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Possibilities of Dry and Lubricated Friction Modification Enabled by Different Ultrashort Laser-Based Surface Structuring Methods
摘要： In this contribution we report on the possibilities of dry and lubricated friction modification introduced by different laser surface texturing methods. We compare the potential of Laser-Induced Periodic Surface Structures and Laser Beam Interference Ablation on 100Cr6 steel in a linear reciprocating ball-on-disc configuration using 100Cr6 steel and tungsten carbide balls with load forces between 50 mN and 1000 mN. For dry friction, we find a possibility to reduce the coefficient of friction and we observe a pronounced direction dependency for surfaces fabricated by Laser Beam Interference Ablation. Furthermore, Laser-Induced Periodic Surface Structures result in a load-dependent friction reduction for lubricated linear reciprocating movements. This work helps to identify the modification behaviour of laser generated micro structures with feature sizes of approximately 1 μm and reveals new possibilities for surface engineering
关键词： lubricated friction,smart surfaces,laser surface texturing,laser beam interference ablation,laser-induced periodic surface structures,dry friction
更新于2025-11-21 11:18:25
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Skin friction measurements on structured surfaces using Clauser-chart method and Oil film interferometry
摘要： Measurements of skin friction have been performed on flat and hexagonal concave surfaces using the conventional Clauser-chart method and the Oil film interferometry. The values of shear stress coefficients measured by the conventional Clauser-chart method on a flat plate were found to be up to 13 % higher from the ones deduced by the Oil film interferometry. The velocity profiles required for the Clauser-chart were obtained by using hot wire anemometry. The analysis of the results suggested that the conventional Clauser-chart method cannot be used to predict shear stresses acting on the hexagonal concave surfaces due to the existence of strong pressure gradients. Oil film interferometry not only provides accurate and direct values of shear stress coefficients but also helps to visualize the flow above the surface.
关键词： Oil film interferometry,skin friction,Clauser-chart
更新于2025-09-23 15:23:52
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Evaluating impact damage to fabric-based personal armor by infrared NDT
摘要： The paper considers the thermo-mechanical mechanism of interaction between the damage agents and armor protection made of polymer fabrics. A simplified mathematical model is proposed to describe the deceleration of a damage agent within an armor fabric due to the dissipation of energy expended on irreversible stretching deformations of fabric fibers, as well as fiber slipping friction and material heating. Woven fabric layers are replaced by solid layers characterized by averaged stiffness and viscosity. A discrete numerical model of a solid material is proposed to reduce a problem with a finite number of degrees of freedom; motion equations are obtained on the basis of the Lagrange equations of the second kind, and for their integration, a stable non-conservative difference scheme is used. The software implementation is based on a functional-object paradigm which allows the modeling of conjugated processes. The parameters of governing equations are identified by using the experimental data. Some illustrative examples of interaction between damage agents and armor barriers with different arrangement of fibers are presented. The proposed model can be used to predict the quality of armor protection with the changing number and location of fibers, as well as to test the armor protection by applying the technique of infrared thermography.
关键词： Armor protection,mathematical model,irreversible deformation,infrared thermography,energy absorption,numerical scheme,composite material,fiber friction
更新于2025-09-23 15:22:29
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Skin Friction Measurements Using Oil Film Interferometry in a 3-D Supersonic Flowfield
摘要： The application of oil film interferometry (OFI) for the measurement of global skin friction on the surface beneath a complex three-dimensional supersonic flow is explored in this study. The flowfield is produced by a fin-generated oblique shock interacting with a compressible turbulent boundary layer. Measurements were obtained by modifying a comprehensive acquisition and processing software, previously developed for two-dimensional, low-speed flows, to measure skin friction distributions underneath such flows. This approach required the local flow direction on the surface, and therefore traditional oil flow visualization was coupled with OFI measurements. A cross-correlation-based algorithm was incorporated to extract flow direction from sequences of oil flow visualization images. Photogrammetry was used with both surface oil flow and OFI to ensure proper spatial overlap for the two measurements. Results from this study demonstrate the capability of the approach in a complex, supersonic flow field that contains regions of both separation and reattachment concomitant with a wide range of skin friction values. The skin friction results show excellent homogeneity, standard deviation of 5.1% of the mean, in the undisturbed boundary layer upstream of the interaction and capture well-resolved high shear gradients in the interaction region. A comparison to legacy data from a similar interaction shows matching trends within the developed flow.
关键词： three-dimensional flow,shock boundary-layer interaction,supersonic flow,oil film interferometry,skin friction
更新于2025-09-23 15:22:29
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Frictional Characteristics of Suspended MoS <sub/>2</sub>
摘要： Molybdenum disulfide (MoS2), a booming layered two-dimensional (2D) nanomaterial, has gain intensive interests for its remarkable physical properties. In this work, the friction characteristics of suspended MoS2 are systematically investigated with atomic force microscopy (AFM). The friction on the suspended MoS2 is much larger than that on the supported MoS2 because of the softening bending rigidity and easier formation of puckering at the AFM tip-MoS2 contact interface, and the difference would increases with the applied load. Similar to the supported MoS2, the friction on the suspended MoS2 also decreases with the increasing layers because of the enhanced bending rigidity. The friction on the suspended MoS2 is relatively insensitive to the shapes of holes below but sensitive to the dimensions. This work can provide beneficial guidance for the diverse design requirements of MoS2-based nanoelectromechanical devices.
关键词： friction,suspended,Molybdenum disulfide,puckering effect,bending rigidity,AFM,atomic force microscopy,MoS2,supported
更新于2025-09-23 15:21:21
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Achieving strong friction lap joints of carbon-fiber reinforced plastic and metals by modifying metal surface structure via laser-processing pretreatment
摘要： Strong dissimilar joints of metals and carbon fiber reinforced plastic (CFRP) are highly demanded for the lightweight design in many fields, which, however, are rather challenging to achieve directly via welding. In this study, 5052 Al alloy and plain carbon steel were first pretreated by a laser-processing method to create rather coarse porous metal surfaces, which were then welded to polyamide 6 based CFRP using friction lap joining. The maximum tensile shear force of the dissimilar joints of CFRP-Al alloy and CFRP-steel achieved 4.9 kN, and 3.9 kN, respectively, and the joint efficiency achieved 78% and 62%, respectively, which were more than three times as those of the CFRP- as-received metal joints. This is the first report on the strengthening of the metal-CFRP friction based joints via the assisting laser treatment technique. The significant improvement of the joint strength could be attributed to a great increase of the mechanical anchors and the chemical bonding area at the metal-CFRP interface.
关键词： Metal,Laser processing,Mechanical interlocking,Dissimilar joining,Friction stir welding,Carbon-fiber reinforced plastic
更新于2025-09-23 15:21:01
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Simultaneous optimization of nanosecond laser ablation and frictional characteristics of tantalum carbide coated graphite substrates
摘要： Tantalum carbide (TaC) is a potential candidate for high temperature applications such as rocket nozzles and thrust petals. Laser surface modi?cation of such transition metal carbides imposes challenges in the selection of laser parameters to achieve controlled microstructure, reduction in porosity, surface roughness and higher wear resistance. The present research focuses on in-vestigating the e?ects of laser ablation parameters such as pulse energy, scanning speed, line spacing and their interactions on surface roughness and CoF of tantalum carbide coated graphite substrates. Regression models were developed to establish a correlation between surface roughness and coe?cient of friction along with laser parameters. The contribution of pulse en-ergy was found to be more signi?cant on CoF, whereas line spacing had a greater in?uence on the surface roughness of the TaC coatings. The optimal condition to obtain minimum surface roughness and CoF was achieved at a higher pulse energy of 250 μJ, lower scanning speed of 100 mm/s and lower line spacing of 10 μm.
关键词： Tantalum carbide,Laser ablation,Friction,Surface roughness
更新于2025-09-23 15:21:01
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The restoration of the friction surfaces by laser cladding
摘要： The paper deals with laser cladding of wear-resistant coatings for restoring friction surfaces. It describes the modes of cladding technological process, and presents the results of wear tests. Wear-resistant coating based on the Ni-Cr-B-Si and alumina system, which exceeds 30HGSA steel by 11.5 times by wear resistance.
关键词： wear-resistant coatings,alumina,friction surfaces,Ni-Cr-B-Si,laser cladding
更新于2025-09-23 15:19:57
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Direct Observation of Crystal Engineering in Perovskite Solar Cells in a Moisture-Free Environment using Conductive Atomic Force Microscopy and Friction Force Microscopy
摘要： The origin of the increased efficiency of perovskite solar cells by control of environmental humidity was investigated using conductive atomic force microscopy (C-AFM) and friction force microscopy (FFM). The perovskite thin films fabricated in a humidity-free environment exhibited better crystallinity and lower number of trap sites than the films fabricated in a high-humidity environment. Through in-depth analysis using C-AFM and FFM, we found that there was locally decrystallized area in the perovskite structure fabricated in a high-humidity environment. By suppressing local decrystallization in a humidity-free environment, the power conversion efficiency (PCE) was increased by about 122%. This was mainly attributed to increase of the current density that elimination of the locally decrystallized area increase the effective active area. From this perspective, mapping local current and friction force using C-AFM and FFM could be new techniques for visualizing the effect of crystal engineering of perovskite solar cells in a humidity-free environment.
关键词： power conversion efficiency,crystallinity,perovskite solar cells,friction force microscopy,conductive atomic force microscopy,humidity
更新于2025-09-23 15:19:57
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Study of the effect of surface laser texture on tribological properties of cemented carbide materials
摘要： Surface texturing has become a potential method to obtain a low friction coefficient under dry/lubricated conditions for different mechanical product surfaces. The mechanism of friction and wear reduction from a micro-texture on the surface of cemented carbide cutting tools was investigated by dry cutting a titanium alloy. Three kinds of micro-textures, namely, line, sinusoidal and rhombic grooves, with different area occupancy rates were produced by a laser on the cemented carbide surface. Experiments and finite element simulation of ABAQUS were used to investigate the tribological characteristics of micro-textured cemented carbide. The results indicated that the line-textured cemented carbide with an area occupancy rate of 10% showed a low friction coefficient of 0.076, which is approximately 34% of the non-textured sample. Few adhesives appeared on the textured surface, while a large number of adhesives were attached to the smooth surface after 30 min of dry friction between the cemented carbide and the titanium alloy balls. Moreover, among the three textures, the line-groove texture has the smallest friction coefficient and a good anti-wear effect. The results show that the existence of a groove texture can effectively reserve the wear debris, reduce the bond wear and weaken the furrow effect.
关键词： titanium alloy,friction and wear,Cemented carbide,machine tool and chip contact zone,surface texture
更新于2025-09-23 15:19:57