Wave Journal Bearing with Compressible Lubricant—Part II: A Comparison of the Wave Bearing with a Wave-Groove Bearing and a Lobe Bearing

To identify the potential advantages of the wave journal bearing, a three-wave journal bearing was compared to both a three-wave-groove bearing (a wave bearing with axial grooves that isolate each wave) and a three-lobe bearing. The lobe bearing's profile was selected to approximate the wave journal bearing's profile. The lubricant was assumed to be compressible (gas). The bearing number, A, was parameterized from 0.01 to 100, and the eccentricity ratio, ε, was varied from 0 to 0.4. Data at bearing numbers 0.1, 1, and 50, and eccentricity ratios of 0.1 and 0.4, were selected as representative of the bearing performance. The calculated load capacity and the critical mass are presented for the three bearings. The wave bearing shows a better load capacity than the other bearings at any applied load and running regime. However, at high bearing numbers the lubricant compressibility effect is predominant and all three analyzed bearings show similar load capacity. The critical masses of the wave-groove and lobe bearing are greater than the critical mass of the wave bearing if the applied load is small. For low and intermediate bearing numbers the wave-groove bearing is more stable than the other bearings especially at low wave's amplitude ratio. The lobe bearing is more stable than the other analyzed bearings at high bearing numbers or at large preload ratios. If the applied load increases, the wave bearing dynamic performance is competitive with both wave-groove and lobe bearings. In addition, at high bearing numbers, the wave bearing could run stably for any allocated rotor mass over a wide range of wave position angle. Three wave bearings are more sensitive to the direction of the applied load than the other bearings especially at low and intermediate bearing numbers. Therefore, a careful selection of the waves position angle has to be done to maximize the wave bearing performance.     

Wave Journal Bearing with Compressible Lubricant—Part I: The Wave Bearing Concept and a Comparison to the Plain Circular Bearing

To improve hydrodynamic journal bearing steady-stale and dynamic performance, a new bearing concept, the wave journal bearing, was developed at the author's lab. This concept features a waved inner bearing diameter. Compared to other alternative bearing geometries used to improve bearing performance such as spiral or herringbone grooves, steps, etc., the wave bearing's design is relatively simple and allows the shaft to rotate in either direction. A three-wave bearing operating with a compressible lubricant; i.e., gas, is analyzed using a numerical code. Its performance is compared to a plain (truly) circular bearing over a broad range of bearing working parameters, e.g., bearing numbers from 0.01 to 100. The geometry of the wave bearing gives the bearing its high load; i.e., stiffness, and stability characteristics. The wave bearing's performance is dependent upon the amplitude of the wave and the position of the waves relative to the applied load. To maximize wave bearing performance, the waves' position relative to the applied load should be carefully selected. The wave journal bearing offers better stability than the plain circular bearing' under all operating conditions and all wave-load orientations. Specifically, an unloaded journal bearing can be made to run stably in any operating regime by incorporating the wave geometry.     

Thermohydrodynamic Analysis of a Journal Bearing in a Turbulent Flow Regime—Part II: Application to an Axial Groove Bearing

The governing equations developed in (1), where a perturbation method is applied in the equation of motion and the energy equation is linearized, are used to study journal bearings of finite length operating in turbulent flow regimes. The thermohydrodynamic solutions are obtained for a journal bearing with four axial grooves. Heshmat and Pinkus' mixing theory (2) is used to evaluate the inlet temperature of each sector. These governing equations are solved to yield pressure, mass-mean velocity and temperature distributions, the mixing temperature at the inlet and the flow rates at the entry and exit of each sector, and the fictional forces.     

Scuffing Behavior of Piston-Pin/Bore Bearing in Mixed Lubrication—Part II: Scuffing Mechanism and Failure Criterion

Surfaces and subsurfaces of test specimens that failed in scuffing were examined. A scuffing criterion is developed stating that scuffing failure would occur when the maximum surface tangential traction is larger than the modified shear strength. A scuffing uncertainty factor is introduced to reflect the influence of factors that affect wear and scuffing and the inaccuracy in modeling.     

Microstructure–Property Relationships in M50-NiL and P675 Case-Hardened Bearing Steels

Case-hardened steels, widely used in high-performance ball and roller bearings, have high surface hardness and a gradient in material properties (hardness, yield strength, etc.) as a function of depth; therefore, they behave as functionally graded materials. Understanding the mechanical properties due to gradients in the subsurface microstructure of case-hardened steels is important for modeling the effects of cyclic damage induced by rolling contact fatigue. In the current study, two different commercially available case-carburized steels (P675, M-50 NiL) and two through-hardened steels (M-50, case P675) were characterized to obtain relationships among the volume fraction of subsurface carbides, indentation hardness, elastic modulus, and yield strength as a function of depth. A variety of methods including microindentation, nanoindentation, ultrasonic measurements, compression testing, rule of mixtures, and upper and lower bound models were used to determine the above relationships and compare the experimental results with model predictions. In addition, the morphology, composition, and properties of the carbide particles are also discussed. It was found that the subsurface hardness and volume fraction of carbides are linearly related. Finally, it was found that the estimation of composite modulus from a well-established model compares with measurements from the ultrasonic method and compression tests. The results presented are of immediate engineering relevance to the bearing industry, with importance to modeling of microstructure and its effects on rolling contact fatigue life.     

A Model for Rolling Bearing Life with Surface and Subsurface Survival—Tribological Effects

Until now the estimation of rolling bearing life has been based on engineering models that consider an equivalent stress, originated beneath the contact surface, that is applied to the stressed volume of the rolling contact. Through the years, fatigue surface–originated failures, resulting from reduced lubrication or contamination, have been incorporated into the estimation of the bearing life by applying a penalty to the overall equivalent stress of the rolling contact. Due to this simplification, the accounting of some specific failure modes originated directly at the surface of the rolling contact can be challenging. In the present article, this issue is addressed by developing a general approach for rolling contact life in which the surface-originated damage is explicitly formulated into the basic fatigue equations of the rolling contact. This is achieved by introducing a function to describe surface-originated failures and coupling it with the traditional subsurface-originated fatigue risk of the rolling contact. The article presents the fundamental theory of the new model and its general behavior. The ability of the present general method to provide an account for the surface–subsurface competing fatigue mechanisms taking place in rolling bearings is discussed with reference to endurance testing data.     

Experimental Identification of Bearing Dynamic Force Coefficients in A Flexible Rotor—Further Developments

Bearing force coefficients are a necessary component in the analysis of linear stability and response of rotating dynamic systems. Often, these bearing parameters are predicted using limited or restrictive flow models, or operating conditions in the actual machine differ largely from the assumed conditions during the analysis. In these instances, the identification of actual support properties represents a means to verify the rotordynamic predictions.

The current work presents an identification procedure that is suitable for implementation in the field and that relies on measurements of rotor synchronous response to calibrated imbalance. The method is extended to the typical case when the displacement measurements occur away from the bearing locations in flexible rotor systems. Measurements and identification are performed on a test rotor supported on a pair of identical two-lobe fluid film bearings and for increasing values of imbalance over a speed range from 1,000 to 4,000 rpm. Identification using increased imbalances reveals the linear region of response in which the procedure renders reliable results. Also, a signal noise study shows that the method is robust to random external disturbances with a noise-to-signal ratio of up to 10%.

     

Thermohydrodynamic Analysis of a Journal Bearing in a Turbulent Flow Regime—Part I: Theory

An attempt is made to formulate a thermohydrodynamic model of fluid-film lubrication that is valid in turbulent flow regimes. The model considers the flow to be a small perturbation of turbulent Couette flow. The modified Reynolds equation is obtained for the turbulent flow and the integro-differential energy equation makes the turbulence analysis easier by replacing the conductive terms in terms of the convective boundary conditions at two solid surfaces. Sample results applying the perturbation method agree well with available experimental data and theoretical methods.     

Tribotechnology in Japan — today and tomorrow

In recent research in tribology, emphasis has been given to the problems which have developed in new industrial fields such as mechatronics, and to the new materials and lubricants which are able to withstand extreme conditions. The Research Committee for the Survey of Future Directions of Tribology Research (SFDTR) was established in 1983 by the Japan Society of Lubrication Engineers to grasp the current state of tribology research and what tribotechnology will be needed in future. The surveys, based on discussions with research and engineering staff in various industries, included: tribological problems, current tribological research and development within industries, and insights into the future trends of tribology. This paper summarizes, according to machine elements, the major results of these surveys.     

Comparison of the Dynamic Behavior and Lubrication Characteristics of a Reciprocating Compressor Crankshaft in Both Finite and Short Bearing Models©

The compression force of refrigerant gas, the viscous and inertial force of the piston, and the centrifugal force of balancer weight induce rotating whirl of the crankshaft in a small reciprocating compressor. It is necessary to develop an analytical model for the accurate prediction of dynamic behavior of the compressor mechanism having coupled characteristics between the piston and crankshaft. The reciprocating compression mechanism is dynamically modeled by considering the viscous frictional force of a piston and the variation in the contact length of the piston-cylinder system, and then numerical analysis is performed for the coupled dynamic behavior of the piston and crankshaft. For the accurate predictions of the dynamic behavior and characteristics of lubrication of the crankshaft-journal bearing system, a finite bearing model is adopted. In addition, the dynamic trajectory and characteristics of lubrication of the crankshaft such as power consumption and oil leakage are compared between the finite bearing model and the short bearing approximation. The influences of the variation in the radial clearance of the journal bearings, lubricant viscosity, and mass and mass moment of inertia of the piston and connecting rod on the dynamic behavior and characteristics of lubrication such as power consumption and oil leakage are investigated.     

Centrally Pivoted Tilting Pad Thrust Bearing with Carbon-Based Coated Collar—Experimental Results of Low- and Medium-Speed Operation

Experimental results of the research on a tilting pad thrust bearing with symmetrical pad support in the conditions of high loads and low speeds are presented in the paper. As described in the literature review, experimental results of tilting pad bearings at low speed/high load regime and transient conditions are rare. Unusual material selection - steel pad against a DLC-type coating on the collar was utilized. Such material combination has been mostly used in automotive industry in concentrated contact friction pairs, but it is not commonly used in thick film contacts. The tests included low speed high load and a test, where a Stribeck curve was reproduced. The steel pads showed minimum traces of contact and no visible wear was noticed on the collar coating. Differences of operation in medium and low speed were observed. Big variations of bearing temperature at medium speed and almost constant pad temperature at low speed were measured. At a specific load of 5 MPa transition to mixed friction was occurring at a sliding speed of approx. 0.18 m/s.     

Optimization in engineering problems—Analysis and generalizations

The main results of researches in the sphere of designing, identification, designing of regulated systems and development of test samples are presented. Examples of the application of the Parameter Space Research Method in different fields of science, industry and training courses are given. Some tasks of the strategy of solving of engineering problems and their optimization are discussed.     

Anti-Shudder Properties of ATFs—An Investigation into Friction Modifying Mechanisms Using VSFT and SAE No. 2 Tests

In recent years, continuous slip torque converter clutches (CSTCCs) have been widely used in automatic transmissions, mainly to improve fuel efficiency. With the adoption of these devices the problem of shudder vibration has arisen. To help alleviate this problem, better anti-shudder characteristics are desired for automatic transmission fluids (ATFs). Positive μ-v curves are well recognized to correlate to the avoidance of shudder. A variable-speed friction tester (VSFT), which combines a low-velocity friction apparatus (LVFA)-type test with the ability to age an oil in situ, was used to determine friction characteristics of four model ATF formulations in a wet clutch tribosystem. The linear-defined multiple parameter spider chart ATF evaluation (LSAE) method was applied to present the ATF's overall friction results including anti-shudder performance and durability (Zhao, et al. (1)). One modified SAE No. 2 test was also used to test the four oils’ friction behavior, to compare with the VSFT results. Similar performance rankings have been obtained from those two tests. Both test results and evaluation parameters will be discussed in this article and the response will be linked to the physical parameters defining the posttest surface. The oil absorption ability of post test friction material is shown to be important to the overall friction performance. The environmental scanning electron microscope (ESEM) images and 3D profiling results showed that some surface topographical parameters, such as V_vc (void volume of the core) and V_vv (void volume of valleys), can be linked with the friction modifying mechanisms in the ATF tests.     

Specific Film Thickness—A Closer Examination of the Effects of EHL Film Thickness and Surface Roughness on Bearing Fatigue

Analysis of literature bearing-fatigue life results shows that fatigue life is not a simple function of the widely accepted specific film thickness, λ, which is the ratio of the EHL film thickness h to composite surface roughness [sgrave]. Instead, the influence of film thickness on bearing life increases with increasing surface roughness; at about 0.20 micrometer (8 microinch) composite roughness life increases with the square root of h while at about 0.46 micrometer (18 microinches) life increases with h squared.

The negative effect of surface roughness on bearing life appears to be relatively independent of film thickness. This suggests that surface roughness affects fatigue life by some mechanism in addition to the degree of interaction of asperities through an intervening EHL film. Additional test results are needed to confirm this point.     

Spindle deflections in high-speed machine tools — Modelling and simulation

This research attempts to develop spindle deflection error models for high-speed machining systems. A model for determining total spindle deflection at the tool-end is presented. The model incorporates spindle bearing characteristics, shifts in ball contact angles, and centrifugal force and gyroscopic moment effects at high speeds. It uses the transfer matrix method to determine the total deflections at the tool-end based upon the point contact deformations at the individual balls of an angular contact ball-bearing assembly. A simulator is also developed for simulating spindle end deflections for various spindle rotational speeds. The results of the simulation show contact angle variations and peak deflections at particular spindle rotational speeds. Important research issues are also presented.Nomenclature AF final position, inner raceway groove centre - RF initial position, inner raceway groove centre - W final position of ball centre - V initial position of ball centre - D ball diameter, mm - r _o inner raceway groove radius, mm - r _i inner raceway groove radius, mm - M gyroscopic moment, N-mm - FO r _o/D - FI r _i/D - P bearing pitch diameter, mm - K _o outer race load-deflection constant, N/mm^1.5 - K _i inner race load-deflection constant, N/mm^1.5 - CF centrifugal force, N - J mass moment of inertia, N.mm² - l length of spindle, mm - E modulus of elasticity, N/mm² - I moment of inertia of spindle, mm⁴ - Y deflection of spindle alongy-direction, mm - z deflection of spindle alongz-direction, mm - M moment at spindle end, N.mm - V shear force at spindle end, N - m spindle mass, kg - material density - _o outer race contact angle - _i inner race contact angle - nominal contact angle - _i inner race deformation - _o outer race deformation - angle between ball centre of rotation and the horizontal - mis-alignment (in degrees) of shaft assembly measured in a plane perpendicular to shaft axis (x-direction) - W1 ball and raceway angular raceway velocity ratio for outer raceway control - W2 ball orbital and angular raceway velocity ratio for rotating inner raceway and outer raceway control - circumferential ball position - raceway control parameter     

Chongqing Machine Tool Works——TheLargest, Oldest and MOst Famous GearManufacturer in China

Chongqing machine tool works, a leading cylindrical gear manufacturer in China. was established in1936 and is now situated at the scenery bank of Huaxi river in southern suburb of Chongqing city-abeautiful .mountain city in China. It has an enroll ment of 4528 people and 311 of them are techniciansand engineers.Sihce it began to produce gear hobbing machinesin 1953,. five types, twelve series and seventy-threedifferent models & varieties of gear cutting machineshave been developed, including …     

TiSiC,TiSiC-Zr,and TiSiC-Cr Coatings—Corrosion Resistance and Tribological Performance in Saline Solution

TiSiC coatings alloyed with Zr and Cr were deposited on Si and 316 L steel substrates by a cathodic arc method in a CH₄ reactive atmosphere. The corrosion and wear behavior of the coatings in 0.9% NaCl solution was investigated. Corrosion resistance of the coatings was evaluated by electrochemical tests. The electrochemical polarization measurements were conducted at room temperature in the potential range ?1 and 1.5 V, with a 0.167 mVs^?1 scan rate. Compared to the uncoated 316 L substrates, the coated ones showed nobler characteristics, with more electropositive corrosion potentials, lower corrosion current densities, and higher polarization resistances. TiSiC-Zr exhibited the lowest corrosion current density (0.62 μAcm^?2) and the highest protection efficiency (69.5%). The tribological performance of the coatings under corrosive conditions (0.9% NaCl solution) was investigated using a ball-on-disc tribometer (6-mm-diameter sapphire ball, 5 N load, 0.15 ms^?1 sliding speed, 400 m sliding distance). The TiSiC-Cr coating demonstrated the best wear behavior, with a wear rate of 3.2 × 10^?6 mm³N^?1m^?1, followed by TiSiC and TiSiC-Zr. The morphologies and compositions of the worn surfaces were examined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) in order to identify the wear mechanism. Corrosion, debris adhesion, and oxidation were found to be the dominant wear processes.     

Implementation of the WEEE-directive — economic effects and improvement potentials for reuse and recycling in Germany

Reducing the quantity of waste for disposal and saving natural resources were main drivers for the introduction of the European Directive on waste electrical and electronic equipment (WEEE-directive). This policy focused on an extension of the producer responsibility (EPR) to the end-of-life-phase of their products. Because of the EPR concept, the national transposition of the WEEE-directive, especially the German transposition in the law ElektroG, caused changes in the organisation and material flows that are sometimes not in line with the aim of the directive, which is to enforce the waste management premise “avoidance prior recycling prior disposal”. Thus, the objective of this contribution is to analyse and compare the situation before and after implementation of the ElektroG in Germany, and deduce improvement potentials. Therefore, a co-operation of a municipality and a nearby disassembly company in Germany is analysed and evaluated, taking into account material flows and costs before/after implementation of the ElektroG, as well as degrees of freedom. Based on this analysis, recommendations are deduced for political decision makers and actors of the WEEE treatment system.