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The mechanical contact properties of M50 aviation bearing steel surfaces by using ultrasonic-assisted electrolytic in-process dressing (UA-ELID) grinding greatly influence the machined surface's quality. However, in wet grinding conditions, there are three contact forms on the grinding surface: the micro-cutting contact between the diamond abrasive particles of the grinding wheel and the workpiece surface, the sliding contact between the oxide film asperities on the grinding wheel surface and the asperities on the workpiece surface, and the hydrodynamic liquid film contact of the electrolytic grinding solution. The existing research on the mechanical behaviour of the grinding contact surfaces mainly focuses on the influence of one of the contact forms on the normal force. Therefore, calculation models of the dynamic solid-liquid mixing normal force of the UA-ELID grinding contact surfaces that with three contact forms are constructed in this paper to accurately understand the mechanical contact properties of the grinding surface. The relationship between the three contact forms under different process conditions, such as wheel speed, feed depth, and feed speed, and their influence on the normal force of the grinding contact surfaces are revealed. Finally, the accuracy and versatility of the calculation models in this paper are verified through comparative analysis with other normal force calculation model and experimental measurement. [Display omitted] • The contact mechanical models of grinding surfaces under the action of three contact forms were constructed. • The normal force generated by abrasive micro cutting is about 60% of the sliding contact of the asperities. • It reveals the shortcomings of the grinding specific energy normal force calculation model in the application process. [ABSTRACT FROM AUTHOR]

The attractive specifications of vertical axis wind turbine (VAWT) are its operating with low noise and wind in various directions. To achieve a higher performance of these turbines, modeling of a curved‐blade VAWT by the modified double multiple streamtube (DMST) method and optimizing this wind turbine are performed. The power coefficient and the total normal force acting on blades were selected as two objective functions. Minimizing the normal force acting on turbine blades as the second objective function was not observed in the open literature. The amount of normal force is crucial in the structural design of VAWT because it generates both the bending moment on blades and forces on supporting arms of VAWT. Another innovation of this study is to consider the shape coefficient parameter that determines the shape of the rotor geometry as a design variable in optimization procedure. A 3 m height curved‐blade VAWT type was optimized by this multi‐objective optimization technique. The optimum values of the design variables obtained by the Genetic Algorithm were selecting an elliptical rotor geometry, pitch angle −1.4°, diameter/height 1.3, blade aspect ratio 19.8, tip speed ratio 4.3 and selecting three blades which could provide a power coefficient of 0.49 and a normal force of 158.7 N. [ABSTRACT FROM AUTHOR]

Nowadays, many scholars have been studied the normal force of MRF in the uniform magnetic field. However, the research on the normal force of MRF in the non-uniform magnetic field is relatively limited. The non-uniform magnetic field can cause the MRF to generate normal force of different sizes and directions to cope with different working conditions, thus the normal force generated in the non-uniform magnetic field require more attention. In this paper, a theoretical model of the normal force of MRF in the non-uniform magnetic field was developed based on the enhanced magnetic dipole model. The normal force of MRF within a unit area can be calculated based on this theoretical model. However, the magnetic induction intensity is different at different locations of the non-uniform magnetic field, which leads to the normal force generated by the MRF are not accurately calculated. Therefore, it is necessary to use COMSOL to establish the material model of the MCR-302 plate rheometer and MRF to verify the accuracy of the proposed model. Then a flat-plate rheometer was used to test the static normal force of the MRF in the non-uniform magnetic field. Finally, the simulation and experimental data were compared. The results show that the simulation result with the experimental data is a good agreement, which verifies the reliability of the theoretical model. The static normal force of the MRF increases with the increase of volume fraction and magnetic field intensity. [ABSTRACT FROM AUTHOR]