自升式平台升降系统齿轮失效分析

通过对某自升式平台齿轮齿条升降系统的失效齿轮及全新齿条分别进行化学成分分析、金相检验和硬度测试,分析了造成该系统中齿轮失效的原因。结果表明:齿轮的失效形式为接触疲劳失效;齿轮材料表面热处理不均匀,节圆附近无硬化层,导致其失效面的表面硬度低于与其相啮合齿条的表面硬度,这是造成该齿轮长期服役后在节圆附近发生接触疲劳失效的主要原因。     

高强度合金抗疲劳应用技术研究与发展

评述了超高强度钢、高强度Al合金和Ti合金表面完整性抗疲劳应用技术的研究和发展。高强度合金疲劳性能对应力集中敏感，不适当的加工工艺和切削热等造成的表面损伤和高拉应力使其疲劳和应力腐蚀性能损失殆尽。先进的表面完整性加工尤其是表面改性可显著提高疲劳性能，如激光冲击使7475-T761拉-拉疲劳寿命提高约89％，7075-T6裂纹扩展速率降低到原来的1／1500；超声喷丸使超高强度钢低周疲劳强度提高约50％，Ti7Al4Mo合金高周疲劳强度提高约15％；表面超硬化可使Vasco X-2M齿轮钢接触疲劳寿命提高30～35倍等。     

微合金化渗碳齿轮钢的接触疲劳性能

通过滚动接触疲劳试验方法,研究了两种渗碳齿轮钢的接触疲劳性能.结果发现,渗碳齿轮钢接触疲劳试样失效方式主要为渗碳层的点蚀和剥落.氧含量较低的Nb微合金化齿轮钢(含0.04%的Nb)中氧化物夹杂数量少、尺寸小,接触疲劳裂纹起裂较难;同时,Nb微合金化齿轮钢渗碳层晶粒尺寸小、硬度高,提高了疲劳裂纹萌生及扩展阻力,导致Nb微合金化后,齿轮钢的接触疲劳寿命大幅度提高.     

阳极极化曲线在CuSn合金接触线电解抛光中的应用

本文以电解抛光原理为依据,以阳极极化曲线为参考,对高速电气化铁路用CuSn合金接触线的电解抛光工艺参数进行了研究。同时,通过对以往电解抛光装置的改进最终确定了CuSn合金接触线电解抛光的最佳工艺参数。研究结果表明,在室温条件下,采用1．5～1．9V的抛光电压,10—15min的抛光时间,可以有效地消除CuSn合金接触线试样表面的划痕,不产生表面变形层,显示的组织形貌更清晰。     

40CrNiM0齿轮材料点蚀破坏的金相研究

用金相试验方法,对40CrNiMo中等硬度齿轮材料在接触疲劳过程中的表面破坏形态、裂纹的萌生与扩展等问题进行了研究,并从金属学角度对材料失效破坏过程进行了分析.结果表明,经过一定周次的循环后,试验滚轮表面产生的接触疲劳破坏是属点蚀破坏,从滚轮表面产生的塑性变形和金属流变层是表面产生点蚀破坏的重要原因.     

40CrNiMo齿轮材料点蚀破坏的金相研究

用金相试验方法,对40CrNiMo中等硬度齿轮材料在接触疲劳过程中的表面破坏形态,裂纹的萌生与扩展等问题进行了研究,并从金属学角度对材料失效破坏过程进行了分析,结果表明,经过一定周次的循环后,试验滚轮表面产生的接触疲劳破坏是属点蚀破坏,从滚轮表面产生的塑性变形和金属流变层是表面产生点蚀破坏的重要原因。     

变速箱双联齿和512齿轮失效分析

某型号变速箱在台架试验过程中,双联齿和与之啮合的512齿轮均发生失效事件。采用断口分析、金相检验、硬度测试以及化学成分分析等方法对失效件进行了检验。结果表明:由于双联齿和512齿轮的齿面存在严重的异常接触,加之双联齿的有效硬化层深度和心部硬度均低于技术要求,从而导致在台架试验过程中双联齿表面发生严重的接触疲劳剥落,与之啮合的512齿轮发生弯曲疲劳断齿。     

化学镀Ni—Re—P合金镀层的研究

本文采用化学镀工艺在铁基合金表面镀上Ni—Re-P合金，并采用SEM和XRD等方法研究了化学镀Ni—Re—P三元合金镀层的形貌和成分变化。经600℃热处理，Ni—Re—P三元舍金镀层将会发生分层现象，同时由于合金选择性氧化而导致富Re层的出现，富Re层将增加合金的耐磨性和抗氧化能力。热疲劳实验结果表明Ni—Re—P三元合金镀层与基体有较强的结合能力。     

支承刚度及齿面涂层对斜齿轮副啮合特性的影响研究

支承刚度对自动变速器齿轮副的啮合质量有着重要影响,研究支承刚度及齿面涂层对斜齿轮副啮合特性的影响具有重要意义。以某七挡双离合自动变速器的一挡斜齿轮副为研究对象,建立了2种不同支承刚度的齿轴系统刚柔耦合模型,分析了不同工况下支承刚度对斜齿轮副啮合特性的影响规律;通过FCL-250H齿轮精测试验台得到有/无磷酸锰转化涂层齿轮的齿形齿向参数,并将其代入有限元模型进行仿真分析;进行齿轮接触疲劳点蚀实验,对比齿面涂层处理前后齿轮的接触疲劳寿命,并从齿轮表面形貌、动力性能及跑合性能等角度进一步揭示了涂层的强化机理。研究结果表明：齿轴跨度增大,支承刚度减小,则齿轮单位长度所受最大载荷和啮合错位量对输入扭矩的变化更为敏感;有涂层齿轮跑合后更有利于啮合,其疲劳寿命得到提高。研究结果为汽车自动变速器齿轮传动系统的结构优化和齿轮疲劳寿命的提高提供了参考。     

滚动接触条件下铁基涂层的疲劳磨损寿命实验研究

利用超音速等离子喷涂技术在45钢表面制备了铁基合金涂层,利用球盘式疲劳磨损实验机评价了铁基涂层在两种载荷条件下的疲劳磨损性能,利用两参数Weibull分布表征了涂层的疲劳寿命,采用扫描电子显微镜(SEM)分析了涂层的微观结构和失效形貌,利用有限元方法研究了涂层内部应力分布.实验结果表明,载荷条件可以显著地影响涂层的寿命和失效形貌,高载下涂层的寿命明显降低;随着载荷的增加,主要失效形式由表面磨损失效转换成剥层失效,其中表面磨损是由于粗糙接触引起,而剥层则与应力分布机制有关.     

Fatigue behaviour of dissimilar Al 5052 and Mg AZ31 resistance spot welds with Sn‐coated steel interlayer

The fatigue property of dissimilar spot welds between an aluminium alloy (AA5052) and a magnesium alloy (AZ31) was studied in this research. The AA5052 and AZ31 coupons were resistance spot welded together by using an interlayer of Sn‐coated steel between the two coupons. The fatigue test results revealed that the Mg/Al joints had the same level of fatigue strength as Mg/Mg resistance spot welds. It was found that within the life range of N_f < 10⁵ cycles, Mg/Al welds degraded faster than Mg/Mg joints. This was attributed to the larger bending moment on the plane of fatigue failure in the Mg/Al welds. Three failure modes were observed under different cyclic loading regimes: Al/steel interfacial failure, Mg coupon failure and Al coupon failure. Fatigue fracture surface of Mg/Al welds consisted of two distinct regions: crack propagation region with brittle morphology and final rupture with ductile morphology.     

Influence of contact pressure on fretting fatigue behaviour of AA 2014 alloy with dissimilar mating material

The effect of contact pressure on the fretting fatigue behaviour of 2014 Al alloy which has been solution heat treated and age hardened (T6 heat treatment) with dissimilar mating materials, was investigated. The fretting fatigue configuration involved bridge‐type contact pads on a flat fatigue specimen. Specimens were made of 2014 Al alloy and bridge‐type pads were made AISI 4140 steel. All the fatigue tests were conducted at a rotational speed of 5000 rpm with a rotating bending fatigue machine (R=?1), using S–N curves to evaluate the fatigue and fretting fatigue properties. The fretting fatigue strength of the material subject to a T6 heat treatment condition at 1 × 10⁷ cycles was dramatically reduced, as compared to that without fretting and with as‐cast. The fretting fatigue life exhibited a variable behaviour with an increase in the contact pressure. A scanning electron microscope was employed to observe the fretting scars and fracture surfaces of the specimens. This analysis showed that cracks originated at the contact surface and crack orientations were approximately ±56 ° from perpendicular to the loading direction.     

Rolling contact fatigue behavior of sintered and hardened steels

Powder-metal-processed bearings and gears are finding increasing application because of their economical and technical advantages. The residual pores from the sintering operatives act as lubricant pockets and dampen sound and vibration. However, porosity also decreases the mechanical strength and reduces the life of components fabricated by powder processing relative to similar wrought components. The rolling contact fatigue behavior of sintered and heat treated steel rollers was investigated using a fatigue test machine designed and fabricated for that purpose. The powder-metal-processed and the wrought steel rollers that were tested had similar composition and hardness and were mated against wrought steel rollers of high hardness. The contact stress versus number of cycles to failure data showed that the wrought steel had a very high endurance limit under rolling contact fatigue compared to the sintered steels investigated. Rolling contact fatigue behavior was found to depend on the porosity present in the material. Large surface peeling failures and pitting type fatigue failures were observed in the sintered and hardened steels, while only pitting type failures were observed in the wrought steels     

等离子喷涂铁基涂层的接触疲劳失效机理研究

对超音速等离子喷涂铁基涂层的接触疲劳失效机理进行了研究.使用球盘式接触疲劳试验机进行了涂层的接触疲劳实验,并通过对失效试样表面形貌的观察,总结出了涂层三种典型的失效形式,即点蚀、剥落和分层.分别研究了三种失效形式的相应的失效机理,结果表明:点蚀失效是由粗糙的表面引起的;剥落失效是由于表层与次表层的微观缺陷引起的;而分层失效则由涂层内部的剪切应力机制决定.     

The effect of high-velocity oxygen fuel, thermally sprayed WC–Co coatings on the high-cycle fatigue of aluminium alloy and steel

Thermally sprayed WC–Co coatings are currently used in numerous contact wear applications in the aircraft, automotive and paper industries. High-cycle fatigue tests were performed at room temperature and 370 °C on SAE 12L14 low-carbon steel and aluminium alloy 2024-T4 thermally sprayed with WC–17 wt% Co using the high-velocity oxygen fuel process. The fatigue life distributions of specimens in the polished, grit-blasted, peened and coated conditions are presented as a function of the probability of failure. Composite beam theory was applied to the coated beam to evaluate the stresses and elastic modulus.The stress–strain curves for the coated and uncoated specimens were used to evaluate the stiffness factor for the aluminium alloy and steel. It is concluded that (i) the coated specimens exhibited significantly high fatigue lives compared with the uncoated specimens, (ii) the mechanisms of deformation for the coated and uncoated aluminium alloy specimens are quite different and (iii) the elastic modulus of the coating plays a significant role in determining the fatigue strength of the coated component. © 1998 Kluwer Academic Publishers     

Corrosion resistance of molybdenum coatings obtained by a contact melting method

The corrosion resistance and fatigue strength of molybdenum coatings obtained by a contact melting method on 1Cr18Ni9Ti steel and on EI 437B alloy were investigated. It was shown that the use of such a coating on EI 437B alloy quadruples its fatigue strength in liquid Pb-Bi eutectic.Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 5, No. 6, pp. 704–708, November–December, 1969.     

微缺陷对热喷涂涂层接触疲劳性能的影响

采用超音速等离子喷涂设备在45号钢基体上制备了三种含有不同微缺陷的NiCrBSi合金涂层。使用球盘式接触疲劳实验机对涂层的接触疲劳性能进行了测试,建立了Weibull失效概率图;使用扫描电子显微镜对涂层的微观结构和失效形貌进行了表征;比较了三种涂层的接触疲劳寿命及涂层的主要疲劳失效模式。结果表明,涂层内的微缺陷主要由微孔隙和微裂纹构成,涂层接触疲劳寿命的长短与这些微缺陷含量的多少成反比,涂层的孔隙率为2.5%,1.3%和2.1%,对应的接触疲劳寿命分别为7.77×105,8.99×105,7.81×105周次。同时,涂层微缺陷含量较少时涂层的失效模式主要以剥落失效为主;涂层微缺陷含量较多、结合强度较差时主要以分层失效为主;涂层内存在较大的孔隙可致使涂层的提早失效,同时涂层表面磨损失效的概率增加。     

中锰铁基合金激光熔覆层组织和接触疲劳性能

为了探讨齿类零件表面接触疲劳损伤后的修复技术,在45钢表面激光熔覆了一层中锰铁基合金。分别采用扫描电镜(SEM)、光学显微镜(OM)、X射线衍射仪(XRD)、HVS-1000型显微硬度计和JPM-1型接触疲劳试验机分析了中锰铁基合金熔覆层的显微组织,测试了其显微硬度和接触疲劳性能。结果表明:中锰铁基合金熔覆层与基体间形成了冶金结合,且其熔覆层无裂纹、气孔等缺陷;中锰铁基合金熔覆层的显微硬度为500~600HV,比渗碳层具有较高的抗接触疲劳性能,能够满足齿类零件的性能要求。     

拓扑与形状优化用于有效的产品设计

 介绍了基于有限元法(FEM)的计算机辅助结构优化方法． 拓扑优化有助于设计新零件的形状，形状优化则通过表面几何形状的局部调整改善零件的刚度或使用寿命．     

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。