1993 Vol.6(1)

Display Mode:          |     

QUALITATIVE CORRELATION BETWEEN THE TRANSITION OF LUBRICATION REGIMES AND CHEMICAL STRUCTURE OF LUBRICATION FILM
1993, 7(1).
[Abstract](2268) [PDF 401KB](103)
Abstract:
In this paper, chemical structure of lubrication film of Mo/ Cr2O3 system in different lubrication regimes was analyzed using x-rays photoelectron spectroscopy (XPS), scanning Auger microprobe (SAM) and scanning electron microprobe (SEM). It was observed that there was a correlation between the transition of lubrication regimes and the chemical structure of lubrication film. Under the boundary lubrication regime, the solid lubrication film on specimen surface consisted of graphite and molybdenum dioxide, which resulted in a good tribological behavior of Mo/Cr2O3 system at high temperature.
A DYNAMIC SYSTEM MODEL FOR RUNNING-IN AND ITS APPLICATIONS
1993, 7(1).
[Abstract](2046) [PDF 303KB](120)
Abstract:
Running-in should be regarded as a convergent process of a dynamic wear system. The wear volume W and the rms of the composite profiles are chosen as the state variables of the system. Two state equations, the wear equation concerning the effect of surface roughness and the rate equation concerning the changes in rms during the running-in process, have been established. The optimum roughness σp and the equilibrium roughness σe, the system stability and critical load carrying capacity, and the optimum loading curve for improving the efficiency of running-in, have been predicted and simulated by the dynamic system model.
FRICTION AND WEAR BEHAVIOR OF SURFACE FUSING COATINGS AND FUNCTINGS OF THE RARE EARTH ADDITIVE
1993, 7(1).
[Abstract](2102) [PDF 470KB](131)
Abstract:
The self-fluxing Ni-based alloy coatings and composite ones with chromium carbide were obtained on the surface of steel by use of a non-vacuum fusing process. The friction and wear behavior of the two kinds of coatings was searched. In order to improve the properties of the coatings, a rare earth additive was added to the coatings and its functions were analyzed. The test results show that the surface fusing coatings possess strong metallurgical bond with the steel substrate, and so do the hard phase particles with the coating matrix; the coatings with the rare earth additive have lower friction coefficient, better wear resistance and can be used on a higher load condition. The functions of the rare earth additive are discussed. Its effect on the composite coating is more efficient in wear resistance.
ANALYSES OF SCUFFING MECHANISM OF SLIDING LUBRICATED LINE CONTACTS
1993, 7(1).
[Abstract](2117) [PDF 232KB](192)
Abstract:
Based on the scuffing experiments of sliding lubricated line contacts, a new scuffing model based on the surface plastic flow has been formulated in this paper. This model hypothesizes that all boundary films (including oxide film) on the surfaces will be breakdowm and scuffing failure will occur when the plastic flow on one of the surface lubricated with non-additive mineral oils comes out. For the friction pairs which are made of GCr15 Steel, Seizure will occur when the ratio of the yield area on the surface to the real contact area reaches 50%. This model can explain the scuffing behavior well and completely. Using the model, the critical scuffing loads have been calculated. The results are in good agreement with experimental data.
ON ACTION MECHANISM OF SOME NON-ACTIVE ANTIWEAR AGENTS
1993, 7(1).
[Abstract](2118) [PDF 378KB](97)
Abstract:
Conventional antiwear agents for lubricants are active chemicals, such as sulphides, phosphates and chlorinates. The action mechanism of these antiwear agents is a kind of "conrolled corrosion". Having no corrosion to metals, some new antiwear agents containing B,N,Si,Al,Sn are named "non-active aniwear agents" by authors. Based on the results of surface analyses, the action mechanism of non-active antiwear agents is suggested that the non-active atoms such as B,N,C,Si,Al,Sn permeate into the surface of metal to form a protecting layer reducing friction and wear.
INFLUENCE OF REAL ROUGHNESSES ON PRESSURE DISTRIBUTIONS AND FILM SHAPES IN ELASTOHYDRODYNAMIC LUBRICATION
1993, 7(1).
[Abstract](2098) [PDF 198KB](142)
Abstract:
The present paper studies on micro-elastohydrodynamic lubrication problems with real rough surfaces in line and point contacts. Random roughness samples are collected from real processed surfaces. Problems with different loads and roughness amplitudes are calculated numerically. From the calculation solutions it is found that pressure peaks and valleys induced by roughness flatten rough surfaces on line and in point contacts because the velocity item in Reynolds equation plays a major role under the heavy loads. Therefore, though pressure distributions become much rough, film shapes are smooth. It is also found that the increment of the maximum pressure is nearly proportional to the maximum amplitude of roughness. And the minimum and the average film thicknesses change slightly with the varivation of rouhgness amplitudes.
APPLICATION OF SYSTEMS ANALYSIS TO IMPROVING THE WEAR CHARACTERISTICS OF DRILLING RIGS' BRAKE PAIRS
1993, 7(1).
[Abstract](2121) [PDF 301KB](80)
Abstract:
On the principle of systems ansalysis and the failure analysis of drilling rigs' brake pairs, a matrix representation was presented, in which the main factors effecting on the wear characteristics of the brake pairs regarded as a tribo-system have been found to be the frictional heating at the interfaces between the brake blocks and rim and the matching character of the materials of brake pairs. Correspondingly, two measures have been described. The one is rationalizing of operating mode or optimizing of design parameters of the brake pairs by means of a group of theoretirial heating-up characteristics curves, the other is screening out the optimum pairing of the materials of brake pairs based upon a series of simulation laboratory tests.
EFFECTS OF PAD AND PIVOT ELASTIC DEFORMATIONS ON TILTING PAD BEARING AND ROTOR SYSTEM DYNAMIC BEHAVIOR
1993, 7(1).
[Abstract](2120) [PDF 296KB](95)
Abstract:
This paper investigates the effects of pad and pivot elastic deformations on tilting pad journal bearing properties and dynamic behavior of rotor system supported on them. Small harmonic oscillations are assumed in deriving the dynamic EHL equations of individual pads and the formulae of pad dymanic properties. Numerical solution and integration are used to get properties of elastically deformable pads. A database of deformable pad properties covering a wide range of practical parameters is set up. It is further transformed to account for pivot deformations. "Assembling" process is used to get bearing properties form the pad database. The minimum film thickness, bearing stiffness, and especially bearing damping, are seen to be significantly affected by pad and pivot deformations. Effects of elastic deformations on rotor system dynamic behavior are shown to be adverse, and unnegligible under circumstances.
EFFECT OF ADDITIVE CHEMISTRY ON THE FRICTION AND WEAR PROPERTIES OF A Cr2O3 COATING
1993, 7(1).
[Abstract](2158) [PDF 355KB](118)
Abstract:
The effects of several lubricating oil additives on the friction and wear properties of Cr2O3 coating were studied with a block-on-ring tester at ambient condition. The results indicate that, relative to the base oil, oleic acid is effective to reduce friction while the others are not; A remarkable wear reduction is obtained by zinc dialkyldithiophosphate (ZDDP), tricesyl phosphate (TCP) and oleic acid but not by sulphurized olefin (SO). The concentrations of these additives have great influence on the wear behaviour of Cr2O3 coating, while a little influence on the friction behaviour. Analytical results of XPS show that the wear-reducing action of ZDDP and TCP are a result of the formation of tribochemical reaction films on the rubbing surfaces, a slight wear-increasing action of SO is due to no tribochemical reaction between Cr2O3 coating and SO or its decomposed products.
CYCLIC BONDING STRENGTH FOR HARD COATINGS AND THE EFFECT OF RESIDUAL STRESSES
1993, 7(1).
[Abstract](2159) [PDF 232KB](116)
Abstract:
Bonding strength of hard coatings suggested to be evaluated by cyclic loading. On the basis of contact stress calculation the proper testing parameters were selected in order to determine the initiation of factigue crack in the interface region. A predict area of debonding patch was defined as the initiation point for contact factigue failure and symbolized as σc. Different surface treatments and different coating thicknesses have been processed on the substrates for PVD and PCVD TiN coatings to strengthen or to weaken the bonding strengths between the films and the substrates to as to testify the significance of cyclic bonding strength and compare σc with Lc by scratch tests. The experimental data show that the cyclic bonding strengths tested under normal press with sliding agree well with the experience in the manulacturing. However, the critical coading values by scratch tests Lc do not reflect the results of different states perfectly. In this paper, a new fatigue crack initiation criterion is suggested when residual stress is involdved. It is theoritically found that the optimised residual stress is compressive with the magnitude of 0.2 Gpa and at the present experimental parameters, this confirms with the experimental results that the decrease of residual stress can improve the cyclic bonding strength for PVD TiN which holds originally 4~7 Gpa compressive stress.
A TEHD ANALYSIS OF A DISC-SUPPORED, DOUBLE-LAYER, POINT-PIVOTED, THRUST BEARING OF A HYDRAULIC GENERATOR
1993, 7(1).
[Abstract](2131) [PDF 243KB](120)
Abstract:
A disc-supported, double-layer, point-pivoted, thrust bearing is analyzed by means of the thermoelastohydrodynamic theory. The pressure, as well as the three-dimensional heat conduction and the three-dimensional thermoelasticity are calculated with the boundary element method. An iteration scheme to accelerate the convergent process of the pressure centre is developed. The effects of load, velocity, insulator ect.on the behaviour of the bearing are investigated.