Gábor Béres

• Doctor of Engineering
• Assistant Professor at John von Neumann University

This study presents the results of finite element simulations based on different variations of the flow curve of DC04 automotive thin sheet. The aim of our research is to investigate how different flow curve equations affect the variation of sheet thickness in cup drawing tests. In order to exclude other influencing factors in the experiment, both...

This study presents the experimental results of layer-compression tests in plane strain state as well as the role of the obtained parameters on the simulated thinning tendency of a cylindrical deep drawn part. The work hardening law has a special importance in numerical simulations, thus it is mostly expected to be known over a large range of defor...

In sheet metal forming operations, the most common forms of failure are tearing and wrinkling. The challenge in technology design is to predict and prevent these failure modes. In the field of rupture failure, a lot of research has been carried out in order to correctly and accurately define the so-called FLC curves. In this paper, we investigate h...

In this study, finite element method was used to study the effects of various notch geometries on the strain field distributions during the plane strain tensile test for cold-rolled steel (DC01). The artificial neural network approach (ANN) and the response surface methodology (RSM) were adopted to develop the mathematical prediction models applied...

Ez a tanulmány egytengelyű nyomóvizsgálat eredményeit mutatja be a DC04 autóipari vékonylemez folyásgörbéjének meghatározására. A folyásgörbe meghatározásának általános módszere a szakítóvizsgálat, amely a kontrakció jelensége miatt nem megbízható nagy alakváltozások esetén. Ezért nyomóvizsgálatot alkalmaztunk, amely két-három nagyságrenddel nagyob...

A leggyakoribb tönkremeneteli módok a lemezalakításban az elvékonyodás, a szakadás és a ráncosodás. A tervezési fázisban éppen ezért igyekszünk ezen tönkremeneteleket megakadályozni. Az elvékonyodás és a szakadás jelenségére számos elmélet született, amely törekszik arra, hogy minél pontosabb alakváltozási határértékeket fogalmazzon meg, ellenben a...

Material prediction behavior in the sheet metal forming operations is one of the critical fields of this process, especially for the industry and sheet metal forming processes in more precisely. Knowing the material behavior is a must to ensure the accuracy during the prediction for the best final size and shape. In this work we made a numerical in...

The Lankford number (i.e. r-value) has long been used as a key parameter in the science of sheet metal forming, for the mathematical description of plasticity. The traditional way of thinking is that this value is a constant in a given direction, and the definition is recommended at Ag-1 % plastic strain. In this study we focused on the evolution t...

Springback is one of the major defects that continuously concerns the sheet metal experts’ community. It is has long been known that the sheet thickness, the bending angle and the yield stress of the material primarily affect the angle change after the tools’ release. Besides, the consideration of the kinematic hardening ( KH ) model has powerful i...

Automobile industry those days reached a level of development very high. Especially in steel families with new grades that have a high combination of strength and formability. The reason behind this is the market and the demand for minimizing the fuel economy, decreasing in harming substance outflows, and improve safety precautions. To ensure the a...

Cikkünkben egy, a lemezalkatrészeket gyártó és kutató szakembereket erőteljesen foglalkoztató probléma, a mélyhúzás során fellépő lokális elvékonyodás jelenségének kísérleti és szimulációs eredményeit mutatjuk be. Az alkalmazott lemezanyagok a járműiparban elterjedten használatos DP600 és DP1000 nagyszilárdságú acélok voltak. Kísérleteinkből az vál...

In the current paper, specimen notch geometries during plane strain tensile test for cold-rolled steel DC01 is studied and optimized using Response Surface Methodology (RSM) and the desirability approach. The notch angle (X°), notch width (d), and notch length (c) were the main geometry parameters considered in this study. The effects of these para...

In the present work, optimization of near plane strain tensile test specimen for four types of cold-rolled steel DC01, DC04, DP600, and DP1000 are studied using finite element code ABAQUS. The sample width (A), notch radius (R), and material anisotropy (r-value) were the main parameters considered in this study. The effects of these parameters on t...

Cikkünk a korszerű lemezalakító technológiák egyik fontos elméleti (de a szimulációs programokon keresztül közvetlen gyakorlati hasznosulással is bíró) kérdéséről, az anyag képlékeny viselkedését leíró változók közül kiemelten az r-érték kutatásáról számol be. Régóta ismert tény, hogy a lemezek alakításánál kulcsszerepet játszik az elvékonyodási ha...

In recent years, the demand for a reduction in pollutant emission has become extremely important in the vehicle industry. It can be achieved through fuel consumption reduction, which is a direct function of the vehicle’s weight. nowadays weight is widely controlled by the use of advanced- and ultra-high strength steels (AHSS and UHSS) in vehicle bo...

Az utóbbi években rendkívüli módon megnőtt a járművek tömegének, üzemanyag-fogyasztásának és károsanyag-kibocsátásának csökkentési igénye a járműiparban. E törekvések többek között az újonnan kifejlesztett nagy és különlegesen nagy szilárdságú acéllemezeknek a járműkarosszéria-építésben történő alkalmazása révén jutnak érvényre. Ezeknek az anyagokn...

This paper aims to investigate different filling methods of ex situ aluminium foam-filled thin-walled Al alloy tubes to determine the best option for possible applications in automotive industry. The main applied filling methods were joining with heat dilatation, mechanical compression and adhesive bonding. Foam specimens were prepared by shaping a...

This study presents the experimental results and the comparison of different analytical models for springback evaluation of bent thin sheets. Three types of advanced high strength steels (from the group of dual phase steels, namely DP600, DP800 and DP1000) and a mild steel (DC04) were used to investigate the sheet profile after rectangular V-die be...

This study presents theoretical methods and experimental investigations for prediction on the flange wrinkling of deep drawn cylindrical cups. The prevention of wrinkling in the flange area is most commonly solved by a blank holder. The appropriate suppress of wrinkling is only possible with optimal process parameters, since inadequate blank holder...

This study is about using of the least squares’ method for parameter defining and model accuracy investigation of mechanical-based work-hardening laws of automotive dual phase steels. The experimental true stress true strain curves were determined by standard, quasi-static tensile tests at room temperature. As most of the commercial finite element...

Abstract. Forming limit diagrams (FLDs) are generally used to reflect the strain limits of sheet metal materials. These diagrams contain essential information for planning of high series stamping processes, however the experimental definition is still a difficult and time-consuming procedure. Five or more samples are needed to cover the different s...

This study is about the effect of the martensite volume fraction and indentation load on microhardness profiles of dissimilar types Dual Phase steels and DC04 mild steel. Experimental investigations were performed by mickrovickers method with using of eight different indentation loads from 0.01 kp up to 1 kp. Besides, microscope and tensile tests w...

Forming limit is a complex concept of limit values related to the onset of local necking in the sheet metal. In cold sheet metal forming, major and minor limit strains are influenced by the sheet thickness, strain path (deformation history) as well as material parameters and microstructure. Forming Limit Curves are plotted in ε1 – ε2 coordinate sys...

The importance of dual phase (DP) steels in the automotive industry was continuously spreading in the last decade. With their special microstructure—containing ferrite and martensite in particular ratio—high strength and increased formability is available. That’s the reason why the application of DP steels is providing to exceed the 50% in a modern...

One of the main aims of automotive developers is vehicle weight reduction. There are many well known ways related to weight reduction, for example using thinner and higher strength sheet materials, or using of formed tubes as load-bearing elements in car body structures. In the field of modern automotive industry we must not forget that the heavy l...

A nagy szériában végezett lemezalakításoknál, mint a járműkarosszéria-gyártásnál, a jól optimalizált folyamatok teszik lehetővé a termelékeny és minőségi alkatrész előállítást. Az utóbbi pár évtizedben megjelentek a karosszériagyártásban az új szerkezeti anyagok, az új tervezési és gyártási filozófiának köszönhetően. Egyre több gyártó alkalmaz növe...

A tudomány fejlődésével a mindennapi életünkben használt anyagokról egyre több információt ismerhetünk meg. Egyes fémekből és ötvözeteikből új felhasználási területen hasznosítható alkatrészeket állítanak elő. Azért, hogy ezeknek a területeknek megfelelő különleges tulajdonságokat ki tudják mérni, a konvencionális mérési eljárásoktól esetlegesen el...

The noise phenomenon of automated arc welding processes can cause noticeable imperfections during the manufacturing. Most of these imperfections can be derived from the difference of the pre-programmed robot path and the actual joint, incorrect metal transfer or arc. Many post-welding material test method exist to ensure the quality of the join...

The aim of automotive materials’ developers is to reduce car’s weight, and increase the energy absorption at the same time. Possibilities to decrease the weight of car body structures, seems to be using of higher strength steels, and formed tubes as parts of the loaded elements. The manufacturing of tubes, with constantly variable cross-sections...

The aim of automotive materials' developers is to reduce car's weight, and increase the energy absorption at the same time. Possibilities to decrease the weight of car body structures, seems to be using of higher strength steels, and formed tubes as parts of the loaded elements. The manufacturing of tubes, with constantly variable cross-sections al...

Clinching is a mechanical cold forming method to join two or more overlapping sheets without using of rivet. This technology is already in use for production of aluminium and steel sheet car body panels. This process is carried out without heat effect on the material structure. Thus the clinching is one of the technologies which may replace traditi...

This study is about the structural transformations of aluminium examining with the Dynamic Mechanical Thermal Analyzer (DMTA). It is a faster and simpler measuring method to make consequence about the metal's structural transformations. The device measures the changing of the mechanical characteristics depending on the heating rate, and concludes c...

The aim of this research is the examination of the DMTA technique to measure the phase transition temperatures of shape memory alloys. These parameters are difficult to detect by traditional material testing techniques, meanwhile quick and reliable results can be provided by DMTA measurements.

The researcher work pushes the borders of the application of a high efficiency equipment, in the matter of metals. With this equipment, which already testified in the compound industry, a flasher query of some metal-related technological parameters could be easily available. Towards the searching, we shaped different compound copper-alloy samples,...

The researcher work pushes the borders of the application of a high efficiency equipment, in the matter of metals. With this equipment, which already testified in the compound industry, a flasher query of some metal-related technological parameters could be easily available. Towards the searching, we shaped different compound copper-alloy samples,...

The aim of automotive materials' developers is to reduce car's weight, and increase the energy absorption at the same time. Possibilities to decrease the weight of car body structures, seems to be using of higher strength steels, and formed tubes as parts of the loaded elements. The manufacturing of tubes, with constantly variable cross-sections al...