中强和高强铝合金的疲劳裂纹扩展特性

本文研究2024（LY12）和7075（LC4）合金的疲劳长、短裂纹扩展特性，包括裂纹扩展速率、名义门槛植、本征门槛值、裂纹闭合效应、尾迹效应．2024合金有优良名义疲劳裂纹扩展抗力和高的名义门槛值，然而又有强的短裂纹效应，归因于其高的裂纹闭合效应和裂纹闭合效应的尾迹依赖性．7075合金的本征门槛值高和短裂纹效应弱，在近门槛值区有高的本征疲劳裂纹扩展抗力．同时．探讨疲劳裂纹扩展抗力、门槛值与断裂特征的关系．     

8090铝锂合金非扩展物理短裂纹的研究

采用CT试样,研究了8090铝锂合金二维穿适短裂纹的扩展行为,重点探索了物理短裂纹尺寸上界值、门槛值、裂纹闭合效应与其非扩展倾向的关系。研究结果表明,当该合金物理短裂纹在一定的恒载幅条件下扩展时,K_(op)的增大率超过K_(ma)的增大率,进而导致dα/dN因ΔK_(eff)下降而下降,由扩展短裂纹转变为非扩展短裂纹。合金的长裂纹门槛值ΔK_(th)和物理短裂纹尺寸上界值Δαr可作为衡量物理短裂纹非扩展倾向的尺度,ΔK_(th)愈高和Δαr愈低,其非扩展倾向愈强。     

基于裂纹闭合效应的疲劳裂纹扩展特性研究

依据线弹性力学理论对30NCD材料的裂纹扩展特性进行了研究,研究表明Paris公式能够很好地描述疲劳裂纹稳定扩展阶段的疲劳裂纹扩展速率da/d N与应力强度因子幅度ΔK之间的关系,稳定扩展段的疲劳裂纹扩展参数m=2.5~4,与绝大多数金属材料的疲劳裂纹扩展参数m=2~4的统计结果相符;NASGRO公式能较好地描述该材料从疲劳裂纹门槛值到高速裂纹扩展速率范围内的3种应力比的da/d N与ΔK关系。由裂纹闭合效应获得的有效应力强度因子范围与da/d N的关系表明:3种应力比下的所有数据都较好地关联在同一曲线上,裂纹闭合是引起应力比和裂纹扩展速率相关的主要原因,随着应力比增加,裂纹闭合程度减弱。     

软岩巷道在周边爆破反复作用下的损伤疲劳破坏

本文分析了软岩巷道围岩在远区爆破弱应力波反复作用下的损伤疲劳破坏机理,认为：岩石在周期性荷载作用下会产生疲劳损伤,所引起的力学性能变化对岩体工程的长期稳定性有重要影响;岩石的疲劳破坏存在门槛值,只有在局部应变或损伤疲劳累积达到疲劳裂纹扩展门槛时,疲劳裂纹才会形成和扩展;岩石疲劳裂纹的起裂韧度比其断裂韧度小得多,因此岩石会在远低于其断裂韧度的循环应力作用下发生疲劳损伤破坏.     

应力比对热等静压Ti-6Al-4V钛合金疲劳裂纹扩展速率的影响

采用标准C(T)试样测定热等静压Ti-6Al-4V钛合金在应力比R=0.1、0.4和0.7的条件下疲劳裂纹扩展速率,获得相应条件下的疲劳裂纹扩展数据,绘制了对应的裂纹扩展速率与应力场强度因子(da/dN-ΔK)关系曲线,并结合疲劳裂纹扩展路径和断口形貌分析探究应力比R对热等静压Ti-6Al-4V钛合金裂纹扩展速率的影响。结果表明,随着应力比R的增大,裂纹扩展门槛值ΔKtn减小。相同ΔK下,裂纹扩展速率da/dN随应力比R一同增大,致使da/dN-ΔK关系曲线向左上移动;裂纹能够穿过等轴晶α相和纤薄的α片层结构呈直线型扩展,遇到较厚的α片层结构时,裂纹偏转并沿原始α片层方向继续扩展,最终发生断裂;断口由预裂区、稳态扩展区和快速断裂区构成,分别对应于疲劳裂纹扩展的三个阶段。     

微小疲劳裂纹的闭合现象及疲劳强度的评价（Ⅲ）

本研究对从预裂纹处萌生的疲劳裂纹的塑性诱发裂纹闭合现象进行了解析,裂纹的张开应力强度因子可近似地用负荷应力及裂纹扩展量的函数来表示。采用带有微小表面预制裂纹和边缘预制裂纹的中碳钢试验片进行了疲劳实验。用激光干涉应变－位移测量仪（ISDG）进行了裂纹闭合点的高精度动态测量。利用裂纹扩展阻力曲线法预测了预裂纹试验片的疲劳门槛值条件,所预测的值与试验结果相当吻合。     

航空2024铝合金VIC-3D静载分析和疲劳试验

通过VIC-3D技术测量静态拉伸全场二维应变及应力,基于航空载荷谱进行动态载荷疲劳试验,利用扫描电子显微镜对试件断口进行观察,研究航空2024铝合金的力学性能。结果表明,利用Y方向应变随时间变化云图,可以探究裂纹出现及发展规律,疲劳试样在第34周循环,总第169 973次循环后发生疲劳断裂。疲劳断口可观察到疲劳源区、疲劳裂纹扩展区及瞬时断裂区,并呈扇形向外扩展。疲劳裂纹萌生于试件表面,裂纹扩展区二次长裂纹方向和裂纹扩展方向垂直,并存在疲劳辉纹,瞬时断裂区呈现出塑性断裂韧窝状形貌,局部存在冲击面形貌。     

航空2024铝合金VIC-3D静载分析和疲劳试验VIC-3D Static Analysis and Fatigue Test of 2024 Aluminum Alloy 陈亚军 黄彦 薛程丹 洪建国

为系统研究航空2024铝合金的力学性能,首先通过VIC-3D技术测量静态拉伸全场二维应变及应力,其次基于航空载荷谱进行动态载荷疲劳试验。VIC-3D结果表明,利用Y方向应变随时间变化云图,可以探究裂缝出现及发展规律;采用运输类飞机下翼面标准载荷谱TWIST,疲劳试样在第34周循环,总第169973次循环后发生疲劳断裂。利用扫描电子显微镜对试件断口进行观察,疲劳断口可观察到疲劳源区、疲劳裂纹扩展区及瞬时断裂区,并呈扇形向外扩展。疲劳裂纹萌生于试件表面;裂纹扩展区二次长裂纹方向和裂纹扩展方向垂直,并存在疲劳辉纹;瞬时断裂区呈现出塑性断裂韧窝状形貌,局部存在冲击面形貌。     

含稀土铝锂合金的分层韧化及数学分析

从宏观性能与断口微形貌角度研究了２０９０＋Ｃｅ合金时效过程中的韧化剂,１５００℃时效比１６３℃时效具有更佳的断裂韧性,归因于其高的层内韧化水平。;裂纹扩展过程中,继口主断裂面塑变迹象减弱,短横向分层程度增大,分层韧化机制不断加强,整个韧化机制在此过程中产生相应改变。     

微小疲劳裂纹的闭合现象及疲劳强度的评价(Ⅰ)

通过对碳素结构钢（JIS－S45C）和高强度低合金钢（JIS－SNCM439）两种材料的边缺口试验片的周向拉压疲劳试验,用裂纹闭合的观点研究从缺口顶端萌生的微小疲劳裂纹的扩展现象。运用裂纹扩展抵抗阻力曲线法（R曲线法）对缺口试验片的疲劳强度进行了评价。包括裂纹的萌生极限、断裂极限以及停止扩展裂纹长度的预测值与实验结果吻合。     

Current situation and future trend of China rare earth luminescent material industry

<正>Rare earth luminescent material is one of the most important application sectors of rare earths.China enjoys the exceptional advantage to develop rare earth luminescent material for its abundant rare earth resources.After several decades'endeavor,China's rare earth luminescent material industry,headed by rare earth phosphor for lamp and LED and high efficient rare earth energy-saving light source,has been gradually developed into a scale industry.China has become a major production base of rare earth phosphor for lamps and rare earth     

China rare earth market review

正June 1~10,2014Rare earth market remained weak.Quoted price of rare earth products was similar to that in May.There was no sign of recovery in downstream market.The market of NdFeB magnetic materials and phosphor was depressed.Catalyst,polishing powder and ceramic industries remained inactive.Demand from downstream industry was soft.Consumers purchased on their needs.Suppliers had strong intention to sell.Prices of rare earth products     

Annual Report analysis of Chinese rare earth-related listed companies in 2013

<正>Chinese rare earth-related listed companies have published their 2013 annual reports.It can be understood from their reports that production and operation activities of Chinese rare earth-related companies were still heavily affected by macro economy and industrial policies.They basically followed the steps of national economy.In 2013,world economy recovered slowly but the economy     

Market opportunities and challenges for rare earth polishing powder

正1.Status of rare earth polishing powder Rare earth polishing powder with high content of cerium oxide began to replace iron oxide for glass polishing and became one of the key materials in glass polishing process since 1940.Compared with traditional iron oxide,rare earth polishing powder has many advantages,such as fast polishing rate,high polishing quality and long service life.It can achieve good surface quality and improve operation conditions.For example,in lens polishing,the polishing work that cerium     

Baotou Research Institute of Rare Earths developed a new RE alloy preparation technology

正Pyrometallurgy Laboratory of Baotou Research Institute of Rare Earths had independently developed a new preparation technology of rare earth alloy for NdFeB.The alloy can remarkably enhance the coercivity of NdFeB magnet but also evidently reduce the production cost of the magnet.The new master alloy was prepared in the kA pilot-scale electrolytic cell by the independent technology.The rare earth master alloy can be used as the raw material for NdFeB.Compared     

Market and recycling of NiMH battery

<正>Market status and future trend of NiMH battery1.Global market of small NiMH battery Global market size of small NiMH batteries declined year on year since 2011.The trend will continue to 2018,at the rate of 5%to 10%annually.Demand for small NiMH batteries will be stable gradually.Many electrical apparatuses are powered by the built-in lithium battery today,which is the main reason for the shrunk market of small NiMH batteries.But,for some products,small NiMH     

China rare earth market review

正September 1-10,2014 Affected by the National Day holiday,rare earth transaction was stagnant and the market showed a weak steady state.As there was no good news for downstream market,some products with flat demand would likely rally slightly for some time to     

2014 second batch of rare earth quota released

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矿用防爆轴流对旋主要通风机叶片ANSYS模态分析及应用

高效节能矿用防爆对旋主要通风机的叶片是主要通风机运行的关键部件,叶片在运行时不断受到气流的作用力,从而使叶片产生振动,当叶片振动的频率与叶片的固有频率接近时,容易产生共振从而导致叶片的断裂。一旦叶片断裂时,对主要通风机的安全运行产生致命的影响,从而导致矿山、化工等企业发生重大事故,将会产生不可估量的损失。基于有限元分析软件ANSYS,对高效节能矿用防爆轴流对旋主要通风机叶片进行模态分析及产生对应的六阶模态频率,对主要通风机叶片的运行频率、固有频率及产生的共振问题进行了原理分析,并且解决了叶片频率共振的问题,从而为主要通风机叶片结构设计提供理论依据,并对主要通风机叶片的安全运行提供保障。     

2013 NdFeB export analysis

<正>China totally exported nearly 24,000 tonsof NdFeB products during 201 3,including 18,825 tons of permanent magnet,valued USD 1.34 billion at an average price of 71.4 USD/kg;3,277 tons of NdFeB magnetic powder,valued USD 1 01 million at an average price of 30.9 USD/kg;1,334 tons of strip casting ribbon,with total export value of USD 74million at an average price of 55.3 USD/kg;and 586