20SiMn低合金钢和0Cr13Ni5Mo不锈钢的多相流损伤行为

对水轮机用金属材料20SiMn低合金钢和0Cr13Ni15Mo不锈钢进行旋转圆盘仪空蚀和冲刷磨损单元和组合多相流损伤实验。结果表明，20SiMn低合金钢和0Cr13Ni15Mo不锈钢的冲刷磨损及空蚀和冲刷磨损联合作用损伤累积质量损失－时间曲线均呈线性关系，空蚀和冲刷磨损联合作用对材料造成的损伤显著高于空蚀和冲刷磨损单独作用，空蚀和冲刷磨损的交互作用在空蚀和冲刷磨损联合作中起重要的作用；在空蚀和冲刷损联合作用中，液体空化及随后的空泡溃灭改变了流体中固相颗粒的运动方向，引起固相颗粒的流速增加和攻角改变，从而加剧了固相颗粒对材料表面的损伤。     

风沙两相流条件下沟槽形态对混凝土壁面抗风蚀磨损性能的影响

采用RNGk-ε湍流模型结合DPM离散相模型,在不改变材料性能条件下数值模拟了混凝土壁面的抗风蚀磨损性能,并进一步分析了槽壁倾斜角度和槽体深度变化对壁面抗风蚀磨损性能的影响。研究结果表明:在低冲蚀角度条件下,沟槽形态壁面较易出现风蚀破坏的集聚分布,而在高冲蚀角度条件下,壁面整体的抗风蚀磨损性能得到提升;槽壁倾角的改变会影响沟槽轮廓对槽体区域的遮蔽效能和沙砾首次撞击该区域的角度,进而改变壁面抗风蚀磨损性能;沟槽倾斜角度一定时,沟槽加深可增大沟槽区域占壁面面积的比率,从而增强壁面整体的抗风蚀磨损性能,但此手段不能有效扩展用于沙砾减速降能的低速流场。     

18CrNiMo7-6合金钢的弯曲微动疲劳特性

对18CrNiMo7-6合金钢进行弯曲微动疲劳实验,建立弯曲微动疲劳S-N曲线,并对实验结果进行分析。结果表明:该合金钢的弯曲微动疲劳S-N曲线不同于中碳钢材料,也不同于常规弯曲疲劳,而是呈"ε"型曲线特征。随着弯曲疲劳应力的增加,微动运行区域由部分滑移区向混合区和滑移区转变,损伤区的磨损机制以剥层、磨粒磨损和氧化磨损为主。在混合区内,裂纹最易萌生和扩展,且裂纹均萌生于材料接触区次表面。受接触应力和弯曲疲劳应力影响,弯曲微动疲劳裂纹的萌生和扩展可分为三个阶段:初期,在接触应力控制下,裂纹萌生于次表面;随后,裂纹受接触应力和弯曲疲劳应力共同控制,转向更大角度方向扩展;最后,裂纹完全受弯曲疲劳应力控制而垂直于接触表面扩展,直至断裂失效。     

基于有限元的固液两相射流冲刷磨损率数值研究北大核心CSCD

利用数值模拟方法研究了不锈钢受到固液两相射流冲蚀作用后发生的磨损过程,对不同粒径的试样进行了磨损率测试。结果表明:流体在喷嘴出口部位的速度约等于10 m/s,当流体与面板发生撞击后便会流向下游,在射流喷嘴口附件存在一个明显的压力较高的滞止区域。下游区域磨损率明显高于上游区域,并且与圆心距离越远的地方冲刷磨损率也越大,之后逐渐降低。当流体与冲蚀壁面接触之后便会流向下游区域,对下游区域造成较大的冲蚀作用,使下游产生较大的冲刷磨损率。越靠近下游区域,冲蚀磨损率表现为先增大后降低的现象,越靠近上游磨损率越小。平均冲刷磨损率和射流速度呈指数关系。     

基于有限元的固液两相射流冲刷磨损率数值研究

利用数值模拟方法研究了不锈钢受到固液两相射流冲蚀作用后发生的磨损过程,对不同粒径的试样进行了磨损率测试。结果表明:流体在喷嘴出口部位的速度约等于10 m/s,当流体与面板发生撞击后便会流向下游,在射流喷嘴口附件存在一个明显的压力较高的滞止区域。下游区域磨损率明显高于上游区域,并且与圆心距离越远的地方冲刷磨损率也越大,之后逐渐降低。当流体与冲蚀壁面接触之后便会流向下游区域,对下游区域造成较大的冲蚀作用,使下游产生较大的冲刷磨损率。越靠近下游区域,冲蚀磨损率表现为先增大后降低的现象,越靠近上游磨损率越小。平均冲刷磨损率和射流速度呈指数关系。     

纤维取向对炭纤维织物复合材料扭动微动摩擦学性能的影响

以球/平面接触方式,进行炭纤维织物复合材料与GCr15钢球之间的扭动微动磨损实验研究,讨论纤维取向对微动磨损性能的影响。结果表明:该材料与金属材料类似,均存在3个微动运行区域,即部分滑移区、混合区以及滑移区,微动磨损机制为磨粒磨损和氧化磨损。炭纤维复合材料微动摩擦磨损性能表现出明显各向异性特征,即纤维平行且垂直于接触表面的纤维混合排布(N取向)复合材料的摩擦耗散能和磨损量均小于纤维平行于接触表面的P取向。在混合区域,磨损区半径随循环周次的增加而逐渐增大,且N取向小于P取向。     

激光熔敷钴合金涂层的抗空蚀和冲刷磨损性能

采用激光熔敷方法在20SiMn低合金钢表面制成了Co合金涂层，以两种目前水轮机转用材20SiMn低合金钢和0Cr13Ni5Mo不锈钢作为对比材料，对涂层进行了空蚀，液固两相流冲刷磨损及空蚀和冲刷磨损联合作用实验，采用失重法并结合能谱分析，X射线衍射分析及显微硬度测量等手段研究了涂层的显微结构和在不同形式损伤下涂层的性能并分析了原因。结果表明：在20SiMn低合金钢表面激光熔敷形成的Co合金涂层有良好的抗空蚀性能，这与涂层在空蚀过程中发生的应力诱发马氏体相变密切相关。良好的抗空蚀性能有利于提高涂层抗空蚀和冲刷磨损联合破坏，从而使涂层表现出与0Cr13Ni5Mo不锈钢接近的抗联合损伤性能。     

低温离子渗氮提高2Cr13不锈钢的冲蚀磨损与冲刷腐蚀抗力

采用喷射式固体粒子冲蚀磨损实验机和浆体冲刷腐蚀装置对比研究了350℃低温离子渗氮和550℃常规高温离子渗氮对2Cr13不锈钢冲蚀磨损和冲刷腐蚀行为的影响规律,通过组织结构分析、硬度测试和电化学交流阻抗分析探讨了低温渗氮改善2Cr13不锈钢抗冲蚀磨损和抗冲刷腐蚀性能的机制。结果表明：低温和常规高温离子渗氮均可提高2Cr13不锈钢在小角度固体颗粒干冲蚀条件下的冲蚀磨损抗力,但是,350℃低温渗氮处理表现出比550℃高温离子渗氮层更好的抗冲蚀磨损性能。在含10%石英砂的中性和酸性5%NaCl水溶液中,350℃低温渗氮处理使2Cr13不锈钢冲刷腐蚀速率分别降低96.7%和87.4%;然而,550℃常规离子渗氮却导致2Cr13不锈钢冲刷腐蚀速率分别提高4.13倍和0.49倍。350℃渗氮层由-εFe3N和N过饱和固溶体αN相组成,其化学稳定性好,硬度高,因而表现出良好的耐腐蚀、抗冲刷磨损与抗冲刷腐蚀性能。550℃渗氮处理时,αN相分解成了α相和CrN化合物,造成基材贫Cr,耐腐蚀性能下降,同时表面硬度低于350℃低温渗氮层,其抗冲蚀磨损性能不及350℃低温渗氮处理,冲刷腐蚀抗力则低于2Cr13不锈钢基材。     

不锈钢材料高温冲蚀磨损性能与机理

为弄清磨粒对工业设备常用材料304不锈钢的冲蚀磨损情况,采用自行设计的气流喷砂式高温磨损试验机,对其进行不同温度下的冲蚀磨损。分析了温度、冲蚀角度、磨粒粒径以及磨粒速度对其冲蚀磨损率的影响,并分析了其冲蚀磨损机理。结果表明:温度对冲蚀磨损率有显著影响,304不锈钢表面氧化膜在400℃时抑制了磨粒的冲蚀,高温下金属塑性升高降低了高角度下磨料的冲击破碎作用,但低角度下抗微切削能力下降;冲蚀磨损率随磨粒粒径的减小先增大后减小再增大,随磨粒速度增大而增大;磨粒对试样表面的低角度微切削和高角度冲击破碎作用是材料冲蚀磨损的主要机理,304不锈钢表面的冲蚀磨损主要来源于微切削作用。     

两种高铬铸铁在热强碱中受冲刷时的腐蚀行为

为考察不同材料在热强碱中的腐蚀和磨损腐蚀行为，用电位线性扫描方法测定了Cr13和Cr26两种高铅铸铁在静态和动态的模拟介质中的极化曲线．研究结果表明：动态条件下的腐蚀电流密度比静态条件下约大两个数量级；在动态冲刷条件下，铸铁材料的表面始终处于活化状态，磨损腐蚀速率远大于纯腐蚀速率；Cr26抗磨损腐蚀的性能优于Cr13．     

Abrasion predictions for Francis turbines based on liquid–solid two-phase fluid simulations

The runner blades and guide vanes of Francis turbines are worn by sediment in the flow. However, there are few studies about abrasion of the runner blade and guide vane for normal turbine operating conditions. This study investigated the relation between the wear rates on the surfaces of the runner blade and guide vane and the sediment concentration, and analyzed the distribution of the wear rates for normal turbine operating condition. An Eulerian–Lagrangian Computational Fluid Dynamics (CFD) procedure was used to simulate steady liquid–solid two-phase flow for various operating conditions. The Finnie model was then used to predict the abrasion. The conditions leading to abrasion in the inner flow passage components of a Francis turbine are clarified through analysis of the abrasion conditions for the runner blades and guide vanes. Field tests and simulations show that the relative wear rate on the runner blades and guide vanes increases with increasing sediment concentration, and the maximum wear on the runner blades occurs in a small opening region with the maximum increasing as the head increases. The maximum wear on the guide vanes occurs at the maximum output and the relative wear rate on the runner blades is much greater than that on the guide vanes. There is no good data, so the relative wear rates on the runner blades and the guide vanes can only be obtained numerically. Thus actual wear rates cannot be given and are beyond the scope of this paper. This paper shows the abrasion characteristics on the runner blades and guide vanes with sediment flow and provides reference data for predicting the abrasion conditions in the flow passage components of a Francis turbine.     

粗晶TM52钢结硬质合金的冲击磨料磨损性能研究

系统对比研究了粗晶粒TM52钢结硬质合金与分别采用真空烧结和低压烧结制备的细晶粒TM52钢结硬质合金在不同冲击功工况下的抗磨料磨损性能与行为,并在对磨损面形貌进行电镜观察分析的基础上探讨了粗晶粒TM52钢结硬质合金的磨损机理。研究发现,粗晶TM52合金的抗磨料磨损性能随着冲击功的逐步提高呈现先下降后增强的变化规律,这与其高锰钢基体在高冲击功条件下的高硬化速率及硬化效果更快、更充分有关。相对于细晶粒钢结硬质合金,粗晶粒TM52钢结硬质合金在抗冲击磨料磨损方面具有明显的性能优势,尤其在高冲击功(3~4J/cm~2)条件下,耐磨性能可提高40%~80%。在此工况下磨损机制主要为碾碎性磨料磨损、擦伤式磨料磨损和疲劳磨损,凿削式磨料磨损不明显。     

Study on three-body abrasive wear behavior of functionally graded Al/TiB2 composite using response surface methodology

Functionally graded LM13 Al/10?wt% TiB₂ metal matrix composite has successfully produced under centrifugal casting. Hollow cylindrical composite with dimensions 150?×?150?×?15?mm was produced under rotating centrifugal speed of 1100?rpm. Microstructural characteristics were studied on the composite surfaces at distance of 1, 5.5, and 10?mm from outer periphery of the casting, and the results revealed that surface at distance of 1?mm has presence of more reinforcement particles. An objective of this study was to characterize abrasion wear behavior at the composite surfaces using dry abrasion tester. Mathematical models were developed using response surface methodology to study the relationship of parameters such as load, speed, and distance from outer periphery with abrasion wear rate. Face centered Central Composite Design with 20 experiments was preferred for dry abrasion test. Adequacy of model was predicted through analysis of variance, and the significance test result shows that load has major impact on the wear rate. The optimized parametric condition to obtain minimum wear rate was found as load of 33?N, speed of 112?rpm, and distance of 1?mm from outer periphery. Scanning electron microscopy analysis done at worn out surface showed maximum wear resistance at the outer periphery.     

Optimization design of axial fan blade

A series airfoil was obtained through optimization design which aimed to promote lift–drag ratio, and the new airfoil series was used to construct a blade. The chord length and installation angle of the blade along the blade height were optimized by using orthogonal optimization. Three design options (straight blades, C-type blades and forward swept blades) are examined in this paper. Taking an axial fan as the research object, the whole 3D numerical simulation was conducted by using Ansys-CFX. Axial fans with three kinds of blades are discussed and compared under design and off-design conditions. The present results show that: under design conditions, the total pressure efficiency of the axial flow fan with the forward swept blade is the highest, and the C-type blade has slightly lower efficiency while the straight blade has the lowest efficiency. Under off-design conditions, the aerodynamic performance of the forward-swept blade and C-type blade fans are better than that of the straight-blade fans.     

Oberflächenbeeinflussung von Modellschlagleisten durch Stoßkontakte mit Betonpartikeln

The influencing of the surface of an impeller bar pattern by impact contacting with concrete particles The wear appearing as a result of an impact strain by abrasion particels in an impact- crusher was simulate with a special test machine. With the impact wear test machine were investigated the effects of impacts at different groups of materials to investigate the wear behaviour versus the number of contacts. In view of the abrasive behaviour of the materials the tests demonstrate the necessitiy to consider the penetrating ability of the abrasive particels in the surface of the sample. By means of microphotos was developed a structural model for the abrasion of ductile areas of the material.     

Experimental-numerical investigation of the dynamic stability of flexural-torsional vibrations of compressor blades under conditions of attached and separated flow. part 3. mutual aerodynamic couplings

The paper considers the results of a study of mutual aerodynamic couplings which give rise to nonstationary aerodynamic interactions between the translational and angular components displacements of neighboring ring blades in the case of variation of attack angle, reduced vibration frequency and the geometric parameters of the blade cascade. The effect of mutual aerodynamic couplings between neighboring blades on the aerodynamic stability of flexural-torsional vibrations of the blades of the peripheral section of the shrouded fan blade ring of gas turbine engine for an attack angle of 15° has been estimated.     

冲击磨损工况下铁基耐磨材料的现状及发展

在破碎、研磨、挖掘等机械设备上,因其常常受物料的冲击磨损,导致耐磨件快速失效,每年耐磨件消耗量很大,如何实现耐磨性和经济效益的有机统一是人们关注的问题。而耐磨材料也在不断地发展,从第一代钢铁耐磨材料Mn13到第三代钢铁耐磨材料高铬铸铁,再到陶瓷颗粒增强复合材料,以应对不同磨损工况。冲击磨料磨损是一种较为复杂的磨损工况,要求材料具有较高的硬度,同时材料还要保持一定的韧性以抵抗冲击力。针对冲击磨损工况下铁基耐磨材料,介绍了国内外耐磨材料的发展现状,概述了从高锰钢到复合材料,再到复合结构的发展过程,总结了复合材料从基体的选择到增强颗粒的选择,及多种颗粒混合增强的研究进展,重点对陶瓷颗粒增强铁基复合材料及复合结构进行了较为全面的介绍,从软质基体包嵌硬质单元和硬质基体包嵌强韧网络单元两种复合方式进行分析,并对未来复合结构技术的发展进行展望。     

Sialon陶瓷的冲蚀磨损及磨粒磨损行为

以ＳｉＣ作为磨粒较全面地研究了Ｓｉａｌｏｎ陶瓷的磨损性能：冲蚀磨损和磨粒磨损性能．Ｓｉａｌｏｎ陶瓷在冲蚀磨损实验中表现出了脆性冲蚀的特征,在高角冲蚀下,冲蚀磨损率随着冲蚀角度的增大而迅速增加,并在冲蚀角为９０°附近达到最大．ＳＥＭ分析表明Ｓｉａｌｏｎ陶瓷的冲蚀磨损机理主要是显微切削和表面颗粒拔出脱落．在Ｓｉａｌｏｎ陶瓷的磨粒磨损实验中,较高载荷作用下,磨损量与时间之间有指数变化关系;较低载荷作用下,磨损初期有一个短暂的磨损量基本不变的孕育阶段,随后进入快磨损阶段,本文对该孕育现象进行了探讨．对磨损表面的ＳＥＭ分析发现;Ｓｉａｌｏｎ陶瓷的磨粒磨损机理主要是犁耕和表面断裂脱落．     

Finite-element simulation for modeling composite plates subjected to soft-body,high-velocity impact for application to bird-strike problem of composite fan blades

We presented a numerical simulation to address the impact-induced deformation and damage of composite plates subjected to soft-body, high-velocity impacts for application to the bird-strike problem of composite fan blades. A new stabilized contact algorithm was developed based on the Lagrange multiplier method to predict appropriate impact forces applied to the plate, in order to solve soft-body impact at high velocity without causing severe numerical instabilities. The bird-strike impact on composite fan blade was simply modeled by discussing the damage characteristics of a unidirectional composite plate. Combining the model of a soft-body impactor with an appropriate contact algorithm, we could capture the transition from the global bending mode at low velocity to the local deformation mode at high velocity, enabling a discussion of the ballistic limit using the damage analysis of the laminate. As the impact velocity increased, the damage in the composite changed from bending-induced matrix-cracking to an intensive fiber-breakage mode causing local shear perforation. The damage mode transition allows us to detect the transition velocity as a ballistic limit, which is one of the critical factors for discussing the bird-strike resistance of composite fan blades.