MoS_2涂层扭动微动磨损特性有限元分析

为探讨MoS2固体润滑涂层在抗扭动微动磨损中应用的可行性,对MoS2涂层在扭动微动下摩擦力学性能进行有限元分析,研究扭转角位移幅值、法向载荷、摩擦因数等对MoS2涂层接触表面力学行为的影响,并与基体材料扭动微动力学行为进行比较。分析结果显示:MoS2涂层扭动微动运行区域的改变消除了混合区裂纹萌生与扩展所产生的损伤;MoS2涂层在部分滑移区和滑移区,其表面塑性应变虽比基体大,但明显较小的摩擦剪应力,在部分滑移区不足以启动MoS2涂层晶体的滑移,在滑移区对塑性流动层的剪切作用不够,因此MoS2涂层表面磨损较轻微,即MoS2能有效发挥抗扭动微动磨损作用。     

有机玻璃扭动微动磨损的实时观测与摩擦振动分析

在新研制的扭动微动磨损实时观测系统上,以法向载荷为100 N和扭动角位移幅值为0.5°～15.0°的参数,对有机玻璃(Polymethylmethacrylate,PMMA)/GCr15摩擦副进行扭动微动磨损试验,同时录制扭动微动过程并同步采集摩擦振动信号。在摩擦动力学行为分析的基础上,结合实时观测和摩擦振动分析,对PMMA的扭动微动磨损行为进行研究。结果表明,随着角位移幅值增加,PMMA扭动微动呈现三个区域(即部分滑移区、混合区和滑移区);在部分滑移状态(θ=0.5°)下,损伤轻微,振动数据与空载时振动数据相似,相对运动主要靠弹性变形协调;在完全滑移状态(θ=15°)下,整个接触区发生严重损伤,大量磨屑被排出接触区,接触区最外侧呈现纺锤状银纹,每循环次数下振动信号的事件发生数先增大后减小,而振动振幅呈现相反的趋势,主要损伤机制为弹塑性变形、剥层和氧化磨损。     

TiAlZr合金微动磨损性能研究

采用高精度液压式微动磨损试验机研究了TiA lZr合金在不同微动运行区域的微动磨损行为,建立了其运行工况微动图。试验结果表明:滑移区、混合区和部分滑移区的摩擦因数随循环次数变化呈现不同的规律,其中部分滑移区摩擦因数较低,磨损体积随着位移幅值的增大而增大;滑移区、混合区磨损体积随着法向载荷的增加而增大,而部分滑移区磨损体积随着法向载荷的增加而减小;滑移区磨屑堆积于中心区域,磨损以磨粒磨损和剥层机制为主;混合区磨损机制主要表现为粘着磨损与磨粒磨损并存;部分滑移区磨损轻微。     

AZ91D镁合金微动磨损特性研究

采用液压高精度材料试验机考察了平面一球面接触的AZ91D镁合金摩擦副的微动磨损行为，分析了位移幅值、法向载荷和频率等参数对摩擦因数和磨损体积的影响，考察了不同实验条件下的磨斑形貌，并探讨了其磨损机理。结果表明：AZ91D镁合金的微动区域可分为部分滑移区、混合区和滑移区3个区域，粘着磨损、疲劳磨损和磨粒磨损分别是3个区域的主要磨损机制；磨损体积随着位移幅值和法向载荷的增加而增大，但却随着频率的增大而减小。在微动部分滑移区和混合区，摩擦因数随着位移增大迅速增加；在微动滑移区，摩擦因数随法向载荷的增大而减小，而位移幅值和频率对摩擦因数的影响较小。     

LZ50车轴钢转动微动摩擦学特性研究

在新型转动微动磨损试验机上,进行LZ50车轴钢/GCr15钢在法向载荷为10N、转动角位移幅值为0.125°～0.5°的转动微动磨损试验。在摩擦动力学行为分析的基础上,结合磨痕的微观分析,研究材料的转动微动磨损机理。结果表明,LZ50车轴钢的微动运行区域仅呈现部分滑移区和滑移区,未观察到混合区。滑移区的摩擦因数明显高于部分滑移区;摩擦因数随着转动角位移幅值的增加而增大。车轴钢在部分滑移区损伤轻微,磨痕呈环状;而在滑移区,接触中心呈现材料塑性流动累积造成"隆起"特征,LZ50钢的转动微动磨损机制主要为磨粒磨损、剥层和氧化磨损。     

往复轴封氟橡胶O型圈微动摩擦学特性

在UMT多功能摩擦磨损试验机上,以氟橡胶(Fluorine rubber,FKM)O型圈/不锈钢平面配副为研究对象,研究了不同接触载荷和位移幅值下FKM O型圈的微动摩擦学特性。在动力学特性分析的基础上对磨痕表面形貌进行扫描电镜及表面成分分析,研究FKM O型圈在微动作用下的运行行为、磨损机理及其损伤演变规律。结果表明:随着位移幅值的增加,FKM依次运行于部分滑移区(Partial slip regime,PSR)、混合区(Mixed fretting regime,MFR)和滑移区(Slip regime,SR);接触载荷明显地改变了微动的运行区域,载荷越大MFR的范围增大,且微动越不易进入MFR和SR;与扭动微动相似,FKM弹性体混合区的判定需要结合F_t-D曲线和磨痕形貌的演变过程;在不同的微动运行区域,FKM的损伤特征及摩擦因数(F_t/F_n)演变明显不同。在PSR,FKM表面损伤较轻微;在MFR及其附近,FKM的材料损伤表现为裂纹的萌生与扩展、表面剥落和点蚀以及局部的磨损;在SR,FKM磨损表面表现出橡胶材料特有的花纹磨损特征;此外,在MFR和SR的磨损表面,FKM发生了明显的摩擦氧化。     

离子渗氮／ 渗硫层转动微动摩擦学行为研究

利用渗氮/渗硫复合处理在LZ50钢表面制备离子渗氮/渗硫层,在干态及不同角位移幅值下对渗层及其基体材料进行转动微动磨损试验,利用扫描电子显微镜、能谱仪和2D/3D轮廓仪对磨痕进行微观分析。试验结果表明：渗氮/渗硫层改变了基体材料的微动运行工况图,部分滑移区和滑移区边界向部分滑移区移动,滑移区运行范围增大;在部分滑移区,渗层的摩擦因数明显低于基体材料,其损伤十分轻微;在滑移区,次表层剥落的硬质颗粒使得稳定阶段摩擦因数高于基体材料,磨损机制为磨粒磨损、氧化磨损和剥层。     

粘结MoS2固体润滑涂层的转动微动磨损特性

采用粘结法在LZ50钢表面制备MoS2固体润滑涂层,研究MoS2涂层及LZ50钢基体在干态不同角位移幅值下的转动微动磨损行为。在分析转动微动动力学特性的同时,结合光学显微镜、扫描电子显微镜、电子能谱仪以及轮廓仪对磨痕形貌进行微观分析。结果表明:涂层和基体的转动微动运行区域仅呈现部分滑移区(Partial slip regime,PSR)和滑移区(Slip regime,SR),未观察到混合区。涂层改变基体的微动运行区域,使得PSR缩小,SR运行区域向小角位移幅值方向移动。由于MoS2涂层的固体润滑作用,涂层的摩擦因数在整个试验过程都明显低于基体。在PSR,涂层损伤轻微;在SR,涂层的转动微动磨损机制主要表现为剥层和摩擦氧化。研究表明粘结MoS2固体润滑涂层具有明显的防护作用,显著降低LZ50钢的转动微动磨损。     

钛合金球与骨水泥界面之间的微动磨损机制研究

采用钛合金球与自制骨水泥试样以球/平面接触方式,在自制的微动摩擦磨损试验机上开展干摩擦和25%小牛血清介质中切向微动磨损试验研究,考察钛合金球与骨水泥界面之间的微动运行特性,并采用S-3000N型扫描电镜观察磨痕形貌来分析其微动磨损机制。结果表明:随着微动振幅的增加,微动运行由部分滑移区向混合区转变。随着接触载荷的增加,试样接触面之间更容易发生黏着。与干摩擦相比,在小牛血清溶液中部分滑移区向较大振幅区扩展。部分滑移区摩擦因数值较低且保持稳定,混合区的摩擦因数先增大后保持不变。稳定摩擦因数随着接触载荷的增加而减小,随微动振幅增大而增大。骨水泥试样的磨损量在小牛血清介质中比在空气中大,并且随接触载荷增大而增大。骨水泥在小牛血清介质中微动磨损的损伤机制主要为黏着磨损和疲劳磨损,溶液分子在应力作用下对骨水泥基体有削弱作用。     

离子渗硫层在油润滑条件下的转动微动摩擦磨损性能

利用低温离子渗硫技术在LZ50钢表面制备渗硫层,在干摩擦和油润滑条件下开展不同角位移幅值的渗硫层转动微动磨损试验,并利用扫描电子显微镜、能谱仪和轮廓仪对磨斑进行微观分析。试验结果表明:与干摩擦相比,油润滑条件下离子渗硫层呈现出不同的微动运行工况图,部分滑移区和滑移区的界限向左移动,滑移区的运行范围增大;在部分滑移区,渗硫层在油润滑条件下的摩擦因数几乎不变,且明显低于干摩擦,损伤十分轻微;在滑移区,渗硫层在油润滑条件下的摩擦因数仍低于干摩擦,呈现"初始-爬升-稳定"3个阶段,其磨损机制为磨粒磨损和剥层。     

690合金材料的微动磨损特性研究

利用微动磨损试验机,在载荷50N以及位移幅值为60μm、100μm、150μm的工况下,研究了690合金材料在常温下的微动磨损行为及其动力学特性,采用激光共焦扫描显微镜(LCSM)和扫描电子显微镜(SEM)观察磨痕微观形貌。结果表明,载荷和位移幅值对微动特征有很大的影响,微动运行完全处于滑移状态。在滑移区,滑移磨损严重、磨痕面积大。690合金材料的磨损机制主要表现为磨粒磨损与剥层的共同作用。     

An experimental study torsional fretting behaviors of LZ50 steel

Four simple fretting modes are defined according to relative motion: tangential, radial, rotational, and torsional fretting. This paper presents a new test rig that was developed from a low-speed reciprocating rotary system to show torsional fretting wear under ball-on-flat contact. Torsional fretting behavior was investigated for LZ50 steel flats against AISI52100 steel balls under various angular displacement amplitudes and normal loads. The friction torques and dissipation energy were analyzed in detail. Two types of T–θ curves in the shape of quasi-parallelograms and ellipticals were found that correspond to gross and partial slips, respectively. The experimental results showed that the dynamic behavior and damage processes depend strongly on the normal loads, angular displacement amplitudes, and cycles. In this paper, the debris and oxidation behaviors and detachment of particles in partial and gross slip regimes are also discussed. Debris and oxidation are shown to have important roles during the torsional fretting processes. The wear mechanism of torsional fretting was a combination of abrasive and oxidative wear and delamination before third-body bed formation. The mechanism was then transformed into third-body wear after a great amount of debris formed.     

基于双重扩展自适应卡尔曼滤波的汽车状态和参数估计

准确实时地获取行驶过程中的状态信息是汽车动态控制系统研究的关键,为此提出了一种新的汽车状态估计器。建立了包含不准确模型参数和未知时变统计特性噪声的非线性汽车动力学模型,针对该非线性系统提出一种双重扩展自适应卡尔曼滤波算法（DEAKF）。该算法采用两个卡尔曼滤波器并行运算,状态估计和参数估计互相更新,同时将带遗忘因子的噪声统计估值器嵌入到状态校正过程和参数校正过程之间,以解决系统的噪声时变问题。基于ADAMS的虚拟试验和实车试验结果表明,该算法的状态估计精度高于EKF方法和DEKF方法的状态估计精度,同时具有良好的模型参数校正能力,对汽车动态控制系统中估计器的设计具有理论指导意义。
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Torsional Fretting Wear Behavior of Bonded MoS2 Solid Lubricant Coatings

The effects of applying a bonded MoS₂ solid lubricant to a 1050 steel substrate were investigated using a torsional fretting wear apparatus. Tests were conducted under a normal load of 50 N with angular displacement amplitudes ranging from 0.1 to 5°. Wear scars were examined using scanning electron microscopy, energy-dispersive X-ray spectrometry, optical microscopy, and surface profilometry. The MoS₂ coating exhibited different torsional fretting regimes than those of the substrate. Fretting regimes of the coating were primarily in the partial slip regime (PSR) and the slip regime (SR) with no mixed fretting regime. The width of the PSR narrowed. Due to the lubricating effects of the coating, the friction torque was consistently lower than that of the substrate. The damage to the coating in the PSR was very slight, and its granular structure remained even after 1,000 cycles. The damage mechanism to the SR coating was a combination of abrasive wear, oxidative wear, and delamination. The MoS₂ coating had potential to alleviate torsional fretting wear.     

Dual-rotary fretting wear behavior of 7075 aluminum alloy

Friction and wear behavior of dual-rotary fretting (DRF) combined by torsional and rotational fretting modes have been investigated. Such fretting mode is essentially achieved by changing tilt angles of the rotary axis and varying rotary angular displacement amplitudes The DRF behavior has been characterized from the dynamic behavior, wear damage, third-body behavior, wear mechanisms. The running condition fretting map (RCFM) of DRF fretting wear was established by using the tilt angles and angular displacement amplitudes. The evolution of the wear volume vs the tilt angle under varied angular displacement amplitudes was quantificationally measured. In addition, the competition between the local wear and fatigue (cracking, wear) has been discussed in detail. The results indicated that the damage of 7075 aluminum alloy induced by DRF was strongly dependent upon the tilt angle and the angular displacement amplitude.     

Study on rotational fretting wear of 7075 aluminum alloy

Rotational fretting wear tests in a ball-on-flat configuration have been successfully realized on a special rotational fretting rig developed from an ultra-low-speed reciprocating rotational driver. The rotational fretting behavior of 7075 aluminum alloy against 52 100 steel was studied under different angular displacement amplitudes and normal loads. The results showed that both F_t?θ and F_t/F_n curves can be used to characterize the rotational fretting running behavior, which exhibited different curve shapes and variation trends in different fretting running regimes. The rotational fretting behavior of 7075 aluminum alloy was strongly dependent on the angular displacement amplitude, normal load and number of cycles. The wear of 7075 aluminum alloy was characterized by slight attrition in the partial slip regime, while a combination of delamination, abrasive and oxidative wear was found in the slip and mixed fretting regimes. The formation of a central bulge probably due to plastic flow was observed under gross slip condition of the rotational fretting mode.     

Study on rotational fretting wear of bonded MoS2 solid lubricant coating prepared on medium carbon steel

The rotational fretting wear behaviors of the bonded MoS₂ solid lubricant coating and its substrate steel were comparatively studied under varied angular displacement amplitudes, constant normal load, and rotational speed. Dynamic analysis in combination with microscopic examinations was performed through SEM, EDX, XPS, optical microscope, and surface profilometer. The experimental results showed MoS₂ changed the fretting running regimes of substrate. The friction coefficients of MoS₂ were lower than those of the substrate. For MoS₂, the damage in partial slip regime was very slight. The damage mechanism of the coating in slip regime was main abrasive wear, delamination, and tribo-oxidation.     

Fretting wear behaviors of a railway axle steel

Fretting damage was one of the most important reasons for the failure of the railway axle. Fretting wear (tangential fretting mode) tests of a railway axle steel (LZ50 steel) flats against 52 100 steel balls were carried out under different normal loads and displacement amplitudes on a hydraulic fretting wear rig. Dynamic analyses in combination with microscopic examinations have been performed. The experimental results showed that the fretting regimes of the LZ50 steel were strongly dependent upon the imposed normal loads and displacement amplitudes. The F_t/F_n curves exhibited different variation trends in different fretting running regimes. The fretting scars presented slight damage in partial slip regime. In mixed fretting regime, the trace of the plowing and plastic deformation flow can be observed on the fretting scars. The wear mechanism during this regime was the combination of the abrasive wear, oxidative wear and delamination accompanied with obvious plastic deformation. The detachment of particles and plowing traces were the main phenomena in slip regime. And, thicker debris layer covered the contact zone of the scar. The severe degradation in slip regime presented the main wear mechanisms of abrasive wear, oxidative wear and delamination.