The removal of material in the ductile regime while improving machining efficiency is currently the technical bottleneck in grinding zirconia ceramics. Prediction models of minimum chip thickness (
h
...min
) and ductile–brittle transition chip thickness (
h
d–b
) were developed according to grinding mechanism. Results showed that both
h
min
and
h
d–b
decreased with increasing friction coefficient. Grinding experiments were carried out using the maximum undeformed chip thickness as the input parameter. Experimental results showed that the
h
min
value in dry grinding is 0.24 μm. Meanwhile, the
h
min
values under minimum quantity lubrication (MQL) and nanoparticle jet MQL (0.4, 0.8, 1.2, 1.6, and 2 vol.%) are 0.27, 0.34, 0.49, 0.65, 0.76, and 0.91 μm, respectively. Furthermore, the
h
d–b
value in dry grinding is 0.8 μm, and the
h
d–b
values under lubrication condition that corresponds to
h
min
are 1.79, 1.98, 2.15, 2.27, 2.39, and 2.59 μm, respectively. The experimental results show the same trend as that of the prediction model. The theoretical calculation is basically consistent with the measured values, with model errors of 7.9% and 6.3%, thereby verifying the accuracy of the chip thickness models.
Aluminum alloy is the main structural material of aircraft, launch vehicle, spaceship, and space station and is processed by milling. However, tool wear and vibration are the bottlenecks in the ...milling process of aviation aluminum alloy. The machining accuracy and surface quality of aluminum alloy milling depend on the cutting parameters, material mechanical properties, machine tools, and other parameters. In particular, milling force is the crucial factor to determine material removal and workpiece surface integrity. However, establishing the prediction model of milling force is important and difficult because milling force is the result of multiparameter coupling of process system. The research progress of cutting force model is reviewed from three modeling methods: empirical model, finite element simulation, and instantaneous milling force model. The problems of cutting force modeling are also determined. In view of these problems, the future work direction is proposed in the following four aspects: (1) high-speed milling is adopted for the thin-walled structure of large aviation with large cutting depth, which easily produces high residual stress. The residual stress should be analyzed under this particular condition. (2) Multiple factors (e.g., eccentric swing milling parameters, lubrication conditions, tools, tool and workpiece deformation, and size effect) should be considered comprehensively when modeling instantaneous milling forces, especially for micro milling and complex surface machining. (3) The database of milling force model, including the corresponding workpiece materials, working condition, cutting tools (geometric figures and coatings), and other parameters, should be established. (4) The effect of chatter on the prediction accuracy of milling force cannot be ignored in thin-walled workpiece milling. (5) The cutting force of aviation aluminum alloy milling under the condition of minimum quantity lubrication (mql) and nanofluid mql should be predicted.
Extreme pressure (EP) and antiwear (AW) additives are necessary for boundary lubrication. However, their mechanisms and physical and chemical properties remain unclear. EP and AW additives were ...reviewed to fill gaps in theoretical and industrial applications. Compounds containing chlorine, sulfur, and phosphorus elements were first used in boundary lubrication because of thermal reaction with metal to form film characteristics. First, the mechanisms of traditional EP and AW additives were analyzed, the physical and chemical properties were compared, and properties affecting factors were studied. Traditional EP and AW additives are not environmentally friendly, but nanoparticle EP and AW additives are excellent substitutes. The mechanisms of nanoparticle EP and AW additives were summarized. The influence of nanoparticle structure parameters, concentration, and media polarity on properties was studied. Second, the influence law of non-polar chain length on traditional EP and AW additives was revealed. The improvement interval of traditional EP and AW additives on the performance of the base fluid was determined. The structural advantage of low crystallinity onion-like and multilayer sheet-like low wrinkle effect of nanoparticles was explained. The particle size design principle attached to the surface roughness and size-dependent melting inhibition mechanism was established. The influence of concentration and media polarity on nanoparticle properties was obtained. Finally, the research of minimum amount matching database and mathematical selection model for traditional EP and AW additives and the molecular dynamics analysis of surface-modified nanoparticles and the development of green general-purpose additives based on molecular design are prospected.
Cutting fluid has cooling and lubricating properties and is an important part of the field of metal machining. Owing to harmful additives, base oils with poor biodegradability, defects in processing ...methods, and unreasonable emissions of waste cutting fluids, cutting fluids have serious pollution problems, which pose challenges to global carbon emissions laws and regulations. However, the current research on cutting fluid and its circulating purification technique lacks systematic review papers to provide scientific technical guidance for actual production. In this study, the key scientific issues in the research achievements of eco-friendly cutting fluid and waste fluid treatment are clarified. First, the preparation and mechanism of organic additives are summarized, and the influence of the physical and chemical properties of vegetable base oils on lubricating properties is analyzed. Then, the process characteristics of cutting fluid reduction supply methods are systematically evaluated. Second, the treatment of oil mist and miscellaneous oil, the removal mechanism and approach of microorganisms, and the design principles of integrated recycling equipment are outlined. The conclusion is concluded that the synergistic effect of organic additives, biodegradable vegetable base oils and recycling purification effectively reduces the environmental pollution of cutting fluids. Finally, in view of the limitations of the cutting fluid and its circulating purification technique, the prospects of amino acid additive development, self-adapting jet parameter supply system, matching mechanism between processing conditions and cutting fluid are put forward, which provides the basis and support for the engineering application and development of cutting fluid and its circulating purification.
The centrifugal compressor impeller is widely used in petroleum, chemicals, and other fields and is liable to failure in complicated working environment. Laser cladding as an advanced technology was ...used to remanufacture the failure impeller. And, remanufacture quality and service safety should be considered. In this paper, simulation and experiments were applied to study the remanufacturing process of failure thin-wall impeller blade. Firstly, a sequentially uncoupled 3D thermo-mechanical finite element (FE) model was developed to calculate temperature distribution and conduct mechanical analysis. Secondly, the impeller blade of repair region quality was studied based on microstructure analysis, microhardness, and tensile property tests. Finally, dynamic-balancing experiment, over-speed test, and dye penetration inspection were used to assess the security of remanufactured impeller. Numerical simulation showed that high temperature (about 1521 °C) and high residual stress (about 300 MPa) were distributed surrounding heat-affected zone (HAZ). And, experiments showed that the deformation of remanufactured impeller was 1.5 mm without no pores, cracks, slag inclusion, and other defects occurred in the remanufactured region.
In nanofluid minimum quantity lubrication (NMQL) grinding of titanium (Ti) alloy, existing nanoparticles cannot solve the technical bottleneck of high surface integrity. Therefore, graphene (GR) ...nanoparticles, which have excellent lubrication performance, were applied in NMQL. The tribological properties of GR nanofluid on wheel–workpiece interface were studied by friction and wear test. In the experiment, 0.5–3 nm thick GR nanoparticles were used to prepare 3% vol. palm oil-based nanofluid. Ball-disc experiment under grinding conditions was carried out on the friction and wear tester. Grinding balls with SiC abrasive grains (to simulate the grinding wheel) and Ti-6Al-4V disc (to simulate the workpiece) were used. Load force was set for simulation of pressure boundary condition of the grinding wheel–workpiece interface. Stratiform nanoparticles (MoS
2
, MoO
3
, and HBN) were used as the comparison group. Results demonstrated that GR nanofluid achieved smaller friction coefficient (0.295), error bars (0.0029), and area of scratches (182,940 μm
2
). GR nanoparticles with small gravity and large specific surface area improved the viscosity of nanofluid and consequently the lubrication performance. The plane hexagonal honeycomb structure determines the strong lubrication stability and abrasive resistance of the GR nanoparticles. The scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) images of the scratch surface also verified the above conclusions.
Water-based cutting fluid has a broad application area and a hundred year history, but its poor corrosion inhibition and anti-rust ability limit its further promotion. Adding corrosion inhibitors can ...effectively solve the above problems. However, no review papers are available on cutting fluid corrosion inhibitors, and their mechanism, suitability, and performance influencing factors have not been revealed. This article discusses cutting fluid corrosion inhibitors to fill the gaps in theoretical research and industrial applications. Inorganic matters are initially used in corrosion inhibition due to their strong oxidizing properties. Therefore, the film formation mechanism of inorganic corrosion inhibitor oxide and precipitation film is first analyzed, and the applications in corrosive medium are summarized. Given that inorganic corrosion inhibitors are not environmentally friendly and expensive, organic corrosion inhibitors are currently used as replacement. Thus, the film formation mechanism of different organic corrosion inhibitors adsorption film is analyzed, and their suitability with metals is determined. The influence of molecular structure and temperature on their corrosion inhibition effect is also studied, and the performance of inorganic and organic corrosion inhibitors is compared. However, single organic corrosion inhibitors are greatly affected by metal surface state, temperature, and immersion time. Therefore, the synergistic film formation after the compounding of organic and inorganic corrosion inhibitors is analyzed. In addition, the influence rate of concentration, molecular structure, and temperature on corrosion inhibition performance is revealed, and a matching database of corrosion inhibitor type and metal type in cutting is established. Finally, in view of the limitations of cutting fluid corrosion inhibitors, the establishment of a molecular dynamics model of corrosion inhibitor failure and accelerates corrosion and the development of general-purpose green additives based on the molecular design and physical and chemical analysis of the suitability of corrosion inhibitor and base liquid are prospected.
The application of cutting fluid in the field of engineering manufacturing has a history of hundreds of years, and it plays a vital role in the processing efficiency and surface quality of parts. ...Among them, water-based cutting fluid accounts for more than 90% of the consumption of cutting fluid. However, long-term recycling of water-based cutting fluid could easily cause deterioration, and the breeding of bacteria could cause the cutting fluid to fail, increase manufacturing costs, and even endanger the health of workers. Traditional bactericides could improve the biological stability of cutting fluids, but they are toxic to the environment and do not conform to the development trend of low-carbon manufacturing. Low-carbon manufacturing is inevitable and the direction of sustainable manufacturing. The use of nanomaterials, transition metal complexes, and physical sterilization methods on the bacterial cell membrane and genetic material could effectively solve this problem. In this article, the mechanism of action of additives and microbial metabolites was first analyzed. Then, the denaturation mechanism of traditional bactericides on the target protein and the effect of sterilization efficiency were summarized. Further, the mechanism of nanomaterials disrupting cell membrane potential was discussed. The effects of lipophilicity and the atomic number of transition metal complexes on cell membrane penetration were also summarized, and the effects of ultraviolet rays and ozone on the destruction of bacterial genetic material were reviewed. In other words, the bactericidal performance, hazard, degradability, and economics of various sterilization methods were comprehensively evaluated, and the potential development direction of improving the biological stability of cutting fluid was proposed.
Magnesium alloys are widely used in industrial fields with excellent comprehensive properties. At the same time, as the lightest structural metal, magnesium alloys are expected to replace aluminum ...alloys and steels to achieve significant weight reduction in aircraft and automobiles. However, the current mainstream magnesium alloy processing methods usually possess the limitations of complex process flow, low material utilization and high manufacturing cost, which limit the wide application of magnesium alloys. With the advantages of high deposition rate and high process flexibility, wire-arc directed energy deposition (DED) process is promising for the fabrication of large and complex magnesium alloy components to improve manufacturing efficiency and increase material utilization. Due to the uniqueness of wire-arc DED, magnesium alloys deposited by this process have different microstructure and properties from other techniques. Therefore, this paper systematically reviews the forming characteristics of wire-arc DED magnesium alloys, summarizes the current status of research on microstructure, properties and defects in this field and presents some feasible quality optimization strategies. On this basis, the limitations of the current research are concluded and comments are provided for subsequent research. Current research has shown that wire-arc DED has the capability to deposit full equiaxed grains magnesium alloys. The future research should be focus on the development of new magnesium alloy wires, the regulation of macro morphology, microstructure and properties, the combination of auxiliary processes and the suppression of defects, in order to further improve the properties of magnesium alloy components and broaden the way for their application.
As a new generation of manufacturing technology, laser welding is widely applied in the fields of automobile, aerospace, etc. with its compelling advantages of high flexibility, quality, and energy ...density. However, the environmental performance of the laser welding process is not clear so far. There is a lack of systematic analysis of the laser welding process that takes all the energy sources and material consumption into consideration to reflect the actual environmental impact and evaluate the process parameter for decision-making. In this study, a parameterized model linking the carbon emissions and laser welding parameters is established. Based on this, a carbon efficiency evaluation approach is proposed to reveal the trade-off between carbon emissions and the added manufacturing value for decision-making on the premise of ensuring the welding quality. To verify the effectiveness of this approach, the carbon efficiency of the laser butt joint welding process is analyzed as an illustration. The results show that the parametric carbon emission models offer a feasible evaluation of carbon emissions of the laser welding process, with an accuracy of approximately 93.6%. The carbon emissions of the cooling system are 1.78 times that of laser devices. Thus, it dominates the carbon emissions of the laser welding process rather than laser devices. While ensuring the processing quality, increasing the welding speed is the most key way to improve carbon efficiency. The reason for it is that the carbon emissions of auxiliary facilities, e.g., cooling system can be reduced significantly as the reduced welding time. Furthermore, the standby time used, e.g., clamping and taking-off of workpieces, etc., is another key factor affecting the carbon efficiency. Thus, shortening the standby time can also improve the carbon efficiency of the laser welding process.
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