•Reviews on various cooling techniques during machining.•Comprehensive review on cutting fluids and cooling technique on turning of hardened steels.•The used of cutting fluid when turning hard steel ...can reduce the heat generated and improve tool life.
In the recent years, there has been increasing interest in hard turning over grinding for machining of hardened steels. There are some issues in the process which should be understood and dealt with such as friction and heat generation at the cutting area that can affect the tool life and surface finish apart from other machining results to achieve successful performance. Researchers have worked upon several aspects related to hard turning and came up with their own recommendations to overcome these problems. They have tried to investigate the effects of tool materials, cutting parameters, different cooling type and cooling technique on different machinability responses like tool life, surface roughness, cutting forces, chip morphology, etc. This paper presents a comprehensive literature review on cutting fluids and cooling technique on turning of hardened steels. Type of tools and cutting parameters used by the researchers have been summarized and presented in this paper as well to give proper attention to the various researcher works.
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•Machinability of Inconel 718 is studied in finish turning conditions using carbide tools.•A mechanistic cutting force model is improved for round inserts.•A new local formulation is ...tested to take tool wear into account.•This original model is validated over a wide range of finishing parameters.•Residual stresses under the machined surface are studied depending on tool wear.
Machining accuracy can be compromised by elastic workpiece deformation and subsurface residual stress introduction during cutting. In order to anticipate the impact of cutting forces and surface integrity evolutions on finished surface and its geometrical errors, it is necessary to better understand the influence of cutting conditions and tool wear. In this study, machinability of Inconel 718 using a round carbide tool in finish turning conditions is assessed. Cutting forces evolution during tool life are analysed and accompanied by advanced investigations of cutting phenomena. An original mechanistic cutting force model is developed, identified and tested. It includes the effect of tool wear over time in its local formulation. This model allows predicting cutting forces evolution along tool pass for a wide range of finishing cutting conditions. Furthermore, a thorough analysis of residual stress profiles at different tool wear levels is led. It features quantitative results for fresh and worn tools. A study on the influence of cutting parameters and tool wear on residual stress profiles in the machining affected zone is highlighted.
Nanofluids are efficient heat transfer media that have been developed over the past 27 years and have been widely used in the electronic microchannel, engine, spacecraft, nuclear, and solar energy ...fields. With the high demand for efficient lubricants in manufacturing, the application of nanofluids in machining has become a hot topic in academia and industry. However, in the context of the huge amount of literature in the past decade, existing review cannot be used as a technical manual for industrial applications. There are many technical difficulties in establishing a mature production system, which hinder the large-scale application of nanofluids in industrial production. The physicochemical mechanism underlying the application of nanofluids in machining remains unclear. This paper is a complete review of the process, device, and mechanism, especially the unique mechanism of nanofluid minimum quantity lubrication under different processing modes. In this paper, the preparation, fluid, thermal, and tribological properties of nanofluids are reviewed. The performance of nanofluids in machining is clarified. Typically, in friction and wear tests, the coefficient of friction of jatropha oil-based alumina nanofluids is reduced by 85% compared with dry conditions. The cutting fluid based on alumina nanoparticles improves the tool life by 177–230% in hard milling. The addition of carbon nanotube nanoparticles increases the convective heat transfer coefficient of normal saline by 145.06%. Furthermore, the innovative equipment used in the supply of nanofluids is reviewed, and the atomization mechanisms under different boundary conditions are analyzed. The technical problem of parameterized controllable supply system is solved. In addition, the performance of nanofluids in turning, milling, and grinding is discussed. The mapping relationship between the nanofluid parameters and the machining performance is clarified. The flow field distribution and lubricant wetting behavior under different tool-workpiece boundaries are investigated. Finally, the application prospects of nanofluids in machining are discussed. This review includes a report on recent progress in academia and industry as well as a roadmap for future development.
► Multilayer TiN coated carbide insert offers higher tool life and better surface finish. ► Chip morphology reveals reduction of cutting temperature in TiN coated insert. ► Reduction of turning ...forces using multilayer coated carbide inserts. ► In TiN coated carbide insert, 2nd order model predicts well for responses. ► Machining cost is significantly reduced using TiN coated carbide inserts.
The present work deals with some machinability studies on flank wear, surface roughness, chip morphology and cutting forces in finish hard turning of AISI 4340 steel using uncoated and multilayer TiN and ZrCN coated carbide inserts at higher cutting speed range. The process has also been justified economically for its effective application in hard turning. Experimental results revealed that multilayer TiN/TiCN/Al2O3/TiN coated insert performed better than uncoated and TiN/TiCN/Al2O3/ZrCN coated carbide insert being steady growth of flank wear and surface roughness. The tool life for TiN and ZrCN coated carbide inserts was found to be approximately 19min and 8min at the extreme cutting conditions tested. Uncoated carbide insert used to cut hardened steel fractured prematurely. Abrasion, chipping and catastrophic failure are the principal wear mechanisms observed during machining. The turning forces (cutting force, thrust force and feed force) are observed to be lower using multilayer coated carbide insert in hard turning compared to uncoated carbide insert. From 1st and 2nd order regression model, 2nd order model explains about 98.3% and 86.3% of the variability of responses (flank wear and surface roughness) in predicting new observations compared to 1st order model and indicates the better fitting of the model with the data for multilayer TiN coated carbide insert. For ZrCN coated carbide insert, 2nd order flank wear model fits well compared to surface roughness model as observed from ANOVA study. The savings in machining costs using multilayer TiN coated insert is 93.4% compared to uncoated carbide and 40% to ZrCN coated carbide inserts respectively in hard machining taking flank wear criteria of 0.3mm. This shows the economical feasibility of utilizing multilayer TiN coated carbide insert in finish hard turning.
Metal cutting fluids have a huge negative impact on human health and environmental ecology, thus posing a serious threat to the sustainable development of the global manufacturing industry. ...Meanwhile, turning processing is an important part of metal material removal processing, and achieving sustainable lubrication is a major problem that needs to be solved urgently. Using vegetable oil to atomize and spray the tool/chip and tool/workpiece interface through the minimum quantity lubrication (MQL) supply system is a feasible way to achieve environmentally friendly turning. Moreover, the preparation of nanofluid by adding nano-reinforced phases to the degradable bio-lubricant can greatly improve the lubricating performance of the micro-droplets. However, conventional research have only focused on individual factors, such as cutting parameters, types of base oil and nanoparticles, and supply parameters. Thus, these studies are unable to provide effective guidance for the turning processing applications related to nanofluid minimum quantity lubrication (NMQL). In order to fill the gaps in the relevant literature, this paper examines the current advanced research on NMQL and explains the experimental phenomenon through the concept of lubrication mechanism. First, the advanced multi-energy field atomization technology and the influence mechanism of the physical and chemical properties of vegetable oil were reviewed. Subsequently, the influence laws governing nanofluid preparation as well as nanoparticle characteristics and concentration were summarized. Furthermore, textured tool and ultrasonic vibration-assisted nanofluid turning are proposed to increase the effective flow rate. Finally, the challenges and future trends of vegetable oil-based NMQL turning processing are proposed.
Energy-efficient machining has become imperative for energy conservation, emission reduction, and cost saving of manufacturing sectors. Optimal machining parameter decision is regarded as an ...effective way to achieve energy efficient turning. For flexible machining, it is of utmost importance to determine the optimal parameters adaptive to various machines, workpieces, and tools. However, very little research has focused on this issue. Hence, this paper undertakes this challenge by integrated meta-reinforcement learning (MRL) of machining parameters to explore the commonalities of optimization models and use the knowledge to respond quickly to new machining tasks. Specifically, the optimization problem is first formulated as a finite Markov decision process (MDP). Then, the continuous parametric optimization is approached with actor-critic (AC) framework. On the basis of the framework, meta-policy training is performed to improve the generalization capacity of the optimizer. The significance of the proposed method is exemplified and elucidated by a case study with a comparative analysis. Note to Practitioners -Here, we consider a real-world application problem of energy-aware machining parameter optimization encountered in flexible turning operations, namely, design of a parametric optimization method that can be generalized to various machining tasks where multiple objectives and constraints varying with the machining configurations. This paper presents a novel meta-reinforcement learning (MRL)-based optimization method to improve the generalization by training optimizer with multiple machining tasks. To the best of our knowledge, this is the first MRL-based method of adaptive parameter decision for energy-efficient flexible machining. It should be highly emphasized that technologists benefit from the reduced decision-making time and the improved energy saving opportunity.
This paper investigates the passive control of chatter instability in turning processes using a vibro-impact nonlinear energy sink (NES). The workpiece is assumed to be rigid and the tool is ...flexible. A dynamical model including a nonlinear cutting law is presented and the stability lobes diagram is obtained. The behavior of the system with the vibro-impact NES is investigated using an asymptotic analysis. A control mechanism by successive beating is revealed, similarly to the strongly modulated response in the case of NES with cubic stiffness. It is shown that such a response regime may be beneficial for chatter mitigation. An original experimental procedure is proposed to verify the sizing of the vibro-impact NES. An experimental setup is developed with a vibro-impact NES embedded on the lathe tool and the results are analyzed and validated.
Non-linear trend detection in Earth observation time series has become a standard method to characterize changes in terrestrial ecosystems. However, results are largely dependent on the quality and ...consistency of the input data, and only few studies have addressed the impact of data artifacts on the interpretation of detected abrupt changes. Here we study non-linear dynamics and turning points (TPs) of temperate grasslands in East Eurasia using two independent state-of-the-art satellite NDVI datasets (CGLS v3 and MODIS C6) and explore the impact of water availability on observed vegetation changes during 2001–2019. By applying the Break For Additive Season and Trend (BFAST01) method, we conducted a classification typology based on vegetation dynamics which was spatially consistent between the datasets for 40.86 % (459,669 km2) of the study area. When considering also the timing of the TPs, 27.09 % of the pixels showed consistent results between datasets, suggesting that careful interpretation was needed for most of the areas of detected vegetation dynamics when applying BFAST to a single dataset. Notably, for these areas showing identical typology we found that interrupted decreases in vegetation productivity were dominant in the transition zone between desert and steppes. Here, a strong link with changes in water availability was found for >80 % of the area, indicating that increasing drought stress had regulated vegetation productivity in recent years. This study shows the necessity of a cautious interpretation of the results when conducting advanced characterization of vegetation response to climate variability, but at the same time also the opportunities of going beyond the use of single dataset in advanced time-series approaches to better understanding dryland vegetation dynamics for improved anthropogenic interventions to combat vegetation productivity decrease.
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•Consistency in change typology derived from NDVI time series was assessed.•The BFAST algorithm was applied for analyzing dryland ecosystems in East Eurasia.•Only 27.09 % of pixels showed robust detection between two state-of-the-art datasets.•A cautious interpretation of advanced change detection algorithms is called for.
This paper reviews the application of conventional and hybrid nano cutting fluids with different additives in various machining processes, namely turning, milling, drilling, and grinding ones. The ...literature states that using nanofluids, as cutting fluids, improves the lubrication and cooling in comparison with conventional cutting liquids, while the level of improvement depends on some parameters. In turning process, for each nanofluid, there is a specific pressure, flow rate, and nanoparticle volume fraction to reach optimum performance. Nanoparticle concentration in the range of 0.25%–0.5% (low and economical concentrations) is the most repetitive for optimal case in most of machining processes. Also, hybrid nanofluids show more positive effects compared with conventional nanofluids and base fluids. According to the reports, important parameters such as cutting temperature, cutting force, tool wear, and surface roughness experience 10%–40% and in some cases 50%–70% positive change after applying nanoparticles in turning processes. On the other hand, for the milling process, the SiO2, MoS2 and graphene nanoparticles are reported as most applied and effective ones in the literature. For the drilling process, the Cu and diamond nanoparticles are the most applied nanoparticles with positive effect. Moreover, the most utilized nanoparticles for grinding process are MoS2, Al2O3 and diamond families. The corresponding challenges in this field are also examined and directions for future research are recommended.
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•Studies conducted about effects of nanofluids on machining parameters are reviewed.•Parameters such as cutting force, surface roughness, tool wear, temperature, tool life, etc. are considered.•Paper is organized based on different machining processes including turning, milling, drilling, and grinding ones.•Comparisons among various nanofluids are performed, and suitable nanofluid for each machining process is introduced.•Corresponding challenges are examined and directions for future research are recommended.
•Wavelet packet transform were applied to vibration signal for roughness monitoring.•Monitoring of roughness using a single sensor without other information sources.•Three diverse wavelet packet ...methods were compared using forty mother wavelets.•The optimal wavelet packets for roughness were found in specific frequency ranges.•Packet feature extraction was analysed to determine the optimum decomposition level.
The wavelet packet transform method decomposes a time signal into several independent time-frequency signals called packets. This enables the temporary location of transient events occurring during the monitoring of the cutting processes, which is advantageous in monitoring condition and fault diagnosis. This paper proposes the monitoring of surface roughness using a single low cost sensor that is easily implemented in numerical control machine tools in order to make on-line decisions on workpiece surface finish quality. Packet feature extraction in vibration signals was applied to correlate the sensor signals to measured surface roughness. For the successful application of the WPT method, mother wavelets, packet decomposition level, and appropriate packet selection methods should be considered, but are poorly understood aspects in the literature. In this novel contribution, forty mother wavelets, optimal decomposition level, and packet reduction methods were analysed, as well as identifying the effective frequency range providing the best packet feature extraction for monitoring surface finish. The results show that mother wavelet biorthogonal 4.4 in decomposition level L3 with the fusion of the orthogonal vibration components (ax+ay+az) were the best option in the vibration signal and surface roughness correlation. The best packets were found in the medium-high frequency DDA (6250–9375Hz) and high frequency ADA (9375–12500Hz) ranges, and the feed acceleration component ay was the primary source of information. The packet reduction methods forfeited packets with relevant features to the signal, leading to poor results for the prediction of surface roughness. WPT is a robust vibration signal processing method for the monitoring of surface roughness using a single sensor without other information sources, satisfactory results were obtained in comparison to other processing methods with a low computational cost.
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