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Found 6374 publications

Digital image analysis of sheet metal testing and forming

Szabolcs Szalai Imre Czinege

Publication Name: 15th Imeko Tc10 Workshop on Technical Diagnostics 2017 Technical Diagnostics in Cyber Physical Era

Publication Date: 2017-01-01

Volume: Unknown

Issue: Unknown

Page Range: 176-180

Description:

Digital image analysing methods are widely used for evaluating local deformations in sheet metal tests and forming processes. The paper is focusing on tensile tests of uniform and non-uniform width flat specimens made of aluminum alloys, which are suitable for demonstrating Löders strain, Portevin-Le Chatelier (PLC) effect and for determination of Forming Limit Curve. Tests were carried out using GOM-ARAMIS® digital image analysis hardware and software. Observation of local deformations during tensile tests showed that initiation and evolution of local strains depend on the position of specimens related to rolling direction of sheet. Using non-uniform width specimens the local deformations are concentrated on the smallest cross-section in the final stage of tensile test. The measured major and minor strains give points of FLC.

Open Access: Yes

DOI: DOI not available

Survey of free speeds on rural roads based on road scene photographs

Gabriella Kosztolányi-Iván

Publication Name: Pollack Periodica

Publication Date: 2012-04-01

Volume: 7

Issue: 1

Page Range: 65-74

Description:

In Hungary since 2008 some roads operate with posted speed limits, which are higher than the general 90 kmph outside urban areas. The goal of the current study was to explore how well road users can recognize various types of roads. The results show on one hand that on the usual road categories like motorways and normal two-lane primary roads the speed choice is clear for road users, i.e. these roads are self-explaining. On the other hand, there are also road categories, which are not self-explaining and therefore road users have difficulties to choose the appropriate speeds.

Open Access: Yes

DOI: 10.1556/Pollack.7.2012.1.6

Long-term safety trends as a function of vehicle ownership in 26 Countries

Csaba Koren Attila Borsos Nalini Ravishanker John N. Ivan

Publication Name: Transportation Research Record

Publication Date: 2012-01-12

Volume: Unknown

Issue: 2280

Page Range: 154-161

Description:

The objective of this paper was to model the evolution of road safety as a function of motorization level. The authors completed a country-level as well as a time-dependent analysis focusing on countries for which data were available for a long period of time (1965 to 2009). For the statistical analysis, a function describing road safety trends (decline, turning, improvement) was proposed. Two coefficients in the model were estimated for each country and for each year, and their change over time is discussed. The results showed that the shape of the curve changed over time. In some countries, the decrease in the mortality rate became slower over time; however, a greater potential to improve road safety existed in other countries. Possible reasons for the general positive trends in road safety are the continuous improvement in engineering solutions (better infrastructure, safer cars) as well as road users who are better trained and skilled because of education and experience. In addition to the factors mentioned previously, the increased speed by which safety-related information and knowledge are disseminated contributes to the decrease in the differences in safety levels among countries.

Open Access: Yes

DOI: 10.3141/2280-17

Traffic safety impacts of irregular overtaking in left-turn lanes at road intersections outside built-up areas

Dániel Miletics

Publication Name: Pollack Periodica

Publication Date: 2013-04-01

Volume: 8

Issue: 1

Page Range: 41-51

Description:

Overtaking is a high risk maneuver for road users, still drivers often accept this risk, moreover they often commit irregular overtaking maneuvers. The paper gives some overview on traffic violations and irregular overtaking maneuvers. Left-turn lanes on major roads are usual elements of un-signalized at-grade junctions on two-lane roads outside urban areas. In several cases the left-turn lane, built for safety reasons, has the unintended negative effect, of becoming a dangerous spot. The paper analyses overtaking maneuvers at left-turn lanes on Hungarian roads. Site surveys were completed at typical sites outside built-up areas. Relationships between the frequency of irregular maneuvers, accident statistics, geometric parameters and traffic data are analyzed.

Open Access: Yes

DOI: 10.1556/Pollack.8.2013.1.4

Investigating the Effect of Gear Ratio in the Case of Joint Multi-Objective Optimization of Electric Motor and Gearbox

György Istenes József Polák

Publication Name: Energies

Publication Date: 2024-03-01

Volume: 17

Issue: 5

Page Range: Unknown

Description:

In this paper, a software framework is presented through an application that is able to jointly optimize an electric motor and a gearbox for the design of a drive system for electric vehicles. The framework employs a global optimization method and uses both analytical and finite element method (FEM) models to evaluate the objective functions. The optimization process is supported by a statistical surrogate model, which allows a large reduction of runtime. An earlier version of this framework was only suitable for electric motor optimization. In the application presented in a previous paper, the motor of a belt-driven electric drive system was optimized. In this paper, the optimization of the same drive system is shown, but now with a combined optimization of a gear drive and motor. The objective functions of optimization are minimizing the total loss energy and the weight of the drive system. The optimization results are compared with previous results to demonstrate the further potential of joint optimization.

Open Access: Yes

DOI: 10.3390/en17051203

Influence of the loading condition on single grain crushing in DEM simulation

Saeed Safikhani Majid Movahedi Rad Erich Bauer

Publication Name: Periodica Polytechnica Civil Engineering

Publication Date: 2019-12-18

Volume: 63

Issue: 4

Page Range: 1152-1158

Description:

Grain crushing is of essential importance for understanding the mechanical behavior of granular materials such as sand, gravel or broken rock under higher pressures. In order to investigate the breakage mechanism of a single grain under different loading conditions, numerical simulations are carried out using DEM. Two different types of boundary conditions are considered to apply displacement-controlled load: loading using platens and loading by uncrushable macro-grains. A 2D crushable macro-grain is built up from a large number of micro-grains which are connected with respect to breakable parallel-bond properties. The response of the crushable macro-grain for different coordination numbers and location of the contact points is discussed. The numerical results show that the type of loading condition can influence the loading capacity and fragmentation patterns of the crushable macro-grain.

Open Access: Yes

DOI: 10.3311/PPci.14541

Change in Stiffness of Reinforced Concrete Tunnel Walls and Its Effect Under Fire Load

Edina Koch Éva Lublóy Zoltán Major

Publication Name: Advances in Transdisciplinary Engineering

Publication Date: 2024-01-01

Volume: 59

Issue: Unknown

Page Range: 342-350

Description:

This article uses the knowledge gained from tunnel fires to address the structural analysis of tunnel walls during fire exposure. The designing at normal temperature and its theoretical background are discussed in the literature. As these books did not yet deal with the issue of fire protection designing, we tried to supplement the existing theoretical knowledge with the knowledge provided by the relevant standards for reinforced concrete tunnel walls. In addition, we have tried to add our own individual ideas to the theory where we felt that there were gaps. The theoretical summary has been compiled in such a way that it can be easily transferred and applied to everyday practice. In this article, we discuss in detail the calculation of the internal forces in tunnel walls during fire exposure. Due to space constraints, the issue of designing at normal temperatures is only touched upon in this article, limiting it to the knowledge available in the literature. Since finite element modelling has become a commonly used technique in tunnel design since the 1970s, we use its potential to investigate the effects of earth pressure and surface loads on the tunnel walls during fire and their changes, using specific software for geotechnical design. In accordance with the limitations of the scope, the determination of the equivalent thickness and the modulus of elasticity of the tunnel wall is also presented in order to determine the internal forces during the fire action.

Open Access: Yes

DOI: 10.3233/ATDE240565

Decoupling – shifts in ecological footprint intensity of nations in the last decade

Cecilia Szigeti Daniel Robert Szabo Gergely Toth

Publication Name: Ecological Indicators

Publication Date: 2017-01-01

Volume: 72

Issue: Unknown

Page Range: 111-117

Description:

The ecological price of economic growth is a heavily debated issue, where ideologies often neglect factual information. In this paper, through the relationship of the ecological footprint and GDP, we examine the tendencies of eco-efficiency in the first decade of the 21st century. We conclude that the average ecological footprint intensity of countries have improved significantly in the given period. In 2009, 50 percent less area was needed to produce a unit of GDP. Many countries could reach the so-called strong decoupling − these countries could increase GDP while decreasing the ecological footprint in absolute terms. We also repeated the analysis of a scientific article published in 2004. We managed to update data and identify ecologically positive tendencies. In ten years, the average of the world's ecological footprint intensity has significantly improved, it halved all in all. We found that 90 percent of the countries started to move to the direction of sustainable development. Among the studied 131 countries, 40 experienced strong decoupling (absolute decrease of resource use), in 77 countries weak decoupling occurred (relative decrease of resource use), and there were only 14 countries, where no decoupling could be observed (relative increase of resource use).

Open Access: Yes

DOI: 10.1016/j.ecolind.2016.07.034

A Preliminary Study on Laser Surface Texturing of Passenger Car Engine Piston Rings

András Lajos Nagy Attila Schweighardt Gabor Laki Gergely Kovács

Publication Name: Fme Transactions

Publication Date: 2025-01-01

Volume: 53

Issue: 2

Page Range: 252-259

Description:

Laser surface texturing offers a possible solution for reducing friction between sliding surfaces in engineering applications. Optimized surface topography can also contribute to reduced wear and elevated longevity by modifying the load and speed-dependent friction state in a system. This preliminaryexperimental study investigates the applicability of affordable fibre laser marking systems for microtexturing piston rings, in order to achieve a measurable reduction in friction under subsystem model conditions. A selection of textures are applied to chromium-coated cast iron piston rings. The resulting surface topographies are characterized through confocal microscopy and subjected to friction testing. A correlation analysis is conducted on surface topography parameters to identify key laser process parameters. Findings indicate an improvement in the range of 7–8% in terms of friction coefficient with appropriate texture size.

Open Access: Yes

DOI: 10.5937/fme2502252L