五轴联动数控展成电解磨床原理与控制

为解决整体叶轮叶片型面的精加工难题,进行了五轴联动数控展成电解磨削整体叶轮的基础研究。根据数控展成电解磨削整体叶轮叶片型面这一加工方法的特点,在分析了数控展成电解磨削整体叶轮原理的基础上,对磨削系统的结构与运动进行了总体设计,提出了经济型多轴数控系统及其联动控制方法,建立了电解磨削非平行直纹展成曲面的数学模型,开发了五轴联动数控展成电解磨削自动数控编程系统,对航空发动机整体叶轮的叶片型面进行了电解磨削。五轴联动数控展成电解磨削技术为整体叶轮叶片型面的精加工提供了一种新的加工手段。     

吹砂、抛光及其电解腐蚀后处理对单晶高温合金表面组织和再结晶行为的影响

采用吹砂处理、砂带抛光、毡轮抛光3种表面处理使铸态单晶(SX)Ni基高温合金叶片表面形成塑性变形层,对叶片表面变形层进行电解腐蚀实验,然后进行标准热处理,研究了单晶高温合金叶片表面处理的变形层及其电解腐蚀后显微组织。结果表明:3种表面处理的铸态单晶高温合金叶片表面变形层深度分别约为6,3.5μm和2μm,并在吹砂处理和砂带抛光的表面变形层周围存在显微裂纹;表面变形层电解腐蚀过渡区内存在大量γ′变形组织,且3种表面处理的塑性变形残存量依次递减,而变形层完全电解腐蚀区内无塑性变形痕迹;标准热处理后,变形层未电解腐蚀区存在凹陷特征和再结晶晶粒,但无塑性变形痕迹;变形层完全电解腐蚀区无明显凹坑和再结晶晶粒。     

论冲压成型模具型面修复方法

通过对覆盖件模具表面进行数铣、焊接、激光淬火等工艺以恢复覆盖件模具的技术状态，从而确保整车的外观质量。通过cAE软件修复数模中原来存在型面磨损、R角变大等质量缺陷。利用修改完成的数模粗铣加工模具表面凹坑、凹凸不平等缺陷，试冲产品样件后对产品样件进行后续匹配，根据后续匹配样件存在的问题对模具进行全面修复，并对模具表面进行激光淬火加工。由此使得覆盖件的表面质量相比以前有大幅提升。     

镍基高温合金喷射液束电解-激光复合加工试验研究

针对镍基高温合金材料激光打孔存在再铸层的缺陷,创新提出了喷射液束电解-激光复合加工方法.基于该加工原理的分析以及激光在电解液中的衰减特性研究,研制了试验系统,并对镍基高温合金GH3044薄片进行了打孔工艺试验.结果表明:应用液压1.5MPa、浓度18%的NaNO2电解液的喷射液束电解-激光复合加工可去除再铸层90%以上.试验证实了喷射液束电解-激光复合加工工艺切实可行,有望在航空发动机叶片气膜孔加工中得到应用.     

航空发动机钛合金叶片抛光烧蚀问题解决措施

本文介绍了航空发动机钛合金叶片型面抛光加工工艺,烧蚀(伤)工程化检测方法,以及烧蚀(伤)后叶片表面状态,分析了产生烧蚀(伤)的原因,介绍了避免产生烧蚀(伤)问题所进行的一系列加工试验工作,通过对各种加工方法及参数的反复实验,总结提出了避免钛合金叶片型面抛光烧蚀(伤)问题的合理加工方法及参数,为钛合金叶片高质量高效率的加工总结了一定的经验。     

基于标准阴极特性的面齿轮阴极设计方法

目的 解决电解加工过程中,简单曲面阴极设计方法不能保证面齿轮加工精度的问题。方法 利用标准阴极进行正交试验,得出钢制面齿轮的最优电解工艺参数。利用该工艺参数对阴极重新设计,加工试件,根据试件的测量结果对原始阴极进行修形,得出最终阴极形状。结果 通过对正交试验数据进行处理,得出钢制面齿轮的最优电解工艺参数为K=20, U=10 V, v=0.6 mm/min;根据试件的误差测量结果,推导出最优修形数为0.4602。结论 此阴极设计方法所设计的阴极能保证面齿轮的加工精度,而且能够加工出IT7级精度制件,同时为复杂型面的高精度电解加工方案提供了一种可行的阴极设计方法。     

MEMS加工中对准误差的在线提取结构

对准误差是MEMS表面加工工艺中的一个重要参数,对它的测量和控制有着重要的意义.目前大多采用光机械的方法来测量,但是测试方法复杂、测试时间长.主要对MEMS表面加工工艺中导电层和非导电层之间的对准误差测试结构进行了研究,可用于测量表面工艺中牺牲层和多晶硅层之间的对准误差.通过对集成电路中所用的锥形梳状游标结构进行改进,把对准误差的测量转化为电阻的测量,从而实现对准误差的快速电测量,理论上可达到0.1μm的分辨率,测试方法简单快捷,并且很便于测试系统集成.     

磨削工艺对无损检测的影响

通过对叶片缺陷理化检测分析,确定了叶片的缺陷为铸造显微缩松,经过对叶片缺陷表面的各种加工工艺试验,发现了大磨削量对显微缩松的荧光检测有掩盖作用,其根本原因是在磨削力的作用下,导致缺陷通向检测表面的开口因材料变形而闭合。因此采用无切削力的线切割加工替代粗磨,并验证了电加工表面缺陷荧光检出率达到100％。     

银币表面缺陷分析及表面保护工艺研究

分析了我厂银币表面缺陷形成的原因，并提出了在银币表面施加保护膜的设想，通过各种防变色工艺实验，提出了采用电解保护和浸渍抗变色剂的多层组合防护膜保护工艺方案。实验表明，经过该保护工艺处理的银币自然放置半年无白斑及其他变色现象产生，在40℃，3mg/L硫化氢气体和3％硫化钾溶液中耐蚀时间为130min，分别为未经处理银币的耐蚀时间的10倍和26倍。     

汽车减振器连杆的耐蚀性研究

对用两种不同的电镀工艺制备的汽车减振器连杆进行了电解腐蚀试验,探讨了减振器连杆镀铬层点蚀的形成机理及其对连杆表面耐腐蚀性的影响。运用金相显微镜及扫描电镜观察腐蚀前后连杆的镀铬层组织,证实连杆的表面镀层缺陷是影响其耐腐蚀性的主要原因。电镀工艺中减小电流密度可以减小镀层裂纹宽度和深度,从而提高镀层的耐蚀性。     

Wear processes and performance of blade pair in small-scale single-shaft plastic shredder machine

Shredder blades and fixed blades were used as a set of blade pair to perform the shredding action. Comparable research was performed on the blade pair to understand its wear mechanism and shredding performance. The loading distribution along the two-edge shredder blades in helix configuration was identified. Optical microscopy, scanning electron microscopy, energy dispersive x-ray, x-ray diffractometer analysis, and hardness tests were used to characterise the surface, elemental composition, microstructure, and hardness of the worn blade pair. The shredder blades’ wear mechanism was categorised as progressive wear which dominant by abrasive, following by adhesive and oxidation wear. The shredding efficiency of the two-edge shredder blades in helix configuration was 69.24 %, recycling efficiency at 96.83 % and retention of 3.17 % after the shredding process.     

钛铝低压涡轮叶片熔模铸造精确成形及冶金缺陷分析

目的 研究不同浇冒口设置对TiAl低压涡轮叶片的成形的影响及叶片冶金缺陷形成的原因。方法 采用熔模精铸方法,通过设计顶注式重力铸造浇注系统,采用冷坩埚感应熔炼炉进行TiAl叶片浇注实验,采用目视和X射线检验方法分析叶片铸件表面及内部缺陷,并结合金属凝固理论分析缺陷形成原因。结果 合理的浇口和排气孔设置有效避免了因熔体流动性差造成的叶片充型不完整,以及凝固收缩导致的应力开裂等问题,浇注出成形完整的铸造叶片;叶冠与叶身端部转角部位充型凝固过程中形成热节,容易出现贯穿性疏松缺陷;树脂基熔模焙烧后残留的碳黑在熔体充型凝固过程中,与面层中的ZrO2反应生产CO,导致叶身出现聚集性皮下气孔;由于凝固收缩引起叶身与铸型分离,降低横向散热能力,导致叶盆部位出现表面疏松。结论 通过浇注合理的浇注系统设置可实现TiAl叶片完整充型,疏松缺陷控制为进一步提高叶片质量的关键。     

On the sharpness of straight edge blades in cutting soft solids: Part I - indentation experiments

The sharpness of a blade is a key parameter in cutting soft solids, such as biological tissues, foodstuffs or elastomeric materials. It has a first order effect on the effort, and hence energy needed to cut, the quality of the cut surface and the life of the cutting instrument. To date, there is no standard definition, measurement or protocol to quantify blade sharpness. This paper derives a quantitative index of blade sharpness via indentation experiments in which elastomeric materials are cut using both sharp and blunt straight edge blades. It is found that the depth of blade indentation required to initiate a cut or crack in the target material is a function of the condition or sharpness of the blade’s cutting edge, and this property is used to formulate a so-called “blade sharpness index” (BSI). It is shown theoretically that this index is zero for an infinitely sharp blade and increases in a quadratic manner for increasing bluntness. For the blades tested herein, the sharpness index was found to vary between 0.2 for sharp blades and 0.5 for blunt blades, respectively. To examine the suitability of the index in other cutting configurations, experiments are performed using different blade types, target materials and cutting rates and it is found that the index is independent of the target material and cutting rate and thus pertains to the blade only. In the companion Part II to this paper a finite element model is developed to examine the effect of blade geometry on the sharpness index derived herein.     

Numerical Simulation of Solidification Process on Single Crystal Ni-Based Superalloy Investment Castings

Bridgman directional solidification of investment castings is a key technology for the production of reliable and highly efficient gas turbine blades. In this paper, a mathematical model for three-dimensional （3D） simulation of solidification process of single crystal investment castings was developed based on basic heat transfer equations. Complex heat radiation among the multiple blade castings and the furnace wall was considered in the model. Temperature distribution and temperature gradient in superalloy investment castings of single blade and multiple ones were investigated, respectively. The calculated cooling curves were compared with the experimental results and agreed well with the latter. It is indicated that the unsymmetrical temperature distribution and curved liquid-solid interface caused by the circle distribution of multiple turbine blades are probably main reasons why the stray grain and other casting defects occur in the turbine blade.     

Failure analysis of X-Msn oil cooler fan blade on helicopter

An analysis on cracks found on AZ91C-T6 X-MSN oil cooler fan blades of a HH-47 helicopter was performed. Cracks on oil cooler fan blades, which are conditional parts, are variously distributed between 199 and 1023 operating hours. All cracks initiated from the blade root mid span as a form of multi-origin, and then developed by HAF (high amplitude fatigue). Cracks were initiated from gas porosity formed in the casting process, a shrinkage cavity and a pit instigated between base metal and coating layer. The blade with 1238 operating hours had a crack 42 mm out of the total length of 45 mm. This crack began from the convex side and penetrated through the concave side causing blade fracture. Therefore, improvement of blade manufacturing process is required and blades in operation are recommended to be eddying current inspected after paint coating removal every 250 h and to be replaced every 1000 operation hours to prevent fracture.     

镍基单晶高温合金杂晶缺陷的研究进展

随着单晶涡轮叶片结构的不断优化和高温合金中难熔元素添加量的增大,镍基高温合金单晶叶片在凝固过程中更易出现杂晶、条纹晶、枝晶碎臂、小角度晶界等缺陷。其中,杂晶是单晶叶片制备过程中最常见的一类凝固缺陷,严重影响单晶叶片的成品率。为了减少该类凝固缺陷的产生,提高叶片的成品率,研究镍基单晶高温合金杂晶缺陷的形成机制、影响因素及其控制措施,对提高单晶叶片的服役性能具有重要意义。因此,关于定向凝固过程中杂晶缺陷的形成机制、影响因素及其控制措施的研究,引起了国内外研究者的广泛关注。本文综述了单晶叶片的制备技术,分析了籽晶法和选晶法制备单晶叶片过程中不同位置杂晶的形成机理,分别讨论了选晶段杂晶、籽晶回熔区杂晶、缘板杂晶的影响因素和控制措施,并对未来的研究方向进行了展望。     

Analysis of surface quality of multi-film cooling holes in nickel-based single crystal superalloy

The effect of the surface quality of multi-film cooling holes processed by laser drilling (LD) and electrical discharge machining (EDM) on the mechanical properties of blades have been studied. The physical features of the cooling holes, including the diameter, conicity and shape of the holes, are measured by optical microscopy, demonstrating that the EDM process is not as accurate as the LD process. Meanwhile, metallurgical characteristics, including the recast layer, heat affected zone and micro-cracking within the surface layer, are analysed by scanning electron microscopy, demonstrating that the radial crack generated in the LD process is more dangerous than the circumferential cracks generated in the EDM process. Using finite element analysis (FEA), the single crystal superalloy specimens with multi-film holes are simulated based on the crystal plasticity theory, showing that a significant increase of the stress gradient is observed in a real hole model than in an ideal circular hole model, which means that a shape simplification in the blade design will reduce the reliability of the blade. Based on the findings above, the influence of the surface quality of holes is investigated to obtain the possible damages to nickel single crystal turbine blades.     

表面冶金高速钢及其应用

本文介绍了一种新型的表面冶金高速钢的形成方法，其主要过程是采用先进的双层辉光离子涌金属技术，首先对金属材料表面进行合金化处理，使其表面形成一个含高速钢主要成份的合金层，然后通过渗碳使其表面达到高速钢成份。     

叶片厚度变化对船用轴流涡轮性能的影响

目的 研究船用轴流涡轮叶片厚度对涡轮性能的影响，为高性能涡轮设计提供参考。方法 基于计算流体力学(CFD)仿真，模拟分析了2种叶片厚度下的叶片压力、涡轮流通特性及效率特性。结果 在相同膨胀比条件下，当叶片厚度从16.12 mm增大至16.61 mm(叶根处宽度)时，折合流量下降。当膨胀比从1.5增大到2时，加厚叶片的折合流量从0.216增长至0.238，未加厚叶片的折合流量从0.219增长至0.243。当膨胀比从2继续增大时，涡轮流量随膨胀比的变化而趋于平缓。当膨胀比约为2时，涡轮效率达到最高。采用加厚叶片时，涡轮效率最高达到0.815;当膨胀比为1.5~2.68时，涡轮效率在0.8以上。当采用未加厚叶片时，涡轮效率最高达到0.808;当膨胀比为1.6~2.38时，涡轮效率才能达到0.8以上。结论 转子叶片的加厚有利于降低能量损失，且叶片表面产生旋转涡流有助于减轻尾缘处的速度冲击，进一步降低了能量损失;但转子叶片过厚会限制流体的通量，使转子的通流面积减小，涡轮的折合流量减小;在大膨胀比条件下，加厚叶片涡轮的堵塞流量明显小于未加厚涡轮的。涡轮效率随膨胀比的增大而先增大后减小。随着叶片厚度的增大，涡轮整体效率增大，高效区范围增大。     

基于AHP和Pugh Matrix法的叶片表面强化工艺研究

为了评价多种表面强化工艺对汽轮机叶片的适用性,采用层次分析(AHP)法,以表面质量、表面性能和经济适用性为准则层,以14种重要评价指标为指标层,建立汽轮机叶片表面强化工艺评价体系,依次对准则层和指标层各参数进行赋权.以热喷涂工艺为基准,运用普氏矩阵(Pugh Matrix)方法,对多种表面强化工艺和传统叶片防水蚀技术进...