Efficacy of surface microtexturing in enhancing the tribological performance of polymeric surfaces under starved lubricated conditions
Introduction
Surface texturing has been successfully utilized to enhance the performance of different components in various applications [1]. Cutting tools are among industrial applications which benefitted from surface texturing [[2], [3], [4]]. The focus of the present study is on the application of surface texturing to improve the tribological performance of parallel sliding contacts, such as thrust bearings [5,6]. To describe the experimental conditions of the tests conducted in the present study, it is essential to differentiate between lubrication regime and lubrication condition of the tests. To clarify, there are studies that interchangeably use the terms mixed and starved to describe a lubrication regime/condition [[7], [8], [9]]. Other studies attempted to define starved lubrication [9], or impose certain constraints, such as limited supply of the lubricant on the contact to describe starved lubrication [10]. In this work, we assign specific definitions for each term.
Supply rate of the lubricant to the contact could be categorized into three readily distinguishable conditions namely dry, starved, and fully-flooded or submerged conditions. When the lubricant is provided at a limited supply rate in the form of spraying, capillary effect, or other minimal supply rate, the term starved condition could be appropriately used. Every lubrication regime could transpire at each of these lubrication supply rates from hydrodynamic regime at a dry contact which is prevalent in air bearings [11,12] to the mixed or even hydrodynamic regime under starved conditions [[13], [14], [15]]. There are several studies [[16], [17], [18], [19], [20], [21]] which have embraced this terminology that seems crucial for more accurate description of a contact lubrication history.
Implementing parametric studies using sliding velocity and obtaining its effect on the COF as a tool for detecting lubrication regimes have been used by many authors [14,15,22,23]. The present study utilizes COF changes with velocity as an indicator of the lubrication regime.
One could expect a shift in the Stribeck curve towards the boundary regime for a textured surface because of lower bearing area, thus higher contact pressure. A leveling effect in the COF behavior in the Stribeck curve was mentioned to signify the optimum texturing parameters [24]. The effect of texturing area density and the side of the tribocontact which is textured, whether the polymer side or the metallic side, was studied for UHMWPE-stainless steel tribopairs. Constant reduction of the COF with increasing velocity for water-lubricated textured UHWMPE was observed for a contact pressure of 0.32 MPa [20], and an optimum area density of 30% was suggested. The effect of elastic modulus on the tribological performance of textured surfaces was discussed in other studies [20,25]. Pressurizing the cavities is essential for generating higher lifts. However excessive pressurizing could damage the structural integrity of the texturing if the mechanical properties such as yield strength are not integrated into the texturing design carefully. Numerical studies focus on the role of texture spatial distribution [26], and texture shapes [27] for journal bearings, and suggested enhanced load capacity via partial texturing, compared to full texturing in the hydrodynamic regime. Other studies show the effective reduction of slip-stick behavior through texturing under starved lubrication conditions [28]. Recent review papers highlight the key role of texturing in enhancing tribological performance of piston-ring and seals [29], as well as machining processes [30] in starved and flooded conditions. In addition, significant improvement in anti-scuffing performance of textured surfaces [31], as well as implementing texturing to reduce adhesive wear [32] under starved lubrication conditions were shown.
Concentration of stress along the perimeter of the textures, usually around sharp corners of the texture features, has been shown numerically [20,33,34]. The negative effect of such stress concentration on friction and wear of textured surfaces were discussed [35] and its elimination is one of the criteria implemented in texture optimization [36]. Hence, the significance of the dimple shapes. Recent studies under starved lubrication on the influence of dimple shape on tribofilm formation, revealed that the tribofilm could outweigh the texturing tribological effects [37]. In this work we also study the effect of plastic deformation of the dimples on effective wear and friction reduction.
Trapping of wear debris by microtextures such as microdimples, retaining lubricant as microreservoirs for liquid lubricants, and generating microhydrodynamic lift were identified as key mechanisms which contribute to enhanced tribological performance of textured surfaces [7,38,39]. Understanding the effect of geometrical specifications of the texturing, such as area density of the dimples, on changes in wear and friction of the sliding components has been studied [38,[40], [41], [42]]. The texture distribution was found to have a strong influence on the wear characteristics of a textured surface [41], while the area density was identified as the most influential parameter on the load carrying capacity, and friction behavior for polymers. The efficiency of texturing also depends on the operating conditions of a bearing contact [43].
The present study investigates the efficacy of textured surfaces under starved lubrication conditions and compares their performance with plain (untextured) surfaces. The focus of this work is on the role of sliding velocity, normal load, polymer material, and type of contact, i.e., kinetic or static. The main objective is to obtain further insight to the texturing of polymers under starved lubrication, which directly contributes to better engineering design and optimization of systems operating under such conditions.
Section snippets
Materials and fabrication of microtextures on polymers
ATSP is an advanced polymer with excellent wear performance under different tribological conditions, including high temperature, starved and dry, high pressure, high speed and abrasive conditions [[44], [45], [46], [47], [48]]. UHMWPE has shown promising performance in various tribological applications, including textured surfaces for bio implants as well as industrial applications [20,24,49,50]. The mechanical properties of ATSP and UHMWPE are given in Table 1. For the pin-on-disk experiments,
Effect of sliding velocity on textured ATSP
The COF values for both untextured and textured ATSP surfaces were obtained under 5.02 MPa nominal contact pressure at a wide range of sliding velocities. Fig. 3 (a) depicts typical data obtained for a single run conducted on the ATSP textured pin under 5.02 MPa contact pressure. The run-in period followed by the incrementally decreasing velocity section is shown. The experiment is concluded by a final reciprocating motion to obtain the static COF. Fig. 3 (b) depicts the obtained average static
Conclusion
Static and kinetic COFs of two different polymers, namely ATSP and UHMWPE were measured under starved lubricated conditions. The effects of texturing, sliding speed and contact pressure were investigated. The evolution of surface topography as a result of harsh testing conditions was investigated and the wear mechanisms were analyzed. In summary, the main findings are:
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Under starved lubricated conditions with a high viscosity lubricant, the efficiency of texturing is most pronounced in the mixed
CRediT authorship contribution statement
Reza Gheisari: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Validation, Visualization, Writing - original draft, Writing - review & editing. Pixiang Lan: Conceptualization, Methodology, Visualization, Writing - original draft, Writing - review & editing. Andreas A. Polycarpou: Conceptualization, Data curation, Funding acquisition, Project administration, Resources, Software, Supervision, Writing - original draft, Writing - review & editing.
Acknowledgement
Partial funding of the present study was provided from the Meinhard H. Kotzebue ‘14 endowment in the J. Mike Walker ‘66 Department of Mechanical Engineering at Texas A&M University. The authors also acknowledge the use of the Texas A&M Materials Characterization Facility (MCF).
References (71)
- et al.
Tribological aspects of various geometrically shaped micro-textures on cutting insert to improve tool life in hard turning process
J. Manuf. Process.
(2018) - et al.
Performance of electrical discharge textured cutting tools
CIRP Ann.
(2011) - et al.
Development of cutting tools with microscale and nanoscale textures to improve frictional behavior
Precis. Eng.
(2009) - et al.
Effect of textured area on the performances of a hydrodynamic journal bearing
Tribol. Int.
(2011) - et al.
Tribological studies of unpolished laser surface textures under starved lubrication conditions for use in air-conditioning and refrigeration compressors
Tribol. Int.
(2011) - et al.
Effects of surface texturing on ring/liner friction under starved lubrication
Tribol. Int.
(2016) - et al.
Effect of surface texturing on cast iron reciprocating against steel under starved lubrication conditions: a parametric study
Wear
(2016) - et al.
Hydrodynamic lubrication of textured steel surfaces under reciprocating sliding conditions
Tribol. Int.
(2007) - et al.
Tribological properties of Tin-based Babbitt bearing alloy with polyurethane coating under dry and starved lubrication conditions
Tribol. Int.
(2015) - et al.
Comparison of the effects of surface texture on the surfaces of steel and UHMWPE
Tribol. Int.
(2013)
Investigation of porous polyimide lubricant retainers to improve the performance of rolling bearings under conditions of starved lubrication
Wear
A critical assessment of surface texturing for friction and wear improvement
Wear
Tribological effects of surface texturing on nitriding steel for high-performance engine applications
Wear
The effect of surface texturing in soft elasto-hydrodynamic lubrication
Tribol. Int.
Effect of textured area on the performances of a hydrodynamic journal bearing
Tribol. Int.
Effect of surface texturing on tribological performance of sliding guideway under boundary lubrication
J. Manuf. Process.
Role of textured tool in improving machining performance: a review
J. Manuf. Process.
Influence of sheet metal texture on the adhesive wear and friction behaviour of EN AW-5083 aluminum under dry and starved lubrication
Tribol. Int.
Influence of dimple shape on tribofilm formation and tribological properties of textured surfaces under full and starved lubrication
Tribol. Int.
Fabrication of textured composite surface and its tribological properties under starved lubrication and dry sliding conditions
Surf. Coat. Technol.
The effect of surface texturing on reducing the friction and wear of steel under lubricated sliding contact
Appl. Surf. Sci.
An optimization research on the coverage of micro-textures arranged on bearing sliders
Tribol. Int.
Hydrodynamic lubrication of textured surfaces: a review of modeling techniques and key findings
Tribol. Int.
High temperature and high pressure tribological experiments of advanced polymeric coatings in the presence of drilling mud for oil & gas applications
Tribol. Int.
Advanced polymeric coatings for tilting pad bearings with application in the oil and gas industry
Wear
Tribological performance of aromatic thermosetting polyester (ATSP) coatings under cryogenic conditions
Wear
Tribology review of blended bulk polymers and their coatings for high-load bearing applications
Tribol. Int.
The effect of surface topography of retrieved femoral heads on the wear of UHMWPE sockets
Med. Eng. Phys.
A phenomenological elevated temperature friction model for viscoelastic polymer coatings based on nanoindentation
Tribol. Int.
Friction characteristics of microtextured surfaces under mixed and hydrodynamic lubrication
Tribol. Int.
Detailed surface roughness characterization of engineering surfaces undergoing tribological testing leading to scuffing
Wear
Surface topography characterisation
Fundam. Princ. Eng.
Three-body abrasive wear of hard coatings: effects of hardness and roughness
Thin Solid Films
Mechanical characterization of polymeric films using depth-sensing instrument: correlation between viscoelastic-plastic properties and scratch resistance
Prog. Org. Coat.
Mechanical and tribological performance of UHMWPE influenced by temperature change
Polym. Test.
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