Optimization of Deep Cryogenic Treatment Process for 100Cr6 Bearing Steel Using the Grey-Taguchi Method

This article presents a method for optimizing the deep cryogenic treatment (DCT) process parameters for 100Cr6 bearing steel, based on the Taguchi method with Grey relational analysis. The DCT parameters considered for the optimization included the cooling rate, soaking temperature, soaking time, and tempering temperature, with the quality targets of dimensional stability, wear resistance, and hardness. As per the Grey-Taguchi technique, nine experimental trials based on the L₉ (3⁴) orthogonal array were conducted. The optimum parameters for 100Cr6 bearing steel were arrived at based on Grey relational analysis. Analysis of variance (ANOVA) was performed and soaking temperature was identified as the most influential factor in deep cryogenic treatment of 100Cr6 bearing steel. The improvement in dimensional stability, wear resistance, and hardness of the deep cryotreated samples under optimized treatment conditions was 13.77, 49.02, and 19.35%, respectively. A microstructural examination was carried out to identify the possible mechanism of cryogenic treatment in improving the properties of the 100Cr6 bearing steel. A confirmation test was subsequently conducted to validate the test results.     

Effect of Fluid Inertia on Journal Bearing Parameters

In the modeling and analysis of rotordynamic systems with journal bearings, the stiffness and damping parameters are usually obtained from the Reynolds equation of hydrodynamic lubrication. The Reynolds equation is derived from the continuity and momentum equations with several assumptions; the principal one among them being that the inertia terms are negligible since the lubricant flow is viscosity-dominated. Some previous work has shown, however, that the effect of fluid inertia on the static and dynamic properties of a bearing is not negligible in many circumstances.

This paper uses a perturbation approach to present a rigorous derivation of the correction terms to be added to account for the effect of inertia in the case of a journal on a short bearing. The governing equation for pressure correction is derived and the corrected stiffness, damping, and inertia coefficients to the first order are displayed as a function of the equilibrium position.     

Inertia Effect on the Load Capacity of Large Water-Lubricated Thrust Bearing

With an assumption that the profile of the velocity is not affected by the inertia force, a numerical model based on an extended Reynolds equation, which takes the full inertia effect and turbulence into account, is established. A finite deference method is used to solve the equation and the numerical results are validated with numerical and experimental results. A simplified expression is derived theoretically and modified by the numerical results of the established model. Finally, a study of a large water-lubricated tilting pad thrust bearing is presented. The analytical results and numerical results agree well. A quantitative analysis of inertia effects on load capacity is made in this article.     

流体惯性对橡胶轴承水润滑性能的影响

以水润滑橡胶轴承的典型数值为例,说明轴承流动状态跨越了层流、第二层流区以及紊流3个区域。从连续性方程和Navier-Stokes方程出发,推导了适用于第二层流区的考虑惯性力的雷诺方程。通过数值计算,考察了流体惯性对圆柱轴承润滑性能和承载能力的影响。发现流体惯性导致水膜压力和承载能力略微增大,轴心平衡位置发生微小改变,可以认为在第二层流区流体惯性对橡胶轴承水润滑性能的影响甚微。     

Cutting tool condition monitoring by analyzing surface roughness,work piece vibration and volume of metal removed for AISI 1040 steel in boring

The vibration is one of the intensive problems in boring process. Machining and tool wear are affected more by vibration of tool due to length of boring bar. The present work is to estimate the effect of cutting parameters on work piece vibration, roughness on machined surface and volume of metal removed in boring of steel (AISI1040). A laser Doppler vibrometer (LDV) was used for online data acquisition and a high-speed FFT analyzer used to process the AOE signals for work piece vibration. A design of experiments was prepared with eight experiments with two levels of cutting parameters such as spindle rotational speed, feed rate and tool nose radius. Taguchi method has been used to optimize the cutting parameters and a multiple regression analysis is done to obtain the empirical relation of Tool life with roughness of machined surface, volume of metal removed and amplitude of work piece vibrations.     

Optimization of surface roughness,cutting force and tool wear of nitrogen alloyed duplex stainless steel in a dry turning process using Taguchi method

In this work, the dry turning parameters of two different grades of nitrogen alloyed duplex stainless steel are optimized by using Taguchi method. The turning operations were carried out with TiC and TiCN coated carbide cutting tool inserts. The experiments were conducted at three different cutting speeds (80, 100 and 120 m/min) with three different feed rates (0.04, 0.08 and 0.12 mm/rev) and a constant depth of cut (0.5 mm). The cutting parameters are optimized using signal to noise ratio and the analysis of variance. The effects of cutting speed and feed rate on surface roughness, cutting force and tool wear were analyzed. The results revealed that the feed rate is the more significant parameter influencing the surface roughness and cutting force. The cutting speed was identified as the more significant parameter influencing the tool wear. Tool wear was analyzed using scanning electron microscope image. The confirmation tests are carried out at optimum cutting conditions. The results at optimum cutting condition are predicted using estimated signal to noise ratio equation. The predicted results are found to be closer to experimental results within 8% deviations.     

滚柱轴承离合器的运动及受力分析

对滚柱轴承离合器进行了运动及受力的分析,推导了滚柱轴承离合器轴向位移量ΔＬ与工作扭矩Ｍ之间的关系,并讨论了载荷与应力分布和预紧弹簧的预紧力,为我国开发设计同类产品提供了理论依据。     

液力偶合器的泄漏原因及防治

本文主要分析了液力偶合器的泄漏部位及泄漏原因,提出了液力偶合器泄漏的防治原则和防治措施。     

轴质量对用液体油膜轴承支承转子动特性的影响

本文研究了轴质量对支承于液体油膜轴承上的转子的影响.转子假定是位于弹性轴中部的薄盘,它考虑非零弹性轴质量由液体油膜轴承支承.该径向轴承假定为短简易型,用纵向的和相互作用的刚度及阻尼系数表示,这些系数与系统的角速度有关.假定转于由一电机加速,假定电机速度由一两阶传递函数控制.仿真结果表示质量比的小值,它由轴质量对盘质量比...     

Dynamic Forging of Splines and Spur Gear Forms: A Modified Upper Bound Analysis that Includes the Effects of Inertia and Some Experiments

To analyse dynamic forging of splines and spur gear forms, the upper bound solutions developed earlier for similar quasistatic cases for spline and spur gear form forging were modified suitably to take account of the inertia forces. In the experimental investigation, initially solid cylindrical billets made of tellurium lead were deformed into these shapes, i.e. splines and spur gear forms, using low velocity dropweight impact conditions and the characteristic die load–time and die movement–time results observed. From these results, the typical die load–die movement curves were evaluated in each of these cases, and compared with the estimates based on the modified analysis. Though the dynamic forging loads in each of these cases were, in general, 20%–40% higher than those observed when tested under similar quasistatic conditions, the estimated dynamic forging loads employing the modified upper bound analysis, taking account of the inertia, as given here, showed good correlations with the experiments. These and other results observed on the progressive changes in shapes of the specimens under dynamic loading conditions are given and the results commented upon.     

基于轴向力/径向力解耦的圆锥电磁轴承设计方法

由于圆锥电磁轴承所固有的几何耦合,轴承的设计相对而言需要考虑的结构参数更多,参数间相互影响、相互制约的关系也更复杂。为此,本文提出了一套描述圆锥电磁轴承的特征变量,实现了圆锥电磁轴承的轴向/径向力的解耦。同时,为圆锥电磁轴承提供了一套标准、规范的设计方法。     

On the Fluid Flow and Thermal Analysis of a Compliant Surface Foil Bearing and Seal

Foil gas bearings have been applied successfully to a wide range of high-speed rotating machinery such as air cycle machines (ACMs) and auxiliary power units (APUs). The performance of these bearings are based on the high pressure gas in a very thin layer between the journal and the bearing governed by the Reynolds equations. Generation of heat in these bearings especially at high journal rotating speed and high loads or at high ambient temperature directly affect their performance. Thermal and fluid flow analysis of an advanced compliant foil journal bearing/seal are presented. The side flow (known as leakage) and the approximate temperatures are the results of this analysis. The result of preliminary analysis shows that the major portion of the heat is carried through conduction and using the modified Couette flow approximation for the present working fluid, air, helped in analysis of the temperature magnitude, which can be related to the gas viscosity behavior and thin gas film thicknesses.     

Stability of Rotors Under the Combined Influence of Fluid Film Bearing Characteristics and Shaft Material Damping

Fluid film characteristics and shaft material damping form an interesting combination in rotor dynamic applications. Under certain conditions, a rotor which is unstable due to the damping, can be stabilized with the proper choice of fluid film bearings as supports. On the other hand, increasing the material damping in the rotor shaft can attenuate stress fluctuations in the rotors supported by fluid film bearings. The influence of the above combination on the stability of rotor bearing systems is investigated using a Jeff cot rotor with significant material damping and supported by fluid film bearings in the rotor dynamic model. The results indicate that under certain conditions, the interaction of the above two factors can be gainfully utilized in the design of rotor bearing systems.     

A Study of the Effect of Wear Particles and Adhesive Wear at High Contact Pressures

The wear rate and friction characteristics were determined for certain combinations of cobalt base alloys and stainless steels when rubbed together at unit pressures up to 300,000 psi in an environment of demineralized water at room temperature. Wear rate and friction data were collected both in the presence and absence of wear particles. A study was also made on the effect of sliding-surface geometry in trapping wear particles.

The results suggest that an exponential relationship exists between wear rate and stress for the materials of test and this relationship is influenced by material combinations and sliding velocity. Entrapped wear particles also affect the wear rate.

Because the wear rate appears to increase sharply at some nominal contact stress when the data is plotted on Cartesian coordinates, the authors define an “Apparent Critical Stress”, using this term and a wear factor term to aid in the evaluation and discussion of results.     

Effect of Impeller Geometry,Rotational Speed,and Fluid Properties on Seal Chamber Flow

Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV) are used to measure the three components of the flow velocity in the seal chamber of a mechanical pusher seal at three shaft rotational speeds of 1000, 1800, and 3600 rpm. The flow details in the narrow gap region between the rotor and the stator are also measured. The Taylor numbers corresponding to the three rotational speeds with water and a lightweight heat transfer mineral oil used as process fluids varied between 1.087 × 10⁷ and 9.48 × 10¹⁰. A smaller size impeller with diameter 12.7 cm compared with 25.4 cm diameter impeller used in previous works, was used in this research. Large differences are observed between flow structures in the seal chamber flow for oil and water. The effect of impeller size and the location of balance holes on the seal chamber flow for water at rotational speed of 1800 rpm is presented     

数控机床工作台与导轨部件对进给爬行的影响

数控机床在低速进给时,产生非匀速爬行,对加工精度和工件表面质量非常不利。应用控制理论对机床进给系统的爬行现象进行了理论分析,建立了进给系统的数学模型,用有限差分法对模型进行了模拟。在此基础上,系统研究了各种因素对爬行的影响,着重分析了工作台与导轨的摩擦对爬行起的作用,并且对不同摩擦力工作状态下的系统进行了对比,最后进行了实际测试验证。     

Effect of Diamond-Like Carbon Coatings on Ball Bearing Performance in Normal,Oil-Starved,and Debris-Damaged Conditions

In this study, a process was developed to deposit wear-resistant metal-doped diamond-like amorphous hydrocarbon and carbon coatings onto spherical rolling elements. Nanocomposite WC/a-C:H, TiC/a-C, and Ti/a-C:H coatings were applied in a closed-field unbalanced magnetron sputtering system and their mechanical, compositional, and microstructural properties were examined. The ability of the coated spherical rolling elements to affect bearing performance in normal, oil-starved, and debris-damaged conditions was evaluated in thrust bearing tests. WC/a-C:H-coated spherical rolling elements (balls) exhibit the ability to improve bearing performance in normal, oil-starved, and debris-damaged conditions.     

轴承预紧力和跨距对主轴动态特性的影响

基于ABAQUS采用有限元分析法分析了主轴动态特性,主要研究了轴承预紧力和支撑跨距对主轴动态特性的影响,在同时考虑轴向预紧和主轴自重对轴承刚度的影响的情况下,计算得到不同预紧力和过盈配合下组配轴承的径向刚度,拟合了固有频率随轴承预紧力和支撑跨距变化的经验公式。结果表明:轴承预紧力相比过盈量对组配轴承刚度的影响更为明显。主轴系统的固有频率随轴承预紧力的增加而增大,相同的刚度下,轴承支承跨距的增加系统固有频率随之增大。     

结构刚度和阻尼对箔片轴承承载力的影响

从承载力系数出发，分析了箔片轴承在周向、轴向和径向3个空间方向的结构刚度的变化对箔片轴承承载力的影响。箔片轴承的阻尼主要表现为库仑摩擦阻尼；阻尼的增大使轴承结构刚度增大，稳定性提高，承载力增大。本文还以承载力系数为依据，比较了提高箔片轴承承载力的方法。