The reach of tribology has expanded in diverse fields and tribology related research activities have seen immense growth during the last decade. This review takes stock of the recent advances in research pertaining to different aspects of tribology within the last 2 to 3 years. Different aspects of tribology that have been reviewed including lubrication, wear and surface engineering, biotribology, high temperature tribology, and computational tribology. This review attempts to highlight recent research and also presents future outlook pertaining to these aspects. It may however be noted that there are limitations of this review. One of the most important of these is that tribology being a highly multidisciplinary field, the research results are widely spread across various disciplines and there can be omissions because of this. Secondly, the topics dealt with in the field of tribology include only some of the salient topics (such as lubrication, wear, surface engineering, biotribology, high temperature tribology, and computational tribology) but there are many more aspects of tribology that have not been covered in this review. Despite these limitations it is hoped that such a review will bring the most recent salient research in focus and will be beneficial for the growing community of tribology researchers.

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A review of recent advances in tribology

Microstructural response and grain refinement mechanism of commercially pure titanium subjected to multiple laser shock peening impacts

Surface texturing has been frequently used for tribological purposes in the last three decades due to its great potential to reduce friction and wear. Although biological systems advocate the use of hierarchical, multi-scale surface textures, most of the published experimental and numerical works have mainly addressed effects induced by single-scale surface textures. Therefore, it can be assumed that the potential of multi-scale surface texturing to further optimize friction and wear is underexplored. The aim of this review article is to shed some light on the current knowledge in the field of multi-scale surface textures applied to tribological systems from an experimental and numerical point of view. Initially, fabrication techniques with their respective advantages and disadvantages regarding the ability to create multi-scale surface textures are summarized. Afterwards, the existing state-of-the-art regarding experimental work performed to explore the potential, as well as the underlying effects of multi-scale textures under dry and lubricated conditions, is presented. Subsequently, numerical approaches to predict the behavior of multi-scale surface texturing under lubricated conditions are elucidated. Finally, the existing knowledge and hypotheses about the underlying driven mechanisms responsible for the improved tribological performance of multi-scale textures are summarized, and future trends in this research direction are emphasized.

https://www.mdpi.com/2075-4442/7/11/95/pdf

Multi-Scale Surface Texturing in Tribology—Current Knowledge and Future Perspectives

SEM/EDS characterization of laser shock peening effect on localized corrosion of Al alloy in a near natural chloride environment

Effects of surface texturing on ring/liner friction under starved lubrication

Laser shock forming (LSF) of commercially pure (CP) titanium foil with different levels of laser energies, namely 675 mJ,1200 mJ,1800 mJ, and 2000 mJ has been investigated. Even the microformability of Ti is poor due to its hexagonal close-packed (HCP) structure, Ti exhibits greatly enhanced microformability during LSF, which can be attributed to two mechanisms: (1) changes in the constitution of materials due to high strain rate (up to 106/s), and (2) inertial effects. Failure of workpiece was observed under laser energy of 2000 mJ, and adiabatic shear bands (ASBs), which leads to crack formation, was proposed to account for this failure. Refined microstructure can be produced in the formed sample after LSF. The refinement mechanisms were identified by TEM observations: (1) the onset of twins, (2) development of DTs (dislocation tangles) in original grains and DCs (dislocation cells) formed by DTs, and (3) evolution of DCs into subgrains and high misoriented grains. In addition to this refinement progress, nanograins formed through breakdown and rotation of the elongated subgrains can also be observed. Mechanical properties including surface hardness and elastic modulus were characterized by nanoindentation, and both increased greatly after LSF. Increased surface hardness indicates improved surface properties of formed samples, and enhanced elastic modulus indicates an increased stiffness of the workpiece, providing an evidence for reduced springback of Ti during LSF. The investigation in this paper is believed to lay a solid foundation for the application of LSF.

Grain refinement progress of pure titanium during laser shock forming (LSF) and mechanical property characterizations with nanoindentation

This paper presents a novel microscale laser dynamic flexible forming (μLDFF) technique on plastic forming of thin metal sheets. This process utilizes flexible rubber material as a soft punch, under the pressure generated by laser-induced shock wave, to act on the thin metal sheet. This novel technique has many new features and the forming mechanism is complex, as well as it takes place in the scale of nanoseconds, which is too short to monitor the deformation behaviors during the process. In order to reduce the experiment times and cost, this paper firstly investigates the feasibility of the process numerically using finite element software ANSYS/LSDYNA, and some key process parameters, such as hardness and thickness of soft punch, thickness of thin metal sheet, aspect ratio of rigid die, as well as laser pulse energy are detailed studied to obtain reasonable parameters. Then a series of experiments based on these reasonable parameters are conducted, and good experimental results are obtained, which verifies the feasibility of the use of simulation to guide the experiment. The results of both numerical simulations and experiments show that the use of combination of soft punch and thin metal sheet can increase the deformation depth in comparison to focusing the beam directly onto thin metal sheet, which is due to the impedance mismatch at the soft punch–thin metal sheet interface.

Chunxing Gu

Papers

Effects of surface texturing on ring/liner friction under starved lubrication

Grain refinement progress of pure titanium during laser shock forming (LSF) and mechanical property characterizations with nanoindentation

Investigation of microscale laser dynamic flexible forming process—simulation and experiments

A thermal mixed lubrication model to study the textured ring/liner conjunction

Mixed lubrication problems in the presence of textures: An efficient solution to the cavitation problem with consideration of roughness effects