三相磨料射流作用下材料的破坏机理研究

针对一种新型磨料射流形式，从摩擦学角度出发，分析材料在其作用下的破坏机理。结果表明材料磨蚀主要由冲蚀磨损、气蚀破坏以及它们的共混蚀损作用造成的。特别是共混蚀损，它是三相流中一种独特的现象，相互制约，相互促进，加速了材料的破坏。     

水轮机过流部件喷焊耐磨蚀涂层（六）

目前,我国制造水轮机用材料多为铸钢,少数为铬不锈钢,这些材料的耐气蚀与磨蚀性能均较差,通常运行不到10000h(一年左右)就要大修。一台中型机组的一次维修费用高达30多万元,因此如何更有效地防止水轮机过流部件的气蚀或磨蚀破坏,提高其使用寿命,确保水电站的安全经济运行和充分利用水力资源,一直是我国水力发电中的重大课题之一。     

水轮机过流件的磨蚀与表面防护

文章简述了材料水力磨蚀方面的有关研究成果,应用试验证明非金属弹性护面涂层有较好的抗气蚀与泥沙磨损性能,值得推广。     

冲蚀与气蚀复合磨损试验装置及其试验研究

在分析典型含沙水流的冲蚀、气蚀磨损试验设备和方法的基础上,针对我国水力机械和水工建筑的特殊损伤破坏形式提出了基于射流的水下冲蚀与气蚀复合磨损试验设备和方法。实验室泥沙冲蚀与气蚀复合磨损模拟试验结果表明,该试验装置设计合理,可以在较短时间内获得试验数据。对2种典型的耐磨不锈钢材料进行了冲蚀磨损试验研究,发现2种材料在冲蚀磨损过程中伴随有气蚀作用机制,材料损伤的实质是冲蚀与气蚀的复合磨损。     

水力机械的各种腐蚀及其特点

水力机械的磨蚀类型,按机理不同可分为三类,即空蚀(Cavitation damage)、磨损(erosion)和腐蚀(corroksion)。 空蚀,是指由于空化作用所引起的材料破坏。最典型的空蚀是发生在水轮机转轮叶片负压区的破坏现象。 磨蚀,是指含沙水流对水力机械部件的作用,而使其表面逐渐失去材料的物理现象。     

论材料的实验室磨损试验与实物试验的差异

按一般概念，实验室磨损试验与实物试验所获得的磨损表面形貌如果相似，就认为实验室试验是有效的。但有时磨损表面的形貌相互之间极有为相似，然而材料的磨损机理及材料耐磨性次序可能有很大差异。文中对气蚀及磨料磨蚀两事例进讨论。     

关于气蚀破坏几个问题的探讨

本文分析了气蚀破坏的原因,认为气蚀对材料的破坏主要是机械作用,其次为腐蚀因素等。机械作用主要是气泡溃灭时对材料表面带来的多次冲击应力,该应力可能高于材料的屈服强度,也可能低于屈服强度,但均可使材料产生破坏。作者认为具有一定耐腐蚀性的低碳马氏体钢是能抗气蚀的,并提出在液体介质中用多次冲击试验对耐气蚀材料进行评定。     

基于流体机械工况的冲蚀磨损特性研究

在圆盘式磨蚀试验台上，对流体机械常用材料HT200、45与40Cr钢进行了模拟实际工况的冲蚀磨蚀试验，研究了试验材料的表面失效规律及微观破坏机理。结果表明：冲蚀分为跑合期、稳定期和上升期三个阶段。灰铁HT200的冲蚀磨损以脆性断裂为主；45钢的冲蚀磨损是以切削磨损为主；40Cr是以犁沟剥落为主。     

浅谈多泥沙电站水轮机抗磨蚀的措施

水轮机的磨蚀,已成为水力发电部门急待解决的重要技术难题,本文分析了磨蚀破坏影响水轮机过流部件的作用机理,并对如何提高抗磨蚀提出几种主要措施。     

含沙量和沙粒粒径对QT500材料冲蚀磨损特性的影响

利用圆盘式磨蚀试验装置模拟流体机械工况条件，对QT500和45钢进行了冲蚀磨损试验，用失重法研究了材料在不同含沙量和沙粒粒径时的冲蚀磨损特性。对试样表面微观形貌进行了观察，探讨了材料的冲蚀磨损机理和损伤规律。研究表明：随含沙量的增加，材料的磨损率也增加，但不与含沙量的增加值成正比；随沙粒粒径的增大，磨损量亦增加。QT500的冲蚀磨损机理主要是脆性剥落和疲劳破坏。     

Influence of heat and thermochemical treatment on abrasion resistance of structural and tool steels

Abrasive wear is responsible for intensive degradation of machine parts or tools. This process starts as an interaction between hard, mostly mineral, particles and the working surface. Methods of increasing the lifetime are based on application of abrasion resistant materials or creation of hard, wear-resistant surface layers or coatings on the surfaces of machine parts or tools. Carbon and low-alloy steels with different types of thermochemical treatment (case hardening, nitriding) are used in cases of low abrasion. Another method of increasing lifetime is the application of ledeburitic steels. The wear resistance of these steels depends on their chemical composition and heat treatment. The results of laboratory tests of thermochemically treated steels, heat-treated ledeburitic chromium steels and high-speed steels show the effect of the microstructure of these steels on their abrasion resistance. Abrasion resistance of carburized low-alloy steels is on the same level as in high-carbon structural and tool steels. In ledeburitic chromium steel maximum abrasion resistance was achieved by quenching from 1100 °C whilst in ledeburitic chromium–vanadium steel the optimum quenching temperature was 1150 °C. Growing abrasion resistance was caused by increasing amounts of retained austenite.     

Improvement of Local Surface Quality by Using Single Abrasive Abrasion Process

AFM-based wear process actually is single abrasive abrasion process. It is widely employed in the surface micro/nano machining for fabrication of structures at the nanometer scale exhibiting high removing ability of nanometer scale materials. In this study, application of AFM-based single abrasive abrasion process in the local surface quality (surface roughness) improvement was studied. Merged holes were fabricated using an AFM diamond tip with different wear parameters on the surface of germanium (Ge) machined by conventional ultra-precision diamond turning. Results showed that cracks left by diamond turning can be removed and the local surface quality can be improved. Also effects of the wear parameters on the surface roughness were investigated. The optimized parameters of the abrasion process for improving the surface quality were provided. It is verified that AFM-based single abrasive abrasion process is a novel approach to modify or repair local surface on the surface of parts manufactured by other methods.     

粗糙表面弹性变形对流量因子的影响

利用FFT技术计算粗糙表面的弹性变形,并提出弹性变形对流量因子影响模型,给出了几个该模型的计算实例,探讨了流量因子大小与计算区域边界压力大小的关系。结果表明,由于弹性变形的存在,使膜厚变大,因而对于横向表面和各向同性表面,压力流量因子比不考虑弹性变形时增大,剪切流量因子减小;对于纵向表面,压力流量因子减小,剪切流量因子增大。通过算例分析发现,粗糙表面弹性变形对流量因子的影响包括两部分,即对平均膜厚的影响和对粗糙度的影响,而后者是主要的影响。     

Scratch and wear performance of prosthetic femoral head components against crosslinked UHMWPE sockets

Total hip arthroplasty is a highly successful procedure where the hip joint is replaced by an artificial ball and socket joint. Bearing wear continues to be a contributing factor to implant failure. Prosthetic femoral heads roughen in vivo which leads to increased wear. Along with the introduction of improved polyethylene which reduces wear by up to 99%, improved femoral head materials have been introduced to improve resistance to abrasion. The abrasion resistance of two of these improved femoral heads was assessed in this study and compared to a cobalt chromium (CoCr) femoral head. The resulting wear performance against a polyethylene acetabular component was assessed. The bulk ceramic (zirconia toughened alumina) femoral head exhibited superior abrasion resistance compared to CoCr (97% reduction in damage) as well as reduced wear after abrasion (97% reduction in wear). The oxide coated zirconium niobium femoral head showed inferior abrasion resistance compared to CoCr (99% increase in damage) as well as increased wear after abrasion (161% increase in wear). Both femoral head surfaces utilize hard ceramic materials, however, the thin ceramic coating on top of a softer metallic substrate of the oxide coated bearing was unable to withstand aggressive abrasion.     

车磨抛合一的数控加工

在数控车床上,应用SN弹性砂轮,可将车磨抛工序集于一身,扩展了数控车床的加工范围,尤其适合重要零件的加工和修复.在数控改造中,采用特殊的结构,将一般数控机床单一的单位控制精度改为多单位控制精度,并针对实际加工中需要的不同抛磨次数,采取特殊的程序结构予以处理,而且还实现了对SN弹性砂轮弹压量和磨损的瞬时自动补偿。     

水工混凝土材料与磨损

结合混凝土材料的缺陷分析,探讨了含沙高速水流冲击作用下,混凝土材料的冲蚀磨损特性与机制。结果表明,混凝土材料呈现典型的脆性材料磨损特征,冲击角度较低时,硬质磨粒的切削作用对磨损起主导地位,磨损程度相对较轻;随着冲角的增大,磨损表面主要承受硬质磨粒垂直方向作用力的影响,裂纹产生、扩展和交叉进而产生脆性断裂与剥落的过程对磨损起主导地位,磨损程度相对较为严重。混凝土材料表层及亚表层的多种缺陷,成为组织结构中的薄弱环节,裂纹易于从缺陷处生成并扩展,促进了混凝土的冲蚀磨损。     

复合抽油杆旋转装置的研制

为了防治抽油杆偏磨和断脱,研制了复合抽油杆旋转装置。该装置将弹簧的弹性形变引起的垂直运动转变为旋转运动,实现了抽油杆的自动间歇旋转,达到抽油杆均匀磨损的目的。利用弹簧吸收释放能量,又避免了冲击载荷的产生,减少了抽油杆断脱现象的发生,延长了抽油杆和传动零件的使用寿命。现场应用表明,该装置可以延长油井的免修期,有较好的应用前景。     

有无冷却水冲洗对热水泵口环变形的影响分析

口环间隙对离心泵的性能有着重要的影响,不仅产生了容积损失,还改变了离心泵的内部流动结构,从而对轴向力和径向力产生重要的影响,所以口环间隙的选择很重要。在高温热水泵使用过程中,介质的高温对泵的结构有着重要的影响,材料的特性会随着材料温度的变化而发生相应的变化,经常出现泵口环的热变形磨损,甚至造成转子部件的咬死,导致开车失败,严重影响着高温热水泵运行的可靠性。通过对TEG200-400型的热水循环泵进行热固耦合分析,研究在输送200℃热水时,有无冷却水冲洗对热水循环泵口环变形的影响情况,为口环间隙的选择提供了一定的基础。     

装载机销轴磨损历程分析及其改进

销轴是装载机工作装置的重要连接部件,销轴的磨损失效往往造成严重的后果。通过大量试验,分析了装载机销轴磨损的历程,表明销轴的磨损历程主要分为磨合阶段、磨粒磨损阶段和粘结磨损阶段。结合虚拟样机技术和有限元技术,确定了销轴的最大磨损位置,对销轴油孔的结构进行了改进,提高了润滑效果,延长了销轴的使用寿命。