Towards optimum additive performance: A numerical study to understand the influence of roughness parameters on the zinc dialkyldithiophosphates tribofilm growth

Wang, Yuechang; Dorgham, Abdel; Liu, Ying; Wang, Chun; Ghanbarzadeh, Ali; Wilson, Mark C. T.; Neville, Anne; Azam, Abdullah

doi:10.1002/ls.1522

Cited by 4 publications

(2 citation statements)

References 61 publications

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“…Surface roughness is essential for modeling most tribology systems [1]. Modeling dry and lubricated contact between rough surfaces is key for understanding many tribological mechanisms, such as friction [2,3], adhesion [4,5], mixed lubrication [6,7], contact stiffness [8,9], and tribochemistry [10]. One fundamental issue of the modeling processes is the realistic representation of the roughness.…”

Section: Introductionmentioning

confidence: 99%

Understanding the Influences of Multiscale Waviness on the Elastohydrodynamic Lubrication Performance, Part I: The Full-Film Condition

Wang

et al. 2022

Lubricants

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Understanding the responses of tribosystems to multiscale roughness is fundamental for the identification of the relevant roughness scales. This work used a point-contact elastohydrodynamic lubrication (EHL) problem as a representative tribosystem and artificially generated waviness with different amplitudes, frequencies, and directions to mimic the multiscale roughness. The amplitudes and frequencies are related to the feature geometry of smooth EHL problems. This work consists of Part I (this paper), focusing on the full-film condition, and Part II, focusing on the partial-film condition. Generated waviness is input to a transient thermal EHL model. The simulation is conducted 1,600 times for different waviness parameters, loads, and speeds. Seven performance parameters are extracted: the minimum film thickness, maximum pressure, central film thickness, central pressure, mean film thickness, coefficient of friction (COF), and maximum temperature rise. The ratios of these parameters with and without waviness are plotted on the frequency–amplitude coordinate plane as contour maps. The influences of the amplitude, frequency, wave direction, load, and speed on the seven performance parameters are analyzed and summarized. The simulated data and plotted contour maps are provided to the readers in the Supplementary Material.

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Section: Introductionmentioning

confidence: 99%

Understanding the Influences of Multiscale Waviness on the Elastohydrodynamic Lubrication Performance, Part I: The Full-Film Condition

Wang

et al. 2022

Lubricants

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“…The kurtosis portrays how much sharp peaks or valleys contribute to the surface profile (see Figure 4C). The skewness-kurtosis plot (Figure 4D) can be used to study the roughness of biological surface topography (Wainwright et al, 2017), thermal-hydraulic performance Liao et al (2020,2021), normal contact stiffness (Belhadjamor et al, 2020) and other processes (Wang Y. et al, 2021;Ba et al, 2021).…”

Section: D Open Surface Wrinkling: Cylindrical Patterns 21 Pure Ancho...mentioning

confidence: 99%

Pattern formation, structure and functionalities of wrinkled liquid crystal surfaces: A soft matter biomimicry platform

Wang

Servio

Rey

2023

Front. Soft. Matter

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This review presents an integrated theoretical and computational characterization and analysis of surface pattern formation in chiral and achiral liquid crystal self-assembly and the mechanical/optical/tribological/tissue engineering surface functionalities that emerge from various wrinkling processes. Strategies to target surface patterns include linear, non-linear, multidirectional and multiscale wrinkling phenomena. The focus of the review is to show the unique surface structure-functionalities that emerge from anisotropic liquid crystal soft matter, eliminating or reducing the need of aggressive solvents, extreme pressure/temperature conditions, erosion and other surface morphing approaches. The surface pattern formation theoretical-modelling- computational results are then connected and validated with actual biological surfaces that are considered solid liquid crystal analogues, such as exocuticles of insects, fish scales, and flowers. A unique feature of the in silico surface pattern formation platform used throughout this review is the generalized liquid crystal shape equation that includes surface anchoring elasticity, membrane elasticity, and stress loads from liquid crystals orientation gradients. Clear characterization of surface shapes, curvatures, roughness, that are behind surface functionalities are introduced and applied to strengthen validation of predictions with actual nature’s surfaces. Wrinkling scaling laws, and the dependence of material properties on morphing mechanisms are elucidated. The predictions capture very well the two-scale wrinkling patterns in tulips, wrinkling gradients that display water sensor capabilities, egg carton shapes in rose petals and their potential for cell alignment, and the ability to create surface roughness with targeted kurtosis and skewness to control and optimize friction and tribological functionalities. The results are summarized in terms of surface geometry (open or closed) mechanisms and phenomena (anchoring, membrane elasticity), material properties (anchoring coefficients, membrane bending modulus, Frank elasticity), wrinkling scales and scaling laws (amplitude, wave-lengths, skewness, kurtosis) and functionalities (optical iridescence, friction, wettability, structural color, curvature-driven cell alignment and differentiation). Taken together, the range of surface geometries and surface functionalities captured by the liquid crystal biomimetic in silico platform provides a foundation for future experimental green manufacturing pathways based on anisotropic soft matter.

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A comparative study for selecting and using simulation methods of Gaussian random surfaces

Wang

Azam

Wilson

et al. 2022

Tribology International

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Towards optimum additive performance: A numerical study to understand the influence of roughness parameters on the zinc dialkyldithiophosphates tribofilm growth

Cited by 4 publications

References 61 publications

Understanding the Influences of Multiscale Waviness on the Elastohydrodynamic Lubrication Performance, Part I: The Full-Film Condition

Understanding the Influences of Multiscale Waviness on the Elastohydrodynamic Lubrication Performance, Part I: The Full-Film Condition

Pattern formation, structure and functionalities of wrinkled liquid crystal surfaces: A soft matter biomimicry platform

A comparative study for selecting and using simulation methods of Gaussian random surfaces

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