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Laminated composite bolted joints are increasingly used in the aerospace field, and their damage and failure behavior has been studied in depth. In view of the complexity and stability requirements of laminated composite bolted structures, accurate prediction of damage evolution and failure behavior is significant to ensure the safety and reliability of the structures. In this paper, a novel asymptotic damage model is developed to predict the damage process and failure behavior of laminated composite bolted joints. In this model, the modified Puck criterion and the maximum shear stress criterion are used for fiber yarns. The parabolic yield criterion is adopted for the matrix, and the fiber fracture, inter-fiber fracture and matrix fracture are considered at the microscopic level. The pull-out strength and progressive failure behavior of countersunk and convex bolted joints structures are predicted by using the proposed model, and the corresponding experimental studies are carried out. The results show that the prediction results are in good agreement with the experimental data, which verifies the reliability of the model. Additionally, the effects of different structural parameters (thickness and aperture) on the progressive damage and failure behavior during pull-out is analyzed by the proposed model, and correction factors of pull-out strength are obtained, which provides a powerful tool for the design, analysis and progression of laminated composite bolted joint structures. [ABSTRACT FROM AUTHOR]

AlCrSiN coatings are promising protective candidates for cutting and forming tools. During the coating deposition process, the microstructure and properties of the coatings were dramatically affected by bias voltages. To further optimize and enhance the AlCrSiN coating, a series of coatings were deposited at different pulse bias voltages using arc ion plating technology. By virtue of scanning electron microscopy, X-ray diffraction, scratch method, OCP, EIS, and other analytical methods, the effects of the pulse bias voltage on the crystal structure, microstructure, and mechanical, tribological, and electrochemical properties of the AlCrSiN coatings were analyzed. The study revealed that the pulse bias voltage exerted a slight influence on the aluminum and nitrogen content of the coatings. As the pulse bias voltage increased, the hardness, critical load, and tribological performance of the AlCrSiN coatings first increased gradually, and then were impaired slightly. When the pulse bias voltage was −100 V, the resulting AlCrSiN coating exhibited the densest structure, the highest hardness, the strongest adhesion, and the best wear resistance. In this case, the coating hardness and critical load reached 2668 HV and 72.7 N, respectively. The friction coefficient and wear rate were 0.35 and 1.02 × 10−3 μm3/N·μm, respectively. Simultaneously, the AlCrSiN coating demonstrated exceptional corrosion resistance in 3.5 wt.% NaCl solutions, surpassing uncoated 304 steel by 3~4 times. [ABSTRACT FROM AUTHOR]

In recent years, Offshore Wind Power (OWP) has gained prominence in China's national energy strategy. However, the levelized cost of electricity (LCoE) of wind power must be further reduced to match the average wholesale price. The cost-cutting and revenue-generating potential of offshore wind generation depends on technological innovation. The most recent studies and applications of offshore wind technology are thoroughly examined. (1) Techniques for site selection, such as site surveys, wind resource assessments, and environmental factors, are reviewed. (2) Three main technical components in offshore wind farms are discussed, including wind turbine, foundations, and booster stations. (3) The state-of-the-art method of the offshore wind farm's construction and operation and maintenance (O&M) practices is discussed. In situ marine geological surveying, large-scale offshore wind turbine manufacturing, integrated structural design, floating foundation design, flexible DC transmission technology, shortage of specialized vessels and equipment for construction, intelligence of O&M, and other issues are challenging China's OWP industry. A brief overview of China's efforts in standardization, parity, and research and development are discussed. Recommendations for future development of the wind power industry are provided for China, which may be referable for other nations with comparable circumstances. [ABSTRACT FROM AUTHOR]

In order to further improve the mechanical and tribological properties of AlCrTiSiN coating, annealing treatment was carried out in this work. X-ray diffraction (XRD), scanning electron microscopy (SEM), nanoindentation, scratch tester, friction, and a wear tester were used to characterize and explore the effects of annealing temperature on the coating composition, phase component, surface and cross-sectional morphology, and mechanical properties as well as the friction and wear performance of the AlCrTiSiN coatings. The results indicated that after the vacuum annealing the content of amorphous phase decreased and the average size of nanocrystals increased in varying degrees. With the increase in annealing temperature the coating surface became smoother and the cross-section morphology changed little. The coating hardness first increased and then decreased. The adhesion between the coating and substrate decreased after annealing, but the wear resistance was improved. When the annealing temperature was 800 °C, the mechanical properties and wear resistance of the resulting coating were the best. In this case, the coating hardness was 27 GPa, the critical load was 61 N, the friction coefficient was 0.66, and the wear rate was 1.97 × 10−3 μm3/N·μm−1. [ABSTRACT FROM AUTHOR]

To take advantage of the synergistic effects of Pt and Zr, a kind of Zr-doped, Pt-modified aluminide coating has been prepared by a hybrid process, first electroplating a Pt layer and then co-depositing Zr and Al elements by an above-the-pack process. The microstructure and isothermal oxidation behavior of the coating has been studied, using a Pt-modified aluminide coating as a reference. Results showed that the Zr-doped, Pt-modified aluminide coating was primarily composed of β-(Ni,Pt)Al phase, with small amounts of PtAl2- and Zr-rich phases dispersed in it. The addition of Zr diminished voids on the coating surface since Zr could hinder the growth of β-NiAl grains. It also helped to increase the spalling resistance of the oxide scale and reduce the oxidation rate, which made the Zr-doped, Pt-modified aluminide coating possess better oxidation resistance than the reference Pt-modified aluminide coating at the temperature of 1100 °C. [ABSTRACT FROM AUTHOR]

Four CrAlSiN coatings with different Al contents were prepared by varying Al sputtering power using a combined method of high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS). Microstructure, chemical compositions and mechanical properties of the four coatings were characterized by XRD, XPS, SEM, TEM, nano-indentation etc. Results showed that the four coatings possessed face-centered cubic (fcc) CrN phase with Al and part of Si dissolved in it. Another part of Si existed as amorphous phase in the coatings. All the four coatings had columnar structure and formed in epitaxy growth by template effect. With increasing Al sputtering power, the Al content increased from 11.4 to 17.6 at.% gradually, while the Cr content decreased a little. The hardness of the CrAlSiN coatings increased initially probably due to the refinement of the coating grain size, while it decreased afterwards mainly caused by the aggregation of small particles leading to rougher surface and defects formed in the coatings. The elastic modulus and adhesive strength possessed the same variation tendency as the hardness versus Al sputtering power. The CrAlSiN coating with Al sputtering power of about 0.8 kW had the highest hardness of about 26.7 GPa and adhesive strength of about 27.2 N. [ABSTRACT FROM AUTHOR]

A Si doped Pt modified aluminide coating was prepared by electroplating and the chemical vapour deposition method. The microstructure and oxidation resistance of the coating were studied, with a single Pt modified aluminide coating as a reference. The results showed that the Si doped Pt modified aluminide coating consisted of singular β-(Ni, Pt)Al phase, and no PtAl2 phase was detected, which might be due to the fact that the addition of Si retarded the formation of PtAl2 phase in the outer layer. Si was dissolved in the β-(Ni, Pt)Al phase in the outer layer and might form silicide with refractory elements in the inter-diffusion zone. The Si doped Pt modified aluminide coating possesses a better oxidation resistance than the Pt modified aluminide coating since Si could promote the formation of α-Al2O3 and inhibit the diffusion of the refractory elements, reducing the formation of detrimental volatile phase. [ABSTRACT FROM AUTHOR]