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In high-speed sawing, the penetration of cutting fluid is limited due to the narrow kerf and large cutting depth. To improve the machining performance of high-speed sawing and the lubrication and cooling efficiency of cutting fluid, a technology named electrostatic minimum quantity lubrication (EMQL) high-speed sawing with water-based nanofluid as cutting fluids was developed. The adsorption and motion characteristics of droplets on the solid surface under airflow were studied. Furthermore, the machinability of EMQL in high-speed sawing was explored. The results show that the charged droplet's surface tension, static contact angle, and velocity under tangential airflow are lower than those of the uncharged droplet, while the dynamic contact angle hysteresis is higher. This indicates that the adsorbability of charged droplets on solid surface is enhanced. In high-speed sawing processing, the principal sawing force is reduced by 19% when the fluid is charged at − 4 kV. The reason may be that charging reduces the drag force of the droplet and increases the capillary force generated by the deformation of the contact line between the droplet and the solid surface, which enhances the adsorption capacity of the charged droplets on the sawtooth surfaces and improves the lubrication performance of the sawing area. [ABSTRACT FROM AUTHOR]

Substrate damage brings great challenges to the efficient and nondestructive removal of aircraft skin coatings. Variable load erosion tests of unidirectional carbon fiber reinforced plastic along different fiber orientations were carried out. The effects of different fiber orientations on the erosion mechanism of CFRP are discussed separately. The matrix resin is squeezed and accumulated as platelets due to the erosion of the particles, and these platelets are removed due to repeated impacts of subsequent abrasives. The epoxy resin on the top layer of the laminate is penetrated by the particles with increased energy loss, and the fiber breakage is attributed to the direct impact of the particles on the carbon fiber. Fiber fractures are divided into micro-brittle fractures and macro-brittle fractures. Cracks are initiated by the concentrated stress of particle extrusion and propagate between the graphite crystallites, resulting in irregular micro-brittle fracture and fiber failure. Under the condition of macro-brittle fracture, the fiber will be debonded, flexural deformed, and even lost under the concentrated stress of particle extrusion. The purpose of this study is to provide a theoretical reference on the mechanism by which nondestructive and efficient removal of stealth coatings can be achieved on aircraft skins. [ABSTRACT FROM AUTHOR]

A green manufacturing technology named "electrostatic minimum quantity lubrication (EMQL)" with water-based Al2O3 nanoparticle fluids as cutting fluids was developed in order to improve the cutting property and minimize oil mist concentration during the machining process. The capillary penetration mechanism, oil mist concentration, and heat transfer property of Al2O3 fluid EMQL were investigated. The cutting performance of Al2O3 fluid EMQL and traditional minimum quantity lubrication (MQL) was compared. The results showed that EMQL could improve the penetrability and heat transfer capacity of the lubricant effectively. Compared with Al2O3 fluid MQL and oil-based MQL, Al2O3 fluid EMQL reduced oil mist concentration and cutting temperature remarkably and showed similar cutting performances compared with the oil-based MQL. The excellent performance of this water-based Al2O3 fluid EMQL technology was mainly due to that EMQL could promote a further penetration of the charged Al2O3 nanofluid droplets into the cutting region, which thus reduced the friction force, and the tool durability was maintained obviously and finally presented better machining performance. [ABSTRACT FROM AUTHOR]