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The tetrahedral amorphous carbon (ta-C) coatings are deposited on piston rings to improve the tribological property of the piston ring-cylinder liner system of the internal combustion engines. The deposition parameters are optimized by molecular dynamics simulation to reduce the cost of coatings' fabrication. The ta-C coatings with higher sp3 fraction, lower friction coefficient, and superior anti-wear properties are achieved by optimizing the incident energy and substrate temperature of carbon atoms. The second nearest-neighbor modified embedded-atom method potential and Tersoff potential are used to describe the interatomic interactions. The effects of the incident energy of the carbon atoms and substrate temperature on the deposition properties of the ta-C coatings are discussed. The numerical results show that the ta-C coatings with high sp3 fraction, high density, and good interface mixing are obtained, and the deposition properties of the ta-C coatings are improved. [ABSTRACT FROM AUTHOR]

Triggered by the growing needs for photoelectric conversion and optical interconnections, flexible optoelectronics have recently attracted a surge of interest. Flexible hybrid laminates are promising components of these devices owing to their high performance and flexibility. However, the thermomechanical mismatch of heterostructures usually induces interfacial stresses and resultant failures, particularly for multilayer structures with soft polymeric substrates. The interfacial stresses in flexible laminates remain a challenging matter to be understood distinctly. Herein, the interfacial stresses are investigated via a representative case composed of hard and soft hybrid laminate under nonuniform temperature. By introducing nonuniform shear strain in the thickness direction of bond layer, and nonuniform temperature changes of multilayer simultaneously, a novel analytical model is developed to describe the interfacial stresses with considering adjusted interfacial compliances for the bond layer with varying thicknesses. Our analytical expressions are suitable for different interfacial compliances and a trilinear approximation is verified by the finite element method (FEM) for the adhesive layers with different thicknesses, and comparative analyses were carried out with the existing literatures. The characteristics of the shear stresses are quantitatively illustrated under different temperature variations, elastic moduli and geometrical dimensions. Based on above the vital influencing factors, the mitigating strategies for shear stress are proposed to decrease the interfacial damage. By optimizing key parametric designs, the model and analysis of interfacial stresses could be useful for characterizing the interfacial thermal stress of rigid-flexible films, and enhancing the mechanical stability of heterogeneous multilayers. [ABSTRACT FROM AUTHOR]

The tribological performance of internal combustion engines (ICEs) has an important impact on fuel efficiency and power consumption, and the wear of cylinder liner-piston ring (CLPR) system affects the operation reliability. The surface texture of CLPR can significantly improve the tribological performance of ICEs. Aiming at the friction and wear of CLPR, the different textures (dimple, equilateral triangle and square) are generated on the CLPR using laser processing, and the different tests are conducted on the UMT-TriboLab tester. The coefficient of friction, wear topography, surface roughness parameters and profiles are measured. The results show that, compared with the non-textured surface, the dimple texture surface of piston ring or cylinder liner has better tribological performance. If the textures coexist on the cylinder liner and piston ring, the tribological performances are better than single surface texture. Furthermore, the mixed textures can significantly improve the surface lubrication performance and the ability to store abrasive particles, and better surface quality can be obtained at the same operating conditions to enhance the tribological performance. This study can provide guidance for reducing the friction and wear of CLPR system of ICEs, and achieve energy saving and emission reduction of ICEs. [ABSTRACT FROM AUTHOR]