Defect and Diffusion Forum Vol. 412

Abstract: In order to guarantee the performant operation of the braking system of a racing car under high load an optimized thermal design of the braking system is an important factor. Especially in motorsports, a lot of braking energy is converted into heat due to short and intense braking events. Therefore, a suitable cooling concept is a crucial point to ensure a reliable thermal management of the braking system to dissipate the generated heat. In this work, the braking system of the formula student racing car of the UAS Esslingen is analysed using the racing car of the season 2019. A transient 1D simulation model of the heat balance of the braking system is created. For the determination of the heat transfer coefficients a steady 3D Conjugate Heat Transfer (CHT) simulation model is set up. The logging data of a real race are used for the validation of the presented model (s). The heat balance of the braking system, its entire heat flows as well as the time-dependent temperature evaluation of the brake disc are analysed and compared. The results of this analysis are used to create a cooling concept for the racing car’s braking system, to ensure an optimized braking performance over the entire race. Several different (geometrical) variants of the thermal design of the braking system are investigated using the above mentioned numerical models and the results are presented. Furthermore, the implementation of a cooling duct for the braking system is studied.

Abstract: This study was conducted using the existing ignition device to verify the effectiveness of LFG, a renewable energy source. The experimental method used a constant volume combustion chamber to check the flame propagation process and combustion pressure. The experiment was carried out by changing the fuel composition ratio of LFG in the range of LFG70 to LFG40. From the result, it was found that the methane combustion occurred smoothly in LFG70 during the flame propagation process, and that combustion progressed gradually over time. In the LFG60 and LFG50 regions, which are fuels with a high CO2 ratio, it was confirmed that the combustion slowed down and the brightness of the light decreased at the same time. In LFG40 with 40% of CH4, a misfire phenomenon in which combustion does not occur was discovered. For combustion pressure, the CH4 chemical composition of the LFG was lowered, which led to the combustion delay and the reduction of combustion pressure

Abstract: In this study, a thermal battery is designed with vacuum insulation to improve its thermal insulation. Thermal insulation is one of the many factors that determine the stability and operation of the battery. The battery’s operating time as well as the improvement in its thermal insulation performance were analyzed. The location of the vacuum insulation was set as a variable in the analysis models. The thermal battery was subjected to unsteady heat transfer analysis until the electrolyte temperature reached 450°C. Vacuum insulation was applied to the part of the base thermal battery to fabricate three model batteries. Compared with the base model B, the operating time increased by 48% for the model BS, 76% for the model BSB, and 179% for the model BSBT. Due to the large area of the side, a large amount of heat was transferred; the quantity of heat transfer was in the order B>BS>BSB>BSBT. In the model BSBT, the heat loss per unit area was reduced by 93% at the side, top, bottom compared with the base model. The results of this study will serve as basic data for the design of thermal batteries with vacuum insulation and for improvement in insulation performance.

Abstract: The problem of mathematical modeling the processes of water treatment from charged particles by electric field is considered. The problem is relevant due to the mass use of cleaning technologies in industry, medicine or the national economy. At the present stage, a significant improvement of purification system quality and the introduction of the technologies for the regeneration of their filtration components are required. Mathematical simulation using computer and supercomputer calculations helps to accelerate the development of new devices and cleaning technologies. On the basis of the chosen purification technology, it is important to create a numerical simulation apparatus with a controlled high accuracy of the calculations. For this purpose, we use a quasi-hydrodynamic (QHD) model of a viscous incompressible fluid flow, a system of convection-diffusion equations taking into account the action of the Lorentz force to describe the propagation of harmful impurities in aqueous medium, and an equation for the electric field potential [1, 2]. The numerical algorithm is based on the finite volume method. It is applied in the case of irregular unstructured meshes. This is important for problems of real two-dimensional (2D) and three-dimensional (3D) geometry. Time integration is performed according to an explicit scheme, which simplifies the procedure for parallelizing the algorithm. The proposed approach was tested on the examples of 2D and 3D geometry with various locations of the electrodes and various values of the potentials. The obtained results of the concentration of the ionic impurities show the possibility of this method to purify water from 10 to 40 percent. A design of a water purifier based on electrophysical purification technology can be developed on the base of this study.

Abstract: Timber drying consists of reducing the moisture content up to a level required by the intended application of the wood product. A proper drying operation is essential to reduce time and energy, as well as to prevent defects. Numerical simulation of this class of problems constitutes an important tool available to the process engineer to define the best drying schedule. However, a successful prediction requires knowledge of the wood properties and additional process parameters. This work is inserted within this framework and aims at discussing strategies do determine material and process parameters using inverse problem techniques. The timber drying process accounts for the fully coupled solution of the heat and mass (moisture) transfer problem, whereas the inverse problem is solved within the time domain based on population-based optimization techniques.

Abstract: An electromagnetic interferences (EMI) shielding is a material that attenuates radiated electromagnetic energy. Polymer nanocomposites is a class of materials that combine electrical, thermal, dielectric, magnetic and/ or mechanical properties, which are useful for the suppression of electromagnetic interferences. In this work, we looked over the effectiveness of the electromagnetic interferences shielding of polymer-based nanocomposites. These are thin samples of epoxy resin strengthened with nanostructured Cu powders. Nanostructured Cu powders were obtained by mechanical milling using the high-energy RETSCH PM400 ball mill (200 rpm). A powder sampling was conducted after 3h, 6h, 12h, 24h, 33h, 46h and 58h milling for characterization requirements. XRD analysis via the Williamson-Hall method shows that the mean crystallites size decreases from 151.6 nm (pure Cu phase) to 13.8 nm (58 h milling). Simultaneously, the lattice strain increases from 0.1% (pure Cu phase) to 0.59% (58 h milling). The elaboration of thin samples was performed by mixing a vol./3 fractions of nanostructured Cu powder, epoxy resin and hardener. Thin slabs of 1 mm thickness were moulded for use in a rectangular wave-guide. The EMI shielding experimental involved a two ports S parameters cell measurement made of R120 metallic wave-guides of rectangular section (19.05x9.525 mm²) and operational over the frequency band of 9.84 to 15 GHz associated to a network analyser. Obtained results show moderate EMI shielding effectiveness for the milled Cu-based slabs.

Abstract: Friction welding (FRW) is an important commercial solid-state welding process in which coalescence is achieved by frictional heat combined with pressure. The objective of this work is to analyze the microstructure and the mechanical behavior of the copper alloy UNS C64200 – bronze-aluminum-silicon, as well as to raise the ideal welding parameters so that there is adequate weldability after process of continuous-drive friction welding. Regarding the analysis of the microstructure, scanning electron microscopy was used to characterize phases. The mechanical properties were evaluated by means of a hardness test of the center of the welded joint, traversing the entire extent of the thermally affected zone. Results show that the UNS C64200 alloy, when subjected to conventional friction welding, behaves satisfactorily in terms of weldability, without the appearance of cracks or defects arising from the temperature characteristic of this process, as well as good hardness with values above the minimum established in norm and higher than the base material.

Abstract: Thermal fatigue widely takes place in light water reactor (LWR) piping systems. It is an important aging mechanism of a nuclear reactor. Thermal transient effects occur at the startup and shutdown of a nuclear power plant. During the thermal transients, local and global cyclic stresses are induced in the piping systems. They are exacerbated by local geometric imperfections and environmental factors, which may lead to crack initiation. The elbows of such piping systems are subject to various combinations of loads (internal pressure, bending, and torsion, as well as thermal fluctuations) during their service life. As can be seen, high-stress concentrations are developed in these piping elements. Therefore, it is important to make a failure evaluation. In this paper, a 12” pipe system segment, which was made with SA 106 Gr C steel, has been considered. It was composed by two straight sections joined by a long radius elbow. Typical start-up and shutdown transient effects of a BWR-5 were considered. A computer-aided thermo-mechanical analysis was carried out using the finite element method. The linearization of the stresses was considered, based on the ASME B & PVC Code Section III, subsection NB. Under these conditions, environmental fatigue was analyzed after 40-and 60-years operation.

Abstract: The future of construction will be directly connected with additive manufacturing (AM). It is easy to see the lack of consistency between jobs, labour inefficiency, schedule delays, delays on material delivery, exceeding budget projections and high percentage of material waste. Over the years, additive manufacturing has been a constant topic of discussion, in order to understand the limitations, applications and the overall impact on the cost of construction. In this work it is intended to present/discuss opportunities and challenges and the potential of AM to revolutionize the industry.