Design and optimization of Metallic Foam Shell protective device against flying ballast impact damage in railway axles

Abstract Ballast impacts can initiate surface defects that cause abrupt failure of the axle and derailment of the railway vehicle. According to the Federal Railroad Administration the axle and bearing failure costs around 89 million dollars and causes 46 derailments in the US per year (2005–2010). In this study, the authors have suggested a novel protective mechanism (Metallic Foam Shell – MFS) by using a lightweight sandwich panel. At the first step, a preliminary study is conducted, followed up by the numerical simulations to determine the applicable materials. At the next step, experimental tests were performed to assess the efficiency of the suggested device against flying ballast impacts. An extended non-destructive (NDT) evaluation has been performed in order to find the most suitable technique for damage detection of the proposed device when on-service. The studied cases were GFRP and Aluminium sandwich panels, having an aluminium foam core with different densities and thicknesses. The results showed that the MFS can absorb up to 90% of the initial impact energy and significantly decrease the chance of rebounding impact to the other components. Moreover, the results were also analysed in order to propose the most reliable NDT method for this specific application

Design of an Innovative Hybrid Sandwich Protective Device for Offshore Structures

Lightweight foam sandwich structures have excellent energy absorption capacity, combined with good mechanical properties and low density. The main goal of this study is to test the application of an innovative hybrid sandwich protective device in an offshore wind turbine (OWT). The results are useful for offshore structure applications. Different lightweight materials (aluminum foam, agglomerated cork, and polyurethane foam) were investigated using experimental tests and numerical simulations. Closed-cell aluminum foam showed the best performance in terms of the energy absorption capacity during an impact. As such, a Metallic Foam Shell (MFS) device was proposed for the fender of offshore wind turbines. A finite element model of a ship-OWT collision scenario was developed to analyze the response of a fender with the MFS device under repeated impacts. The proposed MFS fender can be used efficiently in a wide temperature range, allowing it to be used in harsh climatic conditions

Strength Evaluation of Functionalized MWCNT-Reinforced Polymer Nanocomposites Synthesized Using a 3D Mixing Approach

The incorporation of carboxyl functionalized multi-walled carbon nanotube (MWCNT- COOH) into a polymethyl methacrylate (PMMA) has been investigated. The resultant tensile and flexural mechanical properties have been determined. In this paper, a novel synthesis process for a MWCNT-reinforced polymer nanocomposite is proposed. The proposed method significantly eliminates the most challenging issues of the nano-dispersed phase, including agglomeration and non-homogeneous mixing within a given matrix material, and also resolves the issues occurring in conventional mixing processes. The results of scanning electron microscopy support these claims. This 3D-mixing process is followed by an extrusion process, using a twin-screw extruder for pristine MWCNT, and a compression molding process for COOH-MWCNT, to prepare test specimens for experimentally determining the mechanical properties. The test specimens are fabricated using 0.1, 0.5, and 1.0 wt.% MWCNT, with a remaining PMMA phase. The testing is conducted according to ASTM D3039 and ASTM D7264 standards. Significant improvements of 25.41%, 35.85%, and 31.75% in tensile properties and 18.27%, 48%, and 33.33% in flexural properties for 0.1, 0.5, and 1.0 wt.% COOH-MWCNT in PMMA, respectively, compared to non-functionalized MWCNTs, were demonstrated. The highest strength was recorded for the nanocomposite with 0.5 wt.% f-MWCNT content, indicating the best doping effect at a lower concentration of f-MWCNT. The proposed CNT-PMMA nanocomposite may be found suitable for use as a scaffold material in the domain of bone tissue engineering research. This type of research possesses a high strength requirement, which may be fulfilled using MWCNT. Furthermore, this analysis also shows a significant amount of enhancement in flexural strength, which is clinically required for fabricating denture bases.This research was funded by a grant from the Romanian Ministry of Research, Innovation, and Digitalization, project number PFE 26/30.12.2021, PERFORM-CDI@UPT100—The increasing of the performance of the Polytechnic University of Timis, oara by strengthening the research, development, and technology transfer capacity in the field of “Energy, Environment and Climate Change” at the beginning of the second century of its existence, within Program 1—Development of the national system of Research and Development, Subprogram 1.2—Institutional Performance-Institutional Development Projects—Excellence Funding Projects in RDI, PNCDI III.info:eu-repo/semantics/publishedVersio

Dynamics of MHD Convection of Walters B Viscoelastic Fluid through an Accelerating Permeable Surface Using the Soret–Dufour Mechanism

The MHD convective Walters-B memory liquid flow past a permeable accelerating surface with the mechanism of Soret-Dufour is considered. The flow equation constitutes a set of partial differential equations (PDEs) to elucidate the real flow of a non-Newtonian liquid. The radiation thermo-physical parameters were employed based on the use of Roseland approximation. This implies the fluid employed in this exploration is optically thick. Utilizing suitable similarity terms, the flow equation PDEs were simplified to become total differential equations. The spectral homotopy analysis method (SHAM) was utilized to provide outcomes to the model. The SHAM involves the addition of the Chebyshev pseudospectral approach (CPM) alongside the homotopy analysis approach (HAM). The outcomes were depicted utilizing graphs and tables for the quantities of engineering concern. The mechanisms of Soret and Dufour were separately examined. The imposed magnetism was found to lessen the velocity plot while the thermal radiation term elevates the temperature plot because of the warm particles of the fluid.This research was funded by a grant of the Romanian Ministry of Research, Innovation and Digitalization, project number PFE 26/30.12.2021, PERFORM-CDI@UPT100—The increasing of the performance of the Polytechnic University of Timis, oara by strengthening the research, development and technological transfer capacity in the field of “Energy, Environment and Climate Change” at the beginning of the second century of its existence, within Program 1—Development of the national system of Research and Development, Subprogram 1.2—Institutional Performance—Institutional Development Projects—Excellence Funding Projects in RDI, PNCDI III.info:eu-repo/semantics/publishedVersio

On the Lateral Compressive Behavior of Empty and Ex-Situ Aluminum Foam-Filled Tubes at High Temperature

In this research work, the effect of lateral loading (LL) on the crushing performance of empty tubes (ETs) and ex situ aluminum foam-filled tubes (FFTs) was investigated at 300 °C. The cylindrical thin-walled steel tube was filled with the closed-cell aluminum alloy foam that compressed under quasi-static loading conditions. During the compression test, the main mechanical properties of the ETs improved due to the interaction effect between the cellular structure of the foam and the inner wall of the empty tube. In addition, the initial propagated cracks on the steel tubes reduced considerably as a result of such interaction. Furthermore, the obtained results of the LL loading were compared with the axial loading (AL) results for both ETs and FFTs at the same temperature. The findings indicated that the application of loading on the lateral surface of the composite causes the lower mechanical properties of both ETs and FFTs in comparison with the axial loading conditions

Compressive Behavior of Aluminum Microfibers Reinforced Semi-Rigid Polyurethane Foams

Unreinforced and reinforced semi-rigid polyurethane (PU) foams were prepared and their compressive behavior was investigated. Aluminum microfibers (AMs) were added to the formulations to investigate their effect on mechanical properties and crush performances of closed-cell semi-rigid PU foams. Physical and mechanical properties of foams, including foam density, quasi-elastic gradient, compressive strength, densification strain, and energy absorption capability, were determined. The quasi-static compression tests were carried out at room temperature on cubic samples with a loading speed of 10 mm/min. Experimental results showed that the elastic properties and compressive strengths of reinforced semi-rigid PU foams were increased by addition of AMs into the foams. This increase in properties (61.81%-compressive strength and 71.29%-energy absorption) was obtained by adding up to 1.5% (of the foam liquid mass) aluminum microfibers. Above this upper limit of 1.5% AMs (e.g., 2% AMs), the compressive behavior changes and the energy absorption increases only by 12.68%; while the strength properties decreases by about 14.58% compared to unreinforced semi-rigid PU foam. The energy absorption performances of AMs reinforced semi-rigid PU foams were also found to be dependent on the percentage of microfiber in the same manner as the elastic and strength properties

Correlations between Process Parameters and Outcome Properties of Laser-Sintered Polyamide

As additive manufacturing (AM) becomes more accessible, correlating process parameters with geometric and mechanical properties is an important topic. Because the number of process variables in AM is large, extensive studies must be conducted in order to underline every particular influence. The study focuses on two variables—part orientation in the orthogonal horizontal plane and energy density—and targets two outcomes—geometric and tensile properties of the parts. The AM process was conducted on selective laser sintering (SLS) machine EOS Formiga P100 using EOS white powder polyamide (PA2200). After finishing the sinterization process, the parts were postprocessed, measured, weighted, and mechanically tested. The geometric evaluation and mass measurements of every sample allowed us to compute the density of all parts according to the sinterization energy and orientation, and to determine the relative error of every dimension. By conducting the tensile testing, the elastic and strength properties were determined according to process variables. A linear trend regarding sample density and energy density was identified. Also, large relative dimensional errors were recorded for the lowest energy density. Mechanical properties encountered the highest value for the highest energy density at a 45° orientation angle

Influence of Manufacturing Parameters on Mechanical Properties of Porous Materials by Selective Laser Sintering

This paper presents a study on the tensile properties of Alumide and polyamide PA2200 standard samples produced by Additive manufacturing (AM) based on selective laser sintering (SLS). Because of the orthogonal trajectories of the laser beam during exposure, different orientations of the samples may lead to different mechanical properties. In order to reveal this process issue, four orientations of the samples in building envelope were investigated. For data reliability, all the other process parameters were constant for each material and every orientation. The tensile tests highlight small differences in elastic properties of the two materials, while significant differences in strength properties and energy absorption were observed. Nevertheless, Young modulus indicates high stiffness of the Alumide comparing to PA2200 samples. The stereo microscopy reveals a brittle fracture site for Alumide and a ductile fracture with longitudinal splitting zones for PA2200. From the orientation point of view, similar properties of samples oriented at 0 and 90 degrees for all investigated mechanical properties were observed. However, tensile strength was less influenced by the sample orientations

A Magyar Cukor Zrt. Kaposvári Cukorgyára, mint alsó küszöbértékű veszélyes üzem bemutatása iparbiztonsági szempontok alapján

NemBibliogr.: fol. 61-62.Ne

Nondestructive Evaluation of Aluminium Foam Panels Subjected to Impact Loading

Aluminium foam sandwich structures have excellent energy absorption capacity, combined with good mechanical properties and low density. Some of the authors of this paper proposed an innovative Metallic Foam Shell protective device against flying ballast impact damage in railway axles. A closed-cell aluminium foam was chosen for the Metallic Foam Shell device. The main goal of this study was the experimental investigation of the impact responses of aluminium foam panels. Low velocity impact tests were carried out at different energies on different types of aluminium foam panels in order to investigate the effects of some parameters, such as core thickness, skin material and layer. Tests were conducted at repeated impacts on aluminium foam panels without and with skins made of aluminium and glass fibre-reinforced polymer. The experimental results were compared and the impacted panels were investigated by means of the nondestructive techniques ultrasonic phased array and digital radiography