Nano and Battery Anode: A Review

Improving the anode properties, including increasing its capacity, is one of the basic necessities to improve battery performance. In this paper, high-capacity anodes with alloy performance are introduced, then the problem of fragmentation of these anodes and its effect during the cyclic life is stated. Then, the effect of reducing the size to the nanoscale in solving the problem of fragmentation and improving the properties is discussed, and finally the various forms of nanomaterials are examined. In this paper, electrode reduction in the anode, which is a nanoscale phenomenon, is described. The negative effects of this phenomenon on alloy anodes are expressed and how to eliminate these negative effects by preparing suitable nanostructures will be discussed. Also, the anodes of the titanium oxide family are introduced and the effects of Nano on the performance improvement of these anodes are expressed, and finally, the quasi-capacitive behavior, which is specific to Nano, will be introduced. Finally, the third type of anodes, exchange anodes, is introduced and their function is expressed. The effect of Nano on the reversibility of these anodes is mentioned. The advantages of nanotechnology for these electrodes are described. In this paper, it is found that nanotechnology, in addition to the common effects such as reducing the penetration distance and modulating the stress, also creates other interesting effects in this type of anode, such as capacitive quasi-capacitance, changing storage mechanism and lower volume change.

THE INFLUENCE OF POSTWELD TEMPERING ON MECHANICAL BEHAVIOR OF FRICTION WELDED JOINTS OF 32G2 AND 40HN STEELS UNDER HIGH-CYCLE FATIGUE

At modern mechanical facilities, the friction-welded joints are getting widespread as the most advanced production technique characterized by high efficiency, processability, cost-effectiveness, and safety. Moreover, it allows producing high-quality joints of a large number of different analogous and opposite metals and alloys. Despite all these advantages, one should consider that metal, in the process of welded joint formation, suffers a local thermo-deformational effect, which causes the gradient nature of the structure and residual strains of a welded joint. These factors directly influence the structure’s working ability and durability under fatigue loads, which are the most common cause for parts failure. The paper contains the assessment of the post-weld tempering influence on the cyclic life of welded joints of 32G2 and 40HN steels produced using the rotational friction welding technique. The authors tested laboratory specimens with welded joints under the high-cycle fatigue using the simulation machine with the two-point fastening of a revolving specimen under the action of even twisting moment. The study involved the statistical processing of the obtained results of cyclic life. Based on the metallographic analysis, the authors identified the weak points in welded points where the fatigue cracks initiation and progress occurred in the initial state and after tempering. The paper presents the fractographs illustrating the fracture mechanism of specimens under the study. The authors identified the influence of different tempering temperature modes on the cyclic life of the studied welded joints and the nature of their fracture. The study shows that tempering at the temperature over 400 °C promotes fracture acceleration under the effect of fatigue loads due to the development of return and polygonization processes in the vulnerable area of the thermomechanical action zone.

Modeling of Cyclic Life for Compressor Rotor of Gas Turbine Engine Taking Into Account Production Deviations

The regional aircraft with a turbofan gas turbine engine, created in Russia, is successfully operated in the world market. Further increase of the life and reduction of the cost of the life cycle are necessary to ensure the competitive advantages of the engine. One of the units limiting the engine life is the compressor rotor. The cyclic life of the rotor depends on many factors: the stress-strain state in critical zones, the life of the material under low-cycle loading, the regime of engine operation, production deviations (within tolerances), etc. In order to verify the influence of geometry deviations, the calculations of the model with nominal dimensions and the model with the most unfavorable geometric dimensions (worst cases) have been carried out. The obtained influence coefficients for geometric and weight tolerances are then used for probabilistic modeling of stresses in the critical zone. Rotor speed and gas loads on the blades for different flight missions and engine wear are determined from the corresponding aerodynamic calculations taking into account the actual flight cycles (takeoff, reduction, reverse) and are also used for stress recalculations. The subsequent calculation of the rotor cyclic life and the resource assessment is carried out taking into account the spread of the material low-cycle fatigue by probabilistic modeling of the rotor geometry and weight loads. A preliminary assessment of the coefficients of tolerances influence on stress in the critical zone can be used to select the optimal (in terms of life) tolerances at the design stage. Taking into account the actual geometric and weight parameters can allow estimating the stress and expected life of each manufactured rotor.