Elastohydrodynamic Lubrication Regime Research Articles

Nonequilibrium molecular dynamics investigation on friction behavior of organic friction modifiers under dynamic load

The evolution of lubricating oil containing additives under dynamic conditions is very significant, since its oil film structure, velocity distribution, and adsorption characteristic have an obvious impact on friction and wear. In this work, a boundary lubrication (BL) and elastohydrodynamic lubrication (EHL) models under sinusoidal load were carried out by nonequilibrium molecular dynamics (NEMD), using iron oxide as the substrate, hexadecane, and stearic acid molecules as lubricants. It was discovered that the friction in the BL regime is positively correlated with the degree of additive’s solidification. The greater the solidification degree of additive layers, the less the interlacing between them, making the relative motion between them easier and reducing compression oscillation within them, thus diminishing friction in the BL regime. The degree of liquefaction of base oil and additive regions, as well as the velocity difference within their interlacing zones, are connected to the friction force in the EHL regime. At high frequencies as well as large amplitudes, the oil film has a very high degree of liquefaction, which facilitates internal shear in it, and there is essentially no relative motion between the base oil and additives, resulting in low friction.

Influence of cashew nut shell liquid on corrosion and tribocorrosion behavior of metallic alloys

Cashew Nut Shell Liquid (CNSL) has been explored in several applications within the sustainability principles and circular economy of agro-industrial product waste. To understand the anticorrosive and lubricant properties of CNSL solutions, a multi-faceted approach, incorporating electrochemical analyses, immersion test, tribological measurements, and tribochemical characterization was carried out for mild steel AISI 1012, stainless steel AISI 420 and Aluminium Alloy 6061. Electrochemical analyses reveal a positive impact of CNSL, inducing a shift in corrosion potential to more positive values and a decrease in corrosion current, indicating effective corrosion inhibition for stainless steel and aluminium alloy. In mild steel, CNSL exhibits a mixed-type inhibition with efficiency increasing in correlation with oil concentration. The lubricating properties of CNSL are evident according to the coefficients of friction (COF) obtained and the elastohydrodynamic lubrication regime observed during tribological tests. Tribochemical tests demonstrate a reduction in wear and an improvement in tribocorrosion behavior under sliding conditions. CNSL emerges as a promising tribocorrosion mitigator, demonstrating multifaceted benefits. The concentration-dependent effects highlight the need for optimization in specific applications, particularly for passive materials. CNSL not only inhibits corrosion through film formation but also provides effective lubrication, reducing friction, wear, and chemical-mechanical degradation. This research contributes valuable insights to corrosion science. It proposes practical applications for CNSL in diverse industrial contexts, showcasing its potential as an environmentally friendly and sustainable solution for tribocorrosion challenges.

Prediction of mechanical efficiency of spur gear pairs based on tribo-dynamics model of multi-tooth meshing

The prediction of load-dependent losses of gear pairs is a topic of constant concern, which depends largely on the modelling of friction coefficient in tooth meshing. Although the current load-sharing based models can handle the friction coefficient in mixed elastohydrodynamic lubrication regimes, dynamics behaviour of each tooth pair or the time variation of direction of normal contact load is not taken into consideration. This study proposes a new method for modelling efficiency of spur gear pairs in transient operating conditions by coupling the multi-tooth meshing model with the friction coefficient model. The friction coefficient is modelled through load-sharing function, and the gear dynamics model is established with regard to alternate meshing of single-double tooth pair and time variation of direction of normal load and mesh stiffness. The model is validated by comparing the calculated results of friction coefficients and load-dependent losses with experimental data in published literatures, showing good agreement. At the end, the efficiency model is applied to two types of gear pairs to investigate the influence of tooth shapes and operating parameters on the load-dependent losses of gear pairs.

Exploring the potential of graphene nanoplatelets as a lubricant additive: Topography evolution and performance under boundary lubrication conditions

This work investigates the friction and wear reduction effects of adding functionalized graphene nanoplatelets (GNPs) to a fully formulated engine oil. Friction tests using a continuous sliding/rolling ball-on-disk tribometer showed that 0.2 wt% GNP oil reduced friction by up to 28% and 11% in the boundary and elastohydrodynamic lubrication regimes, respectively. The disk tested with GNP oil also exhibited lower wear and evidence of carbon tribofilm formation. Raman spectroscopy indicated that the mechanical stresses in the tribological tests altered the graphene morphology. Furthermore, the study evaluated the literature mechanisms for graphene-induced friction and wear reduction, and concluded that the interplay between interlaminar shearing and protective film formation mechanisms was the most plausible explanation for the obtained results.

Influence of 1-Ethyl-3-methylimidazolium Diethylphosphate Ionic Liquid on the Performance of Eu- and Gd-Doped Diamond-like Carbon Coatings

A composite lubricating system that combines solid and liquid lubrication can create a synergistic effect by leveraging the strengths of both types of lubricants. Solid lubrication coatings possess advantageous load-bearing abilities and exhibit low volatility. By adopting this approach, the system retains the merits of solid lubrication while simultaneously harnessing the advantages of liquid lubrication. The unique properties of diamond-like carbon coatings (DLCs) offer the potential to create binding locations for lubricant additives by introducing dopant elements that have a high affinity with additives. In the present work, the combined use of europium-doped diamond-like carbon (Eu-doped DLC) with varying atomic concentrations of the dopant element (1.7 at. % and 2.4 at. %) and gadolinium-doped diamond-like carbon (Gd-doped DLC) with different atomic concentrations of the dopant element (1.7 at. % and 2.3 at. %) was studied alongside a pure DLC coating and the incorporation of an ionic liquid (IL) additive in a tribological block-on-ring system. The focus was on the 1-Ethyl-3-methylimidazolium diethylphosphate ionic liquid with a concentration of 1 wt. % in polyalphaolefin (PAO) 8. Among the investigated pairs, the coefficient of friction (CoF) of 1.7 at. % Eu-doped DLC coupled with the IL was the smallest in boundary, mixed, and elastohydrodynamic lubrication regimes. Quantification of wear was challenging due to minimal and localized wear on the DLC coating surfaces. The decrease in friction within the boundary lubrication regime underscores the promise of mechanical systems that integrate 1.7 atomic percent Europium-doped diamond-like carbon coatings with ionic liquids (IL). This study presents a compelling avenue for future scholarly exploration and research efforts focused on reducing friction and improving the efficiency of moving components, particularly in situations where tribological properties exert a substantial influence

Rolling Traction in Isoviscous-Rigid, Piezoviscous-Rigid and Elasto-Hydrodynamic Lubrication Regimes at Line Contact

Abstract This paper deals with rolling traction in isoviscous-rigid (IVR), piezoviscous-rigid (PVR) and elasto-hydrodynamic lubrication (EHL) regimes at line contact. First, a measuring method of rolling traction using the two-disk machine supported by ball bearings was explained. Then, the rolling traction in the IVR, PVR, and EHL regimes at line contact was measured. The measured results showed that as load P increases, the time average rolling traction FR AVG in the IVR and PVR regimes increases, while that in the EHL regime does not significantly increase. The measured FR AVG were lower than the rolling traction FR TED/CPA under the isothermal condition calculated by using the commercial software TED/CPA. To establish the rolling traction expression, a rolling traction expression under the isothermal condition FR iso was first derived by means of curve fitting the calculated FR TED/CPA. Then, a rolling traction expression (which takes into account the thermal effects of the inlet shear heating) FR thermal was derived by multiplying the thermal correction factor Ct to the expression FR iso. Finally, it was shown that the proposed expression FR thermal is effective for estimating the rolling traction in the IVR, PVR, and EHL regimes at line contact.

Friction study of honey-water in a mimicked soft oral environment

Food oral tribology plays an important role in studying the oral processing behavior of foods. This article explores the lubricity of different mass fractions of honey-water solutions (HWS) combining experimental and simulation study. Friction experiments are performed in simulated soft oral environment, and the complete Stribeck curve is successfully constructed. It is found that as the mass fractions of honey increase, the friction coefficients decrease and the curves move towards higher Vη (speed × viscosity) values. Higher viscosity and wettability enhance the film-forming and entrainment ability of the fluid, while reducing the friction coefficients in the boundary and mixed regimes. However, changes in wettability have little impact on the elastohydrodynamic lubrication regime of pure honey. In addition, a lubrication model is established using finite element method to examine the fluid movement in the lubrication area. The distribution of lubrication film exhibits a horseshoe shape. Influences of the sliding speed, fluid viscosity, and solid viscoelasticity on the distribution of fluid pressure and film thickness are revealed. This study provides guidance for exploring the oral processing behavior of fluid foods and improving the pleasure of eating.

Study on the electric discharge behaviour of a single contact in EV motor bearings

Electric current discharge in motor bearings is becoming more of a concern with the move toward electric vehicles (EV), since it can damage bearing surfaces and potentially cause premature failures. Electric discharge (ED) tests were carried out utilizing a self-improved ball-on-disc instrument under elastohydrodynamic lubrication (EHL) regime to better understand the nature of electric discharge in EV motor bearings. The experiments prove that the discharge behaviour is related to the lubricant film thickness and the discharges appear at the minimum film thickness area. An electric discharge energy model was developed to describe the relationship between working conditions and the energy of a single discharge. The model was qualitatively verified by comparing the predicted ED damages with the ball-on-disc test results.

Viscoelastic Response of Elastohydrodynamically Lubricated Compliant Contacts below Glass-Transition Temperature.

The widespread use of polymers in the high-performance engineering applications brings challenges in the field of liquid lubrication in order to separate the rubbing surfaces by the coherent fluid-film thickness relative to not only the inelastic material response of the polymers. The determination of the mechanical properties by the nanoindentation and the dynamic mechanical analysis represents the key methodology to identify the viscoelastic behavior with respect to the intense frequency and temperature dependance exhibited by polymers. The fluid-film thickness was examined by the optical chromatic interferometry on the rotational tribometer in the ball-on-disc configuration. Based on the experiments performed, first, the complex modulus and the damping factor for the PMMA polymer describing the frequency and temperature dependence were obtained. Afterwards, the central as well as minimum fluid-film thickness were investigated. The results revealed the operation of the compliant circular contact in the transition region very close to the boundary between the Piezoviscous-elastic and Isoviscous-elastic modes of the elastohydrodynamic lubrication regime, and a significant deviation of the fluid-film thickness from the prediction models for both modes in dependence on the inlet temperature.

Tribological roles of MoS2 and PTFE nano oils at the rolling/sliding point contacts: Conventional versus textured contacts

Nanolubricants and surface textures have evidenced the ability to improve the tribo-performances of concentrated contacts. Motivated by this finding as reported in the literature, in the present work, the synergistic uses of laser-created surface textures and nanolubricants have been employed to explore and improve the tribological behaviours of moderately loaded ( PH = 0.5 and 0.8 GPa) point contacts operating mainly in mixed and elastohydrodynamic lubrication regimes. MoS2 and polytetrafluoroethylene (PTFE) nanoparticles based on two nanolubricants were prepared in the laboratory to lubricate the rolling/sliding conventional and textured point contacts. Two sets of contacts (grounded discs versus lapped balls and grounded textured discs versus lapped balls) have been employed to create the geometric configuration of conventional and textured concentrated point contacts. Based on the experimental results found herein, the friction coefficient with the textured contacts reduced by 64% in the presence of MoS2-based nanolubricant as compared to the conventional point contact lubricated with the base oil; however, in the presence of polytetrafluoroethylene-based nanolubricant, this reduction has been recorded by 56%. The textured surface involving a small dimple size yielded better results than the relatively large size. Worn surfaces have been investigated and analysed using optical and scanning electron microscopy/energy dispersive X-ray spectroscopy micro-images. Moreover, certain surface studies using atomic force microscope have also been conducted to understand the surface topography and associated wear mechanisms.

What stress components drive mechanochemistry? A study of ZDDP tribofilm formation.

Zinc dialkyldithiophosphate (ZDDP), the most widely used antiwear additive in engine oils, has been extensively studied over the last few decades to help understand the origin of its effectiveness. Glassy phosphate-based tribofilms, approximately 100 nm thick, are often formed on surfaces sliding in ZDDP-containing oils, which help to prevent or reduce wear. Recent studies reveal that a combination of applied shear and compressive stresses drive mechanochemical reactions that promote tribofilm growth, and that growth is further accelerated by increased temperature. While recent work has shown that compressive stress alone is insufficient to form tribofilms, the individual effects of the shear stress and compressive stress are not fully understood. Here, shear and compressive stresses are studied separately by using different ratios of high-viscosity, high-traction fluids for testing. This allows the areal mean compressive and shear stresses in the fluid when confined at a loaded sliding interface, to be independently controlled while driving tribofilm growth, which is a system we refer to as a stress-controlled mechanochemical reactor. Tribofilms derived from a secondary ZDDP were generated using a tungsten carbide/tungsten carbide ball-on-disk contact in the full elastohydrodynamic lubrication (EHL) regime using a mini-traction machine (MTM), meaning that solid-solid contact is avoided. The MTM was equipped with a spacer layer imaging (SLIM) capability, permitting in situ measurement of the tribofilm thickness during its growth. The well-separated sliding surfaces generated by the high-viscosity fluids confirm that solid-solid contact is not required for tribofilm formation. Under these full fluid film EHL conditions, shear stress and temperature promote tribofilm growth in accordance with stress-augmented thermal activation. In contrast, under constant shear stress and temperature, compressive stress has the opposite effect, inhibiting tribofilm growth. Using the extended Eyring model for shear- and hydrostatic pressure-affected reaction kinetics, an activation energy of 0.54 ± 0.04 eV is found, consistent with prior studies of ZDDPs. The activation volume for shear stress is found to be 0.18 ± 0.06 nm3, while that for the compressive stress component is much smaller, at 0.010 ± 0.004 nm3. This not only confirms prior work supporting that shear stress drives tribofilm growth, but demonstrates and quantifies how compressive stress inhibits growth, consistent with the rate-limiting step in tribofilm growth involving a bond-breaking reaction. Implications of these findings are discussed.

Modeling and Simulation of a Wave Energy Converter: Multibody System Coupled to Fluid-Film Lubrication Model and Thermal Analysis

Sea wave energy is being increasingly regarded as one of the most promising sources of renewable energy. This paper deals with the modeling and simulation of an onshore wave energy converter system designed by UMBRA GROUP SpA. Several topics are addressed. Starting from the multibody modeling strategy, this paper delves more deeply into the mechanical efficiency evaluation of the ball-screw in the elastohydrodynamic lubrication regime, the core of the energy conversion process, as well as the thermal characterization of the power take-off module, based on the lumped-parameter and finite element method models. High values of ball-screw indirect efficiency have been observed, ranging from 73% to 97%; these results appear even more encouraging when compared to the performance of alternative energy-consuming technologies. Thermal analysis, on the other hand, provided a maximum temperature increase of 40 °C, allowing for the aversion of any structural collapse and the realistic identification of the lubrication regime, which turned out to be mostly mixed. Finally, an inverse multibody dynamic analysis is performed, and the most interesting simulation results are collected to prove the effectiveness of the proposed approach.

On the Elastohydrodynamic Film-Forming Properties of Metalworking Fluids and Oil-in-Water Emulsions

Oil-in-water (O/W) emulsions are water-based lubricants and used as fire-resistant hydraulic fluids and metalworking fluids (MWFs) in industry. The (elasto-)hydrodynamic film-forming properties of O/W emulsions have been studied extensively in literature. Typical elastohydrodynamic lubrication (EHL) behaviors are revealed at low rolling speeds followed by a starved EHL regime at elevated speeds. These emulsions are self-prepared and mostly stable only for a limited time ranging from hours to several days. By contrast, the film-forming behavior of water-miscible commercial MWFs (long-term stable O/W emulsions) has rarely been reported. This restricts the understanding of the lubrication status of many tribological interfaces in manufacturing processes, e.g., the chip-tool contact in cutting. In this work, the (elasto-)hydrodynamic film-forming property of two commercial MWFs is investigated by measuring the film thickness on two ball-on-disc test rigs using different optical interferometry techniques. For comparison, two self-prepared simple O/W emulsions with known formulation have also been investigated. Experimental results from the two test rigs agree well and show that the two self-prepared emulsions have typical EHL behaviors as reported in literature. However, for the two commercial MWFs, there is almost no (elasto-)hydrodynamic film-forming ability over the whole range of speeds used in this study. This could be explained by the cleaning and re-emulsification effects of the MWFs. The lubrication mechanism of the two MWFs is mainly boundary lubrication rather than hydrodynamic lubrication.Graphical

Polymer Lubrication: Pressure–Viscosity–Temperature Dependence of Film Thickness for Highly Loaded Compliant Contacts in Elastohydrodynamic Lubrication Regime

Abstract The relevance of the compliant contacts operated in elastohydrodynamic lubrication regime has increased during the last decades. Polymers and elastomers have been preferred because of their low-cost production or their tribological performance in many mechanical and bioengineering applications, where the metals originally dominated. Especially, in high-performance applications, such as polymer gears, the current subject of interest covers the transition between Piezoviscous-elastic and Isoviscous-elastic regimes of elastohydrodynamic lubrication. Here, it is necessary to precisely determine operating conditions and lubricant properties such as rheology whose contribution to film thickness formation may be influenced by attributes of individual lubrication regimes. The high-pressure viscosimeter and the optical tribometer were used, the former to establish the pressure–viscosity–temperature relationship of two reference lubricants, natural Squalane and synthetic tri(2-ethylhexyl) trimellitate, and the latter to determine the central and minimum film thickness in the circular contact between the PMMA disc and the steel ball using the optical chromatic interferometry method. Experimental results of film thickness demonstrated a significant deviation from the soft elastohydrodynamic lubrication (EHL) models, independently of the lubricant used, load, entrainment speed, and temperature because the pressure–viscosity–temperature response of lubricant was not included. Due to this, film thickness data were regressed, and new power coefficients of dimensionless parameter G¯ were derived. Outcomes confirmed the operation of the compliant circular contact in the transition region between the Piezoviscous-elastic and Isoviscous-elastic regimes with the minimum film thickness identified on the side lobes of the horseshoe shape.

Elastohydrodynamic Lubrication of Compliant Circular Contacts near Glass-Transition Temperature

Lubrication of polymer materials nowadays represents a subject of interest in many engineering applications, such as bearings or gears, to utilize them in the areas where conventional metal materials have so far dominated. However, material properties of polymers are strongly dependent on temperature that delimits a lubrication process and leads to manifestations of viscoelastic behavior of polymers. An understanding of mechanisms, which are responsible for formation of film thickness near the glass-transition temperature, is necessary to prevent initialization of failure modes and to increase the durability of polymer engineering components. Optical chromatic interferometry was applied to investigate development of film thickness and changes in contact geometry of compliant circular contacts operated in the elastohydrodynamic lubrication regime (EHL). Film thickness was compared with soft EHL prediction models, differences in contact geometry were assessed and their contribution to film thickness development were evaluated. Qualitatively good agreement of experimental results of central film thickness and soft EHL predictions was observed; however, minimum film thickness shows significant discrepancies. Outcomes and findings confirm the operation of the compliant circular contact in Isoviscous-elastic regime of EHL and the main influence of temperature and load to thermomechanical response of amorphous polymer PMMA.

Tribological Properties of Ti6Al4V Titanium Textured Surfaces Created by Laser: Effect of Dimple Density

The loss of energy due to friction is one of the major problems industries are facing nowadays. Friction and wear between sliding components reduce the mechanical efficiency of machines and have a negative impact on the environment. In recent years, surface texturing has shown tremendous ability to reduce friction and wear. Micro-features generated on surfaces act as a secondary reservoir for lubricants and wear debris receptacles to further reduce abrasion. In addition, surface texturing boosts hydrodynamic pressure, which increases the elasto-hydrodynamic lubrication regime of the Stribeck curve, reducing friction and wear. Amongst all different techniques to texture surfaces, laser texturing is the most popular due to its advantages such as high accuracy, good consistency and celerity as compared to other techniques. This study investigated the effect of laser texturing on the tribological properties of Ti6Al4V in contact with a ceramic ball. The effect of varying the dimple density on friction and wear was studied using a ball-on-flat reciprocating tribometer under lubricated conditions. Results show that friction and wear were reduced for all the textured samples as compared to an untextured sample, with important friction and wear reductions for the samples with the highest dimple densities. For samples with intermediate dimple densities, the friction coefficient stayed low until the dimples wore out from the surface and then increased to a value similar to the friction coefficient of the untextured surface. The dimple wear-out time observed in these specimens was greatly influenced by the dimple density.

Methyltrioctylammonium Octadecanoate as Lubricant Additive to Different Base Oils

This study investigates the use of an ionic liquid obtained from fatty acids (FAIL) as an additive at 2 wt.% in two different base oils: a mineral oil (M1) and a polyol ester (E1). Physicochemical characterization of the base oil–FAIL blends confirmed the miscibility of the FAIL in the base oils. The addition of the FAIL hardly changed the density of the base oils and the viscosity slightly increased at lower temperatures. The tribological performance of the base oils and their blends with the FAIL was determined using three different tests: Stribeck curve determination and tribofilm formation tests, both under sliding/rolling motion, and reciprocating wear tests. The M1 + FAIL blend showed the lowest friction values under the mixed lubrication regime due to its higher viscosity, while the E1 + FAIL showed the lowest friction values under the elastohydrodynamic lubrication regime, which may well have been due to its higher polarity. Only the E1 + FAIL blend outperformed the antiwear behavior of the base oil, probably because it has better chemical affinity (higher polarity) for the metallic surface. SEM images showed that the predominant wear mechanism was adhesive-type with plastic deformation and XPS studies proved that the presence of increasing amounts of organic oxygen on the wear scar caused better antiwear performance when the E1 + FAIL blend was used.

Boundary Slip-Induced Temperature Rise and Film Thickness Reduction Under Sliding/Rolling Contact in Thermal Elastohydrodynamic Lubrication

Abstract Temperature rise and film thickness reduction are the most important factors in elastohydrodynamic lubrication (EHL). In the EHL contact area, interfacial resistances (velocity/thermal slips) induced by the molecular interaction between lubricant and solid become significant due to the large surface/volume ratio. Although the velocity slip has been investigated extensively, less attention has been paid on the thermal slip in the EHL regime. In this study, numerical simulations were conducted by applying three cases of boundary slips to surfaces under sliding/rolling contacts moving in the same direction for the Newtonian thermal EHL. We found that the coupled velocity/thermal slips lead the most significant temperature rise and film thickness reduction among the three cases. The velocity slip results in a lower temperature in the lubricant and solids, whereas the thermal slip causes a temperature rise in the entire contact area in the lubricant as the film thickness decreases simultaneously. Furthermore, the effect of thermal slip on lubrication is more dominant than that of velocity slip, which increases the entrainment velocity or slide–roll ratio.

Highly Swollen Adsorption Layer Formed by Polymeric Friction Modifier Providing Low Friction at Higher Temperature

To reduce friction, especially under high-temperature conditions, an oil-soluble polymeric friction modifier (polymeric FM) with a methacrylate backbone and hydroxyl groups has been developed. It was designed to have high adsorption performance and to increase in size when dissolved in base oil as the temperature is increased. To investigate the temperature dependence of the structural and tribological characteristics of the adsorbed layer formed on a metal surface by the polymeric FM, neutron reflectometry measurements and nano-to-macro tribological tests were conducted. The measurements revealed that the polymeric FM adsorbed efficiently on a Cu surface and formed a 6.0-nm-thick adsorbed layer at 23 °C. This adsorbed layer was highly swollen, and its thickness became about three times larger at 100 °C. Nanoscale friction tests using an atomic force microscope showed that the swollen-state adsorbed polymeric FM layer exhibited low-friction and surface-protection performance at 100 °C. Macroscale friction tests revealed the tribological behaviour of an adsorbed polymeric FM layer in elastohydrodynamic lubrication and mixed lubrication regimes. At higher temperatures, the increase in shear resistance due to the effect of thin-film lubrication was suppressed by the weaker segment–segment interaction, causing the boundary contact of the adsorbed polymeric FM layer to have low frictional properties on both ball and disc surfaces. The low-friction mechanism of the adsorbed polymeric FM layer at higher temperatures was justified by associating the temperature with the layer thickness.

Bending of Soft Micropatterns in Elastohydrodynamic Lubrication Tribology

Soft tribology is increasingly important in the design and engineering of materials used in robotics, haptics, and biomechanics studies. When patterned surfaces are part of a lubricated tribopair that undergoes sliding and compressive deformation, the patterns experience a bending strain that affects the lubrication film thickness and elastohydrodynamic friction. The contribution of bending patterns to soft tribology is not well understood because earlier studies focused on hard tribopairs with effectively flat surfaces. We investigate and model the differences in lubricated friction for poly(dimethyl siloxane) (PDMS) elastomer and PEGDA/alginate double network hydrogel patterns in order to determine the effect of height-to-width aspect ratio and bending angle on the elastohydrodynamic friction. Photoresists of two different viscosities are spin coated onto silicon substrates to fabricate molds with pattern heights ranging from 20 μm to 50 μm. Tribological characterization of the tribopairs in the elastohydrodynamic lubrication regime shows that the patterns generate a friction peak that is independent of aspect ratio for short patterns but displays a “power-law fit” decrease with increasing aspect ratio for taller patterns. Two independent models are used to estimate the theoretical bending and deflection angles for the tribopairs. The decrease in lubricated friction is attributed to taller patterns having large bending angles and a reduced effective surface for fluid load bearing. Results suggest that the bending of micropatterns could be harnessed to engineer lubricated friction in a variety of applications.