考虑磨损含间隙曲柄滑块机构的动态特性研究

为得到准确的含间隙铰接机构的接触碰撞模型,在ADAMS中建立含间隙的曲柄滑块机构,以含间隙曲柄滑块机构运动副为对象分析其在考虑磨损情况下的动态特性。以接触一碰撞模型为基础,采用非线性等效弹簧阻尼模型,将用MATLAB处理过的数据和磨损函数嵌入到ADAMS模型中进行动力学仿真,并将得到的动态特性曲线进行分析。结果表明：磨损对间隙运动副的速度、加速度、接触碰撞力和力矩有很大的影响,同时,此种建模方法对建立准确的含间隙机构的模型有很大的参考意义。     

含间隙曲柄滑块机构运动副动态磨损研究

含间隙曲柄滑块机构中运动副的润滑情况不同于滑动轴承,其相对速度不足以形成动压润滑而处于边界润滑状态下.为了分析此状态下的动态磨损问题,考虑到含间隙运动副边界润滑时轴套的切向弹性变形和切向阻尼,结合考虑间隙运动副碰撞接触的非线性弹簧阻尼模型,提出边界润滑条件下的间隙副接触力模型,进而在此基础上推导出间隙副的动态磨损模型,并对含间隙曲柄滑块机构的运动副动态磨损进行数值分析.计算结果表明副元素间呈现出连续弹性变形现象,在连续变形接触处,动态磨损量较大使磨损加剧,并出现非均匀磨损.     

含间隙铰链空间对称展开机构动态特性研究

为了研究间隙铰链对空间对称展开机构动态特性的影响,基于一种改进的非线性碰撞力模型,以空间对称展开机构为研究对象,进行3种不同间隙值(c=0. 01 mm、0. 05 mm及0. 1 mm)工况下展开过程的数值模拟及结果对比分析。研究结果表明,因间隙影响,空间展开机构含间隙铰链处的碰撞力、轴-轴承间圆心运动轨迹较理想铰链呈现振荡现象,且间隙值越大,振荡越明显;同时,间隙铰链导致机构展开运动出现明显非线性现象,随着间隙的增大,机构受驱动载荷变化的影响越发明显,甚至诱使处于稳定状态的空间展开机构再次出现动态振荡和非线性现象。     

考虑磨损影响的含间隙机构仿真与试验研究

利用Archard磨损模型计算含间隙机构中的轴磨损,并获得磨损轮廓。利用ADAMS软件建模仿真,研究了磨损间隙对系统动力学特征的影响。随着磨损间隙的变化,轴孔中心之间的加速度响应幅值呈逐渐增加趋势,高幅振动位置随磨损间隙的增加发生一定规律性的变化,即磨损程度与系统振动的振幅和振动时间密切相关。最后通过自制的含间隙曲柄滑块试验装置验证了以上结论。     

含运动副间隙的弹翼展开机构动态特性研究

为探究运动副间隙对某弹翼展开机构动态特性的影响,基于非线性弹簧阻尼模型,建立了弹翼展开机构间隙接触碰撞的数学模型,利用ADAMS软件对机构的展开过程进行动力学仿真分析,分别探究不同间隙大小、数量、材料等因素在机构展开过程中对动态特性的影响,研究结果可供简易制导武器弹翼展开机构的设计及优化参考。     

含间隙铰链舵面传动机构刚柔耦合动态特性研究

为了研究间隙铰链对舵面传动机构动态特性的影响规律,基于一种改进的变刚度法向碰撞力模型,计入杆件弹性因素,分别进行了不同间隙值（c=0、c=δ及c=1.6δ）、不同摩擦因数（0.06、0.08及0.1）工况下舵机角速度、角加速度的数值模拟分析。结果表明,因间隙影响,舵机动态输出角速度、角加速度均呈现明显的振荡现象,且角加速度较角速度振荡幅值更大;同时,在驱动载荷发生变化时,角速度、角加速度均存在较大的波动,但无间隙情况下的波动程度较有间隙情况下更大;此外,间隙铰链处摩擦因数越大,角速度和角加速度振荡幅值越大,并伴随高频振荡和延迟现象。     

含间隙弹性机构动态特性分析

在含间隙刚性连杆机构动力学分析的基础上,建立了含间隙弹性连杆机构动力学模型,计入刚弹耦合作用及间隙对杆件弹性变形的影响,利用该方法对一弹性四连杆机构进行动力分析,采用较为简洁的迭代求解方法,通过算例讨论了几类机构的副反力,杆件变形的情况,计算结果表明,该方法是正确可行的。     

含间隙平面连杆机构动态特性研究

采用非线性弹簧接触力和非线性阻尼描述了含间隙运动副副元素的碰撞接触过程,以此为基础建立了含间隙平面连杆机的动力学模型,通过大量的数值仿真,研究了运动副间隙对机构动态特性的影响及副元素的相对运动过程。首次指出了高速运转条件下,运动副副元素由于弹性变形而出现的连续变形接触现象。     

含间隙机构动态特性分析

将阶跃函数与牛顿第二定律相结合 ,对含间隙的平面连杆机构的分离与碰撞过程建立了统一的数学模型 ,方便了计算机编程的实现。考虑曲柄为非匀速运动 ,计入了杆件的重量及输入扭矩的变化的影响 ,采用了更为精确的求解方法 ,研究了因间隙引起的碰撞、冲击载荷诱发的非线性现象的机理 ,为机构的动态优化设计提供了新思路。     

渣浆泵叶轮轴向间隙流动及泵体动态磨损特性研究

为研究渣浆泵开式叶轮轴向间隙流动结构及泵体动态磨损特性,采用RNGκ-ε湍流模型和离散相模型,对开式叶轮渣浆泵内非定常固液两相流动进行数值模拟,分析了叶轮轴向间隙泄漏流及其与主流的相互干扰作用;建立了渣浆泵泵体动态磨损模型,由UDF函数实现对泵体壁面磨损过程的动态模拟,运用动网格技术实现间隙网格运动区域的动态更新,分析...     

含间隙连杆机构非线性行为研究

分析了间隙铰接触的特点，指出线性弹簧阻尼模型不能满足接触边界条件并产生力突变；采用符合接触边界条件的非线性弹簧阻尼模型描述碰撞分离过程，建立了含间隙曲柄摇杆机构的动力学模型，对含间隙机构的非线性特性进行了分析和讨论，说明含间隙机构动力学行为中存在混沌现象。     

Steels’ wear resistance definition method by their standard mechanical characteristics

The basic regularities of abrasive outwearing for steels of different structural classes are considered. The reliable function bond of steels’ wear resistance with their mechanical characteristics is proved. The correlation of toughness and plasticity with wear resistance is revealed and the new method of steels’ wear resistance definition based on the use of standard mechanical characteristics is offered. The complex criterion for steels’ wear resistance estimation at mechanical outwearing—the product of ultimate strength on relative reduction of area—(σ_b×ψ) characterizes a nature of steels’ outwearing and is reliable enough for determination of wear resistance in conditions of sliding friction, rolling friction on an abrasive and at erosive outwearing. Using offered complex criterion of steels wear resistance, it is possible to determine or estimate the wear resistances of many steels without running their wear tests. The leading role of metal science in the decision of problem of wear resistance increase for equipment working under abrasive wear conditions is marked.     

Thermal wear and electrical sliding wear behaviors of the polyimide modified polymer-matrix pantograph contact strip

In the present study, the polyimide resin (PI)/cashew-modified resin (YM) polymer-matrix pantograph contact strip (PMPCS) was prepared by using hot repressing, hydro-solidification and dipping treatment processes. The thermal properties of cured resins were studied by thermogravimetry analyzer and differential scanning calorimetry. The thermal wear and electrical sliding wear behaviors of PMPCS against copper were evaluated by a ring block wear tester at elevated temperature under dry sliding conditions and a wear tester which simulated the train motion under laboratory conditions, respectively. Worn surfaces and wear debris of PMPCS were analyzed by scanning electron microscopy and energy dispersive spectrometer, and the wear mechanism was discussed. It has been found that the thermal stability of the PI/YM is superior to that of the YM under the same testing conditions. The results also showed that PI/YM-PMPCS had superior wear resistance than that of YM-PMPCS at elevated temperature and with electrical current. At elevated temperature, the wear mechanism of tribological pair evolved from adhesive wear to oxidative wear with mild delamination wear. Arc erosion wear, oxidative wear, and adhesive wear were the dominant mechanisms of tribological pair during the electrical wearing process.     

Effect of counterparts on the friction and wear behavior of polyelectrolyte multilayers

Polyelectrolyte multilayers (PEMs) were prepared on Si substrates by alternative deposition of poly(sodium 4-styrenesulfonate) (PSS) as polyanion and poly (diallyldimethylammonium chloride) (PDDA) as polycation. The PEM film was characterized by means of ultraviolet-visible light absorption spectrometry and atomic force microscopy. The friction and wear behavior of the polymer film sliding against brass, 440C stainless steel, Si₃N₄ and WC balls was evaluated on a microtribometer. It was found that the multilayer film was uniform and compact, and it registered a lowered friction coefficient and extended antiwear life while sliding against soft counterparts, in particular, a brass ball. This could be because the polymeric transfer film had an enhanced adhesion on the soft metallic counterpart in the presence of inter-transferred metallic debris. Contrary to the above, the PEM film had a higher friction coefficient and shorter antiwear life while sliding against Si₃N₄ and WC balls, possibly owing to a higher shearing stress in the presence of stiff and hardly deformable hard counterparts. In other words, the polymeric transfer film on the hard couterparts, if any, would be easily scaled off, leading to decreased antiwear life. Moreover, the differences in the friction and wear behavior of the PEM film sliding against different counterparts were closely related to the differences in the chemical and crystallographic structure of the counterparts (ceramics Si₃N₄ and WC, and metals brass and stainless steel).     

Two-body free-abrasive wear of polyethylene, nylon1010, expoxy and polyurethane coatings

Two-body free-abrasive wear behavior of polyethylene (PE) coatings, nylon1010 (PA1010) coatings, polyurethane (PU) coatings, and expoxy (EP) coatings was investigated. Abrasive wear tests were performed on a turnplate abrasive wear test machine JMM. Hardened and low-temperature tempered steel 45 was used as a reference material. The results shown that in abrasive wear resistance, the PU coatings are approximately 120%, about 5 times larger than the PE coatings and 3 times larger than the PA1010 coatings and the EP coatings, the EP coatings and the PA1010 coatings approach to 40%, and the PE coatings about 20% compared with the reference material (steel 45). Of all the tested polymer coatings, the PU coatings are the best, the PE coatings the worst, and the PA1010 coatings and the EP coatings intermediate. Wear morphologies of the polymer coatings were observed by scanning electron microscope (SEM). Main wear mechanisms of the tested polymer coatings include ploughing wear for the PE coatings and the PA1010 coatings, fatigue wear for the PU coatings and fatigue fracture as well as some brittle fracture and somewhat ploughing wear for the EP coatings.     

一类三自由度含间隙系统的动力学分析

建立了一类三自由度含间隙系统的力学模型,用变步长四阶Runge-Kutta法,通过理论分析和数值仿真结合,研究了该系统倍周期分岔、杈式分岔向混沌的演化路径,为实际应用中的三自由度含间隙机械系统的动力学优化提供了理论依据。     

金刚石切削黑色金属时刀具磨损机理的摩擦磨损试验

为了降低黑色金属金刚石切削过程中的刀具磨损,提高表面加工质量和精度,对刀具磨损机理进行了研究.通过黑色金属金刚石摩擦磨损试验,模拟了实际切削过程中的刀具磨损行为;分别采用扫描电镜(SEM) 、X射线能谱仪(EDS)以及拉曼光谱仪(RS)对工件表面形貌、实验前后工件表面化学组分变化以及金刚石磨损表面的晶体结构转变进行了检测,同时提出了用石墨化程度作为试验过程中评价金刚石磨损的指标.试验结果表明:金刚石的磨损主要与机械力和温度有关,摩擦速度和工件材料中的含碳量对其影响相对较小;石墨化磨损、扩散磨损和氧化磨损等磨损机理共存,其中石墨化为导致金刚石磨损的主要原因.结合红外热像仪测温和热传导理论推算,近似获得了摩擦界面的真实温度,且随着温度升高15％,金刚石石墨化程度显著加剧83％.作者提出,应当综合考虑热-力耦合作用下的刀具磨损机理,以便进一步探寻抑制刀具磨损的工艺措施.     

Intelligent identification of wear mechanism via on-line ferrograph images

Condition based maintenance（CBM） issues a new challenge of real-time monitoring for machine health maintenance. Wear state monitoring becomes the bottle-neck of CBM due to the lack of on-line information acquiring means. The wear mechanism judgment with characteristic wear debris has been widely adopted in off-line wear analysis; however, on-line wear mechanism characterization remains a big problem. In this paper, the wear mechanism identification via on-line ferrograph images is studied. To obtain isolated wear debris in an on-line ferrograph image, the deposition mechanism of wear debris in on-line ferrograph sensor is studied. The study result shows wear debris chain is the main morphology due to local magnetic field around the deposited wear debris. Accordingly, an improved sampling route for on-line wear debris deposition is designed with focus on the self-adjustment deposition time. As a result, isolated wear debris can be obtained in an on-line image, which facilitates the feature extraction of characteristic wear debris. By referring to the knowledge of analytical ferrograph, four dimensionless morphological features, including equivalent dimension, length-width ratio, shape factor, and contour fractal dimension of characteristic wear debris are extracted for distinguishing four typical wear mechanisms including normal, cutting, fatigue, and severe sliding wear. Furthermore, a feed-forward neural network is adopted to construct an automatic wear mechanism identification model. By training with the samples from analytical ferrograph, the model might identify some typical characteristic wear debris in an on-line ferrograph image. This paper performs a meaningful exploratory for on-line wear mechanism analysis, and the obtained results will provide a feasible way for on-line wear state monitoring.     

含多间隙转动铰机构虚拟样机建模与动力学仿真研究

利用实体接触关系建立含间隙转动铰模型,采用非线性弹簧阻尼器接触力和基于速度的摩擦力计算转动铰元素之间的作用力,通过一含多间隙转动铰曲柄摇杆机构的虚拟样机仿真算例,分析转动铰元素之间的相对运动以及间隙对摇杆运动性能的影响,为提高机构性能提供依据.     

汽车链磨损失效机理的试验研究

通过多挂链条的道路行驶试验与台架模拟试验,研究了汽车链的磨损失效机理,微观分析了销轴、套筒和滚子等元件的磨损表面形貌,进而分析其磨损机制。试验分析表明:在汽车链传动中,链条元件存在典型的疲劳磨损和微动磨损,并伴有磨粒磨损和粘着磨损现象。针对这种磨损失效机理及其影响因素,可以有针对性地研究强化汽车链耐磨性的措施,如:合理选取链条元件的材料、采用合理的强化工艺以及合理选择汽车链传动的润滑剂和润滑方式等。