critical load
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2022 ◽  
Vol 305 ◽  
pp. 114314
Author(s):  
Yingzhuang Guo ◽  
Xiaoyan Wang ◽  
Charles Melching ◽  
Zhe Nan

2022 ◽  
Vol 48 ◽  
pp. 103999
Author(s):  
Jafar Khayatzadeh ◽  
Soodabeh Soleymani ◽  
Seyed Babak Mozafari ◽  
Hosein Mohammadnezhad Shourkaei

Electronics ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 80
Author(s):  
Hongjun Wang ◽  
Chunchao Song ◽  
Youjun Yue ◽  
Hui Zhao

Aiming to solve the problem of voltage fluctuation of critical load caused by lack of control when an unplanned island occurs in a microgrid, a voltage stabilizing control strategy of critical load based on electric spring is proposed in this paper. When unplanned islanding occurs in a microgrid system, the system bus voltage fluctuates dramatically due to instantaneous power imbalance, compromising the power supply safety of important loads on the bus. In this paper, the electric spring control mode is integrated into the voltage stabilizing control strategy of critical loads in an unplanned island for the first time to realize the protection of critical loads. First of all, a model of an optical storage AC/DC hybrid microgrid is built, the overall system architecture is determined, and the microgrid is divided into four working states. Second, the working principle of electric spring is introduced, and a decoupling control strategy based on double closed loop is proposed. Finally, the experimental simulation of the proposed control strategy is experimentally simulated in Matlab/Simulink environment. The simulation findings show that when the bus voltage and current of microgrid change due to an unplanned island, the proposed control strategy based on electric spring may achieve the stability of voltage and current on critical loads.


Author(s):  
Nаtalya Fidrovska ◽  
Viktoria Nesterenko ◽  
Ruslan Karavan

. The problems of the stability of rope drums are quite urgent. The rope drum is in most cases a thin-walled shell, which, under the influence of external pressure from the rope, can lead to loss of stability. The stability issues of the drum shell, which is loaded with rope turns, are very important, because the safety and reliability of the rope hoist is directly related to them The studies carried out made it possible to obtain a new method for calculating the stability of cylindrical shells, which takes into account not only the length of the shell, but also the rigidity of the connection with the head. In addition, a calculation formula was obtained to determine the critical pressure of the oval shell, which gives a fairly good agreement with the experiments of American scientists. The work also considered the effect of the difference in wall thickness on the critical load of the drum. The studies carried out made it possible to conclude that the parameters of the rope drums make it possible to completely eliminate the need to install rings and stiffeners. Also as a result of research it was found that the shell of the crane drum under the influence of a radial load cannot lose stability. Studies have shown that in all cases the stability margin of the rope drum shell is greater than the strength margin. In this case, the load created by the rope wound on the drum is considered, with the ratios of the radius of the drum and the rope typical for crane construction. In addition, a coefficient was established that takes into account the elasticity of the shell-head joint. The studies carried out have shown that such initial deviations of the drum shell shape as ovality do not give a significant increase in the critical load. The results obtained are quite important, since they allow reducing the metal consumption of the rope drum shell and at the same time ensuring its reliable operation. A decrease in metal consumption is achieved by reducing the thickness of the shell and the absence of the need to install rings and stiffeners. This will lead to a decrease in metal consumption and energy consumption of the crane itself, and also simplifies the technology of manufacturing a rope drum.


Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Hiroshi Yoshihara ◽  
Makoto Maruta

Abstract Buckling tests were conducted using slender specimens of western hemlock. In the tests, the slenderness ratio was varied from 132 to 418 in which elastic buckling was induced, and the values of the critical load for buckling were obtained. When the deflection of the specimen was calculated from the loading-line displacement based on elastica theory, the value of deflection/load initially decreased because the compressive deformation was more dominant than the bending deformation. In contrast, when the load increased, the bending deformation became dominant, and the deflection/load-deflection relation exhibited linearity. These tendencies indicated that the transition from compression to bending was induced around the minimum value of the deflection/load. Therefore, it was recommended to determine the critical load for buckling using the load at the minimum value of the deflection/load where the deflection was calculated from the loading-line displacement.


Friction ◽  
2021 ◽  
Author(s):  
U. Pranav Nayak ◽  
Sebastian Suárez ◽  
Valentin Pesnel ◽  
Frank Mücklich ◽  
María Agustina Guitar

AbstractIn the current study, an as-cast 26% Cr high chromium cast iron (HCCI) alloy was subjected to dry-sliding linear wear tests, under different loads. The loads were selected based on analytically computing the critical load (PC) i.e., the load necessary to induce plastic deformation. The PC was calculated to be 15 N and accordingly, a sub-critical load (5 N) and an over-critical load (20 N) were chosen. The influence of increasing the load during the wear test was investigated in terms of the matrix microstructural behaviour and its ability to support the surrounding carbides. The morphological aspects of the wear tracks, and the deformed matrix microstructure adjacent and underneath the track was analysed by confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM), respectively. No evidence of plastic deformation of the matrix was observed below PC. On the contrary, at loads equal to and higher than PC, the austenitic matrix plastically deformed as evidenced by the presence of slip bands. Electron backscattered diffraction (EBSD) measurements in terms of grain reference orientation deviation, and micro-Vickers hardness of the austenitic matrix indicated a deformation depth of about 40 µm at the maximum applied load of 20 N. The active wear mechanisms during sliding were a combination of both adhesive and abrasive wear, although increasing the load shifted the dominant mechanism towards abrasion. This was primarily attributable to the increased propensity for carbide cracking and fracturing, combined with the inability of the hardened austenitic matrix surface and sub-surface to adequately support the broken carbide fragments. Moreover, the shift in the dominant wear mechanism was also reflected in the wear volume and subsequently, the wear rate.


2021 ◽  
Vol 13 (4) ◽  
pp. 197-204
Author(s):  
Daniela BARAN ◽  
Mihaela PETRE

The purpose of this paper is to present a practical way to introduce distributed loads on the walls of a tank in order to perform a FEM analysis using PATRAN/NASTRAN programs. The problem is generated mainly by the fact that there are gravitational accelerations in the three directions of the moving airplane that produce a great number of combinations of inertial loads and consequently a great number of critical load cases. We compared the performed stress analysis with the loads obtained with this method in different cases for 𝑛𝑛=1. (Different forms of the fuel tanks and different placements of the tank inside the aircraft). The form and the density of the grid do not significantly affect the precision of the real inertia loads. Using the presented method one can reduce the volume of FEM files used in the analysis and can quite accurately reproduce the pressure loads on the fuel of a moving aircraft.


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