Dóra Harangozó

57210445164

Publications - 13

Field Application of Austenitic Filler Metals for Repairing Rail Surface Defects in Paved Tracks

Szabolcs Fischer Mykola Sysyn Dmytro Kurhan Dóra Harangozó András Brautigam

Publication Name: Lecture Notes in Networks and Systems

Publication Date: 2025-01-01

Volume: 1258 LNNS

Issue: Unknown

Page Range: 87-95

Description:

Previous research by the authors identified a welding technology to repair rail defects in tramways with partial disassembly and partial preheating, with the following main advantages for the operator: the process can be carried out during operational downtime or even during traffic, disassembly, and repair costs are reduced, and traffic disruption is reduced compared to conventional hard surfacing welding technologies. After welding, the hardening under traffic should approach the vehicle wheels’ hardness values (310–350 HB). In the track measurements under investigation, welds were made on two different rail grades using austenitic weld metal with high elongation relative to the rails, which was also compared with welds made by conventional hard surfacing welding. The present study aims to determine the hardening function of austenitic dowel bars at different layer counts by performing continuous hardness measurements at the investigated sites. The hardening shows a power function at the initial stage and a linear trend after about 2.5 million MGT.

Open Access: Yes

DOI: 10.1007/978-3-031-81799-1_9

INVESTIGATION OF HEAT-AFFECTED ZONES OF THERMITE RAIL WELDINGS

Szabolcs Fischer Mykola Sysyn Dmytro Kurhan B. Kocsis Dóra Harangozó Dalma Németh András Brautigam

Publication Name: Facta Universitatis Series Mechanical Engineering

Publication Date: 2024-12-01

Volume: 22

Issue: 4

Page Range: 689-710

Description:

The paper investigates the heat-affected zone (HAZ) of several rail joints executed by thermite rail welding (TW). The examined rail profile was 54E1 (UIC54). The rail steel categories were different: R260 and R400HT. The welding portions of the TWs fitted R350HT and R260 rail categories with normal welding gaps. The rail pieces were brand new, i.e., without any usage in the railway track. The authors executed Vickers-hardness tests (HV10) and material texture tests on the running surface of the rail head, as well as on slices cut from the rail head. The cutting was performed by the water jet method, five longitudinal direction slices with vertical cutting lines. The considered specimen lengths were 2×70 mm (i.e., 70 mm from the mid-point of the rail joint), however, the depths were 20 mm from the running surface. Therefore, the measuring spaces were 5 mm lengthwise and 2 mm in depth. The variation of the hardness values was determined considering the microstructures of the base steel material and the TW. For comparison, previously measured Elektrothermit SoW-5 and earlier own research were taken into consideration.

Open Access: Yes

DOI: 10.22190/fume221217008f

Application of artificial neural networks for characterisation of formability properties of sheet metals

Dóra Harangozó I. Czinege

Publication Name: International Journal of Lightweight Materials and Manufacture

Publication Date: 2024-01-01

Volume: 7

Issue: 1

Page Range: 37-44

Description:

Artificial neural network models were developed to estimate forming limit diagrams from tensile test results based on our own experiments and data from the literature for steel and aluminium sheet metals. Experimental data were obtained from tensile tests and Nakazima tests. The input parameters used in the models were yield strength, ultimate tensile strength, uniform elongation, elongation at fracture, anisotropy coefficient and hardening exponent or combinations of these. The forming limit curves were defined by the measured minor and major strains using seven standard test specimens. After training the artificial neural network, the difference between measured and predicted results was evaluated by linear regression parameters and by the absolute errors. For steel sheet data taken from the literature, the estimated outputs of ANN models were compared with the results of empirical formulae developed by different authors. It was found that there was a high correlation coefficient between predicted and measured values for models using neural networks, which gave better approximations than other linear and non-linear models.

Open Access: Yes

DOI: 10.1016/j.ijlmm.2023.08.003

Comparative Evaluation of Forming Limit Curve Models for AlMg Alloys †

Dóra Harangozó I. Czinege

Publication Name: Engineering Proceedings

Publication Date: 2024-01-01

Volume: 79

Issue: 1

Page Range: Unknown

Description:

This publication deals with the comparative analysis of theoretical and empirical models suitable for predicting forming limit curves in the case of aluminum–magnesium alloys. The Stören–Rice and Hill–Bressan–Williams equations were evaluated and justified by inverse parameter identification. They showed good agreement with the measured strain values. Using the graphical Modified Maximum Force Criterion, it was demonstrated that the Voce hardening law is more suitable than the Swift one for characterizing this group of alloys, but the weighted combination of the two hardening laws is preferable.

Open Access: Yes

DOI: 10.3390/engproc2024079005

Effect of Roller Levelling on Tensile Properties of Aluminum Sheets

Dóra Harangozó I. Czinege

Publication Name: Materials

Publication Date: 2023-04-01

Volume: 16

Issue: 8

Page Range: Unknown

Description:

The straightening of sheets, bars and profiles plays an important role in many machining processes. The aim of sheet straightening in the rolling mill is to ensure that the deviation of sheets from flatness is within the tolerances specified in the standards or delivery conditions. There is a wide range of information available on the roller levelling process used to meet these quality requirements. However, little attention has been paid to the effects of levelling, namely the change in properties of the sheets before and after roller levelling. The aim of the present publication is to investigate how the levelling process affects tensile test results. The experiments have shown that levelling increases the yield strength of the sheet by 14–18%, while it decreases its elongation by 1–3% and hardening exponent by 15%. The mechanical model developed allows changes to be predicted, so that a plan can be made regarding roller levelling technology that has the least effect on the properties of the sheet while maintaining the desired dimensional accuracy.

Open Access: Yes

DOI: 10.3390/ma16083001

Numerical Investigation of Pre-Stressed Reinforced Concrete Railway Sleeper for High-Speed Application

Szabolcs Fischer Zoltán Major Szabolcs Szalai Mykola Sysyn Attila Németh Dmytro Kurhan Dóra Harangozó M. Movahedi Rad Sarah Khaleel Ibrahim Dániel Harrach Szabolcs Kocsis Szurke Gusztáv Baranyai Géza Herczeg L. Gaspar

Publication Name: Infrastructures

Publication Date: 2023-03-01

Volume: 8

Issue: 3

Page Range: Unknown

Description:

The current paper deals with the numerical investigation of a unique designed pre-stressed reinforced concrete railway sleeper for the design speed of 300 km/h, as well as an axle load of 180 kN. The authors applied different methodologies in their research: traditional hand-made calculations and two types of finite element software. The latter were AxisVM and ABAQUS, respectively. During the calculations, the prestressing loss was not considered. The results from the three methods were compared with each other. The hand-made calculations and the finite element modeling executed by AxisVM software are adequate for determining the mechanical inner forces of the sleeper; however, ABAQUS is appropriate for consideration of enhanced and sophisticated material models, as well as the stress-state of the elements, i.e., concrete, pre-stressed tendons, etc. The authors certified the applicability of these methodologies for performing the dimensioning and design of reinforced concrete railway sleepers with pre-stressing technology. The research team would like to continue their research in an improved manner, taking into consideration real laboratory tests and validating the results from FE modeling, special material models that allow calculation of crackings and their effects in the concrete, and so that the real pattern of the crackings can be measured by GOM Digital Image Correlation (DIC) technology, etc.

Open Access: Yes

DOI: 10.3390/infrastructures8030041

Investigation of deformations of a lithium polymer cell using the Digital Image Correlation Method (DICM)

Szabolcs Fischer Szabolcs Szalai Dóra Harangozó Szabolcs Kocsis Szurke

Publication Name: Reports in Mechanical Engineering

Publication Date: 2022-01-01

Volume: 3

Issue: 1

Page Range: 116-134

Description:

This research aims to investigate the adaptability of a measurement system or a process in determining the parameters of batteries. Methods are suggested for different applications, and properties gained by these measurements are specified. Deformations of lithium polymer batteries measured by various methodologies are also analyzed in detail. Changes in the geometry of worn-out batteries and the localization of the changes can be better understood by applying the results. The GOM ATOS and the GOM ARAMIS systems were applied to characterize lithium polymer batteries. Discontinuous tests were performed and the battery was discharged to 0 V and then fully charged for both methods. The advantages and disadvantages and the applicability of the two measurement systems were analyzed in this topic.

Open Access: Yes

DOI: 10.31181/rme20008022022s

Investigation of the Effects of Thermit Welding on the Mechanical Properties of the Rails

Szabolcs Fischer B. Kocsis Dóra Harangozó Vivien Barna András Brautigam

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2022-01-01

Volume: 19

Issue: 3

Page Range: 37-49

Description:

This current paper deals with the investigation of the variation of the hardness of the rail steel material in the heat-affected zone (HAZ) of a rail joint made by thermit welding (TW). The tested rail is a normal R260 type rail steel category; its production date is 1977, the rolling mill was Diosgyor (Hungary), rail profile is MÁV 48.5. This rail has not been in railway track before the test. The authors performed hardness tests on the rail head’s surface even after the rail welding, as well. After the welding and hardness tests, the rail joint was cut with +/–200 mm by a rail cutter and transported to the laboratory. Water jet cutting was applied to shape six longitudinal direction slices with five vertical cutting lines from the rail piece’s head. The slices’ length was 400 mm, the width of these slices was approx. 10 mm; the TW rail joint was in the mid-point of the slices. Micro-Vickers (HV10) hardness tests were executed on these slices, in the –150…+150 mm interval lengthwise and in the 3, 6, and 10 mm depth points below the rail head’s top surface. As a result, the authors received a very detailed hardness functions of the HAZ of rail joint made by TW. These variation functions were compared to the official Elektrothermit’s SoW-5 hardness tests’ results. It can be concluded that the variation of the hardness of rail steel in the area of the HAZ correlated with the Elektrothermit’s results; however, there were some critical points where significant differences were able to be found. The highest deviation was concluded in 50 mm distance measured from the axis of welded rail joint. The authors gave possible valuable explanations for these phenomena.

Open Access: Yes

DOI: DOI not available

Characterisation of Inhomogeneous Plastic Deformation of AlMg Sheet Metals during Tensile Tests

Szabolcs Szalai Dóra Harangozó I. Czinege

Publication Name: Iop Conference Series Materials Science and Engineering

Publication Date: 2020-08-25

Volume: 903

Issue: 1

Page Range: Unknown

Description:

The Portrevin-Le-Chatelier (PLC) effect was analysed quantitatively in the selected AlMg alloys with Mg-content between 2,8-4,6%. The propagation and characteristics of PLC bands were detected by digital image correlation (DIC) technique and the parameters of the bands were evaluated from strain distributions of tensile test specimens. In parallel, stress-strain curves were analysed evaluating stress serrations. The numerically defined parameters of changes in stress and strain were used for characterising the PLC effect on the behaviour of different sheet metals. General statements of literature were numerically proven for the tested materials and the effect of magnesium content on stress amplitude was analysed in detail.

Open Access: Yes

DOI: 10.1088/1757-899X/903/1/012023

Experimental and numerical investigation of the single-point incremental forming of aluminium alloy foils

Imre Paniti Sherwan Mohammed Najm Dóra Harangozó Zsolt János Viharos

Publication Name: Acta Imeko

Publication Date: 2020-03-01

Volume: 9

Issue: 1

Page Range: 25-31

Description:

Single-Point Incremental Forming (SPIF) is a flexible process for manufacturing sheet metal parts that is well adapted and profitable for prototypes or small batch production. Compared to traditional sheet forming technologies, this relatively slow process can be used in different applications in the automotive and aircraft industries; architecture engineering; and medical aid manufacture. In this article, the indirectly obtained axial forming force on the SPIF of variable wall angle geometry is studied using different process parameters. The estimation of the forces on AlMn1Mg1 sheets with an initial thickness of 0.22 mm is performed by continuous monitoring of servomotor currents. The deformation states of the formed parts were analysed using the ARGUS optical strain measurement system of GOM, while the roughness measurements were carried out by a Mitutoyo system. Some initial finite element analysis simulations and a crack monitoring method together with an interaction plot of forming speed, incremental depth, tool diameter, and lubrication were also reported.

Open Access: Yes

DOI: DOI not available

Influence of local porosity on the mechanical properties of direct metal laser-sintered 1.2709 alloy

I. Fekete István Hatos Dóra Harangozó H. Hargitai

Publication Name: Strojniski Vestnik Journal of Mechanical Engineering

Publication Date: 2020-01-01

Volume: 66

Issue: 6

Page Range: 351-357

Description:

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.

Open Access: Yes

DOI: 10.5545/sv-jme.2020.6573

Displacement-based failure analysis of metal matrix syntactic foam

I. Zsoldos I. Kozma Dóra Harangozó H. Hargitai

Publication Name: Wit Transactions on Engineering Sciences

Publication Date: 2019-01-01

Volume: 124

Issue: Unknown

Page Range: 161-173

Description:

Metal matrix syntactic foams are being used more and more widely thanks to their relative density as well as their perfect energy-absorbing characteristics. Multiple studies concern the economical production of these materials – particularly, how energy absorption as a physical characteristic can be increased. Many studies examined the effects of material choice as well as cell size and wall thickness of reinforcing materials on compressive strength. However, there are only estimated models about descriptions concerning decaying processes of samples from different material composition and geometrical variation. In this study, we introduced an “in situ” examination in order to model the decaying process. We upsetted aluminium-ceramic composite foams cyclically. We reconstructed the geometry of the sample with microcomputed tomography (μCT) technology and digital image processing at certain specified points of the compression test. During the complete decaying process, the process was evaluated with volume change and number of broken hollow particles, as well as elementary particle displacements, orientation and sphericity of the reinforced material.

Open Access: Yes

DOI: 10.2495/MC190161

Experimental investigation of single point incremental forming of aluminium alloy foils

Imre Paniti Dóra Harangozó Zsolt János Viharos

Publication Name: 16th Imeko Tc10 Conference 2019 Amp Amp Amp Amp Amp Quot Testing Diagnostics and Inspection as A Comprehensive Value Chain for Quality and Safety Amp Amp Amp Amp Amp Quot

Publication Date: 2019-01-01

Volume: Unknown

Issue: Unknown

Page Range: 50-55

Description:

Incremental Sheet Forming is a prosperous process to manufacture sheet metal parts that is well adapted for prototypes or small batch production. Compared to traditional sheet forming technologies this relatively slow process is only profitable for the above mentioned production types but it can be used in different applications in automotive and aircraft industries, in architecture engineering and in medical aids manufacturing. In this paper indirectly obtained axial forming force on Single Point Incremental Forming (SPIF) of variable wall angle geometry were studied under different process parameters. The estimation of the forces on AlMn1Mg1 sheets with 0.22 mm initial thickness is performed by continuous monitoring of servo motor currents. The deformation states of the formed parts were analysed using the ARGUS optical strain measurement system of GOM. Interaction plot of forming speed, incremental depth, tool diameter and lubrication were also reported.

Open Access: Yes

DOI: DOI not available