Nickel-based superalloys with multimodal γ′ size distribution microstructure have usually been widely used in many extreme engineering applications due to their excellent mechanical properties at high temperatures. Understanding the underlying mechanisms is vital to provide some insight into improving the performance. Up to now, a well understanding of the deformation mechanisms of unimodal microstructures has been obtained. However, it remains mysterious for superalloys with multimodal microstructures due to the complex size and distribution of γ′ particles. In this study, bimodal superalloys of GH4738 and GH4720Li alloys were selected. In GH4738 alloy, the fine and coarse γ′ particles are 32 nm and 221 nm, respectively, in which the coarse γ′ particles are all intragranular. In GH4720Li alloy, the fine and coarse γ′ particles are 37 nm and 1800 nm, respectively, in which most of the coarse γ′ particles are intergranular. In-situ neutron diffraction assisted by a 2-site elastic-viscoplastic self-consistent (EVPSC) model was employed to elucidate the deformation mechanisms. The effects of γ′ particles in different locations on the partitioning of interphase stress and deformation behaviour have been revealed through comparing with other unimodal superalloys. The results indicate that load partitioning between γ and γ′ phases is distinct between the unimodal and bimodal superalloys. On the one hand, premature load partitioning is observed before microscopic yielding, indicating that γ phase starts to deform plastically in elastic region. It could be attributed to the much lower critical stress of Orowan looping for intragranular coarse γ′ particles or the dislocations emitted by the straight interface plane of intergranular coarse γ′ particles in the bimodal superalloys. On the other hand, the extent of load partitioning at 15% strain for GH4738 and GH4720Li alloys is much lower than that of the unimodal superalloys with coarse γ′ particles, demonstrating that the effect of coarse γ′ particles on load partition is weakened by the shearing effect of fine γ′ particles. Those findings could contribute to a better understanding of deformation mechanisms in superalloys with multimodal γ′ size distributions and shine a spotlight on material design to modulate intergranular and interphase stresses.
The accurate detection of insulator profile of mine transmission line is the basis and premise of mine intelligent UAV (unmanned aerial vehicle) inspection, but it has not been effectively solved. In this paper, the mathematical model of traditional edge detection operator is first derivative operator: Robert operator, Prewitt operator, Sobel operator, and operators whose mathematical model is second derivative Laplacian operator, LOG operator, Canny operator and so on are studied comprehensively. These algorithms are applied to the insulator profile detection of transmission lines, and the experimental results are analyzed and compared.
In recent years, internet of things(IoT) development has brought new vitality to modernizing power grid equipment. In the smart IoT era, collecting distribution equipment data has also become intelligent. However, existing acquisition devices often have fixed functions, making them unable to accommodate diverse sensors. This paper develops a multifunctional acquisition device based on fast fourier transform(FFT) single-peak interpolation to enable dynamic port configuration. This allows effective collection of pressure, temperature, current, voltage, and other sensory data from distribution equipment. The device also enables real-time grid voltage harmonic calculation. Field testing showed the device maintained stability with good data upload rates under multiple sensor connections. The harmonic calculation accuracy met requirements, with an average 0.001% relative frequency error, 0.13% relative amplitude error, and 0.25° angular error.
Initial residual stress is omnipresent in biological tissues and soft matter, and can affect growth-induced pattern selection significantly. Here we demonstrate this effect experimentally by letting soft tubes grow in the presence or absence of initial residual stress and by observing different growth pattern evolutions. These experiments motivate us to model the mechanisms at play when a growing bilayer tubular organ spontaneously displays buckling patterns on its inner surface. We demonstrate that not only differential growth, geometry and elasticity, but also initial residual stress distribution, exert a notable influence on these pattern phenomena. Prescribing an initial residual stress distribution offers an alternative or a more effective way to implement pattern selection for growable bio-tissues or soft matter. The results also show promise for the design of 4D bio-mimic printing protocols or for controlling hydrogel actuators.
In the present study the authors performed surface treatment of stainless steel 65Mn (the thickness is 60 microm) by femtosecond laser (pulse duration 148 fs, wavelength 775 nm). The single-pulse threshold could be obtained directly to be about 0. 2 J x cm(-2). The authors found that the femtosecond laser produced a large number of micro-structures such as nano-pores and nano-protrusions. Then the authors discussed the influence of pulse power and the number of shots on the formed surface structures. The authors found that with the change in the power and the number of pulses, the period of multiple parallel grooved surface patterns remained unchanged, which is about on the sub-micron level. Finally the authors processed the array of holes and the lines with different speed and number of pulses.
The ultra-high-pressure (UHP) water-jet nozzle acts as one of the key units for the whole rotary sprayers, and its chamber shape plays a decisive role in improving the hydrodynamic performance of water jetting. Unfortunately, comprehensive and effective methods to optimize the nozzles' chamber shape are still lacking. By coupling a data-driven surrogate model with metaheuristic optimizer, a computational fluid dynamics (CFD)-based optimization scheme aiming at fully enhancing the hydrodynamic performance of UHP nozzles was proposed in this paper. Firstly, to ensure optimization accuracy, an improved whale optimization algorithm (IWOA) was developed. It combines the chaotic opposition-based learning (COBL) and the Cauchy-Gaussian mutation simulated annealing algorithms, incorporating a nonlinear convergence and adaptive inertia weight mechanism. Then, to reduce CFD computational costs and accelerate calculation speed, a data-driven surrogate model based on IWOA-support vector machine (SVM) was proposed. Herein, the parameter gamma and the penalty coefficient in SVM model, are trained using IWOA. The IWOA-SVM model was constructed using optimal Latin hypercube design (Opt. LHD) to sample nozzle structures, with peak wall shear stress (as objective function) calculated via CFD method. Finally, this optimization scheme was applied to optimize the chamber shape of the original nozzle commonly used in ship rust removal. The results reveal that the chamber shape of the optimized nozzle can greatly enhance the water-jet hydrodynamic performance by raising the peak wall shear stress by 13.88%. Additionally, the IWOA-SVM model demonstrates the capability to evaluate hydrodynamic performance with a maximum error of 2.853%. Therefore, the proposed optimization scheme provides novel insights for the overall design and optimization of the UHP water-jet nozzle.
An experiment device of cryogenic dew and frost point hygrometer is designed based on physical mechanism. Dew and frost on the chilled mirror are detected by transmitting an IR light with wavelength of 850 nm to mirror and receiving the reflected light after absorption of dew or frost by a photodiode. Special novel signal processing technologies for photoelectric integral and ambient light power suppression make the measurements can be done without any light shield. Peltier thermoelectric cooler (TEC) module is employed to heating or chilling mirror for clear or dew or frost, and served by Fuzzy-PID control logic algorithms and high-efficiency, switch-mode driver. Experiment results show that the instrument measuring dew or frost temperature is very accuracy and error less than 0.2 Celsius degree.
In this letter we investigate the propagation of nonlinear pulses along the free surface of flexible metamaterials based on the rotating squares mechanism. While these metamaterials have previously been shown to support the propagation of elastic vector solitons through their bulk, here we demonstrate that they can also support the stable propagation of nonlinear pulses along their free surface. Further, we show that the stability of these surface pulses is higher when they minimally interact with the linear dispersive surface modes. Finally, we provide guidelines to select geometries that minimize such interactions.
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