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1
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Determining Springback Behavior of High-Strength Steels via Channel Forming Process

100%
Esener E., Sönmez E., Özsoy M., Firat M.
Acta Physica Polonica A
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2017
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vol. 132
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issue 3
1010-1012
EN
The increasing use of high-strength steels in sheet metal automotive parts usually brings about the springback problems that can not be easily solved, compared to stamping the parts of conventional steel grades. Prediction and compensation of springback at the design stage is very important from both, the academic and the industrial perspectives. For this purpose, finite element analysis and simulative tests are used to understand formability properties of the material. In this study, springback behaviour of high-strength steels was investigated. Angular channel forming process is used as a simulative test with the DP600, DP1000, and DP1400 materials. Channel forming die tools were designed using a shallowly curved geometry for investigating springback behaviour of materials. Die tools were manufactured and forming process was performed at a hydraulic press machine. Sample surfaces were scanned using optical scanning. Then, experimental springback surfaces were compared with reference geometry by shape deviation analysis. It is observed that springback amount of DP1400 is much greater than those of DP600 and DP800 steels. The DP600 steel has minimum springback amount in the flange region and it has shown the smallest deviation from the reference forming surface, as a result of shape deviation analysis.
2
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A Simulation and Fabrication Works on Optimization of High Pressure Aluminum Die Casting Part

100%
Ertürk S., Kumruoğlu L., Özel A.
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vol. 125
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issue 2
449-451
EN
High-pressure die casting offers reduced costs due to its small tolerances and smooth surface finish. Casting parts produced are consumed by the automotive industry in millions. In this study, the use of computer aided engineering applications on design of high-pressure die-casting was studied. The influence of casting process steps in die design was studied and analyzed. The casting simulation software was used to improve design and solve problems. By using the simulation software in analyses of die design, the final design was reached in a few hours and thus the design process of pre-production was shortened and mold production was carried out with no revision on die material. Radiographic test was applied on the casting parts and the result shows good correlation between simulations of solidification result data. Also the results proved that the application of squeeze pressure in the intensification phase of high-pressure die casting process could be examined in the casting simulation.
3
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Mechanical Properties Enhancement of Particle Reinforced Magnesium Matrix Composites Used for Hot Extruded Tubes

80%
Huang S., Hwang Y., Huang Y., Huang C.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
1271-1273
EN
This paper studies new magnesium metal matrix composites (Mg MMCs) reinforced with SiC particles by the stir-casting method for MMCs tubes hot extrusion. AZ61/SiCp MMCs' ingots reinforced with 0, 0.5 and 1 wt.% SiC particles are fabricated by the melt-stirring technique. AZ61/SiCp MMCs' tubes are manufactured by hot extrusion using a specially designed die-set. Obvious grain size refinement both by addition of particles and extrusion process are discovered. However, the grain refinement effect caused by extrusion process is much significant than that effect caused by SiC particle addition. The 0.2% yield strength (YS) of extruded tubes of AZ61 and AZ61/1 wt.% SiCp MMCs (without and with T5 treatment) are increased by 140.9-161.9% and 156.5-156.7%, respectively, compared with those of as-cast billets.
4
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Porous Ceramic Supports for Membranes Prepared from Kaolin (DD3) and Calcite Mixtures

80%
Harabi A., Boudaira B., Bouzerara F., Foughali L., Zenikheri F., Guechi A., Ghouil B., Condom S.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
1164-1166
EN
The supports for microfiltration (MF) and ultrafiltration (UF) were prepared with local kaolin (Djebel Debagh: type 3: DD3) and calcium carbonate (CaCO₃) mixtures. The choice of these materials is based on their natural abundance (low price). In this work, the tubular ceramic supports were prepared by the extrusion method. The sintering was carried out for 2 hours, at temperatures laying between 1150 and 1300°C. They are then characterized by various techniques: mercury porosimetry, scanning electron microscopy and x-ray diffraction. The obtained results revealed that the main phase formed during the sintering step was anorthite with a minor phase of mullite. Moreover, it has been found that supports sintered at temperatures less than 1300°C had interesting characteristics; an average pore size ranged between 3.91-8.56 μm, a porosity ratio of 42.0-50.4%, a flexural strength ≈67-77 MPa and the pore size distribution is bimodal type. According to their average pore sizes, they may be used either as supports for MF or UF membranes.
5
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Effect of Temperature on Grain Refinement of Mg-3Al-1Zn Alloy Processed by Equal Channel Angular Pressing

80%
Molnár P., Jäger A., Lejček P.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
461-464
EN
In this work the effect of temperature on grain refinement of Mg-3Al-1Zn alloy (AZ31B) processed by equal channel angular pressing using route A is described. The deformation sequences consisted of equal channel angular pressing passes at 200C followed by passes at 150°C. Nonhomogeneous grain size distribution promotes shear band formation at 150°C. Shear bands with microcracks inside were analyzed by electron backscatter diffraction technique.
6
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Prediction of Sheet Drawing Characteristics with Square Drawbead Elements Using Response Surface Methodology

80%
Tiryaki A., Kozan R., Adar N.
Acta Physica Polonica A
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2015
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vol. 128
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issue 2B
B-344-B-347
EN
Drawbeads are often used in the sheet metal forming processes to provide a better control of the material flow into the die cavity. The drawbead restraint force (DBRF) and the exit thickness are two important sheet drawing characteristics to be determined for the selection and installation of the drawbead elements. This study presents the effects of drawbead geometry and sheet material on drawbead restraining force and thinning. Mathematical correlation between the drawbead geometry, sheet material and drawing characteristics was investigated by using Response Surface Methodology (RSM), which is a global approximation method ideally suited for solving highly nonlinear optimization problems. The proposed response surface model for DBRF and thinning showed a good correlation with the experimental data available in the literature. RSM could be considered as an alternative and practical technique to evaluate the sheet drawing characteristics. The method can also be applied to other sheet metal forming issue.
7
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Post SPD Material's Recovery in Thermal Exposition

80%
Kvačkaj T., Kováčová A., Kočiško R.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
689-692
EN
The mechanical and thermo-physical properties of Cu-Cr-Zr alloys in dependence on processing conditions were studied. The processing conditions consisted of solution annealing at temperature of 1020°C for 60 min followed by water quenching. This was followed by one equal channel angular pressing pass carried out at ambient temperature, ageing treatment (T_{AT}∈ (20;480⟩°C, t_{AT}∈ ⟨30;150⟩ min) and cooling in water. The maximal strengthening effect coming from dislocations & grain size refinement & precipitation strengthening of ΔHV0.1=130 was achieved at T_{AT}=480°C and for t_{AT}=120 min. From differential scanning calorimetry analysis, two partial exothermal peaks were recognized and classified as major and minor, these peaks are used to determination the stored energy coming from recrystallization and precipitation (ΔH_R and ΔH_P). The maximal value in stored energy of H_{1×ECAP}=2.923 J/g was obtained after 1st ECAP pass.
8
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Digital Fabrication of Mathematical Models via Low-Cost 3D FDM Desktop Printer

80%
Gür Y.
Acta Physica Polonica A
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2015
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vol. 128
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issue 2B
B-100-B-102
EN
Additive manufacturing technology is developed throughout the 1980's and 1990's. This technology makes the realization of mathematical models much easier. The challenge focused is here to fabricate real objects from very complex mathematical models by using a low-cost 3D fused deposition modeling desktop printer. Thus this brings the intangible mathematical expressions to life. In this study it is illustrated that complex mathematical expressions are not only numbers and symbols but also they are real life objects. In the examples, some mathematical functions such as Möbius strip, Schwartz functions and their boundary conditions are introduced and then digitally fabricated. This work shows that how complex functional mathematical models that cannot be manufactured with classical engineering methods or very difficult to produce can be fabricated by using a 3D FDM desktop printer.
9
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Developing Superplasticity in Ultrafine-Grained Metals

80%
Kawasaki M., Langdon T.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
470-478
EN
The processing of bulk metals through the application of severe plastic deformation provides an opportunity for achieving exceptional grain refinement with grain sizes typically lying in the submicrometer or even the nanometer range. Provided these small grains are reasonably stable at elevated temperatures, these ultrafine-grained metals will exhibit excellent superplastic properties when pulled in tension at elevated temperatures. Most ultrafine-grained materials have been produced using either equal-channel angular pressing or high-pressure torsion. This paper examines the results for superplasticity reported to date using metallic alloys processed by equal-channel angular pressing and high-pressure torsion, compares the experimental strain rates with those predicted using the theoretical model for conventional superplastic flow and then demonstrates the feasibility of preparing deformation mechanism maps that provide comprehensive information on the flow mechanisms.
10
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Influence of Press Ram Pulsation on Deep Drawability of Dual Phase Steel Sheet

80%
Olguner S., Tolga Bozdana A.
Acta Physica Polonica A
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2017
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vol. 132
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issue 3
742-745
EN
A study of the influences of press ram pulsation on deep drawability of dual phase steel sheet is presented. General characteristics of deep drawing process, press ram pulsation technique and dual phase steels are briefly discussed. A finite element model is used to evaluate the influence of pulse motion profile of press ram on the thickness reduction of steel sheet and forming load. Commercial finite element software package DEFORM-3D is used for modelling and simulation of cylindrical cup drawing. The effects of superimposed low frequency vibrations of the press ram are investigated. Pulsation amplitudes of 0.5, 0.25, and 0.125 mm are created on the die with the corresponding pulsation frequencies of 5, 10, and 20 Hz. Finite element simulations are carried out using material model of dual phase (DP600) steel, that is one of the most widely used materials in automobile industry, in order to improve crash safety and fuel economy. Results obtained with press ram pulsation are compared with results for the conventional press ram motion and significant effect of proposed method is demonstrated.
11
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AccumEx - A New SPD Technique for Fabricating Lamellar Materials

80%
Muralidharan G., Verlinden B.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
523-526
EN
Accumulated extrusion is a novel plane strain compression technique, akin to the process of accumulated roll bonding, designed to produce ultrafine grained lamellar materials. AA1050 CP-Al processed by AccumEx displayed a grain refinement from 17 μm to 1.8 μm after 2 passes (equivalent strain of 3.2) with an increase in tensile strength of ≈70%. A comparative study with the conventional equal channel angular extrusion technique demonstrated that the former displayed a higher fraction of high angle grain boundaries with very similar trend of grain refinement. Up to now, extrusions up to 8 passes have been performed.
12
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Mechanical and Structural Properties of High Purity Al Processed by ECAP

80%
Kvačkaj T., Kočiško R., Pokorný I., Bidulská J., Kvačkaj M., Kováčová A., Bidulský R., Lityńska-Dobrzyńska L., Dutkiewicz J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
557-560
EN
The mechanical properties and substructure formation of high purity aluminium (99.999%) processed by severe plastic deformation method (equal channel angular pressing) were studied. The equal channel angular pressing process was carried out at room temperature by route C (sample rotation around the axis about 180° after each pass) in a die with two channels intersecting at an angle of Φp = 90. The softening mechanism through dynamic recovery was recognized up to 6th equal channel angular pressing pass, however, after that the mechanical strengthening was revealed. The samples after equal channel angular pressing processing were annealed in different temperature and time conditions. The influence of annealing temperature and time on microhardness as well as diameter of grain size were investigated in samples processed by the 4th equal channel angular pressing pass.
13
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Formability Evaluation of Aluminium Alloys by FLD Diagrams

70%
Petroušek P., Kočiško R., Kvačkaj T., Bidulský R., Bidulská J., Fedoriková A., Sabol P.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1344-1346
EN
The goal of the present work is evaluated mechanical properties and forming limit diagrams of ambient rolled aluminium alloy based on AlMgSi. Forming limit diagrams are convenient and often used as a tool for the classification of the formability and the evaluation of the forming process of sheet materials. Forming limits of sheet metal are represented in the forming limit diagrams occurring by various deformation states. The most widely used type is the Keeler-Goodwin diagram. Input data got from static tensile test are important for formability evaluating of the thin sheet by mathematical simulations, such as tensile strength, yield strength, elongation, and the strain hardening exponent. The result is a consideration of the suitability of the material for stamping technology.
14
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Prediction of Mechanical Properties of Cold Rolled Steel Using Genetic Expression Programming

70%
Kanca E., Çavdar F., Erşen M.
Acta Physica Polonica A
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2016
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vol. 130
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issue 1
365-369
EN
A new model was developed to predict the mechanical properties of St22 grade cold rolled deep drawing steel by gene expression programming. To obtain a dataset to find out the effect of reduction rate on the mechanical properties of cold rolled and galvanized steel sheet, an experimental program was constructed in the real production plant by keeping all other process parameters constant. The training and testing data sets of gene expression programming model were obtained from the test results. For gene expression programming model, mechanical properties (yield strength, ultimate tensile strength and elongation) before cold rolling, chemical composition, initial sheet thickness and reduction rate were used as independent input variables, while mechanical properties after cold rolling (yield strength, ultimate tensile strength and elongation) were used as dependent output variables. Before constructing the gene expression programming models for dependent variables, dataset was analyzed using the analysis of variance and statistically significant (P ≤ 0.1) independent parameters, i.e. initial sheet thickness, reduction rate, initial yield strength, initial tensile strength, elongation and Mn content were used in gene expression programming model. Different models were obtained for each dependent variable depending on the significant independent variables using the training dataset and accuracy of the best models was verified with testing data set. The predicted values were compared with experimental results and it was found that models are in good agreement with the experimentally obtained results.
15
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Evaluation of Rheological Behaviour upon Recycling of an Ethylene Vinyl Acetate Copolymer by Means of Twin-Screw Extrusion Process

70%
Fatih Ergin M., Aydin I.
Acta Physica Polonica A
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2017
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vol. 131
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issue 3
542-544
EN
Recycling of many polymers has gained a spectacular importance mainly because of its environmental and economical benefits. Ethylene vinyl acetate is one of the thermoplastics used directly as a final product and indirectly as an additive within many other polymeric materials. There has been limited research work on recycling of polymers even though recycling in industry has shown a spectacular growth in the last decade. It is the aim of this study to investigate and to evaluate the rheological behaviour of an ethylene-vinyl acetate copolymer resin upon recycling. For this purpose, original ethylene vinyl acetate granules were processed five cycles by using a twin-screw extruder and their rheological analysis was performed by means of an AR-G2 rheometer (TA Instruments), with a parallel-plate geometry, under a steady state condition. It was found that the rheological measurements of copolymer ethylene vinyl acetate exhibited a shear thinning constitutive behavior, obeying Carreau-Yasuda rheological constitutive model. The changes in flow and oscillatory shear measurements under different processing conditions were also determined in detail and results are reported in the paper.
16
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Dislocation Substructure Evolution during Hydrostatic Extrusion of Al-Mg-Si Alloy

70%
Chrominski W., Lewandowska M.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
585-588
EN
Hydrostatic extrusion is a technique which allows to produce rods with ultrafine grains and unexpectedly enhanced mechanical properties caused by grain refinement. However, the mechanism of such a refinement is not fully understood at this stage. 6xxx aluminium alloys series are usually processed by extrusion. In this study, commercial 6082 aluminium alloy was extruded at ambient temperature in a cooled die in two stages to the true strain of ε =3.2. Such a processing results in a not fully refined microstructure which allows to study different stages of grain refinement. The texture, dislocation substructures and grain refinement were investigated using electron backscatter diffraction and transmission electron microscopy techniques. The results revealed that two main texture components are present in the extruded rods - ⟨111⟩ fiber texture and ⟨001⟩ recrystallized grains. Transmission electron microscopy inspection revealed dislocation structures that can be associated with different stages of plastic deformation according to the low energy dislocation structures hypothesis proposed by Kuhlmann-Wilsdorf.
17
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Activation Energy for Grain Growth of the Isochronally Annealed Ultrafine Grained Magnesium Alloy after Hot Extrusion and Equal-Channel Angular Pressing (EX-ECAP)

70%
Stráská J., Stráský J., Janeček M.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
578-581
EN
Magnesium alloy AZ31 prepared by hot extrusion and 4 passes of equal-channel angular pressing (EX-ECAP) has ultra-fine grained microstructure with an average grain size of 900 nm. Grain growth is analysed using a general equation for the grain growth and an Arrhenius equation. The calculated value of the activation energy for grain growth differs with the annealing temperature. The fitted value of activation energy for grain growth in the intermediate temperature range (210-400°C) is in accordance with the results of other authors, but it is shown in this study that such value is abnormally low and physically meaningless. More real values of apparent activation energy in this temperature range were calculated from the model assuming a linear increase of activation energy with increasing annealing temperature. Result of this linear model of evolution of activation energy in the temperature range between 210-400°C is expressed by the interval estimation of apparent activation energy values. It is concluded that the evolution of apparent activation energy can be explained by a change in the mechanism underlying the grain boundary migration. In the low temperature range, the grain boundary diffusion is dominant since the material is ultra-fine grained, whereas at higher temperatures, the lattice self-diffusion is more important.
18
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Fabricating of Steel/Cast Iron Composite by Casting Route

70%
Ertürk S., Çakır O., Kumruoglu L., Ozel A.
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vol. 125
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issue 2
452-453
EN
In this study, 1.2333 cold work tool steel and cast iron (GG 25) were simultaneously melted in different furnaces to fabricate composite die mold used in sheet metal forming industry. To enhance the metallurgical bond between two components of composite part, the pouring temperature of cast iron was assessed just above the solidus temperature, then metallurgically prepared cast iron was poured on to the cast tool steel. The temperature and casting parameters were monitored and simulated. Experimental and simulation results were compared, finally the optimum parameters and casting route were revealed.
19
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FEA of Plastic Flow in AZ63 Alloy during ECAP Process

70%
Kocich R., Kursa M., Macháčková A.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
581-587
EN
Magnesium alloys based on Mg-Al-Zn system are very attractive materials in many industries due to their specific properties. One of common forming manners suitable for this kind of material is the application of severe plastic deformation method. This paper is focused on the deformation behavior of AZ63 alloy at equal channel angular pressing process in the temperature range of 250-320°C. For this purpose finite element analysis was used. Main attention was devoted to the influence of processing parameters on the material flow. Among other, changes of the flow during equal channel angular pressing in chosen regions of the pressed samples were monitored. As variables, temperature, friction coefficient, strain rate, φ-angle or back pressure application were chosen. The comparison of the material flow lines at different conditions shows the affecting of material flow. There are obvious considerable differences between regions adjacent to the inner radius and those adjacent to the outer radius. For example in the case μ = 0 the dead zone is delimited by the angle Ψp = 36°, while in the case of friction given by the coefficient μ = 0.04, the value of the angle was Ψp = 26.5°.
20
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Acoustic Emission Study of the Deformation Behavior of Mg-Mn Alloys Containing Rare Earth Elements

61%
Illkova K., Dobroň P., Chmelík F., Letzig D., Bohlen J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
634-638
EN
Magnesium-manganese (Mg-Mn) based alloys with various chemical composition were processed by indirect extrusion at two different speeds. Alloying with Mn and rare earth elements has significant influence on the microstructure and on the texture of the alloys under investigation. This paper deals with the acoustic emission analysis of the deformation behavior of the extruded Mg-Mn alloys. The acoustic emission measurements were performed during the uniaxial tension and compression tests, and the obtained results are discussed with respect to the influence of rare-earth elements on the deformation behavior, particularly in terms of the activation of dislocation glide and twinning.
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