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[en] This paper enlarges an undergraduate student project in non-holonomic mechanics (Janova et al 2009 Eur. J. Phys. 30 1257-69) by considering rolling friction. In the original problem of coupled rolling motion, the agreement of theory and experiment was demonstrated for the initial part of motion with rolling friction being neglected. As expected, the reality is that rolling friction plays a decisive role during the whole experiment. Extending the correspondence of the model to reality by considering rolling friction, in this paper it is demonstrated that the model satisfactorily explains not only the initial part but also the whole period of the motion observed. Together with the original problem, this paper is an interesting demonstration of the influence of rolling friction and its physical modelling for undergraduate physics education. It also demonstrates that a relatively simple theoretical background can be used for describing realistic situations in mechanics and for explaining experimental results. Moreover, this paper itself can be used by physics teachers as an interesting project in theoretical mechanics that may be solved both separately from and as a follow-up project to Janova et al (2009).
[en] Aiming at the problem of excessive mechanical loss of the conventional vane compressor, this paper proposes a novel vane compressor structure. This compressor can significantly reduce the mechanical frictional loss through converting sliding friction between vane tip and cylinder into rolling friction by using a rolling bearing. The structure and operation principle are introduced in this paper, and mechanical friction loss calculation models of these two kinds of compressor are theoretically analyzed. The results show that mechanical loss of the novel vane compressor can be reduced by nearly 38% under the same working conditions. At the same time, the actual tested results indicated that the total power consumption of compressor decreased 160.1W (6.89%), and the COP increased by 11.89%. (paper)
[en] The mechatronic system of the DUO-300 rolling mill is analyzed. The influence of the roller’s linear velocity on the distribution of frictional forces in the rolling region is studied. A nonlinear relation is found between the load and the roller speed. The conditions of self-oscillation in rolling are determined. Methods of damping the self-oscillation are considered.
[en] Highlights: • An ultra-robustness HCS-TENG was got by rolling contact electrification and Faraday's Law. • The device gets the high output power, good energy-harvesting capacity in a wider frequency range. • A self-powered multifunctional sensors can be attained by the output signal of TENG. Collecting mechanical energy in the surrounding environment to power small electronic devices is an ideal method as a green and clean power source. Based on the working mechanism and the advantages of triboelectric nanogenerator (TENG), a robust rolling friction contact-separation mode TENG (CS-TENG) has been fabricated for harvesting vertical rotation energy by utilizing the integrated cylindrical surface with the conjunction of rolling contact electrification and electrostatic induction. The output current of the CS-TENG can maintain 96% (origin: 1.72 μA, final: 1.66 μA) after two days continuous work a rotation speed of 300 r/min. Furthermore, an electromagnetic and triboelectric hybrid contact-separation mode nanogenerator (HCS-TENG) has been further designed by coupling magnets in the rolling cylinders with copper coils as an electromagnetic generator (EMG) in the acrylic cylinder to implement the multi-functional properties. The gear transmission structure makes the device more facile to be installed on the rotation objects. The output performances of CS-TENG and EMG under various rotation speeds were systematically studied. It shows that the CS-TENG with six units can deliver an output power of 0.15 mW/cm2 and the 100 μF capacitor can be charged to 6 V in less than 1 min by the hybridized nanogenerator at a rotating rate of 700 r/min. In addition, utilizing the output signal's intrinsic characteristics of CS-TENG, a self-powered rotation speed and displacement sensor using the dual cylinder structure TENG has been achieved for these rotating mobile devices that are inconvenient to get an additional power supply in the grimmest circumstances such as moon car or other celestial and tough environment detection equipment. This multifunctional TENG device reveals a significantly potential application in the grimmest circumstances as power source, self-powered electronics and sensor systems.
[en] The paper presents the results of the scientific and practical research of roller systems operation at feed of liquid lubricating materials through the example of the wide strip hot rolling Mill-2000 at PAO MMK. The experiments proved that application of lubricating materials leads to decrease of energy-power parameters of the process by 12 to 15 %, and reduction of work roll wear by 10 to 12%. The practical results of the study are developed recommendations on determination of consumption-volumetric parameters of the supplied lubricating material depending on rheological and geometrical parameters of the rolled strip and current wear of work rolls. (paper)
[en] A coefficient of contact friction with rolls has been theoretically determined from a forward flow on dependence on reduction during stainless steel rolling. The problem was solved with provision for true nonuniform pressure along a tangential arc. A degree of divergence for the coefficients of friction has been revealed
[en] Given are the results of the study on substructure changes in Mo monocrystals during plastic deformation. The method of diffraction of wide divergent X-ray beam is applied. It is shown that for the degrees of total deformation above 50% the improvement of the structure takes place, which is characterized by the decrease in subboundary angles and the decrease in local stresses and lattice distortions over a subgrain body
[en] The paper presents a method of establishing the coefficient of rolling friction by the study of the damped motion of a pericycloidal pendulum. The pericycloid is the curve described by a point belonging to a mobile circle, which is in pure rolling around a fixed circle, accomplishing an interior contact. For a pendulum with known inertial characteristics, mass and moment of inertia, the equation of motion is found starting from the assumption of a linear dependence between the friction torque and the normal reaction force from contact point. Using an experimental set-up, the law obeyed by damped angular amplitude versus time is found for a pericycloidal pendulum. The experimental data are compared to the theoretical ones, by superposition; thus, the value of coefficient of rolling friction is obtained. The values are in a good agreement with the ones from technical literature. (paper)