No abstract

Purpose. It is a very important issue to be able to determine the accurate particle degradation of railway ballast material. There are three differentbut connectingmethodology for that: 1) full scale field tests, 2) full scale or reduced scale laboratory tests, 3) computer modelling, mainly with discrete element method (DEM). Options no. 1 and no. 2 need a lot of time and money, but for option no. 3 sophisticated software is needed that can consider the accurate micromechanical characteristics of ballast bed material. Methodology. In this paper the authors summarize their results related to modelling, having applied a software that uses DEM for calculation, as well as laboratory tests, namely uniaxial compression tests with reduced scale and computer tomography. Findings. The authors obtained the results that the uniaxial compression test in laboratory was able to be modelled by DEM software with an initial precision but in the future should be specified. The results are certified by measurements performed by computer tomography method. Originality. It is a very complicated issue to model the particle breakage of railway ballast not only particle movements in DEM software. There are many available software packages at the 'market', e.g. PFC, EDEM, YADE. Some of them are quite expensive, the others can be controlled by significantly difficult manner (special programming technique is needed, command line, etc.) The authors applied not only laboratory loading tests, but sophisticated computer tomography for their research. Practical value The results can be useful for railway engineering area. This article is a part of a PhD research at Szechenyi Istvan University, the PhD student is Erika Juhász. Her aim is to develop a method to be able to determine the more accurate ballast breakage, as well as develop assessment methodology related to special measurement techniques (e.g. GOM techniques, computer tomography, etc.). The publishing of this paper was supported by ÚNKP-19-3-I-SZE-13 project.

Powder bed metal printing has demonstrated its potential for the direct manufacturing of complex parts. It has great flexibility compared to conventional manufacturing. There are also some difficulties and problems, e.g., because the process stops during production. When the process is restarted, the first layer may be thicker due to technological limitations. In this paper, the effects caused by the presence of these thicker layers were investigated. The possibility of re-melting the layers to reduce porosity were also analysed. A tool steel powder grade 1.2709 was used to produce samples with an increased thickness of melted layers.

No abstract

The current paper concerns the investigation of CC (Concrete Canvas), a unique building material from the GCCM (geosynthetic cementitious composite mat) product group. The material is suitable for trench lining, trench paving, or even military construction activities, while the authors’ purpose is to investigate the application of the material to road and railway substructure improvement. This research was carried out to verify the material’s suitability for transport infrastructure and its beneficial effects. The authors’ previous study reported that the primary measurements were puncture, compression, and the parameters evaluated in four-point bending (laboratory) tests. However, based on the results, finite element modeling was not feasible because the testing of the composite material in a single layer did not provide an accurate indication. For this reason, the material characteristics required for modeling were investigated. A unique, novel testing procedure and assembly were performed, wherein the material was loaded under quasi-realistic conditions with a crushed stone ballast sample and other continuous particle size distribution samples in a closed polyethylene tube. In addition, the deformation of the material following deformed bonding was measured by computed tomography scanning, and the results were evaluated.