The aim of this work is to investigate the effect of the small magnetorheological fluid gap on the braking performance of the magnetorheological brake. In this article, theoretical analyses of the output torque are given first, and then the operating principle and design details of the magnetorheological brake whose magnetorheological fluid gap can be altered are presented and discussed. Next, the magnetic circuit of the proposed magnetorheological brake is conducted and further followed by a magnetostatic simulation of the magnetorheological brakes with different sizes of fluid gap. A prototype of the magnetorheological brake is fabricated and a series of tests are carried out to evaluate the braking performance and torque stability, as well as the verification of the simulation results. Experimental results show that the braking torque increases with the increase in the current, and the difference for the impact of the fluid gap on braking performance is huge under different currents. The rules, which the experimental results show, have an important significance on both the improvement of structure design for magnetorheological brake and the investigation of the wear property under different fluid gaps.
In order to investigate the causes of the large number of cracks and porosities formed in 33MnCrTiB fork flat steel produced by a special steel plant, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) analysis, and large sample electrolysis of the obtained steel samples were carried out in different steps of the steelmaking processes. The main micro-inclusions in the fork flat steel samples were Al2O3, CaO-MgO-Al2O3-SiO2, and TiN, and the macro-inclusions were mainly Al2O3, CaO-Al2O3, CaO-Al2O3-SiO2-TiO2, and CaO-MgO-Al2O3-SiO2-TiO2-(K2O) systems which originated from the ladle slag and mold flux in the production process. In order to reduce the number of micro-inclusions effectively, the control range of components in the refining slag was confirmed by the thermodynamic calculation, where the mass ratio of CaO/Al2O3 should be in the range of 1.85–1.92, and the mass fraction of SiO2 and MgO should be controlled to 7.5–20% and 6–8%, respectively. In addition, the numbers of macro-inclusions in the flat steel should be effectively reduced by optimizing the flow field of mold and preventing the secondary oxidation, and the flat steel quality problems caused by the inclusions can be improved by the optimization process above.
An optimization design method is developed for the beam pumping unit, which is based on the API-RP-11L design criteria. The Response Surface Method is used to calculate the structural reliability of the beam pumping unit. The optimization design method not only provides an efficient and fast optimization tool for the modular design of the beam pumping unit, but also offers an integral design calculation in accordance with the API design code. The function and theory of this optimization design method are given by this paper, as well as some concrete calculation examples.
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