Ing. Kateřina Nováková

Fibre-reinforced concrete is a new composite material whose advantages include tensile strength or resistance to extreme loadings. The strength of the reinforcement can be further improved by orienting the fibres in a magnetic field. The orientation of fibres must be done immediately after pouring the concrete into a form.One of the applications where it is possible to take advantage of the behaviour that the prefabricated building material acquires after the orientation of the fibres is the use in the production of prefabricated slabs, which are normally produced in a factory outside the area of the construction site. The characteristic properties imposed on the slab are the non-uniform distribution of the required strength, with the highest required strength in the center and the lowest required strength at the edges. This makes it a direct opportunity to use dispersed reinforcement and to orient the fibres in the concrete mixture according to the demand of the customer. Based on this, a robotic device has been developed in which the fibres will be automatically oriented according to the individual requirements of the user. This paper presents a device developed to experimentally verify the possibility of orienting steel fibres in slabs to increase their mechanical strength.

Experimental studies of lithium-ion batteries are very often based only on deep charge and discharge cycles. However, these test profiles do not fully reflect the actual operation of the battery in an electric vehicle or in stationary applications, where the battery is not only loaded during the main charging and discharging profiles, but it is also stressed by the current throughput caused by renewable power fluctuations or by auxiliary services. These cycles, which are superimposed to the main charge and discharge processes and have a depth of discharge not exceeding 2%, are called micro-cycles. Although there are several simulation studies that attempt to capture this issue, there is still no comprehensive experimental study that has the phenomena that occur during micro-cycling. This paper presents an experimental analysis of micro-cycles, providing a detailed view of the different processes taking place in the battery during aging, by means of a detailed analysis of the results from electrochemical impedance spectroscopy (EIS). By studying the single electrochemical processes in detail, this paper explains the benefits of micro-cycling in terms of extending the lifetime of the battery.

Electrochemical impedance spectroscopy (EIS) is a measurement method widely used for non-destructive analysis and diagnostics in various electrochemical fields. From the measured dependence of the battery impedance on the frequency, it is possible to determine the parameters of various equivalent electrical circuit models of the battery. The conventional method of battery measurement using single-sine EIS is currently one of the most widely used methods for the analysis of lithium-ion batteries. However, its most significant disadvantage is the relatively long measurement time. For this reason, there is a growing demand for faster methods using fast-Fourier transform or pseudo-random sequences. A description of various EIS methods applications is provided in this paper.

The last decade has seen a significant increase in electromobility. With this trend, it will be necessary to start dealing with the subsequent recycling and disposal of electric vehicles, including the batteries. Currently, the battery is one of the most expensive components of an electric vehicle, which in part hinders their sufficient competitiveness with the internal combustion engine. Furthermore, the lifetime of a battery for use in an electric vehicle is assumed to be 8–10 years/160,000 km, after which the battery capacity drops to 80% of the initial capacity. However, it transpires that a battery at the end of its life in an electric vehicle does not need to be disposed of immediately, but can be used in other applications wherein the emphasis is not so strictly on an excellent power and capacity capability related to its volume or weight. Thus, reusing batteries can help reduce their cost for use in electric vehicles, increase their utility value, and reduce the environmental impact of batteries. This paper discusses methods for researching battery aging in electric vehicles, testing methods for batteries during the transition from first life to second life, and prospective battery second-life use and its specifics. The main contribution of this perspective article is to provide a comprehensive view of the current state of second-life batteries and an overview of the challenges that need to be overcome in order to use them on a large industrial scale.

Fiber-reinforced concrete is a new composite material whose advantages include tensile strength or resistance to extreme loadings. The strength of the reinforcement can be further improved by orienting the fibers in a magnetic field. The orientation must be done immediately after pouring the black concrete into a form. This paper deals with the magnetic field simulation acting on a steel fiber in the Ansys Maxwell environment. The simulation examines the electromagnetic toque affecting the steel fiber based on its geometry. The model consists of a fiber inserted between Helmholtz coils. Torque curves for various fibers were monitored, and based on the results, a comparison between several commercially available fibers is presented. Furthermore, a device used for measuring the magnetization and hysteresis curves was simulated, and the results are presented in the paper

The efficiency of fibre reinforcement in concrete can be drastically increased by orienting the fibres using a magnetic field. However, the parameters of such a field are not immediately apparent, as they depend on the specific fibre reaction to the magnetic field. In this paper, numerical simulations are conducted to study the mechanical torque acting on fibres placed in a magnetic field. The simulations are verified with an experimental setup as well as theoretical relationships. Ten different fibre types, both straight and hook-ended, are examined. The developed model can be successfully used to study the behaviour of fibres in a magnetic field. The fibre size plays the most important role together with the magnetic saturation of the fibre material. Multiple fibres show significant interactions.