Influences of Cutting Speed and Material Mechanical Properties on Chip Deformation and Fracture during High-Speed Cutting of Inconel 718

The paper aims to investigate the influences of material constitutive and fracture parameters in addition to cutting speed on chip formation during high-speed cutting of Inconel 718. Finite element analyses for chip formation are conducted with Johnson–Cook constitutive and fracture models. Meanwhile, experiments of high-speed orthogonal cutting are performed to verify the simulation results with cutting speeds ranging from 50 m/min to 7000 m/min. The research indicates that the chip morphology transforms from serrated to fragmented at the cutting speed of 7000 m/min due to embrittlement of the workpiece material under ultra-high cutting speeds. The parameter of shear localization sensitivity is put forward to describe the influences of material mechanical properties on serrated chip formation. The results demonstrate that the effects of initial yield stress and thermal softening coefficient on chip shear localization are much more remarkable than the other constitutive parameters. For the material fracture parameters, the effects of initial fracture strain and exponential factor of stress state on chip shear localization are more much prominent. This paper provides guidance for controlling chip formation through the adjustment of material mechanical properties and the selection of appropriate cutting parameters

An Empirical Study on the Indirect Impact of Flight Delay on China’s Economy

Due to the influence on the sectors and industries that have strong relationships with the air transportation industry, flight delays have a huge impact on China’s economy. In this study, the input–output method and the Ghosh model were used to analyze the indirect economic impacts of flight delays on China’s economy. We also constructed simultaneous demand-fare equations to estimate the direct output of the air industry as a result of flight delay control. The final results showed that the total indirect impact of flight delays on China was Ұ350.71 billion in 2013, stressing the importance of controlling flight delays. Since delay control not only provides direct benefits to passengers and carriers, but also indirectly contributes to regional economies, the efforts benefit the entire Chinese society. The great investment in flight delay governance should be shared among various producing sectors

Investigation of Cutting Temperature during Turning Inconel 718 with (Ti,Al)N PVD Coated Cemented Carbide Tools

Physical Vapor Deposition (PVD) Ti1−xAlxN coated cemented carbide tools are commonly used to cut difficult-to-machine super alloy of Inconel 718. The Al concentration x of Ti1−xAlxN coating can affect the coating microstructure, mechanical and thermo-physical properties of Ti1−xAlxN coating, which affects the cutting temperature in the machining process. Cutting temperature has great influence on the tool life and the machined surface quality. In this study, the influences of PVD (Ti,Al)N coated cemented carbide tools on the cutting temperature were analyzed. Firstly, the microstructures of PVD Ti0.41Al0.59N and Ti0.55Al0.45N coatings were inspected. The increase of Al concentration x enhanced the crystallinity of PVD Ti1−xAlxN coatings without epitaxy growth of TiAlN crystals. Secondly, the mechanical and thermo-physical properties of PVD Ti0.41Al0.59N and Ti0.55Al0.45N coated tools were analyzed. The pinning effects of coating increased with the increasing of Al concentration x, which can decrease the friction coefficient between the PVD Ti1−xAlxN coated cemented carbide tools and the Inconel 718 material. The coating hardness and thermal conductivity of Ti1−xAlxN coatings increased with the increase of Al concentration x. Thirdly, the influences of PVD Ti1−xAlxN coated tools on the cutting temperature in turning Inconel 718 were analyzed by mathematical analysis modelling and Lagrange simulation methods. Compared with the uncoated tools, PVD Ti0.41Al0.59N coated tools decreased the heat generation as well as the tool temperature to reduce the thermal stress generated within the tools. Lastly, the influences of Ti1−xAlxN coatings on surface morphologies of the tool rake faces were analyzed. The conclusions can reveal the influences of PVD Ti1−xAlxN coatings on cutting temperature, which can provide guidance in the proper choice of Al concentration x for PVD Ti1−xAlxN coated tools in turning Inconel 718

Curing behaviors and mechanical properties of SiC-whisker-reinforced alumina ceramics fabricated with digital light processing

Silicon carbide whiskers (SiCw) have presented great potential to improve the mechanical properties of Al2O3 ceramic. However, effective curing of SiCw/Al2O3 ceramic slurry during digital light processing (DLP) is still challenged due to the high refractive index of SiCw. This paper aims to investigate the effect of SiCw content on rheological properties and associated curing behaviors of ceramic slurry. A modified Beer-Lambert model is proposed to evaluate the curing depth as functions of SiCw content and exposure parameters. The SiCw/Al2O3 ceramic slurries with the whiskers content of 0–16 vol.% are prepared and characterized. The results indicate that the curing depth decreased from 158 to 19 μm at the given exposure energy of 100 mJ/cm2 with the increase of SiCw content. The scattering and absorbance of light result in the decrease of curing depth and the geometrical overgrowth. The rheological properties of ceramic slurry are affected by the agglomerated whiskers. Furthermore, SiCw/Al2O3 ceramics are fabricated by DLP method, based on which the relationships among mechanical properties, microstructures and whiskers contents are determined. Significant effect of reinforcement is obtained in SiCw/Al2O3 ceramic due to whiskers pullout consuming the external loading energy. The microhardness and flexural strength of the SiCw/Al2O3 ceramics with 8 vol.% SiCw are 16.72 GPa and 208.5 MPa, respectively

Group 2 innate lymphoid cells boost CD8+ T-cell activation in anti-tumor immune responses

ABSTRACTGroup 2 innate lymphoid cells (ILC2s) are essential for orchestrating type 2 immune responses during allergic airway inflammation and infection. ILC2s have been reported to play a regulatory role in tumors; however, this conclusion is controversial. In this study, we showed that IL-33-activated ILC2s could boost CD8+ T-cell function through direct antigen cross-presentation. After activation by IL-33, ILC2s showed an enhanced potential to process antigens and prime CD8+ T cell activation. Activated ILC2s could phagocytose exogenous antigens in vivo and in vitro, promoting antigen-specific CD8+ T cell function to enhance antitumor immune responses. Administration of OVA-loaded ILC2s induces robust antitumor effects on the OVA-expressing tumor model. These findings suggested that the administration of tumor antigen-loaded ILC2s might serve as a potential strategy for cancer treatment

MiR-1180 promotes apoptotic resistance to human hepatocellular carcinoma via activation of NF-κB signaling pathway

Apoptosis resistance in human hepatocellular carcinoma (HCC) is a significant factor in carcinogenesis. Therefore, understanding the molecular mechanisms involved in apoptosis resistance is crucial for developing anticancer therapies. Importantly, small non-coding microRNAs (miRNAs) have been reported as key biomarkers for detecting tumour onset and progression. In the present study, we demonstrate that miR-1180 is upregulated in HCC. Ectopic expression of miR-1180 has an anti-apoptotic effect in HCC, while miR-1180 inhibition increases cell apoptosis, both in vitro and in vivo. Moreover, our results show that miR-1180 directly targets key inhibitors of the nuclear factor (NF)-κB signaling pathway (i.e., OTUD7B and TNIP2) and the pro-apoptotic Bcl-2 associated death promoter (BAD) protein by post-transcriptional downregulation. Therefore, the anti-apoptotic function of miR-1180 in HCC may occur through NF-κB pathway activation via downregulation of its negative regulators. In conclusion, our study reveals the critical role of miR-1180 during apoptosis resistance in HCC