超声辅助内圆磨削40Cr15Mo2VN轴承套圈的试验研究#br#

针对传统加工方式难以获得轴承套圈较小的表面粗糙度和表面波纹度的问题,采用超声辅助内圆磨削的加工方法来改善轴承套圈的表面质量。基于超声内圆磨削单颗磨粒运动轨迹分析,建立了表面粗糙度的理论模型,通过对轴承套圈进行超声内圆磨削试验,研究了各个加工参数对轴承表面质量的影响。研究结果表明：超声内圆磨削加工方法可明显改善轴承的表面质量;增大超声振幅可减小表面粗糙度而表面波纹度会先减小后增大;随着砂轮转速的增大,表面粗糙度及表面波纹度会先减小后增大;磨削深度和进给速度的增大会使表面粗糙度及表面波纹度增大,但超声内圆磨削可减小它们的增加量。     

A Study on the Influence of Waviness Error to a Hydrostatic Bearing for a Crankshaft Pin Turner

This article describes a theoretical analysis of a hydrostatic journal bearing for a crankshaft pin turner by considering the waviness error of the journal and bearing. The authors found adequate design parameters to operate the crankshaft pin turner bearing. The flow rate, radial clearance, and eccentricity were selected as the basic design parameters. The load-carrying capacity of the bearing as a function of the design parameters was studied in the case of a true circular journal and bearing. The influence of the waviness error on the load-carrying capacity was then investigated; cosine functions were selected for the waviness functions. As a result, the load-carrying capacity varied according to the amplitude and phase angle of the waviness functions. Thus, it was found that the influence of the waviness error is a significant factor in analyzing lubrication characteristics.

Run-out accuracy analysis method according to the waviness phase angles of the journal and bearing was suggested. It was found that the phase angles between the bearing load wave and load-carrying capacity wave are important factors that affect the running accuracy in addition to the amplitude of waviness error.     

表面波纹度对滑动轴承转子系统稳定性的影响

为揭示表面波纹度对滑动轴承转子系统稳定性的影响,建立了考虑表面波纹度的滑动轴承转子系统动力学模型,提出其非线性动力学分析、计算方法,表征出周向表面波纹、轴向表面波纹以及组合表面波纹等不同形式的表面波纹度对系统稳定性等系统特性的影响。研究结果表明,表面波纹度的存在会使系统油膜产生波动,增加系统的能量损失,特别是当Sommerfeld数S<0.2时,表面波纹度对系统能量损失的影响最明显。但它的存在并非都有害,表面波纹度误差的存在会在一定程度上有利于滑动轴承转子系统稳定性及承载特性,且随着波纹幅值的增高,其促进的作用越明显。此外,不同形式表面波纹度对系统特性的影响程度也不同,轴向表面波纹度对系统承载能力的促进作用比周向表面波纹度及组合表面波纹更大,而周向表面波纹度则对系统稳定性及能量损失性的影响作用更明显。当Sommerfeld数S>0.5时,轴向表面波纹度对稳定性的影响较小。     

Investigation of the burnishing process with PCD tool on non-ferrous metals

It is well known that the no-chip machining process, burnishing, can easily improve surface roughness, waviness and hardness. To get the practical useful parameters, the effects of various burnishing parameters (spindle speed, depth, feed, burnishing radius and lathe) on surface roughness and waviness of the non-ferrous components were studied experimentally with a theoretical analysis. The experiments were conducted with a simply designed cylindrical surfaced polycrystalline diamond tool developed by us. It was found that smaller parameters do not mean lower surface roughness or waviness and different optimum burnishing parameters can be got under different burnishing conditions.     

微观表面形貌对螺旋槽液膜密封空化发生的影响

为探索微观表面形貌对液膜密封空化的影响,基于满足质量守恒的JFO空化模型及坐标变换,建立考虑微观表面形貌的双坝区螺旋槽液膜密封数学模型;采用有限体积法离散求解控制方程,综合分析表面粗糙度、周向波度和径向锥度对螺旋槽液膜密封空化发生的影响规律。结果表明:相比而言,密封面计入微观表面形貌后,摩擦副液膜中空穴区发生位置分散且形状不规则;以空化面积比为判据,较大表面粗糙度对液膜空化促生虽起到积极作用,但数据较小,可忽略不计;锥度对液膜中空穴促生和抑制影响有限,波幅的增加显著促进液膜中空穴的发生;高频波数时,正锥度有利于降低液膜空化面积比,抑制空穴。     

Analysis and optimization of dynamic response of air bearing sliders to disk waviness

Flying stability has been becoming more critical for air bearing sliders with extremely low flying height (FH). Therefore, the effects of disk waviness on flying height modulation (FHM) cannot be neglected. This paper presents an analytical study on the mechanism of FHM of air bearing sliders due to disk waviness, and a design optimization for increasing waviness following ability of sliders. An analytical three-degree-of-freedom (3-DOF) model is developed, where the air bearings are modeled as six lumped linear springs and dampers. The purpose of this model is to develop a quantitative understanding of how air bearing sliders respond to disk waviness. The dynamic characteristics of the slider-air bearing system are then analyzed, and the closed-form frequency resonance function (FRF) of FHM to disk waviness is derived. The impact of disk surface features and the positions of the trailing pad, the side pads, the leading pads and the negative pressure center on FHM are also investigated using parametric analysis. The analysis results show that the improvement of the roll-off characteristics of the disk surface waviness can also decrease the FHM. In addition, shortening the distance between the trailing pad pressure center and the head position, moving backward the side pads and leading pads and forward the negative pressure center can increase waviness following ability of the slider. Finally, an air bearing slider is designed according to the proposed design strategies for reducing the FHM due to disk waviness.     

波纹度波数对深沟球轴承振动特性的影响

建立了三自由度轴承动力学模型和波纹度模型,以6201深沟球轴承为研究对象,基于定步长四阶龙格-库塔法得到轴承振动频率和振动加速度,分别通过与文献和试验结果的对比,验证了模型的正确性.并分析了内外圈波纹度波数对轴承加速度峰峰值和有效值的影响,结果表明:轴承振动加速度响应的峰峰值和有效值随内外圈波纹度波数增大而增大,波纹度...     

粗糙度各向异性对润滑接触面摩擦的影响

齿轮、轴承、凸轮等重载接触副的性能受表面粗糙度的显著影响。高负载情况下的摩擦因数与润滑接触面粗糙度的各向异性相关。测量的表面粗糙度可以分解为一系列具有不同波长、幅值的正弦表面粗糙度,因此,考虑各向异性正弦表面粗糙度,构建粗糙表面点接触瞬态弹性流体动力润滑(TEHL)模型,提出基于多重网格算法的粗网格构造新方法,提高粗糙表面润滑问题求解的稳健性。研究表面粗糙度各向异性对高负载情况下摩擦因数的影响规律。结果表明,粗糙度的各向异性影响接触面压力、油膜厚度分布、粗糙度形变量,从而影响摩擦因数。提出一个组合函数来量化粗糙度各向异性对摩擦因数的影响,表明全膜润滑到混合润滑的过渡不仅与载荷、速度等工况参数相关,还与粗糙度各向异性相关。     

Surface Roughness Effect on Slider Bearing Lubrication

The effect of roughness of surfaces of a slider bearing on the load-carrying capacity and friction force, is studied. The distinction is made between waviness and roughness, the latter being treated as a random quantity which may be characterized by a probability density function, determined experimentally. Results can be obtained in closed form suitable for calculation if a Beta distribution is assumed. Actually, this can approximate quite closely a Gaussian distribution, yielding quite accurate results. However, the procedure developed can be carried out for any desired distribution.     

Contact-induced off-track vibrations of air bearing-slider-suspension system in hard disk drives

Contact-induced vibration of air bearing-slider-suspension system is a crucial issue for slider flying stability and head positioning precision of 1 Tbit/in² hard disk drives. In this paper, the contact-induced off-track vibrations of air bearing-slider-suspension system are investigated by simulation. A dynamic simulator is developed to calculate the interactions between the air bearing dynamics and vibrations of slider-suspension assembly. The simulation model consists of a finite element model of suspension assembly, an air bearing model based on the generalized lubrication equation, and a slider–disk contact model based on the probability distributions of surface roughness. A sequential method is used to couple all these models and analyses. The time history of the slider and suspension motions, together with the time-varying forces including air bearing force, air shear forces, contact force and friction force can be obtained. The effects of different contact conditions, such as the contact intensity, friction coefficient, and disk surface waviness on off-track vibrations are investigated numerically in details. The results reveal some mechanisms on how these factors contribute to the off-track vibrations of suspension assembly.     

Convection of Heat in Short-Bearings and Face Seals

For a short bearing or face seal, the temperature is determined by a steady Couette flow component and a zero-average perturbation, or waviness. In terms of these component flows, convection along the film and conduction into the surfaces is derived, and conditions are determined under which convection significantly influences the circumferential distribution of heat flux into the solid surfaces. For a stationary sinusoidal wave on a bearing surface, the phase relationship between this displacement perturbation and the wall heat input is found. The result is primarily of interest in systems where frictional heating may excite the thermoelastic growth of surface waviness, and where weak perturbations on heating may excite thermoelastic instability.     

Fitting of robust reference surface based on least absolute deviations

Engineering surfaces comprise shape deviations namely form, waviness and roughness. For characterization of roughness, form and waviness are separated from the measured surface by establishing a reference surface that represents these deviations. This paper presents a new approach of simultaneously separating form and waviness deviations by fitting a reference surface that remains robust against the outliers such as deep grooves. A second degree polynomial and a set of sinusoidal functions are taken as basis functions to represent form and waviness respectively. A criterion of minimization of sum of absolute deviations (L₁-norm) is considered as against the commonly used least squares (L₂-norm) criterion and the reference surface obtained is found to be robust against outliers such as deep valleys in the measured surface. The superiority of the proposed fitting scheme is brought out by testing on different surfaces and comparing with the least squares method of fitting and the robust Gaussian regression filtering.     

The effects of surface irregularities on the performance characteristics of flexible finite journal bearings lubricated with couple stress fluids

A numerical solution for the elastohydrodynamic lubrication of finite journal bearings is presented. Couple stress effects resulting from blending the lubricant with various additives are considered. Elrod's cavitation algorithm, which automatically predicts film rupture and reformation in the bearings, is implemented in the solution scheme. A simple elastic model is used to describe the elastic deformation of the bearing liner. Furthermore, the effects of surface waviness on the performance of the bearing are incorporated into the analysis. A comprehensive study illustrates the effects of couple stress, liner flexibility, and surface waviness on the steady‐state performance of finite‐width journal bearings. The results show that these effects should be considered at higher values of the eccentricity ratio.     

表面横向波形点接触弹流动压性能的研究

物体的表面结构形态在有些场合下对润滑状况有重要的影响作用.本文研究了考虑表面粗糙度的点接触问题的特点,建立了点接触的分析模型和接触物体表面的横向波形数学模型,应用多网格重积分方法求解了在给定条件下其与时间相关的弹流动压性能的解.主要分析了表面横向波形的点接触的润滑性能,揭示了油膜压力、油膜厚度在油膜接触区上随参数变化的特征和规律.     

The effect of particle hardness and shape when abrasive water jet milling titanium alloy Ti6Al4V

Legislative restriction on effluent disposal has resulted in an increase in the environmental costs of chemical milling and replacement methods are being sought. Abrasive water jet cutting (AWJ) is a mature process that is employed to through cut materials that are difficult to process by more conventional methods and the process is also being developed for controlled depth milling (CDM) to produce three-dimensional features which in the past might have been produced by chemical or etching processes. A major problem to be solved when using AWJ as a CDM technique is that of tolerance on depth, surface waviness and surface roughness of the milled area. In the current work, the effects of milling parameters on the surface characteristics are investigated when milling a titanium alloy (Ti6Al4V) with different abrasives, namely white and brown aluminium oxide, garnet, glass beads and steel shot. It has been demonstrated that the ratio between the hardness of the workpiece and the abrasive is more important than particle shape. Material removal rate and surface roughness increased when particle hardness is increased. Shape factor and particle hardness have no significant effect on surface waviness. For the abrasives investigated; traverse speed is shown to govern the operative mechanism of material removal and thus the material removal rate. It is also shown that the surface waviness can be reduced as the traverse speed is increased whilst, the surface roughness is not strongly dependent on traverse speed.     

Precision grinding of bearing steel based on active control of oxide layer state with electrolytic interval dressing

The oxide layer state directly relates to machining quality in electrolytic in-process dressing (ELID) grinding. In this paper, intermittent grinding control strategy was used to monitor and control the state of the oxide layer in interval ELID (ELID II) grinding. Some experiments were implemented based on active control of the oxide layer state. The influence of dressing current, wheel speeds, and grit size on surface roughness and waviness has been discussed in detail with ELID II grinding for bearing steel. The experimental results illustrate that the ELID II method can realize a stable grinding process based on active control of the oxide layer state. The surface roughness (Ra) and waviness (Wa) increase with increase of the dressing current. When the dressing current is constant, Ra and Wa reduce as wheel speed increases and decrease as grain size of wheel decreases. The experimental results also show that sufficient abrasive protrusion can be ensured in ELID II grinding, especially for grinding with a W2.5 super-abrasive wheel which may produce a very smooth surface quality, Ra 0.0166 μm and Wa 0.018 μm.     

球轴承波纹度激振的机理研究

对轴承样品进行了振动测量和波纹度测量,利用样条函数拟合了波纹度曲线及其导数曲线,分析了曲线性质对轴承振动的影响,并根据所建立的球轴承振动模型进行了仿真计算。研究结论对了解轴承振动噪声机理,提高轴承质量有重要作用。     

考虑轴箱轴承表面波纹度的高速车辆振动特性分析

采用SIMPACK动力学软件,建立一高速车辆出现轴箱轴承表面波纹度缺陷的动力学计算模型,将轴承假设为只有外圈和内圈两者之间的相互作用,轴承中的滚子直接等效成若干个力元,分别考虑轴承的内、外圈以及滚子表面波纹度对车辆振动特性的影响。仿真结果表明:当轴承出现波纹度缺陷时,轴箱振动加速度会增大,而构架的加速度变化不大;对于外圈表面波纹度,会在特定频率及其倍频处出现峰值,且当纹度波数等于或接近滚子数目相或其倍数关系时,轴箱会出现严重的振动;对于内圈表面波纹度,当波纹度数N_w≠iZ±1且N_w≠iZ±1(其中i为正整数)时,在所仿真的波数下可能会出现多种基频及其倍频成分,否则只会产生特定的基频及其倍频成分;对于滚子表面波纹度,当滚子波纹度数目为偶数时,只会出现特定的基频及其倍频成分,且在特征频率旁边存在着调制边带;随着滚子波纹度数目的变化,三种情况下的轴箱振动加速度幅值会在波纹度数目等于滚子数目处产生峰值点,且随着波纹度幅值的增加,三种情况下的轴箱的振动均变得越来越剧烈。     

角接触球轴承摩擦力矩波动性分析

针对低摩擦力矩角接触球轴承,利用能量守恒定律,研究角接触球轴承零件工作表面的波纹度对轴承摩擦力矩波动性的影响,从理论上对角接触球轴承零件工作接触表面的波纹度幅值、谐波阶次与轴承摩擦力矩波动性的关系进行分析,给出影响角接触球轴承摩擦力矩波动性的内、外滚道和钢球工作表面的主要波纹度谐波阶次和相应的激振频率,并试验验证.研究...     

粗糙平面滑块油膜形成能力的研究

实践表明,金属摩擦副的润滑性能有可能通过控制其表面几何形貌而获得大大的改善。本文将平均流量模型应用于分析表面精糙的平面滑块轴承的油膜形成能力,从而成功地阐明了这一机理。