Rolling/Sliding Wear Behavior of High Carbon Steel Wire Rod (HSWR) of Traction Machine

Steel wires are critical load-bearing components in a wide range of applications such as elevator, cranes, mine haulage etc. The traction machine of elevator which transmits power to wire rope causes micro-slip between wire rope and sheave during reciprocating action. The lubrication condition of wire rope is also changed due to the lack of grease. This study focuses on the wear behavior of steel wire and effect of both dry and grease conditions by using the rolling/sliding contact wear tester done under various slip ratios and rolling speeds. The experimental results of the wear volume curve against the number of revolutions under the grease condition are compared with the results under dry condition. The worn surface of steel wire and the size of wear particles were observed by SEM. In order to quantify the wear amount of steel wire we established an equation and finally obtained the wear coefficient.

Scale Effects in Generalized Newtonian Elastohydrodynamic Films

The prediction of elastohydrodynamic lubrication (EHL) film thickness requires knowledge of the lubricant properties. Today, in many instances, the properties have been obtained from a measurement of the central film thickness in an optical EHL point contact simulator and the assumption of a classical Newtonian film thickness formula. This technique has the practical advantage of using an effective pressure-viscosity coefficient which compensates for shear-thinning. We have shown by a perturbation analysis and by a full EHL numerical solution that the practice of extrapolating from a laboratory scale measurement of film thickness to the film thickness of an operating contact within a real machine may substantially overestimate the film thickness in the real machine if the machine scale is smaller and the lubricant is shear-thinning in the inlet zone.

Prototype Design of a High-Speed Viscous Air Spindle

In this paper an innovative air driven spindle for micro cutting applications is presented. The spindle uses a viscous traction concept which has the advantage that the viscous traction forces can act directly on the cylindrical part of the tool, which makes the tool-holder redundant. Furthermore, the tool can be actuated in the axial direction within the housing. In this paper the concept of the viscous turbine, a design of a prototype spindle along with the traction and load-capacity of the spindle are discussed.

Synergistic Antiwear Effects of Zinc Dialkyl Dithiophosphate and Different Detergents

The effectiveness of blends consisting of base oil, some secondary zinc dialkyl dithiophosphate (ZDDP), and different detergents to form antiwear tribofilms on steel surfaces sliding in the boundary lubrication regime was investigated in the temperature range of 105–125°C. The efficacy of the tribofilms formed from these blends was evaluated in terms of contact voltage and wear rate measurements. The best antiwear performance was demonstrated by the tribofilm formed from the blend containing sulphonate detergent. The results of this study provide insight into competing effects between ZDDP and different detergents that affect significantly the antiwear performance of the formed tribofilms.

Influence of Scratches on the Performance of a Partial Journal Bearing

In this paper, the influence of circumferential scratches on the thermohydrodynamic performance of a partial (lobe) journal bearing is studied. The bearing damage is characterized by four factors: the area of the scratched region, the density of the scratches within the affected area, the relative position of the scratched region and the relative depth of the wear defects. The bearing performance is characterized by minimum film thickness, average oil temperature, maximum pressure, friction torque etc., at imposed magnitude and direction of the load. A numerical hydrodynamic model with global thermal effects is used for studying the influence of the different wear related parameters on the bearing performance. The results permit to predict the overall performance loss due to the circumferential wear marks, for different wear profiles. The types of wear profiles that can lead to the bearing destruction (characterized by a critical minimum film thickness) are also investigated.

Characterization of Contact Damping and Frequency in Elastic-Plastic Contact

Elastic-plastic interaction of a block of rough surface with a smooth plane is considered in this paper. The nonlinear normal vibration response of the block is examined when subject to an external compressive load. Free vibration response of the block is studied. The vibration response corresponds to the application of a constant compressive external load and the study yields closed-form equations for the contact damping rate and contact natural frequency. It is shown that vibration decay rate is constant as opposed to the exponential decay rate for the linear vibrating systems. Closed form equations relating contact damping rate and contact natural frequency to the surface parameters are given.

Mechanical Properties of ZDTP Tribofilms Measured by Nanoindentation: Strain Rate and Temperature Effects

This study aims to contribute to better understand the antiwear action of zinc dialkyldithiophosphate (ZDTP) additives used in car engine lubrication. The antiwear action of ZDTP is associated to the formation of a protective tribofilm onto the rubbing surface. On a mechanical point of view, the efficiency of ZDTP tribofilms results from equilibrium between film formation and wear rates, associated with appropriate rheological properties. In this work, the mechanical properties of a ZDTP tribofilm have been measured by nanoindentation in different test conditions in order to investigate the effect of temperature and strain rate. A Nanoindenter XP® entirely set into a climatic chamber was used to perform the nanoindentation tests. For all tests, an increase of the elastic modulus was observed from a threshold contact pressure value. This effect is similar to the anvil effect observed on polymers: in confined geometry, the elastic modulus increases versus hydrostatic pressure. For the tribofilm, in the studied range, this effect is enhanced at high temperature and low strain rate. Furthermore, when the temperature increases, a change in the rheological behavior of the tribofilm is observed. Up to about 50°C, the tribofilm exhibits viscoplastic behavior — the hardness increases versus strain rate — and above 50°C, the hardness decreases versus strain rate (“shear thinning-like” behavior).

Lubricant for Probe-Based Ferroelectric Recording Devices

In a probe-based ferroelectric recording system a protective coating of lubricant provides low friction and a low wear rate as well as allows the continuous contact of the probe tip with the storage medium. SO5, a member of the commercially available electric connector lubricants polyphenyl ether (PPE), was experimentally proven effective as a lubricant in supporting this probe/media interface and has enabled the demonstration of the probe-based ferroelectric recording technology. The unique stability of SO5 lubricant in an electric field and in the presence of electrons makes this liquid particularly suitable for ferroelectric recording storage devices. A broad range of analytical techniques were used to identify this lubricant as a mixture of alkylated diphenyl ethers having varying molecular weight. A thin layer of this lubricant was uniformly coated on the probe media surface through a dip-lubing procedure. Its thermal stability and wettability was investigated in terms of the requirements for the successful application of this unique ferroelectric recording technology. The impact of this lubricant film on the read/write capability, durability and tribological performance was also explored.

A Molecular Model of Asperity Contact and Comparison to Continuum Based Models

Surface asperities can range widely in size. Therefore it is important to characterize the effect of size and scale on the contact mechanics. This work presents a molecular model of asperity contact in order to characterize small scale asperity contact. The model is also compared to existing continuum mechanics based models developed originally by Hertz for elastic contact and later expanded by others to include plasticity. It appears that the predictions can be related to each other and that the continuum material properties can be related to the properties describing the molecular forces.

Sliding Contact of Elastically Dissimilar Periodic Profiles

Various methods for solving the partial contact of surfaces with regularly periodic profiles—which might arise in analyses of asperity level contact, serrated surfaces or even curved structures—have previously been employed for elastic materials. A new approach based upon the summation of evenly spaced Flamant’s solution is used here to solve periodic problems in plane elasticity for sliding contact with Coulomb friction. The advantage is that solutions are derived in a straightforward manner without requiring extensive experience with advanced mathematical theory.