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Flaw tolerance performance of TC4 alloy was investigated for helicopter transmission systems design. The impact pit flaws and scratch flaws were investigated by fatigue specimens with same flaw depth for flaw tolerance design，and high-cycle fatigue S-N curve tests were conducted. The results show that both scratch flaws and impact pit flaws significantly reduce the fatigue limit of the TC4 titanium alloy. The scratch flaw has a higher flaw influence factor（Kflaw） of 2.29 compared to the impact pit flaw’s Kflaw value of 1.75 under the same flaw depth conditions. Fracture surface analysis provided laws of the fatigue crack initiation and propagation associated with these flaws. Scratch flaws mainly exhibit multiple sources，with crack initiated at the root of the scratch，while the characteristics of fatigue crack initiation for impact pit flaws vary with the applied stress. Multiple sources are observed under high stress lever，with crack initiated on the surface of the pit，while under low stress，the crack initiates at a subsurface of the pit.

Mixed dimensional van der Waals heterostructure based on layered two-dimensional molybdenum disulfide (MoS2) interfaced to gallium nitride (GaN) has attracted tremendous attention due to its unique properties and application in novel electronic, optoelectronic, and quantum devices. However, developing facile synthesis methods and insights into the exciton dynamics for this system still remains a major challenge. Here, a simple and cost-effective method is demonstrated for large-scale synthesis of monolayer MoS2 on differently doped GaN substrates. A mixed aqueous solution of Na2MoO4 and NaOH is spin-coated on GaN and sulfurated in one step by chemical vapor deposition (CVD). High quality monolayer MoS2 nanosheets with side length over 400 μm and surface coverage ratio of more than 90 % are achieved on GaN. Furthermore, the PL intensity, excitonic transition ratios and ultrafast exciton dynamics of MoS2 are observed to be largely modulated by the doping type of GaN, owing to substrate-induced doping, which is proved by Raman, PL and transient absorption spectroscopy. Notably, p-GaN can attract electrons from monolayer MoS2 and weaken its intrinsic n-doping, thereby facilitating higher PL intensity as well as longer exciton lifetime, while n-GaN provides strong n-doping and generates opposite effect. This work hereby presents a pathway for large-scale synthesis of MoS2/GaN heterostructures and further understanding of their charge transfer properties and exciton dynamics, which should inspire their applications for optoelectronic devices.

In view of the problem that the gas turbine blades rely more on the long-term test of the whole machine in the later stage to expose the insufficient design, this paper takes the gas turbine blades of an engine as an example to study the low cycle fatigue life of gas turbine blades. Firstly, the stress-strain analysis of gas turbine blade is carried out under typical cycles. It is determined that the main failure mode of gas turbine blade is low cycle fatigue failure controlled by strain fatigue. According to the principle of linear damage accumulation, the low cycle fatigue life of gas turbine blade is predicted. Then, a design method of low cycle fatigue test of turbine blade on rotating test-bed is innovatively proposed. The method uses open-loop electromagnetic induction coil to heat the blade, realizes the temperature field of gas turbine rotor with temperature gradient through heat conduction, and determines the test speed of gas turbine rotor according to the principle of strain equivalence. The test results show that the predicted service life of gas turbine blade is within 5 times of service life dispersion zone, and the crack position of component test blade is consistent with the test results of the whole machine.

Over the past decade, the plasmonics of graphene and black phosphorus (BP) were widely recognized as promising media for establishing linear and nonlinear light-matter interactions. Compared to the conventional metals, they support significant light-matter interaction of high efficiency and show undispersed optical properties. Furthermore, in contrast to the conventional metals, the plasmonic properties of graphene and BP structure can be tuned by electrical and chemical doping. In this review, a deep attention was paid toward the second- and third-order nonlinear plasmonic modes of graphene and BP. We present a theoretical framework for calculating the lifetime for surface plasmons modes of graphene and BP assisted by the coupled mode theory. The effect of the Fermi energy on the second-order and third-order nonlinear response is studied in detail. We survey the recent advances in nonlinear optics and the applications of graphene and BP-based tunable plasmonic devices such as light modulation devices, switches, biosensors, and other nonlinear photonic devices. Finally, we highlight a few representative current applications of graphene and BP to photonic and optoelectronic devices.

The increasing demand for multispectral information acquisition and the complexity of application environments have sparked a growing interest in broadband detection. However, achieving a high level of responsivity across a wide response range remains a significant challenge. Herein, an ultrasensitive broadband phototransistor based on hybrid photogating (HPG) structure is demonstrated, which consisted of a quasi‐2D beta‐phase gallium oxide (β‐Ga2O3) nanoflake as the carrier transport channel and a tellurium (Te) nanoflake as the photogating layer. Attributed to the strong doping influence of the Te nanoflake, a low off‐state current of pA level and a high on/off current ratio of ≈108 are obtained. Upon 255 nm wavelength illumination, the device exhibited an ultrahigh responsivity up to 3.82 × 106 A W−1 and a detectivity as high as 1.59 × 1014 Jones across a large gate voltage range. Notably, an exciting infrared response is obtained with a responsivity of 138 A W−1 and a detectivity of 3.70 × 109 Jones under the 1550 nm wavelength illumination, exclusively achievable when the gate voltage exceeded 4 V. Leveraging the gate‐tunable spectral response, an innovative model for secure optical communication was proposed. This work presents an efficient and feasible strategy for fabricating multifunctional optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this article, a photodetector (PD) based on nanoporous (NP) AlGaO/AlGaN with efficient light capture and enhanced shortwave deep-UV (DUV) response has been demonstrated. A controllable electrochemical etching was utilized to obtain the NP-AlGaN with an extremely low reflectivity and a strong coupling absorption. After thermal oxidation, the NP-AlGaN was converted into NP-AlGaO, which can significantly suppress the dark current for the fabricated PD, resulting in a detectivity of up to 1.5 × 1013 Jones at 5 V. Meanwhile, defect passivation during oxidation significantly enhances its response speed (6–7 μs), contributing to a high gain-bandwidth product of 2.6 × 105. Critically, the NP-AlGaO/AlGaN hybrid structure greatly improves the responsivity for the shortwave DUV band and the high penetration confers the PD with even better detection capability in the wider DUV band. Therefore, the proposed device manipulating photon motion by means of novel nano-optical structures has great prospects for the detection of weak optical signals in the wide DUV spectral range, also opening up great opportunities for high-sensitivity sensors based on the nanostructured semiconductors. [ABSTRACT FROM AUTHOR]

Mixed dimensional van der Waals heterostructure based on layered two-dimensional molybdenum disulfide (MoS2) interfaced to gallium nitride (GaN) has attracted tremendous attention due to its unique properties and application in novel electronic, optoelectronic, and quantum devices. However, developing facile synthesis methods and insights into the exciton dynamics for this system still remains a major challenge. Here, a simple and cost-effective method is demonstrated for large-scale synthesis of monolayer MoS2 on differently doped GaN substrates. A mixed aqueous solution of Na2MoO4 and NaOH is spin-coated on GaN and sulfurated in one step by chemical vapor deposition (CVD). High quality monolayer MoS2 nanosheets with side length over 400 μm and surface coverage ratio of more than 90 % are achieved on GaN. Furthermore, the PL intensity, excitonic transition ratios and ultrafast exciton dynamics of MoS2 are observed to be largely modulated by the doping type of GaN, owing to substrate-induced doping, which is proved by Raman, PL and transient absorption spectroscopy. Notably, p-GaN can attract electrons from monolayer MoS2 and weaken its intrinsic n-doping, thereby facilitating higher PL intensity as well as longer exciton lifetime, while n-GaN provides strong n-doping and generates opposite effect. This work hereby presents a pathway for large-scale synthesis of MoS2/GaN heterostructures and further understanding of their charge transfer properties and exciton dynamics, which should inspire their applications for optoelectronic devices. [ABSTRACT FROM AUTHOR]