impact toughness of welded joints in titanium alloys

Effect of the welding conditions and annealing on the impact strength of different heat-affected areas of the titanium welded joints is studied. Maximum impact strength is established in the range of 350–550°C, in practice this coincides with the temperature peaks for short-time strength and fatigue life.     

ADC12铸造铝合金齿轮箱开裂原因分析

采用微观扫描、化学成分、硬度及金相检验等方法对ADC12铸造铝合金齿轮箱开裂的原因进行了分析。结果表明,齿轮箱是由于内部存在较多的针状β(Al9Fe2Si2)脆性相和较集中分布的显微疏松孔隙,增加了压铸铝合金的脆性,降低了材料的承载强度,致使齿轮箱零件在承受外力载荷和装配定位销应力共同作用下,过早产生疲劳断裂失效。